• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.587-590
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• 2003

The first attention in designing a transformer for low temperature rise should be to reduce losses. Leakage inductance and temperature rise are two of the more impotent problems facing the magnetic core technology of today's high frequency transformers. Excessive leakage inductance increases the stress on the switching transistors and limits the duty-cycle, and excessive temperature rise can lead the design limitation of high frequency transformer with high current. The flat transformer technology provides a very good solution to the problems of leakage inductance and thermal management for high frequency power. The critical magnetic components and windings are optimized and packaged within a completely assembled module. The turns ratio in a flat transformer is determined as the product of the number of elements or modules times the number of primary turns. The leakage inductance increase proportionately to the number of elements, but since it is reduced as the square of the turns, the net reduction can be very significant. The flat transformer modules use cores which have no gap. This eliminates fringing fluxes and stray flux outside of the core. The secondary windings are formed of flat metal and are bonded to the inside surface of the core. The secondary winding thus surrounds the primary winding, so nearly all of the flux is captured.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전력기술부문
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• pp.95-99
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• 2001

Frequency is the unique physical value for all the interconnected systems. Therefore. the load frequency control is in the responsibility of all members in the interconnection power unbalance in one of the interconnected system can cause the problems in others. In the following text a brief description and the role of frequency in an interconnected system will be presented. Following is the short description of the Balkan Interconnection (UCTE Second Synchronous Zone) with schematic diagram. A Power-Frequency (P-f) dynamic model of a control area wil1 be shown. Model gives the analytical solution for frequency change versus a time after outage of a generator in the power system. This model will be applied to the Balkan Interconnection and compared with numerical approach. Advantages and drawbacks of the analytical method will be discussed Purpose of using this model is to investigate if the pumps in reversible hydropower plant will be underfrequency shed after the outage of the biggest generator unit in the interconnection, according %o (n-1) security postulate.

• 전기학회논문지
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• 제56권12호
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• pp.2072-2077
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• 2007

The primary objective of all power systems is to maintain the reliability and to minimize outage time for fault or the others. The frequency relaying algorithm perceives a variation of system frequency and thereafter detects the unbalance between generation and load. A multi-agent system is composed of multiple interacting computing elements that are known as agents. In this paper, frequency relaying algorithm is designed by multi-agent system and is implemented by EMTP-MODELS. To verify performance of the frequency relaying algorithm based on multi-agent system, simulations by EMTP have been carried out.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.176-178
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• 2005

In this paper deals with the frequency control of the HVDC scheme linking Haenam to Cheju Island. The primary aim of the study is to develop and evaluate a new frequency control that can be employed without having to utilize the existing Synchronous Compensators(Gas Turbines). Study cases are completed involving synchronous compensators trip and load tripping events and study plots presented. It is demonstrated that the existing frequency measurement can be replaced by one derived from the AC network alone, incorporated into a new frequency control algorithm and gives good frequency control and dynamic performance.

• 대한소아치과학회지
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• 제27권1호
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• pp.122-134
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• 2000

