• Proceedings of the Korea Society for Simulation Conference
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• 1994.10a
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• pp.11-11
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• 1994

트래픽의 흐름을 조절하고 ATM 네트워크 자원의 사용을 최적화하기위해서는 폭주로 인한 성능 저하를 막기 위한 적절한 제어가 필요하다. 기존의 사용자 감시 제어(UPC) 메커니즘이 네트워크의 상황과는 관계없이 매우 불안정한 예방적 기능만을 수행하였고, qvj로 인해 셀 지연을 가중시키는 한계점을 갖고 있었다. 본 논문은 OAM 셀을 이용하여 네트워크의 상태에 따라 능동적으로 반응하는 적응적 사용자 감시 제어 메커니즘을 제안하고ㅡ 버퍼로 인한 지연을 고려하여 서비스의 한층 더 높이고자 한다. 제시한 사용자 감시 제어방식은 OAM 셀이 주는 정보를 바탕으로 네트워크 내의 상황을 판단하여 사용자가 요구한 서비스의 질을 고려할 수 있도록 리키율과 버퍼의 문턱값을 조정하였다. 네트워크가 분주시에는 리키율을 낮추고 버퍼를 줄여서 네트워크 내에 유입되는 셀을 막는 역할을 하고 네트워크가 한가할 때는 리키율을 높히고 버퍼를 늘여서 빠르게 네트워크 내로 셀이 유일도리 수 있\ulcorner 한다. 폭주 발생 시에는 셀의 유입을 막고 푹주 상태가 해결될때까지 스페이서의 작동을 멈춘다. 본 논문에서 제시한 사용자 감시 제어 메커니즘의 트래픽 소스 모델은 IPP로 모델링하였고, 트래픽은 음성과 고속 데이터를 중심으로 시뮬레이션하였다. 음성과 고속 대이타 각각의 경우에 시뮬레이션한 결과를 기존의 방식과 비교, 분석한 결과에서 음성에서는 버퍼지연이 대폭 줄였고 고속 데이터인 경우에는 셀 손실율이 줄어드는 것을 볼 수 있었다. 따라서 제시한 방식에 의해 사용자가 요구하는 서비스의 질을 유지하면서 동시에 네트워크의 자원을 효율적으로 사용하였음을 알 수있었다.에 적합한가를 고찰하였다.베이터에 의한 아파트의 소음 및 진동에 관하여 그 현황, 원인 그리고 대책에 관한여 논하고자 한다.감 방법을 연구하였고, T.Sakai는 5자유도 모델을 이용하여 엔진 공회전시 발생하는 치타음에 대해 이론과 실험을 통해 해석하고, 엔진 회전수 변동, 클러치 특성, 변속기의 드래그(drag) 토크의 영향과 치타음 저감을 위한 개선된 클러치 특성을 제시하였다. 이 외에도 Thomas C.T.와 E.P.Petkus는 특정 차량에 대한 동력전달계의 비틀림 진동 현상에 대해 연구하였다. 이러한 연구들로 볼 때, 자동차 동력전달계에서 발생하는 진동은 이론과 실험을 통해 그 해석이 가능하며 설계에 매우 유용하게 이용되고 있음을 알 수 있다. 따라서, 본 연구는 4 실린더 4 싸이클 1.5 L 엔진을 장착한 경승용차의 실차 주행실험을 통해 가속 페달의 급조작에 따른 차체의 종진동 현상을 측정하고, 엔진-변속기-타이어-차체의 반환정계 4자유도 진동모델로 시뮬레이션을 수행하여 실차 주행실험의 결과치와 비교, 분석한 후 클러치 비틀림 특성을 비롯한 자동차 동력전달계의 각 설계인자들이 차체의 종진동에 어떠한 영향을 미치는가를 해석하고자 한다.be presented.LIFO, 우선 순위 방식등을 선택할 수 있도록 확장하였다. SIMPLE는 자료구조 및 프로그램이 공개되어 있으므로 프로그래머가 원하는 기능을 쉽게 추가할 수 있는 장점도 있다. 아울러 SMPLE에서 새로이 추가된 자료구조와 함수 및 설비제어 방식등을 활용하여 실제 중형급 시스템에 대한 시뮬레이션 구현과 시스템 분석의 예를 보인다._3$", chain segment,

