An image compression apparatus includes a tile specifying section specifying rectangular tiles having an arbitrary size with respect to an image, an image dividing section dividing the image using the specified rectangular tiles, a bit-plane decomposing section decomposing each of the specified tiles dividing the image into bit-planes, a bit-plane ordering section ordering the bit-planes decomposing each of the specified tiles depending on a coding sequence, a layer forming section forming layers by the ordered bit-planes, and a suppressing section suppressing a quantization rate of a region low relative to other regions of the image.

This application claims the benefit of Japanese Patent Applications No. 2001-175081 filed Jun. 11, 2001 and No. 2001-178310 filed Jun. 13, 2001, in the Japanese Patent Office, the disclosure of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to image compression methods and apparatuses, image expansion methods and apparatuses, and storage media, and more particularly to an image compression method and apparatus, an image expansion method and apparatus, and a computer-readable storage medium which stores a program for causing a computer to carry out an image compression and/or an image expansion so as to suppress a quantization rate in a vicinity of a tile boundary.
2. Description of the Related Art
Due to improvements made in image input techniques and image output techniques, there are increased demands to improve the high definition property of color still images. One example of an image input apparatus is a digital camera (DC), and helped by reduced cost of high-performance charge coupled devices (CCDs) having 3,000,000 or more pixels, such high-performance CCDs are widely used for digital cameras in the popular price range. It is expected that products using CCDs having 5,000,000 or more pixels will be put on the market in the near future. Such high-performance input devices, typified by the CCDs, have been realized mainly due to improvements in silicon processes and device technologies, and have solved the tradeoff problem between miniaturizing the input device and suppressing signal-to-noise (S/N) ratio. This trend of increasing the number of pixels of the input device is expected to continue.
On the other hand, considerable improvements have also been made in image output devices and image display devices, such as hard-copy devices including laser printers, ink jet printers and thermal printers, and soft-copy devices including flat panel displays made of CRTs, liquid crystal displays (LCDs) and plasma display panels (PDPs). The high definition property of such image output devices and image display devices have improved considerably, and the cost has greatly been reduced.
Because of these high-performance and inexpensive image input devices and image output devices on the market, the use of high-definition still images have become popular. It is expected that the demands for high-definition still images will increase in the future in various fields. Actually, the developments in personal computers (PCs) and network-related technologies including the Internet have accelerated such trends. Especially in recent years, mobile equipments such as portable telephones and lap-top computers have become extremely popular, and there are more and more opportunities to transmit or receive high-definition images via a communication means. Consequently, it is expected that the demands to further improve the performance or function of the image compression and/or expansion techniques will increase so as to facilitate processing of the high-definition still images.
As one of image compression and expansion algorithms for facilitating the processing of such high-definition still images, the JPEG (Joint Photographic Experts Group) system is popularly used. In addition, the JPEG2000 which has become an international standard in 2001 uses an image compression and expansion algorithm with a high performance which is further improved compared to the JPEG. Hence, the JPEG2000 is extremely flexible and extendible with respect to various functions and various applications. Accordingly, there is much expectation on the JPEG2000 as a next-generation high-definition still image compression and expansion format which will succeed the JPEG.
FIG. 1 is a system block diagram for explaining the operating principle of the JPEG algorithm. The JPEG algorithm is realized by a color space transform and inverse transform section 40, a discrete cosine transform and inverse transform section 41, a quantization and inverse quantization section 42, and an entropy coding and decoding section 43. Normally, a non-independent-function is used in order to obtain a high compression rate, and the so-called lossless (or no-loss) compression and expansion will not be carried out. Although the original image data is not stored in their entirety, no problems will occur from the practical point of view. For this reason, the JPEG system can suppress the amount of memory capacity required to carry out the compression and expansion processes and to store the compressed image data. In addition, the JPEG system greatly contributes to reducing the time which is required for the data transmission and reception. Because of these advantages, the JPEG system is presently the most popularly used still image compression and expansion algorithm.
FIG. 2 is a system block diagram for explaining the operating principle of the JPEG2000 algorithm. The JPEG algorithm is realized by a color space transform and inverse transform section 50, a two-dimensional wavelet transform and inverse transform section 51, a quantization and inverse quantization section 52, an entropy coding and decoding section 53, and a tag processing section 54.
As described above, the JPEG system is the most popularly used still image compression and expansion system at the present. However, the demands to further improve the high definition properties of still images continue to increase, and the technical limits of the JPEG system are beginning to surface. For example, block noise and mosquito noise appearing in the image were not conspicuous in the past, but are gradually becoming more conspicuous as the high definition property of the original image improves. In other words, the image deterioration of the JPEG file which did not cause problems in the past are now becoming notable and no longer negligible from the practical point of view. As a result, image quality improvement at the low bit rate, that is, in the high compression rate region, is recognized as the most important problem to be solved for the algorithm. The JPEG2000 was developed as an algorithm capable of eliminating this problem, and it is expected that the JPEG2000 system will be used concurrently with the existing JPEG system.
When FIGS. 1 and 2 are compared, it may be seen that the transformation method is one of the largest differences between the JPEG and the JPEG2000. The JPEG system employs the discrete cosine transform (DCT), while the JPEG2000 system employs the discrete wavelet transform (DWT). Compared to the DCT, the DWT has an advantage in that the image quality is good in the high compression region, which is the main reason for employing the DWT in the JPEG2000 system.
Another large difference between the JPEG and the JPEG2000 is that the JPEG2000 additionally uses a functional block called the tag processing section 54 at the last stage for forming codes. The tag processing section 54 generates the compressed data as a code stream at the time of the compression operation, and interprets the code stream necessary for the expansion at the time of the expansion operation. The JPEG2000 can realize various convenient functions by the code stream. For example, FIG. 3 is a diagram showing an example of a subband at each decomposition level for a case where the decomposition level is 3. It is possible to freely stop the still image compression and expansion operation at an arbitrary level corresponding to the octave division in the DWT of the block base shown in FIG. 3.
At the original image input and output sections shown in FIGS. 1 and 2, the color space transform and inverse transform sections 40 and 50 are connected in most cases. For example, a transformation from the RGB colorimetric system made up of red (R), green (G) and blue (B) components of the primary color system or, from the YMC colorimetric system made up of yellow (Y), magenta (M) and cyan (C) components of the complementary color system, to the YUV or YCrCb colorimetric system or, an inverse transformation, is carried out in the color space transform and inverse transform sections 40 and 50.
Next, a description will be given of the JPEG2000 algorithm. The technical terms related to the JPEG2000 are in conformance with the JPEG2000 Final Draft International Standard (FDIS). Typical technical terms are defined as follows.    1. "Bit-Plane": A two-dimensional array of bits. In this Recommendation International Standard a bit-plane refers to all the bits of the same magnitude in all coefficients or samples. This could refer to a bit-plane in a component, tile-component, code-block, region of interest, or other.    2. "Code-Block": A rectangular grouping of coefficients from the same subband of a tile-component.    3. "Decomposition Level": A collection of wavelet subbands where each coefficient has the same spatial impact or span with respect to the source component samples. These include the HL, LH, and HH subbands of the same two-dimensional subband decomposition. For the last decomposition level the LL subband is also included.    4. "Layer": A collection of compressed image data from coding pass of one, or more, code-blocks of a tile-component. Layers have an order for encoding and decoding and decoding that must be preserved.    5. "Precinct": A one rectangular region of a transformed tile-component, within each resolution level, used for limiting the size of packets.
FIG. 4 is a diagram showing an example of each component of a color image divided into tiles. Generally, each of components 70, 71 and 72 (RGB primary color system in this case) of the original image is divided into rectangular regions (tiles) 70t, 71t and 72t in the color image as shown in FIG. 4. Each of the tiles, such as R00, R01, . . . , R15, G00, G01, . . . , G15, B00, B01, . . . , B15, becomes a basic unit for executing the compression and expansion process. Accordingly, the compression and expansion operation is independently carried out for every component and for every tile. At the time of the coding, the data of each tile of each component is input to the color space transform and inverse transform section 50 and subjected to a color space transform, and is thereafter subjected to a two-dimensional wavelet transform (forward transform) in the two-dimensional wavelet transform section 51 and spatially divided into frequency bands.
FIG. 3 described above shows the subband at each decomposition level for the case where the decomposition level is 3. In other words, the two-dimensional wavelet transform is carried out with respect to the tile original image (0LL) (decomposition level 0 (60)) obtained by the tile-division of the original image, so as to separate the subbands (1LL, 1HL, 1LH, 1HH) indicated by the decomposition level 1 (61). The two-dimensional wavelet transform is then carried out with respect to the low-frequency component 1LL at this level, so as to separate the subbands (2LL, 2HL, 2LH, 2HH) indicated by the decomposition level 2 (62). Similarly thereafter, the two-dimensional wavelet transform is also carried out with respect to the low-frequency component 2LL, so as to separate the subbands (3LL, 3HL, 3LH, 3HH) indicating the decomposition level 3 (63).
Furthermore, in FIG. 3, the color of the subband which is the target of the coding at each decomposition level is indicated by gray. For example, when the decomposition level is 3, the subbands (3HL, 3LH, 3HH, 2HL, 2LH, 2HH, 1HL, 1LH, 1HH) indicated by gray are the coding targets, and the 3LL subband is not coded.
Next, the bits which are the coding targets are determined in the specified coding order, and context is generated from the peripheral bits of the target bit in the quantization and inverse quantization section 52.
The wavelet coefficients after the quantization process ended are divided into non-overlapping rectangular regions called precincts, for each of the individual subbands. The precincts are introduced to efficiently utilize the memory upon implementation.
FIG. 5 is a diagram for explaining one example of the relationship of the precinct and the code block. An original image 80 is divided into 4 tiles 80t0, 80t1, 80t2 and 80t3 at the decomposition level 1. As shown in FIG. 5, a precinct 80p4, for example, is made up of 3 spatially matching rectangular regions, and the same holds true for a precinct 80p6. Furthermore, each precinct is divided into non-overlapping rectangular blocks called code blocks. In this particular example, each precinct is divided into 12 code blocks 0 to 11, and for example, a code block 80b1 indicates a code block number 1. The code block becomes a basic unit when carrying out the entropy coding.
The coefficients after the wavelet transform may be quantized and coded as they are. However, in order to improve the coding efficiency, the JPEG2000 decomposes the coefficient values into bit-plane units, and the bit-planes may be ordered for every pixel or code block.
FIG. 6 is a diagram for explaining the procedure for ordering the bit-planes. In the particular example shown in FIG. 6, an original image 90 (32×32 pixels) is divided into 4 tiles 90t0, 90t1, 90t2 and 90t3 each having 16×16 pixels. The sizes of the code block and the precinct at the decomposition level 1 respectively are 4×4 pixels and 8×8 pixels. The numbers of the precincts and the code blocks are assigned in a raster sequence. In this particular example, numbers 0 to 3 are assigned to the precincts, and numbers 0 to 3 are assigned to the code blocks. A mirroring method is used for the pixel expansion with respect to the outside of the tile boundary, and the wavelet transform is carried out by a independent-function (5, 3) integer transform filter to obtain the wavelet coefficients of the decomposition level 1.
In addition, FIG. 6 also generally shows the typical layer structure for the tile 90t0 (tile 0) precinct 90p3 (precinct 3) and the code block 90b3 (code block 3). A code block 90w3 after the transform is obtained by subjecting the code block 90b3 to the wavelet transform by the independent-function (5, 3) integer transform filter and obtaining the wavelet coefficient values of the decomposition level 1. The code block 90w3 after the transform is vided into the subbands (1LL, 1HL, 1LH, 1HH), and the wavelet coefficient values are allocated to each of the subbands.
The layer structure is easier to understand when the wavelet coefficient values are viewed from a horizontal direction (bit-plane direction). One layer is made up of an arbitrary number of bit-planes. In this example, each of the layers 0, 1, 2 and 3 is made up of 3 bit-planes 1, 3 and 1. The layer which includes a bit-plane closer to the LSB becomes the quantizing target earlier, and the layer including the bit-plane closer to the MSB becomes the quantizing target later and remains unquantized to the last. The method of discarding the layer closer to the LSB is called truncation, and the quantization rate can finely be controlled by this truncation.
In the entropy coding section 53 shown in FIG. 2, the coding with respect to the tiles of each of the components is carried out by probability estimation from the context and target bits. Hence, the coding process is carried out in units of tiles for all of the components of the original image.
