• 오토저널
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• 제8권2호
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• pp.31-42
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• 1986

The prediction of performance, exhaust emissions and EGR effect is made by the SI engine cycle simulation. In this simulation several models are employed - two zome, thermodynamic combustion, mass fraction burned, heat transfer, chemical equilibrium, chemical kinetics for NOx, laminar flame speed for ignition delay. The chemical species in burned gas considered are 13 species-CO$_{2}$, CO, $O_{2}$, H$_{2}$O, H$_{2}$,OH, H, O, N$_{2}$, NO$_{2}$, N, Ar - and the cylinder pressure, burned and unburned zone temperature and composition of gas are calculated at each crank angle through the compression, ignition delay, combustion and expansion process. To check the validity of the model, experimental study is done for measuring emissions, combustion pressure and engine output. The predicted values for pressure and emissions show qualitative agreement with the measured data and the EGR effect also shows similar tendency.

• 한국정밀공학회지
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• 제17권11호
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• pp.75-80
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• 2000

Recently, there are a great many research for magnetic levitation system. In case electromagnet is operated as the actuator of control system, first of all, we must analysis about an electromagnet. Important parameters of this system are inductance(L) and resistance(R) which are induced from the coil of electromagnet. And attractive force equation is also important. If the load of this system is large, phase delay is caused by self-inductance effect. Because this delay effect cause stability of whole magnetic evitation system to grow worse, a measures to diminish time constant must have been taken. And the linearized attractive force equation which is used at small range of the operating point is compensated to use at larger range, thus the experiment of magnetic levitation system will get a better result.

• Bulletin of the Korean Chemical Society
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• 제21권10호
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• pp.957-958
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• 2000

The addition effect of $CH^3Br$ on the ignition of methane was investigated in the temperature range of 1537-1920 K behind reflected shock waves. The ignition delay times were measured by the sudden increase of pres-sure and OH emission in the $CH_4-O_2-Ar$ system containing small amount of $CH_3Br.$ The delay times of mix-tures with $CH_3Br$ were shorter than those without $CH_3Br.$ The promotion of ignition by $CH_3Br$ was caused by the relative fast decomposition rate in additive. To clarify the addition effect of $CH_3Br$ from the viewpoint of the reaction mechanism, computational analyses were performed in $CH_4-CH_3Br-O_2-Ar$ mixtures.

• Current Optics and Photonics
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• 제2권6호
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• pp.563-567
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• 2018

We propose and experimentally demonstrate a simple tunable photonic microwave band-pass filter with high resolution using a reflective semiconductor optical amplifier (RSOA) and an optical time-delay line. The RSOA is used as a gain medium for generating cross-gain modulation (XGM) effect as well as an optical source. The optical source provides narrow spectral width by self-injection locking the RSOA in conjunction with a partial reflection filter with specific center wavelength. Then, when the RSOA is operated in the saturation region and the modulated recursive signal is injected into the RSOA, the recursive signal is inversely copied to the injection locked optical source due to the XGM effect. Also, the tunability of the passband of the proposed microwave filter is shown by controlling an optical time-delay line in a recursive loop.

• 복식
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• 제66권4호
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• pp.32-44
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• 2016

The purpose of this study is to examine the cognitive responses and the corresponding behavior responses of consumers who have experiences in not being able to buy a product in an online shopping mall due to it being sold-out. Responses were gathered from 526 consumers between the ages of 20 to 40 years residing in a metropolitan area. Each person surveyed had experienced a situation in which a product that they wanted to purchase from an online shopping mall was sold-out. SPSS 18.0 was used to perform frequency analysis, factor analysis, reliability analysis, and regression analysis. The first set of results of this study showed positive responses of quality, discernment, scarcity, but also negative cognitive responses of careless management, manipulation of shopping mall management, and common taste. In negative cognitive responses, sold-out situations caused consumers inconvenience. The second set of results revealed that quality, discernment, and careless management had a significant effect on product replacement (Substitute, S); likewise, factors such as quality, discernment, careless management, manipulation by shopping mall designers, and common taste had a significant effect on the delay of purchasing decisions (Delay, D). Scarcity, careless management, manipulation by shopping mall designers, and common taste also demonstrated significant influence on the incomplete leaving of stores (Incomplete Leave, L1), while discernment, scarcity, careless management, manipulation by shopping mall designers, and common taste had a significant influence on the complete leaving of stores (Complete Leave, L2). Previous studies have examined the behavioral response topics of substitute, delay, and leave. These study results suggest that product sellouts at online shopping malls did not have a solely negative effect on consumers. It actually had a positive effect in terms of discernment, scarcity, and the perception of quality of sold-out products. Furthermore, both positive and negative cognitive responses had various effects on behavioral responses.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제35권3호
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• pp.146-152
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• 2009

