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This paper deals with a study on the digital to analog converters using the R-2R resister ladders and the transister switches. Most of the converters use technique of the successive approximation analog to digital converters for the serial-parallel methods. This system is composed of threshold logic and storage circuits, and parallel D/A converters. The characteristics of the system is discussed. And the absolute errors of the system are described and investigated.
The new forming method which uses vibratiry powder packing followed by infiltration of binder solutions, Pressureless Powder Packing-Forming Method, was applied to the manufacturing of SiC/C composites. From the result of vibratory powder packing and binder infiltration experiment with various particle sizes, the abrasive SiC powder of which mean size is 40㎛ was selected because of its high packing density and no agglomeration in this forming method. Uniform green bodies with narrow pore size distribution and complex shapes could be easily formed by this new forming method. It was found that amorphous carbon was pentrated into green bodies by the impregnation-carbonization process. As a result, this forming method can be applied to the fabrication of SiC/C composite.
The Pressure loss due to leakage flow is directly related to the tip clearance size of centrifugal impeller. The performance and the pressure distribution along the shroud casing are measured by using pressure transducer system for unshrouded centrifugal compressor at different size of tip clearance. The characteristic curves With respect to the size of tip clearance are presented as one curve regardless of rotational speed. As the size of tip clearance increases form 0.5mm through 2.0 mm, the values of pressure coefficient of characteristic curves decrease linearly due to the increase of leakage loss. The reduction rate of static pressure coefficients per 1 mm tip clearance is 0.04∼0.047, and the reduction rate per c/b₂is 0.28 evenly. The pressure coefficient for radial direction on the shround casing surface is presented as one curve regardless of rotational speed and decreases linearly. The reduction rate of pressure coefficient is nearly identical to that of characteristic curves.
In the system using one sensor, to describe accurate situation or conclude from information of one source in difficult. Moreover, sensor noise degrades the belief of decision. Multisensor information system, however, can increase the belief of date by imploying more than one source of information simultaneously. Another advantage of the system is that it can accomplish its task with other sources of information when one source malfunctions. In this paper, we implemented data association methods to identity moving flight targets using distance, probability theory, Dempster-Shafter theory for the low level process in the information fusion system. Data association is to classify information from various sources into data groups depending for the same flight object. Times and errors of these data association methods are analyzed.
In the system of ??, hydroxyapatie was synthesized through the sol-gel process. In the system, the effect of the change of ??, addition of the acid or base, the change of Ca/P and the characterization of synthesized powder were studied. In the system of ??, monophase of hydroxyapatite was synthesized at 800℃. In the three cases of r>6.7, addition of the base and no addition of the base or acid, the second phase was remained. But in the case of addition of the acid with r=3.3, 1.67, monophase of hydroxyapatite was synthesized. Addition of the NH₄OH, hydroxyapatite peak was remarkable at 600℃ by the thermal decomposition of NO₃, but for CH₃COOH, hydroxyapatite peak was obtained at 800℃ due to the remained acetate ligand. In the result of change of Ca/P mole ratio, for Ca/P=1.5, the growth of β-TCP was remarkable, for Ca/P=2.0, CaO peak intensity grew with heat treatment but, for Ca/P=1.67, monophase of hydroxyapatite was synthesized.
Response surface methods for structural reliability analysis are widely adopted due to the computational efficiency. However, the computational amount depends on number of random variables selected to model the randomness inherent in structures as well as loadings acting on. In this study, random field mesh models are used to models are used to model spatial random distribution of structural design variables, such as material properties, section properties, etc. The sensitivity analysis has been performed to select proper size of random field division with a selected auto-correlation function model of spatial randomness. In addition random variable sensitivity analysis has been also studied to improve the computational efficiency by disregarding the random variables of low sensitivities on structured reliability.
Fracture machines does work for concrete, provided that one uses a proper, nonlinear form of fracture mechanics in which a finite nonlinear zone at fracture front is being considered. The fracture process zone is a region ahead of a traction-free crack, in which two major mechanisms, microcraking and bridging, play important rules. The development of model of fracture process zone is most important to describe fracture phenomena in concrete. The toughness due to bridging is dominant compared to the toughness induced by the microcracking, so that the bridging is the dominant mechanism governing the fracture process of concrete. In this paper the bridging zone, which is a part of extended macrocrack with stresses transmitted by aggregates in concrete, is modelled by a Dugdale-Barenblatt type model with linear tension-softening curve. Finite element techniques are shown for implementation of the model for the analyses of crack growth in concrete.
The heat generation mechanism of angular contact ball bearing are analyzed. The heat generation rate and ball temperature of angular contact ball bearing are calculated with respect to the various shaft speed, load and lubrication method. The analysis is focused mainly on the predominant sources of heat generation which are spin-moment, gyro-moment, torque due to applied load and viscous friction torque. The viscosity of lubricant is assumed to be a function of the temperature only and the contact between ball and race is assumed to be elastic. Lumped capacitance method is adopted to compute ball temperature. Effective load is calculated iteratively considering the rate of ball expansion due to the temperature rise.
에탄올의 효율적 농축을 위해 일반 역삼투 공정 및 향류식 역삼투 공정을 적용하여 막모듈 다단 농축공정과 이에 대한 수치해석을 수행하였다. 농축실험 결과, OSRO공정의 RO공정의 농축도보다 최대 1.5배의 상승 효과를 나타내었으며, 농축도는 적용압력과 단수에 비례하여 증가하였다. 다단 농축공정에 대한 수치해석 결과, OSRO공정이 RO공정보다 실험치에 근접하는 바, 각 단을 통과하는 농축액에 의한 높은 삼투압치를 OSRO공정에서 효과적으로 감소, 완화시킬 수 있음을 알 수 있었다. Reverse Osmosis(RO) Process and Counter-Current Osmotic Sink Reverse Osmosis(OSRO) Process were applied to effective ethanol concentration in multiple stage type. Degree of ethanol concentration from OSRO Process was 1.5 times as large as that from RO Process and increased in proportion to applied pressure and stage number values. Experimental results of degree of ethanol concentration from the OSRO Process were closer to numerical results of that than from RO Process. Consequently, it was possible for the high osmotic pressure drop occurred by concentrated ethanol solution through each membrane module stage to be effectively decreased under OSRO Process.
This paper describes a linear address generation unit for the superscalar YS6 microprocessor. The superscalar YS6 microprocessor with A-pipe and B-pipe can execute 2 instructions per clock. The linear address generation unit consists of a segmentation unit and a SDCache unit. The segmentation unit and the SDCache unit of YS6 microprocessor speed up the linear address generation process by using the following techniques. The segmentation unit can generate two linear addresses per clock by using multiport register files and 4-input adders and support two concurrent stack operations per clock. It takes 9 clocks to execute a macroinstruction, 'Mov Sreg, reg', in previous architectures. However, YS6 processor with SDCache unit executes this instruction in 2 clocks. The SDCache unit solves cache consistency problem with main memory by using the Subset protocol. This unit is described with Verilog HDL (Hardware Description Language) and its functional operation is verified.