• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.18-18
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• 2007

지난 수년 동안 Sn-3.0Ag-0.5Cu 합금은 전자산업의 표준 무연솔더 조성으로 전자제품의 제작에 사용되어져 왔으며, 그 신뢰성도 충분히 검증되어 대표적인 무연 솔더 조성으로의 입지를 굳혀왔다. 그러나 전자제품의 mobile화에 따른 내충격 신뢰성에 대한 요구와 최근의 급격한 Ag 가격의 상승은 Ag 함량의 축소에 의한 원가절감을 요청하게 되었으며, 이에 따라 소량의 Ag를 함유하는 솔더 조성 개발에 대한 연구가 산업 현장을 중심으로 절실히 요청되고 있다. Sn-Ag-Cu의 3원계 함긍에서 Ag는 합금의 융점을 낮추고, 강도와 같은 합금의 기계적 특성을 증가시키는 한편, 모재에 대한 합금의 젖음성을 향상시키는데 필수적인 원소로 인식되고 있다. 따라서 Sn-Ag-Cu의 3원계 함금에서 Ag의 함량을 감소시키게 되면, 합금액 액상선 온도와 고상선 온도가 벌어져 pasty range(또는 mush zone)가 증가하게 되고, wettability도 감소하게 되어 솔더 합금으로서의 요구 특성을 많이 상실하게 된다. 또한 Ag 함량을 감소시키게 되면 합금의 elongation이 향상되면서 내 impact 수명이 향상되는 효과를 볼 수 있으나, 합금의 creep 특성 및 기계적인 강도는 감소하면서 열싸이클링 수명은 감소하는 경향을 나타내게 된다. 따라서 솔더 합금의 내 impact 수명과 열싸이클링 수명을 동시에 만족시키지 위해서는 Ag 함량을 최적화하기 위한 고려가 필요하며, 합금원소에 대한 연구가 요청된다고 하겠다. 한편 Ag의 함량을 3wt.% 이상으로 첨가할 경우에도 비교적 느린 응고 속도에서는 조대한 판상의 $Ag_3Sn$ 상을 형성하는 경향이 있어 외관 물량을 야기 시킬 가능성이 매우 커지는 현상도 보고되고 있다. 따라서 Ag의 첨가량을 최적화 하면서 솔더 재료로서의 특성을 계속적으로 유지하기 위해서는 제 4 원소의 함유가 필수적이라고 할 수 있다. 본 연구에서는 Sn-Ag-Cu계에 첨부하는 제 4원소로서 In을 선택하였다. 비록 In은 Ag보다 고가이기 때문에 산업적인 적용을 위한 솔더 합금 원소로는 거의 각광받지 못했으나, 본 연구의 결과로는 In은 매우 소량 첨가할 경우에도 Sn-Ag-Cu계 합금, 특히 소량의 Ag를 함유하는 Sn-Ag-Cu계 합금의 wettabilty와 기계적 특성 향상에 매우 효과적임을 알 수 있었다. 결론적으로 본 연구를 통해 구현된 Sn-Ag-Cu-In계 최적 솔더 조성의 경우 Sn-3.0Ag-0.5Cu의 표준 조성에 비하여 약 18%의 원자재 가격 절감을 도모할 수 있을 것으로 예상되는 한편. Sn-3.0Ag-0.5Cu에 유사하거나 우수한 wettability 특성을 나타내었고. Sn-1.0Ag-0.5Cu 또는 Sn-l.2Ag-0.5Cu-0.05Ni 조성보다는 월등히 우수한 wettability 특성을 나타내었다. 더구나 Sn-Ag-Cu-In계 최적 솔더 조성은 합금의 강도 저하는 최소화 시키면서 합금의 elongation은 극적으로 향상시켜 합금의 toughness 값이 매우 우수한 특성을 가짐을 알 수 있었다. 이렇게 우수한 toughness 값은 솔더 조인트의 대표적 신뢰성 요구 특성인 열싸이클링 수명과 내 impact 수명을 동시에 향상시킬 수 있을 것으로 예상된다. 요컨대 본 연구를 통해 구현된 Sn-Ag-Cu-In계 솔더 조성은 최적 솔더 조성에서 요구되는 4가지 인자, 즉, 저렴한 원재료 가격, 우수한 wettability 특성, 합금 자체의 높은 toughness, 안정하고 낮은 성장 속도의 계면 반응층 생성을 모두 만족시키는 특징을 가짐으로서 기존 무연솔더 조성의 새로운 대안으로 자리 잡을 것으로 기대된다.

