• 한국경영과학회지
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• 제27권1호
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• pp.107-117
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• 2002

The ever-glowing demands for more responsiveness and more flexibility in manufacturing generate greater expectation for the AGV system. So far. a significant amount of research has been carried out to fulfill those requirements. However, the dynamic characteristics of manufacturing systems make it hard to solve the problem analytically. In this paper, the AGV system is analyzed in the production environments which adopt a cycle time to produce materials. The use of the cycle time could eliminate much of uncertainty Inherent In the manufacturing process so that it is possible to build the deterministic model for the AGV systems, which eventually Produce better results on the important issues such as AGV dispatching, determination of the number of AGVs, and empty vehicle travel time.

• Biotechnology and Bioprocess Engineering:BBE
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• 제8권6호
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• pp.349-353
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• 2003

The physiological characteristics of cultures of very high cell mass (e.g. 10g cell mass/L), termed“ultrahigh cell density cultures”is reviewed. A close relationship was found between the length of the optical path (OP) in flat-plate reactors and the optimal cell density of the culture as well as its areal (g m$\^$-2/ day$\^$-1/) productivity. Cell-growth inhibition (GI) unfolds as culture density surpasses a certain threshold. If it is constantly relieved, a 1.0cm OP reactor could produce ca. 50% more than reactors with longer OP, e.g. 5 or 10cm. This unique effect, discovered by Hu et al. [3], is explained in terms of the relationships between the frequency of the light-dark cycle (L-D cycle), cells undergo in their travel between the light and dark volumes in the reactor, and the turnover time of the photosynthetic center (PC). In long OP reactors (5cm and above) the L-D cycle time may be orders of magnitude longer than the PC turnover time, resulting in a light regime in which the cells are exposed along the L-D cycle, to long, wasteful dark periods. In contrast, in reactors with an OP of ca. 1.0 cm, the L-D cycle frequency approaches the PC turnover time resulting in a significant reduction of the wasteful dark exposure time, thereby inducing a surge in photosynthetic efficiency. Presently, the major difficulty in mass cultivation of ultrahigh-density culture (UHDC) concerns cell growth inhibition in the culture, the exact nature of which is awaiting detailed investigation.

• Journal of Sport and Applied Science
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• 제2권1호
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• pp.25-38
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• 2018

One of the largest and fastest growing segments of the tourism industry, sport tourism refers to travel to play sports, watch sports, or to visit a sport attraction including both competitive and non-competitive activities. In this respect, cycling can be considered as not only a form of physical exercise but also a form of tourism in which cycling is a usual tourism-related activity, heading to a particular destination. The purpose of this study is to examine how demographical differences of cycle tourists are related to the quality of their life. An online survey was conducted and data was analyzed using frequency, reliability, and one - way ANOVA using SPSS 22.0. First, we found that there was no significant difference on the quality of physical life based on demographical characteristics. Second, the analysis of the relationship between demographical characteristics and the quality of mental life showed that income level affects their quality of mental life. Third, the analysis of the relationship between socio demographic characteristics and the quality of social life showed that marital status affects the quality of social life. Fourth, no statistically significant difference was found between the demographical characteristics and the quality of environmental life. Further implications were discussed.

• 대한교통학회지
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• 제25권3호
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• pp.19-28
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• 2007

국내 일반국도는 고속도로와 함께 도시 간을 연결하는 이동성 기능중심의 도로로 고속도로의 우회도로로써의 성격도 함께 가지고 있다. 그러나 최근 국내 현황을 살펴보면 유 출입이 완전히 통제된 수준의 도로에서부터 신호교차로가 빈번하게 설치되어 시가화 된 수준의 도로까지 다양한 형태로 나타난다. 일반적으로 일반국도의 구간 통행속도에 미치는 영향분석을 위해 주로 사용되는 변수로는 도로의 기하구조와 교통상황 등이 있는데, 본 연구에서는 이 중에서 신호등에 의한 속도영향을 살펴보았다. 그 결과 일반국도의 통행속도에 가장 크게 영향을 미치는 요인은 신호등 설치밀도였으며, 신호등 설치밀도가 0.3개/km 이하에서는 일정속도를 유지하고 0.7개/km까지는 급격히 감소하다가 이후에는 속도가 낮게 안정화되었고, g/C=0.6은 0.8에 비해 $3{\sim}9km/h$로 감속되었다. 교통량 수준별로는 신호등 설치밀도가 미치는 영향이 거의 유사한 것으로 나타났다.

• 대한교통학회지
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• 제28권3호
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• pp.19-28
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• 2010

국내의 자전거도로는 대체로 주변 토지이용시설 특성을 고려하지 않은 채 계획되고 있다. 이와 같이 획일화된 도로계획은 효율적이지도 못할뿐더러 안전과 이용편리에 있어서 최적의 환경을 제공할 수가 없다. 따라서 본 연구는 보다 안전하고 편리한 자전거도로 이용환경 구축을 목적으로, 자전거도로 유형에 대해 물리적 시설측면의 분류를 시도하였고, 토지이용시설 이용자의 통행특성을 조사 분석하였다. 카이제곱 독립성검정을 통해서 토지이용시설 간에 통행특성의 차이가 있음을 확인했고, 군집분석과 자전거도로 유형 결정기준을 통해 해당 토지이용시설에 적합한 자전거도로 유형을 제시하였다.

