• 산경연구논집
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• 제8권5호
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• pp.7-13
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• 2017

Purpose - The purpose of this paper is to analyze the relationship between the real exchange rate and the output, which is based on the macroeconomic equilibrium theory in China. Its aim will be to verify whether the change in the real exchange rate has a significant effect on the output or not. Research design, data, and methodology - This study endeavors tries to investigate the correlation among economic variables under the macroeconomic market (the commodity market and the money market) equilibrium. So, time-series data from 1990 to 2016 is applied to establish a vector auto-regression (VAR) model so as to perform an empirical analysis. Results - The empirical results reveal that an increase in the real exchange rate will result in an increase in the output in the short run. However, the empirical results also indicate that this kind of mechanism cannot work in the long run. Conclusions - The effect of a decrease of real exchange rate on output is significant in the short run. Also, this paper suggests that the total supply and the total demand can promote economic growth. The fiscal and money policy play a significant role in economic growth in China as well.

• Tribology and Lubricants
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• 제17권5호
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• pp.380-385
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• 2001

In nuclear power steam generators, high flow rates can induce vibration of the tubes resulting in fretting wear damage due to contacts between the tubes and their supports. In this paper the fretting wear tests and the sliding wear tests were performed using the steam generator tube materials of Inconel 600 and 690 against STS 304. Sliding tests with the pin-on-disk type tribometer were done under various applied loads and sliding speeds at air environment. Fretting tests were done under various vibrating amplitudes and applied normal loads. From the results of sliding and fretting wear tests, the wear of Inconel 600 and 690 can be predictable using the work rate model. Depending on normal loads and vibrating amplitudes, distinctively different wear mechanisms and often drastically different wear rates can occur. It was found the results that the wear coefficients for Inconel 600 and 690 were 262.3$\times$10$\^$-15/Pa$\^$-1/ and 209.2$\times$10$\^$-15/Pa$\^$-1/, respectively. This study shows that Inconel 690 can provide much better wear resistance than Inconel 600 in air.

• Journal of Communications and Networks
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• 제9권3호
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• pp.330-341
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• 2007

This work analyzes the performance of the parallel packet switch (PPS) with a sliding window (SW) method. The PPS involves numerous packet switches that operate independently and in parallel. The conventional PPS dispatch algorithm adopts a round robin (RR) method. The class of PPS is characterized by deployment of parallel low-speed switches whose all memory buffers run more slowly than the external line rate. In this work, a novel SW packet switching method for PPS, called SW-PPS, is proposed. The SW-PPS employs memory space more effectively than the existing PPS using RR algorithm. Under identical Bernoulli and bursty data traffic, the SW-PPS provided significantly improved performance when compared to PPS with RR method. Moreover, this investigation presents a novel mathematical analytical model to evaluate the performance of the PPS using RR and SW method. Under various operating conditions, our proposed model and analysis successfully exhibit these performance characteristics including throughput, cell delay, and cell drop rate.

• 한국시뮬레이션학회논문지
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• 제29권4호
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• pp.95-109
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• 2020

이 논문에서는 자동차 차체 조립라인과 같은 제조시스템을 설계할 때, 설비투자비용과 같은 다양한 비용요소를 고려하여 최적 배치안을 결정하는 문제를 다룬다. 시스템의 성능 평가에 필요한 생산율 재공품 재고 수준을 추정하기 위해서는 시뮬레이션 실험 결과를 기반으로 하는 메타모델 방법론을 사용하였다. 최적화 문제의 목적함수는 목표생산율을 만족시키는 최소비용으로 정하였는데, 비용요소로는 로봇, 버퍼, 운송장비에 대한 투자비용을 고려하였고, 운영비용으로는 재공품 재고비용을 포함시켰다. 최적화 문제를 풀기 위해서는 하모니 탐색방법론을 사용하였다.

• KSBB Journal
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• 제13권6호
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• pp.730-734
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• 1998

An이ew식과 Aiba삭을 조합하여 에탄올 생산단주인 Saccharomyces cerevisiae ATCC 24858의 비성장속도를 당농도와 에탄올 농도의 함수로 표현하였다. 기침의 저해영향을 받지 않는 최대 당농도 $S_m$은 150 g/L이며 기질의 저해영향은 기질농도 S와 $S-S_{max}$항의 함수로 표현되었다. 최대 비성장 속도 ${\mu}max 는 0.49 hr^{-1}, Monod상수 K_s$는 19 g/L, Andrew식의 기질저해상수 $K_1$는 139 g/L이였다. 또한 비성장속도에 영향을 마치지 앓는 최대알콜농도 Pm이 존재하였으며 그 값은 2 g/L 이였다. 따라서 Aiba식에서 비성장속도에 영향을 미치는 에탄올 농도항은 P-Pm으보 표현되었다. 본 연구의 알코올생산균주에 대한 비성장속도의 완성된 수식은 디음과 같으며 이 수식에 위한 계산값은 평균오차 6% 내외의 범위에서 실험값과 일치하였다.