Finally, the tag processing section 54 carries out a process of connecting all code data from the entropy coding section 53 into one code stream and adding a tag to this code stream. FIG. 7 is a simplified diagram showing an example of the code stream structure. As shown in FIG. 7, tag information called a header is added to the head of the code stream and to the head of the partial tile forming each tile. A main header 100 is added to the head of the code stream, and a tile-part header 101 is added to the head of the partial file. The coded data (bit stream 102) of each tile follows the tile-part header 101. An end tag 103 is also added to the end of the code stream.
On the other hand, at the time of the decoding, contrary to that at the time of the coding, the image data is generated from the code stream of each tile of each component, as will now be described briefly in conjunction with FIG. 2. In this case, the tag processing section 54 interprets the tag information added to the code stream which is input from the outside, decomposes the code stream into the code stream of each tile of each component, and carries out the decoding process for every code stream of each tile of each component. The position of the bit which is the target of the decoding is determined by the order based on the tag information within the code stream, and the quantization and inverse quantization section 52 generates the context from the arrangement of the peripheral bits (which have already been decoded) of the target bit position. The entropy coding and decoding section 53 carries out a decoding according to the probability estimation from the context and the code stream to generate the target bit, and the target bit is written at the target bit position.
The data decoded in this manner has been spatially divided for every frequency band. Hence, the decoded data is subjected to a two-dimensional wavelet inverse transform in the two-dimensional wavelet transform and inverse transform section 51, so as to restore each tile of each component of the image data. The restored data is transformed into the original colorimetric system data by the color space transform and inverse transform section 50.
In the case of the conventional JPEG compression and expansion system, the tile used in the JPEG2000 may be regarded as a square block having each side made up of 8 pixels and used for the two-dimensional discrete cosine transform.
The description given heretofore relates to the general still image. However, the technique described above may be extended to the moving (or dynamic) image. In other words, each frame of the moving image may be formed by one still image, and the still images may be displayed at an optimum frame rate for the application so as to obtain the moving image. Video data is obtained by coding the original still image or decoding compressed still image data, continuously, and thus, the compression and expansion operation is basically the same as that for the still image. Such an compression and expansion operation is sometimes also referred to as a motion still image compression and expansion process. This function of carrying out the motion still image compression and expansion process does not exist in the MPEG system video file which is presently used popularly for the moving image. Since this function of carrying out the motion still image compression and expansion process has an advantage in that high-quality still images can be edited in units of frames, there is much attention on this function for business use in broadcasting stations or the like. Hence, this function has the possibility of eventually being used by the general consumers.
The specification required of the motion still image compression and expansion algorithm but greatly differs from that required of the general still image compression and expansion algorithm is the processing speed (or rate). This is because the processing speed determines the frame rate which greatly affects the quality of the moving image. Because of the need to carry out the process in real-time, the method of realizing the motion still image compression and expansion algorithm is limited to methods having a high dependency on the hardware such as ASIC and DSP. Although it may eventually become possible in the future to realize a sufficiently high speed process by software, it seems necessary until then to wait for further progress in the fields such as semiconductor process and device techniques and software parallel compiler techniques.
However, according to the conventional techniques, there is a problem in that the tile boundary becomes conspicuous when the compression and expansion process is carried out under a high compression rate condition. The amount of data of the image becomes extremely large when the original image which is the target of the compression and expansion process is spatially large in area or includes large number of gradation levels for each of the color components. The concept of using tiles was developed to simultaneously cope with the demands to improve the high-definition still image described above and the technical problem of increasing amount of image data.
If the original image having an extremely large amount of data is processed as it is, an extremely large memory region is required to provide a working area for processing the image data and to provide an area for holding the processed result. In addition, the processing time required for the compression or expansion becomes extremely long. In order to avoid such problems, the original image is divided into units called tiles (blocks in the case of the JPEG) which are rectangular regions, and the compression and expansion process is normally carried out for each of such regions. By employing this concept of spatially dividing the original image into tiles, it has become possible to suppress the increase in the required memory capacity and processing time to a practical level.
However, the division of the original image into tiles has introduced a new problem, namely, the conspicuous tile boundary described above. This phenomenon of conspicuous tile boundary occurs when the compressed image data which is generated under a high compression rate condition by nonreversibly compressing (lossy encoding) the original image is expanded (decoded) back to the original image. Particularly when displaying a high-definition still image having a large area or moving image frequently using a high compression rate, the conspicuous tile boundary subjectively causes considerable effects even if the image quality within the tile is maintained satisfactory. Hence, this conspicuous tile boundary may cause serious consequences in the future with respect to one advantage of the JPEG2000, that is, the reduced image quality deterioration under the high compression rate.
FIG. 8 is a diagram showing an example of an image which is obtained by compressing the original image to 1/75  by a lossless (no-loss) compression and thereafter expanding the compressed image. FIG. 9 is a diagram showing an example of an error image between the original image and the image after expansion. In FIGS. 8 and 9, portions indicated by arrows 110a and 111a correspond to boundaries of the mutually adjacent tiles. It may be seen that a conspicuous discontinues line exists at these portions 110a and 111a.
When the image is compressed at a high compression rate and then expanded, it may be regarded that the two-dimensional wavelet transform process causes the conspicuous tile boundary. In other words, when the lowpass filter and highpass filter in the horizontal direction and the lowpass filter and highpass filter in the vertical direction carry out the respective filtering operations, the region which is the target of the operations extends outside the tile where the image data does not exist. The rate at which the operation target region extends outside the tile increases as the decomposition level increases.
According to the JPEG2000 format, various filters such as the non-independent-function (9, 7) floating point transform filter and the independent-function (5, 3) integer transform filter are recommended for use as the wavelet filter. For the sake of convenience, the detailed operation of the wavelet transform and the reason why the tile boundary appears will now be described for a case where the independent-function (5, 3) integer transform filter is used as the wavelet filter.
FIG. 10 is a diagram showing a pixel expansion using the mirroring method. As shown in FIG. 10, a case will be considered where characters "RICOH" are arranged in one row of a target tile 112. It is assumed that each character corresponds to the value of 1 pixel, and the first character "R" is the kth pixel and the last character "H" is the mth pixel. When carrying out the wavelet transform with respect to this tile 112, several pixels before the kth pixel and several pixels after the mth pixel become necessary. Hence, it is necessary to extend the pixels outside a tile boundary 112a according to the mirroring method, as shown in FIG. 10. Expanded pixels are denoted by a reference numeral 113.
In the (5, 3) independent-function wavelet filter, the values of the odd numbered pixels and the wavelet coefficient values of the even numbered pixels are respectively calculated according to formulas (1) and (2), where C(2i+1), C(2i), . . . are wavelet coefficient values and P(2i+1), P(2i), . . . are pixel values.C(2i+1)=P(2i+1)−|_(P(2i)+P(2i+2))/2_| for k−1≦2k+1<m+1  (1)C(2i)=O(2i)+|_(C(2I−1)+C(2I+1)+2)/4_| for k≦2I<m+1  (2)
FIGS. 11A through 11G are diagrams showing pixel values and wavelet coefficient values when the decomposition level is 1, for the case where a lossless (no-loss) (5, 3) independent-function wavelet transform is carried out with respect to a square tile made up of 16×16 pixels. In FIG. 11A, the numerals arranged outside the tile indicate the pixel values extended by the mirroring method.
A vertical direction highpass filter operation shown in FIG. 11B and a vertical direction lowpass filter operation shown in FIG. 11C are carried out with respect to the tile having the pixel values shown in FIG. 11A. Next, a horizontal direction lowpass filter operation and a horizontal direction highpass filter operation are carried out with respect to the result of the vertical direction lowpass filter operation shown in FIG. 11C, so as to obtain the LL component shown in FIG. 11D and the HL component shown in FIG. 11E of the wavelet coefficients at the decomposition level 1. On the other hand, a horizontal direction lowpass filter operation and a horizontal direction highpass filter operation are carried out with respect to the result of the vertical direction highpass filter operation shown in FIG. 11B, so as to obtain the LH component shown in FIG. 11F and the HH component shown in FIG. 11G of the wavelet coefficients at the decomposition level 1.
FIGS. 12A through 12C are diagrams showing examples of pixel values of a square tile made up of 16×16 pixels which is obtained by carrying out an inverse transform from the wavelet coefficients derived in FIGS. 11A through 11G.
FIG. 12A shows the coefficient values of each of the subbands of the decomposition level 1, which are obtained by the forward wavelet transform described above in conjunction with FIGS. 11A through 11G, and are rearranged by interleaving.
FIG. 12B shows the result which is obtained by carrying out the horizontal direction inverse transform filter operation on the odd number pixels, followed by the horizontal direction inverse transform filter operation on the even numbered pixels, with respect to the coefficient values shown in FIG. 12A, and FIG. 12C shows the result which is obtained by carrying out the vertical direction inverse transform filter operation on the even number pixels, followed by the vertical direction inverse transform filter operation on the odd numbered pixels.
FIG. 13 is a diagram showing an example of the comparison result which is obtained by comparing the pixel values of the original image shown in FIG. 11A and the pixel values which are obtained by carrying out the lossless transform and inverse transform by the pixel expansion according to the mirroring method shown in FIG. 12C. In the case shown in FIG. 13, the error is indicated by a difference between the individual pixels. It may be seen from FIG. 13 that, the pixel values after the compression and expansion process perfectly match the pixel values of the original image, for all of the tiles.
FIGS. 14A through 14G are diagrams showing pixel values and wavelet coefficient values when the decomposition level is 1, for the case where a lossy (5, 3) independent-function wavelet transform is carried out with respect to a square tile made up of 16×16 pixels. In FIG. 14A, the numerals arranged outside the tile indicate the pixel values extended by the mirroring method. However, in order to facilitate comparison with FIG. 11A, FIG. 14A shows the result of the quantization and inverse quantization.
A vertical direction highpass filter operation shown in FIG. 14B and a vertical direction lowpass filter operation shown in FIG. 14C are carried out with respect to the tile having the pixel values shown in FIG. 14A. Next, a horizontal direction lowpass filter operation and a horizontal direction highpass filter operation are carried out with respect to the result of the vertical direction lowpass filter operation shown in FIG. 14C, so as to obtain the LL component shown in FIG. 14D and the HL component shown in FIG. 14E of the wavelet coefficients at the decomposition level 1. On the other hand, a horizontal direction lowpass filter operation and a horizontal direction highpass filter operation are carried out with respect to the result of the vertical direction highpass filter operation shown in FIG. 14B, so as to obtain the LH component shown in FIG. 14F and the HH component shown in FIG. 14G of the wavelet coefficients at the decomposition level 1. In this particular example, the quantization step size is 4 (LL component)/32 (HL & HH components)/64 (HH component). The wavelet coefficient values after the quantization are obtained by adding the original positive or negative sign to the floor function of the value obtained by dividing the coefficient of each subband by the quantization step size.
FIGS. 15A through 15C are diagrams showing examples of pixel values of a square tile made up of 16×16 pixels which is obtained by carrying out an inverse transform from the wavelet coefficients after the quantization and inverse quantization and are derived in FIGS. 14A through 14G. The forward and reverse wavelet transforms are similar to those for the lossless independent-function wavelet transform, and a detailed description thereof will be omitted.
FIG. 16 is a diagram showing an example of the comparison result which is obtained by comparing the pixel values of the original image shown in FIG. 14A and the pixel values which are obtained by carrying out the lossy transform and inverse transform by the pixel expansion according to the mirroring method shown in FIG. 15C. In this example, unlike the case where the lossless transform and inverse transform (quantization step size 1) are carried out, errors are generated. Large errors are seen particularly near the tile boundary. This is the cause of the tile boundary becoming visually conspicuous at the low bit rate.
Conventionally, in order to eliminate the problems described above, a proposal has been made to use the image data of the adjacent tiles, that is, to mutually overlap the boundaries of the adjacent tiles (although the adjacent tile boundaries should not overlap according to the baseline system of the JPEG2000). In addition, the tile boundary which becomes visually conspicuous as a result is subjected to a so-called post-filtering process or the like by employing completely different image processing algorithms for each to make the tile boundary less conspicuous.

