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961.
Thermal conductivity, specific heat capacity and complex dielectric constant of PSN ceramic have been measured from 0.1 K up to 100 K. The thermal conductivity increases after poling of the sample but no influence of an applied electric field on the specific heat and the dielectric constant has been detected. Below 0.3 K a strong decreasing of the density of states has been observed.  相似文献   
962.
963.
An edge-coupled PIN photodetector with an InGaAs absorber layer has been designed and fabricated. Values of bandwidth at 1530 nm, with and without bias, have been measured as 50 GHz and 20 GHz, respectively. The external quantum efficiency is as high as 40% using a standard 12 mu m radius lens-ended single-mode fibre.<>  相似文献   
964.
A high degree of mobility, reliability, and efficiency are needed for autonomous exploration of extreme terrain. These requirements have guided the development of the Ambler, a six-legged robot designed for planetary exploration. To address issues of efficiency and mobility, the Ambler is configured with a stacked arrangement of orthogonal legs and exhibits a unique circulating gait, where trailing legs recover directly from rear to front. The Ambler is designed to stably traverse a 30 degree slope while crossing meter sized features. The same three principles have provided many constraints on the design of a software system that autonomously navigates the Ambler through natural terrain using 3-D perception and a combined deliberative/reactive architecture. The software system has required research advances in real-time control, perception of rugged terrain, motion planning, task-level control, and system integration. This paper presents many of the factors that influenced the design of the Ambler and its software system. In particular, important assumptions regarding the mechanism, perception, planning, and control are presented and evaluated in light of experimental and theoretical research of this project.  相似文献   
965.
An X-ray technique for local measurements of the internal residual stress near inclusions in metalmatrix composites (MMCs) is presented. The technique utilizes medium- to high-energy monochromatic X-rays from a synchrotron source and a combination of slits on the entry and exit sides of the sample in order to determine the strains from small volumes deep within the composite sample. The strains of the individual matrix grains are sampled and averaged, allowing for a much improved spatial resolution. An analyzer is used in order to avoid well-known systematic errors related to geometry and stability of the beam. First results are obtained on a model system consisting of a 500 μm continuous W fiber imbedded in an A1 matrix. Two specimens were investigated with typical Al grain sizes of 1 mm and 30 μm. With a gage volume of 10×10×170 μm3, we obtained count rates on the order of 5000 cps and an accuracy in the strain measurements of Δε≤5×10−5. For both specimens, we found no variations of the radial and transverse strain components with the distance to the fiber, indicating either a complete debonding of the system, a very weak interface, or interface deterioration due to chemical reaction. Intragranular strain fluctuations on the order of ε=±10−4 were found to build up close to the grain boundaries. For the specimen with the smaller Al grain size, sampling data from approximately 15 grains at the same distance to the fiber was sufficient for averaging out the intergranular fluctuations. Finally, we observe effects from the conventional metallurgic sample preparation up to 400 μm from the surface, emphasizing the relevance of bulk techniques.  相似文献   
966.
967.
968.
Applications of Walsh functions in communications   总被引:2,自引:0,他引:2  
Communication theory was founded on the system of sine-cosine functions. A more general theory has become known more recently; it replaces the sine-cosine functions by other systems of orthogonal functions, and the concept of frequency by that of sequency. Of these systems, the Walsh functions are of great practical interest since they lead to equipment that is easily implemented by semiconductor technology. Filters, multiplexing equipment, and a voice analyzer/synthesizer have been built successfully for Walsh functions. Some interesting applications of electromagnetic Walsh waves have been found theoretically.  相似文献   
969.
Zusammenfassung Es wird eine gegenüber anderen Verfahren in Auftrennungskapazität und Schnelligkeit verbesserte Methode zur Bestimmung von Lysinoalanin (LAL) beschrieben, die universell zur Untersuchung von Lebensmitteln anwendbar ist. Nach entsprechender Probenaufbereitung und Freisetzung des Lysinolanins durch salzsaure Hydrolyse wird das Eiweißhydrolysat mit Natronlauge/Natriumcitratpuffer direkt neutralisiert. Die Auftrennung erfolgt im Aminosäureanalysator durch ein basisches Kurzzeitprogramm (Citrat-Elutionspuffer pH 4,50/0,61 nNa+, 60 °C, LAL-Elutionszeit 55 min) mit Ninhydrinnachweis. Damit kann LAL in fast allen Lebensmitteln ohne nennenswerte Interferenzprobleme bestimmt werden; auch die in manchen Lebensmitteln, vor allem in erhitzten Milchprodukten, üblichen relativ hohen Aminozucker-, Fructoselysin- und Lactuloselysin-Konzentrationen stören die Bestimmung des LAL nicht. Hinsichtlich LAL-Absorption an Huminstoffe, Wiederfindung und Nachweisgrenze ist zwischen kohlenhydratreichen Lebensmitteln und reinen Proteinkomponenten zu unterscheiden. Je nach Probenmatrix ergibt sich eine Nachweisgrenze von 10–40 ppm im Eiweiß. Genaue Bestimmungen können bis zu 80 ppm LAL im Eiweiß durchgeführt werden, die minimale nachweisbare LAL-Menge beträgt bei höchster Empfindlichkeit 10 ng LAL.
Improved method for determination of lysinoalanine in food
Summary A faster method for the determination of lysinoalanine (LAL) was developed which is universally applicable to all kinds of food products and shows a better ability to separate LAL from interference substances. After appropriate sample preparation and liberation of protein bound LAL by acid hydrolysis the protein hydrolysate is directly neutralized with sodium hydroxide/sodium-citrate-solution. LAL is separated by means of an automatic amino acid analyzer with a special short time program for basic amino acids (sodium citrate buffer pH 4.50/0.61 nNa+, 60°C, LAL-elution after 55 min) and detected colorimetrically with ninhydrin. There are no interference problems with high concentrations of amino sugars, fructoselysine and lactuloselysine which occur to a considerable degree particularly in heated milk products. As for LAL-absorption on humin substances, recovery and detection limit, there is a difference between pure protein compounds and samples rich in carbohydrates. Depending on the type of sample matrix detection of 10–40 ppm LAL in protein is possible. Exact quantitative determination is limited to 80 ppm LAL in protein. The lowest amount of LAL that can be detected is 10 ng.


Herrn Prof. Dr. Ing. Dr. h.c. mult. Helmut Zahn in Verehrung zum 65. Geburtstag gewidmet  相似文献   
970.
European Food Research and Technology - A highly sensitive fluorometric method for simultaneous determination of lysinoalanine (LAL) anddl-2,3-diaminopropionic acid (DAP) was developed. After acid...  相似文献   
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