• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.4
• /
• pp.400-406
• /
• 2017

The model used in this study was reversed to analyze the cause of excessive damage that occurred inside the rotating system and pipe system of a centrifugal-type seawater pump on a ship. For this purpose, internal flow analysis on a cooling seawater pump was performed using CFD. As a result, the shape and boundary conditions of the target pump were set by reverse engineering, and pump efficiency at a design operating point of $125m^3/h$ was calculated as 85.3 % with a head of 32.0 m. The maximum efficiency point of the target pump was estimated to be 86.2 % at $150m^3/h$, but this differed from the actual operating point. At $112.5m^3/h$, which was the lowest flow point, flow was unstable due to the characteristics of the low flow point and analysis convergence was not good. The purpose of this study was to clarify the cause of ongoing cavitation in seawater pumps and piping systems in operation. Future research will be needed to clarify causes for pipe systems in the future by performing calculations for the total piping system of an inlet and outlet, in addition to measuring the flow rate of each branch pipe.

• Membrane Journal
• /
• v.20 no.2
• /
• pp.120-126
• /
• 2010

In this study, the effect of surface deposition of $TiO_2$ nanoparticles at polyethersulfone (PES) microfiltraiton (MF) membrane on humic acid fouling was investigated. The effect was observed as a function of crystal structures of $TiO_2$ nanoparticles and solution chemistries including pH and divalent cation such as calcium. Our results showed clearly that $TiO_2$-deposited membrane could mitigate membrane fouling significantly. However, this effect was observed to be dependent upon crystal structures of $TiO_2$ nanoparticles and solution chemistries. In the absence of calcium, fouling mitigation was less pronounced for both anatase and hybrid $TiO_2$-deposited membrane than for rutile $TiO_2$-deposited membrane while opposite trend was observed after addition of calcium. In the presence of calcium, the adsorption of humic acid to $TiO_2$-deposited membrane can be reduced by electrostatic repulsions between humic acid and $TiO_2$ surface. Addition of calcium provided further beneficial effect on fouling mitigation particularly at higher pH for the anatase $TiO_2$ deposited membrane, implying that both increased hydrophilicity due to $TiO_2$ nanoparticles and negative surface charge of the membrane should affect fouling mitigation. However, rutile $TiO_2$ having more inertness generally than the anatase $TiO_2$ showed relatively robust effect on the fouling mitigation regardless of solution properties.

• The Journal of Engineering Geology
• /
• v.29 no.2
• /
• pp.123-136
• /
• 2019

This study examines the effect of collector well installed to reduce groundwater level in the regions with the occurrence of landcreep, a soil mass movement triggered by instability on slopes. Slopes are prone to failure as a result of instability caused by its internal, topographic and geological properties as well as due to external factors such as rainfall and earthquake. In Korea during the rain season, rainfall infiltration affects the groundwater level in soil, building up porewater pressure and load, and finally drives slopes to collapse. Slope failure caused by rainfall infiltration has been leading to a drastic forest degradation. The studied slope is located adjacent to a valley, its terrain corresponds to piedmont gentle slope, while the upper part of the failure surface is steep. After reinforcing the terrain where landcreep had occurred and installing collector well on the slope, we measured the changes in the groundwater level. In order to analyze the relationship between the well and the slope, we calculated the ratio of groundwater level to rainfall before and after the installation of the collector well. As a result, it is confirmed that the ratio increases after the installation of the well, which in turn reduces the groundwater level. Analysis of the change in groundwater level after 3, 7, 15 days antecedent rainfall showed that the higher the overall groundwater level, the less the value ($r_p$) of groundwater level-rainfall ratio is, while the value becomes relatively greater when the groundwater level is low. In particular, if a slope has a large catchment basin as is in the case of the studied site, antecedent rainfall affects groundwater level in the order of 3 < 7 < 15 days.

