• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.155-160
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• 2006

In this paper, we propose a spatial filtering scheme using factorial kriging, one of geostatistical filtering methodin order to separate regional and residual gravity anomaly. This scheme is based on the assumption that regional anomalies have longer distance relation and residual anomalies have effected on smaller range. We decomposed gravity anomalies intotwo variogram models with long and short effectiveranges by means of factorial kriging. And decomposed variogram models produced the regional and residual anomalies. This algorithm was examined using by a synthetic gravity data, and applied to a real microgravity data to figure out abandoned mineshaft.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.3
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• pp.258-264
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• 2004

In this paper, MMIC double balanced star mixer for 40 ㎓ was implemented on GaAs substrate with backside vias. In the design of the MMIC mixer, the design of balun and diode was required. A novel balun structure using microstrip to CPS was presented. The 40 ㎓ balun was designed based on the design experience of the scale-down balun by 2 ㎓. The balun may be suitable for fabrication in MMIC process with backside via and can easily be applied for DBM(Double Balanced Mixer). A Schottky diode was designed and implemented using p-HEMT process considering the compatability with other high frequency MMIC's fabricated on p-HEMT base process. Finally, the double balanced star mixer was fabricated using the balun and the p=HEMP Schottky diode. The measured performance of mixer shows 30 ㏈ conversion loss at 18 ㏈m LO power. This insufficient performance is caused by the unwanted diode at AlGaAs junction in vertical structure of p-HEMT. If the p-HEMT's gate is recessed to AlGaAs layer, and so the diode is eliminated, the mixer's performances will be improved.

• Composites Research
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• v.31 no.4
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• pp.151-155
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• 2018

Mechanical joint and adhesive joint are two typical joining methods for structures. The adhesive joints distribute the load over a larger area than mechanical joints and have excellent fatigue properties. However, the strength of adhesive joint greatly depends on the environmental conditions and the skill of the operator. Therefore, there is a need for techniques to evaluate the quality of the adhesive joints. The electric resistance method is a very promising technique for detecting defects by measuring the electrical resistance of an adhesive joint in which CNTs are dispersed in an adhesive. In this study, Aluminium-Aluminium adhesive single lap joint specimens were fabricated by using the adhesive dispersing CNTs using a sonicator and a 3-roll mill, and the static strengths and defect detection capabilities of the joints using the electrical resistance method were evaluated according to the CNTs content.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.222-222
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• 2010

III-V반도체 태양전지는 다양한 에너지 밴드갭을 만들 수 있으며 다중접합 태양전지의 경우 흡수 전류가 커져 효율이 증가한다. 태양전지의 효율의 증가는 태양광 발전시스템의 발전 단가를 낮추는 중요한 요인이다. 우리는 효율이 높은 III-V 태양전지를 제작하기 위해 일차적으로 Ge기판 위에 GaAs를 성장하고자 한다. Ge기판과 GaAs의 격자상수는 0.07%차이로 거의 일치하나 물질의 열팽창계수가 다르고 비극성인 Ge기판 위에 극성인 GaAs를 성장 시 위상불일치(Anti Phase Domain) 나타난다. 위상불일치 현상을 줄이기 위해 성장 시 온도와 V/III비율, 성장두께 등을 달리하여 성장한다. 표면의 상태가 좋아질수록 위상불일치 현상이 작으며 단일성장 보다 두 단계 과정으로 성장 했을 때 표면의 상태가 더 좋은 결과를 바탕으로[1], 20nm 이하로 얇게 seed층을 성장하고 그 위에 두꺼운 버퍼층을 성장하는 두 단계로 진행하였다. seed층의 성장온도는 $400{\sim}550^{\circ}C$, V/III 비율을 3.5~30으로 다양하게 바꿔가면서 표면의 상태를 비교하였다. 이때 버퍼층의 성장 온도와 V/III 비율은 $680^{\circ}C$, 192으로 일정하게 유지하였다. 표면은 SEM과 AFM을 통해 분석하였으며 결정질의 상태는 XRD 장비(Panalytical사)로 분석하고 광학적 특성은 LTPL(Accent Optical Technologies사)로 측정하였다. 실험의 결과는 seed층의 온도가 낮고 V/III 비율이 낮으며 성장률이 높았을 때 표면상태가 좋은 반면 버퍼층은 온도가 높고 V/III 비율이 높으며 성장률이 낮을 때 표면상태가 좋았다. seed층을 $450^{\circ}C$온도에서 V/III 비율이 3.5이고 성장률이 버퍼층에 비교하여 크게 하여 성장 했을 때 표면 거칠기가 3.75nm로 작아 표면의 상태가 좋음을 확인할 수 있었다. 두 단계 성장 시 표면의 상태는 seed층의 조건에 따라 결정됨을 알 수 있었다. 표면상태가 좋았을 때 결정상태 역시 좋았으며 성장률이 바뀜에 따라 반치폭이 42~45 arcsec의 값을 나타내었다. 광학적 특성은 10K에서 1.1512eV 밴드갭 에너지를 가지고 있어 양질의 GaAs가 성장됨을 알 수 있다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.329.2-329.2
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• 2014