• Korean Journal of Poultry Science
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• v.25 no.4
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• pp.185-193
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• 1998

This experiment was conducted to investigate the effect of dietary supplemental Astragalus membranaceus on performance and meat quality of broiler chicks for 5 weeks. Basal diets based on corn and soybean meal contained 21％ crude protein for the first three weeks and 19％ for the rest of two weeks. Four levels of dietary Astragalus membranaceus(0, 0.25, 0.50, 1.00％) were fed in a one way design. There were four replicates of 50 chicks per treatment. Weight gain, feed intake, feed efficiency, blood component, breast meat lipid and protein were measured at the end of experiment. No increased growth rate was observed in chicks fed the basal diet supplemented with Astragalus membranaceus. Chicks fed the diet containing 0.5 and 1.00％ Astragalus membranaceus tended to depress the growth rate. Feed intake of 0.25％ Astragalus membranaceus treatment was significantly lower than control group(P<0.05), Dietary supplemental Astragalus membranaceus improved the feed efficiency compared to the control group, but was not significantly different between them. However, Astragalus membranaceus treatment exhibited decreased serum cholesterol and AST compared to those of control group, but was not significantly different between supplemental groups. Serum hematocrit, triglyceride, phosphate and BUN decreased at 0.25％ Asparagus membranaceous supplementation. Growth hormone and IGF-1 (ng/ml) of chicks fed more than 0.50％ Astragalus membranaceus significantly decreased compared to those of control(P<0.05). The total lipid and protein content of chicks fed 0.25 and 0.50％ Astragalus membranaceus tended to increase, but did not show consistency at more than 0.50％ supplement. The results of this experiment indicated that optimum dietary Astragalus membranaceus level to improve the performance and meat quality of broiler chicks may be less than 0.25％.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.718-723
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• 2016

The use of the scroll compressor in the air conditioning of medium-sized vehicles has increased because of its low torque fluctuation, high energy efficiency and low noise. In addition, the main components of the compressor have been changed from steel to aluminum to reduce its weight, following studies on the constituent materials. The processing precision of the fixed scroll and orbiting involute scroll wrap of the scroll compressor must be below $10{\mu}m$. To ensure this, the surface roughness and contour tolerance are measured. To improve the hardness of the orbiting scrolls using aluminum subjected to anodizing treatment and as the base material, we used a sealing treatment and measured the resulting characteristics. The aluminum materials were made of an Al-Mg-Cu based alloy including small amounts of Ni, Fe, and Zn. The surface roughness was less than $3{\mu}m$ and the processing accuracy was within $10{\mu}m$. Also, the hardness of the nanodiamonds with CNTs used in the sealing treatment was more than 450. This was found to improve the hardness of the material by 50% or more compared to the water sealing treatment and there was little difference between the use of carbon nanotubes and nanodiamonds as sealing materials.

• Elastomers and Composites
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• v.38 no.3
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• pp.227-234
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• 2003

Silicone composites for high voltage insulator (HVI SC) were prepared by adding aluminum trihydrate(ATH) treated by surface treatment agent to base silicone compound at the ratio oi 100:20, 100:40, 100:60, 100:80, and 100:100, respectively And also, ATH was treated by various surface treatment agents, such as stearic arid, acryl silane, and vinyl silane under compounding process. Mechanical properties and electrical properties were investigated for the various contents of ATH and surface-treatment agents. Mechanical properties such as tensile strength, elongation, and tear strength decreased as the load of ATH increased. Volume resistivity, AC break down strength, and tracking resistance for HVI SC containing ATH treated by vinyl silane were better than those for HVI SC containing ATH treated by other surface treatment agents, such as stearic acid and acryl silane. Polymer-filler interaction of silicone composites according to surface treatment agents was studied by measuring bound rubber contend(BR). From the experimental results, BR of silicone composite containing ATH treated with vinyl silane was higher than that of the others. The degree of rule for silicone composite was investigated using Rheometer. Maximum torque of silicone composites contaning ATH treated with vinyl silane was higher than that of silicone composite contaning ATH treated with other surface agents.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.1
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• pp.59-69
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• 2021