Image compression method and apparatus for suppressing quantization rate in particular region, image expansion method and apparatus therefor, and computer-readable storage medium storing program for the compression or expansion


A method of removing gas from a printhead is provided. A sealing material may be applied to orifices of a printhead from external the printhead to restrict passage of fluid through the orifices. Ink may be moved through a printhead conduit disposed in fluid communication with the orifices to create an inward suction adjacent the orifices so that the gas is displaced from adjacent the orifices.

Printers may create printed output on a print medium by firing ink droplets at the print medium from nozzles of a printhead. To prepare the nozzles for firing initially, the nozzles are primed with ink, to replace gas with ink. The nozzles and their supply compartments then should be maintained relatively free of gas bubbles to maintain consistent firing of the nozzles.

Hewlett-Packard Development Company, L.P.


The invention is based on the discovery that a remarkable improvement in the performance of maleimide thermosets can be achieved by incorporating amide-extended maleimides into an adhesive formulation. Amide-extended maleimides described herein can be used to toughen bismaleimide thermosetting materials without sacrificing any thermal stability. Amide-extended maleimides are readily prepared by reacting a bismaleimide with an appropriate amine via the well-known Michael addition reaction. Acylation of the resulting secondary amines provides the amide-extended maleimide. The acylating agent can also be used to introduce polymerizable functional groups into the backbones of these thermoset monomers. Amide-extended acrylate and methacrylate monomers can also be prepared.

Adhesive compositions, particularly conductive adhesives, are used for a variety of purposes in the fabrication and assembly of semiconductor packages and microelectronic devices. The more prominent uses include bonding of electronic elements such as integrated circuit chips to lead frames or other substrates, and bonding of circuit packages or assemblies to printed wire boards. Adhesives useful for electronic packaging applications typically exhibit properties such as good mechanical strength, curing properties that do not affect the component or the carrier, and thixotropic properties compatible with application to microelectronic and semiconductor components.
A few methods have been described in the art to decrease the brittleness of bismaleimide thermosets. The well-known Michael addition reaction, using aromatic or aliphatic diamines is one of these methods. Michael addition has been used to reduce the cross-link density and therefore to improve the toughness of these thermosets. The Michael addition approach to toughen BMI resins, however, has at least one significant limitation. Michael addition is thermally reversible and the amine extended bismaleimides will revert to the starting materials in the vicinity of 300° C. This thermal reversion or retro-Michael addition is unacceptable for any adhesive end-use that requires thermal resistance.
The bismaleimides represent one useful class of thermoset compounds that have been used in the microelectronic packaging industry. Bismaleimides are curable, meaning that they are capable of polymerization to yield cross-linked resins. In addition, bismaleimides may be homocured in the presence of free radicals or photoinitiators, or combined with other free-radical curing monomers (e.g., acrylates, methacrylates, syrenics, vinyl ethers, vinyl esters, allyl monomers, olefins, and the like). They may also be cured in the presence of comonomers via, Diels-Alder, -ene, and Michael addition mechanisms.
Commercially available bismaleimide thermoset compositions are noted for their high modulus, and excellent resistance to thermal degradation. However, these thermoset compositions are also well known for brittleness. The utility of the bismaleimide class of thermosets could be vastly improved if less brittle formulations could be achieved that retain the desirable thermal and elastic properties.
A few methods have been described in the art to decrease the brittleness of bismaleimide thermosets. The well-known Michael addition reaction, using aromatic or aliphatic diamines is one of these methods. Michael addition has been used to reduce the cross-link density and therefore to improve the toughness of these thermosets. The Michael addition approach to toughen BMI resins, however, has at least one significant limitation. Michael addition is thermally reversible and the amine extended bismaleimides will revert to the starting materials in the vicinity of 300° C. This thermal reversion or retro-Michael addition is unacceptable for any adhesive end-use that requires thermal resistance.
The imide-extended polymaleimides of this invention are contemplated for use in a wide variety of applications. They can be used, for example, as matrix resins and adhesives for aerospace, marine, automotive, wind turbine, and sports equipment composite products. They can be used in the fabrication of printed wiring boards and flexible circuits. The compounds of this invention can be used in die attach adhesives, underfill and mold compound resins for electronic packaging. They can be used to make thermally resistant films and film adhesives. They may also be used in the fabrication of anisotropic conductive adhesive films and pastes.

