스털링기관 재생기내의 작동유체 유속 및 마찰저항 특성(II)-작동유체 유동마찰저항 특성-

김태한,조창래 한국농업기계학회 2008 바이오시스템공학 Vol.33 No.1

The output of the Stirling engine is influenced by the regenerator effectiveness. The regenerator effectiveness is influenced by heat transfer and flow friction loss of the regenerator matrix. In this paper, in order to provide basic data for the design of regenerator matrix, characteristics of flow friction loss were investigated by a packed method of matrix in the oscillating flow as the same condition of operation in a Stirling engine. As matrices, two different wire screens were used. The results are summarized as follows; 1. With the wire screen of No.50 as regenerator matrices, pressure drop of working fluid of the oscillating flow is shown as 3 times higher than that of one directional flow, not too much influenced by the number of packed meshes. 2. With the wire screen of No.100 as regenerator matrices, pressure drop of working fluid of the oscillating flow is shown as 2.5 times on the average higher than that of one directional flow, not too much influenced by the number of packed meshes. 3. Under one directional flow which used regenerator matrices with both 200, 240, and 280 wire screens of No. 50 and 320, 370, and 420 wire screens of No. 100, the relationship between the friction factor and Reynold No. is shown as the following formula. (수식) 4. Under oscillating flow which used regenerator matrices with both 200, 240, and 280 wire screens of No. 50 and 320, 370, and 420 wire screens of No. 100, the relationship between the friction factor and Reynold No. is shown as the following formula. (수식) 5. The pressure drop is shown as high in proportion as the number of meshes has been higher, and the number of packed wire screens as matrices increases.

주식간 정보흐름의 시간의존성 및 새로운 접근법 연구

엄철준(Cheoljun Eom) 한국자료분석학회 2007 Journal of the Korean Data Analysis Society Vol.9 No.3

재무분야에서 정보흐름에 관한 연구주제는 금융시장에서 발생하는 복잡한 자산간의 상호작용 및 그 자산들의 가격결정과정을 이해하는데 도움이 되기 때문에, 많은 연구자들이 관심을 갖는 중요한 연구과제이다. 우리는 주식간 정보흐름의 검증결과에 공통적으로 영향을 미칠 수 있는 시간의존성 및 그 영향요인들을 체계적으로 관찰하고자 한다. 시간의존성과 관련된 영향요인으로는 수익률의 측정기간단위, 과거자료의 시차길이, 그리고 시장상황의 변화 등이 있다. 검증자료는 한국뿐만 아니라 미국, 일본, 영국의 각 주식시장의 시장지수를 구성하는 개별주식자료를 이용하였다. 관찰결과를 요약하면 다음과 같다. 첫째, 인과관계모형으로부터 도출된 주식간 정보흐름의 검증결과는 수익률 측정기간단위와 과거자료 시차길이의 변화에 따라 의미 있는 영향을 받는다는 것을 확인하였다. 둘째, 주식간 정보흐름의 검증결과는 시장상황의 변화에 따라 시간가변적 속성을 가졌다. 셋째, 시계열자료의 시간 순서를 무작위로 섞음으로써 시간속성을 통제하였을 때 더 이상 의미 있는 주식간 정보흐름을 관찰할 수 없다. 이상의 결과에서, 주식간 정보흐름의 검증결과는 강한 시간의존성을 갖는다는 것을 체계적으로 확인할 수 있었다. 그리고, 개별주식과 같이, 다양화된 대용량자료를 사용한 정보흐름 검증과정을 수행하고자 할 때, 주식 네트워크 방법이 보다 효과적인 방법임을 알 수 있었다. Our goals were to investigate the properties of time dependency in terms of information flow as well as to find empirical evidence of the possible factors that can affect information flow. In order to observe the properties of information flow, we must consider various factors, such as the time scales of return, the lag length of past data to the model, the sequence of time, and market status. We established the above factors by inducing significant changes in the results of the information flow, and we compared those changes to the results for each factor. However, to sufficiently observe the information flow between stocks, it was difficult to consider the number of whole connections between stocks. Because, the number of whole connections between stocks is N( N -1)/2. To investigate information flow effectively, we suggest analyzing the stock network by using the minimal spanning tree(MST) method. This method chooses N-1, the most important links consisting of individual stock prices in the financial market. And we used various individual stocks traded in diverse countries such as America, the UK, Japan, and Korea. According to the results, we discovered that the information flow between stocks observed by the causality model was significantly influenced by the changes of time scales of return and the lag length of past data. That is, the relationship between the time scale of return and the frequency of significant information flow is negative, while the relationship between the lag length of past data to causality model and the frequency of significant information flow is positive. Furthermore, as using the time series removed the temporal time correlation, we could not find significant information flow for the previous results. We also found that information flow between stocks have time-varying properties according to market status. That is, the information flow between stocks have properties of time-dependency. Therefore, if researchers would like to study information flow between assets or markets, they need to consider the properties of time dependency and other possible factors.

