Effect of Impact Velocity on Interface Characteristics of HT‑9 Steel Joints Fabricated by Magnetic Pulse Welding

Jun‑Woo Song,Jin‑Ju Park,Gyoung‑Ja Lee,Min‑Ku Lee,Kyu‑Hyun Park,Soon‑Jik Hong,Jung Gu Lee 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.3

The weldability window in magnetic pulse welding (MPW) is proposed for the end-closure joining of HT-9 steel tubularworkpieces. Based on both theoretical and experimental investigations, the impact velocity of the flyer tube at the momentof collision had a dominant effect on the bonding characteristics of the resultant joints and the optimal impact velocity wasestimated to be in the range of 265–290 m/s in this alloy system. Under the optimal process conditions, no leak was detectedduring helium leak testing. Moreover, the integrity of the joint interface was preserved until the tube section ruptured duringinternal pressure burst testing. For HT-9 steel, the ductile δ-ferrite phase produced by the localized interfacial melting duringMPW acted as an effective obstacle to crack propagation, thereby enhancing the fracture resistance of the joint interface. Allof the results demonstrated the high integrity and durability of the HT-9 steel tube assembly fabricated by the MPW process.

이온교환체로서 Polyphenylene Sulfide Sulfonic Acid에 관한 연구

전병광,손원근,서구원,맹학영,김동철,송해영 충남대학교 공업교육연구소 1994 論文集 Vol.17 No.1

Sulfonated poly(phenylene sulfide)(S-PPS) was prepared by the reaction of poly(phenylene sulfide)(PPS) with fuming sulfuric acid. The sulfonation was confirmed by the high intensity band of the SO_3H group at 1190 cm^-1. Thermally crosslinked S-PPS was used for a cation exchange polymer with high thermal stability. The ion exchange capacity of soluble S-PPS(H-form) and insoluble S-PPS(H-form) was 5.16meq/g and 3.50meq/g, respectively. The ion exchange capacity and IR absorbance at 1190cm^-1 of S-PPS were decreased as the curing temperature was increased.

용사코팅용 나노 WC-12Co 피드스톡의 제조

전형우,김주선,박준영,박종구,황순영,이해원 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.4

This study investigates the fabrication of WC-12Co feedstock powders with weakly locculated slurries by spray drying under various conditions. The morphological defects and flocculation states according to the amount of additives are evaluated to prepare spherical WC-Co feedstock powders with little morphological defects and homogeneous microstructures. The characteristics of feedstock powders, heat treated between 850-1200℃, are analyzed via SEM, EPMA, and mercury porosimetry. The results showed that with the increase in heat treatment temperature the portion of larger pores around 10 μm increased while, that of smaller pores of 1 μm lessened due to the coalescence of WC particles, forming dense feedstock powders with little defects such as hollow or craters. The feedstock heat treated at 1200℃ showed a porosity of 42.2% and a density of 8.28 g/cm^(3) as well as uniform distribution of pores and Co. (Received January 19, 2004)

프랑스 지방자치의 역사적 발전과 교훈

배준구 慶星大學校 1997 論文集 Vol.18 No.2

Chaque pays a des traditions particulieres, qui ont influence dans le sens de la centralisation ou dans celui de la decentralisation. La Fance comme la Coree peut etre classee, traditionnellement, parmi les Etats qui reconnaissent un role essentiel aux administrations centrales. Pour la coree, 1995 marqua la reprise de la decentralisation, et pour la France, depuis 1982 la profonde reforme est aussi entreprise en coreens maintes similitudes, et le travail d'ajustement que requiert la reprise du processus de decentralisation peut s'inspirer de l'exemple francais. L'objet de ce travail est de donc faire ressotir les caraterisques des grandes grandes etapes de la decentralisation en France et les lecons de la experience francaise par rapport au contexte coreen. L'observation de l'exemple francais peut inspirer le travail de redressement de l'administration locale coreenne, par l'adoption des elements positifs: la mise en mouvement de la deconcentration(avec l'affirmation de la Region) qui a accompagne la decentralisation, la nouvelle repartition des competences decoulant du systeme des attributions specifiques, la suppression du controle administratif et financier, la reglementation des conditions d'exercice des mandats locaux, le progres de la cooperation intercommunale, la planification decentralisee par l'elaboration de contrats de plan entre l'Etat et la region. Par contre, les quatre constats doivent etre exprimes qui imposent des reorientations: l'augmentation du nombre d'echelon administratifs, les collectivites de base ne retirant pas de la repartition des competences les benefices qu'elles etaient en droit d'attendre, l'accentuation de la politisation, une coloration tres etatique de la competence et les credits.