This patent is subject to a terminal disclaimer.

Amide-extended crosslinking compounds and methods for use thereof


A control system for a rear-mounted work implement on a work machine operable from a forward-facing operator's station located on the work machine is disclosed. The control system includes a surface adjacent to the operator's station, the surface being fixed in a position. A control device is attached to the surface and includes a grip configured to be gripped by an operator. A position of the grip is fixed relative to the surface during use, and the grip is positioned to stabilize an operator when turned in the operator's station to view the work implement. The control device also includes a switching mechanism disposed between the grip and the surface, and being configured to operate the work implement and configured to be actuatable by a hand on the grip.

Work machines, such as motor graders, are often equipped with a rear-mounted work implement, such as a ripper device. The ripper device is meant to be controlled while driving the work machine forward. Because of this, the operator must look out of the rear cab window to observe the work implement while he drives. Traditional controllers for the rear-mounted work implement are mounted along a front of the operator's cab and may include a lever having a knob connected to a rod extending from the control panel. The rod typically connects to a mechanical linkage extending from the control panel to the rear of the work machine for operation of the work implement.
During use, the operator may observe the rear-mounted work implement by looking over his shoulder, while at the same time reaching forward with one or both arms to adjust the work implement by operating the control lever. Doing this can be uncomfortable for the operator and, if done for extended periods, can cause fatigue. In addition, while the operator is looking out the back window toward the rear-mounted work implement, any bumps encountered by the motor grader may cause the operator's arm to jog, and may inadvertently move the control lever.
One system for controlling a work implement is disclosed in U.S. Pat. No. 5,768,947 to Fee et al. The '947 patent discloses a work implement hand support for a bulldozer. The hand support extends in a forward direction from a base and end portion. At a distal end of the hand support, a thumb-operated lever is configured to operate the work implement. Although the hand-support is effective and functional, there is a need for a hand-support that can be grasped from the rearward direction to provide additional comfort to an operator.
The control device described herein overcomes one or more of the deficiencies in the prior art.

Rear-mounted work implement control system


Novel derivatives of benzofuran and dihydrobenzofuran are provided which are useful as melatonergic agents.

The invention pertains to novel substituted benzodioxoles, benzofurans, dihydrobenzofurans, benzodioxanes and related derivatives having drug and bio-affecting properties and to their preparation, pharmaceutical formulations and use. In particular, the invention concerns benzodioxoles, benzofurans, dihydrobenzofurans and related derivatives bearing substituted amino methyl cyclopropyl groups. These compounds possess melatonergic properties that should make them useful in treating certain medical disorders.
Melatonin (N-acetyl-5-methoxytryptamine) is a hormone which is synthesized and secreted primarily by the pineal gland. Melatonin levels show a cyclical, circadian pattern with highest levels occurring during the dark period of a circadian light-dark cycle. Melatonin is involved in the transduction of photoperiodic information and appears to modulate a variety of neural and endocrine functions in vertebrates, including the regulation of reproduction, body weight and metabolism in photoperiodic mammals, the control of circadian rhythms and the modulation of retinal physiology. ##STR1##
Recent evidence demonstrates that melatonin exerts its biological effects through specific receptors. Use of the biologically active, radiolabelled agonist .sup.125 I!-2-iodomelatonin has led to the identification of high affinity melatonin receptors in the CNS of a variety of species. The sequences of two cloned human melatonin receptors have been reported Reppert, et al., Proc. Natl. Acad. Sci. 92, p. 8734-8738, (1995) and Reppert, et al., Neuron 13, p. 1177-1185, (1994)!. In mammalian brain, autoradiographic studies have localized the distribution of melatonin receptors to a few specific structures. Although there are significant differences in melatonin receptor distribution even between closely related species, in general the highest binding site density occurs in discreet nuclei of the hypothalamus. In humans, specific .sup.125 I!-2-iodomelatonin binding within the hypothalamus is completely localized to the suprachiasmatic nucleus, strongly suggesting the melatonin receptors are located within the human biological clock.
Exogenous melatonin administration has been found to synchronize circadian rhythms in rats (Cassone, et al., J. Biol. Rhythms, 1:219-229, 1986). In humans, administration of melatonin has been used to treat jet-lag related sleep disturbances, considered to be caused by desynchronization of circadian rhythms (Arendt, et al., Br. Med. J. 292:1170, 1986). Further, the use of a single dose of melatonin to induce sleep in humans has been claimed by Wurtman in International Patent Application WO 94/07487, published on Apr. 14, 1994.
Thus, melatonin agonists should be particularly useful for the treatment of sleep disorders and other chronobiological disorders. Melatonin agonists would also be useful for the further study of melatonin receptor interactions as well as in the treatment of conditions affected by melatonin activity, such as depression, jet-lag, work-shift syndrome, sleep disorders, glaucoma, reproduction, cancer, premenstrual syndrome, immune disorders, inflammatory articular diseases and neuroendocrine disorders.
Aside from simple indole derivatives of melatonin itself, various bicyclic structures have been prepared and their use as melatonin ligands disclosed. In general these bicyclic amide structures can be represented as: ##STR2## wherein Z is an aryl or heteroaryl system attached by a two carbon bridge to the amide group. Some specific examples follow.
Yous, et al. in European Patent Application EP-527,687A, published on Feb. 17, 1993, disclose as melatonin ligands arylethylamines i, ##STR3## wherein Ar' is, inter alia, a substituted or unsubstituted benzob!thiophen-3-yl, benzimidazol-1-yl, benzob!furan-3-yl, 1,2-benzisoxazol-3-yl, 1, 2-benzisothiazol-3-yl, or indazol-3-yl radical; R.sub.1 is, inter alia, an alkyl or cycloalkyl group; and R.sub.2 is hydrogen or lower alkyl.
Yous, et al. in European Patent Application EP-506,539A, published on Sep. 30, 1992, claim ligands ii, ##STR4## wherein A is oxygen or sulfur; X is a methylene group or a bond; and R is H or lower alkyl when p is 1 and B is defined by the radical iii, ##STR5## wherein R.sub.1 is hydrogen or lower alkyl and R.sub.2 is, inter alia, hydrogen, lower alkyl or cycloalkyl. Alternatively, R is defined by the radical iii when p is 0 or 1 and B is lower alkoxy.
Several naphthalene derivatives have also been disclosed as melatonin ligands.
Andrieux, et al. in European Patent Application EP-447,285A, published on Sep. 18, 1991, claim amidoalkylnaphthalenes iv, ##STR6## wherein R is lower alkyl; R.sub.1 is hydrogen or lower alkyl; and R.sub.2 is, inter alia, hydrogen, lower alkyl, or cycloalkyl.
Yous, et al. in European Patent Application EP-562,956A, published on Sep. 29, 1993, disclose amide and urea naphthalene derivatives v, ##STR7## in which R is hydrogen or OR.sub.4 wherein R.sub.4 is, inter alia, hydrogen, alkyl, cycloalkyl, or cycloalkylalkyl; R.sub.1 is hydrogen or COOR.sub.5 wherein R.sub.5 is hydrogen or alkyl; R.sub.2 is hydrogen or alkyl; X is NH or a bond; and R.sub.3 is, inter alia, alkyl, alkenyl, or cycloalkyl.
Lesieur, et al. in European Patent Application EP-530,087A, published on Mar. 3, 1993, disclose naphthylethylureas and naphthylethylthioureas vi, ##STR8## in which R is hydrogen or OR.sub.3 wherein R.sub.3 is, inter alia, hydrogen, lower alkyl, or cycloalkyl; R.sub.1 is hydrogen or lower alkyl; X is oxygen or sulfur; and R.sub.2 is, inter alia, lower alkyl or cycloalkyl.
Langlois, et al., in Australian Patent Application AU-A-48729/93 disclose arylalkyl(thio)amides vii as melatonergic ligands, ##STR9## wherein R.sub.1 is hydrogen or lower alkyl; R.sub.2 is hydrogen, halogen, or lower alkyl; R.sub.3 and R.sub.4 are identical or different groups including, inter alia, hydrogen, halogen, or lower alkyl or R.sub.3 and R.sub.4, together with the benzene ring which carries them, form a ring-system E.sub.3 chosen from, inter alia, naphthalene, on the understanding that the portion of the ring-system E.sub.3 formed by R.sub.3 and R.sub.4 and the two carbon atoms of the benzene ring which carry them is unhydrogenated or partially hydrogenated; R.sub.5 is hydrogen or lower alkyl; and R.sub.6 is, ##STR10## wherein X is sulfur or oxygen and R.sub.7 is, inter alia, lower alkyl or alkenyl. Compound viii is included as a specific example, ##STR11##
Horn and Dubocovich in European Patent Application EP-420,064A, published on Apr. 3, 1991, disclose 2-amidotetralins ix as melatonin ligands, ##STR12## wherein R.sub.1 is, inter alia, hydrogen, lower alkyl, or lower alkoxyl; R.sub.2 is, inter alia, hydrogen, halogen, or lower alkoxyl; R.sub.3 is, inter alia, hydrogen, or lower alkyl; R.sub.4 is, inter alia, lower alkyl, haloalkyl or cycloalkyl; and R.sub.5 is hydrogen, hydroxyl, halogen, oxo, aryl, lower alkyl or alkylaryl.
Copinga et al, in J. Med. Chem., 36, p. 2891-2898 (1993), discusses amidomethoxytetralins of structure x and their melatonergic properties. ##STR13## In structure x, R.sub.1 is H or OCH.sub.3 and R.sub.2 is alkyl, haloalkyl, phenylalkyl or phenyl.
Lesieur et al, in EP-708,099A, published Apr. 24, 1996, disclose compounds of structure xi, which are useful for the treatment of diseases caused by a melatonin imbalance. ##STR14## wherein ------ is a single or double bond; R.sub.1 =Me or MeNH; and X-Y =--CH(Me)--CH.sub.2 --, CH.sub.2 CH(OH)--or (CH.sub.2).sub.3 --.
North et al., in International Application WO 95/29173, published Nov. 2, 1995, disclose naphthalene derivatives of structure xii: ##STR15## wherein R.sub.1 is a group of the formula CR.sub.3 R.sub.4 (CH.sub.2).sub.p NR.sub.5 COR.sub.6 ; R.sub.2 is hydrogen, halogen, C.sub.1-6 alkyl, OR.sub.7 or CO.sub.2 R.sub.7 ; and may be the same or different substituent when q is 2; R.sub.3, R.sub.4 and R.sub.5, which may be the same or different, are hydrogen or C.sub.1-6 alkyl; R.sub.6 is C.sub.1-6 alkyl or C.sub.3-7 cycloalkyl; R.sub.7 is hydrogen or C.sub.1-6 alkyl; n is zero, 1 or 2; p is an integer of 1, 2, 3 or 4; q is 1 or 2; and the dotted lines indicate the absence or presence of an additional bond. The North et al. compounds are taught to treat chronobiological disorders.
In International Application WO 95/17405, published on Jun. 29, 1995, North et al., disclose compounds of structure xiii and teach their use in the treatment of conditions related to the melatonin system. ##STR16## wherein R.sub.1 is hydrogen, halogen or C.sub.1-6 alkyl; R.sub.2 is a group of formula --CR.sub.3 R.sub.4 (CH.sub.2).sub.p NR.sub.5 COR.sub.6 ; R.sub.3, R.sub.4 and R.sub.5, which may be the same or different, are hydrogen or C.sub.1-6 alkyl; R.sub.6 is C.sub.1-6 alkyl or C.sub.3-7 cycloalkyl; n is an integer of 2, 3 or 4; and p is an integer of 1, 2, 3 or 4.
The foregoing disclosures do not teach or suggest the novel melatonergic benzodioxole, benzofuran or dihydrobenzofurans of the present invention. The novel compounds of the present invention display melatonergic agonist activity.