Traditional surgical method or injection using filler is performed for soft tissue augmentation. Surgical methods have disadvantage of surgical morbidity. Commercially available injectable materials have the disadvantages such as resorption, short-term effect. repeated application and hypersensitivity. Significant shortcoming of cell therapy using autologous fibroblasts is delay of treatment effect. Chitosan/${\beta}$-glycerol phosphate (GP) solution has thermosensitive property and allows sol-gel transition at physiologic pH and temperature. These properties may resolve the delay of treatment effect. The purposes of this study are to evaluate the viscosity and pH changes of chitosan/${\beta}$-GP solutions and to evaluate the effect of chitosan/${\beta}$-GP solution on fibroblast proliferation and production of collagen. We measured the viscosity and pH as function of temperature, of the solution containing 1:0.7, 1:0.75, 1:0.8 chitosan (1, 10, 100, 700 kDa) /${\beta}$-GP. Fibroblasts from ears of 5 rats were cultured in chitosan/${\beta}$-GP solutions for 3 weeks. Cell proliferation and collagen contents were measured every week with WST (water-soluble tetrazolium salt) assay and Collagen assay respectively. The Results are 1) Chitosan(100 kDa<)/${\beta}$-GP solution (1:0.75) showed sol-gel transition at physiologic pH and body temperature and injectable properties. It will enable to resolve the delay in treatment effect 2) Cell proliferation and total collagen contents of the control group were increased with time. However, these decreased after the 1st week in experimental group 3) Collagen contents in the experimental group are higher than that of control group. Chitosan/${\beta}$-GP solution may provide favorable conditions for cell function

• 대한교통학회지
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• 제19권6호
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• pp.219-227
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• 2001

본 연구에서는 CA(Cellular Automata)규칙을 이용하여, 돌발상황의 영향을 분석할 수 있는 시뮬레이션 모형을 구축하고, 실시간 자료인 VDS 자료와 현장측정 자료를 이용하여 시뮬레이션 모형을 검증하였다. 이렇게 구축된 시뮬레이션 모형을 이용하여, 고속도로상에서 돌발상황이 발생하였을 때의 영향을 분석하였다. 그 결과는 5% 신뢰구간에서 통계적으로 유의함으로 나타났다. 돌발상황의 영향을 분석하기 위해서 돌발상황의 지속시간과 교통량의 변화에 따른 돌발상황의 유형을 분류하였고, 각각의 돌발상황 유형에 따른 영향을 분석하였다. 이때 돌발상황에 의한 영향은 구간 통행시간의 변화와 혼잡 지체시간의 변화를 통해서 분석하였다. 결과에 따르면, 교통량이 적을 때는 교통류가 돌발상황에 의해서 거의 영향을 받지 않았고, 교통량이 증가함에 따라, 돌발상황에 의한 영향이 점점 더 커지는 것으로 나타났다. 또한, 교통량이 2000대/시를 넘어설 때는 돌발상황이 발생하지 않더라도, 교통량의 증가에 따라 혼잡지체가 자연스럽게 발생하는 것으로 나타났고, 돌발상황이 45분 동안 계속될 경우에는 약 425∼722대·시의 지체가 발생하였다.

