Described herein is an optically readable memory device comprising a molecular memory obtained using carbon nanotubes. In particular, the molecular memory uses, as memory element, a bundle of carbon nanotubes, for which it is possible to obtain at least two stable states by modifying their geometrical configuration and, consequently, their optical transmission properties.

At present, the nonvolatile memories with highest performance are Flash memories. Flash-memory technology was initially launched on the market as an alternative to EEPROM memories. Like EEPROM memories, Flash memories can be erased and reprogrammed electrically with generally high limits (˜105 cycles) on the number of erase/write cycles. Unlike EEPROM memories, in a Flash memory there is no need to erase the entire memory array in order to store new data in a portion thereof. In fact, Flash memories are typically organized in sectors, each of which can be reprogrammed individually, with different access times for the read operation (˜50 ns), the write operation (˜5 μs) and the erase operation (˜100 ms).
As is known, a Flash memory cell is basically made up of a bulk, an NMOS transistor provided in the bulk and comprising a drain region and a source region that are separate from one another, a control-gate region arranged over the bulk between the drain and source regions, and electrically insulated from the bulk by means of interposition of an insulating material, typically oxide, and a floating-gate region, arranged between the bulk and the control-gate region and electrically insulated therefrom. The floating-gate region is completely insulated from the external environment, and its potential depends upon the electrical charge present therein and upon the capacitive couplings with the other devices of the memory cell.
Furthermore, the memory cell is manufactured in such a way as to obtain a maximum capacitive coupling between the floating-gate region and the control-gate region, which, instead, can be contacted from outside.
The working principle of a Flash-memory cell is based upon the trapping of some electrons in the floating-gate region, the said electrons generating an electrical potential that compensates the electrical potential applied to the control-gate region, thus making it necessary to bring the latter up to a higher electrical potential to obtain a strong inversion in the channel.
In order to distinguish the two possible states (OFF/ON) of the memory cell, a voltage jump is required, which has the function of generating a variation in the threshold voltage of the MOS transistor. This variation determines a distinction between the state in which the floating-gate region does not contain any charge, characteristic of a virgin memory cell or an erased memory cell (represented by a logic "1"), and the state in which the floating-gate region contains a negative charge, characteristic of a programmed memory cell (represented by a logic "0").
The operation of programming a flash-memory cell envisages the creation of a channel for the electrons in the space-charge area of the drain region, the so-called "pinch-off area", in order to supply a certain number of electrons with the energy necessary to overcome the potential-energy barrier of the oxide-silicon interface. In this case, by applying an appropriate electrical field, it is possible to favor the migration of these electrons to the floating-gate region, storing on the latter a negative charge. This technique is commonly known as "channel-hot-electron (CHE) injection".
In flash memories, the erase operation, which consists of removing electrons from the floating-gate region, is obtained by the tunnel effect through the gate oxide, also known as the Fowler-Nordheim. (FN) effect. In this type of memory, erasure by bytes cannot be obtained. As is known, in face, in a typical array architecture of a flash memory, the source regions of all the memory cells are connected to the same common source line, the drain terminals of the memory cells belonging to the same column are connected to the same bit line, and the gate terminals of the memory cells belonging to the same row are connected to the same word line, so that, during the erase operation, all the memory cells belonging to a given sector are simultaneously erased. The capacity of non-volatile memories is strictly linked to the dimensions of the memory cells, which form the array, and to the complexity of the structure, whilst the dimensions of the memory cells are, in turn, strictly linked to the dimensions of the elementary electronic devices that form them.
In the last few years, the substantial success of CMOS technology has been determined basically by the possibility of constantly reducing the size of electronic devices. In fact, this technology follows the so-called Moore's law, according to which the number of the transistors that can be manufactured on an integrated circuit and, hence, the computing speed should double in a time range of between 18 and 24 months.
However, it is a common conviction that conventional silicon microelectronics will not be able to continue indefinitely to follow this law, in so far as sooner or later physical limits will certainly be reached that will prevent current circuits from functioning reliably at nanometric dimensions, whereas, at the same time, an exponential increase in production costs will render any further increase in the levels of integration prohibitive. In fact, as the density of the-electronic devices on a chip increases, phenomena such as the need to dissipate the heat generated by such densely populated circuits, and the transition from the classical behavior to the quantistic behavior of the charge carriers will considerably slow down progress.
The need to solve these problems has pushed research towards the study of new technologies, based upon the use of organic materials that will be able to replace either completely or partially silicon in the fabrication of electronic devices.
In fact, molecular electronics affords the potential for overcoming the limits of on-silicon technology, in so far as it is possible to manufacture single-molecule devices which are organized in parallel by means of self-assembly techniques that are also economically advantageous.
In particular, whilst it is possible, with current technologies, to manufacture high-density Flash memory units with capacities in the region of 64-128 Mb, but with high costs, in future, by resorting to molecular memories, it will be possible to achieve memory capacities of various tens or hundreds of gigabits, in which each memory cell will be formed by one or more molecules, the structural configuration of which may be associated with different possible and modifiable states by means of interactions at an atomic level or at the level of individual electrons.
In recent studies, it has been shown that it is possible to manufacture a non-volatile memory device using a particular protein, rhodopsin. The rhodopsin bacterium, for example, is a photochromic molecule, i.e., a molecule that is able to change color, and hence absorption spectrum, following upon exposure to photons of an appropriate wavelength. In the photocycle of the protein, shown in FIG. 1, two states are distinguishable, designated by bR and Q, which represent, respectively, the logic states "0" and "1". Furthermore, in FIG. 1, represented by the solid line, are the thermal relaxations, whilst, represented by the dashed line, are the transitions induced by light.
An article appearing in Scientific American Vol. 82 (1994), J. Phys. Chem. B. Vol. 103 (1999) describes the manufacture of electro-optical biomemories, which are based upon the rhodopsin bacterium, in which the reading and writing system employs two laser arrays arranged orthogonally to one another, and a detector array.
For writing the data, a yellow paging laser is used to bring the molecules into the logic state "0". A spatial light modulator (SLM), which is a liquid crystal display (LCD) array, partitions this beam, so as to excite a two-dimensional surface of material inside the transparent envelope. This surface of optically stimulated material represents the equivalent of a data page.
Before the protein returns to its initial state, a red laser is activated, arranged perpendicular to the yellow laser used for writing the data. Another spatial light modulator displays the binary data and sections this beam so as to display light spots on the page. The molecules arranged at the spots go into the Q-state and represent the logic states "1" on the page. The remaining molecules of the page return to the initial state and represent the logic state "0".
Reading of the data is also obtained optically, by activating the yellow laser, which excites the page upon which the yellow light impinges to the logic state "0". This operation is performed with the purpose of further differentiating the absorption spectra of the states that encode the logic "0" and the logic "1". After 2 ms, the page is impinged upon by a low-intensity red laser, the latter condition being required to prevent any jump into the Q state. The molecules that encode the logic "0" absorb red light, whilst the molecules that encode the logic "1" allow themselves to be traversed by the light beam. In this way, on the charge-injection photodetector array (CID), there is reconstructed an image, formed by light spots and dark spots, corresponding to the information contained in the memory in the form of binary data.
In order to erase the information, a short pulse of blue laser light suffices to convert the molecules from the Q state to the bR state.
This type of optically readable molecular memory presents a number of advantages over traditional semiconductor memories, these advantages being offset, however, by a number of limitations. In the first place, it is possible to produce, in large quantities and at a low cost, the protein on which a molecular memory of this type is based, with performance levels that are very similar to those of traditional semiconductor memories. In addition, the system can be integrated in a high-density architectural configuration, the minimum dimensions of which chiefly depend upon the quantity of biomolecules sufficient for guaranteeing operation, on a statistical basis, of the rhodopsin-bacterium photochromic system.
The limits of memories of this type are prevalently linked to the integratability of the biological material with the silicon and with the cleanroom process steps. In particular, there may arise problems connected to the stability of the protein/silicon link and to the conformational and hence functional stability of the proteins themselves at the interface with the silicon. In addition, a molecular memory that employs the rhodopsin bacterium would have access times in writing and erasure of the order of some milliseconds for a single cell.
Once again, in the framework of biomemories of the type described above, molecular-memory devices have been proposed, which use different types of molecules (rotaxane, pseudo-rotaxane, catenane). In particular, a memory of this type is described in the U.S. Pat. No. 6,128,214, granted on Oct. 3, 2000 in the name of Hewlett-Packard.
Broadly speaking, the above memory device, which is illustrated in FIG. 2, is formed by two parallel layers of nanometric conductors arranged perpendicular to one another, between which there is interposed a layer of molecules. A bistable molecule is arranged in a position corresponding to each intersection of the pairs of conductors and defines, in effect, a switch. An applied voltage modifies the electronic state of the molecules and, hence, the resistance between the top conductor and the bottom conductor. The switches are activated by electrochemical oxidation or reduction of the molecules. When a switch is closed electrochemically, the resistance between the connected conductors is low, and this state constitutes a logic "1". When the switch is open, the resistance is high, and this state represents a logic "0". In order to read the state of the switch, it is necessary to apply another voltage, the value of which is such as motto cause switching of the state of the junction. Consequently, the reading process is not destructive.
The limits of the above device are basically linked to the difficulty of arranging the molecules in contact with the nanometric conductors, which are made of silicon or metal, as well as to the instability of the molecules themselves to high temperatures.
In order to overcome the drawbacks of the molecular memories described above, in the article "Carbon Nanotube-Based Nonvolatile Random Access Memory for Molecular Computing", Science, Vol. 389 (5476), Jul. 7, 2000, 94-97, there is proposed the manufacture of nonvolatile memories based upon the use of molecular structures known as carbon nanotubes (CNTs).
It is known that carbon atoms have the property of organizing themselves to form different structures, giving rise to materials of different forms. In fact, a diamond is formed by carbon atoms organized in tetrahedrons, whilst graphite is formed by carbon atoms organized in planar structures. Consequently, these two allotropic forms, albeit originating from the same type of atoms, exhibit structural properties (hardness, elasticity, friction) and functional properties (electrical conductivity, color, etc.) that are highly different and frequently opposite to one another. The structural characteristics, such as hardness and refractoriness, of graphite and diamond render hard to implement, on a device, at nanometric scales, a top-down approach, through which it is possible to arrive at the desired dimensions with successive removal of a macroscopic quantity of a material. Instead, a bottom-up approach, through which it is possible to manufacture, and subsequently assemble, nanoscopic components, starting from individual atoms or molecules, is rendered possible by the use of another allotropic form of carbon, namely fullerene.
Belonging to the family of the fullerenes C60, also known as buckyball, which presents a molecular structure having the shape of a polyhedral cage, consisting of pentagons and hexagons. The buckyball structures that develop as long cylinders, rather than as spheres, are called carbon nanotubes. Their length may be millions of times longer than their diameter. In addition, using known techniques of molecular synthesis, there have been observed, in the laboratory, single-walled cylindrical structures (single-walled nanotubes—SWNTs), having a diameter of 1-2 nm, and multiple-walled structures (multiple-walled nanotubes—MWNTs), i.e., formed by coaxial cylinders with diameters of a few tens of nanometers.
Carbon nanotubes are organic molecules formed by a number of interconnected carbon atoms in a cylindrical structure, characterized by a small weight, and they present exceptional elastic properties, which render them extremely hard, but also capable of undergoing large deformations without breaking. Thanks to their exceptional property of conducting electrical charges, carbon nanotubes, since they can be configured both as conductors and as semiconductors, are suitable for forming components of a new class of nanometric electronic devices.
A nanometric electronic device is described in the above-mentioned article and is shown in FIGS. 3a and 3b. The nanometric electronic device essentially consists of a substrate (for example, doped silicon) on which nanotubes are arranged in two different levels orthogonally with respect to one another and vertically separated by a distance of 1-2 nm, in such a way as to cross at a point corresponding to each memory element. Arranged between the conductive substrate and the first level of nanotubes is a dielectric (for example, silicondioxidee, SiO2), with the purpose of insulating the second level of nanotubes from the substrate, which is polarized with a reference voltage (ground). Moreover, the nanotubes of the second level are arranged on top of spacers made of (organic or inorganic) dielectric material, so as to be insulated from the nanotubes of the first level. Instead, no dielectric is interposed at the points where the nanotubes of the second level and the nanotubes of the first level cross.
The nanotubes are then connected to the rest of the circuit, outside the grid, by means of contacts, made, for example, of gold, These contacts being used both during reading and during writing. In particular, writing of the single memory element is performed by imposing an electrostatic action between the substrate and the point of crossing of the two nanotubes, through the dielectric.
The voltage values imposed depend upon the thickness of the dielectric and upon the energy levels required for guaranteeing a change of state of the nanotube (ON/OFF), in such a way that such changes will be reversible. The OFF and ON states for the individual memory element are shown in FIGS. 4a and 4b, respectively. In particular, a voltage value of 4.5 V for the ON state and a value of 20 V for the OFF state have been estimated.
Consequently, reading of the individual memory element would be done electrically, always by means of the electrical contacts arranged on the edge of the grid, by measuring the resistivity associated to the two states ON/OFF.
The main limitations which, at the moment, prevent industrial development of the above approach are outlined in what follows.
A first limitation is represented by the fact that the techniques used for the manufacture of said architecture do not enable control of the nature of the nanotubes used. In particular, there will be a random distribution of metallic nanotubes (M) and semiconductor nanotubes (S). This implies that, in the read step, the values of resistivity measured on different cells that are in the same state, ON or OFF, undergo, even important, fluctuations according to the geometrical configuration (chirality) of the two nanotubes concerned. For instance, the crossings between nanotubes M-M, S-M, M-S, S-S are possible, to which different levels of resistivity are associated, corresponding both to the ON state and to the OFF state, even though the levels of resistivity for the two states ON-OFF remain, basically, distinguishable.
A second limitation, which may prevent operation of the nonvolatile memory architecture described herein, is represented by the possibility that, during reading operations, current paths are set up, which are able to falsify the interpretation of the state of an individual cell. This problem is known, and occurs, for example, in optical scanning systems of a matrix type. By way of example, FIG. 5 illustrates a schematic circuit diagram in which acquisition of the state is in effect falsified, as a result of the multiple paths of the current Generally speaking, this problem is solved using rectifying diodes connected in series to each sensing element so as to prevent the diodes from being traversed by reverse currents. In the case in point, this possibility would risk markedly influencing the complexity of the system, i.e., the final storage capacity, unless the rectification functions can be integrated by acting directly on the metal-semiconductor characteristics of the nanotubes. In this way, it would be possible to generate Schottky junctions, already integrated in the cell array.
A third limitation is represented by the fact that the configuration entails the manufacture, arrangement, and manipulation of individual nanotubes, appropriately organized and insulated from the rest of the structure. This operation is very difficult, as well as being costly, in so far as the products of the processes of synthesis are, generally speaking, bundles of nanotubes, and the extraction of a single molecule from the bundle would involve additional process steps, together with the manipulation of the molecules.

