The invention relates to a composite material of formula: (C—N—B-MR)x(Al-MR)y(R)z in which C—N—B-MR is one or more carbides, nitrides or borides of one or more refractory metals of group IV, V or VI of the Periodic Table and/or one or more aluminium carbides, nitrides or borides chosen from Al4C3, AlN, AlB2 and Al1-67B22; Al-MR is one or more aluminides of one or more of the above refractory metals, it being understood that: if MR=Nb, Ta, Hf, Zr, Ti or V, then Al-MR=Al3MR; if MR=W or Cr, then Al-MR=Al4MR; if MR=Mo, then Al-MR=Al8Mo3 or Al17Mo4 (≅Al4Mo), and R is a residual component other than carbon, comprising one or more phases chosen from Al4C3, AlN, AlB2, Al1-67B22 and MRtAlu(C—N—B)v in which t, u and v are numbers greater than or equal to zero, and x, y and z are the volume fractions of the respective components with x>y; x+y>0.5; x+y+z+1 and 0.01<y<0.5. The invention is also aimed at the use of this composite material as a coating in a component that can be welled by liquid aluminium and can be used in electrolysis cells.

Aluminum is produced conventionally by the Hall-Héroult process in electrolysis cells by reducing alumina dissolved in an electrolyte based on cryolite melted at temperatures of approximately 960° C. according to the following reaction:Al2O3+3/2C2Al+3/2CO2
The carbon of the anode is consumed during the reaction, and there is CO2 release during aluminum production. The counter electrode or cathode also consists of carbon. Today, graphite blocks are used increasingly as cathode to have a better electrical conductivity and less energy loss in the process. The aluminum is deposited at the bottom of the cell, and it forms a conducting liquid aluminum layer on the surface of the cathodes. This aluminum can react with graphite to form aluminum carbide (Al4C3). This is one of the causes that limit the lifespan of cathodes (typically 3-8 years). Since liquid aluminum does not wet graphite, one usually maintains a relatively thick layer of liquid aluminum at the bottom of the cells (15-25 cm). However, the electromagnetic forces generated by the presence of strong electrical currents and magnetic fields create waves at the surface of this liquid aluminum layer, which can generate short circuits with the anode, if the anode-cathode distance (ACD) is insufficient. To prevent these short circuits, one maintains an ACD of relatively large value of approximately 4.5 cm. The relative displacement of the liquid aluminum layer with respect to the surface of the cathode is also a source of erosion and deterioration of the cathodes.
The resistance of the electrolyte in the gap between the anode and the conducting liquid aluminum layer produces a drop in voltage of approximately 1.5 V for an ACD of 4.5 cm and a typical current density of 0.7 A/cm2. This ohmic drop constitutes the primary source of loss of energy in the process. This is the reason why, in the past decades, intense research has been conducted to develop cathode coatings that are wettable by liquid aluminum to reduce the thickness of the aluminum layer at the bottom of the cells, and thereby also allow a reduction in the anode-cathode distance. Besides being wettable, the coating must be a good electrical conductor, and allow improving the resistance to erosion of the cathodes, thus increasing their lifespans.
The open porosity at the surface of the cathodes, which represents typically 15-20% of the volume of the electrodes, is a source of deterioration, when aluminum and/or sodium originating from the electrolyte effectively penetrates into it and reacts chemically with the carbon. One research area thus consists in seeking products and methods to fill these pores so as to increase the lifespan of the electrodes. The example of the invention, described in the application mentioned below, is illustrative of this subject.
1—WO2000/046427 issued to Carbone Savoie and entitled "Impregnated Graphite Cathode for Electrolysis of Aluminium" describes a graphite cathode with, in its surface pores, a carbon-based product baked at a temperature of less than 1600° C., which makes it possible to increase the resistance to erosion of said cathode.
Moreover, since the electrolysis cells work at very high temperatures, research on protective coatings for cathodes that are wettable by liquid aluminum in the past focussed primarily on refractory materials (MR) or on composites based on refractory materials and carbon. In the context of this invention, a refractory material denotes a material having a very high melting point, typically higher than 1800° C. As far as the carbon is concerned, several types have been used, such as, coal, anthracite, coke, and graphite. The refractory material of first choice that is used most commonly is TiB2 which has been known for many years for its wettability, good electrical conductivity, and its inertness in liquid aluminum.
The following list gives examples of inventions carried out for the purpose of developing methods and coatings to solve this problem:
2—WO1991/018845 in the name of Alcan International Ltd and entitled "Method of Producing Platelets of Borides of Refractory Metals" describes a method for producing platelets of borides of refractory metals as well as platelets so produced, which consists in reacting an oxide of refractory metals with boric oxide (B2O3) and carbon in the presence of a small quantity of alkali metals.
3—WO1993/020027 in the name of MOLTECH INVENT S.A., and entitled "Refractory Protective Coatings, Particularly for Electrolytic Cell Components" describes protective coatings formed by a self-maintained combustion of a colloidal pasty solution (colloidal slurry) containing refractory materials.
4—WO1994/020651 in the name of MOLTECH INVENT S.A. and entitled "The Bonding of Bodies of Refractory Hard Materials to Carboneous Supports" describes a method to glue tiles, plates or bricks made of refractory materials on a carbon-based cathode with the help of a colloidal non-reactive pasty solution comprising preformed particles of refractory materials, such as, TiB2, in a colloidal solution containing fine alumina particles.
5—WO1994/021572 in the name of MOLTECH INVENT S.A. and entitled "Production of Carbon-Based Composite Materials as Component of Aluminium Production Cells" describes a method for manufacturing a composite material comprising a mixture of borides, carbides, oxides and/or nitrides of refractory metals and of aluminum, silicon, titanium or zirconium, which react to form a refractory compound. This mixture is combined with carbon and a colloidal binder containing fine particles, such as, Al2O3.
6—WO1997/006289 in the name of MOLTECH INVENT S.A. and entitled "Maintaining Protective Surfaces on Carbon Cathodes in Aluminium Electrowinning Cells" describes a cathode consisting of blocks of carbon having on the surface a layer which is wettable by liquid aluminum, and which contains particles of titanium boride or boride of other refractory metals, and a porous inorganic binder material containing liquid aluminum, whose content of refractory materials and boron is adjusted so as to prevent the dissolution of the wettable layer of boride of refractory metals.
7—WO1997/008114 in the name of MOLTECH INVENT S.A. and entitled "The Production of Bodies of Refractory Borides for use in Aluminium Electrowinning Cells" describes a method for manufacturing a part made of refractory borides chosen from the borides of Ti, Cr, V, Zr, Hf, Nb, Ta, Mo and Ce, and containing a colloid, such as, alumina or silica, the whole in the form of a pasty solution which is dried, and then treated thermally.
8—WO1998/017842 in the name of MOLTECH INVENT S.A. and entitled "Slurry and Method for Producing Refractory Boride Bodies and Coatings for use in Aluminium Electrowinning Cells" describes a part or a coating of refractory boride similar to the previous one, but in which the pasty solution can also contain an organic additive, such as, polyvinyl alcohol.
9—WO2000/029644 in the name of Alcan International Ltd. and entitled "Wettable and Erosion/Oxidation-Resistant Carbon-Composite Materials" describes a carbon-based composite material which can be used to manufacture blocks or coatings for the cathodes as well as a method for manufacturing a carbon-based composite material which produces in situ TiB2 when exposed to liquid aluminum. The method consists in mixing quantities of TiO2 and B2O3 to produce a precursor mixture, and then mix this product with a component that contains carbon.
10—WO2000/036187 in the name of Alcan International Ltd. and entitled "Multilayer Cathode Structure" describes a method for manufacturing one or more layers of a composite refractory material containing a metal boride on a carbon-based substrate (cathode) which consists in roughening the substrate before the application of the layers to improve their adhesion. When several layers are applied successively, the metal boride content increases progressively so as to minimize the differences between the thermal expansion coefficients of the various materials.
11—WO2001/042531 in the name of MOLTECH INVENT S.A. and entitled "Dense refractory material for use at high temperatures" describes a component or a coating of refractory material comprising particles of refractory materials containing boron, nitrogen, silicon, carbon or phosphorus, the whole in a matrix of oxides. The refractory material is obtained by subjecting a pasty solution (slurry) to a thermal treatment.
12—WO2001/061076 in the name of Alcan International Ltd. and entitled "A method for providing a protective coating for Carbonaceous Components of an Electrolysis Cell" describes a method for protecting a carbon-based electrolysis cell component from deterioration, which consists in preparing a solution of refractory materials in a "lignosulfonate" binder and applying it in the form of a protective coating which is then allowed to dry.
13—WO2001/061077 in the name of Alcan International Ltd. and entitled "Refractory coating for components of an aluminium electrolysis cell" describes a refractory coating for the components of an electrolysis cell manufactured by applying as a coating a pasty solution (aqueous slurry) comprising particles of a refractory material, such as, TiB2 dispersed in an aluminum oxalate complex. When exposed to high temperatures in the electrolysis bath, the complex produces aluminum oxide which binds the refractory particles to each other as well as to the cathode.
14—WO2002/070783 in the name of MOLTECH INVENT S.A. and entitled "Aluminium-Wettable Porous Ceramic Material" describes a material comprising a ceramic that is resistant to liquid aluminum, such as, alumina, and a material wetted by aluminum comprising a metal oxide or a partially oxidized metal including Mn, Fe, Co, Ni, Cu or Zn which reacts or react with Al(l) to form a surface containing alumina, aluminum, and the metal derived from the metal oxide.
15—WO2003/018876 in the name of Alcoa Inc. and entitled "Method for Protecting Electrodes During Electrolysis Cell Start-up" describes a method to apply a protective layer to the cathode of an electrolysis cell comprising a plurality of layers preferably with an internal layer of TiB2, and a protective layer which protects the cathode from the hot gases used to preheat the cell during startup.
16—WO2004/092449 in the name of MOLTECH INVENT S.A. and entitled "Aluminium-Wettable Carbon-based Body" describes a carbon component having an aluminum-wettable external component comprising a carbon rich mixture containing particles based on metals that can react with aluminum. The metal-based particles are metal oxides or partially oxidized metal particles chosen from Fe, Cu, Co, Ni, Zn and Mn.
17—WO2004/011697 in the name of Alcoa Inc. and entitled "Interlocking Wettable Ceramic Tiles" describes an electrolysis cell for aluminum comprising interlocking cathode tiles which are positioned on the graphite blocks. Each tile includes a main body with vertical holding notches to prevent displacement of the tiles out of the surfaces of the graphite blocks during operations.