지난 수년간 태양전지의 광전변환효율을 높이기 위해 자가 조립된 InAs 또는 GaSb와 같은 양자점을 GaAs 단일 p-n 접합에 적용하는 연구를 개발해 왔다. 그러나 양자점의 흡수 단면적에 의한 광 흡수도는 양자점층을 수십 층을 쌓으면 증가하지만 활성층에 결함을 생성시킨다. 생성된 결함은 운반자트랩으로 작용하여 태양전지의 광전변환효율을 감소시킨다. 본 실험에서는 양자점이 적용된 태양전지와 적용되지 않은 태양전지의 광전변환 효율을 비교하고, 깊은준위 과도용량 분광법을 이용하여 결함상태를 측정 및 비교함으로써, 활성층 내부에 생성된 결함이 광전변환 효율에 미치는 영향을 분석하였다. 소자구조는 분자선 증착 방법을 이용하여, 먼저 n+-형 GaAs기판위에 n+-형 GaAs를 250 nm 증착한 후, 도핑이 되지 않은 GaAs활성층을 $1{\mu}m$ 두께로 증착하였다. 마지막으로 n+ 와 p+-형 GaAs를 각각 50, 750 nm 증착함으로써 p-i-n구조를형성하였다. 여기서, n+-형 GaAs 과 p+-형 GaAs의 도핑농도는 동일하게 $5{\times}1018cm-3$로 하였다. 또한 양자점을 태양전지 활성층에 20층을 형성하였다. 이때 p-i-n 태양전지 와 양자점 태양전지의 광전변환 효율은 각각 5.54, 4.22 % 를 나타내었다. p-i-n 태양전지의 개방 전압과 단락전류는 847 mV, 8,81 mA이며 양자점 태양전지는 847 mV, 6.62mA로 확인되었다. 태양전지의 전기적 특성을 측정하기 위해 소자구조 위에 Au(300nm)/Pt(30nm)/Ti(30nm)의 전극을 전자빔증착장치로 증착하였으며, 메사에칭으로 직경 $300{\mu}m$의 태양전지 구조를 제작하였다. 정전용량-전압 특성 및 깊은준위 과도용량 분광법을 이용하여 태양전지의 결함분석 및 이에 따른 광전변환 특성인자와의 상관관계를 논의할 것이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.349-349
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• 2012

박막형 GaAs 계 III-V 태양전지는 ELO (Epitaxy Lift-off) 기술에 의하여 기판으로부터 분리되어 얻어질 수 있다. 지금까지 이 기술에 대해 개발된 결과에 의하면 박막 III-V 태양전지의 효율이 기존 기판 기반의 태양전지 효율과 비슷한 수준을 얻고 있으며, 기판의 재활용, 플렉서블, 및 신축성 태양전지로의 적용분야 등의 보고들도 발표되고 있어 실리콘 태양전지가 접근하기 힘든 특정한 응용분야로의 가능성을 밝게 해주고 있다. 그러나, 이 ELO방식에 의한 박막형 III-V 태양전지가 실질적으로 상업화 되기 위해서는 생산 수율의 개선 및 기판 재활용 시의 저손실 등 해결해야 할 당면과제들이 놓여 있다. 기판재활용의 가능성을 위해 아직까지 발표된 셀의 크기는 $2{\times}2mm^2$ 이하이며, 보다 넓은 셀에 대하여 기판재활용 방식으로 재생된 효율을 갖는 III-V 박막 태양전지는 보고된 바 없다. 본 연구에서는, $1{\times}1mm^2$, $2{\times}2mm^2$, 그리고 $5{\times}5mm^2$에 대하여 ELO 에 의한 박막 태양전지를 제작해 보고, 보다 넓은 면의 박막 태양전지를 효율적으로 제작하기 위한 방법을 연구하고자 한다. 또한, 이 셀들을 유연한 PDMS transfer에 부착하여 플렉서블 태양전지로의 가능성에 대해서도 기술하고자 한다. 사용된 박막 태양전지 구조는 한국광기술원에서 제작한 22% GaAs 단일 접합 태양전지와 같은 구조로 되어 있으며, 희생층으로는 AlGaAs 층을 사용하였고, ELO을 위한 에칭용 홀 지름은 5, 10, 그리고 $20{\mu}m$에 대하여 조사하였다.