Optically readable molecular memory obtained using carbon nanotubes, and method for storing information in said molecular memory


A deficiency in a link in a messaging system is detected by sending across the link a request message that includes a coded data string, receiving across the link a reply message that includes the coded data string, and determining whether the travel time involved is excessive. To maximize the likelihood that the coded data string is included in the reply message, the coded data string is preferably included in both the subject and body fields of the request message.

The invention is directed to messaging systems.
A messaging system allows a user to direct a message from a source location, e.g., a messaging server, on the messaging system to a destination location, e.g., another messaging server, on the messaging system. Locations on the messaging system are connected by messaging links. Typically, these links include computer data connections such as network connections in a networked computer system. The message is delivered by transferring the message across one or more of the links to a mailbox located at the destination. The delivery is typically facilitated by router computers and gateway computers that allow the message to be transferred across numerous and disparate interlinked networks, including the Internet.
From time to time, a link in a messaging system develops a deficiency that causes a message delivery failure or a message delivery delay or both. A delivery failure is a failure of a message to arrive at the mailbox to which the message is directed. A delivery delay is a delay in the arrival of the message at the mailbox. A delivery failure or a delivery delay can occur if, e.g., the messaging system develops a computer hardware deficiency or a configuration deficiency that causes a message destination to become insufficiently connected with the messaging system. Such a failure or delay can also be caused by a deficiency involving computer software used in the messaging system. In addition, a message delivery delay can occur due to a significant increase in the link's message traffic, i.e., the volume of messages transferred across the link during a time period. Furthermore, if the link includes cables or wires, a delivery failure or delay can occur as a result of damage or wear involving the cables or wires.


An improved technique for decoding wherein the number of coefficients to be included in each sub-block is selectable, and a code indicating the number of coefficients within each layer is inserted in the bitstream at the beginning of each encoded video sequence. This technique allows the original runs of zero coefficients in the highest resolution layer to remain intact by forming a sub-block for each scale from a selected number of coefficients along a continuous scan. These sub-blocks may be decoded in a standard fashion, with an inverse discrete cosine transform applied to square sub-blocks obtained by the appropriate zero padding of and/or discarding of excess coefficients from each of the scales. This technique further improves decoding efficiency by allowing an implicit end of block signal to separate blocks, making it unnecessary to decode an explicit end of block signal in most cases.