각화치은, 부착치은의 폭경, 치은열구의 깊이에 대해 성인에서는 많은 연구가 있었으나 아동에서의 연구는 드물었기 때문에, 유치열기, 혼합치열기 및 영구치열기의 모든 치아에 대하여 아동의 협측 각화치은 및 부착치은의 폭경과 치은열구 깊이에 대한 정상치를 구하고, 악골의 발육 및 치아의 맹출과의 관련성을 고찰하며, 점막치은 문제의 발현빈도를 조사하고자 하였다. 결론은 다음과 같다. 1. 유치열의 부착치은 폭경은 상악 유측절치 및 유견치에서 각각 3.50mm, 3.55mm로 최대값을, 하악 제1유구치에서 1.34mm로 최소값을 나타내었다. 영구치열의 경우에는 상악 측절치에서 3.00mm로 최대값을, 하악 제1소구치에서 0.55mm로 최소값을 나타내었다. 상하악 동명치아 비교시 상악 치아가 하악 치아보다 더 큰 값을 나타내었고, 남녀간 차이에는 특별한 규칙이 발견되지는 않았다. 2. 연령증가에 따른 부착치은 폭경의 변화 양상은 유치열의 경우 유견치, 제1유구치, 제2유구치에서 6세부터 증가하였다. 영구치의 경우 남자에서는 하악 중절치와 상악 제 1대구치의 측정값만이 연령에 따른 증가 추세를 나타냈으나(p<0.05), 여자에서는 상하악 중절치 측절치 및 상악 제1대구치에서 통계적으로 유의성 있는 각화치은 폭경의 증가 추세를 관찰할 수 있었다(p<0.05). 3. 치아교대기에서 부착치은 폭경의 차이는 남자 상악 중절치를 제외한 모든 경우에 유치에서의 측정값이 영구치에서의 측정값보다 큰 것으로 나타났다(p<0.05). 4. 6제부터 12세까지는 각화치은의 폭경과 치은열구의 깊이는 대부분 유치 초기값보다 그 계승영구치 최종값이 더 높은 값을 나타냈으나(p<0.05), 부착치은의 폭경에서는 유치 초기와 그 계승영구치 최종값사이에 통계적으로 유의성 있는 차이가 나타나지 않았다. 5. 점막치은 문제 발현 빈도는 남녀에 상관없이 유치열은 상하악 제 1유구치가, 영구치열은 상하악 모두 제 1소구치가 최고치를 나타냈으며 유치에서보다 그 대응 계승영구치에서 그 빈도가 더욱 높게 나타났다. 연령증가에 따라 점막치은 문제의 발현 빈도는 유치열, 영구치열에서 모두 감소하였으나, 하악 제1유구치, 하악 영구 견치, 제1, 제2소구치의 경우 연령의 증가와 상관없이 비슷하게 유지되거나 증가하는 경향을 보였다.

• 대한전자공학회논문지TC
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• 제48권9호
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• pp.27-34
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• 2011

무선 통신 시스템의 효율을 높이기 위해 제안된 무선인지 (Cognitive Radio) 시스템은 2차 사용자가 주사용자 (primary user)의 스펙트럼을 서로 공유하는 시스템이다. 2차 사용자가 주사용자에게 간섭을 일으키지 않으면서 효율적으로 데이터를 전송하기 위해서 NC-OFDM (Non-contiguous Orthogonal Frequency Division Multiplexing)을 사용한다. 하지만 NC-OFDM은 기존 OFDM과 마찬가지로 높은 PAPR (Peak-to-Average Power Ratio)을 발생시켜 시스템 성능을 저하시킨다. 본 논문에서는 첫 번째로 NC-OFDM에서 부반송파의 분포에 따른 PAPR에 대해 분석하였다. 두 번째로 기존 OFDM의 PAPR 감소기법인 PTS (Partial Transmit Sequence)와 SLM (Selective Mapping)을 NC-OFDM에 적용하여 PAPR 감소성능을 확인하였다. 마지막으로 pruned-FFT가 적용된 PAPR 감소기법을 NC-OFDM에 적용할 경우 계산복잡도를 기존 OFDM과 비교하였다. 시뮬레이션을 통해 pruned-FFT가 적용된 NC-OFDM이 기존 OFDM보다 PAPR 감소성능 및 계산복잡도 측면에서 보다 효율적임을 검증하였다.

• Journal of Positioning, Navigation, and Timing
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• 제10권3호
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• pp.197-206
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• 2021

We compared two typical ensemble time scale algorithms; AT1 and Kalman filter. Four commercial atomic clocks composed of two hydrogen masers and two cesium atomic clocks provided measurement data to the algorithms. The allocation of relative weights to the clocks is important to generate a stable ensemble time. A 30 day-average-weight model, which was obtained from the average Allan variance of each clock, was applied to the AT1 algorithm. For the reduced Kalman filter (Kred) algorithm, we gave the same weights to the two hydrogen masers. We also compared the frequency stabilities of the outcome from the algorithms when the frequency offsets and/or the frequency drift offsets estimated by the algorithms were corrected or not corrected by the KRISS-made primary frequency standard, KRISS-F1. We found that the Kred algorithm is more effective to generate a stable ensemble time scale in the long-term, and the algorithm also generates much enhanced short-term stability when the frequency offset is used for the calculation of the Allan deviation instead of the phase offset.

