• Journal of the Microelectronics and Packaging Society
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• v.16 no.2
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• pp.43-50
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• 2009

Although thin PCBs(Printed Circuit Boards) have recently been required for high density interconnection, high electrical performance, and low manufacturing cost, the utilization of thin PCBs is severely limited by warpage and reliability issues. Warpage of the thin PCB leads to failure in solder-joints and chip. The $B^2it$(Buried Bump Interconnection Technology) for PCB has been developed to achieve a competitive manufacturing price. In this study, chip temperature, package warpage, chip stress and solder-joints stress characteristics of the PCB prepared with $B^2it$ process have been calculated using thermo-mechanical coupled analysis by the FEM(Finite Element Method). FEM computation was carried out with the variations in bump shapes and kinds of materials under 1.5W power of chip and constant convection heat transfer. The results show that chip temperature distribution reached more quickly steady-state status with PCB prepared with $B^2it$ process than PCB prepared with conventional via interconnection structure. Although $B^2it$ structures are effective on low package warpage and chip stress, with high strength bump materials arc disadvantage for low stress of solder-joints. Therefore, it is recommended that optimized bump shapes and materials in PCB design should be considered in terms of reliability characteristics in the packaging level.

• Journal of Internet of Things and Convergence
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• v.8 no.6
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• pp.65-73
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• 2022

This study identified the level of awareness of dangerous accidents by empirically analyzing the possibility of hazardous accidents at work and the possibility of dangerous accidents due to COVID-19 targeting the participating seniors who are active in the Senior Club, an organization dedicated to job placement for the elderly. The purpose of this study is to provide basic data for preparing measures to improve risk accidents that may occur in organizations in charge of job placement for the elderly and to suggest countermeasures to prevent dangerous accidents. For this purpose, data were collected from the elderly participating in 16 senior clubs in Busan, and 425 of the collected 430 were ultimately used. As a result of this study, first, it was found that the elderly who participated in a job-dedicated institution for the elderly generally perceived the possibility of occupational risk accidents and risk factors due to COVID-19 to be low. Second, it was found that there was a statistically significant difference in the probability of occurrence of hazardous accidents at work according to demographic characteristics during the participation period, and the probability of occurrence of dangerous accidents with COVID-19 was found to have statistically significant differences in the classification and age of the participating elderly. Based on the results of this study, the project manager suggested creating a safety accident management record sheet, preparing a risk management manual, and establishing a risk management system reflecting the individual characteristics of the participants.

• Journal of Bio-Environment Control
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• v.25 no.3
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• pp.218-223
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• 2016

The calculation method of ground heat exchange in greenhouses has different ideas in each design standard, so there is a big difference in each method according to the size of greenhouses, it is necessary to establish a more accurate method that can be applied to the domestic. In order to provide basic data for the formulation of the calculation method of greenhouse heating load, we measured the soil temperature distribution and the soil heat flux in three plastic greenhouses of different size and location during the heating period. And then the calculation methods of ground heat exchange in greenhouses were reviewed. The soil temperature distributions measured in the heating greenhouse were compared with the indoor air temperature, the results showed that soil temperatures were higher than room temperature in the central part of greenhouse, and soil temperatures were lower than room temperature in the side edge of greenhouse. Therefore, it is determined that the ground heat gain in the central part of greenhouse and the perimeter heat loss in the side edge of greenhouse are occurred, there is a difference depending on the size of greenhouse. Introducing the concept of heat loss through the perimeter of building and modified to reflect the size of greenhouse, the calculation method of ground heat exchange in greenhouses is considered appropriate. It was confirmed that the floor heat loss measured by using soil heat flux sensors increased linearly in proportion to the temperature difference between indoor and outdoor. We derived the reference temperature difference which change the direction of ground heat flow and the perimeter heat loss factor from the measured heat flux results. In the heating design of domestic greenhouses, reference temperature differences are proposed to apply $12.5{\sim}15^{\circ}C$ in small greenhouses and around $10^{\circ}C$ in large greenhouses. Perimeter heat loss factors are proposed to apply $2.5{\sim}5.0W{\cdot}m^{-1}{\cdot}K^{-1}$ in small greenhouses and $7.5{\sim}10W{\cdot}m^{-1}{\cdot}K^{-1}$ in large greenhouses as design standard data.

• Korean Journal of Environment and Ecology
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• v.30 no.1
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• pp.104-109
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• 2016

In Korea, the government has invested the installation of artificial reefs (ARs) which deploying to enhance the restoration of marine environment and productivity on the coastal area at the part of 222,627ha, from 1971 to 2014 for 44 years. The number of ARs are gradually increasing, while their comparison and corelation analysis were not much studied. Therefore, this study is to analyse temporal variation of ARs which composed of concrete named the Horn triangle reefs were deployed at Pohang, Jangkil-ri, a depth of 5 to 7m, in 2003, was monitored 4 times from 2009 to 2011. In results, the biodiversity investigated that the dominant species was Mollusca Omphalius pfeifferi except in 2009. The different species mainly depend on spatial-temporal variation. In this type of study can be used to the R&D, management and government policy of ARs as well improving marine environment.