Many applications, such as, multi-point video teleconferencing, the windowing of displays for workstations, video communications on asynchronous transfer mode ("ATM") networks, and broadcast high-definition television can benefit if video at various resolutions can be derived from an encoded bitstream. The simplest method of achieving this is the simulcast technique in which multiple independent coded replicas of a video sequence (each scaled to a different resolution) are simultaneously transmitted. In this approach, scaling is performed prior to the compression/decompression of each replica, and each resolution scale is then independently encoded and assigned a portion of the total available transmission bandwidth. As a result of his independent encoding and transmission, the simulcast technique requires a wide bandwidth.
A more bandwidth efficient alternative to simulcasting, is scalable video encoding. Frequency scaling is a low-complexity method of scalable video encoding in which a single video signal is transmitted to multiple receivers which decode images of varying resolutions from that signal depending upon the particular signal decoding scheme employed by each receiver. A specific encoding method to which frequency scaling can be easily applied uses discrete cosine transform ("DCT") blocks of original or prediction error pixels to derive blocks of frequency domain coefficients. Various subsets of these frequency domain coefficients can be used to generate different resolution scales for a given image. Such encoding may be implemented using a slightly modified version of the encoders disclosed in the International Standards Organization Committee Draft 11172-2, "Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5 Mbit/s," November 1991, and in "Video Coding Using the MPEG-1 Compression Standard," A. Puri, Proceedings of the Society for Information Display 92, May 1992, Boston.
The transform coding portion of these encoders computes the DCT as a function of the energy in the blocks it receives from an original image, or from the difference between the original and its prediction from a previously decoded image. Assuming an 8.times.8 picture element ("pixel") basic block size, each 8.times.8 pixel block of a picture is transformed into an 8.times.8 block of DCT coefficients. These coefficients are then quantized and scanned so that they may be converted into a one dimensional sequence. An entropy coder within the video encoder compresses the one dimensional sequence to a series of number pairs called run/levels. Within a run/level the first number represents the number of zero coefficients between the last two non-zero coefficients in the one dimensional sequence, and the second number represents the quantized value (i.e., quantization index) of the next non-zero coefficient in that sequence. The number of zero coefficients is called the length of "run of zeros". For example, the one dimensional sequence of quantized coefficients 1 1 0 0 5 0 0 0 6 3 0 0 4 0 0 0 . . . 0 results in the run/level sequence of (0, 1) (0, 1) (2, 5) (3, 6) (0, 3) (2, 4) (EOB). EOB, or End-of-Block, indicates that all of the remaining quantized coefficients are zeros. Prior to transmission, these pairs, including the (EOB), are encoded using variable-length codes ("VLCs") consisting of a sequence of binary digits obtained from a code table which is optimized to assign shorter codes to most frequent pairs occurring in typical video images. This way, long runs of zeros (which are common in motion compensated transform based image coding) can be efficiently coded. When the transmitted signal is received, or stored signal is retrieved, the VLCs are decoded and the run/level pairs are recovered. The non-zero quantized coefficients are then inverse quantized, the zero coefficients are reconstituted, and an inverse DCT ("IDCT") is performed on the entire block.
Frequency scaling allows for efficient encoding of video in a manner which facilitates the derivation of various resolutions at the decoder by using different IDCT block sizes. It can be shown that if a decoder applies the IDCT to an upper left corner sub-block of every received block of coefficients, it can generate lower resolution images. For example, if a 2.times.2 sub-block of an encoded 8.times.8 block is decoded, image resolution will be reduced by a factor of four both vertically and horizontally (referred to as f-scale 2 frequency scaling). In this manner, the frequency scalability can be implemented on the decoder without any modification to the encoder. However, because of the VLCs used for coding run/level pairs, there is no way to detect the end of a block (EOB), or the beginning of a new block, unless the entire block is decoded. As a result, in order to recover a sub-block, the variable-length word decoder must operate as though a full resolution image were being recovered (this requires very fast, expensive circuitry to be used to decode even low resolution images). Using unique marker codes to separate sub-blocks is not feasible because of the high overhead caused by such codes.
An existing method for obtaining a frequency scalable bitstream is to encode the coefficients from sub-blocks separately in a layered structure and multiplex them as slices of various layers in the bitstream. In this method, the lowest resolution layer keeps the basic structure of the bitstream hierarchy, but fewer DCT coefficients are included with each block (such as four coefficients for f-scale 2). The remaining coefficients for each block in the slice are sent in slave slices which are separated by independently identifiable bit patterns called slave slice start codes. One problem with this approach is that every coded block in each scale has an EOB associated with it to mark the last non-zero coefficient included in that scale. As a result, instead of sending a single EOB for each coded block as in non-scalable coding, multiple EOBs are sent which decreases the efficiency of the frequency scalable coding.
Another problem with this solution is the overhead it introduces over and above the overhead caused by the slave slice start codes. The arrows in FIG. 1A shows a typical zigzag scan of an 8.times.8 coefficient block (100), where each of the numbers corresponds to the location of the coefficient in the one dimensional sequence derived by the scan operation. FIG. 1B shows the zig-zag scanning pattern applied to 2.times.2 (101), 4.times.4 (102), and 8.times.8 (103) coefficient sub-blocks used with f-scale 2, f-scale 4, and f-scale 8 layers respectively. If coefficients 3 and 4 are zeros, they will be coded as part of a single run of zeros within the bitstream if the 8.times.8 block is scanned as a whole (FIG. 1A). However, in existing methods of frequency scalable block encoding they must be coded separately as they are each in a different coefficient sub-block. While there are only three such breaks associated with an f-scale 2 sub-block (between the coefficients within the solid-line ovals of FIG. 1B), there are seven associated with an f-scale 4 sub-block (between the coefficients within the dotted-line ovals). Each break in a run of zeros introduced by the sub-block divisions leads to increased coding overhead. While this overhead may be reduced by using separate VLC tables optimized for each frequency scale, these separate tables introduce additional complexity.

Efficient frequency scalable video decoding with coefficient selection


A focus adjustable head mounted display system used in a head mounted display device has an image capturing device for capturing environment images; an image processing unit for receiving image signals from the image capturing device and processing the received image signals; a focus adjustment unit for adjusting an input image from the image capturing device according an input focus adjustment signal so that the adjusted display image responses the focus adjustment signal; an image display unit installed at a head mounted display device for displaying the adjusted display image; a focus input unit being a manually operation device for generating a focus adjustment signal to the image processing unit; and the focus input unit providing a focus value to the focus adjustment software. A head mounted display device and a method for realizing the focus adjustable head mounted display system are also disclosed.

In U.S. Pat. No. 6,369,952, a visual display device is provided for delivering a generated image, preferably combinable with environment light, to the eye of a user. A shroud protects from stray light and holds optical elements in desired alignment. An image generator is masked by at least two masks to provide for a high quality image without waste. A removably mounted shield or activatable device and convert the apparatus from a see-through device to an immersion device and back again. The device can be mounted to the user's head while still allowing for use of conventional eyeglasses. A tracker for outputting an indication of the orientation, attitude and/or position of a head-mounted display (HMD) may be provided. The tracker can be configured so that it is incorporated in the HMD housing and/or can be easily decoupled from the HMD, so that the HMD can be used without the tracker (e.g. for watching movies).
In U.S. Pat. No. 6,611,385, a wearable display system including a display panel to display a signal processed in a predetermined way. The wearable display system includes a grating to diffract a signal output from the display panel, a waveguide to guide the propagation of a signal diffracted by the grating; and a magnifying lens to magnify the signal propagating through the waveguide and to direct the signal toward an eye of a user. The waveguide is formed by a combination of two or more substrates. According to the wearable display system, optical devices are easily and simply arranged on the waveguide to conform to specifications, and furthermore, are individually manufactured and attached to the waveguide. Therefore, the wearable display system is manufactured with minimum time and effort.
In U.S. Pat. No. 5,991,084, a compact virtual image display system is provided, which includes a microdisplay; a first magnification optic consisting of three surfaces: a display input surface; a reflective/transmissive surface, and a reflective first magnification element surface; and a second magnification optic. Light forming the source object enters the first magnification optic at the display input surface. The light travels within the first magnification optic such that it is projected to an area on the reflective backslash transmissive surface that is at least partially within the full field of view provided by the second magnification optic. The light is directed to the reflective/transmissive surface at a first angle relative to the reflective/transmissive surface such that the light is internally reflected by the reflective/transmissive surface and directed to the reflective first magnification element surface. The first magnification element surface internally reflects the light corresponding to the source object as a magnified virtual image. The magnified virtual image is then is conveyed within the first magnification optic back to the reflective/transmissive surface at a second angle of incidence relative to the reflective/transmissive surface such that the light is transmitted by the reflective/transmissive surface out of the first magnification optic. The second magnification optic is positioned to receive the magnified virtual image transmitted from the first magnification optic and transmit a compound magnified virtual image of the magnified virtual image of the source object to the observer.
In U.S. Pat. No. 6,683,584, a camera display system displays information via a matrix display element mounted within a housing that is positioned relative to at least eye of a user. The display is connected to a video or image sensor such that the user can view information or images shown on the display. The display can be mounted to a housing so that the user can move the display in and out of the user's field of view.
In U.S. Pat. No. 6,680,802, a one-eye viewing type head-mounted image display device that is compact and comfortably wearable consists mainly of a viewer and an elastic member. The viewer includes an LCD, a main prism, a see-through prism, a frame, and a microphone. The main prism conducts an image, which is displayed on the LCD, to make the image viewable with either the user's right eye or left eye. The see-through prism is bonded to the main prism, transmits extraneously light, and conducts the light to a users eye. The frame bears the LCD at a predetermined position relative to the prisms. The microphone is mounted in the frame. The elastic member includes a nose rest which supports the viewer so that the viewer will be located at a predetermined position in front of the user's eye.
However, all above mentioned prior arts only disclose optical systems or mechanic structures for displaying image to the head mounted display, but no prior art discusses or discloses any structure or mechanism about the image quality to the eyes. Many people have eye diseases, such as far-sightedness (hyperopia), nearsightedness (shortsightedness; myopia), weak sight (amblyopia), or astigmatism, which cannot see clear views for normal images. Thereby, as a normally clean image is displayed on a head mounted unit, the image is vague to the eye-diseased user. This is because it is not imaged in the focus of the user. For example, the image of a nearsighted people is focused before the retina so that the people will see a vague image. For example, nearsighted people must wear a pair of eyeglasses to adjust the image clearness to make the image is just imaged on the retina. However, this problem is also occurred for the people wearing a head mounted display since in general, the user wearing a head mounted display can not further wear a pair of glasses Thus, it is necessary that the image displayed on the head mounted display can provide images suitable for the eyes of the user. Thus it is necessary to that the images displayed on the head mount display is adjusted in advance so that as the image is incident in to the eyes it present a clear image on the retina of the user's eyes.
Moreover, a further application is that a head mounted display can be used to completely replace the function of eyeglasses, especially, for patients of weak sights. That, images are captured through a camera and then the images are processed in advance so as to display on the display screen which can present clear images to the user. Thereby, it is necessary to process the captured images in advance. However, all the prior arts cannot provide these functions to users.