18—WO2005/052218 in the name of Alcan International Ltd. and entitled "Stabilizers for Titanium Diboride-Containing Cathode Structure" describes a method for stabilizing the surface of the cathodes, which consists in preparing a mixture of materials based on carbon, TiB2, and up to 25 wt % of a finely divided additive comprising two closely linked compounds of which one has a melting point greater than the annealing temperature of the mixture. One applies the mixture to the surface of the cathodes, and when it is placed in contact with the liquid aluminum, the aluminum reacts with the additive to form a dense phase at the surface, which has a low solubility in aluminum. Examples of additives are the TiO2/B2O3 compounds or the TiC/B2O3 compounds.
The methods for manufacturing cathode coatings that are wettable by liquid aluminum include pressing and sintering techniques, when tiles made of dense refractory materials are glued or applied to the surface of graphite, or coating, painting and aerosol type atomization techniques followed by thermal annealing steps, when the refractory product is in the form of a paste or an aqueous or colloidal solution. On the other end, thermal deposition techniques have never been proposed, except insofar as the plasma technique (Air Plasma Spray—APS) is concerned, because, in cases involving the melting of ceramics or of refractory materials, very high temperatures of several thousand degrees Celsius are required (typically 2000-3500° C.). Only a plasma technique using ionized gases reaches these temperatures and energy levels. The invention below is an example thereof.
19—U.S. Pat. No. 3,856,650 in the name of Swiss Aluminium Ltd. in 1974 and entitled "Cathode for an Aluminium Fusion Electrolysis Cell and Method of Making the Same" describes a coating of a ceramic material which is electrically conductive and insoluble in cryolite and liquid aluminum, as well as a method for manufacturing the coating by plasma, which consists in applying the ceramic material in a finely dispersed form with an energy such that one produces a consolidated and adhering coating.
In spite of all the above-mentioned efforts, it appears that none of the inventions has become established on a large scale in industry to date, for the various reasons below:                a) Most of these inventions describe composite materials comprising carbon added in the form of anthracite, coke, graphite or other, and consequently these additives can also react with the liquid aluminum or the sodium of the electrolyte to form aluminum carbide, and lead to the deterioration of the coating.        b) Several of the coatings that have been the object of inventions become detached from the substrate during use, because of the difference in thermal expansion between the coating and the graphite cathode.        c) The inventions which consist in using dense tiles of refractory materials, such as, TiB2, are difficult to apply on a large scale, because of the high costs of the materials and of the manufacturing methods.        d) Most of the patented coating materials are not thermodynamicaliy stable in liquid aluminum, and present a high physical and chemical erosion rate leading to an insufficient lifespan.
In parallel with these developments of protective coatings based on refractory materials that are wettable by liquid aluminum, one also notes a certain number of inventions concerning the "design" of an electrolysis cell, which take advantage of the use of protective coatings that are wettable by liquid aluminum. The patents below are corresponding examples.
20—U.S. Pat. No. 3,400,061 granted in 1968 in the name of Kaiser Aluminium & Chemical Corporation and entitled "Electrolytic Cell for Producing of Aluminium and Method of Making the Same" describes an electrolysis cell in which the conventional cathodic flat bottom made of carbon is replaced by a cathode structure which is drained, inclined, and wettable by aluminum. The drained cathode surface is coated with a refractory substance comprising a mixture of refractory metals and at least 5% carbon.
21—U.S. Pat. No. 5,203,971 granted in 1993 in the name of Moltech Invent S.A. and entitled "Composite Cell Bottom for Aluminium Electrowinning" describes an electrolysis cell whose base consists in part of conductive carbon sections and in part of mutually juxtaposed sections made of nonconductive refractory materials. The sections made of carbon are at the same level or at a lower level with respect to the sections made of refractory materials.
22—WO 1999/002764 granted in the name of MOLTECH INVENT S.A. and entitled "A Drained Cathode Cell for the Production of Aluminium" describes a drained cell in which the surface of the wettable cathode is dimensionally stable and inclined, thus allowing the liquid aluminum produced to flow off the surface. The distance between inclined anode and cathode (ACD) is not more than 3 cm.
23—WO 2002/097168 and WO 2002/097169 in the name of MOLTECH INVENT S.A., entitled "Aluminium Electrowinning Cells Having a Drained Cathode Bottom and an Aluminium Collection Reservoir," describe electrolysis cells for aluminum production comprising a cathode formed from a series of carbon blocks having a surface that is wettable by liquid aluminum.
One cannot end this section on prior art without mentioning the inventions that relate to channeling the aluminum produced to a collecting device. For this purpose, channels (grooves) are usually produced on the surface of the graphite cathodes, which serve not only to drain the liquid aluminum but also, in some cases, to break the waves on the surface of the surface of the liquid aluminum, as described previously. The following two inventions are corresponding examples.
24—WO1996/007773 in the name of MOLTECH INVENT S.A. and entitled "Aluminium Electrowinning Cell with Improved Carbon Cathode Block" describes a cathode consisting of graphite blocks whose surface has been scratched with a series of parallel channels (grooves) in the direction of the current bus bars to diminish the waves and the movements of the layer of liquid aluminum.
25—WO 2000/063463 in the name of MOLTECH INVENT S.A. and entitled "Aluminium Electrowinning Cell Having a V-Shaped Cathode Bottom" and WO2001/031088 entitled "Drained-Cathode Aluminium Electrowinning Cell with Improved Electrolyte Circulation" describe a cathode surface that is wettable by liquid aluminum, and drainable, containing channels (grooves) to collect the aluminum and having V-shaped sections with V-shaped surface to facilitate the flow of the aluminum.
The problem with these last inventions is that they add further costs to the technologies while making the methods more complex, since the wettable coatings are usually applied over the totality of a drainable cathode surface, which now presents relief and a complex geometry.
It is interesting to note that none of the numerous documents describing cathode coatings based on refractory materials that are wettable by liquid aluminum describes with precision the degree of wettability of the coatings in questions. Indeed, to characterize the wettability, these inventions usually limit themselves to applying the coating to a graphite specimen, often cylindrical in shape, and dipping this coated specimen in a bath of liquid aluminum. The analysis by microscopy of the interface between the coating and the aluminum after the solidification of the bath makes it possible to determine whether or not the liquid aluminum wetted the coating properly. However, the wettability of a surface by liquid aluminum is defined by the contact angle that forms when a drop of aluminum is deposited on this surface. A contact angle of less than 90° indicates a good wettability. None of the above-mentioned inventions specifies the degree of wettability of the patented coatings. However, it should be mentioned that the mechanisms that are at the origin of the wettability of the surfaces of refractory materials, such as, TiB2, by liquid aluminum, have never been elucidated precisely.
In the context of the work that led to the present invention, the inventors noticed that there was a connection to be made between the cathode coating materials of electrolysis cells and grain refiners in the aluminum industry, two subjects that appear unrelated at first blush. Grain refiners are additives that one adds in small quantities to molten aluminum alloys to refine their microstructure during the solidification or, in other words, to reduce the size of the aluminum crystals. A fine and uniform microstructure improves the properties of the solidified metal and facilitates its subsequent shaping.
During the cooling, the surface of the grain refiner acts as a heterogeneous nucleation site to crystallize the alloy. To act effectively, the liquid aluminum thus must properly wet the surface of the grain refiner. Two types of grain refiner are available commercially. The Al—Ti—B system (example: Al-5Ti-1B in wt %), and the Al—Ti—C system (example: Al-3Ti-0.15C in wt %). The Al—Ti—B system which is best known consists of small particles of TiB2 in a matrix of aluminum.
Now, recent work published in the literature (26-31):
26—P. Schumacher and A. L. Greer, Mater. Sci. Eng. A, A178 (1994) p. 309.
27—P. Schumacher and A. L. Greer, Mater. Sci. Eng. A, A181/182 (1994) p. 1335.
28—P. Schumacher and A. L. Greer, Proc. Conf. "Light metals 1995" (ed. J. W. Evans) p. 869 (1995), Warrendale, Pa., TMS.
29—P. Schumacher and A. L. Greer, Proc. Conf. "Light metals 1996" (ed. W. Hale) p. 745 (1996), Warrendale Pa., TMS.
30—P. Schumacher, A. l. Greer, J. Worth, P. V. Evans, M. A. Kearns, P. Fisher and A. H. Green, Mater. Sci. Technol., 14 (1998) p. 394.
31—A. M. Bunn, P. Schumacher, M. A. Kearns, C. B. Boothroyd, and A. L. Greer, Mat. Sci. Technol., 15 (1999) p. 1115 suggest that it may not be the surface of the TiB2 as such which acts as nucleation site, but a fine layer of Al3Ti which is thought to be located between the surface of the TiB2 and the aluminum. This thin layer of a Ti aluminide, which has a thickness of several nanometers, and which is responsible for the wettability, is thought to be stabilized by the presence of TiB2 (see reference 29).
During the work that led to the present invention, the inventors, influenced by these recent studies on grain refiners, based themselves on the hypothesis that the presence of refractory metal aluminides is desirable, to ensure a good wettability of the cathode coatings.
Cassie's law, which describes the contact angle of a liquid on a composite material consisting of a refractory ceramic (carbide, nitride or boride) and of a refractory metal aluminide can be expressed as follows:Cos θc=S1 Cos θ1+S2 Cos θ2where θc is the contact angle of the liquid with the composite material, θ1 and θ2 are the respective contact angles on the ceramic and the refractory aluminide, while S1 and S2 are the respective surfaces of the two phases in contact with the liquid. S1=S2=1.
If the wettability on the refractory ceramic is not very high, and θ1 is approximately 90°, the first term of the above equation becomes negligible (cos θ1˜0), and if the wettability on the aluminide is very high, and θ2 is close to 0 (cos θ2˜1), then, under these conditions, the cosine of the contact angle on the composite becomes directly proportional to the surface area of the refractory metal aluminide. The larger the surface area will be, the smaller the contact angle on the composite will be. Consequently, for an aluminide surface fraction of 30%, the contact angle on the composite would be 72.5° or cos−1(0.3). Along the same idea, if one imagines a composite consisting of grains of refractory ceramic (for example, grains of NbB2 or NbC) with grain boundaries of refractory metal aluminide (for example, Al3Nb), the greater the volume fraction and consequently the surface fraction of grain boundaries will be, the greater the wettability of the composite will be. Thus, it will be advantageous to reduce the size of the grains or of the crystallites, and to increase the grain boundary density, as is the case in nanocrystalline materials where the grain boundary density can reach values as high as 30%, when the size of the grains is on the order of few nanometers. By definition, a nanocrystalline material is a material for which the size of the grains or crystals is less than 100 nm.