Benzofuran and dihydrobenzofuran melatonergic agents


Coating methods and a coated substrate are provided. The coating method includes providing a component having an aperture formed in a surface thereof, arranging and disposing a hollow member on a portion of the surface to define a hollow space above the aperture corresponding to a shape of the aperture at the surface, applying at least one coating over the surface of the component and the hollow member to form an applied coating having an applied coating thickness, and removing at least a portion of the hollow member to expose the hollow space through the applied coating. The coated substrate includes a component having an aperture formed in a surface thereof, a hollow member arranged and disposed on the surface to define a hollow space above the aperture, and an applied coating over the surface of the component, the hollow space being exposed through the applied coating.

When turbines are used on aircraft or for power generation, they are typically run at a temperature as high as possible, for increased operating efficiency. Since high temperatures can damage the alloys used for the components, a variety of approaches have been used to raise the operating temperature of the metal components. One approach calls for the incorporation of internal cooling channels in the component, through which cool air is forced during engine operation. The cooling holes can be formed in the substrate by techniques such as water jet processing and/or electrical discharge machining (EDM). Cooling air (usually provided by the engine's compressor) is fed through the holes from the cooler side to the hot side of the combustor wall. As long as the holes remain clear, the rushing air will assist in lowering the temperature of the hot metal surface and preventing melting or other degradation of the component.
Another technique for protecting the metal parts and effectively raising the practical operating temperature of an aircraft engine involves the use of a thermal barrier coating (TBC). The TBC is usually ceramic-based. TBC systems frequently also include a bond coat which is placed between the ceramic coating and the substrate to improve adhesion. The use of TBC's in conjunction with the battery of cooling holes is sometimes the most effective means for protecting an engine part. However, incorporation of both systems can be very difficult. For example, the cooling holes sometimes cannot be formed in the engine part after a TBC has been applied, since lasers usually cannot effectively penetrate both the ceramic material and the metal to form the pattern of holes. If the cooling holes are formed prior to the application of the TBC system, they may become covered and at least partially obstructed when the bond coat and/or TBC is applied. Additionally, repair of the metal parts often includes replacing the TBC, during which the existing cooling holes may become covered and at least partially obstructed. Complete removal of the ceramic-metal material from the holes can be very time-consuming and ineffective. Any obstruction of the holes during engine operation can interfere with the passage of cooling air, can waste compressor power, and can possibly lead to engine component damage due to overheating.
Therefore methods of coating a component and methods of forming apertures or holes in coated components that do not suffer from the above drawbacks are desirable in the art.


The present invention relates to methods, devices, and coatings, wherein active agent release is determined by deposition rate of a coating or material. In an embodiment, the invention includes a method for coating a medical device, including identifying active agent elution rates for a coating composition applied to substrates at a plurality of coating deposition rates, selecting one of the coating deposition rates, and applying the coating composition to the medical device at the selected deposition rate. In an embodiment, the invention includes a combination including a medical device and a composition for coating the surface of a medical device with an active agent in a manner that permits the coated surface to release the active agent over time when implanted in vivo.

Therapeutic benefits can be achieved in some instances by providing an active agent to a subject in a manner that extends the time over which the active agent is released. Further, therapeutic benefits can be achieved by providing an active agent to a specific target tissue, instead of systemically. This is because the effect of the agent on the target tissue can be maximized while limiting side effects on other tissues. One approach to providing these benefits is to use a coating system containing an active agent on a medical device.
The specific rate at which an active agent is eluted from a coating or material is of importance. If the active agent elutes too quickly, there may be too much of an active agent that is dosed to a particular tissue. Over-dosing of an active agent may have harmful side effects. If the active agent elutes too slowly, there may be too little of an active agent that is dosed to a particular tissue. Under-dosing of an active agent may fail to yield a therapeutic effect.
A desirable elution rate for one active agent may be different than a desirable elution rate for another active agent. Further, a desirable elution rate for a particular active agent may vary with the particular type of condition being treated.
Therefore, a need exists for coatings, coating systems, and coating methods that achieve a predetermined rate of elution of an active agent from a coating or material.

Methods, devices, and coatings for controlled active agent release


A method of preparing a layout for manufacturing an integrated circuit chip according to a circuit design, the method includes generating a pattern for the layout based on the circuit design, determining, by a processor, if at least one layout rule is violated by including the generated pattern in the layout and modifying the layout if the at least one layout rule is violated. The at least one layout rule includes a constraint on a relationship between a power line pattern and a device pattern in the layout. The at least one layout rule is specified by comparing a predetermined threshold value with one of an estimated voltage drop along a signal path in a second layout different than the layout or an estimated current density on the signal path in the second layout. The constraint includes a minimum number of contacts per device or power vias per device.

Since the invention of integrated circuits (ICs), the semiconductor industry has experienced continual rapid growth due to continuous improvements in the integration density of various components (e.g. transistors, diodes, resistors, capacitors, etc.). A significant part of the improvement in integration density comes from repeated reductions in minimum feature size that allow the integration of more components into a given area.
Meanwhile, as semiconductor device features are reduced further, the impacts caused by current-resistance voltage drop (IR drop) effects and electro-migration (EM) effects increase. The IR drop effects refer to the voltage drops along electrical paths resulting from the currents carried by the electrical paths and the resistances of the electrical paths. The EM effects refer to the mass transport of metal due to the momentum transfer between conducting electrons and diffusing metal atoms. The IR drop effects and the EM effects make the performance of an IC deteriorate or even fail.

Method of preparing a layout and system for performing the same

TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY, LTD.


A musical instrument laser tracking device comprises a musical instrument digital interface adapted to be connected to a musical instrument digital interface port of a musical instrument. A computer system electronically connected to the musical instrument digital interface and incorporating software adapted to produce electronic signals to control a laser projector. A digital-to-analog converter electronically connected to the computer system and adapted to convert the electronic signals from a digital format to an analog format, and a laser projector electronically connected to the digital-to-analog converter and adapted to receive the electronic analog signals from the digital-to-analog converter, generate laser beams accordingly, and shine the laser beams on predetermined objects in predetermined patterns.