Focus adjustable head mounted display system and method and device for realizing the system

Universal vision biotechnology Co., Ltd.


A stored gas inflator (10) comprising a pressure vessel (12) for storing a pressurized medium therein. The pressure vessel (12) has a wall (14) defining an interior of the vessel. A gas flow conduit (26) extends through the interior of the pressure vessel (12). The conduit (26) has a first portion extending from the interior of the vessel (12) through a first portion of the wall (14) to an exterior of the vessel, and a second portion extending from the interior of the vessel through a second portion of the wall (14) to the exterior of the vessel. Rupturable barriers (40) are formed along a portion of the conduit (26) that extends through the interior of the vessel, for separating an interior of the conduit (26) from the interior of the pressure vessel (12) prior to activation of the inflator (10). The barriers (40) are rupturable upon activation of the inflator (10) to enable fluid communication between the interior of the conduit (26) and the interior of the pressure vessel (12). This permits the pressurized inflation medium to flow from the pressure vessel (12) into the conduit (26) and out of the conduit in opposing directions into one or more associated airbag(s) or other inflatable element(s). Use of multiple gas flow paths from the inflator (10) permits a greater quantity of gas to flow relatively rapidly from the inflator (10).

Various problems are associated with inflating large inflatable curtain airbags. Several of these problems arise from an automotive industry requirement that a single inflator be used to inflate these large curtain airbags. Since the entire length of the inflatable curtain must deploy rapidly, it becomes more difficult to deploy the curtain airbag in a short time with a single inflator as the size of the vehicle (and, therefore, the volume of the curtain) increases. To accomplish the required rapid fill using a single inflator in larger curtain airbags, the inflation fluid flow rate from the inflator must increase. However, to accommodate the increased fluid flow rates from the inflator, the material of the airbag must be reinforced to prevent structural damage to the airbag.


A method and apparatus of sensing obstructions in a tubular nuclear fuel rod or the like is disclosed. A nozzle is positioned to engage one end of the fuel rod in an air tight sealed relationship. A first gas flows through the nozzle and then into and through the fuel rod. The pressure is sensed and compared with a standardized pressure to determine any excess back pressure in the nozzle indicating an obstruction present therein.

Nuclear fuel rods are manufactured from openended zirconium alloy tubular rods. Fissionable pellets are inserted into the rods which are end-plugged. The completed fuel rods are arranged in a skeletal structure containing as many as 264 fuel rods and other core component rods and control rods. This structure is placed into the reactor housing to form its core thereat.
In a nuclear reactor, the nuclear fuel contained within each fuel rod undergoes fission which increases the temperature and pressure within the rods. Any hydrogenous impurities present in the rods typically form hydrides causing the rod to leak radioactive products into the coolant. To minimize internal rod decay and hydriding during reactor operation, the interior of the rods are cleaned during their manufacture by blowing through the fuel rods felt or urethane cleaning plugs. However, during the cleaning process, a cleaning plug or portion thereof may become lodged within the rod. If visual inspection does not locate the cleaning plug before the rod is filled with fissionable pellets and then girth and seal welded, the cleaning plug is retained therein. During reactor operation, the cleaning plug will lead to hydriding causing rod leakage and subsequent contamination of the reactor coolant. Consequently, it is necessary to assure that no obstruction, such as a cleaning plug, is retained within the fuel rod before the fissionable pellets are inserted therein and the fuel rod is welded. Current visual inspection systems have been found inadequate because a cleaning plug or other obstruction can cause a partial obstruction which is difficult to detect.
It is therefore an object of this invention to provide a method and apparatus for sensing obstructions, such as a cleaning plug, in a tubular nuclear fuel rod or the like without using a visual inspection system.
It is still another object of this invention to provide a method and apparatus for sensing obstructions, such as a cleaning plug, in a tubular nuclear fuel rod or the like, which is adapted for repeatable use with many fuel rods.
It is another object of the present invention to provide a method and apparatus for sensing obstructions, such as a cleaning plug, in a tubular nuclear fuel rod or the like, where an audible alarm signal can be generated if an obstruction is present.

Method and apparatus for sensing obstructions in a nuclear fuel rod


Systems are disclosed for holding an object in mid-air under the influence of fixed and variable magnetic forces countering the gravitational pull of the object. These systems can be used for display purposes, such as advertising or commercial displays; and/or educational purposes such as spinning globes. It is perceived that the larger the gap between the suspended object and the structure containing the magnets and control systems, the more desirable the device becomes.

The current invention is a system for holding an object in mid-air under the influence of fixed and variable magnetic forces countering the gravitational pull on the object.
Such systems can be used for display purposes such as advertising or commercial displays; and/or educational purposes such as spinning globes.
It is perceived that the larger the gap between the suspended object and the structure containing the magnets and control systems, the more desirable the device becomes.
Such a systems has been disclosed in U.S. Pat. No. 6,154,353 whereby a fixed support has an upper station containing a permanent magnet, an electromagnet and a sensor system. The suspended object also has a permanent magnet and floats, below the upper station of the support frame. The permanent magnets are configured so as to attract one another in an upwards direction, countering the downwards gravitational force on the object. Hence a theoretical balance point is defined whereby in the absence of any external influences or fluctuations in the magnetic and gravitational forces, the object would be held steady in mid-air.
In fact, such a balance point is virtually impossible to maintain and so control systems are applied, disclosed for example in DE 4210741, whereby fluctuations in the field provided by the permanent magnet in the object, are interpreted, and consequently the current to the electromagnet in the support frame is adjusted to provide an attractive or repelling force in order to prevent the object moving away from the balance point.
U.S. Pat. No. 6,154,353 discloses such a system modified by the fact that the permanent magnets provide an attractive upwards force slightly greater than the downwards force on the object due to gravity. In this case the electromagnet is normally employed to provide a small repelling force to provide a fine balance and establish what might be called a dynamic balance point.
In the dynamic balance point the object is balanced in mid air by an upward force provided by the attraction of the permanent magnets countered by the forces of gravity plus the repelling force of the electromagnet acting on the permanent magnet in the object.
If the object moves away from the dynamic balance point, stationary sensors detect the change in the field caused by the positional variation of the permanent magnet in the object. If the field rises above a predetermined level the current to the electromagnet is increased and the repelling force consequently increases to push the object downwards. By extension, if the field falls below a certain value the current in the electromagnet is decreased such that the repelling force is reduced and the object is pulled upwards.
The advantages of this system are that relatively small amounts of power are needed to achieve the fine balancing provided by the electromagnet. Furthermore if the power fails the object will move upwards towards the frame rather than downwards. However, the gap between the object and the structure is less than is theoretically possible.


Disclosed is an electrolyte for an electrolytic capacitor which comprises a salt of a tertiary dicarboxylic acid represented by the following formula (I) or (II): ##STR1## wherein n represents an integer of 1 to 5, and R.sup.1 to R.sup.4 each represents an alkyl group having 4 or less carbon atoms, ##STR2## wherein n has the same meaning as defined above, l and m each represents an integer of 4 or 5, and R.sup.5 and R.sup.6 each represents hydrogen atom, methyl group or ethyl group,. and an electrolytic capacitor using the same.

This invention relates to an electrolyte for an electrolytic capacitor and an electrolytic capacitor using the same.
An electrolytic capacitor uses a so-called valve metal anode such as as aluminum and tantalum, on which an insulating oxide film is formed by anodic oxidation as a dielectric material. The electrolytic capacitor can be formed by placing a cathode opposed to the anode, interposing a separator between two electrodes and making retained an electrolyte to the separator.
Since the anode is subjected to etching treatment to enhance the surface area, the electrolyte functions as a true cathode by contacting with the concave and convex surface. Electric conductivity and temperature characteristics of the electrolyte become main factors to determine the electric characteristics of an electrolytic capacitor. Also, the electrolyte repairs damage of an oxide film whereby it affects to leakage current and lifetime of the capacitor. Thus, the electrolyte is the most important constitutional element which controls the characteristics of the electrolytic capacitor.
In the prior art, as an electrolyte for an electrolytic capacitor, particularly for a medium or high voltage, so-called ethylene glycol-boric acid type electrolyte has been used. This kind of the electrolyte forms water when heating by esterification reaction of ethylene glycol and boric acid. Therefore, there is a disadvantage that it cannot be used at a high temperature exceeding 100.degree. C. since inner pressure is too heightened.
In order to overcome such a disadvantage, azelaic acid, sebacic acid, decanedicarboxylic acid or a salt of these acids has been used, but these materials are poor in solubility to a solvent such as ethylene glycol and also insufficient in thermal stability.
In Japanese Laid-Open Patent Application No. 116815/1986, there has been proposed the method for improving solubility and thermal stability by using a tertiary monocarboxylic acid, but anodic film forming ability is insufficient. In Japanese Laid-Open Patent Application No. 103821/1989, it has been proposed to use a tertiary dicarboxylic acid, but the compound contains ester bonds, which are subjected to scission, and results in the deterioration of the electrolyte.

Electrolyte for electrolytic capacitor and electrolytic capacitor using the same


A continuously cast strand is cut into elongated billets having ends and the billets are run through a rolling stand. after cutting the strand into billets and before rolling the billets one of the billets is engaged in the rolling stand and a trailing end of the one billet and a leading end of another billet are enclosed in a mold with the ends longitudinally spaced. This space between the ends is filled with molten metal in contact with the ends of the billets and the molten metal is hardened to interconnect the billet ends. Then the mold is removed from around the billet ends. The molten metal is of substantially the same composition as the billets. Furthermore the one billet is advanced in a travel direction by means of the stand and the mold and the other billet are advanced synchronously with the one billet after enclosing the billet ends in the mold. The mold is removed from the billet ends before the hardened metal between the billet ends enters the rolling stand.