Composite materials for wettable cathodes and use thereof for aluminum production


Novel nonlinearly optically active polyurethane polymers, well suited for electrooptical applications, have recurring structural units of the formula: ##STR1## in which m is a number greater than 5; R.sub.1 and R.sub.2, which may be identical or different, are each a saturated or unsaturated alkyl or aromatic radical; R.sub.3 is a linear aliphatic, or cyclic aromatic or arylaliphatic hydrocarbon radical; and Y is a group including a radical containing dislocated .pi. electrons and an electron acceptor group (A).

1. Field of the Invention
The present invention relates to novel polyurethane polymers useful in the production of materials having nonlinear optical activity.
Materials displaying nonlinear optical activity may have a strong cubic (.chi..sup.3) or quadratic (.chi..sup.2) susceptibility. This invention more especially relates to polymers or materials having a high quadratic susceptibility after polarization, and which also have a good cubic susceptibility.
2. Description of the Prior Art
Numerous polymers are known to this art that possess the property of being nonlinearly optically active. In certain cases, this activity is greater than that of the inorganic materials currently used for such purpose.
Polymers used in NLO (nonlinear optics) generally contain conjugate groups with dislocated electrons, which provide them with a significant cubic .chi..sup.(3) susceptibility value.
Furthermore, in certain polymers (including those of the present invention), the groups responsible for the NLO activity are not centrosymmetrical and have a strong hyperpolarizability .beta. of the second order.
These noncentrosymmetrical groups are most typically conjugated groups with transfer of charges, the orientation of which within the materials by a polarizing electrical field renders the material noncentrosymmetrical. The material then has a nonzero quadratic susceptibility .chi..sup.(2).
Heretofore, these polymers were polymers with conventional backbones, such as the polyolefins, polyacrylates, polymethacrylates, polychloroacrylates or polysiloxanes, for example, onto which polar charge transfer groups were grafted.
Compare, for example, EP-No. 262,680 and FR-No. 597,109. However, these polymers have certain disadvantages and, in particular, difficulties are encountered in the preservation of their nonlinear optical activity. Indeed, the graft segments must have a certain mobility to enable their orientation in an electrical field. But they always retain a certain residual mobility, whereby over the course of time they may lose their orientation. This results in a decrease in their electronic centrosymmetry generated by the electrical field and, consequently, in their nonlinear optical activity. This phenomenon is illustrated in the article by C. Ye et al, "M.R.S. Symposium Proc.", Vol. 109 (Nonlinear Opt. Proc. of polymers, p 263) J. Heeger Editor, 1988.
Another disadvantage of these polymers resides in the fact that the number of polar groups with charge transfer is generally low, as it is a function of the structure of the polymer. Furthermore, the number of grafts cannot be very high without introducing a significant change in the properatives of the polymer.
Materials are also known to the art which possess nonlinear optical activities and typically are constituted by a polymer matrix, into which is dissolved a compound having a nonlinear optical activity cf the conjugate/charge transfer molecule type.
However, these compounds generally have low solubilities in the matrix and also possess a residual mobility in such matrix, which in time will effect a disorientation of said compounds, which renders the material centrosymmetric relative to electrical charges.
In fact, the quadratic nonlinear optical activity is generated by the dislocation of the electrons and a substantial noncentrosymmetry of the charges at the molecular and material level.

Novel nonlinearly optically active polyurethanes


An intake air temperature sensor capable of detecting an intake air temperature highly accurately and at high speed. The intake air temperature sensor of the present invention includes: a secondary passage 7 taking in an intake airflow; a flow rate detecting element 13 disposed in the secondary passage 7; an intake air temperature detecting element 4 provided outside the secondary passage; a temperature sensor 9 detecting a temperature of a fitting section of the intake air temperature detecting element 4; a circuit board 11 disposed in a casing; and an integrated circuit 10 applying a correction process to an output of the intake air temperature detecting element 4 on the basis of signals output from the temperature sensor 9 and a flow rate detecting element 13.

1. Field of the Invention
The present invention relates to an intake air temperature sensor, and particularly to an intake air temperature sensor with little effect of the temperature of a sensor fixing member and self-heating of a circuit section, and a thermal airflow meter including the same.
2. Background Art
For instance, JP Patent Application Publication No. 2005-9965 A (2005) discloses an intake air temperature sensor in which an intake air temperature is detected based on information of a first temperature sensor disposed at a flow rate measuring element and a second temperature sensor disposed in a casing.
However, the technique described in JP Patent Application Publication No. 2005-9965 A (2005) does not give much consideration to air temperature variation in a secondary passage due to the temperature of a secondary passage structure, an effect on the second temperature sensor due to self-heating of circuits disposed in the casing, the thermal time constant of the casing from several tens of seconds to several minutes and the like.
The structure of the secondary passage has a temperature different from that of an airflow to be measured owing to heat from a sensor fixing member and self-heating of circuits. Accordingly, owing to adverse effects of heat from the structure of the secondary passage, the temperature of the air in the secondary passage is changed and becomes a temperature different from that of the airflow to be measured, which causes a problem in that an error occurs in an output of the intake air temperature sensor in the above technique.
Further, since variation in the temperature of the structure of the secondary passage is affected by the thermal time constant of the casing, several tens of seconds to several minutes are required to stabilize the temperature of the structure of the secondary passage. Accordingly, the above technique has a problem that the output of the intake air temperature sensor is unstable for several tens of seconds to several minutes after the intake air temperature is changed.
Variation in airflow rate varies the power consumption of a drive circuit for driving an airflow rate sensor and in turn varies the self-heating of the circuits. Here, time until the temperature of the casing is stabilized is also affected by the thermal time constant of the casing. Accordingly, it is required several tens of seconds to several minutes until an output from the second temperature sensor is stabilized. This causes a problem in that the output of the intake air temperature sensor, which is corrected on the basis of the output of the second temperature sensor, is also unstable for several tens of seconds to several minutes after the airflow rate varies.

Intake air temperature sensor and thermal airflow meter including the same


A video-on-demand system transfers video content signals to a first communication system. The video-on-demand system transfers a control screen signal to a second communication system and receives a video control signal from the second communication system. The video-on-demand system implements a viewer control selection indicated by the video control signal. The control screen could be a web page that includes a video display control menu comprising play stop, pause, rewind, and fast forward. The control screen could include a video content selection menu. The video-on-demand system implements the control screen menu selections.

1. Field of the Invention
The invention is related to the field of video systems, and in particular, to a video-on-demand system that provides a viewer with remote control.
2. Description of the Prior Art
Video-on-demand systems are currently being designed and implemented. The video-on-demand system offers an individual viewer various selections from a video content library for viewing on-demand. Some examples of video content include movies, television shows, documentaries, news, and sports. The video-on-demand system receives a request from the viewer to view a particular selection from the video content library. In response to the request, the video-on-demand system transfers the selected video content over a communication system to the viewer""s display. Thus, the video-on-demand system allows a viewer to immediately view selected video content.
Video-on-demand systems use a television set-top box for remote control. Using the set-top box, the viewer may view a video content menu on the television and order video content for display on the television. The viewer may also view a video control menu on the television to play, stop, pause, rewind, and fast forward the video content on the television Unfortunately, the set-top box is a special component that is closely coupled to the television. The set-top box does not have other uses.
The invention solves the above problems with a video-on-demand system that allows the viewer to use a portable computer connected over second communications system for remote control. The second communications system could be the web, and the portable computer could run a web browser. Advantageously, the viewer can control the video display using their portable computer. The portable computer has many other uses and eliminates the cost of a special television set-top box.
The video-on-demand system transfers video content signals to a first communication system. The video-on-demand system transfers a control screen signal to a second communication system and receives a video control signal from the second communication system. The video-on-demand system implements a viewer control selection indicated by the video control signal. The control screen could be a web page that includes a video display control menu comprising play, stop, pause, rewind, and fast forward. The control screen could include a video content selection menu. The video-on-demand system implements the control screen menu selections.