• Clinical and Experimental Reproductive Medicine
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• 제39권3호
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• pp.95-106
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• 2012

It has been revealed that multiple cohorts of tertiary follicles develop during some animal estrous cycle and the human menstrual cycle. To reach developmental competence, oocytes need the support of somatic cells. During embryogenesis, the primordial germ cells appear, travel to the gonadal rudiments, and form follicles. The female germ cells develop within the somatic cells of the ovary, granulosa cells, and theca cells. How the oocyte and follicle cells support each other has been seriously studied. The latest technologies in genes and proteins and genetic engineering have allowed us to collect a great deal of information about folliculogenesis. For example, a few web pages (http://www.ncbi.nlm. nih.gov; http://mrg.genetics.washington.edu) provide access to databases of genomes, sequences of transcriptomes, and various tools for analyzing and discovering genes important in ovarian development. Formation of the antrum (tertiary follicle) is the final phase of folliculogenesis and the transition from intraovarian to extraovian regulation. This final step coordinates with the hypothalamic-pituitary-ovarian axis. On the other hand, currently, follicle physiology is under intense investigation, as little is known about how to overcome women's ovarian problems or how to develop competent oocytes from in vitro follicle culture or transplantation. In this review, some of the known roles of hormones and some of the genes involved in tertiary follicle growth and the general characteristics of tertiary follicles are summarized. In addition, in vitro culture of tertiary follicles is also discussed as a study model and an assisted reproductive technology model.

• 한국정밀공학회지
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• 제24권4호
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• pp.57-67
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• 2007

Laser surface hardening technologies have been used to improve characteristics of wear and to enhance the fatigue resistance fur mold parts. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser surface hardening for the case of SKD61 steel. CW Nd:YAG laser is selected as the heat source. The optical lens with the elliptical profile is designed to obtain a wide surface hardening area with a uniform hardness. From the results of the experiments, it has been shown that the maximum average hardness is approximatly 780 Hv when the power, focal position and the travel of laser are 1,095 W, 0mm and 0.3 m/min, respectively. In samples treated with lower scanning speeds, some small carbide particles appear in the interdendritic regions. This region contains fine martensite and carbide in proportions which depend on the local thermal cycle.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1542-1547
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• 2007

Laser surface treatment technologies have been used to improve characteristics of wear and to enhance the fatigue resistance for mold parts. The optical lens with the elliptical profile is designed to obtain a wide surface hardening area with a uniform hardness. The objective of this research work is to investigate the influence of the process parameters, such as power of laser and defocused spot position, on the characteristics of laser surface treatment for the case of SKD61 steel and SCM4 steel. From the results of the experiments, it has been shown that the maximum average hardness is approximatly 700${\sim}$780 Hv when the power, focal position and the travel of laser are 1,095 W, 0mm and 0.3 m/min, respectively. In samples treated with lower scanning speeds, some small carbide particles appear in the interdendritic regions. This region contains fine martensite and carbide in proportions which depend on the local thermal cycle.

• 한국정밀공학회지
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• 제20권7호
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• pp.44-55
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• 2003

The Nd:YAG laser process is known to have high speed and deep penetration capability to become one of the most advanced welding technologies. This paper describes the machining characteristics of SM45C carbon steel welding by use of an Nd:YAG laser. In spite of its good mechanical characteristics, SM45C carbon steel has a high carbon contents and suffers a limitation in the industrial application due to the poor welding properties. The major process parameters studied in the present laser welding experiment were position of focus, travel speed and laser power. Optical microscope and SEM were used to investigate the microstructures of the welded zone. The experimental results showed that penetration depth of the welding process increases with laser power. Both the microstructural investigation and the theoretical calculations indicated that materials undergoes a very high heating and cooling cycle during welding process. It was also found that the austenite nucleation takes place at the initial stage and the completion temperature of austenite transformation is much higher than in the case of the arc welding.

• 한국농공학회지
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• 제17권3호
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• pp.3885-3893
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• 1975

This work was intended to study the cutting graph and vibratory phenomina of a newly developed mower which may be suitable for mowing agricultural product having large and hard stems like corn and sugar beet. The system consists of cutter-bar having Curvilinear-translation motion, which attached to drag-crank mechanism. The motion of equation developed for experimental vibratory system which equipped with the cutter-bar system was established and the parameters defining the system's vibratory motion were experimentally determined. The optimum balancing weight for the cutter-bar am vibratory characteristics of the cutter-bar for various counterweight were analyzed to provide the design and operational conditions. The results of the study are summarized as follows; (1) The cutting graph by the new cutter-bar system depends upon the magnitude of ratio of forward travel(Vm) to crank speed (R$\omega$); The cutting pitch for Vm/R$\omega$ 1 (whole cycle cutting) and Vm/R$\omega$=2/$\pi$ (a half cycle cutting) are 2$\pi$ Vm and 4R, respectively. (2) The experimental vibratory system had been proved to function adequately so that it can be used in determining the required counterweight to minimize the vibratory motion of cutter-bar. (3) Experimentally determined counterweight to give the least vibratory motion was a little greater than the theoretically determined one. With the optimum counterweight it was possible to reduce up to about 87% of the amplitude without counterweight, which may be considered to be within safe operational region. (4) To avoid the actual operation of the cutter-bar at resonance which occured in low frequency ratio, it was considered that the rotational speed of the crank for a specific design of mower should be determined separately in connection with the desired cutting graph.