자율신경계의 활성도 측정을 위한 Data Acquisition System의 개발 및 임상응용

신동구,박종선,김영조,심봉섭,이상학,이준하 영남대학교 기초/임상의학연구소 2001 Yeungnam University Journal of Medicine Vol.18 No.1

Background: Power spectrum analysis method is a powerful noninvasive tool for quantifying autonomic nervous system activity. In this paper, we developed a data acquistion system for estimating the activity of the autonomic nervous system by the analysis of heart rate and respiratory rate variability using power spectrum analysis. Materials and methods: For the detection of QRS peak and measurement of respiratory rate from patient's ECG, we used low-pass filter and impedance method respectively. This system adopt an isolated power for patient's safety. In this system, two output signals can be obtained: R-R interval(heart rate) and respiration rate time series. Experimental ranges are 30∼240 BPM for ECG and 15∼80 BPM for respiration. Regults: The system can acquire two signals accurately both in the experimental test using simulator and in real clinical setting. Conclusion: The system developed in this paper is efficient for the acquisition of heart rate and respiration signals. This system will play a role in research area for improving our understanding of the pathophysiologic involvement of the autonomic nervous system in various disease states.

MBOD법에 의한 만경강 수계의 조류성장잠재력 평가

김종구,김준우 한국환경과학회 2004 한국환경과학회지 Vol.13 No.9

The modified biochemical oxygen demand (MBOD) were conducted to evaluate the water quality and fertility in the Mangyeong river from november 2002 to april 2003. MBOD method was used to evaluate algal growth potentials and their limiting factors. MBOD depends on the amount of available inorganic nutrient and organic substrate during 5-day incubation in the dark condition at 20℃. The MBOD assay depends on inorganic nutrients such as phosphorus and nitrogen as well as reduced carbon as called MBOD, MBOD-P, and MBOD-N, respectively. The concentration of pollutants were in the range of 3.08~48.36 mg/L for COD. The concentration of nutrients were in the range of 0.37~111.62 mg/L for dissolved inorganic nitrogen (DIN) and 0.00~1.03 mg/L for dissolved inorganic phosphorus (DIP). The results of MBOD bioassay showed that the MBOD, MBOD-P and MBOD-N values were 15~173 mg O₂/L, 13~165 mg O₂/L and 66~175 mg O₂/L ranges, respectively. The MBOD values are found to be the highest in Iksan River and the lowest in Hari River throughout the Mangyeong River. The relationships of MBOD, MBOD-P and MBOD-N in MBOD method were generally found in MBOD MBOD-P≒MBOD-N. But the result of Gosan was appeared to MBOD≒MBOD-N>MBOD-P. The MBOD-N value was higher 3 to 5 times than the MBOD-P value in the Gosan station. The algal growth potentials expressed as the concentration of chlorophyll-a were maximum 20 times more than algal biomass in the water column.

