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排序方式: 共有490条查询结果,搜索用时 15 毫秒
481.
482.
It is well known that the dielectric matrix of air-fireable thick film resistors (TFRs) presently used in hybrid microelectronics and passive components invariably consists of a high-lead silicate glass. However, the current trend in the electronic industry is to restrict and eliminate the hazardous elements viz. lead, cadmium etc. from electronic components. An attempt to develop suitable RuO2-based or pyrochlore ruthenate based Pb-Cd free TFRs has been only partially successful till now. We report here the preliminary results of a study aimed to investigate the feasibility of CaRuO3 perovskite-based lead-free TFRs. Our results showed that sheet resistances higher than 1 kΩ/sq. can be easily achieved in a controlled way, with hot and cold temperature coefficients of resistance (TCR) in the range of 325-580 ppm/°C and 180-500 ppm/°C, respectively. Similarly, the compositions also exhibit negligible piezoresistive effects with gauge factor, GF < 1. Additionally, the resistors do not exhibit negative structural features, like bleeding or devitrification of glass, observed in previous attempts to develop reliable lead-free TFRs.  相似文献   
483.
Journal of Intelligent Information Systems - Tsetlin machines (TMs) are a pattern recognition approach that uses finite state machines for learning and propositional logic to represent patterns. In...  相似文献   
484.
This paper describes the principles, architecture and design details for using the Blender Game Engine in real-time production device emulation. An emulation system for a real material transport and handling production installation was implemented based on this. A prototype of a distributed production control system was run on top of the device emulation system to evaluate feasibility. A cardinal architectural principle is the clear distinction between production controllers and production devices. This principle, applicable through flexible communication middleware, enables the implementation of portable production controllers that execute transparently on either the emulated or the real production system. Production system engineers may take advantage of this approach to develop and gain confidence in complex production control solutions.  相似文献   
485.
486.
This paper investigates the application potential for the technology-push manufacturing technology (TPMT) autonomous industrial mobile manipulation (AIMM), in order to link the conceptual ideas (academia) to actual manufacturing requirements (industry). The approach is based on the proposed TPMT methodology in a comprehensive industrial case study. More than 566 manufacturing tasks have been analyzed according to three main application areas (logistics, assistance, and service) to find their suitability for the AIMM technology. The conducted TPMT analysis shows that AIMM has great potential within the manufacturing industries. More than two thirds of the analyzed manufacturing tasks are solvable with AIMM within the next few years. The AIMM technology, at its current stage, finds most suitable applications within logistics (e.g., transportation and part feeding), moving toward assistance (e.g., (pre)assembly and machine tending), and in the future more service-minded tasks (e.g., maintenance and cleaning). Based on the identified real-world applications, it is possible to raise the AIMM technology to the next levels of industrial maturation, integration, and commercialization.  相似文献   
487.
A two-bed hospital ward with one standing healthcare person and a ceiling-mounted lowimpulse semicircular inlet diffuser is simulated in a full-scale room. Tracer gas is used for simulating gaseous contaminants, and the concentration is measured at different air change rates and different postures of the patients. A textile partition between the beds, which is typical in a hospital ward, is used for protection of the patients in some of the experiments. Three different layouts of return openings are tested. One layout with one opening at the ceiling, another with four openings at the wall opposite to the inlet diffuser, and one with a high location of these four openings. The downward recirculating flow is on average parallel with the partition, and in most cases the partition does not decrease cross-infection. A high location of the four return openings decreases the risk of cross-infection.  相似文献   
488.
The processing of aluminum nitride (AlN) ceramics in aqueous media requires the use of a surface layer to protect the surface of the particles against hydrolysis. This surface layer might influence the densification, affecting the reactions between AlN and sintering additives. The present paper describes a thermodynamic and experimental approach to evaluate the effects of a phosphate-based protecting surface layer on the densification of AlN in the presence of YF3–CaF2 as sintering aids, and to predict the densification behavior during sintering using thermodynamic assessments. Based on thermodynamic calculations and the measured weight loss of the samples during heating to sintering temperature, the chemical reactions occurring during firing were proposed. The proposed reactions were related to the experimental results as well as the final properties of the AlN samples, namely, thermal conductivity, microstructure, secondary phases, and density.  相似文献   
489.
The purpose of this study was to understand the impact of the poly (lactic-co-glycolic acid) (PLGA) molecular behavior in the feed solution on the drug release kinetics of PLGA microparticles prepared via spray drying. The PLGA molecular behavior in the feed solutions were characterized by using tube viscometry, which provides information about the polymer coil radius (Rcoil), the Martin constant (Km), and the overlap concentration (c*). The particle size and the drug surface enrichment were investigated by using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The drug release profiles were characterized by using the USP paddle method and analyzed by using the Crank's diffusion model to calculate the kinetic parameters. Multivariate data analysis using principal component analysis (PCA) was employed to display the relationship between the PLGA molecular behavior, particle properties and the drug release kinetics from the spray dried PLGA microparticles. Rheological studies suggested that an increased molar ratio of a poor solvent (methanol) in the solvent system resulted in a decreased Rcoil, the increase in Km and c*. The higher effective diffusion coefficient of drug calculated by using the Crank's diffusion model was observed in the polymer matrix prepared at an acetone-to-methanol molar ratio of 69:31. The PCA models indicated that the drug surface enrichment and the Km were directly proportional to the drug burst release, while the entanglement index was inversely correlated. Further, the particle size had a less significant impact on the drug burst release. This study implies that the polymer molecular behavior would influence the microscopic connectivity and diffusivity of polymer matrix, which eventually affects the drug release kinetics.  相似文献   
490.
Unlike ambient pressure silicate glasses, some phosphosilicate glasses contain sixfold-coordinated silicon (Si6) units even when prepared at ambient pressure. The variation in the fraction of Si6 with composition remains a topic of interest, both for technological applications of phosphosilicate glasses and for fundamental understanding of the glass structure. In this work, we use statistical mechanical modeling to predict the composition–structure relationships in Na2O–P2O5–SiO2 and CaO–P2O5–SiO2 glasses. This is achieved by accounting for the enthalpic and entropic contributions to the interactions between each pairwise modifier ion and structural unit. The initial enthalpy parameters are obtained based on experimental structural data for binary Na2O–SiO2, CaO–SiO2, Na2O–P2O5, and CaO–P2O5 glasses, which can then be transferred to predict the structure of mixed former glasses. This approach has previously been used to predict the short-range structure of borosilicate and aluminoborate glass systems. However, here we show that the formation of Si6 must be specifically included to make accurate predictions of the composition–structure relationships in phosphosilicate glasses. After incorporating the formation mechanism of Si6 in the statistical mechanics model, we find an excellent agreement between model predictions and experimental structure data for Na2O–P2O5–SiO2 and CaO–P2O5–SiO2 glasses.  相似文献   
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