• 전기학회논문지
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• 제63권12호
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• pp.1716-1721
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• 2014

In this paper, a study on automation method for the circuit/EM (Electro-Magnetic) simulation is carried out to analyze effectively the SI/PI (Signal Integrity/Power Integrity) issues which occur on circuits and/or PCBs (Printed Circuit Boards). For the automation of the circuit/EM simulation, algorithms performing each process of the SI/PI analysis automatically (such as ports setup, circuit definition and SI/PI evaluation) are developed; thereby automation system for the SI/PI analysis is constructed with the algorithms. The automation of the circuit/EM simulation is accomplished in the environment of the C/S (Client/Server) architecture in order to reduce resources such as high cost computers demanded for the SI/PI analysis. The automation method for the SI/PI analyses proposed in this paper reduces effort, time, and cost spent on the environment setup for simulation and the SI/PI analysis process. In addition, the proposed method includes automation of the documenting process, which organizes, records and displays the SI/PI analysis results automatically for users.

• 한국재료학회지
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• 제12권9호
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• pp.750-760
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• 2002

In this study, three solders, Sn-37Pb, Sn-3.5Ag, and Sn-3.8Ag-0.7Cu were screen printed on both electroless Ni/Au and OSP metal finished micro-via PCBs (Printed Circuit Boards). The interfacial reaction between PCB metal pad finish materials and solder materials, and its effects on the solder bump joint mechanical reliability were investigated. The lead free solders formed a large amount of intermetallic compounds (IMC) than Sn-37Pb on both electroless Ni/Au and OSP (Organic Solderabilty Preservatives) finished PCBs during solder reflows because of the higher Sn content and higher reflow temperature. For OSP finish, scallop-like $Cu_{6}$ /$Sn_{5}$ and planar $Cu_3$Sn intermetallic compounds (IMC) were formed, and fracture occurred 100% within the solder regardless of reflow numbers and solder materials. Bump shear strength of lead free solders showed higher value than that of Sn-37Pb solder, because lead free solders are usually harder than eutectic Sn-37Pb solder. For Ni/Au finish, polygonal shaped $Ni_3$$Sn_4$ IMC and P-rich Ni layer were formed, and a brittle fracture at the Ni-Sn IMC layer or the interface between Ni-Sn intermetallic and P-rich Ni layer was observed after several reflows. Therefore, bump shear strength values of the Ni/Au finish are relatively lower than those of OSP finish. Especially, spalled IMCs at Sn-3.5Ag interface was observed after several reflow times. And, for the Sn-3.8Ag-0.7Cu solder case, the ternary Sn-Ni-Cu IMCs were observed. As a result, it was found that OSP finished PCB was a better choice for solders on PCB in terms of flip chip mechanical reliability.

• Bulletin of the Korean Chemical Society
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• 제27권5호
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• pp.649-656
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• 2006

The proposed head-space supercritical fluid extraction (SFE) methodology as an alternative to an existing conventional procedure was explored for the determination of organochlorine compounds in aqueous matrix. In this study, polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were utilized as target analytes. To enhance the recovery efficiency, the factors such as the $CO _2$ density, the extraction time, and the extraction mode were investigated. Furthermore, the analytical procedures and the results obtained were compared with those provided by the conventional method (the U.S. EPA method 8080). Under the optimized conditions, i.e., a combination of static with dynamic SFE mode at 2,000 psi and 40 ${^{\circ}C}$, the head-space SFE methodology gave equivalent or better to the conventional method in recovery efficiencies with clear advantages such as simple sample treatment and fast analysis time as well as reduced solvent and reagent consumption.

• 전기학회논문지
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• 제66권10호
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• pp.1508-1515
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• 2017

This paper proposes the defect detection method for automatic inspection machines in printed circuit boards (PCBs) manufacturing system. The defects of PCB such as open, short, pin hole and scratch can be detected by comparing the standard image and the target image. The standard image is obtained from CAD file such as ODB++ format, and the target image is obtained by arranging, filtering and binarization of captured PCB image. Since the PCB size is too large and image resolution is too high, the image processing requires a lot of memory and computational time. The wavelet transform is applied to compress the standard and target images, which results in reducing the memory and computational time. To increase the inspection accuracy, we utilize the he HH-domain as well as LL-domain of the transformed images. Experimental results are finally presented to show the performance improvement of the proposed method.

• 한국대기환경학회지
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• 제19권5호
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• pp.469-490
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• 2003

Atmospheric concentrations of persistent organic pollutants (POPs) were measured at Gosan, Jeju in November 2001 and spring 2002, each time for two weeks. Primary target pollutants were organochlorine pesticides, coplanar polychlorinated biphenyls (co- PCBs), and dioxin/furans listed in the Stockholm Convention adopted in May 2001. Polycyclic aromatic hydrocarbons (PAHs) were also measured in order to understand the overall characteristics of the POPs distribution as well as PM$_{2.5}$, a potent carrier of POPs. In the latter part of the measurement period of November 2001, almost every pollutant of combustion origin including dioxin/furans went high probably due to influence of emissions in the nearby area. The characteristics of atmospheric environment at Gosan in this period were rather close to urban areas far from those of a background area. A severe dust storm swept for three days at the end of the measurement period of spring 2002. However, changes in pollutant concentrations were relatively small except PM$_{10}$. Nevertheless, increases in particulate PAHs and OCDD (octachlorinated dibenzo-p-dioxins), mostly present in fine particles, were observed. Trends in organochlorine pesticide variations were mixed although possible volatilization of DDT residues from soil was inferred from the measurements of spring 2002.2.2.