Remote control of video-on-demand system


Monitoring and measuring colored samples by the techniques of liquid scintillation counting employs the relationship of absorbance and counting efficiency. A determination of whether color quench correction is required is made. Should a color monitor detect a color intensity which requires color correction, then efficiency correction is performed here. Both the color monitor and the color correction of efficiency are incorporated into a liquid scintillation counter which performs color monitoring, measurement and correction automatically.

This invention relates to liquid scintillation counting. In particular the invention is concerned with a system for monitoring and measuring the color of samples in a liquid scintillation counter. The system is directed to determining whether the color in a liquid scintillation sample is sufficiently intense such that direct activity, namely disintegrations per minute (DPM) of the sample can be determined from a conventional chemical quench curve.
It is known that fewer photons leave the vial of a quenched liquid scintillation sample relative to photons leaving an unquenched sample. Three primary quenching processes are known: chemical, color, and absorption. Each of these processes interferes with one of the energy exchange processes required for the production of light and its detection by a photomultiplier tube.
The effect of quenching can be described in relation to the following energy transfer processes which take place in a liquid scintillation cocktail.
______________________________________ 1. .sup.--B + .sup.--S .fwdarw. S + B electronic excitation of the solvent 2. .sup.--S + .sup.--F .fwdarw. S + F electronic excitation of the Fluor 3. .sup.--F .fwdarw. F + hV photon emission by the Fluor 4. hV + PMT .fwdarw. Ep photoelectric electron emission by the PMT ______________________________________
A beta particle, B, with kinetic energy interacts with a solvent molecule, S, in the cocktail causing its electronic excitation, S; step 1. The excess electronic energy of the solvent can be passed to a fluor molecule, F, causing its electronic excitation, F; step 2. The excited fluor molecule can emit a photon, hV; step 3, and return to the electronic ground state. This photon, after leaving the vial, can interact with the cathode of a photomultiplier tube and produce a photoelectric electron. This signal is amplified and represents the "observation of a radionuclide decay event."
Quench refers to any process which interferes with the energy exchange reactions represented in the above steps. Absorption quench refers to processes which interfere with step 1. In other words, a beta particle is prevented by absorption from reacting with a solvent molecule. Chemical quench refers to interference either with excitation of F, step 2, or via internal energy mode decay which prevents production of hV in step 3. Some molecule other than the solvent is excited by the beta particle, thereby preventing solvent excitation. Color quench refers to any chemical which absorbs hV produced by the fluor so that light does not reach the PMT in step 4.
The wavelength of the emitted light depends upon the specific fluor. This generally lies between 380-430 nm; however, the emission bands are broad and may extend beyond these wavelengths. Any substance absorbing energy in the stated wavelength range decreases the number of photons leaving the sample vial. Where the DPM in the sample is required a quench curve is used. This requires the counting efficiency, E, of the sample as defined by: ##EQU1## where the counts per minute (CPM) is observed for a sample having DPM disintegrations per minute. To obtain DPM for an unknown, CPM is measured directly by a liquid scintillation counter while E is obtained from a quench curve previously prepared. A quench curve relates nuclide counting efficiency, E, to some quench monitor, for instance the H# in Horrocks (U.S. Pat. No. 4,075,480). A quench curve is developed from a set of quenched standards, each containing the same number of DPM's of the same radionuclide, but containing a different quantity of a chemical quench agent.
With the availability of the quench curve, the DPM of an unknown sample is obtained by measurement of the H# and CPM of the sample. The counting efficiency is obtained from the H# and quench curve.
This gives accurate values for DPM provided that only chemical quench is present. Should color quench be present, then a chemical quench curve does not always recover DPM correctly, since there is a difference between chemical and color quench curves in terms of H#. As the level of quench increases, the difference between the chemical and color quench curves increases, thus leading to increased percentage error in DPM.
Different quench curves are thus required for chemically quenched standards and for a set of color quenched standards. For measuring an unknown sample it would be necessary to know beforehand which quench curve to use. Furthermore, if an unknown contained both chemical and color quenching agents or a color agent which absorbed at a wavelength different from the agent used for the quench curve standard, then the available curves would not provide the correct answer. Accordingly, a variety of quench curves is needed to answer correctly for a variety of chromophores at a variety of quench levels.
Some limited solutions for color quench correction have been suggested. The suggested color quench curve corrections have been for specific systems with one exception. Specific systems are those with no variations between the standard and the unknown regarding the cocktail, chromophore or level of quench present.
Also, quench monitors with limitations have been reported; none however, has been placed on an automatic liquid scintillation counter.
One prior art approach depends upon correlations between counting efficiency and spectroscopic parameters such as absorbance or wavelength of the absorber. A second approach depends upon the development of and analysis of four different quench curves which are functions of two different quench monitors for the two types of quench, color and chemical. The third approach involves some variation on the concept of lesser pulse height analysis. A fourth approach includes isolated internal standards and spectral analysis Additionally other investigators have sought to solve the problem in effect by either establishing color quench curves and measuring unknowns from them or by decolorizing the system through the use of chemical oxidizing agents.
There has been limited success with the spectroscopy approach in trying to correlate the primary wavelength of absorption of the chromophore with the counting efficiency of the sample. A multicomponent analysis approach to the use of the Beer-Lambert law correlating absorbance and the counting efficiency of the sample has also been attempted. Difficulties with these methods include the numerous measurements and the awkwardness of automation.
Using the four quench curve approach, two quench curves are developed for pure chemical quench and two for pure color quench. For an unknown having pure chemical quench, the two quench curves for chemical quench would give the same values for the counting efficiency while the two color curves would not. Should the unknown be pure color quenched, then the two color quench curves would give the same efficiency while the chemical quench curves would not. This scheme is not useful if both chemical and color quench are present. An advantage of this method however is that it provides a built-in quench monitor.
With the lesser pulse height analysis technique, the pulses from two photomultiplier tubes are examined separately. This allows mathematical analysis to combine advantageously the results of summation counting from both tubes with single tube results either in or out of coincidence.
In general, if light is generated at a point, in a sample, then one path, to one photomultiplier tube is shorter than a second path, to a second photomultiplier tube. This difference is important, since, if color is present, absorbance, As, is path length dependent, L. Absorbance is also concentration, C, and chromophore dependent, A , according to the Beer-Lambert law: EQU As=ALC
Assuming that the same number of photons leave along both paths, then fewer photons will arrive at one tube than the other tube in accordance with the Beer-Lambert law because the one path is longer than the other path. The pulse arriving at the one tube will be of lesser intensity. In general, for each decay event in the presence of color, the intensities of the two pulses arriving at the respective tubes will be different. Laney (U.S. Pat. No. 3,725,657) and Jordan (U.S. Pat. No. 4,292,520) disclose using the lesser intense pulse to monitor counting efficiency.
Here, the separated color and chemical quench curves which occur if summed coincidence is used, become one curve if the lesser pulse is used. In other words, the color effect is not monitored by the lesser pulse, since it is lost. This is both advantageous and disadvantageous. One advantageous aspect is that only one quench curve per radionuclide is required to obtain counting efficiencies for both color and chemically quenched samples. The technique however does not solve the color correction problem in a general sense, since the chemical and color quench curves split apart again at higher quench levels even if lesser pulse height analysis is used. The lesser pulse height technique is also not capable of providing a color monitor since the technique is insensitive to color.
With an isolated internal standard technique a "sealed internal standard" in a pyrex tube with a small internal diameter is prepared. This standard contains a sample of the radionuclide to be measured in an unknown. Preparation of sealed internal standards for each radionuclide of interest is required. The mechanical placement of the internal standard into a sample vial, its removal and cleaning prior to use in the next sample is not conducive to an automated operation.
No combination of color monitor and color correction has been developed together and incorporated onto an automated liquid scintillation counter in any of the methods discussed above.
It is an object of the present invention to provide a monitor to determine whether a given chemical quench curve can be applied accurately to a given sample.

Color monitoring in liquid scintillation systems


There is provided a thin glass elongated body having a small amount of air bubbles between a thin glass and a resin film. A thin glass elongated body of the present invention includes: a thin glass having an elongated shape; and a resin film bonded onto at least part of the thin glass, wherein the resin film has, in a portion in which the thin glass and the resin film are laminated, a plurality of cutting lines and/or holes each penetrating through the resin film.