인구이동 플로의 연령-특수적 패턴 분석을 위한 방법론 연구 - 우리나라 시군구 단위 인구이동에의 적용 -

이상일(Sang-Il Lee),김현미(Hyun-Mi Kim) 대한지리학회 2021 대한지리학회지 Vol.56 No.5

본 논문의 주된 연구 목적은 인구이동 플로의 연령-특수적 패턴을 분석하기 위한 새로운 방법론적 대안을 제시하는 것이다. 새로운 방법론을 구성하는 가장 중요한 요소로 세 가지 사항이 집중적으로 다루어 진다. 우선 전통적인 O-D 매트릭스 대신 하위 인구 집단의 플로 속성이 변수로 다루어 질 수 있는 다이아딕 매트릭스의 적극적인 사용이 제안된다. 둘째, 인구이동 플로를 표준화하는 측도로서 플로 SSD가 제시된다. 플로 SSD는 방향적 지역쌍별로 특정 연령 집단에 대한, 규모를 감안한 플로 특화도를 측정해 준다. 셋째, 연령 집단별 인구이동의 플로 SSD 값을 변수로 투입한 PCA의 활용이 제안된다. 분석 프레임워크의 적용성을 평가하기 위해 2020년 우리나라 시군구 단위 인구이동 데이터를 분석하였다. 26,082개의 방향적 지역쌍과 18개의 연령 집단으로 이루어진 다이아딕 매트릭스를 구성하였고, 개별 연령 집단별 이동량을 플로 SSD를 활용해 표준화하여, 다이아딕 PCA 분석에 최종 투입하였다. PCA의 결과, 네 개의 PC가 총변동의 거의 80%를 설명하며, 개별 PC는 인구의 생애 주기와 관련된 특징적인 인구이동 양상을 포착하는 것으로 드러났다. 결론적으로, 본 연구에서 제안된 방법론은 인구이동 플로의 연령-특수적 패턴을 분석하는데 매우 유용한 것으로 평가되었다. The main objective of this paper is to propose a new analytical method for age-specific patterns in migration flows. It is composed of three key elements. First, the use of dyadic matrices as opposed to the traditional O-D matrices is strongly recommended to present age-specific migration flows as variables in a multivariate data set. Second, the flow SSD (standardized score of dissimilarity) as a flow standardization technique is proposed and is expected to capture the degree of flow specialization of each directional region pair in a particular age group with consideration of flow amount. Third, a dyadic PCA (principal component analysis) technique is proposed by employing the standardized flow SSD values as input variables. In order to assess the applicability of the proposed analytic framework, an analysis is conducted for inter-regional migration flows in South Korea, 2020. A dyadic matrix composed of 26,032 directional region pairs and 18 age group flow variables is prepared. The variables then are standardized and subsequently input into a dyadic PCA. The four PCs explain almost 80% of the total variances, and each PC appears to capture a particular facet of migration flows which is associated with a particular stage of life cycle. In conclusion, the method proposed in this paper appears to be a plausible analytical alternative to investigate age-specific patterns in migration flows.