• Korean Journal of Construction Engineering and Management
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• v.10 no.4
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• pp.38-49
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• 2009

In public project market, design-build projects have been increased because of market trend change which enables technical competition. In this condition, its importance is also getting important. Generally, life cycle of design-build project consists of planning, preliminary design, procurement, contract, detail design, start of construction, construction, end of construction, and evaluation. From contractor's viewpoint, it has problems such as difficulties in project management and information sharing because of frequent change of charged division. To solve these problems, it is desirable to change from function-based management system to process-based management system. The purpose of this study is to develop management process model for design-build project by progress phases. This study analyzed main conflicts and decision making factors of each stage in design-build projects, then systemized management subjects' responsibilities and management points' change. And also this study defined the key information that is the key point by project characteristics and progress phases. Based on this analysis, this study did business process modeling from planning stage to construction design check stage. At last, we proposed the way to manage business process by design-build project progress.

• Journal of Plant Biotechnology
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• v.33 no.1
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• pp.27-32
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• 2006

To clarify the roles of bromelain in plants, we isolated BL1 gene encoding bromelain from pineapple stem tissues and sequenced. The full length cDNA is 933 bp and encodes a polypeptide of 311 amino acid residues. The cDNA is most similar 94% at the amino acid level to bromelain previously isolated from pineapple (BAA21929). Explants of Lactuca sativa were co-cultivated with Agrobacterium tume-faciences LBA 4404 strains containing nptII and BL1 gene for transformation. Through initial selection of regenerated explants by culturing on a kanamycin and carbenicillin containing MS medium, multiple shoots were obtained after 2 months of culture. For a complementary step of selection, putative transgenic shoots were transferred to 1/2 Ms basal medium supplemented with 100 mg/L kanamycin and 500 mg/L carbenicillin. The selected shoots were obtained T1 generation seeds with emasculation, and tested with PCR analysis using 35S promoter and BL1 specific primers whether BL1 gene was introduced to genome of the plants. These results confirmed that produced the specific PCR bands in the putative transgenic lines. Additionally the Northern blot and endo protease activity showed that transcripts of BL1 gene were detected in transgenic lines. Theses results suggest that BL1 gene be successfully integrated and transcripted in the transgenic lettuce plants.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.43 no.2
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• pp.149-155
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• 2017

This study was carried out to investigate the hair protection effect of fermented black soybean extracts. The morphological characteristics, tensile strength and constitutional changes of the hair were analyzed and compared when the hair was chemically oxidized and then treated with fermented black soybean extract. As a result, treatment of oxidizing agent on virgin hair caused damage on the cuticle layer of the epidermis and decreased in tensile strength of hair from $14.32{\pm}0.83g/cm^2$ to $12.32{\pm}0.79g/cm^2$. FT-IR analysis showed the peaks at 1,077, 1,041, and $801cm^{-1}$ of the hair treated with oxidizing agent were increased compared to peak values of virgin hair, indicating that cystein in hair was decreased which is crucial to disulfide bond between keratin. On the other hand, when the damaged hair is treated with the fermented black soybean extract, cracks in the cuticle layer of the epidermis were filled, tensile strength was restored to $14.27{\pm}0.96g/cm^2$ and the ratio of oxidized cysteine in hair was decreased. These results suggest that the fermented black soybean extract is worthy of further investigation as a protective material for hair damaged by oxidizing agents.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.180-191
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• 2013

The purpose of this research was to find an optimal quarrying for marble by analyzing the applicability and the work efficiency of a chain saw machine newly introduced in the underground Baekwoon mine. From the test results of the physical properties of Baekwoon marble, which affects the efficiency of rock cutting, it was found to have similar physical characteristics as the ones which are now being produced in the other areas in Korea. And especially it shows isotropic property, which can be thought to be advantageous as a dimensional stone. To check the long-term quality of the marble as a stone material, several tests such as corrosion resistance test and abrasion test were carried out. It was found to be vulnerable to acid rain with decrease of weight and seismic wave velocity after applying artificial rain at pH 5.6 for 50 times. The percentage of wear from abrasion test was 22.67%. The working time and cutting speed of the chain saw machine were recorded and analyzed during the test-run at the quarry. The overall work cycle was assorted into 9 unit operations and the operating time per each unit was drawn. The operating times for the two cutting patterns, which could be possibly applicable to the work site, were compared. The results indicated that the pattern B, that the cutting sequence was set to minimize the movement of the machine, showed 6% less working hours than the pattern A, which first cuts the outer boundary. With cutting pattern analysis, the ore body in the Baekwoon mine was 3 dimensionally modeled and a quarrying plan considering the existing conditions of the marble was suggested.

