• 정보과학회 논문지
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• 제44권3호
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• pp.314-322
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• 2017

대규모 다중 사용자 온라인 롤플레잉 게임 유저들은 시나리오를 따라 주어진 임무들을 수행하며 최고 레벨을 향해 캐릭터를 성장시킨다. 최고 레벨 유저를 보유하는 것이 온라인 게임의 성공적 운영에 중요함에도 불구하고 이들에 대한 연구는 크게 이루어지지 않았다. 이 연구에서는 5만여명 유저들에 의해 기록된 약 6천만 건의 게임 내 로그 데이터 분석을 통해 유저들이 최고 레벨에 도달하는 과정과 그 이후 게임 이탈 현상을 분석하며, 최고 레벨 유저의 이탈에 영향을 미치는 요인을 이해하고자 한다. 분석 결과, 최고 레벨 이전의 행동 패턴을 이용해 최고 레벨 유저의 이탈을 예측할 수 있으며, 최고 레벨 이전에 사회적으로 활발하고 많은 사람들과 대화하는 게이머가 덜 떠난다는 것을 발견하였다(p<0.05). 이 연구는 유저간 소통 패턴이 최고 레벨에 도달한 유저들의 지속적인 사용에 주요한 요인임을 확인하며, 엘리트 유저의 지속적인 게임 이용을 유도하는 실무적 시사점을 제공한다.

• Animal Bioscience
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• 제37권6호
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• pp.1130-1139
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• 2024

Objective: The daily maximum temperature and seawater level continuously increase as global warming continues. We examined the adaptability and production performance of heat-stressed goats with a supply of low-saline drinking water. Methods: Twelve Kacang and Kacang Etawah cross goats were exposed to two climatic conditions (control, 25℃ to 33℃, 83% relative humidity [RH], temperature humidity index [THI]: 76 to 86; and hot environment, 26℃ to 39℃, 81% RH, THI: 77 to 94) and two salt levels in drinking water (0% and 0.4% NaCl). The experimental design was a Latin Square (4×4) with four treatments and four periods (28 days each). Results: Temperature of the rectal, skin, and udder, and respiration rate rose, reached a maximum level on the first day of heat exposures, and then recovered. Plasma sodium rose at 0.4% NaCl level, while the hot environment and salinity treatments increased the drinking water to dry matter (DM) intake ratio. Water excretion was elevated in the hot environment but lowered by the increase in salinity. Total lying time increased, whereas change position frequency decreased in the hot condition. Lying and ruminating and total ruminating time increased and explained the enhanced DM digestibility in the hot conditions. Conclusion: The goats exhibited a high level of plasma sodium as salinity increased, and they demonstrated physiological and behavioral alterations while maintaining their production performances under increasing daily maximum temperatures.

• 자원ㆍ환경경제연구
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• 제9권2호
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• pp.285-309
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• 2000

One of the main issues in natural resource economics is estimating the amount of stock and the biological growth functions of renewable natural resources. Since the stock level is not directly observed the usual econometric approaches cannot be employed for this purpose. The maximum entropy approach has been suggested as a useful alternative to estimate the dynamic model of natural resource use. This study estimates the stock and the growth function of Korean anchovy using the data for yield and yield efforts. The results show that the current level of anchovy yield exceeds its maximum sustainable yield, which implies that the stock will decrease substantially over time.

• 한국철도학회논문집
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• 제6권4호
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• pp.246-251
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• 2003

A quantitative analysis on the amounts of cant and lateral displacement of gravitational center due to the introduction of high-speed tilting car was carried out, based on the current alignment of the conventional line. In addition, the maximum allowable speed in curve and the level of improvement in maximum speed of tilting car were evaluated through the comparison with the maximum speed of locomotive. It was found that the tilting car produces an equivalent amount of cant, which corresponds to 47.5 % of current actual cant. This effect could be explained by the fact that 1.34 m, which is the height of gravitational center of tilting car from the rail level, is much lower than that of locomotive and thus guarantees much higher level of safety in curve. The equivalent amount of cant due to the lateral displacement of gravitational center followed by tilting in curve was 2.4 mm. It was small but not enough to be neglected and must be included in calculating the maximum speed in curve. It could be concluded that the 15 % speed-up of the conventional line is reasonable under the current condition of alignment.