통근통행에 의한 직⋅간접 흐름을 이용한 지역의 중심성 분석

이종상,서덕수 한국농촌지도학회 2020 농촌지도와 개발 Vol.27 No.3

The regional centrality plays a very important role in national and regional planning and it is measured by data such as people, goods, and information flows among regions. The inter-regional flows are usually considered by only direct flows, yet indirect flows, which are generated accordingly from direct flows, are not critically considered. Most centrality studies have also hardly reflected the indirect flow in the network analysis. This study demonstrates the significance of the indirect flows to enhance accuracy of the regional centrality. The nationwide dataset of inter-regional commuter traffic matrix is used in this study and analysed into two groups; one to consider only direct flow and the other both direct and indirect flows. The results indicate remarkable differences of centrality raking between two groups such as Yeongam of Jeonnam Province(+60th), Eumseong of Chungbuk Province(+57th), Gwacheon of Gyeonggi Province (-35th), and Nowon of Seoul (-32nd). It clearly shows the significant influence of indirect flow for regional centrality study. This also reveals regional centrality ranking in Korea by considering direct and indirect flows of commuters. Jung, Gangnam, and Jongno of Seoul are categorized in the highest rank group and Ulleung of Gyeongbuk, Ongjin of Incheon, and Jindo of Jeonnam are in the lowest group. The top group includes seven districts of Seoul, two of Busan, and one of Gyeonggi Province. The bottom group includes mostly island and costal areas. As this study shows an accurate method of centrality measurement, it has a significant implication to lead an effective regional planning.

미숙아에서의 Germinal matrix출혈의 위험 인자와 뇌 혈역동학적 인자에 대한 연구

김민정,조은영,김성우 동국대학교 의학연구소 2008 東國醫學 Vol.15 No.1

미숙아의 신경학적 후유증을 남길 수 있는 germinal matrix 출혈(Germinal matrix hemorrhage, GMH), 뇌실 내 출혈의 위험인자와 혈역동학적 인자와의 관계에 대해 알아보기 위하여 이번 연구를 시행하였다. 2006년 8월부터 2007년 8월까지 동국대학경주병원에서 분만된 신생아 중 재태 기간 34주 이하의 미숙아 54명을 대상으로 연구하였고, 뇌 도플러초음파검사는 생후 1주 이내와 20일 이후에 최소한 2번 이상 시행하였다. 촬영 후 방사선과 전문의의 판독에 따라 당시의 최고 및 최저 cerebral blood flow velocity(CBFV)와 resistance index(RI)를 분석 비교하였다. 또한 GMH의 알려진 주산기 인자, 분만 방법 및 신생아기 위험인자에 대해 분석하였다. 전체 54명 중 11명(20.3%)이 GMH 및 뇌실확장이 동반된 GMH으로 진단되었다. 뇌 도플러초음파를 시행한 결과 통계적으로 유의하지 않았으나 GMH군에서 최고 CBFV(38.42±13.87)은 정상군(38.45±8.96)보다 낮았으며, 최저 CBFV값(12.09±6.79)은 정상군(10.85±3.48)보다 높았다. RI값도 두 차례 전부 GMH군이 정상군보다 낮았으나 통계적으로 유의하지 않았다. GMH의 주산기 및 신생아기 위험인자들을 조사한 결과 산모의 전자간증만이 통계적으로 유의하게 높았다(p<0.05). 이번 연구에서 주산기 뇌출혈이 있는 환아의 뇌혈류증가량이 병변이 없는 환아보다 적으며, 이로 인해 뇌 허혈이 생겨 뇌백질의 손상이 지속되고 뇌실확장, 뇌실주위백질연화증과 같은 합병증이 동반되는 것으로 보인다. 따라서, 신경학적 후유증으로의 이행을 예측할 수 있는 뇌초음파 도플러 검사와 같은 좀 더 정확한 방법에 대한 많은 연구가 필요할 것으로 생각된다. The purpose of this study is to investigate the relation among cerebral blood flow and germinal matrix hemorrhage (GMH) using Doppler ultrasonography and risk factors in 54 preterm infants with gestational age less than 34 weeks. Eleven of 54 preterm infants delivered from August 2006 to August 2007 were diagnosed through ultrasonography as having GMH. Cerebral blood flow of posterior cerebral artery was assessed at within the first 7days and the 30days of the life. Maximum and minimum of blood flow and resistance index (RI) of posterior cerebral artery were calculated from the data obtained by Doppler ultrasonography. We also reviewed their medical records retrospectively. We analyzed the obtained data using the SPSS for Windows 14.5 program, Mann-Whiney U test and Wilcoxon Signed rank test. The incidence of GMH is 20.3%. The only maternal preeclampsia had statistical meaning among the known risk factors (p<0.05). On the fifth day of life, RI was 0.70 ± 0.10 in infants with GMH and 0.72 ± 0.06 in those without GMH. On the 22th day of life, RI was 0.75 ± 0.04 in infants with GMH and 0.76 ± 0.06 in those without GMH. The RI was lower in infants with GMH at either point, but there is no significance. Blood flow velocity was also lower in infants with GMH without significance. Although there is not statistically significant, the results suggestive of vasoparalysis in such infants at the level of major cerebral arteries. We suggest that the total cerebral blood supply is decreased in cases of GMH and this reduction occurs within 7th day of life. By way of regular follow-up with Doppler ultrasonography, careful observation of neurological problem must be given to infants diagnosed GMH at first ultrasonography.