In recent years, light-weighting and thinning of a display device, an illumination device, and a solar battery have been progressed from the viewpoints of transportation, storage, design, and the like. Further, continuous production has also been carried out to manufacture a film-shaped member to be used in those devices by a roll-to-roll process. For example, a thin glass is frequently used as a flexible material which may be subjected to processing or treatment by the roll-to-roll process (for example, Patent Literatures 1 and 2).
The thin glass involves problems in that the thin glass is liable to be broken in its processing or treatment owing to its extreme fragility, a device is fouled with glass pieces resulting from the breakage, excessive caution is required for restoration of the fouled device, and the like. In order to prevent the breakage of the thin glass, and to prevent the fouling of the device even when the thin glass is broken, a method of bonding a protective film onto a surface of the thin glass to protect the thin glass has been known (for example, Patent Literature 3). However, when a film, such as the protective film, is bonded onto the thin glass, there is a problem in that air is trapped between the thin glass and the film to generate air bubbles. In the case where the thin glass having the film is taken up with the air bubbles generated, the thin glass is liable to be broken due to the air bubbles. Further, in the case where the thin glass having the film with the air bubbles generated is subjected to a roll-to-roll process into which laminate roll, a nip roll, or the like is incorporated, the air bubbles accumulate at an inlet of the roll and increase in size while the thin glass having the film continuously passes through the roll, with the result that troubles are liable to occur during processing and conveyance. Further, in the thin glass having the film having a difference in surface level, air is liable to be trapped between the thin glass and the film during bonding, and thus the above-mentioned problem becomes more conspicuous. Various problems are caused in the thin glass having the film with the air bubbles generated, and hence, in the case where air is trapped between the thin glass and the film during bonding of the film, an attempt is generally made to perform peeling and rebonding (rework) of the film. However, the thin glass serving as an adherend is liable to be broken during peeling of the film, and it is also difficult to rework the film.


The present technology relates to a focus detection device and method and a program by which an accurate image shift amount can be detected. A calculation unit performs calculation based on learning on the basis of a received light amount distribution of an A pixel group having a first property for phase difference detection and a received light amount distribution of a B pixel group having a second property different from the first property and outputs defocus amount related information relating to a defocus amount. The present technology can be applied to an imaging apparatus that performs focus detection by a phase difference detection method.

A pupil splitting phase difference detection method is known which performs focus detection using output signals of a pair of phase difference detecting pixels (hereinafter referred to as phase difference pixels) for performing pupil splitting of an imaging lens. In the pupil splitting phase difference detection method, an image shift amount of output signals of a pair of phase difference pixels is detected by performing center-of-gravity calculation, and the detected image shift amount is converted into a defocus value using a conversion coefficient. In order to calculate the conversion coefficient for the detected image shift amount, a technology is proposed which calculates the conversion coefficient using aperture information of the imaging lens and sensitivity information of the light receiving angles of the phase difference pixels.
Meanwhile, as a method for detecting an image shift amount, a correlation calculation method is known which shifts output signals of a pair of phase difference pixels and determines the shift amount at which the correlation of the waveforms indicates a maximum value as an image shift amount.
However, since waveforms of phase difference pixels (hereinafter referred to as phase difference waveforms) in the pupil splitting phase difference detection method described above have a characteristic that they do not coincide with each other in principle, it is difficult to provide a conversion coefficient appropriate for an image shift amount detected by center-of-gravity calculation.
Therefore, a technology has been proposed in which an image shift amount calculated by the correlation calculation method is provided as a correction value to an image shift amount detected by center-of-gravity calculation (refer to PTL


A working surface incorporates a means for transferring mechanical energy produced by a rotating member of the working surface so that the energy rotates a shaft attached to an alternator that charges a bank of 12 V batteries. The alternator is responsible for converting the mechanical energy being input by the rotating shaft to electrical energy that is fed to the batteries. The batteries transfer the energy into an inverter for use depending upon the required amount. Thereby, backup electrical power may be generated and stored, taking advantage of excess horsepower at cruise provided by a vehicle as well as better utilizing travel time. Additionally, the added cost of ownership and noise of a portable power generator is avoided.

The present invention relates to electrical power generation and storage devices for portable or emergency use. While portable electrical generators are quite useful for emergency situations or austere environments, such generators tend to be inconvenient with regard to maintenance, transport, duration, and reliability. Consequently, a significant need exists for a more convenient and cheaper method of providing back-up electrical power.
Various kinds of portable generators exist in the current market. The uses for these generators range from home use to industrial use. Conventional portable generators comprise an engine and an alternator driven by the engine to produce electricity. Specifically, the spark-ignited combustion engine produces mechanical drive to rotate a crankshaft. The crankshaft, connected with a revolving shaft of the generator, will produce electrical current by converting the mechanical power produced by the engine into electrical energy. The mechanical energy drives the crankshaft to rotate electrically conductive elements within a magnetic field. The rotation of the electrically conductive elements around the field produces electric energy capable of being used or stored.
A more desirable form of energy storage is extremely valuable as a result of the continual rise of fuel prices, the concern for the environment, and the decline of the amount of fossil fuels. A portable power source that can produce electrical energy by converting mechanical energy would help reduce the cost of energy, protect the environment, and provide a reliable, convenient source of energy. The traditional portable electric generators consume gasoline to produce the mechanical drive necessary to rotate the electrically conductive elements. By contrast, using a rotating axle coupled with a gear system or other means would provide the necessary mechanical drive to produce electrical energy as opposed to wasting other energy sources and utilizing a portion of the power of a vehicle that would otherwise be unused.
A more efficient approach as stated earlier would be to use a mechanical drive system already being used, such as the wheel axle of a towed vehicle or a drive system of a car, to effectuate the rotation of the shaft of an alternator. This rotation of the shaft by means including but not limited to gears, pulleys, and transmissions will produce electric power capable of being stored within a single battery or a series of batteries. The power may then be converted by an inverter from direct current to alternating current as desired by the user.

Trailer with integral axle-mounted generator and battery charger


A feeder-folder unit for use in folding paper sheet stock and delivering it to a signature gathering machine comprises a main frame with a hopper assembly carried by the main frame for receiving and storing a supply of sheets of paper stock. A sheet extractor and transfer drum assembly is located adjacent the hopper for extracting individual sheets of paper stock from the hopper means and conveying the extracted sheets along a path to a scoring and folding unit located adjacent the path. The hopper assembly includes a pair of spaced support surfaces for supporting the sheets of stock and intermittently actuated drive chains are provided for driving the sheets along the support surfaces toward the sheet extractor and transfer drum assembly. Each of the support surfaces is adjustable independently of the other and the drive chains to selectively vary the presentation of the sheets to said sheet exterior and transfer drum assembly to thereby permit precise positioning of the sheets relative to the scoring and folding unit.

The subject invention is directed toward the art of signature gathering machines and, more particularly, to a feeder-folder unit for feeding individual sheets or signatures from a supply hopper through a folding unit. The unit is particularly suited for handling and precision folding cover stock and will be described with particular reference thereto; however, it should be appreciated that that a unit of the type under consideration is capable of handling and folding a variety of types of sheet material for many uses.
As can be appreciated, when feeding and folding relatively stiff and rigid cover stock, it is desirable to maintain the folds at a precision location on the stock so that the mating edges of the folded cover match with great precision. Additionally, it is highly desirable that the fold be relatively crisp and smooth with no damages to the sheet stock adjacent the fold.
The above noted needs and goals for an apparatus of this type is met by the subject invention which provides an extremely effective and efficient feeder folder apparatus wherein the supply hopper is provided with means which permit extremely fine and delicate adjustments to be made in the location of the feed stock relative to the feeder scoring and folding units. Additionally, the folding unit is designed such that the fold is made very effectively with a minimum of disturbance or damage to the stock adjacent the fold line.


Plants made resistant to insects by transforming their nuclear genome with two or more DNA sequences, each encoding a different non-competitively binding B. thuringiensis protoxin or insecticidal part thereof, preferably the toxin thereof.

