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A Fault Tolerant Control Technique for Hybrid Modular Multi-Level Converters with Fault Detection Capability

  • Abdelsalam, Mahmoud;Marei, Mostafa Ibrahim;Diab, Hatem Yassin;Tennakoon, Sarath B.
    • Journal of Power Electronics
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    • v.18 no.2
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    • pp.558-572
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    • 2018
  • In addition to its modular nature, a Hybrid Modular Multilevel Converter (HMMC) assembled from half-bridge and full-bridge sub-modules, is able to block DC faults with a minimum number of switching devices, which makes it attractive for high power applications. This paper introduces a control strategy based on the Root-Least Square (RLS) algorithm to estimate the capacitor voltages instead of using direct measurements. This action eliminates the need for voltage transducers in the HMMC sub-modules and the associated communication link with the central controller. In addition to capacitor voltage balancing and suppression of circulating currents, a fault tolerant control unit (FTCU) is integrated into the proposed strategy to modify the parameters of the HMMC controller. On advantage of the proposed FTCU is that it does not need extra components. Furthermore, a fault detection unit is adapted by utilizing a hybrid estimation scheme to detect sub-module faults. The behavior of the suggested technique is assessed using PSCAD offline simulations. In addition, it is validated using a real-time digital simulator connected to a real time controller under various normal and fault conditions. The proposed strategy shows robust performance in terms of accuracy and time response since it succeeds in stabilizing the HMMC under faults.

Repeated Reading Experience of University Students (대학생들의 반복독서 경험에 관한 연구)

  • Lee, Seung-Chae
    • Journal of the Korean Society for Library and Information Science
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    • v.41 no.2
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    • pp.161-180
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    • 2007
  • The goal of this study is to examine what sort of books people read repeatedly, what are the different preferences between men and women, how much the repeatedly-read books are related to the most memorable books and how the repeatedly-read books are connected to reading habits. A questionnaire was provided to college students and their repeated reading experiences were searched. The results of the statistical analysis are summarized : 1) Most college students have experienced repeated reading more than twice. 2) The number of college students who have experienced repeated reading twice is the highest and next, those who have read repeatedly 3 times. Also, the number of times of repeated reading tends to be similar between male and female students. 3) The books which many students read repeatedly more than twice are : a) Romance of 3 Kingdoms b) Little Prince c) Da Vinci Code d) Alchemist e) Chinese nine spine stickle back f) Meu Pe do Larania Lima g) Harry potter. 4) About half of the students have read the most memorable books many times. 5) The importance of books was evaluated on the basis of the number of repeated readers and the number of readings. The order of the important books is Three Romans of 3 kingdoms, Little Prince, Da Vinci Code, Meu Pe do Larania Lima, Tuesdays with Mollie, Harry Potter, and The Myth of Greece and Rome. 6) The preferred books by male college students are mostly the stories of fighters while female likes books that contain deep emotion and morality. More than half of the males' repeated reading was Romance of 3 Kingdoms while the preferred books of females are distributed widely.

An Effective Multimedia Data Transmission in Ad-Hoc Networks Based on Bluetooth (블루투스를 이용한 애드혹 네트워크에서의 효율적인 멀티미디어 데이터 전송)

  • Kim, Byoung-Kug;Hong, Sung-Hwa;Hur, Kyeong;Eom, Doo-Seop
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.3B
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    • pp.112-122
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    • 2008
  • Basing on Piconet, The Bluetooth System forms network and transmits data. There is one Master and maximum 7 Slave bluetooth devices in one piconet. A job scheduler performed by Master bluetooth device, gives the chance of data transmission to Slave bluetooth devices, which connected to Master, using polling method in piconet. The maximum data rate is 723.2 kb/s when it uses ACL link with DH5 packet type in a piconet which is constructed by two bluetooth devices. However, if there are one master and two slave devices in a piconet, then the maximum data rate is reduced to a half(361.6kb/s), because a master device has to support same data rate for all connected devices. And, there is the defect in scatternet when data transmission rate becomes low(Maximum rate: 302.2kb/s). This paper proposals the new ad-hoc network topology called "DoublePico"for overcome the low data transmission in scatternet which is constructed by piconets. The method of doublepico that represented in this paper makes high data transfer rate(Maximum rate: 457.57kb/s) in bluetooth ad-hoc networks.