There currently exist laser shows and music shows which combine lights and lasers synchronized to music to enhance the experience of the audience. Besides an auditory experience, they add a visual aspect that thrills the audience. In a music show or the opening and closing ceremonies of the Olympics for example. In a live music show we have lights and lasers linked to the overall music and/or the beat or drums but none that links the audience to any particular instrument player as they play each individual note or beat. Similarly when a musician is practicing alone and would like an enhanced visual effect to every note that is played, there currently exists no such solution. There currently exists a need for a device that enhances the experience of both a single live instrument player alone and together with an audience

Musical instrument laser tracking device


A memory is disclosed. A memory cell comprises three gate structures sequentially arrayed between a first source-drain region and a second source-drain region. A first gate structure and a third gate structure are formed by superposition of a first gate dielectric layer, a floating gate, a second gate dielectric layer and a polysilicon control gate, so that two memory bits and two control gates are formed. A second gate structure is located between the first gate structure and the third gate structure and serves as a select gate. Erasing and programming operations on the two memory bits formed by the floating gates are realized by FN tunneling. During erasing and programming, the first source-drain region and the second source-drain region are grounded, so that the memory bits can be selected and then erased or programmed only by controlling voltages of the first control gate, the select gate and the second control gate. An operation method of a memory is further disclosed. The two memory bits of the memory cell can be independently operated, so that operations on single memory bits are achieved, and accordingly, storage-computation integrated operations are realized.

FIG. 1 is a structural view of a memory cell of an existing memory. As shown in FIG. 1, the memory cell 1 comprises a first gate structure 104, a second gate structure 105, a third gate structure 106, a first source-drain region 102 and a second source-drain region 103.
The first gate structure 104 is formed by superposition of a first gate dielectric layer 107, a floating gate (FG) 108, a second gate dielectric layer 109 and a polysilicon control gate 110 which are formed on a surface of a semiconductor substrate 101. The first source-drain region 102 and the second source-drain region 103 are usually N+ doped. The semiconductor substrate 101 is a P-typed doped silicon substrate.
The second gate structure 105 consists of a third gate dielectric layer 111 and a polysilicon gate 112 which are formed on the surface of the semiconductor substrate 101.
The third gate structure 106 is formed by superposition of a first gate dielectric layer 107, a floating gate 108, a second gate dielectric layer 109 and a polysilicon control gate 110 which are formed on the surface of the semiconductor substrate 101.
A channel region is formed by a part, located between the first source-drain region 102 and the second source-drain region 103, of the semiconductor substrate 101.
The first gate structure 104, the second gate structure 105 and the third gate structure 106 are arrayed on a surface of the channel region located between the first source-drain region 102 and the second source-drain region 103. Formation of a channel on the surface of the channel region is controlled by the first gate structure 104, the second gate structure 105 and the third gate structure 106.
The polysilicon control gate 110 of the first gate structure 104 serves as a first control gate CCG0 of the memory cell 1, the polysilicon gate 112 of the second gate structure 105 serves as a select gate CWL of the memory cell 1, and the polysilicon control gate 110 of the third gate structure 106 serves as a second control gate CCG1 of the memory cell 1.
The floating gate 108 of the first gate structure 104 serves as a first memory bit, and the floating gate 108 of the third gate structure 106 serves as a second memory bit.
The first source-drain region 102 is connected to a source S, and the second source-drain region 103 is connected to a drain D.
The memory bits of the existing memory are generally programmed by source-side hot electron injection (SSI). As an example, programming of the second memory bit is described as follows:
Programming Voltages:
The voltage of the select gate CWL is set as 1.4V, so that a channel is formed at the bottom of the second gate structure 105;
The voltage of the first control gate CCG0 is set as 5V, so that a channel is formed at the bottom of the first gate structure 104;
A programming current such as 2 μA is supplied to the source S;
A 5.5V voltage is applied to the drain D, and a 8V voltage is applied to the third control gate CCG1, so that a large depletion region is formed at the bottom of the third gate structure 106. Electrons from the source S flow into the depletion region at the bottom of the third gate structure 106 via the channel and are then injected into the floating gate 108 of the third gate structure 106 to fulfill programming. Such electron injection method for programming is called SSI and can fulfill programming with a small programming current. However, operations on single memory bits of the existing memory are unachievable, and thus, storage-computation integrated operations cannot be achieved.

Shanghai Huahong Grace Semiconductor Manufacturing Corporation


A plant for transmitting electric power is provided. The plant has a direct voltage network connected to at least one alternating voltage network through a station. The station transmits electric power between the direct voltage network and the alternative voltage network and has at least one converter for converting direct voltage to alternating voltage and for converting alternating voltage to direct voltage. The plant comprises a DC/DC converter connected between the poles of the direct voltage network. The DC/DC converter is adapted to create a higher voltage between the poles on the station remote side of the DC/DC converter than on the station near side.

The present invention relates to a plant for transmitting electric power comprising a direct voltage network for High Voltage Direct Current (HVDC) and at least one alternating voltage network connected thereto through a station. The station has at least one VSC-converter adapted to convert direct voltage into alternating voltage and the converse, and for transmitting electric power between the direct voltage network and the alternating voltage network.
Such a plant has recently become known through the thesis "PWM and Control of Two and Three Level High Power Voltage Source Converters" by Anders Lindberg, Kungliga Tekniska Hogskolan, Stockholm, 1995, in which publication such a plant for transmitting electric power through a direct voltage network for HVDC is described. Before the issuance of the thesis, plants for transmitting electric power through a direct voltage network for HVDC have been based upon the use of line-commutated CSC (Current Source Converter) converters in stations for power transmission. By the development of IGBTs (Insulated Gate Bipolar Transistor; a bipolar transistor having an insulated gate) for high voltage applications, and the suitability to connect them in series in valves in converters, since they may easily be turned on and turned off simultaneously, VSC (Voltage Source Converter) converters for forced commutation have now become an alternative. This type of transmission of electric power between a direct voltage network for HVDC, being voltage-stiff therethrough, and alternating voltage networks connected thereto, offers several important advantages with respect to the use of line-commutated CSCs in HVDC. Thus, the consumption of active and reactive power may be controlled independently of each other, and there is no risk of commutation failures in the converter, and thereby no risk of transmission of commutation failures between different HVDC links, which may occur in line-commutation. Furthermore, there is the possibility to feed a weak alternating voltage network or a network without any generator of its own (a dead alternating voltage network). Further advantages are also provided.
In a plant of this type, it is desirable to operate without expensive transformers and still obtain the exact voltage asked for on the direct voltage network.


A foldable, stackable box assembly, having a collapsible sleeve component and a foldable container which is insertable into and out of the sleeve by a built-in handle mechanism. The container and sleeve are formed of these folding blanks which, when assembled, create a sturdy, slidable drawer-like box assembly. The front of the container has a compressible handle-like mechanism. It is a characteristic of the container/drawer that the front wall has, extending down from the top, a panel which extends forwardly and terminates short of the bottom of the front of the container/drawer. It is held there by compressible panels, and forms the handle mechanism under which a user can insert hand or finger to pull out the container/drawer from the sleeve.

Not applicable.
Not applicable.
This present invention relates to an improvement in knock-down, collapsible, foldable boxes, and more particularly to shoe boxes for easy storage and shipment, both in the knock-down or assembled state while transporting shoes and, when set up and configured for use, are stackable upon one another and have a removable drawer-like container which, when removed, permits easy retrieval of the shoes within, especially in a shoe store, without adversely affecting the remainder of the stack. It must be understood that, though this invention was prompted by a need for better shoe boxes adapted to storage (in both shoe manufacturing and in retail stores), retrieval, and return, it is capable of being used for any product storage and is not limited to shoes and shoe boxes.
Currently shoes are shipped from manufacturer or distributor to a retailer in a pre-formed, generally pasted, shoe box. The typical box has a bottom part and a top part. The bottom part has a base or bottom with four upstanding walls which form a container. The top part is the cover which has an upper base with four downwardly extending walls which snugly fit around the four upstanding walls to cover the opening of the bottom part. Typically the four downwardly extending walls are considerably shorter in length than are the four upstanding walls. This box thus is a pasted-up open-top box closed by a removable lid adapted to fit snugly around the outside of the open-top of the box.
It is customary in shoe stores to stack such boxes on top of one another and to have numerous such stacks or columns abutting one another. In such stacking configurations, the stacks can be extremely high consisting of many boxes stacked upon one another. Stacking and columning are generally done in some organized fashion by style and size for example. Shoe boxes such as these generally have information about the shoe style, size, and color which is printed on one or more of their upstanding walls. When a shoe salesperson, for instance, needs a pair of shoes which are in a box on top of the stack, there is no problem in merely taking that box out to the showroom and returning it to the same location without disrupting the organization of the stacks. When a desired shoe is in a box or boxes below the top of a stack, in the middle, or at or near the bottom, pulling the box from the stack is more difficult. Box tops and bottoms can get damaged.
For organizational purposes, it is best that the space created by the removed box remain unfilled so that, if a sale is not consummated, the box may be returned to its proper organizational location. This is not what usually occurs however. Once a box is removed from the stack, the boxes in that stack above the removed box simply fall into the space created by the removed box. Given the configuration of the box and lid, the descent generally is not smooth and orderly thereby creating an unsightly, scattered, appearance and unsettling the organization of the stacks.
The present invention eliminates the bulk associated with shipping the pre-formed pasted boxes to the shoe manufacturer, for example, and eliminates the problems associated with removing boxes from their stacks in the retail shoe store. In addition, the present invention, with its sleeve, slidable and removable container, permits re-use of the container and placement of the container into its original or any vacant sleeve.
Accordingly, several objects and advantages of my invention are to:
a. provide boxes which are easy to manufacture and less bulky to ship to the shoe manufacturer, to the retailer, and to an end-user;
b. provide boxes for products which are stackable and maintain their stack integrity after the container portion of a box is removed from the stack;
c. provide boxes for products which facilitate retrieval of the product therefrom and return thereto;
d. provide boxes for products which are not limited to a single product size and style but which are relatively fungible and re-usable; and
e. provide product boxes which facilitate reorganization of a retailer""s product inventory.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.
The above-noted problems, among others, are overcome by the present invention. Briefly stated, the present invention contemplates a knock-down, foldable, collapsible, stackable box assembly which has a sleeve and a removable container insertable into and out of the sleeve. The container and sleeve are formed of folding blanks which, when folded and assembled, create a sturdy, slidable drawer-like box assembly with the inner container being the removable drawer. The front of the container has a compressible handle-like mechanism which, when one or more box assemblies are shipped together, especially in large shipping containers, compresses without damage to its structure or function. When not in use by the retail purchaser or end-user, the sleeve may be unfolded and collapsed flat and the container may be unfolded and unassembled into a flat blank. When needed, each is easily re-folded, re-assembled into useable box, drawer-like structures. Any suitable materials may be used for the box assembly but a cardboard or cardboard-like materials are best.
The foregoing has outlined the more pertinent and important features of the present invention in order that the detailed description of the invention that follows may be better understood so the present contributions to the art may be more fully appreciated. Additional features of the present invention will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and the disclosed specific embodiment may be readily utilized as a basis for modifying or designing other structures and methods for carrying out the same purposes of the present invention. It also should be realized by those skilled in the art that such equivalent constructions and methods do not depart from the spirit and scope of the inventions as set forth in the appended claims.