• Journal of Korea Port Economic Association
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• v.30 no.1
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• pp.73-96
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• 2014

Competitiveness of container ports has been traditionally evaluated by capability of individual ports to provide services to customers or their service quality. However, since container ports are connected by container shipping networks to varying degrees, the status of the ports in liner shipping service networks also determines competitiveness of the ports. Sometimes same ports may play different roles in different forms of shipping networks. Shipping network connections that formulate in container ports therefore have more significant impact on their performance than service capabilities they have. This study aims to explore how the shipping and port network has been structured and changed in the past and to examine the network characteristics of ports using Social Network Analysis(SNA). In this SNA study, nodes in the network are the ports-of-call of the liner shipping services and links in the network are connections realized by vessel movements, such that the liner shipping networks determine the port networks. This study, therefore, investigates the liner shipping networks and through its results demonstrates the network characteristics of the ports that are represented by the four centrality indices. This provides port authorities and terminal operating companies with managerial implications to enhance competitiveness from customers' perspectives.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.495-495
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• 2022

충적하천에 댐이 건설되면 하류 하천의 식생환경에 변화를 주게 된다. 이입, 활착 및 성장과정을 거치는 제외지 식생은 하천의 유량이 증가하면 소류력과 세굴로 인해 쓸려 내려가기 때문에, 일반적으로 홍수기를 거치면 식생 활착 및 성장 이전의 사주 모습으로 복귀하게 된다. 그러나 댐의 홍수조절 기능은 홍수기에도 하류 하천에 식생을 정착시킬 만큼 큰 소류력을 발생시키지 않아 결국 식생의 성장에 기여하게 된다. 또한 댐은 상류로부터 공급되었던 세립토를 차단시켜 하류 하천의 하상 표면을 조립화 시키게 되는데, 이는 하상의 고정력을 증대시켜 식생의 안정적인 성장을 돕게 된다. 하천에 식생이 자리잡게 되면 홍수 시 흐름에 대한 저항력의 증가로 수위가 높아질 수 있고 제방에 자리 잡은 식생의 이탈은 제방의 붕괴 위험을 증가시킬 수 있고, 식생 사주의 발달이 지속되면 이동사주에서 정지사주로 변화되어 기존의 충적하천 자체가 사라지게 될 수도 있고, 하류 하천의 수리 및 유사 거동 특성도 변화시켜, 기존과 다른 하천 경관 및 수생태계 출현할 수 있다. 국내에서는 2000년대부터 이러한 하천 제외지 사주의 식생 활착이 가속화되어 왔으며, 특히 내성천, 황강 등 댐이 건설된 낙동강 지류 하천에서 이런 현상이 두드러지게 나타났다. 이에 따라 관련된 많은 조사·연구들이 수행되었으며, 변화 원인으로 홍수조절, 유사공급 변화 및 기후변화가 제시되었다. 그러나 댐이 건설되지 않은 하천(비조절 하천)에 대한 조사와 같은 비교군 지역의 정량적 분석은 상대적으로 부족하여, 정확한 제외지 식생 증가에 대한 원인을 규명하지 못하였다고 판단된다. 이에 비조절 하천이라 판단되는 감천을 대상으로 식생의 변화 양상을 분석하고, 유사 및 기후변화 등과의 관계를 본 연구에서 제시하였다. 감천은 상류에 김천부항댐이 건설되었으나, 댐의 영향범위가 전체 유역면적의 약 6%로 비조절 하천에 가깝고 사주가 발달된 충적하천이므로, 하천 본류에 댐이 건설된 다른 지역과의 비교군으로 적합하다고 판단하였다. 대상 지점은 상, 중, 하류의 사주가 발달된 지역으로 선정하였고, 본 연구에서 개발된 이미지 처리기법을 적용하여 사주 면적을 계산하였다. 분석결과 식생역으로 전환된 모래 사주의 면적은 봄~초여름 강우량과 밀접한 관계가 있는 것으로 파악되었다. 특히 초여름까지 가뭄이 지속될 때, 식생역은 증가하였다. 그러나 식생 활착 이전에 큰 유량 발생 시 식생이 쓸려 내려가고 유사가 그 자리를 대체하여 다시 사주가 발달하는 과정을 보여 주어, 감천의 사주 식생역의 증가 추세는 없는 것으로 파악되었다. 향후 댐이 본류에 건설된 조절 하천과의 비교를 통해 사주의 식생역 증가에 대한 댐 건설의 영향을 파악할 것이다.