• 한국환경보건학회지
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• 제42권2호
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• pp.92-101
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• 2016

Objectives: Outdoor workers are exposed to thermally stressful work environments. In this study, heat stress indices for harbor workers in summer were calculated to evaluate thermal comfort based on a human heat balance model. These indices are Physiological Subjective Temperature (PST), Dehydration Risk (DhR), and Overheating Risk (OhR) according to respective stage of cargo work in a harbor. In addition, we constructed a forecast system to provide heat stress information. Methods: Thermophysiological indices in this study were calculated using the MENEX model (i.e. the human heat balance model), which used as inputs the meteorological parameters, clothing insulation, and metabolic rate for each stage of cargo work in the harbor of Masan over the course of seven days, including a four-day heat wave. The forecast heat stress information constructed for Masan harbor was based on meteorological data supported by the Dong-Nae Forecast from the KMA (Korea Metrological Administration) and other input parameters. Results: According to higher metabolic rate, thermophysiological indices showed a critical level. In particular, PST was evaluated as reaching the 'Very hot' or 'Hot' level during all seven days, despite the heat occurring over only four. It is important in a regard to consider the work environment conditions (i.e. labor intensity and clothing in harbor). On a webpage, the forecast thermophysiological indices show as infographics to be easily understand. This webpage is comprised of indices for both current conditions and the forecast, with brief guidance. Conclusion: Thermophysiological indices show the risk level to health during a heat wave period. Heat stress information could help to protect the health of harbor workers. Further, this study could extend the applicability of these indices to a variety of outdoor workers in consideration of work environments.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2002년도 추계 학술발표회 논문집
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• pp.103-108
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• 2002

We consider an estimation of discontinuous variance function in nonparametric heteroscedastic random design regression model. We first propose estimators of a change point and jump size in variance function and then construct an estimator of entire variance function. We examine the rates of convergence of these estimators and give results on their asymptotics. Numerical work reveals that the effectiveness of change point analysis in variance function estimation is quite significant.

• 대한기계학회논문집B
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• 제40권9호
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• pp.569-576
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• 2016

본 연구는 HSDI 디젤 엔진의 연소 성능 향상을 위해 연료 분사 타겟팅의 최적화를 수치 해석적으로 연구하였다. 연구에 적용된 연소모델은 ECFM-3Z모델을 사용하였고, 해석에 필요한 엔진 부하 및 연료의 타겟팅은 분사량, 분사각도, 분사시기를 변경하여 해석한 실린더압력, 열 발생률, 배기 배출물 특성의 결과를 비교 분석하여 연구하였다. 연구결과, 분사시기와 분사각도에 따라 연료가 피스톤 보울 안쪽으로 많이 유입될수록 열 발생률의 증가로 인하여 $NO_x$는 증가하였고, CO, Soot은 연소성능의 증진으로 감소하는 것을 확인할 수 있었다. 또한, 분사시기가 진각될수록 균일 혼합기 형성시간이 충분하여 연소성능이 증진되고, 실린더압력은 증가하였다.

• 한국전문물리치료학회지
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• 제23권4호
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• pp.71-80
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• 2016

Background: Functional capacity evaluations (FCEs) are designed to systematically assess the capacity to perform work-related tasks and to determine worker's ability to return to the previous job following work-related injuries. These evaluations may be rated either by clinician or worker. There has been a lack of consensus between the two scoring methods. Objects: This study aimed: 1) to confirm if the data are fit to the Rasch rating scale model and 2) to investigate the item-level concordance rate between the ratings of clinician and injured worker of the FCE. Methods: A cross-sectional study was conducted with a sample (n=124) of a rehabilitation program with the Occupational Rehabilitation Data Base for workers with low back pain. The functional capacity evaluation at admission and discharge was administered to clinicians and workers. The data were analyzed using both classical test theory-based Pearson's r and intra-class coefficient followed by item-level analysis with Rasch rating scale model. Results: All items of the FCE, except sitting items rated by clinician at admission and handling items rated by both clinician and worker throughout admission and discharge, were acceptable fit statistics with minor out of ranges for a misfit criterion. This may indicate that the items of the FCE overall fit to the Rasch rating scale model. Few problematic items responding differently to clinician and worker both at admission and discharge were detected with the differential item functioning analysis despite the excellent concordance rate using the two conventional statistics-sitting and handling items at admission and handling item at discharge. Conclusion: The item-level speculations using Rasch analysis of the FCE demonstrate that the ratings of clinician and self ratings of worker were psychometrically acceptable though there was an apparent discrepancy between the raters both at admission and discharge.

• 대한산업공학회지
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• 제29권2호
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• pp.135-144
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• 2003

Traffic performance in a microcellular system is much more affected by cell dwell time and channel holding time in each cell. Cell dwell time of a call is characterized by its mobility pattern, i.e., stochastic changes of moving speed and direction. Cell dwell time provides important information for other analyses on traffic performance such as channel holding time, handover rate, and the average number of handovers per call. In the next generation mobile communication system, the cell size is expected to be much smaller than that of current one to accommodate the increase of user demand and to achieve high bandwidth utilization. As the cell size gets small, traffic performance is much more affected by variable mobility of users, especially by that of pedestrians. In previous work, analytical models are based on simple probability models. They provide sufficient accuracy in a simple second-generation cellular system. However, the role of them is becoming invalid in a picocellular environment where there are rapid change of network traffic conditions and highly random mobility of pedestrians. Unlike in previous work, we propose an improved probability model evolved from so-called Random walk model in order to mathematically formulate variable mobility of pedestrians and analyze the traffic performance. With our model, we can figure out variable characteristics of pedestrian mobility with stochastic correlation. The above-mentioned traffic performance measures are analyzed using our model.