• Korean Journal of Family Social Work
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• no.43
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• pp.87-110
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• 2014

This study is to understand the psychosocial experience in 'Cheonan Warship Incident Survivors'. The study question was how psychosocial experience in The Union of Family Bereaved by Cheonan Warship had been progressed. To answer this question 4 representers ofthe group and 2 reporters had been interviewed using a qualitative research method based on Phenomenology method. From this study the group's experience in had been revealed that they first crisis intervention are to identify and reinforce the strengths and coping skills of a one's family. Second, they gathered their opinion together and assigned the roles to the members, and then, requested what they want responding reasonably. The families' love, the representers' quick judgements and decisions, and the embarrassment of the military and media for the dead, who had been abandoned for long and decayed under the cold ocean, made the national support and respectful treatment possible for the dead and the family. The results of study will be applicable for individuals and groups, who need social work service as an empowerment intervention approach and crisis intervention are to identify and reinforce the strengths and coping skills of a one's family. The social worker's ability to anticipate, understand, and give therapeutic direction to the crisis reaction and the concerns of family members helps to bring around a successful crisis resolution. It is clear to us that wars, suicides, homicides in school settings, disaster and other events are providing unique challenges to social workers who are interested in learning more about the effects such events have on victims of traumatic events.

• 한국노년학
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• v.31 no.4
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• pp.939-967
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• 2011

This study observed elderly women's adaptation process on separation by death in rural areas through grounded theory approach and developed its entity theory. Participants for this study were 14 elderly women who have lost their husbands in the last 12 months. The study was conducted for 8 months starting January 2010. Each interview per session took 40 to 90 minutes, study notes were taken on site, and recorded contents were transcribed by the researcher which was myself. The research data were collected by in-depth interview and with help of local community's nurses who were in charge of taking care of the participants. The collected data were analyzed by applying Strauss & Corbin's grounded theory (1998). As a result of study, 80 concepts, 28 subcategories, and 12 categories were deducted during open coding process. Adaptation process on separation by death was process of 'finding a way to live alone' which used strategy of 'attempting a make changes in life', and 'embracing the situation' which were influenced by conciliatory conditions of 'degree on economic condition', 'change in health', and 'supporting system' which focuses on phenomenon of 'bearing life alone' which is influenced by context condition of 'marital chemistry of couples during lifetime', and 'the couple's leadership during lifetime' together with casual conditions of 'the fall of wall'. The adaptation process accordance to time flow were divided into 4 steps which were step of 'shock and release of emotions', step of 'longing and resentment', step of 'resignation and acceptance', and step of 'life's restructure'. Above results suggest right directions for welfare for the aged and process of 'finding a way to live alone' for participants by controlling several factors and using intervention strategy, and provided basic data required for developing and applying practical welfare mediation.

• Korean Journal of Microbiology
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• v.47 no.1
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• pp.92-96
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• 2011

Rhodococcus sp. strain DK17 possesses three megaplasmids (380 kb pDK1, 330 kb pDK2, and 750 kb pDK3). The alkylbenzene-degrading genes (akbABCDEF) are present on pDK2 while the phthalate operons which are duplicated are present on both pDK2 (ophA'B'C'R') and pDK3 (ophABCR). DK17 with an optimal temperature of $30^{\circ}C$ showed no growth at $37^{\circ}C$. When transferred to $30^{\circ}C$, however, the $37^{\circ}C$ culture began to grow immediately, indicating that $37^{\circ}C$ is not lethal but stressful for DK17 growth. In addition, when exposed to $37^{\circ}C$ even for a short time, a part of DK17 cells lost the ability to degrade o-xylene (a model compound of alkylbenzenes). When two hundred colonies were randomly selected for colony PCR for pDK2-specific akbC, ophC', or pDK3-specific ophC, a total of 29 colonies were found to have lost at least one of the three genes. PFGE analysis clearly showed that all the mutants have different megaplasmid profiles from that of DK17 wild type, which are divided into five different cases: Type I (10 mutants, pDK2 loss and acquisition of a new ~700 kb plasmid), Type II (9 mutants, pDK2 loss), Type III (8 mutants, pDK3 loss and acquisition of a new ~400 kb plasmid), Type IV (1 mutant, pDK3 loss), and Type V (1 mutant, pDK2 and pDK3 loss and acquisition of the ~400 kb and ~700 kb plasmids). The above results showing that growth temperature changes can induce physical changes in bacterial genomes suggest that environmental changes in habitats including temperature fluctuations affect significantly the evolution of bacteria.

• Proceedings of the Ginseng society Conference
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• 1988.08a
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• pp.92-98
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• 1988