Recently, large-scale offshore and coastal structures have been constructed owing to the increasing interest in eco-friendly energy development. To achieve this, precise simulations of waves are necessary to ensure the safe operations of marine structures. Several experiments are required in the field to understand the offshore wave; however, in terms of scale, it is difficult to control variables, and the cost is significant. In this study, numerical waves under various wave conditions are produced using a piston-type wavemaker, and the produced wave profiles are verified by comparing with the results from a numerical wave tank (NWT) modeled using the smoothed particle hydrodynamics (SPH) method and theoretical equations. To minimize the effect by the reflected wave, a mass-weighted damping zone is set at the right end of the NWT, and therefore, stable and uniform waves are simulated. The waves are generated using the linear and Stokes wave theories, and it is observed that the numerical wave profiles calculated by the Stokes wave theory yield high accuracy. When the relative depth is smaller than two, the results show good agreement irrespective of the wave steepness. However, when the relative depth and wave steepness are larger than 2 and 0.04, respectively, the errors are negligible if the measurement position is close to the excitation plate. However, the error is 10% or larger if the measurement position is away from the excitation location. Applicable target wave ranges are confirmed through various case studies.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.12
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• pp.1720-1725
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• 2011

Aspartic acid chelated iron (Asp-Fe) was synthesized by a new method using calcium carbonate, aspartic acid, and ferrous sulfate. This study was carried out to investigate the bioavailability of Asp-Fe in iron-deficient rats. We divided the rats into four experimental groups. The first was the normal diet control group, or NC. The second was the no treated control group of iron-deficient (ID) rats, or ID+C. The third was the heme-iron (heme-Fe) treated group of ID rats, ID+heme-Fe. And the fourth was the Asp-Fe treated group of ID rats, or ID+Asp-Fe. There were no differences among any of the experimental groups in diet consumption, change of body weight, or the weight of the livers, kidneys, or spleens. After 7 days of feeding, the iron content in the sera of the ID+Asp-Fe group (175.2 ${\mu}g$/dL) and the ID+heme-Fe group (140.8 ${\mu}g$/dL) were significantly higher than that of the ID-C group (96.1 ${\mu}g$/dL). The total iron binding capacity (TIBC) of the ID+Asp-Fe group (735.4 ${\mu}g$/dL) was significantly normalized compared to the ID+C group (841.9 ${\mu}g$/dL) or ID+heme-Fe group (824.6 ${\mu}g$/dL). The hematocrit level of the ID+Asp-Fe group was increased to normal levels, but there was no statistical difference among ID groups. The absorption ratio of heme-Fe was 21.3% and that of Asp-Fe was 50.2%, which indicates a 2.3 times higher ratio in comparison with heme iron. With the above results we found that Asp-Fe seems to be an efficient form of iron to supply iron deficient rats in order to cure them of anemia. Thus, these findings suggest that aspartic acid chelated iron has the potential to serve as a functional food related to iron metabolism.

• Korean Journal of Food Science and Technology
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• v.10 no.2
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• pp.112-118
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• 1978