不良住宅地區의 政策方案에 關한 硏究 : 서울市 不良住宅地區의 住居實態分析을 中心으로

裵俊銶,李盛根 嶺南大學校社會科學硏究所 1982 社會科學硏究 Vol.2 No.2

1. Introduction In a rapidly developing and urbanizing country like Korea, housing has significant economic, social and political ramifications. Rapid urbanization has taken place primarily because the rural poor have migrated into large cities for employment opportunities and better living conditions. Consequently urban housing has become scarce in quantity, expensive in price, and overcrowded to the extent that doubling-up and tripling-up are commonplace. Coincident with these problems is that of the urban squatter settlements, which have become widespread and generate tremendous urban problems. The Korean government has devised numerous measures to tackle the squatter problem. The government's effort has been successful only in a limited sense; it improved the city's physical appearance through slum clearance and renewal. It is, however, subject to serious criticisms; and two of them are particularly significant: inconsistency in policies which often resulted in waste of resources, and deprivation of the individual rights of those directly affected. Another, equally serious as these, has to do with the intolerable financial burden that relocates have to bear. Such criticisms have forced the government to change its policy direction; and the recently considered, new policy measures are geared to selective redevelopment, and immediate legalization, with revised housing standards for squatters. Although it has not yet materialized, the idea is highly commendable. Obviously, more in-depth studies must be carried out; and a set of alternative courses of action generated and evaluated in terms of the legal, institutional and financial implications of each before the new policy is firmly set. Additionally, the on-going policies and programs ought to be rigorously assessed to gain insight from past experience. 2. The Definition of Squatter Dwellings The first question that must be answered is, what is a squatter home? The definition should differ from one country to another, depending upon the degree of squatter settlement concentration and the definition of housing quality and/or standards. The most difficult task in the process of defining substandard housing is to clarify the difference between a substandard unit and an illegal unit. Normally the degree of substandardness is measured in terms of qualitative housing standards, whereas illegal housing is defined simply by the absence of a legal title to the property. A.L. Mabogunje points out that the first step is measuring habitability is to consider the various types of functions that standards are meant to perform in shelter provision. In reviewing the standards for shelter provision, especially in developing countries, he offered a threefold division as follows; 1) Space-Use and Density Standards; 2) Health and Sanitation Standards; 3) Community Facilities and Services Standards. The first category includes minimum lot sizes, number of buildings per unit area, building bulk per unit, number of persons per room or number of persons per area. The second grouping, technological or performance standards, is intended to define the quality of environment, particularly in terms of the quality of construction, the type of materials that must be used, the quality of services that can be offered, or tolerable levels of toxicity. The third grouping defines the lower and upper limits of the size of population, and the area or distance to be served by particular amenities or community facilities. In Korea, however, the measuring criteria for substandard housing are primarily physical and legal. The Ministry of Construction (MOC) utilizes criteria somewhat a mixture of substandard and illegal housing as follows: -floor area is less than 7pyong (substandard) -illegal housing on public land (illegal) -housing without permission (illegal) -housing with inadequate building materials such as shacks (illegal or substandard) -lacking utilities such as electricity, water, and sewer etc, (substandard or illegal) The criteria used by the City of Seoul are similar to those of the MOC. The acquisition of proper title and building permission are two major legal criteria. According to these criteria, substandard housing includes both the legal but physically substandard as well as all illegally built housing. In this paper, therefore, the term (squatter) refers to both these categories of housing; i.e., legally and properly titled but substandard housing, and illegally built, improperly titled housing. 3. An Overview of the Squatter Areas Conditions 1) Physical conditions -materials of dwelling are used more durable materials compared to 1970, for example, cement bricks etc. -size of house became larger than '70, but under half of Seoul average. -total number of room per dwelling is almost equal to Seoul average, but total number of room used by a household is smaller than Seoul average. -housing facilities (sanitary etc.) became better than '70, but sanitary, sewage and waste disposal conditions are unhealthy and insufficient. -in summary physical condition and dwelling density are unhealthy, insufficient and overcrowded compared to Seoul average level. 2) Social conditions -a number of person per household is more than Seoul average, and the preferance to boy is stronger than the other survey areas. -the composition rate of traditional family is higher than Seoul average, and a number of tenements in dwelling is more than Seoul average. -occupations of household head are mainly unskilled workers and cottage industry workers. -the relationships of neighborhood and social networks are very friendly close and intimate. -they show strong interest to the redevelopment program of squatter communities. -residents don't to migrate long distance in a city, instead of moving to near squatter communities. -the period of settlement in present location is mainly before 1970. -present housing areas are considered as essential and critical base for their economical opportunities. 3) Economic conditions -monthly income don't reach to Seoul average, but it has increased compared to '70. -especially, the propensity to saving is high. -house prices and rents in squatter communities are cheaper than the other areas. 