Sn-xAg-0.5Cu 무연 솔더 볼의 파단특성 연구

정종설,이용성,신기훈,정성균,장동영 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-

This paper presents a study on the failure characteristics of SnAgCu lead-free solder balls. To estimate the effect of Ag, three types of SnAgCu balls are first prepared by varying the weight percent of Ag (1.0, 3.0, 4.0 wt%) and then analyzed by reliability tests such as thermal shock, high speed ball shear, and drop tests. Thermal shock test reveals that the higher the weight percent of Ag is, the longer the fatigue life becomes. To the contrary, high speed ball-shear test and drop test show that the shear strength and the fracture toughness of solder balls are inversely proportional to the weight percent of Ag, respectively. Reasons for these observations will be further investigated in the future work.

加味牛膝湯이 實驗動物의 鎭痛에 미치는 影響

金炯均,權文鉉,오로사,金成宰,李彦政,李峰根 圓光大學校 韓醫學硏究所 1996 원광한의학 Vol.6 No.1

스크림 프리프레그의 기계적 특성평가

정성균,정성교 서울産業大學校 1999 논문집 Vol.49 No.2

Mechanical characteristics of composite laminates with carbon scrim and glass scrim are evaluated in this paper. Composite laminates in USN125 group are made by inserting carbon scrim and glass scrim between layers. The stiffness properties needed for a plane-stress analysis are modulus(E₁), strength(Xt) in the fiber direction, modulus(E₂), STRENGTH(Yt) transverse to the fiber direction, one of the in-plane Poisson ratios ν12, and desity of composite laminates. These properties are routinely characterized by ASTM standards. Experimental results show that the mechanical properties of UD prepreg the transverse direction were highly improved by inserting scrim.

보드 레벨 플립칩의 4점 굽힘 시험 시 파단 특성 연구

이용성,정종설,이재헌,신기훈,정성균 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-

In general, circuit board assemblies experience various mechanical loadings during assembly and in actual use. The repeated cyclic bending can cause electrical failures due to circuit board cracks, solder interconnects cracks, and the component cracks. In this paper, we report on the failure characteristics of board level flip chips under the repeated cyclic bending. We first describe a new 4-point bending tester, which is developed according to JEDEC standard No.. 22B113. The performance of the tester is then estimated through actual experiments . Test results reveal that the cracks first occur on the outer balls around 20,000 cycles and gradually propagate to the inner balls where cracks are found around 70,000 cycles.

cAMP 농도에 영향을 미치는 수종약물이 파골세포형성에 미치는 영향

소영,고성희,백정화,김관식,정동균 대한구강생물학회 1992 International Journal of Oral Biology Vol.16 No.2

To study the effect of cAMP on the generation of osteoclasts from their precursor cells, the bone marrow cells were isolated from 7 to 9 week-old male mice. The femur and tibia were dissected aseptically and the marrow cavity was flushed with 1 ㎖ of α-minimum essential medium by slow injection. Collected marrow cells were cultured at 1.5-2.0×10^6 cells/well in 24-well plate for 8 days. In experimental group, PGE_2(5×10^-6, 10^-5M), forskolin(10^-5M) or IBMX(10^-4, 10^-5M) were added singly or in combination from the 1st day culture. After cultures, staining for tartrate-resistant acid phosphatase(TRACP)-marker enzyme of osteoclast-was performed according to the modified method of Burstone. The TRACP-positive multinucleated cells(MNC), which have 3 or more nuclei, were counted. The observed results were as follows. 1. In control group. TRACP-positive mononuclear cells were present, but no TRACP-positive multinucleated cells appeared. 2. PGE_2(5×10^-6M) or forskolin(10^-5M) significantly stimulated the formation of TRACP-positive MNC. Moreover, forskolin potentiated the TRACP-positive MNC formation induced by PGE_2 when added simultaneously. 3. IBMX(10^-4, 10^-5M), when added alone, significantly stimulated the formation of TRACP-positive MNC. However, IBMX(10^-5M) added in combination of PGE_2(10^-5M) partially inhibited the TRACP-positive MNC formation induced by PGE_2.