• 한국수자원학회논문집
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• 제47권9호
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• pp.743-752
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• 2014

함양 지체시간은 강우로부터 지표면을 지나 지하수면으로 도달하는 침투수의 통로 역할을 하는 비포화대를 통과할 때 발생하는 시간지연을 의미한다. 함양 지체시간을 직접적으로 측정하는 것은 불가능하기 때문에 본 연구는 고도와의 단순회귀분석을 이용하여 지체시간에 대한 경험식을 유도하였다. 이를 위하여 제주도 내에 4개의 유역(한천, 강정천, 외도천, 천미천)을 선정하여 총 18개의 관측지점에 대한 지체시간을 산정하였다. 또한 제안된 회귀식을 검증하기 위하여 선형 저수지 이론으로부터 유도된 방정식을 적용하여 구한 지체시간과 본 연구에서 유도된 경험식으로부터 산정된 지체시간을 이용하여 각각 산정한 지하수 함양량을 비교한 결과 상관성이 높은 것을 확인할 수 있었다. 따라서 본 연구에서 유도한 경험식을 이용하여 SWAT모형의 지체시간 매개변수에 적용할 경우 지하수 함양의 공간적 지연효과를 잘 반영할 것으로 판단된다.

• International Journal of Automotive Technology
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• 제7권1호
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• pp.1-7
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• 2006

The ignition delay of a dual fuel system has been numerically investigated by adopting a constant volume chamber as a model problem simulating diesel engine relevant conditions. A detailed chemical kinetic mechanism, consisting of 28 species and 135 elementary reactions, of dimethyl ether (DME) with methane ($CH_{4}$) sub-mechanism has been used in conjunction with the multi-dimensional reactive flow KIVA-3V code to simulate the autoignition process. The start of ignition was defined as the moment when the maximum temperature in the combustion vessel reached to 1900 K with which a best agreement with existing experiment was achieved. Ignition delays of liquid DME injected into air at various high pressures and temperatures compared well with the existing experimental results in a combustion bomb. When a small quantity of liquid DME was injected into premixtures of $CH_{4}$/air, the ignition delay times of the dual fuel system are longer than that observed with DME only, especially at higher initial temperatures. The variation in the ignition delay between DME only and dual fuel case tend to be constant for lower initial temperatures. It was also found that the predicted values of the ignition delay in dual fuel operation are dependent on the concentration of the gaseous $CH_{4}$ in the chamber charge and less dependent on the injected mass of DME. Temperature and equivalence ratio contours of the combustion process showed that the ignition commonly starts in the boundary at which near stoichiometric mixtures could exists. Parametric studies are also conducted to show the effect of additive such as hydrogen peroxide in the ignition delay. Apart from accurate predictions of ignition delay, the coupling between multi-dimensional flow and multi-step chemistry is essential to reveal detailed features of the ignition process.

• 지식경영연구
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• 제22권1호
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• pp.1-19
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• 2021

대규모 병원정보시스템 프로젝트가 계획 대비 지연되는 경우가 종종 발생하고 있다. 따라서 프로젝트 관리 측면에서 일정 지연을 촉발하는 원인을 검토하고 지연 유발 요인들 간 인과관계 분석이 필요하다. 본 연구는 근거이론 방법론을 활용하여 병원정보시스템 개발 프로젝트 사례에 대한 일정 지연 요인을 발견하고 이들 간의 인과관계를 파악하고자 한다. 연구 결과, '비현실적 일정 수립'은 도미노 현상과 같이 전반적인 일정 지연에 영향을 미치고, '기존 시스템 분석 미흡'은 분석 품질의 저하를 야기하는 반면 '서브시스템 통합 인터페이스 부실'은 설계 품질의 저하로 이어졌다. 본 연구는 학술적인 측면에서 프로젝트 지연에 영향을 미치는 요인을 찾아내고 지연 요인들 간의 인과 관계를 분석하였으며, 실무적 관점에서는 System Integration (SI) 기업, 병원, 프로젝트 관리자 입장에서 프로젝트 일정 지연을 최소화할 수 있는 방안을 제시한 점에 의의가 있다.