Since the development and the widespread use of chemical insecticides, the occurrence of resistant insect strains has been an important problem. Development of insecticide resistance is a phenomenon dependent on biochemical, physiological, genetic and ecological mechanisms. Currently, insect resistance has been reported against all major classes of chemical insecticides including chlorinated hydrocarbons, organophosphates, carbamates, and pyrethroid compounds (Brattsten et al., 1986).
In contrast to the rapid development of insect resistance to synthetic insecticides, development of insect resistance to bacterial insecticides such as B. thuringiensis sprays has evolved slowly despite many years of use (Brattsten et al., 1986). The spore forming gram-positive bacterium B. thuringiensis produces a parasporal crystal which is composed of crystal proteins (ICPs) having insecticidal activity. Important factors decreasing the probability of emergence of resistant insect strains in the field against B. thuringiensis sprays are: firstly the short half-life of B. thuringiensis sprays after foliar application; secondly the fact that commercial B. thuringiensis preparations often consist of a mixture of several insecticidal factors including spores, ICPs and eventually beta-exotoxins (Shields, 1987); and thirdly the transitory nature of plant-pest interactions. Many successful field trials have shown that commercial preparations of a B. thuringiensis containing its spore-crystal complex, effectively control lepidopterous pests in agriculture and forestry (Krieg and Langenbruch, 1981). B. thuringiensis is at present the most widely used pathogen for microbial control of insect pests.
Various laboratory studies, in which selection against B. thuringiensis was applied over several generations of insects, have confirmed that resistance against B. thuringiensis is seldom obtained. However, it should be emphasized that the laboratory conditions represented rather low selection pressure conditions.
For example, Goldman et al. (1986) have applied selection with B. thuringiensis israelensis toxin over 14 generations of Aedes aegypti and found only a marginal decrease in sensitivity. The lack of any observable trend toward decreasing susceptibility in the selected strains may be a reflection of the low selection pressure (LC50) carried out over a limited number of generations. However, it should be pointed out that Georghiou et al. (In: Insecticide Resistance in Mosquitoes: Research on new chemicals and techniques for management. In "Mosquito Control Research, Annual Report 1983, University of California.") with Culex quinquefasciatus obtained an 11-fold increase in resistance to B. thuringiensis israelensis after 32 generations at LC95 selection presssure.
McGaughey (1985) reported that the grain storage pest Plodia interpunctella developed resistance to the spore-crystal complex of B. thuringiensis; after 15 generations of selection with the Indian meal moth, Plodia interpunctella, using a commercial B. thuringiensis HD-1 preparation ("Dipel", Abbott Laboratories, North Chicago, Ill. 60064, USA), a 100-fold decrease in B. thuringiensis sensitivity was reported. Each of the colonies was cultured for several generations on a diet treated with a constant B. thuringiensis dosage which was expected to produce 70-90% larval mortality. Under these high selection presssure conditions, insect resistance to B. thuringiensis increased rapidly. More recently, development of resistance against B. thuringiensis is also reported for the almond moth, Cadra cautella (McGaughey and Beeman, 1988). Resistance was stable when selection was discontinued and was inherited as a recessive trait (McGaughey and Beeman, 1988). The mechanism of insect resistance to B. thuringiensis toxins of Plodia interpunctella and Cadra cautella has not been elucidated.
The main cause of B. thuringiensis resistance development in both reported cases involving grain storage was the environmental conditions prevailing during the grain storage. Under the conditions in both cases, the environment was relatively stable, so B. thuringiensis degradation was slow and permitted successive generations of the pest to breed in the continuous presence of the microbial insecticide. The speed at which Plodia developed resistance to B. thuringiensis in one study suggests that it could do so within one single storage season in the bins of treated grain.
Although insect resistance development against B. thuringiensis has mostly been observed in laboratory and pilot scale studies, very recent indications of B. thuringiensis resistance development in Plutella xylostella populations in the (cabbage) field have been reported (Kirsch and Schmutterer, 1988). A number of factors have led to a continuous exposure of P. xylostella to B. thuringiensis in a relatively small geographic area. This and the short generation cycle of P. xylostella have seemingly led to an enormous selection pressure resulting in decreased susceptibility and increased resistance to B. thuringiensis.
A procedure for expressing a B. thuringiensis ICP gene in plants in order to render the plants insect-resistant (European patent publication ("EP") 0193259 {which is incorporated herein by reference}; Vaeck et al., 1987; Barton et al., 1987; Fischhoff et al., 1987) provides an entirely new approach to insect control in agriculture which is at the same time safe, environmentally attractive and cost-effective. An important determinant for the success of this approach will be whether insects will be able to develop resistance to B. thuringiensis ICPs expressed in transgenic plants (Vaeck et al., 1987; Barton et al., 1987; Fischhoff et al., 1987). In contrast with a foliar application, after which B. thuringiensis ICPs are rapidly degraded, the transgenic plants will exert a continuous selection pressure. It is clear from laboratory selection experiments that a continuous selection pressure has led to adaptation to B. thuringiensis and its components in several insect species. In this regard, it should be pointed out that the conditions in the laboratory which resulted in the development of insect-resistance to B. thuringiensis are very similar to the situation with transgenic plants which produce B. thuringiensis ICPs and provide a continuous selection pressure on insect populations feeding on the plants. Mathematical models of selection pressure predict that, if engineered insect-resistant plants become a permanent part of their environment, resistance development in insects will emerge rapidly (Gould, 1988). Thus, the chances for the development of insect resistance to B. thuringiensis in transgenic plants may be considerably increased as compared to the field application of B. thuringiensis sprays. A Heliothis virescens strain has been reported that is 20 times more resistant to B. thuringiensis HD-1 ICP produced by transgenic Pseudomonas fluorescens and 6 times more resistant to the pure ICP (Stone et al., 1989). Furthermore, the monetary and human costs of resistance are difficult to assess, but loss of pesticide effectiveness invariably entails increased application frequencies and dosages and, finally, more expensive replacement compounds as new pesticides become more difficult to discover and develop.
Therefore, it would be desirable to develop means for delaying or even preventing the evolution of resistance to B. thuringiensis.
B. thuringiensis strains, active against Lepidoptera (Dulmage et al., 1981), Diptera (Goldberg and Margalit, 1977) and Coleoptera (Krieg et al., 1983), have been described. It has become clear that there is a substantial heterogeneity among ICPs from different strains active against Lepidoptera, as well as among ICPs from strains active against Coleoptera (Hofte and Whiteley, 1989). An overview of the different B. thuringiensis ICP genes, that have been characterized, is given in Table 2 (which follows the Examples herein).
Most of the anti-Lepidopteran B. thuringiensis (e.g., Bt3, Bt2, Bt73, Bt14, Bt15, Bt4, Bt18) ICP genes encode 130 to 140 kDa protoxins which dissolve in the alkaline environment of an insect's midgut and are proteolytically activated into an active toxin of 60-65 kDa. These ICPs are related and can be recognized as members of the same family based on sequence homologies. The sequence divergence however is substantial, and the insecticidal spectrum, among the order Lepidoptera, may be substantially different (Hofte et al., 1988).
The P2 toxin gene and the cry B2 gene are different from the above-mentioned genes in that they do not encode high molecular weight protoxins but rather toxins of around 70 kDa (Donovan et al., 1988 and Widner and Whiteley, 1989, respectively).
It has recently become clear that heterogeneity exists also in the anti-Coleopteran toxin gene family. Whereas several previously reported toxin gene sequences from different B. thuringiensis isolates with anti-Coleopteran activity were identical (EP 0149162 and 0202739), the sequences and structure of bt21 and bt22 are substantially divergent (European patent application ("EPA") 89400428.2).
While the insecticidal spectra of B. thuringiensis ICPs are different, the major pathway of their toxic action is believed to be common. All B. thuringiensis ICPs, for which the mechanism of action has been studied in any detail, interact with the midgut epithelium of sensitive species and cause lysis of the epithelial cells (Knowles and Ellar, 1986) due to the fact that the permeability characteristics of the brush border membrane and the osmotic balance over this membrane are perturbed. In the pathway of toxic action of B. thuringiensis ICPs, the binding of the toxin to receptor sites on the brush border membrane of these cells is an important feature (Hofmann et al., 1988b). The toxin binding sites in the midgut can be regarded as an ICP-receptor since toxin is bound in a saturable way and with high affinity (Hofmann et al., 1988a).
Although this outline of the mode of action of B. thuringiensis ICPs is generally accepted, it remains a matter of discussion what the essential determinant(s) are for the differences in their insecticidal spectra. Haider et al. (1986) emphasize the importance of specific proteases in the insect midgut. Hofmann et al. (1988b) indicate that receptor binding is a prerequisite for toxic activity and describe that Pieris brassicae has two distinct receptor populations for two toxins. Other authors have suggested that differences in the environment of the midgut (e.g., pH of the midgut) might be crucial.

This patent is subject to a terminal disclaimer.


A dynamic A-MSDU enabling method is disclosed. The method enables the recipient of an aggregate MAC service data unit (A-MSDU) under a block ACK agreement to reject the A-MSDU. The method thus distinguishes between A-MSDU outside of the block ACK agreement, which is mandatory, from A-MSDU under the block ACK agreement, which is optional. The method thus complies with the IEEE 802.11n specification while enabling the recipient to intelligently allocate memory during block ACK operations.

The Institute of Electrical and Electronics Engineers (IEEE) has adopted a set of standards for wireless local area networks (LANs), known as 802.11. Wireless products satisfying 802.11a, 802.11b, and 802.11g are currently on the market, for example.
Recently, an 802.11n standard, known also as the Enhancement for High Throughput wireless standard, has emerged. Under the 802.11n standard, transmitters and receivers each have multiple antennas for transmission and reception of data. As a multiple input, multiple output (MIMO) technology, 802.11n is designed to coordinate multiple simultaneous radio signals, and is expected to support a bandwidth of greater than 100 megabits per second (Mbps).
Under 802.11, a device (or client), also known as a station (STA), accesses a wireless LAN (WLAN) by following a communication protocol, essentially involving the transmission of frames to an access point (AP). The frames, or packets, may be data frames, control frames, or management frames. The frames convey information that enables the AP to "connect" the device to the WLAN. The APs and STAs in a WLAN constitute a wireless neighborhood.
The 802.11n specification defines two parallel types of packet aggregation: aggregate MAC service data unit (A-MSDU) and aggregate MAC protocol data unit (A-MPDU), where MAC is shorthand for medium access controller. The A-MSDU and A-MPDU may be used separately or together. A MAC service data unit (MSDU) is the frame entering or exiting the top of the MAC. A MAC protocol data unit (MPDU) is the frame entering or exiting the bottom of the MAC.
The aggregate MSDU, A-MSDU, aggregates data MSDUs into one MAC protocol data unit, or MPDU. Each such packet included in the MPDU contains a short header with the byte count, the destination address, and the source address. The aggregate MPDU, A-MPDU, aggregates MPDUs into one PHY protocol data unit, or PPDU, with PHY being shorthand for the physical layer of the stack.
A merger of both aggregation types, A-MSDU and A-MPDU, means that an MPDU containing A-MSDU is included in A-MPDU. Both types of aggregation are mandatory in the current draft of the 802.11n specification. The receiver, or recipient, is therefore expected to support both types of aggregation when prompted by the transmitter, or originator.
Under 802.11n, the maximum size, known as the maximum transmission unit, or MTU, of A-MSDU is approximately 4 Kilobytes (Kbytes). The MTU that can be sent by MPDU is 1500 bytes. To support A-MSDU, the recipient has to be able to receive the full-sized A-MSDU. In other words, the recipient must allocate memory to receive the A-MSDU packet.
There are two ways to transmit an A-MSDU packet. The packet may be sent under the normal acknowledge (ACK) protocol. Alternatively, the packet may be transmitted using a block ACK agreement. An A-MPDU, by contrast, mandates using a block ACK agreement.
To use or not use either type of aggregation, A-MSDU or A-MPDU, is entirely up to the originator, the station that transmits the data. The station that receives the data, or recipient, should be prepared to receive the data, whatever the aggregation types is. A station that receives an "add block ACK (ADDBA) request" should allocate a block ACK (BA) reordering buffer. ADDBA request is the name of the action frame that is used to establish the block ACK agreement. A BA reordering buffer contains several buffers, in which each one is of the MTU for A-MSDU size (e.g., .about.4 Kbytes). This must be done by the recipient station, even when the originator has no intent to merge A-MSDU into A-MPDU. Thus, even where the originator does not send the A-MSDU packets aggregated into an A-MPDU packet, the recipient has allocated the larger MTU size for each buffer in the BA reordering buffer. In such a situation, more than half of the memory allocation in the recipient buffer is wasted. That is, 4000 Kbytes-1500 Kbytes, or 2500 Kbytes, of each buffer is wasted.
Thus, there is a continuing need for a packet aggregation method that is efficient for the recipient while supporting the 802.11n specification.

