• Nuclear Engineering and Technology
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• 제48권2호
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• pp.376-385
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• 2016

A hexagonally arrayed 37-pin wire-wrapped rod bundle has been chosen to provide the experimental data of the pressure loss and flow rate in subchannels for validating subchannel analysis codes for the sodium-cooled fast reactor core thermal/hydraulic design. The iso-kinetic sampling method has been adopted to measure the flow rate at subchannels, and newly designed sampling probes which preserve the flow area of subchannels have been devised. Experimental tests have been performed at 20-115% of the nominal flow rate and $60^{\circ}C$ (equivalent to Re ~ 37,100) at the inlet of the test rig. The pressure loss data in three measured subchannels were almost identical regardless of the subchannel locations. The flow rate at each type of subchannel was identified and the flow split factors were evaluated from the measured data. The predicted correlations and the computational fluid dynamics results agreed reasonably with the experimental data.

• 한국항공우주학회지
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• 제30권4호
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• pp.28-37
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• 2002

음향불안정을 억제하는 수동제어기구중 하나인 음향공의 음향학적 효과를 파악하기 위해, 음향공이 장착된 로켓엔진 연소실의 음향장 특성을 수치해석적으로 조사하였다. 음향공 모델로서 Helmholtz 형태의 공명기가 채택되었고, 조화해석을 통해 주로 음향공에 의해 야기되는 음향학적 효과를 관찰하였다. 음향공의 음속을 조정하여 동조주파수를 변화시켜가면서 가진음원에 대한 연소실의 음향진동 응답을 구하고, 제1접선방향 음향모드의 감쇠인자를 구하였다. 동조주파수가 제1접선방향 음향모드의 공진주파수에 접근함에 따라 모드분할 현상이 나타났고, 이로인해 음향공을 본래의 제1접선방향 음향모드에 동조시키더라도 음향감쇠효과가 저하됨을 알았다. 모드분할 현상과 분할된 각 모드의 감쇠인자 및 음향 에너지 분포를 고려하였으며, 이를 토대로 효과적인 감쇠를 위해서는, 억제하고자 하는 음향모드로부터 모드분할 현상이 나타나지 않으면서 그 음향모드의 감쇠효과를 극대화하도록 음향공을 동조시키는 것이 바람직함을 알 수 있었다.

• 인터넷정보학회논문지
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• 제19권1호
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• pp.11-17
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• 2018

본 논문에서는 회사 또는 백화점 등과 같은 고층 건물에 다수의 펨토셀 기지국들(Femtocell base stations, fBSs)이 밀집되어 배치되는 기업형 펨토셀 네트워크(Enterprise femtocell network, EFN) 환경에서 부분 주파수 재사용 (Fractional frequency reuse, FFR) 자원할당 방법을 이용하여 하향링크에 대한 시스템 성능을 분석한다. 이를 위해, 먼저 매크로셀과 펨토셀 사이의 주파수 간섭을 완화시키는 Split reuse 주파수 할당 방법에 대해 소개하고, 이후 EFN의 fBS들에게 주파수 간섭 완화 및 주파수 효율을 극대화할 수 있는 FFR을 이용한 자원할당 방법을 제안한다. 마지막으로 시뮬레이션을 통해 제안하는 FFR 자원할당 방법의 시스템 성능을 분석하고, EFN 환경에서 주파수 재사용 계수(Frequency reuse factor: FRF)를 4로 사용하는 전형적인 FRF 4 방법보다 제안하는 FFR 자원할당 방법이 평균 fUE 용량, 전체 EFN 용량, 그리고 Outage probability 측면에서 우수한 성능임을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권2호
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• pp.562-576
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• 2020

The power allocation optimization problem is investigated for improving the physical-layer security in two-way relaying networks, where a full-duplex relay based half-jamming protocol (HJP-FDR) is considered. Specially, by introducing a power splitter factor, HJP-FDR divides the relay's power into two parts: one for forwarding the sources' signals, the other for jamming. An optimization problem for power split factor is first developed, which is proved to be concave and closed-form solution is achieved. Moreover, we formulate a power allocation problem to determine the sources' power subject to the total power constraint. Applying the achieved closed-form solutions to the above-mentioned problems, a two-stage strategy is proposed to implement the overall power allocation. Simulation results highlight the effectiveness of our proposed algorithm and indicate the necessity of optimal power allocation.

• 복식문화연구
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• 제8권2호
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• pp.282-292
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• 2000

The purpose of this study is to provide for some basic data useful to the development of the brassieres comfortable and more suitable for obese women. The results of this study can be summarized as follows ; 1. Obese women were categorized using Rohrer index into three groups, and thereupon, their breast forms were analyzed. As a result, it was found that group 1 and 2 had similar small breasts, while group 3 had the largest size of breasts. 2. The forms of obese women's breast split, protrusion and volume, factors related with breast area and drooping, factor affecting the breast protrusion and factor defining the lower form of breast. 3. The actual breast types of obese women could be classified into cone type, protrusion type, drooping type Ⅰ and Ⅱ. The more obese a woman was, her breast tended more to droop.