Platelet-Derived Growth Factor가 백서두개관 세포군의 증식 및 교원합성에 미치는 영향

김기수,고성희,백정화,민병무,김관식,정동균 대한구강생물학회 1991 International Journal of Oral Biology Vol.15 No.2

To study the effect of platelet-derived growth factor(PDGF) on the replication and collagen synthesis of rat calvarial cells, five bone cell populations(I-V) were prepared from fetal rat calvaria by sequential enzyme digestion. After primary culture for 6-7 days, each bone cell population was collected and then population Ⅰ and Ⅱ, Ⅳ and Ⅴ were pooled together. And the cells were resuspended at 6-8×10^4 cells/㎝^2 and cultured for 2-3 days. The medium was changed to serum-free medium prior to addition of growth factor. The effect of PDGF on the cell proliferation was measured by the incorporation of [^3H]thymidine into DNA. Protein synthesis was determined by measurement of [^3H]proline incorporation into collagenase-digestible protein(CDP) and noncollagenous protein(NCP) according to the method of Peterkofsky and Die-gelmann(1971). The observed results were as follows. 1. PDGF at 10 ng/㎖ significantly increased the [^3H]thymidine incorporation into DNA in all bone cell populations. 2. PDGF at 30 ng/㎖ significantly increased the synthesis of NCP in population Ⅰ, Ⅱ and Ⅳ, Ⅴ. 3. PDGF had no effect on the synthesis of CDP but percent collagen synthesis was decreased significantly in population Ⅳ, Ⅴ. Taken together, the increase of protein synthesis by PDGF in rat calvarial cells was due to the incraese of NCP synthesis.

연쇄알구균 감염에 의한 급성 인후염 후 반응성 관절염 1예

박은하,도연실,양정채,강미라,서현주,정숙인,손준성,기현균,오원섭,백경란,송재훈 대한감염학회 2004 감염과 화학요법 Vol.36 No.6

연쇄알구균에 의한 급성 인후염 후 발생한 반응성 관절염은 급성 류마티스열의 개정된 진단기준을 충족하지 못하면서, 지속적 혹은 재발성의 비이동성 관절염과 발열, 홍반성 결절, 일시적 간기능 이상 등을 보이면서 심장염과 무도증을 드물게 동반하는 질환이다. 따라서, 발열을 동반한 급성 관절염 환자에서 감별해야 할 질환 중의 하나이며, 심근염 예방을 위한 페니실린 요법의 적응증 및 기간에 대해서는 아직 이론이 많은 상황으로, 보다 광범위한 연구가 필요하다. 저자들은 연쇄알구균에 의한 급성 인후염 1주 후에 발생한 하지의 다발성 비이동성 관절염과 함께 결절홍반 및 일시적 간기능 이상을 보인 환자에서 PSRA로 진단하고 비스테로이드성 항염증제 및 스테로이드로 성공적인 치료를 하였기에 이를 문헌 고찰과 함께 보고하는 바이다. Poststreptococcal reactive arthritis (PSRA) is associated with recent streptococcal infections. However, PSRA is distinct from acute rheumatic fever by its clinical manifestations: non-migrating arthritis, erythema nodosum or erythema multiforme, and transient elevation of serum transaminases. We experienced a 33-year-old man who presented with fever, arthritis of both knees and ankles, and erythema nodosums on extensor surfaces of lower legs which developed 6 days after the onset of pharyngitis symptoms. Blood and urine cultures were negative. Throat culture was negative for group A β-hemolytic streptococcus. The ASO titers increased up to 2080 IU/mL in sequential monitoring. The result of bone scan was compatible to arthritis of both knees and ankles. There were no signs or symptom of carditis. He showed clinical improvement with anti-inflammatory drugs (naproxen 1,000 mg/day and prednisolone 7.5 mg/d). PSRA should be included in the differential diagnosis of patients presenting with arthritis combined with fever.

Terminal Sliding Mode Control System with Minimum Convergence Time for DC Motor Systems

Seong-Kyun Jeong,Bo-Ram Kim,Kang-Bak Park 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

Since the finite time stabilization is very important in many actual applications, finite time control systems have been studied a lot. Terminal sliding mode control system is a robust control scheme which guarantees that the error gets to zero in a finite time. The terminal sliding mode controller uses terminal sliding surface utilizes a power function whose exponent is a rational number 0 to 1. This exponent affects the convergence time. Thus, in this paper, for DC motor systems, we derived a condition on the exponent to guarantee the minimum convergence time.