Communication station and method for communicating aggregate MAC service data units (A-MSDU) under a block acknowledge agreement


Disclosed is an apparatus for controlling a drive transistor of a horizontal deflection apparatus which comprises a comparator; a switching controller which compares a reference voltage coupled to a non-inverting terminal with a signal provided externally through an inverting terminal and removes noise; a switch including a first switch coupled to a constant voltage and a grounded second switch, either the first or second switch being operated according to an output of the switching controller; a diode; a capacitor; a resistor; and a base current supplier. When the constant current, generated by the constant voltage, is provided through the first switch, the constant current is provided to the base terminal of the transistor through the diode, the transistor is turned on, and the capacitor is charged to as much as a forward voltage drop of the diode, and when the first switch is turned off and the grounded second switch is turned on, the transistor is turned off to discharge the capacitor. The present invention supplies a uniform current to the base terminal or discontinues the supply of the uniform current so as to reduce switching loss of the transistor.

(a) Field of the Invention p The present invention relates to a horizontal deflection apparatus. More specifically, the present invention relates to an apparatus for controlling a drive transistor of a horizontal deflection apparatus to reduce switching loss of the drive transistor.
(b) Description of the Related Art
A horizontal deflection apparatus uses horizontal synchronization signals and synchronization to generate sawtooth waves of 15.75 KHz, and provides the sawtooth waves to a horizontal deflection coil in order to scan electron beams of television cathode ray tubes (CRT) or computer monitors in the horizontal direction.
FIG. 1 is a circuit diagram illustrating a conventional horizontal deflection apparatus, and FIG. 2 is a waveform diagram of an equivalent circuit of a controller of a drive transistor. A controller 100 of the drive transistor Q2 is an equivalent circuit of a pulse transformer for providing a base current for the drive transistor Q2.
As shown in FIG. 1, a drive signal to operate a switch Q1 is provided to the switch Q1 from an internal microprocessor. When the switch Q1 is turned on, an inductor current i.sub.LB is increased with the passage of time at a slope of V.sub.B /L.sub.B as shown in FIG. 2 since this circuit adopts a forward converter method. Since carriers in the base layer move in the negative direction, the drive transistor Q2 is turned off according to a base current i.sub.B2 of the drive transistor Q2, and energy is stored in an inductor L.sub.B. At this time, when the carriers in the base layer are removed, the base current i.sub.B2 of the drive transistor Q2 goes into a completely off state, and the base current i.sub.B2 of the drive transistor Q2 becomes zero.
When the switch Q1 is turned off, the inductor current i.sub.LB flows through the base of the drive transistor Q2 in a state decreasing with the passage of time (i.e., at a negative slope) because of the time delay of the inductor L.sub.B. Therefore, the drive transistor is turned on. At this time, after the base current i.sub.B2 of the drive transistor Q2 is provided at a maximum value, the base current i.sub.B2 is then gradually reduced but continuously maintained in an on state.
When the controller 100 of the drive transistor is operated as above, a resonance switch 110 of the horizontal deflection apparatus operates in four operation modes in an equivalent circuit such as that shown in FIG. 3. Waveforms in the four operation modes are shown in FIG. 4.
FIG. 3(a) shows a first operation mode of the resonance switch 110.
In the first operation mode, the drive transistor Q2 is turned on so that a resonance is not generated, and an inductor current i.sub.Ly of a yoke coil L.sub.y is increased from a point t0 to a point t2 in FIG. 4. It is assumed that the current i.sub.Ly flowing through the yoke coil L.sub.y flows through a diode D2 coupled to the drive transistor Q2 in parallel, and that the drive transistor Q2 is turned off.
As shown in FIG. 4, when the diode D2 is turned on at the point t0 and a diode current i.sub.D2 flows, a voltage between a collector and emitter of the drive transistor Q2 becomes zero, and a capacitor Cx in FIG. 1 is charged to generate a capacitor voltage Vx. Therefore, when the drive transistor Q2 is turned on at a zero voltage point t1 (i.e., when the switch Q1 is turned off), a switching loss of the drive transistor Q2 is very low because the switching operation is performed in a zero voltage state.
FIG. 3(b) shows a second operation mode of the resonance switch 110.
As shown, the second operation mode of the resonance switch 110 is performed between the interval t2 and t3. Since the capacitor voltage Vx is provided, the diode D2 is turned off and the current i.sub.Ly of the yoke inductor L.sub.y is increased from a negative direction to a positive direction, and a collector current i.sub.C2 starts to gradually flow through the drive transistor Q2.
At this time, as shown in FIG. 4, a base current i.sub.B2 of the drive transistor Q2 is reduced from a very high value to a very low value in a zero voltage switching state because of a time delay of the inductor L.sub.B in FIG. 1. On the other hand, a collector current i.sub.C2 of the drive transistor Q2 is gradually increased because of the yoke inductor L.sub.y. In the waveform of the base current i.sub.B2 of FIG. 4, a current I.sub.BF represents a forward bias current to drive the drive transistor Q2, and a current I.sub.BR represents a reverse bias current to stop the drive transistor Q2.
The collector circuit i.sub.C2 gradually increases up to a maximum value I.sub.CP, and when the current I.sub.Ly flowing to the yoke coil L.sub.y reaches a maximum value I.sub.LP, the second operation mode stops.
FIG. 3(c) shows a third operation mode of the resonance switch 110.
As shown, the third operation mode of the resonance switch 110, which is performed between an interval t3 and t4 of FIG. 4, starts when the switch Q1 is turned on, that is, when the drive transistor Q2 is turned off. When the drive transistor Q2 is turned off, the collector current i.sub.C2 flowing through the drive transistor Q2 is reduced, and the yoke coil current i.sub.Ly flows through a capacitor Cy coupled to the drive transistor Q2 in parallel.
Therefore, as the capacitor Cy is charged, the voltage at the capacitor Cy steeply increases in a sine wave form, the voltage V.sub.CE2 also increases as a sine wave, and the collector current i.sub.C2 flowing through the drive transistor Q2 steeply reduces. When a drive status is not maximized in this state, that is, if even a small collector current i.sub.C2 flows, subsequent switching loss occurs.
The capacitor Cy is discharged by a serial resonance of the yoke coil Ly and the capacitor Cy, and the voltage at the capacitor Cy reduces in a sine wave form.
FIG. 3(d) shows a fourth operation mode of the resonance switch 110.
As shown, the fourth operation mode of the resonance switch 110 is performed after an interval t4 of FIG. 4. When the current is discharged from the capacitor Cy and the voltage at the capacitor Cy becomes negative, the diode D2 coupled to the capacitor Cy in parallel is turned on to complete the fourth operation mode, and the yoke coil current i.sub.Ly flows through the diode D2, after which the mode returns to the first operation mode.
Characteristics of the switching loss in the vicinity of the point t3 will now be described in detail.
FIG. 5(a) is a diagram illustrating a switching loss under first base driving conditions during operation of a conventional horizontal deflection device, in which a horizontal deflection frequency is not changed but a magnitude of a base current is changed. Here, the solid lines represent reference base driving conditions, and the dotted lines represent the first base driving conditions.
As shown, when the base current i.sub.B2 is reduced from the forward bias base current I.sub.BF to the reverse bias base current I.sub.BR under the reference base driving conditions of the drive transistor Q2, a voltage V.sub.CE2 between the collector and emitter, and the collector voltage i.sub.C2 of the drive transistor Q2 are represented by the solid lines around and after the point t3.
When the reverse bias current I.sub.BR is not sufficiently small after the point t3, an off switching operation of the drive transistor Q2 is not performed quickly so that the collector current i.sub.C2 continues to flow. At this time, since the voltage VCE2 steeply increases at the point t3, switching loss of the drive transistor Q2 occurs.
To prevent this energy loss, when the forward bias base current I'.sub.BF and the reverse bias base current I'.sub.BR are reduced according to the first base driving conditions as shown by dotted lines in FIG. 5(a), the voltage V'.sub.CE2 is increased since the forward bias base current I'.sub.BF for turning on the drive transistor Q2 is small. At this time, the collector current I'C2 is increased to a maximum value before the point t3, thereby resulting in the generation of switching loss.
FIG. 5(b) is a diagram illustrating switching loss under second base driving conditions during operation of a conventional horizontal deflection apparatus. As in FIG. 5(a), the horizontal deflection frequency is not charged but the magnitude of the base current is changed. Here, the solid lines represent reference base driving conditions, and the dotted lines represent the second base driving conditions.
Assuming that, under the second base driving conditions, the forward bias base current I'.sub.BF is greater than I.sub.BF, and the reverse bias base current I'.sub.BR is less than I.sub.BR, since the forward bias base current I'.sub.BF is sufficient to turn on the drive transistor Q2, the voltage V'.sub.CE2 between the collector and emitter is reduced to nearly zero. However, since the base current I'.sub.B2 is greatly reduced before the point t3, the voltage V'.sub.CE2 between the collector and emitter is substantially increased. Therefore, since the collector current I'.sub.C2 in the vicinity of the point t3 is at a maximum, the switching loss is increased.
Therefore, the reverse bias base current I.sub.BR of the controller 100 of the drive transistor Q2 is optimized to suit the characteristics of television sets or monitors. However, since the horizontal deflection frequency of the monitors must be modified to adjust the resolution of the monitors, optimization is very difficult.
FIG. 6(a) is a waveform of the reverse bias base current when the horizontal deflection frequency is changed to a higher frequency.
As shown, when changes in the resolution of the monitor increases the horizontal deflection frequency to therefore change the point where the base current i.sub.B becomes zero (i.e., from the point t3 to t'3), the reverse bias base current I.sub.BR at the point t3 increases to I'.sub.BR at the point t'3.
Therefore, when the reverse bias base current increases over that required to turn off the drive transistor Q2, the drive transistor Q2 is not completely turned off, and switching loss occurs at the point t'3 as a result of the maximum collector current and also the voltage between the collector and emitter.
FIG. 6(b) is a waveform of the forward bias base current when the horizontal deflection frequency is changed to a smaller frequency.
As shown, when changes in the resolution of the monitor decreases the horizontal deflection frequency to therefore change the point where the base current i.sub.B becomes zero (i.e., from the point t3 to t'3), the reverse bias base current I.sub.BR at the point t3 decreases to I'.sub.BR at the point t'3.
Therefore, when the reverse bias base current decreases below that required to turn off the drive transistor Q2, the moment at which the drive transistor Q2 is turned off becomes point t3, which is earlier than the point t'3 at which the base current becomes completely zero. Accordingly, the voltage between the collector and emitter increases before the point t'3 so that switching loss occurs.
Hence, the drive transistor Q2 experiences almost no switching loss through use of zero voltage switching. However, when the drive transistor Q2 is turned off, very heavy switching loss repeatedly occurs. This is particularly the case when the horizontal deflection frequency is changed to adjust the resolution of the monitor.
In case of controlling the drive transistor of the horizontal deflection apparatus such that the horizontal deflection frequency of a color television is uniform or the horizontal deflection frequency of a computer monitor is varied, much heat is generated in the power switching elements when using the conventional methods. To solve this problem, elements having greater current and voltage capacities, or a heat sink are used. However, both of these methods increase overall costs, particularly the use of the heat sink. Also, reliability is not ensured with the use of the heat sink.