4. An Overview of The Redevelopment Policy The early squatter clearance projects, such as building clearance program, citizens apartment program, were ineffective. Squatter settlements policy has been ill-conceived and misguided; squatter settlements were regarded simply as a social disease and the people's welfare was totally overlooked. The City of Seoul enacted the Housing Rehabilitation Act in 1973. The act stipulated that local government would provide infrastructure and community services, and it allowed the government to take full control over the rehabilitation projects of squatters. With this legal support the city prepared the rehabilitation plan for 126,000 units by means of upgrading rather than relocation. The impact of the rehabilitation project was minor at best. The project failed to relate itself to the affordabilities of low income squatter families. Recognizing the failure of the housing rehabilitation policy for squatters provided by the Housing Rehabilitation Act of 1973, the City of Seoul strived to implement the redevelopment policy by means of clearing out squatter homes and constructing new dwelling units, mainly multifamily units, on the same sites. This approach began with the premise that an efficient and effective redevelopment policy should be well coordinated with overall city functions, such as location, community facilities, etc., and consider aesthetic factors as well. The government adopted the Urban Renewal Act in 1976 (December 31), replacing the Urban Redevelopment section of the City Planning Act which had been established after the Korean war (1950-1953). The renewal act of 1976 provided criteria for designating a redevelopment area, the qualifications of an implementing agency and procedures, and methods and procedures for participation of private developers, etc. 5. Evaluation of the Redevelopment Policy for Squatter Areas 1) Evaluation of Policy Objectives The objectives of current policy emphasize recovering the urban functions and aesthetic elements of the city by means of the physical removal and redevelopment of squatter rather than by improving the social welfare of squatter families. Although this ill-conceived and misguided policy has contributed to improving the city's aesthetics considerably, it has brought heavy financial burdens to squatter families, destroyed community integration, downgraded living environments through relocation activities, and consequently engendered sprawls of squatter dwellings on peripheral areas of the city. It is, therefore, difficult to justify the policy objectives of the current program. 2) Evaluation of methodology <Redevelopment> The redevelopment program, involving primarily demolition and renewal in the project areas, is found to have some merit in its renewal of densely developed squatter areas. Furthermore the program achieves the physical improvement of squatter life by securing open space, and the improvement of housing standards. However one has to look at the negative side as well which involves aggravation of the housing shortage and the heavy financial burden on the squatter. <Relocation> As an easy physical control measure implemented in those areas not eligible for either rehabilitation or redevelopment, a relocation policy has been utilized. The procedure begins with the notification of relocation within a one year period. If the families receive the notification to move within the required period, they are eligible for both a priority ticket for public housing accommodation and financial assistance in moving. Otherwise, all families in the area will be removed by force. The statistics for relocation, indicate that 55,169 units were removed by the end of 1978, and 48,103 newly formed units were being cleared. Since the relocation measure removed about 90% of the targeted units, it might imply the successful achievement of the measure statistically. However, the Third Illegal Housing Survey done in 1979 indicated that there were 30,000 additional units to be removed. The relocation policy has many difficulties and is unlike redevelopment which provides a better living environment. 6. The Policy Plan for Squatter Areas If one conceives only the physical improvement of squatter areas, the redevelopment approach has offered and would continuously offer great potential for accomplishing the housing policy objectives. The program was designed to clean up squatter settlements in the city core areas and build new residential complexes on them in accordance with a comprehensive plan. No other planning tool would provide the possibility for such radical change. Although the redevelopment program has much merit for reviving the city functionally and improving its aesthetics it is nevertheless, subject to many criticizms. If the city government is to solve the problem of housing shortage, attention must be given to these segments of society that are most desperately in need of housing, and not to those already in possession of homes. Even if the government is concerned more about the quality of the urban environment, workable and reasonable measures designed to improve the status of existing houses would be more effective than wholesale removal and resettlement. Regardless of what appears to be an obviously more realistic approach to housing policy, and regardless of the important functions that squatter settlements provide to needy residents, the government continues to treat squatters and squatter and squatter settlement both unwisely and unfairly. Squatter areas are regarded as an embarrassment and as the breeding ground for intense political instability. In this regard, John Turner has written: "The reasons for the failure of conventional housing programs, or of any program for the replacement of substandard dwellings, lie in the discrepancies between people's needs and the standards for housing set by the institutions. The immense variability of individual households' needs and the inelasticity of low-income people's housing demands, creates a difficult situation for governments.' The present policy lacks an appreciation for the positive functions that squatter settlements provide, and it endangers the fragile network of physical and social relationships that make it possible for the low-income squatter to survive and pursue a meaningful life in the city. It would be both more sensible and more humane to permit existing levels of squatter settlements to remain and allow the inhabitants to better their lives, than risk the potential negative effects and high costs, both social and individual, inherent in relocation. Much of the discussion has thus far focused on the government's failure to understand the real needs of low income, squatter families with respect to housing. Numerous attempts has been made to alleviate housing conditions of squatter families and yet many have resulted in worsening the situation. It is this paper's recommendation that most squatter settlements in Seoul should be immediately legalized, rehabilitated, and selectively redeveloped. Although squatters comprise the lowest socio-economic group of the urban population, it has been shown that they have a very high level of developmental motivation and aspiration. In no sense are these families down-and-out slum dwellers. They are hard-working, ambitious, and achievement-oriented working class households, who, if given the opportunity, can and will contribute greatly to the overall betterment of the city. As possible mitigation measures, some policy alternatives are proposed in this chapter. These measures deal with the clarification of definition, criteria reformulation, compiling of explicit date, implementation of modified redevelopment, relocation, and financial resources. -clarification of definition -reformulation of criteria -compiling explicit data -implementation of modified redevelopment -relocation -financial resources