Current Status and Future Strategies to Treat Spinal Cord Injury with Adult Stem Cells

Jeong, Seong Kyun,Choi, Il,Jeon, Sang Ryong The Korean Neurosurgical Society 2020 Journal of Korean neurosurgical society Vol.63 No.2

Spinal cord injury (SCI) is one of the most devastating conditions and many SCI patients suffer neurological sequelae. Stem cell therapies are expected to be beneficial for many patients with central nervous system injuries, including SCI. Adult stem cells (ASCs) are not associated with the risks which embryonic stem cells have such as malignant transformation, or ethical problems, and can be obtained relatively easily. Consequently, many researchers are currently studying the effects of ASCs in clinical trials. The environment of transplanted cells applied in the injured spinal cord differs between the phases of SCI; therefore, many researchers have investigated these phases to determine the optimal time window for stem cell therapy in animals. In addition, the results of clinical trials should be evaluated according to the phase in which stem cells are transplanted. In general, the subacute phase is considered to be optimal for stem cell transplantation. Among various candidates of transplantable ASCs, mesenchymal stem cells (MSCs) are most widely studied due to their clinical safety. MSCs are also less immunogenic than neural stem/progenitor cells and consequently immunosuppressants are rarely required. Attempts have been made to enhance the effects of stem cells using scaffolds, trophic factors, cytokines, and other drugs in animal and/or human clinical studies. Over the past decade, several clinical trials have suggested that transplantation of MSCs into the injured spinal cord elicits therapeutic effects on SCI and is safe; however, the clinical effects are limited at present. Therefore, new therapeutic agents, such as genetically enhanced stem cells which effectively secrete neurotrophic factors or cytokines, must be developed based on the safety of pure MSCs.

ORIGINAL ARTICLE : A Suggestion of Modified Classification of Trigeminal Schwannomas According to Location, Shape, and Extension

( Seong Kyun Jeong ),( Eun Jung Lee ),( Yun Hee Hue ),( Young Hyun Cho ),( Jeong Hoon Kim ),( Chang Jin Kim ) 대한뇌종양학회 대한신경종양학회 2014 Brain Tumor Research and Treatment Vol.2 No.2

Background Comprehensive knowledge of the anatomical features of trigeminal schwannomas (TSs) is essential in planning surgery to achieve complete tumor resection. In the current report, we propose a modified classification of TSs according to their location of origin, shape, and extension into the adjacent compartment, and discuss appropriate surgical strategies with this classification. Methods We retrospectively analyzed 49 patients with TS who were treated surgically by a single neurosurgeon at the Asan Medical Center between 1993 and 2013. Results There were 22 males and 27 females, with the median age of 40 years (range, 21?75 years). Median tumor size was 4.0 cm in diameter (2.0?7.0 cm). Tumors were classified as follows: Type M (confined to the middle fossa; 8 cases, 19.0%), P (confined to the posterior fossa; 2 cases, 4.8%), MP (involving equally both middle and posterior fossae; 5 cases, 11.9%), Mp (predominantly middle fossa with posterior fossa extension; 6 cases, 14.3%), Pm (predominantly posterior fossa with middle fossa extension; 16 cases, 38.1%), Me (predominantly middle fossa with extracranial extension; 4 cases, 9.5%). Surgical approach was chosen depending on the tumor classification. More specifically, a frontotemporal craniotomy and extradural approach with or without zygomatic or orbitozygomatic osteotomy was applied to M- or Mp-type tumors; a lateral suboccipital craniotomy with or without suprameatal approach was applied to the majority of P- or Pm-type tumors; and a posterior transpetrosal approach was used in four tumors (three Pm and one MP). Gross total resection was achieved in 95.9% of patients, and the overall recurrence rate was 4.1% (2 patients). Postoperatively,trigeminal symptoms were improved or unchanged in 51.0% of cases (25 patients). Surgical complications included meningitis (5 patients) and cerebrospinal fluid leakage (3 patients). There was no mortality. Conclusion TSs are well to be classified with our modified classification and able to be removed effectively and safely by selecting appropriate surgical approaches.