• Steel and Composite Structures
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• 제17권2호
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• pp.145-157
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• 2014

This study aimed to investigate the fatigue crack growth behavior of a kind of fiber metal laminates (FML) under four different stress levels. The FML specimen consists of three 2024-T3 aluminum alloy sheets and two layers of glass/epoxy composite lamina. Tensile-tensile cyclic fatigue tests were conducted on centrally notched specimen at four stress levels with various maximum values. A digital camera system was used to take photos of the propagating cracks on both sides of the specimens. Image processing software was adopted to accurately measure the length of the cracks on each photo. The test results show that: (1) a-N and da/dN-a curves of FML specimens can be divided into transient crack growth segment, steady state crack growth segment and accelerated crack growth segment; (2) compared to 2024-T3 aluminum alloy, the fatigue properties of FML are much better; (3) da/dN-${\Delta}K$ curves of FML specimens can be divided into fatigue crack growth rate decrease segment and fatigue crack growth rate increase segment; (3) the maximum stress level has a large influence on a-N, da/dN-a and da/dN-${\Delta}K$ curves of FML specimens; (4) the fatigue crack growth rate da/dN presents a nonlinear accelerated increasing trend to the maximum stress level; (5) the maximum stress level has an almost linear relationship with the stress intensity factor ${\Delta}K$.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1425-1437
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• 2018

In this paper, a methodology was proposed to reduce the electrical level and spatial size of the smart grid with distributed generations (DGs) to a scale in which the electrical phenomena and control strategies for disturbances on the smart grid could be safely and freely experimented and observed. Based on the design methodology, a micro smart grid simulator with a substation transformer capacity of 190VA, voltage level of 19V, maximum breaking current of 20A and size of $2{\times}2m^2$ was designed by reducing the substation transformer capacity of 45MVA, voltage level of 23kV and area of $2{\times}2km^2$ of the smart grid to over one thousandth, and also reducing the maximum breaking current of 12kA of the smart grid to 1/600. It was verified that the proposed design methodology and designed micro smart grid simulator were very effective by identifying how all of the fault currents are limited to within the maximum breaking current of 20A, and by confirming that the maximum error between the fault currents obtained from the fault analysis method and the simulation method is within 1.8% through the EMTP-RV simulation results to the micro smart grid simulator model.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.91-99
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• 2010

HVDC converter station consists of a number of equipment such as converter transformer, ac filter, thyristor valve and so on. They can be acoustic noise sources. In this paper, we analyzed the simulation results of the outdoor acoustic noise for HVDC converter station. It shows that maximum noise level in boundary of HVDC converter station exceeds regulation value. The main factors in generating maximum noise level are ac filter and converter transformer. Then we applied some soundproof countermeasures in HVDC converter station. Shielding wall is enough to reduce transformer noise level but not enough to reduce ac filter noise level. In case of ac filter, soundproof building is effective in satisfying noise level regulation in boundary of HVDC converter station. In addition, we also studied effects of season, soundproof woods, ground.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.574-576
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• 2010

HVDC converter station consists of a number of noise sources such as converter transformer, ac filter, cooling system and so on. In this paper, we analyzed the simulation results of the outdoor acoustic noise characteristics for HVDC converter station. It shows that maximum noise level in boundary of HVDC converter station exceeds regulation value. The main factors in generating maximum noise level are ac filter and converter transformer. Then we applied some soundproof countermeasure in HVDC converter station. Shielding wall is enough to reduce transformer noise level but not enough to reduce ac filter noise level. In case of ac filter, soundproof building is effective in satisfying noise level regulation in boundary of HVDC converter station. In addition, we also studied effects of season, soundproof woods, ground.

