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排序方式: 共有732条查询结果,搜索用时 62 毫秒
591.
Duhwan Mun Author Vitae Soonhung Han Author Vitae Junhwan Kim Author Vitae Youchon Oh Author Vitae 《Computer aided design》2003,35(13):1171-1179
The current version of STEP standard cannot exchange the parametric information of CAD models. Only pure boundary representations that cannot be parametrically edited are transferable [Geometric Modeling: Theory and Practice (1997)]. There are two approaches for the exchange of design intents such as parameters, features, and constraints. The first is an explicit approach based on constraints between pre-defined parameters and features. The second is a procedural approach based on the sequence of operations issued to construct the models. The authors have previously proposed a macro-parametric approach [International Journal of CAD/CAM 2 (2002) 23], which is a variation of the procedural approach. In this approach, CAD models can be exchanged in the form of macro files, which include the history of modeling commands. To exchange CAD models using the macro-parametric approach, a set of standard modeling commands should be defined. This paper introduces a set of standard commands and explains the process of developing the set. 相似文献
592.
Youngsong Mun 《The Journal of supercomputing》2005,33(1-2):33-52
Multistage Interconnection Networks(MINs) have a number of applications in the areas of computer and communications. The most
widely researched structure among MIN’s is the (l)banyan type network. It has several variations such as buffered banyan,
batcher-banyan, tandem banyan, recirculating banyan and banyan with contention resolution phase. Analytical performance evaluation
is crucial for justifying the merit of the design in different operational conditions. While several analytical models have
been proposed for the performance evaluation of MINs, they are mainly for uniform traffics. Even the models for nonuniform
traffics have several shortcomings such as they only consider output buffered structure or do not consider blocking conditions.
In this paper, the more accurate models than any other ones so far have been proposed for the performance evaluation of multibuffered
banyan-type MIN’s under nonuniform traffic condition is obtained. The accuracy of proposed models are conformed by comparing
with the results from simulation. Firstly, single buffer model is developed. Markov chain is used for the analysis. Multibuffer
model is obtained from single buffer model. Simulation is performed using Discrete Evenet Simulaton(DES) method. As a results,
proposed model proves to be very accurate. 相似文献
593.
Perovskite oxides like SrTiO3 at the nanoscale are of interest for emerging applications,including high-k dielectrics and sensors.However,their synthesis requires long calcination at the elevated temperature,which is a barrier of their application to flexible electronics.Here,an effective laser-assisted sol-gel method to patternably produce SrTiO3 nanoparticles (-100 nm) in selective areas on polyimide substrates (coated with ITO) is introduced.Importantly,the violet-laser power is just 1 W but sufficient to crystallize the material in a short period (a few seconds).Furthermore,developing a flexible device platform using carbon nanotubes (CNT) and SrTiO3 nanoparticles for detection of humidity changes at room temperature is proposed.The sensor platform has both capacitive and resistive sensing abilities.The resistive mode with a lower power usage (about 0.2 μW) is suitable for long monitoring of humidity in the range of 2% RH and above.The capacitive mode with higher sensitivity,faster response/recovery time (1-3 min),and lower detection limit (0.5% RH) can be used for calibration purposes.The performance of the flexible sensor is still maintained after 5000 bending cycles at 1.5-cm radius.Altogether,our synthesis method and the flexible sensor show chances for mass-producing perovskite oxides at low cost for wearable electronics. 相似文献
594.
