• 설비공학논문집
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• 제26권3호
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• pp.108-114
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• 2014

On a large scale of data center, heat generation rates from sever computers occupy almost the entire cooling load of the building, and it is gradually increasing. The efficiency of air distribution system in data centers can be affected by heat generation rates of server computers. In this study, the distributions of airflow and temperature in a data center have been investigated by CFD simulations under various conditions of heat generation rates for server computers. From the results, air around the cold aisle which has high temperature flows tremendously into the cold aisle according to the increase of heat generation rates for server computers and the air temperature in the cold aisle becomes higher. The SHI (supply heat index) and RHI (return temperature index) show almost similar values to the cases study because the air inflow rates to server computers increase with the heat generation rates of server computers.

• 대한전기학회논문지:전력기술부문A
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• 제54권8호
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• pp.418-428
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• 2005

In this paper, a new probabilistic generation modeling method which can address the characteristics of changed electricity industry is proposed. The major contribution of this paper can be captured in the development of a probabilistic generation modeling considering generator maintenance outage and in the classification of market demand into multiple demand clusters for the applications to electricity markets. Conventional forced outage rates of generators are conceptually combined with maintenance outage of generators and, consequently, effective outage rates of generators are newly defined in order to properly address the probabilistic characteristic of generation in electricity markets. Then, original market demands are classified into several distinct demand clusters, which are defined by the effective outage rates of generators and by the inherent characteristic of the original demand. We have found that generators have different effective outage rates values at each classified demand cluster, depending on the market situation. From this, therefore, it can be seen that electricity markets can also be classified into several groups which show similar patterns and that the fundamental characteristics of power systems can be more efficiently analyzed in electricity markets perspectives, for this classification can be widely applicable to other technical problems in power systems such as generation scheduling, power flow analysis, price forecasts, and so on.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.804-806
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• 2005

In this paper, a new probabilistic generation modeling method which can address the characteristics of changed electricity industry is proposed. The major contribution of this paper can be captured in the development of a probabilistic generation modeling considering generator maintenance outage and in the classification of market demand into multiple demand clusters for the applications to electricity markets. Conventional forced outage rates of generators are conceptually combined with maintenance outage of generators and, consequently, effective outage rates of generators are new iy defined in order to properly address the probabilistic characteristic of generation in electricity markets. Then, original market demands are classified into several distinct demand clusters, which are defined by the effective outage rates of generators and by the inherent characteristic of the original demand. We have found that generators have different effective outage rates values at each classified demand cluster, depending on the market situation. From this, therefore, it can be seen that electricity markets can also be classified into several groups which show similar patterns and that the fundamental characteristics of power systems can be more efficiently analyzed in electricity markets perspectives, for this classification can be widely applicable to other technical problems in power systems such as generation scheduling, power flow analysis, price forecasts, and so on.

• 한국환경보건학회지
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• 제28권2호
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• pp.117-129
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• 2002

Concentration of welding fumes and their components is known to be hazardous to welder and adjacent worker. To determine the generation rates of metals in fumes, $CO_2$ flux cored arc welding on stainless steel was performed in well designed fume collection chamber. Variables were different products of flux cored wire(2 domestic products and 4 foreign products) and input energy(low-, optimal- , high input energy). Mass of welding fumes was determined by gravimetric method(NIOSH 0500 method), and 17 metals were analysed by inductively coupled plasm-atomic emission spectroscopy(NIOSH 7300 method). Flux cored wire tube and flux were analysed by scanning electron microscopy to determine their metal composition. 17 metals were classified by their generation rates. Generation rates of iron, manganese, potassium and sodium were all above 50mg/min at optimal input energy level. Generation rates of chromium and amorphous silica were 25~50mg/min. At 1~25mg/min level, nickel, titanium, molybdenum, and aluminum were included. Copper, zinc, calcium, lead, magnesium, lithium, and cobalt were generated below 1 mg/min. Generation rates of metal components in fumes were influenced by input energy, types of flux cored wire. Flux cored wire was consisted of outer shell tube and inner flux. Iron, chromium, and nickel were the major components of outer tube. Flux contained iron, chromium, nickel, potassium, sodium, silica, and manganese. The use of flux cored wire can increase the hazards by increasing the amounts of fumes formed relative to that of solid wire. The reason might be the direct transfer of elements from the flux, since the flux is fine power. Ratio of metals to the fume of flux cored wire was lower than that of solid wire because non-metal components of flux were transferred. Total metal content of fumes in flux cored arc welding was 47.4(24.3~57.2) percent that is much lower than that of solid wire, 75.9 percent. We found that generation rates of iron, manganese, chromium and nickel, all well known to cause work related disease to welder, increased more rapidly with increasing input energy than those of fumes. To reduce worker exposure to fumes and hazardous component at source, further research is needed to develop new welding filler materials that decrease both the amount of fumes and hazardous components.