• Korean Journal of Microbiology
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• v.36 no.1
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• pp.1-7
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• 2000

The genes involved in riboflavin synthesis (ribI, II, III, and IV) were found immediately downstream of luxG in the lux operon from Photobacterium species. The single stranded DNA containing the intergenic region of lux genes and rib genes from Photobacterium phosphoreum was fully protected by P. phosphoreum mRNA from the S1 nuclease mapping assay suggesting that a transcriptional terminator was not present in the region. In addition, the levels of riboflavin synthase activity in P. phosphoreum was increased during the development of bacterial bioluminescence in the same fashion as the luciferase and fatty acid reductase activities. Insertion of the Photobacterium leiognathi DNA extending from luxB to ribII, between a strong lux promoter and a reporter gene (chloramphenicol acetyltransferase, CAT) and transferred by conjugation into P. leiognathi, did not affect expression of reporter gene. Moreover the CAT gene was not expressed in an analogous construct missing the lux promoter indicating that a promoter was not present in this region. Based on the data here, it can be concluded that the lux genes and rib genes in Photobacterium species are under common regulation.

• Korean Journal of Animal Reproduction
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• v.18 no.3
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• pp.199-206
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• 1994

We present here a new PCR-based cloning technique that allows the different PCR products during mouse embryogenesis. Recently, mRNA differential display described by Liang & Pardee (Science 257, 1992) and re-confirmed by Zimermann & Schultz (PNAS 91,1994). This method will detect the appropriate changes in the temporal patterns of expression or in the transition from maternal control to zygotic control as well as the functional difference of embryo with polyspermy or monospermy, the difference of expression between successfully hatched blastocyst and blastocyst failed to hatching, response to agents, and cell cycle regulation. By this methods, we have cloned an eDNA, which showed mouse 2 cell specific expression. Genomic DNA digested with EcoRI showed approximately 15 kb and then showed higher expression in fetal liver rather than adult liver. Furthermore, this gene is likely to have 2 mRNA by alternative splicing.

• Archives of Reconstructive Microsurgery
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• v.18 no.1
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• pp.27-30
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• 2009

Purpose: Recently, replantation of fingertip amputation, Zone I by Yamano classification, is still difficult because digital arteries branch into small arteries and also digital veins are hard to separate from the immobile soft tissue. However the replantation of fingertip in adults is a well-established procedure, but the replantation in infant or child is still uncommon. Therefore we present one case of replantation of the fingertip of the small finger in 12-months-old patient. Methods: We experienced a 12-months-old male amputation of small finger. It had been amputated completely at the level of Zone I by Yamano classification. Replantation was performed using the arteryonly technique with neither vein nor nerve repair. Because the artery has been damaged, it is still possible to make a direct suture by transposing the arterial arch in an inverted Y to I arterial configuration. Venous drainage was provided by an external bleeding method with partial nail excision and repaired margin for approximately 7 days. Results: We were performed replantation in infant with only-arterial anastomosis successfully, result in good recovery of aesthetic and functional outcome. Conclusion: In conclusion, although fingertip injury was difficult to replantation in infant and child, we must try it. Because of its functional and cosmetic advantage.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.3
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• pp.331-340
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• 2010

The basic theory and application of new adaptive finite element algorithm have been proposed in this study including the adaptive hp-refinement strategy, and the effective method for constructing hp-approximation. The hp-adaptive finite element concept needs the integrals of Legendre shape function, nonuniform p-distribution, and suitable constraint of continuity in conjunction with irregular node connection. The continuity of hp-adaptive mesh is an important problem at the common boundary of element interface. To solve this problem, the constraint of continuity has been enforced at the common boundary using the connectivity mapping matrix. The effective method for constructing of the proposed algorithm has been developed by using hierarchical nature of the integrals of Legendre shape function. To verify the proposed algorithm, the problem of simple cantilever beam has been solved by the conventional h-refinement and p-refinement as well as the proposed hp-refinement. The result obtained by hp-refinement approach shows more rapid convergence rate than those by h-refinement and p-refinement schemes. It it noted that the proposed algorithm may be implemented efficiently in practice.