A fluid dispersion and delivery assembly (49) includes first and second syringes (28,50) containing a hemostatic solution (38) and a flowable gel material (58), fluidly coupled together by a fluid transfer assembly (2). The fluid transfer assembly includes a double Luer fitting (4) and a hollow tube (6), having openings (24,22) at its ends (16,18), reciprocally mounted within the fitting. This permits the hemostatic solution in the first syringe to be evenly dispersed into the flowable gel material within the second syringe by simply pressing the plunger (46) of the first syringe. After dispersion, the fluid transfer assembly is dismounted from the second syringe to permit combined material (62) within the second syringe to be dispensed.

The present invention relates generally to methods and devices for dispersing a first, fluid material into a second material. It is particularly useful for evenly dispersing a first, fluid material from a first syringe into a second material within a second syringe.
The use of two syringes to mix two substances and then dispense the mixture from one of the syringes is known. U.S. Pat. No. 3,700,215 to Hardman et al. illustrates the outlet nozzles of a pair of syringes connected by a coupler. A perforated mixing tube, with perforations along the entire length thereof, is slidably mounted within the coupler so that depressing the plunger on one syringe simultaneously drives the contents of that syringe into the other syringe along with the perforated mixing tube. The plunger of the other syringe is then depressed causing the contents to be driven back into the first syringe along with the perforated mixing tube. This process is repeated a desired number of times until the substances are appropriately mixed.
U.S. Pat. No. 4,743,229 to Chu illustrates a pair of syringes coupled at their outlet nozzles. One of the syringes contains a fibrillar collagen which is injected into the second syringe which contains particulate mineral material. Excess air in the first syringe containing the particulate mineral material is expulsed through a porous piston which permits air, but not the mineral material, to pass through the piston. The collagen-mineral mixture is then dispensed from the second syringe as a collagen-based bone repair preparation.
The Chu patent shows a relatively simple system for combining two materials within the barrel of one syringe. However, the injected material is not necessarily evenly dispersed within the other material. Therefore, unless the materials are driven back and forth between the two syringes as is taught in the Hardman patent, neither good dispersion nor good mixing will likely occur. However, certain materials, such as the collagen/mineral preparation of the Chu patent, are not amenable to such flow back and forth between two syringes. Also, other preparations, such as certain insulin preparations, may be sensitive to mechanical agitation or an increase in temperature which could be created while being forced back through a relatively small orifice between the two syringes.

Fluid dispersion and delivery assembly and method


An apparatus for producing book blocks from a stack of aligned signatures each having a fold and which together form a spine of a book block. An arrangement for stitching stitches the signatures together with at least two spaced transverse seams formed of a double strand of binding thread passing through each of the folds of the signatures from a location outside of the signatures and extending along an inner edge of each of the folds to an exit point in each of the folds. The transverse seams include a chained transverse seam having loop-like binding thread sections. An interrupting arrangement interrupts the chained transverse seam at an end region of the book block such that a last formed loop-like section of the binding thread remains unchained and is left at the end region of the book block. An unreleasably fastening arrangement unreleasably fastens the last formed loop-like section to either the chained transverse seam and the folds of the signatures.

The present invention relates to an apparatus for producing book blocks from a stack of signatures that are aligned with one another on their flat sides and are stitched together by means of a binding thread, with their folds forming the spine of the book block. The book block has at least two spaced transverse seams formed of a double strand of binding thread that passes through the folds of the signatures from the outside and extends along the inner edge of the fold to their 15 exit points. One of the two transverse seams is formed of a chain of loop-like binding thread sections that are successively pulled out of the folds of the signatures, with the chain being interrupted after a stack section has been formed that determines the book block.
EP-A-0,295,220 discloses an apparatus of the above formulated type according to which book blocks are separated from a stack of signatures by cutting through the binding thread at the so-called flat seam under the influence of a tensioning force generated by the moving stack of signatures. These threads are pulled out of the fold of the signatures at the adjacent loop seam or chained seam, respectively, and then cut apart by a knife. This manner of proceeding produces a breather or relaxation, respectively, between the signatures which has a negative influence on the stability of the book blocks and the compactness to be produced by the stitching.
By changing the binding thread from the hook needle to the knife, an additional unreliability moment is created with respect to the transfer.

Apparatus for producing book blocks from a stack of signatures


A separator for a fuel cell, includes: a metal plate; a first electro-conductive resin layer formed on a first surface side of the metal plate; a second electro-conductive resin layer formed on a second surface side of the metal plate opposite to the first surface side; and a flow channel in which the metal plate and the first and second electro-conductive resin layers have a wavy shape in cross section.

There is known a fuel cell including a pair of separators sandwiching a membrane electrode gas diffusion layer assembly. Such a separator is formed with flow channels having a wavy shape in cross section. A reactant gas flows along the flow channels on the membrane electrode gas diffusion layer assembly side. A coolant flows on the side opposite to the flow channels. The membrane electrode gas diffusion layer assembly is sandwiched by the flow channels of the separators. In addition, there is known a separator including a metal plate and electro-conductive resin layers provided on respective surfaces of the metal plate. As for the flow channels, the metal plate and the electro-conductive resin layers are formed to have a wavy shape in cross section (see, for example, Japanese Unexamined Patent Application Publication No. 2003-297383).
As for the flow channels, the metal plate also has a wavy shape. Thus, a depth of the flow channel may partially increase an expansion amount of the metal plate and may decrease its thickness in processing, which may decrease its stiffness. In addition, if the depth of the flow channel is formed to be shallow in order to suppress such a decrease in stiffness of the metal plate, the pressure loss of the reactant gas and the coolant flowing along the flow channels may increase. Further, if a width of the flow channel is increased while ensuring the depth thereof in order to suppress the decrease in stiffness of the metal plate as described above, the membrane electrode gas diffusion layer assembly might not be sandwiched at a suitable interval. This might decrease an area of a membrane electrode assembly on which sufficient sandwiching force exerts, so that the membrane electrode assembly might repeatedly swell and expand in the area on which small sandwiching force exerts, and its strength might decrease.

Separator for fuel cell, fuel cell, and manufacturing method of separator for fuel cell


A method of controlling an arc welding system during a welding process is disclosed. The welding process has a plurality of welding cycles in which a consumable electrode is advanced towards a workpiece. The method includes dynamically regulating a rate of advancement and instantaneous melt rate of the electrode during each welding cycle in response to predetermined events occurring during the welding process. The melt rate may be coordinated with the rate of advancement of the electrode to provide a wide range of stable deposition rates with a shielding gas such as CO2. An arc welding system for carrying out the method is also disclosed.