Flash Light Millisecond Self‐Assembly of High χ Block Copolymers for Wafer‐Scale Sub‐10 nm Nanopatterning
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Hyeong Min Jin Dae Yong Park Seong‐Jun Jeong Gil Yong Lee Ju Young Kim Jeong Ho Mun Seung Keun Cha Joonwon Lim Jun Soo Kim Kwang Ho Kim Keon Jae Lee Sang Ouk Kim 《Advanced materials (Deerfield Beach, Fla.)》2017,29(32)
One of the fundamental challenges encountered in successful incorporation of directed self‐assembly in sub‐10 nm scale practical nanolithography is the process compatibility of block copolymers with a high Flory–Huggins interaction parameter (χ). Herein, reliable, fab‐compatible, and ultrafast directed self‐assembly of high‐χ block copolymers is achieved with intense flash light. The instantaneous heating/quenching process over an extremely high temperature (over 600 °C) by flash light irradiation enables large grain growth of sub‐10 nm scale self‐assembled nanopatterns without thermal degradation or dewetting in a millisecond time scale. A rapid self‐assembly mechanism for a highly ordered morphology is identified based on the kinetics and thermodynamics of the block copolymers with strong segregation. Furthermore, this novel self‐assembly mechanism is combined with graphoepitaxy to demonstrate the feasibility of ultrafast directed self‐assembly of sub‐10 nm nanopatterns over a large area. A chemically modified graphene film is used as a flexible and conformal light‐absorbing layer. Subsequently, transparent and mechanically flexible nanolithography with a millisecond photothermal process is achieved leading the way for roll‐to‐roll processability. 相似文献
595.
Giant Peak Voltage of Thermopower Waves Driven by the Chemical Potential Gradient of Single‐Crystalline Bi2Te3
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Swati Singh Hyeona Mun Sanghoon Lee Sung Wng Kim Seunghyun Baik 《Advanced materials (Deerfield Beach, Fla.)》2017,29(33)
The self‐propagating exothermic chemical reaction with transient thermovoltage, known as the thermopower wave, has received considerable attention recently. A greater peak voltage and specific power are still demanded, and materials with greater Seebeck coefficients have been previously investigated. However, this study employs an alternative mechanism of transient chemical potential gradient providing an unprecedentedly high peak voltage (maximum: 8 V; average: 2.3 V) and volume‐specific power (maximum: 0.11 W mm?3; average: 0.04 W mm?3) using n‐type single‐crystalline Bi2Te3 substrates. A mixture of nitrocellulose and sodium azide is used as a fuel, and ultraviolet photoelectron spectroscopy reveals a significant downshift in Fermi energy (≈5.09 eV) of the substrate by p‐doping of the fuel. The induced electrical potential by thermopower waves has two distinct sources: the Seebeck effect and the transient chemical potential gradient. Surprisingly, the Seebeck effect contribution is less than 2.5% (≈201 mV) of the maximum peak voltage. The right combination of substrate, fuel doping, and anisotropic substrate geometry results in an order of magnitude greater transient chemical potential gradient (≈5.09 eV) upon rapid removal of fuel by exothermic chemical reaction propagation. The role of fuel doping and chemical potential gradient can be viewed as a key mechanism for enhanced heat to electric conversion performance. 相似文献
596.
Jong Ho Won Sung Cik Mun Gi Hwan Kim Hyung Mo Jeong Jeung Ku Kang 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(34)
Hybrid energy storage systems have shown great promise for many applications; however, achieving high energy and power densities with long cycle stability remains a major challenge. Here, a strategy to synthesize high‐tap density anode and cathode structures that yield ultrahigh performance in hybrid energy storage is reported. First, vinyl acetate monomers are polymerized into molecular sizes via chain reactions controlled by the surface free radicals of graphene and metals. Subsequently, molecular‐size polymers are thermally evaporated to construct battery‐type anode structures with encapsulated tin metals for high‐capacity and stratified graphene pliable pockets (GPPs) for fast charge transfer. Similarly, sulfur particles are attached to GPPs via monomeric polymerization, and capacitor‐type hollow GPP (H@GPP) cathode structures are produced by evaporating sulfur, where sublimated S particles yield mesopores for rapid anion movement and micropores for high capacity. Moreover, hybrid full‐cell devices with high‐tap density anodes and cathodes show high gravimetric energy densities of up to 206.9 Wh kg?1, exceeding those of capacitors by ≈16‐fold, and excellent volumetric energy densities of up to 92.7 Wh L?1. Additionally, they attain high power densities of up to 23 678 W kg?1, outperforming conventional devices by a factor of ≈100, and long cycle stability over 10 000 cycles. 相似文献
597.