• The Southeast Asian review
• /
• v.24 no.2
• /
• pp.167-206
• /
• 2014

메콩 경제권(GMS)의 다양한 개발 현장 속에서 고무 나무로부터 채취하는 라텍스는 캄보디아, 라오스를 포함한 인도 차이나 반도 국가들 사이에서 주요 농업 활동으로 주목 받고 있다. 그러나 캄보디아와 라오스의 대형 플랜테이션은 여러 부정적인 결과들을 낳고 있다. 토지 점유, 계약 농업을 통한 착취 등으로 인해 역설적으로 농촌의 빈곤은 증가하고 있고 해외 투자자에 대한 재정적, 기술적 의존이 심화되고 환경 파괴가 일어나고 있다. 이러한 점들로 인해 소규모 자작농들에 주목할 필요가 있다. 고무 자작농은 고용을 창출하며 토지 점유를 방지한다. 본 연구는 캄보디아와 라오스의 소규모 고무 자작농들의 생계를 비교하며 고무 호황으로 어떠한 이득을 얻고 어떠한 형태로 생계를 개선할 수 있는지를 연구한다. 본 연구는 캄보디아의 Tboung Khmum 구역과 Somsanouk 마을의 사례 연구를 바탕으로 하였다. 실증적인 분석은 세 가지의 이론적 틀을 바탕으로 하였다. 미시-생계 연구, 글로벌 가치사슬 그리고 GMS에 대한 연구들이다. 실증 분석의 초점은 생계의 변화상과 결과(고용 창출과 빈곤 탈출)이다. 전체적으로 소규모 고무 자작농은 전망이 밝았으나 앞서 언급 된 문제점들로 인해 농촌 문제를 모두 해결할 수 있는 수단은 아니다. 중요한 유사성은 소규모 고무 자작농의 사회경제적 공헌이다. 연구 지역 두 곳에서 자작농들은 고무 농사는 생계를 개선하는 데에 좋은 수단이라고 답하였다. 그럼에도 불구하고 낮은 교육 수준은 그들의 생계 전략을 불안정하게 하고 있다. 양쪽 지역에서 응답자들은 다른 주민을 따라 고무 농사를 시작했다고 대답했으며 경제, 환경적인 위험에 대해 충분히 인지하고 있지 못하였다. 이와 관련한 다른 유사점으로 소규모 자작농들을 지원할 수 있는 정부의 개입이 없었다는 것이다. 자금 조달은 고무 농사의 심각한 애로 사항 중 하나였다. 명확한 차이점으로 Tboung Khmum의 자작농들은 중개 상인에게 계약 관계를 맺지 않고 라텍스를 판매했으며 Somsanouk의 경우에는 고무 가격이 국제 시장의 영향을 받음에도 가장 높은 가격을 제시하는 상인에게 농민 전체가 같이 판매를 하였다. 이러한 현상은 GMS 내에서 이루어지고 있는 근대적인 경제 현상 에 농촌 공동체들이 다양하게 연결 되고 있음을 재확인한다. 게다가 Somsanouk 마을에서는 사이짓기를 하는 경우가 없었다. 이는 투자자들이 생산량을 극대화하기 위해 자작농들에게 사이짓기를 장려하지 않았기 때문이다. Tboung Khmum 마을의 경우 고무와 더불어 고무 이전의 주요 작물이던 카사바를 같이 재배했다. 요약하면, 자작농에 의한 소규모 고무농업은 (비록 농촌의 모든 어려움을 해결할 수는 없지만) 토지점유 등 부정적 현상이 나타나는 대규모 플렌테이션에 비해 유의미한 일자리를 창출하는 등 미래를 위한 보다 나은 대안이 될 수 있다. 농촌 생활의 질을 개선하기 위해서는 7년 간의 고무 생육기간 동안 농가가 감수해야 하는 사회-경제적 불안정성을 해결하고 대안적 소득원을 마련할 필요가 있다

• Therapeutic Science for Rehabilitation
• /
• v.10 no.1
• /
• pp.63-75
• /
• 2021

Objective : The purpose of this study was to examine the roles and practices of occupational therapists in public health centers based on their working experience of occupational therapists who are working in these facilities. Methods : We used Giorgi's descriptive phenomenological research method. Six occupational therapists were interviewed, and their recorded data were analyzed using Claizzi's thematic analysis. Results : As a result, 4 categories, 16 themes, and 24 elements were elicited. The major roles of occupational therapists in public health centers were the evaluation of clients, home-visit occupational therapy, management of dementia programs and community connection projects. Interventions that are needed to create a healthy community include case and program management, compensatory approaches, and healthy lifestyle interventions. The difficulties experienced by occupational therapists include their limited number job insecurity, performance-oriented administrative policy, and the lack of communication among professionals. Occupational therapists require education in health management and practice in public health centers to build their capacities. Conclusion : The results of this study could be used for guidelines for occupational therapists who work in community healthcare centers, as well as basic training for competent occupational therapists in the community.