스털링 기관용 재생기에 관한 기초 연구 (IV) - 철선을 축열재로 한 재생기의 전열 및 유동손실 특성 -

오대건,김태한,Oh D. G.,Kim T. H. 한국농업기계학회 2005 바이오시스템공학 Vol.30 No.4

The output of Stirling engine is influenced by the regenerator effectiveness. The regenerator effectiveness is influenced by heat transfer and flow friction loss of the regenerator matrix. In this paper, in order to provide a basic data for the design of regenerator matrix, characteristics of heat transfer and flow friction loss were investigated by a packed method of matrix in the oscillating flow as the same condition of operation in a Stirling engine. As matrices, 6 kinds of steel wires, 4 kinds of combined steel wires, 8 kinds of combined steel wires with screen meshes were used. The results are summarized as follows; Among 6 kinds of steel wires $({\phi}0.7\;mm,\;{\phi}0.9\;mm,\;{\phi}1.2\;mm,\;{\phi}\;1.6\;mm,\;{\phi}2.0\;mm,\;{\phi}2.7\;mm),$ the two steel wires $({\phi}0.7\;mm,\;{\phi}0.9\;mm)$ showed the highest in effectiveness. Among 4 kinds of combined steel wires $({\phi}l.6-{\phi}l.2\;mm,\;{\phi}1.2-{\phi}l.6\;mm,\;{\phi}0.9-{\phi}l.2\;mm,\;{\phi}l.2-{\phi}0.9\;mm),\;the\;{\phi}1.2-{\phi}0.9\;mm$ showed the highest in effectiveness. Among 8 kinds of combined steel wires with screen meshes $(150-{\phi}0.9\;mm,\;150-{\phi}l.2\;mm,\;{\phi}0.9\;mm-150,\;{\phi}1.2\;mm-150,\;150-{\phi}0.9\;mm-150,\;150-{\phi}1.2\;mm-150,\;150-{\phi}l.6\;mm-150,\;150-{\phi}2.0\;mm-150),\;the\;{\phi}l.2\;mm-150$ showed the highest in effectiveness.