This article reviews the premises of configural frequency analysis (CFA), including methods of choosing significance tests and base models, as well as protecting α, and discusses why CFA is a useful approach when conducting longitudinal person-oriented research. CFA operates at the manifest variable level. Longitudinal CFA seeks to identify those temporal patterns that stand out as more frequent (CFA types) or less frequent (CFA antitypes) than expected with reference to a base model. A base model that has been used frequently in CFA applications, prediction CFA, and a new base model, auto-association CFA, are discussed for analysis of cross-classifications of longitudinal data. The former base model takes the associations among predictors and among criteria into account. The latter takes the auto-associations among repeatedly observed variables into account. Application examples of each are given using data from a longitudinal study of domestic violence. It is demonstrated that CFA results are not redundant with results from log-linear modeling or multinomial regression and that, of these approaches, CFA shows particular utility when conducting person-oriented research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
598.
Marie-Claude Savoy Pei Mun Woo Pauline Ulrich Adrienne Tarres Pascal Mottier 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2018,35(4):674-685
An LC-MS/MS method for screening 14 aminoglycosides in foodstuffs of animal origin is presented. Its scope includes raw materials and processed ingredients but also finished products composed of milk, meat, fish, egg or fat. Aminoglycosides are extracted in an acidic aqueous solution, which is first recovered after centrifugation, then diluted with a basic buffer and finally purified by molecularly imprinted polymer-solid phase extraction (MIP-SPE). Analytes are detected within 8 min by ion-pair reversed phase LC-MS/MS. Due to the large range of foodstuffs involved, the variability of matrix effects led to significant MS signal variations. This was circumvented by systematically extracting each sample twice, i.e. ‘unspiked’ and ‘spiked’ at the screening target concentration of 50 µg kg?1. The method was validated according to the European Community Reference Laboratories Residues Guidelines giving false-negative and false-positive rates ≤3% for all compounds. Ruggedness of the method was further demonstrated in quality control operations by a second laboratory. The 14 aminoglycosides in water-based standard solutions were stable for up to 6 months when stored at either ?80°C, ?20°C or at 4°C storage temperatures. 相似文献
599.
Heow Pueh Lee Benson Mun Pun Ng Abhishek Vishwanath Rammohan Le Quan Ngoc Tran 《Journal of Natural Fibers》2017,14(1):71-77
Natural fiber based composites are becoming attractive candidates for use in various applications owing to their mechanical and sound absorption properties. It has been proposed that they could potentially replace glass fiber composites owing to their minimized impact on human health and the environment. Though studies have been dedicated to understanding their mechanical properties, few focus on quantifying their sound attenuation behavior. We investigated the sound absorption properties of flax/epoxy composites and found them to be superior to those of glass/epoxy composites. A noteworthy result was that the noise reduction coefficient increased from an average value of 0.095–0.11 for unidirectional flax/epoxy composite and to 0.10 for cross-ply flax/epoxy system. Results suggest that flax/epoxy composites could be less expensive, viable and ecologically superior substitutes for glass-fiber based composites, particularly in applications where sound absorption is important. 相似文献
600.
PFA‐g‐polystyrene sulfonic acid membranes were prepared by simultaneous radiation‐induced graft copolymerization of styrene onto poly(tetrafluoroethylene‐co‐perfluorovinyl ether) (PFA) film followed by sulfonation. The membrane physico‐chemical properties such as swelling behavior, ion exchange capacity, hydration number, and ionic conductivity were studied as a function of the degree of grafting. Thermal as well as chemical stability of the membranes was also investigated. The membrane properties were found to be mainly dependent upon the degree of grafting. The water uptake, ion exchange capacity, hydration number, and ionic conductivity of the membranes were increased, whereas the chemical stability decreased as the degree of grafting increased. The membranes showed reasonable physico‐chemical properties compared to Nafion 117 membranes. However, their chemical stability has to be further improved to make them acceptable for practical use in electrochemical applications. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1–11, 2000 相似文献