In the production of bars, for instance steel rein-forcement bars, it is standard to continuously cast a metal strand, cut it into relatively long billets, roll the billets into bars of the desired sectional shape, and finally to cut the bars into the desired trade lengths. The strand is cut into billets because it is virtually impossible to deal with the extremely long strand as it exits the continuous-casting apparatus. Normally also the rolling mill is not located close enough to receive the continuously cast strand directly and in any case the low speed of the rolling mill cannot match the outlet speed of the strand from the continuous caster.
The billets are normally of a standardized length that is in turn a multiple of a desired finish trade length, corrected of course for the length increase encountered with rolling, but the last billet produced from a continuously cast strand is invariably shorter than this desired trade length. This short piece creates a problem that is dealt with, for instance, in the system of German patent document 3,636,785 by cutting it to a length equal to a multiple of the desired finish length before further treatment. Although such a procedure is a substantial improvement on the procedure of simply manually culling out and recycling the overshort piece it is relatively complex and requires special equipment.

Method and apparatus for connecting billets


A lighting apparatus comprises a plurality of light modules; each module comprises: a hollow body provided with a light box having a light exit opening and housing a LED light source controlled by a control unit; a diffusing screen positioned on the opening to uniform the light passing through the opening; a closure cover, positioned above the diffusing screen; a transparent capacitive film positioned on a face of the closure cover and connected to the control unit to define a touch control device of the module; the modules are shaped as respective polyhedral sectors arranged around the first axis and each module defines an independent light module controlled by the respective touch control device independently of the other modules.

In the lighting industry, particularly the interior lighting industry, a large number of different types of lighting apparatuses are known, which can also provide a multiplicity of functions and lighting effects.
A common requirement is to change the luminosity or light intensity.
However, the known apparatuses may not be fully satisfactory, in particular with regard to simplicity and luminosity control efficiency.
On the other hand, in the lighting industry there is a constant search for technical solutions, which also allow them to be integrated into aesthetically original objects and further allow newly-designed lighting effects to be obtained, in which field, in addition to the purely functional aspect, also the aesthetic and emotional component has a key role.


A successive type constant temperature valve core with single handle comprises a valve cover, a temperature adjusting assembly, a thermo sensitive element and a control assembly for hot and cold inlet water, combining in the chamber of the valve cover from top to bottom, wherein, the control assembly for hot and cold water inlet comprises a holder of the thermo sensitive element, an adjuster, a put-off spring, a buffer spring and a holding piece. The upper part of the holder of the thermo sensitive element props the thermo sensitive element, and the lower part extends from the lower end of the valve cover; the buffer spring is arranged outside the holder of the thermo sensitive element, and the two ends respectively prop the holder of the thermo sensitive element and the adjuster; the adjuster is axial adjustably restricted to the periphery of the lower part of the holder of the thermo sensitive element by matching the buffer spring with the holding piece; the put-off spring is arranged outside the buffer spring, and the two ends are respectively prop the holder of the thermo sensitive element and the valve cover; the top and foot of the adjuster respectively forms cold water inlet and hot water inlet; water outlet is arranged on the wall of the valve cover; the holder of the thermo sensitive element is provided with a mixed water passage that communicates with the cold water inlet, the hot water inlet and the water outlet.

The traditional valve core with single handle does not own the function of constant temperature, and the single handle generally is taken as flow control or flow switch. Under the condition of variable temperature and pressure of supply water, the outlet water may be sometimes hot and sometimes cold, which will bring inconvenience to people.
With the advancement of science and technology and the improvement of living standard, the function of constant temperature will be gradually used in the traditional valve core. The valve cores with the function of constant temperature have been widely used in each kind of water supply system for bath in household and hotel, etc. The users can adjust the temperature of outlet water according to actual demands by themselves, and after presetting temperature, the mixed outlet water temperature will be constant; consequently, the problem of sometimes hot and sometimes cold water caused by change of inlet water pressure and unstable temperature by a common valve core can be solved, and the valve core is safe and prevent user's scald.
The utility model with authorized publication patent number of CN2665478 Y discloses a constant-temperature ceramic valve core with single handle, which contains a valve handle, a body of the valve core, a valve cover, a seal ring, a fixed ceramic chip, a movable ceramic chip, an adjuster and a temperature sensor; wherein, the body of the valve core is provided with a cold water inlet, a hot water inlet and a mixed water outlet chamber; the temperature sensor is arranged in the mixed water outlet chamber; the adjuster is connected with the top of the temperature sensor; the lower end of the temperature sensor is provided with a put-off spring. Turning the valve handle up and down to control the movable ceramic chip, so as to switch on and off or regulate the water; turning the valve handle left and right can regulate the proportion of cold and hot water; consequently, the temperature of the mixed outlet water can always be kept at the presetting water temperature. The patent technology has more complicated internal structure and unstable quality; consequently, the inner water passage can be restricted on a certain extent, and small-size valve core is difficult to be made, as small volume valve core has the defect of deficient flow rate.
Besides, the users only use the function of flow switch and pay less attention to the adjustment of flow rate in the actual application.

Successive type constant-temperature valve core with single handle

HongWan Industrial Zone Xiangzhou, Zhuhai

Suprema (Zhuhai J/V) Thermostatic Sanitaryware Co., Ltd.


The monohydrate of 5-(2-(4-(1,2-benzisothiazol-3-yl)-1-piperazinyl)ethyl)-6-chloro-1,3-dihydr o-2H-indole-2-one hydrochloride has advantageous stability for formulation as a neuroleptic agent.

The invention is directed to a novel monohydrate of 5-(2-(4-(1,2-benzisothiazol-3-yl)-1-piperazinyl)ethyl)-6-chloro-1,3-dihydr o-2H-indol-2-one hydrochloride, a pharmaceutical composition containing said monohydrate and a method of administering said monohydrate to treat neuroleptic diseases.
U.S. Pat. No. 4,831,031 which is incorporated herein by reference, discloses 5-(2-(4-(1,2-benzisothiazol-3-yl)-piperazinyl)ethyl)-6-chloro-1, 3-dihydro-2H-indol-2-one hydrochloride of the formula ##STR1## wherein Ar is benzisothiazol-3-yl, in the hemihydrate form (hereafter "the hemihydrate"), having neuroleptic activity.


In a digital network system, such as ISDN (Integrated Service Digital Network) system, a data link is established between transmit-side and receive-side stations so that a data transfer is performed onto a public telephone line in accordance with a predetermined protocol. The transmit-side station compresses data read from a storage medium and then transfers compressed data to the receive-side station, while the receive-side station expands the compressed data and then writes it into a storage medium. Before transferring the compressed data, the transmit-side station transmits a data transfer request to the receive-side station, so that if the receive-side station is now ready to receive the compressed data, the transmit-side station transfers the compressed data to the receive-side station. On the other hand, when completing a data transfer, the transmit-side station transmits an end request of data transfer to the receive-side station, so that if the receive-side station is now in a state to respond to a data transfer completion, the data link formed between the transmit-side and receive-side stations is terminated. Herein, the whole storage area of the storage medium is divided into plural storage blocks, so that the data transfer is performed with respect to each storage block. Preferably, the storage medium is a floppy disk, so that each storage block corresponds to each track formed on the floppy disk.

The present invention relates to a data transfer method by which digital information stored in a storage medium is transferred to a remote place via a digital network.
According to an example of the conventional data transfer method by which digital information is transferred on a public line to a remote place, each of the transmit-side and receive-side provides a modulator-demodulator (i.e., MODEM). Herein, MODEM at the transmit-side converts the digital information into an analog signal, which is then transmitted toward to the receive-side. Then, a MODEM at the receive-side decodes the analog signal into the digital information.
Meanwhile, in the above-mentioned data transfer method wherein the digital information is transferred in the form of the analog signal, it takes a very long time to transfer much information stored in a storage medium such as a floppy disk. For this reason, there is provided another data transfer method in which the digital information is transferred in the form of a digital signal. However, there is no data transfer method which is optimum to the public network system, i.e., so-called "ISDN" (Integrated Service Digital Network).


A standing chip scale package is disclosed. The standing chip scale package provides electrical connection to bumped device contacts on both sides of the chip. The package is coupleable to a printed circuit board in a standing configuration such that front and back sides of the bumped chip are substantially perpendicular to a mounting surface. A process of fabricating the standing chip scale package is also disclosed.