• Asian Pacific Journal of Cancer Prevention
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• 제15권24호
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• pp.10607-10611
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• 2015

Background: HER2 expression in the primary tumor and its lymph node metastases vary in gastric cancer, reflecting intratumoral heterogeneity. This finding also suggests that proliferation of a different clone in metastatic nodes is possible. In the current study, we aimed to determine the cause of discordance in HER-2 expression in the primary tumor and lymph node metastases for patients with gastric cancer. Materials and Methods: Eighty-one patients with gastric cancer who had undergone radical gastrectomy and were found to have lymph node metastasis upon pathological examination were included. Histopathological samples were obtained from biopsies obtained during patient gastrectomies and lymph node dissection. HER2 status was evaluated by both immunohistochemistry (IHC) and silver in situ hybridization (SISH). Results: Sixty-four (79%) patients were SISH (-), while 17 (21%) were SISH (+) in the primary tumor. However, in metastatic lymph nodes, HER2 status was SISH positive in 5 (28.3%) of the 64 SISH (-) primary tumor specimens. One of the 17 SISH (+) primary tumors was SISH (-) in the metastatic lymph nodes. Thus, SISH results for HER2 in both primary tumors and lymph node metastases were comparable, showing a concordance of 92.5%. In total, six patients demonstrated discordance between the primary tumor and lymph node metastases. The prevalence of HER2 discordance was significantly higher for patients in the pN2 and N3 stages (p=0.007). Although discordant patients had worse survival rates than concordant patients, the differences were not significant (p>0.05).Conclusions: Our study indicates that the frequency of concordance in HER2 status, as determined by IHC or SISH, is high in primary tumors and their corresponding lymph node metastases for patients with gastric cancer. If there is a discrepancy in HER2 status, its evaluation by both IHC and SISH may be useful for detecting patients who would benefit from trastuzumab, and it would therefore help guide decision-making processes in administering treatment.

• 한국가족관계학회지
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• 제21권3호
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• pp.3-23
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• 2016

Objectives: The purpose of this study is to examine the effects of symptoms of dementia elderly on the primary caregiver's depression. In addition, moderating effect of family support was examined. Based on the results, the necessity for intervention in the level of social welfare as a way to mitigate primary caregiver's depression was suggested. Method: In order to accomplish these purposes, a total of 197 who are spouse and adult-children of dementia elderly using day care facilities or services in Seoul, Gyeonggi, Busan province, South Korea were utilized. Data were analyzed by frequency analysis and descriptive statistics, regression model analysis with SPSS 18.0. Results: In case of analysis results, the mean value was reported 0.9 out of four point about primary caregiver's depression and the mean value of family support was reported 3.34 out of five point. And besides, the analysis result of dementia elderly's symptoms showed that prevalence of depression/dysphoria were 62.2%, prevalence of aberrant motor were 61.3%, prevalence of apathy/indifference were 56.6%. Crucial findings are as follows: the symptoms of dementia elderly was significantly associated with the primary caregiver's depression. At the same time, family support significantly influenced lower level of the primary caregiver's depression. While, in the relationship between the symptoms of dementia elderly and the primary caregiver's depression, family support has a moderation effect by important protection factor. Conclusions: From these findings, the necessities to provide the care service for dementia elderly to help improve symptoms of dementia as well as the policy and service to manage the mental health of the family as primary caregiver were suggested. Also, the necessities to provide the family therapy program to improve the relationship with family members were suggested.

• 대한세포병리학회지
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• 제11권2호
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• pp.65-73
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• 2000

Cytologlc evaluation of cerebrospinal fluid(CSF) is an effective mean for diagnosing many disorders involving the central nervous systems(CNS). One of the most important reasons for cytologic examination of CSF is to detect metastatic or primary neoplasms of the CNS. We did a retrospective study of 1,438 CSF specimens obtained between 1992 and 1996. A total of 1,205 adult and 233 pediatric CSF specimens from 947 patients were accessed at the Department of Pathology of Seoul National University Hospital and Children's Hospital, respectively. Among 1,438 CSF cytology specimens, 169 cases(11.8%, 77 patients) including 135 adult cases(59 patients) and 34 pediatric cases(18 patients) were positive for malignant cells. Diagnoses included 50 metastatic carcinomas(adult, 60; pediatric, 0); 46 malignant lymphomas(adult, 44; pediatric, 2); 21 leukemias(adult, 20; pediatric, 1); 4 retinoblastomas(adult, 0; pediatric 4); 2 rhabdomyosarcomas(adult, 0; pediatric, 2); 1 multiple myeloma(adult, 1; pediatric, 0), and 35 primary CNS neoplasms(adult, 10; pediatric, 25). The most commonly identified metastatic carcinomas in adults were adenocarcinoma. Their primary sites were the lung, gastrointestinal tract, and breast in order of frequency. The most common primary CNS neoplasm in children was medulloblastoma.