Repeated Reading Experience of Senior High School Girl: Centered on Jeonju Girls' High School Freshmen (여고생들의 반복독서 경험에 관한 연구 - 전주여고 1학년 학생들을 중심으로 -)

  • Lee, Seung-Chae
    • Journal of Korean Library and Information Science Society
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    • v.39 no.2
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    • pp.313-332
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    • 2008
  • The goal of this study is to examine what sort of books girl's high school students read repeatedly, what are the different preferences between high school and university students. how much the repeatedly-read books are related to the most memorable books and how the repeatedly-read books are connected to reading habits. A questionnaire was provided to Jeonju Girls' High School Freshmen and their repeated reading experiences were searched. The results of the statistical analysis are summarized: 1) Most girls' high school students have experienced repeated reading more than twice. 2) The number of girls' high school students who have experienced repeated reading twice is the highest and next. those who have read repeatedly 3 times. Also, the number of times of repeated reading tends to be similar between woman high school and College students. 3) The books which many students read repeatedly more than twice are : a) Little Prince b) The Myth of Greece and Rome c) Chinese nine spine stickle back d) Meu Pe de Larania Lima e) Giving Tree f) Harry Potter. 4) About half of the students have read the most memorable books many times. 5) The importance of books was evaluated on the basis of the number of repeated readers and the number of readings. The order of the important books is Little Prince, The Myth of Greece and Rome, Harry Potter, Giving Tree, Meu Pe de Larania Lima, Chinese Nine Spine Stickle Back.

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Strength Evaluation of Pinus rigida Miller Wooden Retaining Wall Using Steel Bar (Steel Bar를 이용한 리기다소나무 목재옹벽의 내력 평가)

  • Song, Yo-Jin;Kim, Keon-Ho;Lee, Dong-Heub;Hwang, Won-Joung;Hong, Soon-Il
    • Journal of the Korean Wood Science and Technology
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    • v.39 no.4
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    • pp.318-325
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    • 2011
  • Pitch pine (Pinus rigida Miller) retaining walls using Steel bar, of which the constructability and strength performance are good at the construction site, were manufactured and their strength properties were evaluated. The wooden retaining wall using Steel bar was piled into four stories stretcher and three stories header, which is 770 mm high, 2,890 mm length and 782 mm width. Retaining wall was made by inserting stretchers into Steel bar after making 18 mm diameter of holes at top and bottom stretcher, and then stacking other stretchers and headers which have a slit of 66 mm depth and 18 mm width. The strength properties of retaining walls were investigated by horizontal loading test, and the deformation of structure by image processing (AlCON 3D OPA-PRO system). Joint (Type-A) made with a single long stretcher and two headers, and joint (Type-B) made with two short stretchers connected with half lap joint and two headers were in the retaining wall using Steel bar. The compressive shear strength of joint was tested. Three replicates were used in each test. In horizontal loading test the strength was 1.6 times stronger in wooden retaining wall using Steel bar than in wooden retaining wall using square timber. The timber and joints were not fractured in the test. When testing compressive shear strength, the maximum load of type-A and Type-B was 130.13 kN and 130.6 kN, respectively. Constructability and strength were better in the wooden retaining wall using Steel bar than in wooden retaining wall using square timber.

Half a cenury of the rural geography in Korea(1945-1995):review and prospect (촌락지리학 50년(1945-1995)의 회고와 전망)

  • ;Lee, Moon-Jong
    • Journal of the Korean Geographical Society
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    • v.31 no.2
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    • pp.213-254
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    • 1996
  • The Korean Geographical Society was founded in 1945, when Korea was liberated from the Japanese rule. And The Journal of the Korean Geography activated academic studies of geography by publishing research papers in it. Professor Kang, Dae-Hyun wrote the first two specialized papers of rural geography in 1966: " Flood Plain Settlements on the Han River" and "The Location and Form of the Dispersed Villages around Dae-Cwan-Ryung". The early studies of rural geography were not based on serious academic foundations, such as the adjustment of theoretical notions and a good grasp of subjects. After choosing subjects that came to hand without academic consideration. they simply enumerated generalized items of the results of the field work investigation such as the location the landscape and the process of formation of the settlements. In the 1970s and 1980s, however, rural settlement studies progressed remarkably in Korea. More than 80% of 318 dissertations, theses, or papers collected for this review were written in the late 1980s, and the subjects and methodology became diversified. As may be expected, recent studies are found very systematic and problem-solving in the various fields - contexual understanding spatial structure, the development of clan villages according to the socialization process, the effects of rural-out migration on the change of villages etc. Such a trend can be understood as a reaction to the circumstances under which, as the Western society already experienced, rural villages become washed out by the waves of industralization and urbanization and hardly continue to exist. In this paper, geographical studies of rural settlement which have been carried out in Korea last fifty years will be reviewed under the four headings on the studies related to a) farming villages; b) fishing villages; c) mountain villages: and d) special function villages. Studies of farming villages and related ones are very diverse. The results of the studies carried out last fifty years can be classified into sixteen subjects. Just as, in the West, studies of rural settlement have been mainly concerned with farming villages since rural geography came into being, so, in Korea, they have been centred on farming villages. It is a natural result considering the history of human life. Even in Korea, however the rural settlement is no more an isolated life space which keeps unique traditions of old life style, but it begins to form a dynamic life space connected to big cities by heavy traffic. Because the modern farming villages of Korea have an undetachable connection with the cities, special methodology to solve new problems has been posed in the studies of rural settlement. Many scholars have produced a lot of studies of farming villages, and three of them are prominent: Oh. Hong-Seok, Choi, Ki-Yeop, and Lee, Moon-Jong. Oh, Hong-Seok is a versatile and hard-working scholar who has published more papers than anyone else in the various fields of rural geography such as farming villages, fishing villages, mountain villages, and reclamation villages. And he has expanded his concerns to environment issues in recent years. Choi, Ki-Yeop has maintained that the prototype of Korean rural villages is clan villages continuing to write a series of good papers in which he pursues their regionalizion in the process of socialization. Lee, Moon-Jong divides the spatial organization of side settlement, sahachon (settlement near the temple), religion settlement, orchard settlement, settlement near the foreign military camp, displaced people's settlement. Chung Gam Lok settlement, etc. Though The Korean Geographical Society has half a century's history, academic activties in the field of rural settlement have been performed no more than thirty years. We cannot help saying that it is admirable that in such a rather short time we have five academical schools of the rural geography in Korea. geography in Korea.