Four domestic frying oils (soybean, corn, rapeseed and rice bran oil) were studied on their changing properties according to thermal oxidation by means of chemical analysis of their compositions and measurements of various physical and chemical properties. The content of linoleic acid which is an essential unsaturated fatty acid and the total amount of unsaturated fatty acids were highest in soybean oil (53.2% and 80.3% respectively) among the unheated frying oils and the degree of its thermal degradation was lowest during the continuous heating period for 48 hours at $180^{\circ}C$. However in general, the contents of unsaturated fatty acids were sharply decreased by thermal oxidation whereas the saturated fatty acid contents ranging 10-17% were not changed considerably, which largely agreed with the results of iodine value measurements. The free acid and peroxide values were also lowest in soybean oil (0.09 and 5.6 respectively) among the unheated oils whereas an anomalously high free acid value was observed in rapeseed oil (54.8) which was packed in unleveled glass bottles. Such a high value is probably ascribed to the photo-catalyzed oxidation during storage. The viscosity measurements have shown similar values before heating, but after thermal oxidation for 32 hours the rapeseed and rice bran oils became too thick to measure viscosity by capillary flow method with heavy darkening in color.

• Journal of the Korean Applied Science and Technology
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• v.35 no.1
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• pp.173-185
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• 2018

Effects of three different types of dispersions and flow improving additives composed with fatty acid esters, fatty acid metal salts and amide compound on the vulcanization and the mechanical properties properties of rubber compounds of EPDM and carbon black as fillers. were investigated using Mooney viscometer, moving die rheometer, hardness tester, and universal test machine. The aging characteristics of vulcanized EPDM compounds were also investigated. The Mooney viscosity measured at $125^{\circ}C$ showed a tendency to decrease in the order of amide type> metal salt type > ester type additive. Scorch time showed little or no difference with the addition of ester or metal salt type additives, but the amide type additive shortened a scorch time more than one minute. Rheological measurement data obtained at $160^{\circ}C$ showed that the vulcanization time was faster for metal salt type and amide type additive systems. Delta torque values of EPDM compound increased with metal salt type and amide type additives, but slightly decreased with ester type additive. The tensile strength of the EPDM compound was greatly improved when an ester type additive was added, but the amide type or metal salt type additive had no significant effect. The elongation was significantly improved for metal salt type additive, while the rest were not significantly affected. The tear strength of the EPDM compounds increased with the addition of all kinds of additives, and it increased remarkably in the case of metal salt type additive. Hardness of the EPDM compounds was nearly same value regardless of additive types. The thermal aging of the EPDM blend at $100^{\circ}C$ for 24 h showed little change in the case of metal salt type or amide type additive, but the elongation tends to decrease by 10-20% for all EPDM compounds containing additives.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.530-534
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• 2006