1. Field of the Invention
The present invention generally relates to a semiconductor package and more particularly to a standing chip scale package.
2. Description of Related Art
The miniaturization of electronic devices has led to the design and manufacture of increasingly smaller semiconductor devices. Semiconductor devices are generally packaged for electrical connection to traces of a printed circuit board. Chip scale packages provide a package on the scale of the semiconductor device to minimize board space consumed by the package.
Vertical conduction power semiconductor devices such as MOSFETs generally have two electrodes or contacts formed on a first surface of the device and a third electrode or contact formed on a second surface of the device. In order to electrically connect the electrodes to the printed circuit board, some conventional chip scale packages provide a means by which all the electrodes are disposed on the same side of the device. For example, U.S. Pat. No. 6,646,329 discloses a package including a leadframe and a die coupled thereto. The die is coupled to the leadframe such that its back surface (drain contact) is coplanar with source leads and a gate lead extending from the leadframe. The disclosed structure is disadvantageously complex.
Another prior art chip scale package includes a die mounted drain side down in a metal clip or can with the source and gate electrodes disposed coplanar with the rim surface of an extended portion of the clip or can as disclosed in U.S. Pat. No. 6,767,820. The disclosed package makes it difficult to visually check solder joints after the package is mounted onto a circuit board.
A flip-chip MOSFET structure disclosed in U.S. Pat. No. 6,653,740 has a vertical conduction semiconductor die in which the lower (drain) layer of the die is connected to a drain electrode on the top of the die by a diffusion sinker or conductive electrode. The disclosed structure suffers the problem of increased resistance and a reduced active area.
It is also known to electrically connect the device electrodes with the printed circuit board by means of conductive blocks or layers. One such structure is disclosed in U.S. Pat. No. 6,392,305 wherein the electrodes of the chip are electrically connected to conductive blocks that in turn are connected to the printed circuit board through side surfaces thereof. U.S. Pat. No. 6,841,416 discloses a chip scale package having upper and lower conductive layers connected to the terminals of the chip. Electrode surfaces formed on the same side surfaces of the upper and lower conductive layers are connected to corresponding connection pads of the printed circuit board. The disclosed structures are overly complex and/or the fabrication process is too complicated and/of inefficient for low cost production.
There remains a need in the art for a chip scale package that provides electrical connection to device contacts on both sides of the chip, a clear view of solder joints, and a reduced printed circuit board mounting area. Preferably the process of fabricating the chip scale package permits batch handling. Further, the chip scale package can preferably be made using simple manufacturing steps and at low cost.

Alpha and Omega Semiconductor Incorporation


A current diverter strip is provided having a dielectric (22) located above a plurality of conductive segments (24). An insulator (30) is also provided among said conductive segments (24) and below said dielectric (22). When RF transparency is required, the conductive segments (24) can have a maximum dimension that is approximately ⅙th of a wavelength of the highest operating frequency of an antenna that may be communicating through the current diverter strip. The dielectric (22) may be colored to match the color of the structure to which it is implemented. Upon exposure to a strong electric field, the current diverter strip (20) forms an ionized channel above the dielectric (22). In various implementations, the current diverter strip may be radio frequency transparent, environmentally and chemically resistant, color matched to its surroundings, and/or can withstand repeated uses.

Arcing current, such as a lightning strike, can attach to conductive objects near or contained within non-conductive enclosures. For example, lightning has penetrated nose radomes on aircraft and forced lightning currents in excess of 200,000 amperes into the antennas and other sensitive electronics underneath the nose radomes. Such lightning strikes cause considerable degradation of the radome structure and extensive damage to the underlying antenna and sensitive electronics.
Lightning diverter strips have been devised in the past to prevent lightning puncture of radomes. These lightning diverter strips provide an alternate electrically conductive path for the lightning current. Typically, the lightning diverter strip is applied over the outer surface of the radome with one end of each lightning diverter strip electrically grounded to the conductive airplane structure.
There are three main forms of lightning diverter strips. One form is the continuous metal conductor, which includes metal bars and foils. Another form is the segmented diverter strip which is comprised of closely spaced metal segments that have been applied to a flexible strip material. The third form of lightning diverter strip applies finely powdered aluminum to a non-conductive substrate using a flexible epoxy such that the strip will have a very high DC resistance but will conduct lightning current.
The three main conventional diverter strip forms have one or more of the following disadvantages. The lightning diverter strip may have a detrimental impact on the underlying antenna's radio frequency performance. The lightning diverter strip may be damaged during a lightning strike, thereby reducing its lightning strike diversion ability for subsequent lightning strikes. The lightning diverter strip may be susceptible to weather erosion which reduces the lightning diversion effectiveness of the strip, or the lightning diverter strip may be visible on the radome surface which detracts from the aesthetics of the radome.


Systems and methods automatically determine responses to intention-focused content based on semantic analysis, natural language analysis, token analysis, social network analysis and influence ratings. The systems and methods identify relevant queries for product support, purchase or advocacy from multiple communications channels and further separate the high-value conversations and individuals from the low value conversations and individuals in an efficient manner. Described herein is a system and method to use the identification of important individuals and the context of their conversations to appropriately route content items and messages and subsequent responses in such a way as to allow an efficient interaction to occur.

The proliferation of social interactions on the internet has introduced numerous opportunities to offer insights into people's interests and activities. A recent set of social applications or features has provided the next step beyond status updates, product or interest ratings and social sharing networks; the ability to describe future intentions of behaviors or activities offers a unique view into the explicit statements someone makes that can then be leveraged by others into offering support to that stated intention.
A technology analyst in the social media space, Jeremiah Owyang, has produced a taxonomy that describes where this intention space lies available at the URL (Uniform Resource Locator) www.web-strategist.com/blog/2009/12/04/when-real-time-is-not-fast-enough-the-intent-based-web/. Owyang lists the "Intention Web" as "Information that provides explicit predictions of who will do what next, although it's not happened yet." Examples include Upcoming.org, Facebook events, Plancast. Further examples include Tweetmeme, Topsy, Sency, and OneRiot. Owyang further explains the opportunities in this area as:                People can connect to each other, improving experience. Businesses can provide a more contextualized experience for customers or prospects using Social CRM
Owyang recognizes the complexity of the problem he describes by stating the challenges:                Explicit intentions may not be true, the future is always uncertain. Companies can barely keep up with real time web—let alone predict the future.
Brian Solis takes Jeremiah's concept and extends it, providing a description at the URL: www.briansolis.com/2010/01/the-predictive-web which states:                Suddenly the predictive Web comes into focus. The innovation that materializes into products and platforms creates an ecosystem that wires the individual human algorithm to the technology that will work on our behalf to mine and present data, content, products, people and companies that match what interests us based on who we are—not solely derived from what we have in common. Just because we viewed a common item, purchased a product or service based on our click patterns or share contacts within networks, doesn't imply, nor does it guarantee, that we share interests, ideas, and ambitions. Therefore, the ability to predict is only as accurate as the technology that focuses on who we are defined by all we do.
Importantly, neither Owang nor Solis offer suggestions for how to make use of the intention data provided in this social medium, nor do they suggest how to interpret the quality of the intent while they specifically caution about the potential problems of intent quality.

Identifying individual intentions and determining responses to individual intentions


An expansion joint system for roadway constructions is provided incorporating dampers that are designed to protect the roadway constructions from the effects of disturbances caused by seismic events and vehicular traffic by absorbing and dissipating mechanical vibration energy.

The invention relates to an expansion joint system incorporating damping means, which may be utilized in various roadway constructions where gaps are present between adjacent concrete sections of the roadway construction. The expansion joint including damping means is useful in roadway constructions, including, for example, bridge constructions and other roadway structures where absorption and dissipation of mechanical vibrations is desired.
In a roadway construction, such as highways and bridges, a gap is intentionally provided between adjacent concrete structures for accommodating dimensional changes within the gap occurring as expansion and contraction due to temperature changes, shortening and creep caused by prestressing of the concrete, seismic disturbances, and deflections and longitudinal forces caused by vehicular traffic. An expansion joint is typically utilized to accommodate these movements in the vicinity of the gap.
Bridge constructions are especially subject to dimensional changes and movement caused by seismic events and vehicular traffic. This raises particular problems, because the movements occurring during such seismic events are not predictable either with respect to the magnitude of the movements or to the direction of the movements. In many instances, bridges have become unusable for significant periods of time, due to the fact that traffic cannot travel across damaged expansion joints.
Damping is the absorption of mechanical energy by a material in contact with the source of that energy. It is desirable that the damping materials be highly effective in converting this mechanical energy into heat energy rather than transmitting it to the surroundings.
The use of viscous dampers as "anti-seismic devices" to dampen vibrations caused by seismic cycling and vehicular traffic in bridge construction is known. Viscous dampers typically provide damping by forcing a piston rod into a housing containing a viscous material, such as an oil. The mechanical vibration energy exerted on the bridge structure is decreased when the piston rod pushes through the viscous fluid, as the mechanical energy is converted to heat energy. Thus, damping is achieved. These viscous dampers are often installed across an expansion joint, but are not incorporated into the expansion joint system itself.
Heretofore, the art has not disclosed an expansion joint system having damping means incorporated therein. Therefore, a need still exists for an improved expansion joint system that can absorb and dissipate vibration energy that may be caused by seismic events and vehicular traffic, occurring in the vicinity of a gap having an expansion joint installed between two spaced apart, adjacent roadway sections.

Expansion joint system including damping means


An apparatus which makes dark lines due to a central axis of a cross dichroic prism sufficiently inconspicuous. In a second lens array, minute lenses arranged on the same column include three different types of minute lenses having optical axes at different positions. Each row of the minute lenses consists of one of the three types of minute lenses. Partial light fluxes respectively passing through the minute lenses have optical axes at different positions relative to a center of a lighting area of a liquid-crystal light bulb, so as to illuminate different illumination areas.