An image forming device is disclosed which is provided with a simple lock mechanism for locking the position of the developing units on a rotary frame during toner supply. In the lock mechanism, a solenoid is turned off and a rod is moved downward by a spring so that a second member is rotated counterclockwise and a claw at the end thereof is engaged with a protruding portion of a first member. In this state, a rotary frame driving gear is prohibited from rotating, i.e., the rotary frame is locked. Thus, it is unnecessary to prepare a conventional two-way lock mechanism, and displacement of the rotary frame during toner supply is restrained with a simple structure.

1. Field of the Invention
The present invention relates to an image forming device, and more particularly to an image forming device including a rotary developing device having a plurality of developing units and a rotary frame that maintains the developing units in a circumferential direction in order to place each of the developing units opposite the image bearing member by means of rotation.
2. Background Information
An image forming device utilizing an electrophotographic system includes a photosensitive drum as an image bearing member and other devices located circumferentially around the drum, such as a charger, an exposure device, a developing device, a transfer device, a cleaning device, and so on. In addition, a fixing device is provided downstream of the photosensitive drum in a direction in which the transfer media are conveyed. In this image forming device, first, a surface of the photosensitive drum is uniformly charged by the charger. Then, the photosensitive drum is exposed by the exposure device in accordance with image data so that an electrostatic latent image is formed on the photosensitive drum. The electrostatic latent image is developed by the developing device. In the case of a full color image forming device, four developing units are provided for storing cyan developer, magenta developer, yellow developer, and black developer. The developing units develop the latent image to a toner image with four colors (cyan, magenta, yellow, and black). After that, the toner image is transferred to a transfer medium by the transfer device and then fixed to the transfer media by the fixing device, and the transfer media is finally discharged to a discharge unit. Residual developer remaining on the photosensitive drum is cleaned by the cleaning device.
In the above-mentioned image forming operation, the toner in the toner container is consumed as the development is carried out, and thus it is necessary to refill the toner. There are two systems to compensate for the toner consumed by the image forming operation.
The first system is to fill a certain amount of the toner in the developing unit and replace the developing units when the toner is completely consumed, as shown in Japanese Unexamined Patent Publication No. 2004-45960. In this system, the developing unit and the toner container are formed into a cartridge, so that it is not necessary to supply the toner to the developing unit. Consequently, it is easy to maintain the developing unit.
The second system is to provide a toner container outside of the developing unit so as to supply the toner to the developing unit from the outside, as shown in Japanese Unexamined Patent Publication Nos. 2001-134045 and 10-198149. Recently, as full color image forming devices have been increasingly used by individuals, there have been demands to reduce the size of the image forming device. It is necessary to reduce the size of the developing units in order to reduce the size of the image forming device. In the second system, by providing the toner container outside of the developing unit, the developing unit will be reduced in size.
In the device shown in Japanese Unexamined Patent Publication No. 2004-45960 in which the developing unit and the toner container are formed into a cartridge, it is necessary to place enough toner for about 4,000 sheets of printing in the developing unit in advance, because the toner is not supplied to the developing unit from the outside. As a result, it is difficult to reduce the developing unit in size. Although it is possible to set a toner printing capability to 4,000 sheets or less in order to reduce the size of the developing unit, in that case the cost per one sheet increases. In addition, when the toner is completely consumed, it is necessary to replace the developing units each time. As a result, it increases the burden on the environment.
On the contrary, in a system in which the toner container is provided outside of the developing unit and the toner is supplied to the developing unit from the outside, it is necessary to prepare a member for supplying the toner from the toner container to the developing unit. For example, a plurality of toner supply paths are provided for supplying the toner to each of the developing units in the device shown in Japanese Unexamined Patent Publication No. 2001-134045, and a plurality of toner supply pipes are provided for supplying the toner to each of the developing units in the device shown in Japanese Unexamined Patent Publication No. 10-198149. The toner is supplied to the developing units through the toner supply paths or the toner supply pipes from the toner container.
In a rotary developing device having a plurality of developing units and a rotary frame holding the developing units in a circumferential direction in order to place each of the developing units opposite the image bearing member by means of rotation, it is necessary to advance the toner supply pipe into the developing device in order to supply the toner, and pull the toner supply pipe out from the developing device after the toner supply is finished. Furthermore, in order to stop rotation of the rotary frame when the toner supply pipe is inserted into and pulled out from the developing device, a lock mechanism is provided. The lock mechanism is typically adapted to prohibit rotations both clockwise and counterclockwise. As a result, the lock mechanism generally has a difficult structure.
It is an object of the present invention to provide a simple lock mechanism for locking the position of the developing units during the toner supplying operation in the device which includes a toner container apart from the developing device and a toner supply member for supplying the toner to the developing units.


The knock down shelter and storage structure of the present invention includes a base frame assembly formed by interlocking beams. A vertical wall assembly engages the base frame and includes a plurality of corner uprights. A plurality of intermediate uprights and plurality of wall panels slidably engage the uprights to form an enclosed structure. A roof assembly is formed from a plurality of rafters and a plurality of roof panels that slidably engage the rafters. The roof assembly includes transverse members at the forward and rearward portions of the rafters. The assembly forms a rigid known down structure.

The present invention relates to portable building structures suitable for shelter or secure storage that can be assembled without the use of tools or nails, screws and the like to form a rigid structure and that can be readily dismantled.
Portable building structures that can be readily assembled and dismantled are generally referred to as "knock down structures." These structures are used as temporary enclosures to shelter the user while hunting or fishing, for example, or as vacation cabins and recreational shelters for the home. A particular problem with "knock down structures" is providing a sufficiently rigid structure that can resist high winds and inclement weather while retaining its characteristic of being easily assembled and dismantled. In the prior art structures, rigidity has been increased by providing structural frame members having metallic joint supports, dowel pin connectors and interlocking slots or by fixedly attaching structure support posts to the ground or concrete slab upon which the structure is assembled. The limitations of a knock down structure that is fixedly attached on site to the supporting ground or slab can be readily understood. Portable building structures that utilize metallic joint supports and dowel pins to increase rigidity generally require the use of tools and a large plurality of such supports and pins to assure the construction of a knock down structure that will resist high winds and inclement weather. Thus there remains a need for a knock down building structure of sufficient rigidity to resist adverse environmental elements that can be readily assembled and dismantled without the use of tools and fastener means.

Knock down shelter and storage structure