조류발전은 조류 유속이 빠른 곳에 수차발전기를 설치하여 해수의 운동에너지로부터 전기를 생산하는 발전방식이다. 2001년부터 해양연구원에서는 울돌목의 우수한 조류발전 개발 여건을 바탕으로 조류에너지 실용화 기술을 개발하고 있다. 본 연구에서는 조류발전 시스템에 사용되는 헬리컬 수차의 효율을 현장실험을 바탕으로 판단하고자 하였다. 현장실험을 위하여 지름 2.2 m, 높이 2.5 m의 수차를 제작하고, 울돌목 협수로의 한 쪽 면에 쟈켓구조물을 설치하여 수차를 거치한다. 수차가 회전함에 따라 회전봉에 일정 마찰을 주어 토크와 RPM을 측정하고, 함께 측정된 유속자료를 이용하여 수차를 효율을 산정한다. 유속-수차효율, TSR(수차의 날개속도와 유속의 비)-수차효율의 상관관계로 실험결과를 고찰하였다. 1중 날개 수차인 경우에 유속 1.4에서 2.6 m/s 사이에서 최대효율이 30 - 35 % 정도였고, 2중 날개 수차에 대한 실험에서는 유속 1.4에서 2.6 m/s 사이에서 최대수차효율이 25 - 35 % 사이임을 알 수 있었다. TSR과 최대수차효율의 상관관계는 실험 case별로 조금씩 다르다. 전체적으로 1중 날개의 경우가 최대수차효율에서 2중 날개보다 TSR 값이 조금 큰 경향을 나타냄을 알 수 있다. 이것은 1중 날개가 2중 날개보다 가벼워 좀 더 큰 RPM을 발생시켜서 나타난 현상으로 생각된다. 현재의 실험결과들을 이용하여 TSR과 최대수차효율을 상관관계를 나타내는 모델식을 도출하였다. 현장시험결과를 종합하면, 현장조류발전 시설이 최소 600 kW의 전력이 생산되기 위해서는 지름 3 m, 높이 3.6 m 인 수차 3개가 하나의 축에 설치되어야하는 것으로 계산되었다. 정격유속이 4.8 m/s이고 수차의 지름이 3m 라면, 최적 전력발생시의 RPM은 1중 날개의 경우 79이고 2중 날개의 경우는 63정도임을 추정할 수 있었다.촬영하여 실시간으로 전송하기 때문에 홍수시 하천 상황에 대한 모니터링 목적으로 사용될 수 있다. 영상수위계는 우물통 등을 이용하는 기존 방법과 비교하여 구조물이 필요 없어 설치 비용이 저렴하고, 영상에 의한 하천 모니터링 기능을 자체적으로 가지고 있기 때문에 효율적이라고 할 수 있다.따른 4개의 평가기준과 26개의 평가속성으로 이루어진 2단계 기술가치평가 모형을 구축하였으며 2개의 개별기술에 대한 시범적용을 실행하였다.하는 것으로 추정되었다.면으로의 월류량을 산정하고 유입된 지표유량에 대해서 배수시스템에서의 흐름해석을 수행하였다. 그리고, 침수해석을 위해서는 2차원 침수해석을 위한 DEM기반 침수해석모형을 개발하였고, 건물의 영향을 고려할 수 있도록 구성하였다. 본 연구결과 지표류 유출 해석의 물리적 특성을 잘 반영하며, 도시지역의 복잡한 배수시스템 해석모형과 지표범람 모형을 통합한 모형 개발로 인해 더욱 정교한 도시지역에서의 홍수 범람 해석을 실시할 수 있을 것으로 판단된다. 본 모형의 개발로 침수상황의 시간별 진행과정을 분석함으로써 도시홍수에 대한 침수위험 지점 파악 및 주민대피지도 구축 등에 활용될 수 있을 것으로 판단된다. 있을 것으로 판단되었다.4일간의 기상변화가 자발성 기흉 발생에 영향을 미친다고 추론할 수 있었다. 향후 본 연구에서 추론된 기상변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전거래전략을 활용하는 경우 주식투자기간은 24개월이하의 중단기가 적합함을 발견하였다. 이상의 행태적 측면과 투자성과측면의 실증결과를 통하여 한국주식시장에 있어서 시장수익률을 평균적으로 초과할 수 있는 거래전략은 존재하므로 이러한 전략을 개발 및 활용할 수 있으며, 특히, 한국주식시장에 적합한 거래전략은 반전거래전

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.6
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• pp.674-682
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• 2009

This study was designed to examine the effects of Compositae plants on plasma glucose and lipid levels in streptozotocin (STZ) induced diabetic rats. Sprague-Dawley rats were randomly assigned to 5 groups: normal, STZ-control and three experimental groups [Artemisia iwayomogi (A. iwayomogi), Atractylodes lancea (A. lancea), and Taraxacum mongolicum (T. mongolicum)]. Normal and STZ-control group were fed an AIN-93 diet and three experimental groups were each fed a modified diet containing 10% compositae powder for 4 weeks. The plasma glucose levels at 4 weeks of A. iwayomogi, A. lancea, and T. mongolicum groups were significantly lower than STZ-control group. The A. iwayomogi and A. lancea groups had significantly suppressed hypertrophy of liver and kidney. The hematocrit levels of A. lancea and T. mongolicum group were significantly lower than STZ-control groups. The total cholesterol and triglyceride levels and atherogenic index (AI) of A. lancea group were significantly lower than STZ-control group. Intake of Compositae plants may be effective in antihyperglycemia by lowering blood glucose levels. The A. iwayomogi, A. lancea, and T. mongolicum can be beneficial for the diabetic complications and damage from the lipid peroxidation.