1. Field of the Invention
The present invention relates to a projection display apparatus with colored light combining means and a lighting optical system therefor.
2. Discussion of the Background
A cross dichroic prism is often used for projection display apparatus that project a color image on a projection screen. For example, in a transmissive liquid-crystal projector, the cross dichroic prism is utilized as colored light combining means that combines three colored rays of red, green, and blue and emits the composite light in a common direction. In a reflective liquid-crystal projector, the cross dichroic prism is utilized as colored light separation means that separated a beam of white light into three colored rays of red, green, and blue and also as colored light combining means that recombines modulated three colored rays and emits the composite light in a common direction. A known example of the projection display apparatus with the cross dichroic prism is disclosed in JAPANESE PATENT LAID-OPEN GAZETTE No. 1-302385.
FIG. 17 conceptually illustrates a main part of a projection display apparatus. The projection display apparatus includes three liquid-crystal light valves 42, 44, and 46, a cross dichroic prism 48, and a projection lens system 50. The cross dichroic prism 48 combines three colored rays of red, green, and blue modulated by the three liquid-crystal light valves 42, 44, and 46 light and emits the composite light toward the projection lens system 50. The projection lens system 50 focuses the composite light on a projection screen 52.
FIG. 18 is a partly decomposed perspective view illustrating the cross dichroic prism 48. The cross dichroic prism 48 includes four right-angle prisms which are bonded to one another via the respective right-angle surfaces by an optical adhesive.
FIG. 19 shows a problem arising in the case of utilizing the cross dichroic prism 48. As shown in FIG. 19(A), the cross dichroic prism 48 has a red light reflection film 60R and a blue light reflection film 60B which are arranged in a substantially X shape on an X-shaped interface formed by the right-angle surfaces of the four right-angle prisms. There is an X-shaped layer of optical adhesive 62 formed in the gaps between the four right-angle prisms. Both the reflection films 60R and 60B accordingly have gaps at a central axis 48a of the cross dichroic prism 48.
When a light beam passing through the central axis 48a of the cross dichroic prism 48 is projected on the projection screen 52, a dark line due to the central axis 48a may be formed in the projected image. FIG. 19(B) shows an example of the dark line DL. The dark line DL represents a relatively dark, linear area having a different color from that of the other part and is formed substantially on the center of the projected image. It is considered that the dark line DL is ascribed to scattering of rays and no-reflection of the red light and blue light in the gaps of the reflection films in the vicinity of the central axis 48a. A similar problem arises in a cross dichroic mirror that includes two dichroic mirrors that are arranged in an X shape and respectively have selective reflection films, such as a red reflection film and a blue reflection film. In this case, a dark line due to a central axis of the mirror is formed in a projected image.
As described above, in the prior-art projection display apparatus, a dark line is formed substantially on the center of a projected image because of the central axis of the cross dichroic prism 48 or the cross dichroic mirror.

Projection display and illuminating optical system for it


A chemical vapor trap for selectively removing harmful corrosive contaminants, such as water and acetic acid vapors, from an evacuating vapor phase in a vacuum drying system is provided. The chemical vapor trap includes a condenser section effective to convert a high temperature incoming heated sample liquids and heated vapor phase into a liquid phase condensate and a relatively lower room temperature stripped vapor phase. Liquid condensate including water and acetic acid are trapped below a chemical blanket or sealing layer which prevents re-vaporization or boiling of removed corrosive volatile contaminants from the vapor phase entering the vacuum pumps, promoting improved pump performance and extend pump service life.

The present invention generally relates to apparatus and methods for drying samples under conditions of elevated temperature and reduced pressure. More particularly, it relates to a new and improved chemical vapor trap for use in a vacuum drying system which is effective to selectively remove water, acetic acid and other materials known to be harmful to vacuum pump operation and service life by isolating these materials from the drying vapor phase and blanketing them under a chemical blanket to prevent their undesired revaporization during the remainder of the sample drying operation.
Vacuum drying instruments are presently known and used for various scientific purposes. Illustrative examples include gel dryers, specimen dryers, rotary evaporators, vacuum centrifuges and filtration manifolds. The sample may be a biological specimen or fluid or it may be a treated substrate material to be used in subsequent analytical determinations. The samples generally contain a solvent portion or fraction to be removed which typically includes water, acids, organic liquids and other solvents. The solvents are removed in these devices by applying heat and vacuum to a drying chamber containing the samples. The liquid and vapor forms of most of these solvents are known to be deleterious to the vacuum pumps used for creating a partial vacuum in the drying chambers.
More particularly, oil sealed rotary vane vacuum pumps are used to create a vacuum in a sample chamber. Oil sealed rotary vane vacuum pumps are preferred because of the good pumping speeds and rapid and efficient ability to dry a sample. A major drawback previously associated with rotary vane pumps is that heated water vapor and acetic acid condense in the pump in the oil case resulting in an acetic acid, water and oil emulsion. In rotary pumps wherein the lubricating oil is fed from the oil case, the water settles at the bottom of the pump case. At start up, instead of receiving oil lubricant, the pump sees acidified water which is non-lubricating when the condensed solution reaches the oil feed hole. Often what happens is that after start up, the pumps actually freeze up from lack of lubricant. Efforts to prevent entry of heated liquids into the pump or condensation of heated acidified water in the pump have included placing a liquid trap in line before the vacuum pump to trap and remove liquid phase materials evolving from the heated sample. The liquid traps are generally effective to prevent large amounts of liquids from traveling directly from the sample to the pump, however, a liquid trap cannot prevent vapor phase contaminants such as acetic acid and water vapor from entering the pump. Moreover, at lower pressures the trapped liquids may volatilize and add to the corrosive vapor load feeding to the pump which is undesirable.
Prior attempts to reduce or eliminate vapor phase corrosive contaminants have included placing a cold trap between the liquid trap and the vacuum pump to cause water and acetic acid to condense out of the vapor phase feed to the vacuum pump. The vapor phase load at the beginning of a drying cycle is often too large for the condenser capacity so that contaminated vapors still reach the pump in an undesirably high concentration. Moreover, solvent flashing and fly-by can occur in the cold trap permitting hot corrosive vapors also to exit the cold trap in a high concentration. Furthermore, cold traps are maintenance intensive requiring setup for each drying session and the cost of refrigerants is an undesirable extra expense.
In view of the problems associated with premature failures and problematic maintenance of oil sealed rotary vane pumps, a compromise has been made by employing lower speed, less efficient diaphragm vacuum pumps, because they are generally more resistant to vapor phase composition. Liquid phase contaminants carried over into a diaphragm vacuum pump or condensed from vapor phase materials in the pump itself cause damage to the diaphragms and premature failure of the pumps. In the past, diaphragm pumps were believed to provide an agreeable alternative to rotary vane vacuum pumps because the need for a cold trap could be dispensed with. A liquid trap is generally used to collect liquid phase contaminants. At lower system pressures achieved by vacuum pump evacuation, the liquid in the trap revaporizes into the vapor phase which may condense in the pump and cause premature diaphragm failure. Often people have suggested the use of a cold trap in a diaphragm pump system which represents an unacceptable compromise because the maintenance issues concerning the cold trap are not avoided and the pump has a slower pumping rate leading to slow, i.e. unacceptably long, drying times.
Other efforts to alleviate or avoid solvent contamination of the vacuum pumping devices in drying systems, have included the suggestions made in U.S. Pat. No. 5,137,604 and U.S. Pat. No. 5,025,571. In the first of these patents, a cold trap is employed in connection with an elaborate switching device for opening the cold trap and sample chamber to vacuum in discrete episodes. This proposed improvement incrementally passes evolving vapor phase materials through the cold trap to increase the residence time of the vapor phase in the condenser to more effectively remove the corrosive contaminants from the vapor phase prior to entry into the pump. The vapor phase and liquid phase spill over from most samples is so high at the beginning stages of the drying cycle that incomplete condensation is the norm, so that contaminants still reach the pump and can condense therein and cause damage. More importantly, the drying times of the samples are undesirably long and cold trap maintenance is not avoided.
In U.S. Pat. No. 5,025,571, another method of preventing liquid egress comprises collecting liquids and condensed vapors in a heated liquid trap which effectively revaporizes all evolving solvent to heated vapor phase form before entering the diaphragm pump. Pre-heating still does not and cannot prevent the undesirable condensation of harmful corrosive liquids within the pump itself which is a disadvantage, particularly in view of the compromise already made in terms of pumping speed and drying times for these diaphragm pump systems.
Accordingly, to overcome the disadvantages of prior art vacuum drying systems, it is an object of the present invention to provide a new and improved chemical vapor trap which is generally effective to selectively substantially remove water and/or acetic acid contaminants from a vapor phase in a vacuum drying system, regardless of vacuum source, to prevent these corrosive materials from entering the vacuum pump.
It is another object of the present invention to provide a new and improved chemical vapor trap which is effective to selectively remove water and acetic acid from an evolving vapor phase in a vacuum drying system by condensing these materials into a liquid phase condensate and isolating the condensate from the vacuum system in a manner which prevents re-vaporization and reintroduction of the corrosive acid and water materials into the vapor phase being fed to the vacuum pump.
It is another object of the present invention to provide a new and improved vacuum drying system for drying samples which is faster, and more efficient, at drying sample materials in a relatively maintenance-free manner as compared to prior art vacuum drying systems.

Chemical vapor trap and vacuum drying system including same


A new and distinct cultivar of Kalanchoe plant named ‘Kelly’, characterized by its upright, uniform and moderately vigorous growth habit; dark green-colored leaves; uniform, freely and early flowering habit; large double dark orange and light orange bi-colored flowers; and excellent postproduction longevity.