The present study was performed to find the effects of ginseng and its saponins. which is written in Chung Yao Ta Tsu Tien as anti-amnesia in its chief indication. on experimental amnesia in mice. In the step through test. ginsenoside $Rb_1\;(GRb_1)\;and\;GRg_1$ facilitated the registration of memory and antagonized the electroconvulsive shock (ECS)-induced inhibition of the retention of memory. Moreover. $GRg_1$ antagonized the EtOH-induced inhibition of the retrieval of memory. In the step down test. $GRb_1\;GRb_2\;and\;GRg_1$ antagonized the ECS-induced inhibition of the retention of memory. Moreover. $GRg_1$ antagonized the EtOH-induced inhibition of the retrieval of memory and facilitated the acquisition of short term memory. In the shuttle hox and lever press tests. they have no effects on acquisition and retrieval of memory. except $GRb_1\;GRb_1$ depressed the retrieval of conditioned avoidance response in the shuttle box test. After the end of four tests. the effects of these orally administered drugs on sedative. analgesic. antipyretic and anticonvulsant actions. and on spontaneous and exploratory movements were tested in doses of less than 500mg/kg. but they had none of these effects. Present study may indicate that $GRg_1$ had effects on the retrieval of memory and on the acquisition process of learning response. The recent research on the role of NGF for the survival. regeneration and regulation of brain in adult animals. indicated the importance of NGF on dementia and amnesia. During our research on the specificity of the neurite out growth induced by NGF. we found that the effect of NGF was potentiated by $GRb_1$ in organ cultures of chick embryonic dorsal root ganglia. Then. the effect of $GRb_1$ on neuronal cell survivalin cell culture system was studied. $GRb_1$ potentiated the NGF-mediated increase of neurofilaments in cell cultures of chick embryonic sensory and sympathetic neurons. NGF with $GRb_1$ also showed a tendency to increase the number of surviving neurons of rat embryonic cerebral cortex. NGF increased choline acetyl transferase activity in cell cultures of rat embryonic septum area neurons. but $GRb_1$ did not potentiate NGF activity in cell cultures of rat embryonic septum area neurons. Present study may indicate that $GRb_1$ plays an important role for the survival or regeneration of neurons in the brain.

• Korean Journal of Microbiology
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• v.54 no.1
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• pp.9-17
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• 2018

To investigate the role of bkdR, sigL, yplP, and des genes which were known to be involved in fatty acid synthesis and sensitive at low temperature, deletion mutants of Bacillus subtilis CU1065 and JH642 were constructed. To determine the low temperature sensitivity of these genes, we compared the growth curves of cells at $37^{\circ}C$ and $15^{\circ}C$. At $37^{\circ}C$, wild type and deletion mutants showed almost similar growth but only bkdR deletion strain at $15^{\circ}C$ showed very slow growing compared with wild type. At $15^{\circ}C$ sigL and yplP deletions were somewhat slower or similar to those of wild type strain. Double and triple mutants for bkdR, sigL, yplP deletions were constructed and grown at $20^{\circ}C$ in LB agar to investigate cold sensitive growth. Double or triple deletions including bkdR deletion showed cold sensitive growing. In order to identify more clearly cold sensitive growth, the experiments were carried out under cold shock conditions in which the temperature was lowered from $37^{\circ}C$ to $15^{\circ}C$ at the point of 0.4 optical densities at 600 nm. In these cold shock experiments, only bkdR deletion showed significantly lower growing and additional des deletion increases cold sensitivity. The bkdR activates the bkd operon, which catabolized isoleucine, valine and leucine, amino acids and produce precursors for the synthesis of branched fatty acids. At cold shock growing of bkdR deletion strain, isoleucine recovered cold sensitivity of bkdR deletion but valine did not restore cold sensitivity. Isoleucine is used as a precursor for the synthesis of anteiso-branched fatty acids. On the other hand, valine is used as a precursor for the synthesis of iso-branched fatty acids. This indicates that anteiso-branched fatty acid plays an important role at the cold shock condition.

• Korean Journal of Agricultural Science
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• v.33 no.1
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• pp.35-41
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• 2006

This study was conducted to investigate the developmental ability of interspecies cloned embryos after nuclear transfer of goat fetal fibroblast cells into porcien oocytes. Recipient porcine and goat oocytes were obtained from slaughterhouse and matured in vitro according to established protocols. Enucleation was accomplished by aspirating the first polar body and cytoplasm and a single donor cell was individually microinjected into vitelline space of the enucleated oocyte. The reconstructed oocytes were electrically fused with 0.3M mannitol fusion medium. After electro-fusion, interspecies reconstituted embryos were cultured in PZM-3 for 7 days. In porcine interspecies nuclear transfer with goat fetal fibroblast cells, the cleavage rate of reconstituted embryos were 58.9% which was no significant different from that in porcine nuclear transfer embryos (67.4%). However, the developmental rate into blastocyst stage was 5.4% in interspecies nuclear transfer which was significantly lower than that in porcine intraspecies nuclear transfer (13.6%). When the developmental ability of porcine interspecies nuclear transfer with goat cells was compared with goat intraspecies nuclear transfer, the cleavage rate of embryos were 59.2% and the developmental rate into morular and blastocyst stage was 13.6% in interspecies nuclear transfer which were significantly lower than those in intraspecies nuclear transfer embryos. This result indicated that porcine interspecies nuclear transfer with goat fetal fibroblast cells showed the developmental potential in vitro with lower cleavage and developmental rate compared with intraspecies nuclear transfer.