• 자원ㆍ환경경제연구
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• 제28권1호
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• pp.147-176
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• 2019

본 연구에서는 국내의 균등화 발전비용에 대한 연구결과를 기초로 하여 전원 구성에 있어서 원자력의 비중이나 이용률이 발전의 사회적 비용에 어느 정도 영향을 주는지를 시뮬레이션을 통해 도출한다. 원전이 상대적으로 증가되도록 설계되었던 제7차 전력수급기본계획과 원전의 비중을 축소하고 신재생에너지 발전의 비중을 증가시킨 제8차 전력수급기본계획을 비교하여 전원 믹스에 따른 발전의 사회적 비용, 발전단가, 전기요금의 변화 정도를 추정한다. 8차 수급계획의 환경급전 관련 변수를 고려하고, 국내 두 기관의 균등화 발전비용 연구결과를 이용한 시뮬레이션 결과, 사회적 비용은 향후 10년 내에 22%까지 증가할 수 있고, 직접적인 전력생산비용에 기초하고 있는 발전단가 역시 22% 증가하고, 전기요금은 최대 18%까지 증가할 수 있음을 도출하였다. 따라서 제8차 전력수급기본계획에 따른 전원믹스는 발전에 따른 외부 비용까지 고려한 사회적 비용차원에서 검토할 경우 7차 수급계획의 전원믹스와 비교할 때 사회적 비용을 증가시킨다.

• International journal of advanced smart convergence
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• 제12권3호
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• pp.19-24
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• 2023

Recently, fifth generation (5G) networks are being deployed in phases all over the world, the paradigm has shifted to developing the next generation wireless technologies, which have grown exponentially in last few decades, wireless networks are promising for the demand to enormous connections. Non-orthogonal multiple access (NOMA) and intelligent reflecting surface (IRS) are considered as the key technoloies for next-generation beyond 5G (B5G) and sixth generation (6G) networks, in which IRS can play an important advance in the wireless propagation environment, and NOMA can effectively increase massive connectivity to improve user fairness. In this paper, we analyze a performance on the strongest channel user in terms of achievable data rates numerically. Then, with the achievable data rates, the signal-to-noise ratio (SNR) gain is calculated for the IRS-NOMA network over the conventional NOMA network. As a consequence, IRS-NOMA schemes have been considered as some key technologies.

• 문화기술의 융합
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• 제10권4호
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• pp.105-109
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• 2024

본 연구는 저출산과 사회 변화로 인해 점점 더 심각해지고 있는 군간부 인력 충원 문제를 분석하고, MZ세대의 특성을 고려한 인력 충원 전략을 모색하고자 한다. 군은 북한의 지속적인 군사적 위협 속에서 안보를 지키기 위해 노력하고 있으나, 저출산으로 인해 병역 자원이 급감하고 있어 인력 충원에 직접적인 영향을 미치고 있다. 또한, MZ세대의 가치관 변화와 군 조직 문화의 괴리로 인해 우수 인재 유치에도 어려움을 겪고 있다. MZ세대는 일과 삶의 균형, 수평적 관계, 자아실현 등을 중시하며, 권위적이고 수직적인 군 조직 문화는 이들에게 매력적으로 다가오지 않는다. 이에 본 연구는 군의 인력 충원 문제점을 진단하고, MZ세대의 특성을 반영한 맞춤형 인력 충원 전략을 제시하여, 미래 군의 지속가능한 발전 방향을 모색하는 것을 목적으로 한다.