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A Study on Health Seeking Behavior - Focused on Shopping-Around Phenomenon in Banwol-Eup Residents (일부(一部) 지역사회(地域社會) 주민(住民)의 의료(醫療) 행태(行態)에 관(關)한 연구(硏究) - 반월읍(半月邑) 주민(住民)의 Shopping-around 현상(現象)을 중심(中心)으로 -)

  • Choi, Young-Teak;Lee, Eun-Il;Kim, Hyo-Joong
    • Journal of agricultural medicine and community health
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    • v.11 no.1
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    • pp.44-54
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    • 1986
  • This study was aimed at investigating the health seeking behaviors of patients; For the purpose of analyzing the research theme we classified the study into two phase. First, the types of patients' health seeking behavior were categorized into a scheme according to what medical care resources were utilized in patients' coping process. Second, from patients' first visits to third visits to medical resources, we analyzed variations of factors which noted as crucial elements in constituting the patients' sickness career. To grasp the generalized characteristics from complicated empirical data, we limited the scope of our analysis to third stage of health seeking. A total of 121 persons who had beer suffering from chronic diseases more than 3 months was sampled among the residents of Banwol-Eup, the target Area of Korea University Health Project. The findings are as follows ; 1) In the course of visiting medical care resources, 34 different types of health seeking Behavior were found. From this result we inferred the idea that patients in Banwol-Eup had not any stable norms to cope with their pains. Clinics, hospital, pharmacy, Herb-doctors', folkways (self-treatment) were accessed by patients in orders. But more than half of patients who had utilized clinics or hospitals from their first to third visits, changed medical care resources to others, for example herb doctors or folkways, which had fundamentally different treatment models. Upon these two facts, the diversified types and capricious patterns in the health seeking behavior of Banwol patients, we observed a typical Shopping-Around phenomenon. 2) Factors which influenced patients' to their sickness career were changed along the courses of health seeking, from first to third visits as follows ; $\cdot$ Perceived seriousness of diseases were tended to decrease. $\cdot$ Professional medical personnel tended to be influencial in the patients' sickness career, (5.0%, 25.0% and 65.7%). The influence of the primary interaction groups such as parents, friends, neighbours, tended to decrease ; (90.9%, 71.2% and 30.0%). $\cdot$ The subjective reasons why to choose such a medical care resource were related to economic affordability and disease-itself as main motives. Credibility of health resources tended to increase 14.9%, 24.0% and 31.4 sequently. $\cdot$ Geographic accessibility factors did not change significantly. Most of patients had utilized health resources in Banwol and Anyang area. 3) Cultural inclination in the shopping-around phenomenon has shown difference among age groups. The age group' over 50 years' preferred traditional health resources to modern health resources. 4) Consistency of health seeking behavior on the shopping around phenomenon has shown difference according to the degrees of patients' economic affordability and those of psychological satisfaction toward modern health services. However, there were some restrictions in this thesis ; a) the study was limited to the 3rd health seeking career so it did not allow us to collect more informations after that, b) the study was not able to carry out causal analysis on patients health behavior determinated by explanatory model of health resources, and c) the study was not able to take into consideration of factors connected with social structural circumstances. Despite of restrictions described above, we are sure that this thesis would promote health providers' understanding toward patients' inclinations, through which they could provide efficient and accurate medical service.

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