• The Journal of Korean Academy of Sensory Integration
• /
• v.20 no.2
• /
• pp.46-55
• /
• 2022

Objective : This study aimed to explore the meaning of work experience of school-based occupatioanl therapists. Methods : This study was a phenomenological study. The participants were 7 school-based occupational therapists, all of whom were female with working experience of 5 years. One-on-One interviews were conducted with them about their work experience as school-based occupational therapists, and additional interview details were confirmed by e-mail. The interviews were recorded with the consent of the subjects. The researcher listened to the recordings several times prior to transcribing and analyzed the interviews according to Colaizzi's research method. Results : A total of 2 themes and 10 sub-themes were derived. Challenges and hopes were drawn as themes. The challenges theme included sub-themes administrative work burden, restriction of physical environment, lack of awareness of teachers, unstable employment, and legal restrictions. There were sub-themes such as sense of mission for children, team members with the same goal, children who want school-based occupational therapy, teacher' satisfaction, and responsibility for the development of school-based occupational therapy. Conclusion : Institutional improvement and policy support for school-based occupational therapy should be prepared to provide qualitatively improved school-based occupational therapy for special education subjects.

• Progress in Superconductivity and Cryogenics
• /
• v.25 no.2
• /
• pp.10-13
• /
• 2023

High-T_C superconductivity (HTSC) has been the central issue in the field of condensed matter physics for decades. An essential part of the research on superconductivity is finding new exotic superconductors. It was recently suggested that Ir-substituted La_0.7Sr_0.3MnO₃ (LSMIO) is a new high-T_C superconductor. However, systematic studies to experimentally verify the superconductivity have not been done. Here, we report the growth processes of LSMIO thin films and their electrical transport properties. We observed a clear negative correlation between the intensity of the laser utilized for film deposition and the Curie temperature of the deposited film. We attributed this effect to the suppression of Sr concentration in the LSMIO films as the laser intensity increased. However, our LSMIO films show conventional ferromagnetism instead of HTSC. To realize the HTSC in LSMIO systems, further exploration of diverse compositions of LSMIO compounds is essential.

• Korean Journal of Microbiology
• /
• v.34 no.3
• /
• pp.120-125
• /
• 1998

A plasmid pNPG contains a genomic DNA complementing npgA1 which is located on the left arm of linkage group I. It transformed Aspergillus nidulans at a high frequency. No abortive transformants were observed and the $Trp^+$ transformants were all $Npg^+$. The 10.4 kb Psti fragment of the genomic DNA was subcloned into pILJ16, which increased the transformation efficiency by more than 200-folds. The transformants were mitotically unstable and yielded $Arg^-$ conidia at the frequency of more than 80%. An additional gene cloned into the plasmid containing the fragment was always lost with $argB^+$ marker. These characteristics strongly indicate the possibility that the plasmids autonomously replicate. The full activity of enhanced transformation was retained on the 4.9 kb EcoRI-HaeIII fragment. The DNA segment was similar to AMA1 rather than ANS1 in function and designated AMA2.

• Microbiology and Biotechnology Letters
• /
• v.6 no.1
• /
• pp.41-46
• /
• 1978

Piscicidal substance produced by Streptomyces sp. isolated from soil was toxic against various kinds of fish. After extraction with CH$Cl_3$ from the culture medium, the substance was purified by avicel column chromatography. In order to test toxicity, various kinds of fish were subjected to the acqueous solution of 100 us of the substance per liter of water. Generally, the substance was toxic to most fish, but Macropodus chinenes and Misgurnus mizolepis are resistant to the substance than Gobius similis and Pseudorasbora parva. The substance was stable at pH range, 3.0 to 7.0, but labile at alkaline pH, and to heat as well. Succinic dehydrogenase on most of tissue cell of Cyprinus carpio was inhibited by this substance strongly, but spinal cord was not inhibited. By addition of Cu and Pb salts to the culture medium, piscicidal substance producibility was activated.

• Journal of Korean Society of Steel Construction
• /
• v.24 no.3
• /
• pp.337-348
• /
• 2012

This study investigated the characteristics of bifurcation and the instability due to the initial imperfection of the space truss, which is sensitive to the initial conditions, and the calculated buckling load by the analysis of Eigen-values and the determinant of tangential stiffness. A two-free nodes model, a star dome, and a three-ring dome model were selected as case studies in order to examine the unstable phenomenon due to the sensitivity to Eigen mode, and the influence of the rise-span ratio and the load parameter on the buckling load were analyzed. The sensitivity to the imperfection of the two-free nodes model changed the critical path after reaching the limit point through the bifurcation mode, and the buckling load level was reduced by the increase in the amount of imperfection. The two sensitive buckling patterns for the model can be explained by investigating the displaced position of the free node, and the asymmetric Eigen mode was a major influence on the unstable behavior due to the initial imperfection. The sensitive mode was similar to the in-extensional mechanism basis of the simplified model. Since the rise-span ratio was higher, the effect of local buckling is more prominent than the global buckling in the star dome, and bifurcation on the equilibrium path occurring as the value of the load parameter was higher. Additionally, the buckling load levels of the star dome and the three-ring model were about 50-70% and 80-90% of the limit point, respectively.