• 한국환경과학회지
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• 제17권10호
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• pp.1069-1073
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• 2008

Indoor air quality can be affected by indoor sources, ventilation, decay and outdoor levels. Although technologies exist to measure these factors, direct measurements are often difficult. The purpose of this study was to develop an alternative method to characterize indoor environmental factors by multiple indoor and outdoor measurements. Using a mass balance model and regression analysis, penetration factor (ventilation rate divided by the sum of ventilation rate and deposition constant) and source strength factor (source strength divided by the sum of ventilation rate and deposition constant) were calculated using multiple indoor and outdoor measurements. Subsequently, the ventilation rate and $NO_2$ generation rate were estimated. Mean of ventilation rate was 1.41 ACH in houses, assuming a residential N02 deposition constant of 0.94 $hr^{-1}$. Mean generation rate of $NO_2$ was 16.5 ppbv/hr. According to house characterization, inside smoking and family number were higher $NO_2$ generation rates, and apartment was higher than single-family house. In conclusion, indoor environmental factors were effectively characterized by this method using multiple indoor and outdoor measurements.

• 한국양식학회지
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• 제9권3호
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• pp.287-291
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• 1996

유도된 자성발생성 2배체를 친어로 양식어민에게 보급하고 유전적 동형접합제를 생산하기 위해 제 2세대 자성발생성 2배체를 유도하였다. 제 1세대 자성발생성 2배체의 성숙과 산란은 광주기와 HCG 처리로 유도하였을 때, 부상률은 $22.9\~65.7\%$의 범위로 나타났으며, 수정률은 $69.0\~86.2\%$, 그리고 부화율은 $36.8\~85.8\%$의 범위로 나타나 제 2세대 자성발생성 2배체군과 대조군 간에는 유의적 차이가 없었다(P>0.05). 제 2세대 자성발생성 2배체의 생존율은 부화 후 40일까지 부화 자어수의 약 $30\%$로 대조군에 비하여 $15\%$ 낮게 나타났다(P<0.05). 평균 전장 3 cm 이후에 선발육종을 실시한 결과 평균 전장 4 cm 이후에 대조군에 비하여 급격히 성장함이 관찰되어 부화 후 100일째에는 평균 전장이 대조군이 10.0 cm, 제 2세대 자성발생성 2배체는 15.4 cm로 나타나 통계적으로 유의하였다(P<0.01).

• Investigative Magnetic Resonance Imaging
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• 제5권1호
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• pp.24-32
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• 2001

Purpose : We investigated the reproducibility of language lateralization by 4 different word generation paradigms or the rest contents in each paradigm using functional magnetic resonance imaging in normal volunteers Materials and Methods Nine normal volunteers with left-handedness (mean age: 25 yrs) were examined on a 1.57 MR unit using a single-shot gradient echo epibold sequence. Four different word generation paradigms of noun, verb, adjective and adverb were used in each normal volunteer for investigating language system. In each paradigm, two different rest contents consisted of only seeing the " +" symbol or reading the meaningless letters. Each task consisted of 96 phases including 3 activations and 6 rests of 2 different contents. Two activation maps in one task were obtained under two different rest contents using the correlation method. We evaluated the detection rates of Broca and Wernicke areas and the differences of language lateralization among four different word generation paradigms, or between the rest contents. Results : The detection rates of Broca and Wernicke areas were over 67 % in 4 different language paradigms and there was no significant difference of them among language paradigms, or between two different rest contents. Language dominances, in all 4 different language paradigms, were shown to be consistent in 66 %, but were contrary with language paradigms in some subjects. The rest contents made no significant effect on dominant language dominance determination, but the success rates of the dominant language dominances determined from 4 language paradigms were higher in reading the meaningless letter (100%, n=9) than in only seeing "+" on screen at the rest task (78%, n=7).