• 농업과학연구
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• 제3권2호
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• pp.214-224
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• 1976

양생온도(養生溫度)가 혼화재(混和材)를 사용(使用)한 모르터의 강도(强度)에 미치는 영향(影響)을 조사(調査)키 위해서 양생온도(養生溫度)를 $20^{\circ}C$, $30^{\circ}C$, $35^{\circ}C$로 하여 모르터의 압축(壓縮), 인장(引張), 곡강도시험(曲强度試驗)을 실시(實施)하였고 그 결과(結果)를 요약(要約)하면 다음과 같다. 양생온도(養生溫度) $1^{\circ}C$ 상승(上昇)에 대(對)한 강도증가(强度增加)는 기준강도(基準强度)에 대(對)하여 연탄재첨가시(添加時) 압축강도(壓縮强度)에서 1.58%, 인장강도(引張强度)에서 0.96%, 곡강도(曲强度)에서 1.26% 증가(增加)했다. 동일(同一)한 경우 플라이애쉬 첨가시(添加時) 압축강도(壓縮强度)에서 1.3%, 인장강도(引張强度)에서 0.99%, 곡강도(曲强度)에서 1.18%의 증가(增加)를 나타냈다. 압축강도(壓縮强度)는 플라이애쉬 첨가량(添加量) 25%에서 인장강도(引張强度)는 20%, 곡강도(曲强度)도 20%에서 최대치(最大値)를 나타냈다. 연탄재를 혼합(混合)한 경우 압축강도(壓縮强度)에서 20% 인장강도(引張强度)에서 15~20%, 곡강도(曲强度)에서 20% 첨가(添加)할 때 최대치(最大値)를 나타냈다. 연탄재 첨가(添加)의 경우가 플라이애쉬 첨가(添加)의 경우 보다 저강도(低强度)이나 양생온도(養生溫度)의 조절(調節)로 소요(所要)의 강도(强度)를 얻을수 있기 때문에 혼화재(混和材)로서 개발(開發)할 여지(餘地)가 충분(充分)히 있는 것으로 사료(思料)된다.

• Journal of Nutrition and Health
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• 제29권3호
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• pp.267-277
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• 1996

Effect of DHA-rich fish oil on brain development and learning ability has been studied in Sprague Dawley rats. Female rats were fed experimental diets containing either corn oil fish oil at 10%(w/w) level throughout the gestation and lactation. Corn oil was added in fish oil diet to supply essential fatty acid at 2.3% of the calories. All male pups were weaned to the same diets of dams at 21-days after birth. Plasma fatty acid composition was analyzed for dams and pups at 21-days, 28-days and 22-weeks after birth. The analysis of DNA and fatty acid profile in the brain were undertaken at birth, 3, 7, 14, 21, 28 days and 22 weeks after birth and learning ability was tested at 18-20 weeks of age. Regardless of dietary fats, arachidonic acid(AA) and docosahexaenoic acid(DHA) were the principal polyunsaturated fatty acids in the brain. Rats fed CO diet showed a continouus increase of AA content in the brain from 10.9%(at birth) to maximum 15.3% level (14-days old), while the rars fed FO diet showed 78-79% of CO group throughout the period. Rats fed FO diet showed higher incorparation of DHA from 15.2% at birth to a maximum level of 18.5% at 140days, while the rats fed CO diet showed only 7.0% incorporation of DHA at birth and a maximum level of 11.1% at 21-days. Compared to CO group, FO group showed lower ratio of chol/PL and higher content of DHA in brain microsomal membrane, resulting in better membrane fluidity. Total amount of DNA per gram of brain was reached maximum level at 21 days in both groups. This would be a period of the cell proliferation during brain development. Overall, the rats fed fish oil diet showed a higher incorporation of DHA and membrane fluidity in the brain and better learning performances (p<0.05).