朝鮮朝 末期의 近代化에 있어서 敎育과 내셔널리즘에 관한 硏究 : 그 成立過程과 役割構造를 중심으로

李俊球 弘益大學校 敎育硏究所 1986 敎育硏究論叢 Vol.- No.2

In this article, the writer has closely observed how our education and nationalism were established and developed, and what role they played for the modernization of the nation during the later period of the Yi Dynasty, especially between the years of 1860 and 1910. He conducted the historical study: A. In terms of the subject, he observed 1) the modernization 2) the nationalism 3) the education. B. In terms of the point of view, he observed 1) the interaction of modernization and nationalism 2) the interaction of nationalism and education 3) the interaction of education and modernization reaching a conclusion that the three conceptions are closely related, eventually leading to conception of trinity. C. In terms of the contents, he found that Historically, nationalism and modernization are closely related. In Korea, its modernization and nationalism were developed in such inseperable relationship. It is particularly noteworthy that desire for modernization and "people's sovereignty conception" greatly prevailed among the Koreans at that time. The latter is actually nationalism itself. In this context, modernization and nationalism interacted strongly and closely, accelerating the development of modern education.

韓國近代의 思想과 敎育 : 民族意識의 屈折과展開 Refraction and Development of National Consciousness

李俊球 弘益大學校 敎育硏究所 1989 敎育硏究論叢 Vol.- No.5

This paper is to examine how the national consciousness of Korea was formed in modern times, when the country went through many changes in thought and education. 1. The national consciousness in modern Korea was formed when domestic and foreign developments enabled the people to see their realities, engaged them in campaigns against foreign invasions and against feudalism, and caused changes in education. 2. This paper discusses how those campaigns happened in that period, what influences the campaigns had on education of the period, and what course the education of the period took in its modernization. 3. As modern Korea could not put an end to the feudal system and stepped on the new historical stage, the country directed its effort exclusively to keeping it independent ant to restoring its full sovereignty while it was struggling against. feudalism and agaist invasion. 4. The course was full of complications, and the situation continued until the Samil Independence Movement of 1919 from 1860's. 5. During that period bringing up leaders was the most important task imposed upon education. In conclusion, education in the latter part of the 19th century was burdened with two tasks at a time: inspiring the people with the national consciousness, and coping with various influences from abroad.

韓國近代의 留學과 民族主義 : with Referance to the Refration and Frustration of Their Movement 民族意識의 屈折과 展開

李俊球 弘益大學校 1990 弘大論叢 Vol.22 No.1

The Korean education as the leading factor of historical innovation and consciousness formation during the later 19th century was expected to to play a double role: encouragement of national consciousness and counter power to the rapid international surge. In the context of the contemporary national danger, the Korean students' national consciousness was relatively strong. However, it is noteworthy that their consciousness was gradually refracted and became eventually subject to the change of direction influenced by the outside world trend. Their change of direction is well illustrated by the fact that instead of pursuing their national consciousness movement, they turned toward the movement of independance and national salvation.