The present invention relates to a new and distinct cultivar of Kalanchoe, botanically known as Kalanchoe blossfeldiana, and hereinafter referred to by the name 'Kelly'.
The new Kalanchoe is a product of a planned breeding program conducted by the Inventor in Hinnerup, Denmark. The objective of the breeding program is to create new double-flowered Kalanchoe cultivars with attractive foliage and flower coloration.
The new Kalanchoe originated from a self-pollination made by the Inventor in Hinnerup, Denmark in September 2003, of a proprietary Kalanchoe blossfeldiana selection identified as code number KJ 2003 0564, not patented. The cultivar Kelly was discovered and selected by the Inventor as a flowering plant from within the progeny of the stated self-pollination in a controlled environment in Hinnerup, Denmark in May, 2004.
Asexual reproduction of the new Kalanchoe by vegetative terminal cuttings in a controlled environment in Hinnerup, Denmark since July, 2004, has shown that the unique features of this new Kalanchoe are stable and reproduced true to type in successive generations.


The present invention relates to a combined semiconductor gas sensor, this sensor is constituted by combining two portions, each of the portions is made of a different gas sensitive material, their resistance exhibit different variation with the variation of the density of a specific gas, a detecting signal is led out from the junction of the two portion. Because of the mutual compensation and propagation effect of the two portions of the above mentioned gas sensor, the stability and/or sensitivity as well as the stability to temperature and humidity and the initial relaxation time can be improved. Gas sensors of different characteristics can be obtained by different combinations of two different gas sensitive materials selected according to need.

The present invention relates to a semiconductor gas sensor, and particularly to a combined semiconductor gas sensor constituted by two different gas sensitive materials, which has high sensitivity and preferable selectivity, thermo-stability and anti-humidity capability.
Recently, semiconductor gas sensors have become one of the most rapidly developed and widely used gas sensors for their advantages of relatively high sensitivity, uncomplicated manufacturing techniques, convenient and flexible usage, etc. More and more types of semiconductor gas sensors have also been developed, the kinds of gases that can be detected have been increasing rapidly, from the detection of flammable and explosive gas to the detection of poisonous gases, fragrance, stink, as well as freshness. Some of the gases used in producing of semiconductors and integrated circuits are of severe poison, the density to be detected is in the range of 1-100 ppm, and sometimes even in the magnitude of ppb's. In view of poisoning preventing and personal safety, it is also required to be extended to the detection of low density ones in many occasions. For example, for preventing slow poisoning, the allowable average density of H.sub.2 S for eight-hour working is 15 ppm, and 150 ppm for CO; for preventing acute poisoning, the allowable density for fifteen-minute exposure to H.sub.2 S is 100 ppm, and to CO is 400 ppm. The existing gas sensors can hardly satisfy this measuring requirement.
As for methods for improving the sensitivity of semiconductor gas sensors, the recently adopted methods include:
1. adding catalyst to improve the activity of gas sensitive materials; PA1 2. super-parculate of the material; PA1 3. searching for new materials with desirable sensitivity. PA1 (1) where .beta..sub.A >.beta..sub.B, V.sub.T '>V.sub.T and output voltage increases; PA1 (2) where .beta..sub.A =.beta..sub.B, V.sub.T '=V.sub.T and output voltage remains unchanged; PA1 (3) where .beta..sub.A <.beta..sub.B, V.sub.T '<V.sub.T and output voltage decreases. PA1 1. In condition R.sub.A >>R.sub.B PA1 .beta.=.beta..sub.A .beta..sub.B, noticing that we have .beta..sub.A >1 and .beta..sub.B >1 for A being N-type and B being P-type material, therefore .beta.>.beta..sub.A or .beta..sub.B. PA1 (i) 1+.gamma..sub.A .DELTA.T=1+.gamma..sub.B .DELTA.T, i.e., .gamma..sub.A =.gamma..sub.B. PA1 (ii).gamma..sub.A .DELTA.T<<1, .gamma..sub.B .DELTA.T<<1 PA1 (i) where .DELTA.T>0 PA1 where .vertline..gamma..sub.A .vertline.>.vertline..gamma..sub.B .vertline., ##EQU22## is more approaching 1 than 1+.gamma..sub.1 .DELTA.T (provided that .gamma..sub.1 =.gamma..sub.A); PA1 where .vertline..gamma..sub.A .vertline.=.vertline..gamma..sub.B .vertline., ##EQU23## is more approaching 1 than 1+.gamma..sub.1 .DELTA.T; where .vertline..gamma..sub.A .vertline.<.vertline..gamma..sub.B .vertline., it is indefinite. PA1 (ii) where .DELTA.T<0, we have: EQU 1+.gamma..sub.A .DELTA.T>1 and 1+.gamma..sub.B .DELTA.T>1 PA1 where .vertline..gamma..sub.A .vertline.>.vertline..gamma..sub.B .vertline., ##EQU24## is more approaching 1 than 1+.gamma..sub.1 .DELTA.T; where .vertline..gamma..sub.A .vertline.=.vertline..gamma..sub.B .vertline., ##EQU25## is more approaching 1 than 1+.gamma..sub.1 .DELTA.T; where .vertline..gamma..sub.A .vertline.<.vertline..gamma..sub.B .vertline., it is indefinite. PA1 where .tau..sub.A >.tau..sub.B, V.sub.T '<V.sub.T, slow response. PA1 where .zeta.>1, i.e., .tau..sub.A <.tau..sub.B, then V.sub.TS <V.sub.T ', quick recovery; PA1 where .zeta.<1, i.e., .tau..sub.A >.tau..sub.B, then V.sub.TS >V.sub.T ', slow recovery.
However, the improvement of sensitivity of gas sensors by the use of such methods is of certain limitation, detections of ppb level can hardly be realized by the sensors manufactured by these methods.
Furthermore, the existing gas sensors are of simple structures constituted by doping a gas sensitive substrate material with characteristic-improving dopant, the selecting characteristic of which is not good enough and the stability is poor. In order to improve the stability in application, a thermosensitive resistor is usually connected externally for compensation, and sometimes, the gas sensitive detecting head is combined with the temperature compensating element. Since the above-mentioned temperature compensating element is a thermosensitive resistor, it can only be used for temperature compensating but not for humidity compensating, without any contribution to the improvement of the selectivity of the gas sensor, and any improving effect to the sensitivity and initial relaxation time of the sensor.


An ink jet image receptor element having a protective coating is disclosed. The protective coating is a single protective layer that contains a fluoropolymer and an acrylic polymer. Because the protective coating is resistant to surface pitting, dirt, stains, and general degradation, images formed from the element can be used effectively on billboards, banners, posters, and other outdoor signs.

The use of ink jet printing in the production of images is well known. Ink jet printing and its use in making full color images is reviewed in W. E. Haas, "Non-Impact Printing Technologies," pp. 379-384, of Imaging Processes and Materials--Neblette's Eighth Edition, John Sturge, Vivian Walworth & Allan Shepp, eds., Van Nostrand Reinhold, New York, 1989. In these processes, ink droplets are emitted from a nozzle and deposited on a receptor to form an image. Although paper stock is extensively used as the receptor, many other materials are used, such as plastic film and sheet, fabric, metal, wood, and glass. When transparencies are produced, a coated transparent plastic film or sheet typically is used as the receptor.
Ink jet printing processes can produce high quality four-color images in sizes ranging from office copy up to sizes useful for posters, displays and billboards. However, ink jet printing has been limited largely to applications such as office copy in which environmental and/or abrasion damage to the image is unlikely.
In applications in which the image will be subject to handling or exposed to the elements, such as in posters, banners, displays, wall coverings, and particularly billboards, a protective layer is essential to protect the water-sensitive ink jet image and its underlying receptor from rain, sunlight, and other environmental contaminants as well as from abrasion and graffiti. It is important that the protective layer not only be resistant to abrasion, graffiti, and degradation by ultraviolet radiation, it must be non-tacky to prevent blocking during storage of the images, in addition, it must be inexpensive and convenient to apply.
Protective layers that perform very well are known, such as laminated layers of polyethylene terephthalate sheet. However such layers are neither inexpensive nor easy to apply.
Fluoropolymers can provide a surface which is non-sticky and has good resistance to graffiti, because paint does not adhere permanently to it, and which has good resistance to the elements in general. The advantage of fluoropolymer layers is also the major problem with their use as protective layers: nothing sticks to them, but they do not stick to anything. Thus, fluoropolymer layers typically do not adhere to the image they are intended to protect.
Ocampo, U.S. Pat. No. 5,316,608, discloses a protective layer suitable for use with vinyl fabrics. The protective layer comprises a plurality of layers of an acrylic polymer/-fluoropolymer composition, beginning with a layer containing substantially all acrylic followed by layers of increasing fluoropolymer content. This provides a composite layer structure with a top surface having sufficient fluoropolymer content to provide a good weathering surface and an inside surface having sufficient acrylic content to adhere the layer to the receptor. Although this multilayered structure appears successful, it is cumbersome to manufacture and apply. Neumann, U.S. Pat. No. 4,556,89, discloses a composite material composed of a plasticized polyvinyl chloride layer and a protective layer composed of an acrylic polymer, plasticized polyvinyl chloride, and a fluorine-containing copolymer. This protective layer appears to be useful primarily for protection of plasticized polyvinyl chloride layers.
A need exists, therefore, for an inexpensive, clear, transparent, protective layer for ink jet generated images, particularly for large size images, such as posters, panels, banners, displays, and billboards. The protective layer must adhere to the image, be able to withstand weathering and graffiti, have good resistance to abrasion, and not interfere with viewing of the image. Preferably the protective layer should be an integral part of the imaged element so that no additional steps are required for its application.

Ink jet receptor element having a protective layer