In a typical GMAW process, a welding circuit is established which includes a consumable electrode, a workpiece and a power source. The electrode is generally a solid wire and not only conducts the electric current that sustains the arc, but also melts and supplies filler material into the joint. A shielding gas such as argon or carbon dioxide (CO2) or blends of argon and helium with CO2 and/or oxygen may be supplied during the welding process to support the arc and prevent the molten metal reacting with oxygen and nitrogen in ambient air.
A GMAW process can be made to operate reliably over a wide range of deposition rates when used with an argon or argon-helium based shielding gas. At low deposition (or wire feed) rates, current densities in the wire electrode are low, and the process operates in short-circuit transfer mode. In this mode, the molten droplet formed at the end of the electrode regularly touches the weld pool, and metal transfer is achieved through a combination of surface tension and electromagnetic forces. This mode can be made to operate very stably with correct selection of key process parameters.
As the wire feed rate is increased, the current density must also increase so that the melting rate matches the feed rate. For mean currents of approximately 170 A to 200 A for 0.9 mm diameter wire, the process operates in a globular transfer mode. This mode is characterised by large droplets being detached by a combination of gravity and electromagnetic forces at irregular intervals. The irregular metal transfer results in poor bead appearance and low operator appeal. In these current ranges, the GMAW process is preferably operated in pulsed spray transfer, an open-arc process where the metal transfer is regular and can be precisely controlled by the current wave form. A droplet of consistent size is propelled across the arc at regular intervals with minimal spatter to produce a smooth weld bead of intermediate size.
Above approximately 200 A for 0.9 mm wire, the process transits to spray transfer mode. In this mode, fine droplets having a diameter less than that of the electrode are propelled from the electrode towards the weld pool at a high speed across the open arc. As current is increased, the droplet becomes finer and the electrode end becomes more tapered. The constant metal transfer produces a smooth weld bead. The high current produces high heat input and relatively wide bead. Large fusion areas and deep penetration can also be achieved if the travel speed is high enough to avoid "puddling", but without producing undercut. Due to the large, highly liquid weld pool, the positional capability of this mode is mostly limited to down hand. At very high currents (above 400 A), and where the electrode stick out length is sufficiently long, rotating arc transfer can be produced. Under these conditions, it is thought that the resistive preheating of the electrode is sufficiently high to soften it to a point where it is rotated by the non axial arc forces. If very high deposition rates are required, then a larger electrode is used in spray mode at lower wire feed rates.
Due to the availability of a number of distinct operating modes as mentioned above, the argon-based GMAW process offers the ability to operate over a very wide range of deposition rates for a given electrode size. As such it has been widely used in the welding industry.
The major disadvantage of argon is its comparatively high cost of production, compared to CO2. As CO2 is a by-product of processing such as brewing, it is relatively inexpensive since low temperature distillation equipment is not required. However there are a number of limitations which need to be overcome to using CO2-shielded GMAW for high volume production welding.
The most significant difference between GMAW processes using CO2, and argon based shielding gas is that the CO2 process does not exhibit a spray transfer mode. For low currents (less than 170 A for 0.9 mm wire) the CO2 process operates in dip transfer mode. The overall behaviour is similar to that for argon, but spatter levels tend to be higher and the bead finish is not smooth.
While it is possible to deposit a weld bead using globular transfer by increasing the current, the resulting weld bead has a poor appearance, arc stability is also poor, and spatter is very high.

Control method and system for metal arc welding


The invention relates to a device for optical distance measurement, in particular a device functioning in accordance with the phase measurement principle, having at least one transmission unit (12) equipped with at least one light source (22, 24) for transmitting modulated optical measurement radiation (16) toward a target object (20), and having a reception unit (18) for receiving the optical measurement radiation (17) returning from the target object (20).

The present invention relates to a device for optical distance measurement and to a method for optical distance measurement by means of phase modulation.
Optical distance measuring devices as such have been known for a long time and have in the meantime also been commercially marketed in a wide variety of embodiment forms. These devices emit a modulated light beam, which is oriented toward the surface of a target object to be measured, whose distance from the device is to be determined. Part of the light reflected against or scattered back by the target surface is detected again by the measuring device and used to determine the desired distance.
The application field of such distance measuring devices generally includes distances in a range of typically between a few centimeters and several hundred meters.
Depending on the distances to be measured and the reflectivity of the target object, different demands are placed on the light source, the quality of the measurement beam, and the detector.
Depending on the orientation of the transmission and reception conduits necessarily provided in the device, the optical distance measuring devices known from the prior art can essentially be divided into two categories. On the one hand, there are devices in which the transmission conduit is situated a certain distance apart from the reception conduit so that the respective optical axes are parallel to each other. On the other hand, there are monoaxial measuring devices in which the reception conduit is coaxial to the transmission conduit.
The biaxial measurement systems have the advantage of not requiring a complex beam splitting to select out the returning measurement signal, thus permitting better suppression of an optical crosstalk, for example, from the transmission conduit directly into the reception conduit.
On the other hand, biaxial distance measuring devices have among other things, the disadvantage that in the range of shorter measurement distances, detection problems can arise due to the presence of a parallax. The projection of the target object onto the detector surface of the measurement receiver integrated into the unit, which projection is still unambiguously situated on the detector at large target distances, begins to creep away from the optical axis of the reception branch as the measurement distance decreases, and also experiences a variation in the beam cross section in the detector plane.
This means that without further steps being taken in the unit, in the close detection range, i.e. for a short distance between the target object and the measuring device, the measurement signal can approach zero.
DE4316348A1 has disclosed a device for distance measurement, having a visible measurement beam generated by a semiconductor laser whose reception device includes a light guide whose outlet is connected to an optoelectronic converter. The light entry surface into the fiber of the light guide is situated in the projection plane of the reception lens of this device for large object distances and can be shifted out of this position laterally in relation to the optical axis.
In this way, measurement beams that arrive into the reception lens at ever greater inclination at short object distances can be guided by the device according to DE4316348A1 onto the light-sensitive surface of the detector through tracking by the optical fibers, without requiring spatial movement of the detector.
The required electronic control of the tracking and the use of additional, in particular moving parts in the distance measuring device according to DE4316348A1 entail a not insignificant amount of effort, which increases the complexity and therefore the cost and susceptibility of such a system to malfunction.
There are also known optoelectronic distance sensors that function in accordance with the so-called triangulation principle. DE3703422A1 has disclosed such an optoelectronic distance sensor functioning according to the triangulation principle, which has at least one first pilot beam source 7 that makes the projection beam path of the sensor visible, which is inclined in relation to the measurement beam. In sensors of this kind, a position-sensitive detector is used, which is offset in relation to the transmission direction. Since the incidence point of the measurement beam reflected by the target object is a function of the distance of the detector from the target object, its position can be used to calculate the distance between the detector and the target object.
DE29615514U1 has disclosed an electronic distance measuring device that has a flat measuring bar, which is situated on the side of the housing of the measuring device and can be slid in relation to it. The flat measuring bar serves to establish a reference plane spaced a definite distance apart from the measurement plane of the distance measuring device; the measuring device is then able to detect small distances very precisely by measuring a measurement value greater than the minimum and then subtracting the distance between these two planes to determine the measurement value. In a suitable fashion, the subtraction of this distance between the planes occurs automatically in that the degree to which the flat measuring bar extends out from the measuring device housing is measured at the push of a button and can be automatically taken into account. In this way, the measuring device according to DE29615514U1 is able to determine very small distances with a high degree of precision, even when using the phase-comparison method to determine the desired distance.
Triangulation sensors of this kind are typically used in industrial sensors for distance measurement, for example in machine tools to determine short movement distances of a moving part of such a machine tool. The triangulation measurement method only permits measurements in a small measurement range, but is able to achieve high levels of precision.

Device and method for optical distance measurement

Abstract: According to the present invention, the device has means (51, 55, 68) that enable a measurement of distances from a target object (20′) by means of a triangulation method.

Abstract: The invention also relates to a method for optical distance measurement in which it is possible to switch back and forth between a phase measurement method for determining a distance of a distance measuring device from a target object (20, 20′) and a triangulation method for determining this distance.


An OFDM packet is initially detected by auto-correlating short training symbols to generate an initial packet detection signal. The initial packet detection signal may be used to initiate a coarse timing synchronization process, which may use a short symbol matched filter. A coarse timing signal may be generated from at least some of the short training symbols by correlating sampled short training symbols with short filter matched coefficients. The coarse-timing signal may be used to initiate the operation of a fine timing synchronization process, which may use a long symbol matched filter. A fine timing signal may be generated from at least some of the long training symbols by correlating sampled long training symbols with long filter-matched coefficients. The fine timing signal may be used to initiate channel estimation by performing a Fast Fourier Transform (FFT) operation on the long training symbols. The fine timing signal may also be used to initiate data signal processing using the channel estimation and may include starting an FFT operation on data symbols.

Orthogonal frequency division multiplexing (OFDM) is a multi-carrier transmission technique that uses orthogonal subcarriers to transmit information within an available spectrum. Because the subcarriers may be orthogonal to one another, they may be spaced much more closely together within the available spectrum than, for example, the individual channels in a conventional frequency division multiplexing (FDM) system. To help achieve orthogonality, a subcarrier may have a null at the center frequency of the other subcarriers. Orthogonality of the subcarriers may help prevent inter-subcarrier interference within the system. Before transmission, the subcarriers may be modulated with a low-rate data stream. The transmitted symbol rate of OFDM symbols may be low, and thus the transmitted OFDM signal may be highly tolerant to multipath delay spread within the channel. For this reason, many modem digital communication systems are turning to OFDM as a modulation scheme for signals that need to survive in environments having multipath reflections and/or strong interference. Many wireless communication standards have already adopted OFDM including, for example, the IEEE 802.11a standard, the Digital Video Broadcasting Terrestrial (DVB-T) broadcasting standard, and the High performance radio Local Area Network (HiperLAN) standard. In addition, several industry consortia, including the Broadband Wireless Internet Forum and the OFDM Forum, are proposing OFDM for fixed wireless access systems.
One problem with OFDM systems is that they may be more sensitive to phase noise and frequency offset relative to single carrier systems. Unlike single carrier systems, phase noise and frequency offset in OFDM systems introduce interference, including intercarrier interference and intersymbol interference. To demodulate the subcarriers, an OFDM receiver may perform a synchronization to determine the location of symbol boundaries and timing instants. Inaccurate synchronization may result in a reduced or loss of orthogonality between the subcarriers resulting intercarrier and/or intersymbol interference and reduction in system performance. Achieving accurate synchronization in an OFDM system may be more critical than in single carrier systems. Conventional OFDM systems have used a cyclic prefix and/or special OFDM training symbols to help achieve symbol timing and frequency synchronization, however channel effects, such as linear distortion, in a multipath channel make this a difficult task.
Another difficulty with OFDM systems is properly detecting an OFDM packet. Channel effects, for example, increase the probability of false packet detection, which may be referred to as a false alarm probability. A high false alarm probability may result in reduced system performance.

Receiver and method to detect and synchronize with a symbol boundary of an OFDM symbol