스털링 기관용 재생기에 관한 기초 연구 (III) - 복합메쉬 철망을 축열재로 한 재생기의 전열 및 유동손실 특성 -

이시민,김태한,Lee S. M.,Kim T. H. 한국농업기계학회 2005 바이오시스템공학 Vol.30 No.4

The output of Stirling engine is influenced by the regenerator effectiveness. The regenerator effectiveness is influenced by heat transfer and flow friction loss of the regenerator matrix. In this paper, in order to provide a basic data for the design of regenerator matrix, characteristics of heat transfer and flow friction loss were investigated by a packed method of matrix in the oscillating flow as the same condition of operation in a Stirling engine. As matrices, several kinds of combined wire screen meshes were used. The results are summarized as follows; The packed meshes with high mesh no. in the side of heater part of regenerator showed effective than the packed meshes with low mesh no. in the side of cooler part of regenerator. The temperature difference and pressure drop of the regenerator were not made by the specific surface area of wire screen meshes but by the minimum free-flow area to the total frontal area. Among the No. 150 single screen meshes, 200-60 combined meshes, the 200-150-100 combined meshes showed the highest in effectiveness.

O-D행렬에서 간접류의 재해석과 계산방법의 개선

이종상(Lee, Jong-Sang) 한국지역개발학회 2007 韓國地域開發學會誌 Vol.19 No.2

The graph theory method which is developed by Nystuen & Dacey(1961) has been widely applied for nodal regionalization by using interaction O-D matrices. One desirable property of the Nystuen & Dacey model is the inclusion of indirect flows in addition to direct flows. But there are some problems in this model, its names, the interpretation and magnitude of indirect flows. The results of this study are as follows: ① there are no indirect flows by way of direct flows concerning flows such as passengers, commodities, and money itself. Thus, it is not necessary to consider indirect flows. Indirect flows is interpreted as transfer of information through passengers, commodities, and money among regions; ② The proper adjacency matrix is aij=xij/Pj. The Nysten & Dacey model and the new model to the trips of commuters in Jejs Prefecture was applied in this study. By comparison, the new model proved to be more appropriate to the information transfer by direct commuters. Therefore, the new model was found to be more useful.

Harmonic and Resonance Analysis of High-speed Train-network Coupling Systems Based on Harmonic Admittance Matrix Model

Bohong Li,Fei Lin,Mengyue Zhou 보안공학연구지원센터(IJUNESST) 2015 International Journal of u- and e- Service, Scienc Vol.8 No.1

To study the impact of fundamental flow and background harmonics on harmonic and resonance characteristics of high-speed train-network coupling systems, harmonic admittance matrix model for four quadrant converter is deduced with the method of FFT and Bessel function. Equivalent load of train and chain network model of multiple conductors was established to conduct the calculation of fundamental and harmonic flow. Based on all of these, realize the harmonic and resonance research of train-network coupling system with multiple trains, which offer the reference to safe operation and avoid the voltage peaks in actual supply network.

Tracing solute infiltration using a combined method of dye tracer test and electrical resistivity tomography in an undisturbed forest soil profile

Kim, Jae Gon,Park, Sam-Gyu,Yi, Myeong-Jong,Kim, Jung-Ho John Wiley Sons, Ltd. 2010 Hydrological processes Vol.24 No.21

<P>An accurate prediction of solute infiltration in a soil profile is important in the area of environmental science, groundwater and civil engineering. We examined the infiltration pattern and monitored the infiltration process using a combined method of dye tracer test and electrical resistivity tomography (ERT) in an undisturbed field soil (1 m × 1 m). A homogeneous matrix flow was observed in the surface soil (A horizon), but a preferential flow along macropores and residual rock structure was the dominant infiltration pattern in the subsurface soil. Saturated interflow along the slopping boundaries of A and C1 horizons and of an upper sandy layer and a lower thin clay layer in the C horizon was also observed. The result of ERT showed that matrix flow started first in A horizon and then the infiltration was followed by the preferential flows along the sloping interfaces and macropores. The ERT did not show as much detail as the dye-stained image for the preferential flow. However, the area with the higher staining density where preferential flow was dominant showed a relatively lower electrical resistivity. The result of this study indicates that ERT can be applied for the monitoring of solute transportation in the vadose zone. Copyright © 2010 John Wiley & Sons, Ltd.</P>