• 아동학회지
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• 제22권3호
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• pp.1-15
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• 2001

The development of this inventory for measuring the parenting self-efficacy of Korean mothers took place in Seoul with 473 mothers of 5th and 6th grade children. Means, %, ${\chi}^2$, Cramer's V, Cronbach's ${\alpha}$, Split-half Reliability, factor analysis and Pearson's r were used for data analysis. Five parenting self-efficacy factors were extracted from the 37 items developed for this study. Subscales were General Parenting Self-Efficacy, Health, Communication, Education, and Control. Criterion Validity of the 37 items was confirmed by a significant correlation with the Shin's parenting self-efficacy(r=.71). Internal consistency of this scale was high (Cronbach's ${\alpha}=.92$), including internal reliability of subscales. Factor validity was satisfactory at .65 - .86. These results confirm this scale as a valid and reliable measure of the parenting self-efficacy of Korean mothers.

• 가정과삶의질연구
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• 제10권1호통권19호
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• pp.1-13
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• 1992

The purpose of this study was to validate the Elementary HOME(Home Observation for Measurement of the Environment) with korean elementary children. Subjects were 536 mothers 1st-5th graders in the elementary schools in the Seoul. Pearson's r, pearcentage(%), phi($\phi$/), Cronbach's $\alpha$/ ware conducted for the statistical analysis. The major findings were as follows. 1) The item pass rate(percentage) were ranged 16~98. 2) The discriminant coefficients($\phi$/) of the item were ranged 0.06~0.58. 3) The reliability coefficients of the scale were that the split-falf was 0.84, and Cronbach's $\alpha$/ was 0.88. Considering the length of the scale, these reliability estimates appear to be at an acceptable level 4) The factor analysis and the correlations between HOME and SES indices and children's school schievement to test construct validity were conducted to test construct validity. Eight factors were extracted from the factor analysis and coefficients(r) were ranged 0.16~0.45 and -0.08~0.37.

• Clinics in Shoulder and Elbow
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• 제22권3호
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• pp.159-170
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• 2019

Delaminated rotator cuff tear pertains to the horizontal split of the tendon substance. As reported previously, the presence of a delaminated tear and incidence of delaminated rotator cuff tear ranges from 38% to 92%. The different strain intensities applied across the rotator cuff tendon, and the shear stress between the bursal and articular layers seem to play a role in its pathogenesis. In a delaminated rotator cuff tear, the degree and direction of retraction between two layers differ, with accompanying intrasubstance cleavage. A surgeon therefore needs to consider and carefully evaluate the tear characteristics when repairing delaminated rotator cuff tear. Delaminated rotator cuff tear is considered to be a poor prognostic factor after rotator cuff repair, but numerous surgical repair techniques have been introduced and applied to resolve this problem. Recent literature has reported good clinical outcomes after delaminated rotator cuff repair.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.624-629
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• 2016

철도차량에서 기초제동장치의 제동레버는 제동통으로부터 발생되는 작용하중을 받아서 제동패드로 전달하는 중요한 안전장치로 설계 시 높은 안전성이 요구되는 기구이다. 그러나 철도차량의 설계기준인 【철도차량 안전기준에 관한 규칙】에 의하면 충분한 강도를 가져야 한다와 같이 정성적인 기준만을 제시하고 있어 실제 안전율 1.27로 설계된 전기기관차용 제동레버가 절손되어 재질을 바꿔 강도를 높인 적이 있고 또한 철도차량의 종류에 따라 각기 다른 구조의 제동레버를 사용하고 있어 본 논문에서는 분리형 구조로 설계된 고속철도차량과 일체형으로 설계된 전기동차와 전기기관차에 적용된 각각의 제동레버에 대해 이론적 해석, 구조해석을 시행하여 응력분포 및 취약부분을 확인하였다. 또한 제동 시 발생되는 수평응력과 굽힘 응력의 관계를 확인하기 위해 파단시험을 실시하여 제동레버가 굽힘 응력을 많이 받음을 확인하였다. 이와 같은 해석과 실험을 통해 실제 운행 중인 철도차량의 각 제동레버에 적용된 안전율을 확인하였으며, 실제 적용된 안전율을 바탕으로 최소 정량적인 안전율의 기준 값을 제시하였다. 그리고 일체형으로 제작된 전기동차의 제동레버에 대해 동일조건하에 분리형으로 설계 변경하여 구조해석을 시행하여 일체형으로 설계된 제동레버를 분리형으로 설계 변경하였을 경우 안전율 향상에 어느 정도 영향을 미치는지를 분석하였다.

• 대한방사선기술학회지:방사선기술과학
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• 제8권2호
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• pp.71-72
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• 1985

This study was performed on the dose distribution of various field size and the effect of penumbra shield in the telecobalt unit. The results obtained are as follows. 1. Errors of the light and ${\gamma}-ray$ field size was below the regulation as 0.52 percentage. 2. The coefficient of field area was increased with the larger field area, and this coefficient was showed the more difference in larger SSD. 3. The rectangular field areas, which were described by level of the same percentage depth does, were decreased with the more elongation factor. At the same elongation factor, the compensating factor was decreased with the larger field size. 4. The lead block or extension collimator was able to shield r-ray exposure of outside field size from 50 to 80 percentage. 5. On the matching adjacent fields, while the gap between beam edges are contacted, that overlapped beam edges indicated up to 140 percentage, and while the gap was 1 cm, it could be reduced to 90 Percentage. The lead-libocking on the overlapped area was more effective to lower dose, as 80 percentage in this case. 6. Percentage depth dose of various trimming field sizes were increased linearlly according to area 1 perimeter size, but the center split field size did not maintain linearlly.