• 한국패류학회지
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• 제30권4호
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• pp.371-381
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• 2014

The bioaccumulation of 16 United States Environmental Protection Agency (USEPA) priority polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs in the Manila clam, Ruditapes philippinarum exposed to sediments artificially contaminated by Iranian Heavy Crude Oil was measured and the biota-sediment accumulation factor (BSAF) was estimated through laboratory experiments. The proportion of 16 PAHs accumulated in the tissue of R. philippinarum was only from 3 to 7% of total PAHs. Among 16 PAHs, the concentration of naphthalene was highest in the tissue. Alkylated PAHs were highly accumulated more than 93% of total PAHs. The C3 dibenzothiophene was most highly accumulated. The relative composition of alkylated naphthalenes in the tissue of R. philippinarum was lower than in the sediments. In contrast, those of alkylated compounds of fluorenes, phenanthrenes, dibenzothiophenes were higher in the tissue than the sediments. The BSAF for sum of 16 PAHs was 0.11 to 0.13 g carbon/g lipid and that for alkylated PAHs was 0.05 to 0.06 g carbon/g lipid. Naphthalene showed the highest BSAF value. Alkylated PAHs with the same parent compound, BSAF tended to increase with the number of alkylated branch increased, except for alkylated chrysenes. BSAF of total PAHs lies between that of field-based values, and are also similar to those of other persistent organic pollutants (PCBs, DDTs, HCHs). This study provides the BSAF values of individual alkylated PAHs accumulated in R. philippinarum for the first time and will be used as a basis for further understanding the bioaccumulation of organic contaminants in the marine benthic organisms.

• 마이크로전자및패키징학회지
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• 제16권2호
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• pp.43-50
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• 2009

최근 인쇄회로기판(PCB)의 제품트랜드는 박형화, 고밀도화로 대표되지만 휨(Warpage) 억제, 신뢰성확보와 같은 기술적 난제로 인해 박형화와 고밀도화에 많은 제약을 받고 있다. $B^2it$(Buried Bump Interconnection Technology) 공법은 기판의 핵심공정 중 하나인 드릴링 공정이 생략되어 인쇄회로기판을 낮은 제조비용으로 박형화할 수 있는 기술로 개발되고 있다. 본 논문은 $B^2it$공법이 적용된 인쇄회로기판의 열적-기계적 거동특성을 유한요소해석(FEA)을 통해 고찰한 논문으로서 패키징레벨에서 방열효과와 신뢰성 등에 벙프의 재료, 형상 등이 미치는 영향 등을 분석하였다. 해석결과에 의하면 $B^2it$공법이 적용한 인쇄회로기판은 기존 비아구조를 가진 인쇄회로기판에 비해 칩에서 발생하는 열의 확산이 신속하고 패키징의 휨을 억제하는데도 유리하며 칩에서 발생하는 응력도 낮추지만 솔더-조인트의 응력은 증가시키게 된다. 따라서 패키징의 신뢰성을 향상시키기 위해서는 범프의 형상, 재료 등을 패키징을 구성하고 있는 모든 요소들을 고려하여 최적화하는 것이 필요하다.

• 한국발생생물학회:학술대회논문집
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• 한국발생생물학회 2003년도 제3회 국제심포지움 및 학술대회
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• pp.63-63
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• 2003

In an effort to uncover the spermatogenic impairment by the polychlorinated biphenyls (PCBs), the expression of tight junctions (TJs) genes important for the formation of the blood testis barrier (BTB) were examined following the 3,3',4,4',5-pentachloro biphenyl (PCB126) treatment in cultured neonatal testis in mice. At 4 days (D4) after 10 and 100 nM PCB126 treatment the expression of claudin-11 was significantly increased when compared with vehicle control. In contrast no difference in occludin and claudin-1 expression was found among the experimental group. On D8, 100 nM PCB126 significantly increased the expression of claudin-11 but not occludin and claudin-1. 1 uM PCB126 treatment significantly decreased expressions of occludin and ciaudin -1, suggesting the general toxic effect on the Sertoli cell. Because PCB126 does not alter the proliferative activity of spermatogenic cells and Sertoli cells in neonatal testis, it is likely that increase in the expression of claudin-11 by low dose of PCB126 may attribute to the alteration of the Sertoli cells differentiation in testis. It also emphasized that PCB126 might have differentially affected the transcription of TJ genes in Sertoli cells. In conclusion, this result suggests that the structure of TJ may be targeted by PCB126 in neonatal testis in mice and that co-PCB is potentially harmful to spermatogenesis by alteration of the development of BTB.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2005년도 총회 및 춘계학술발표회
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• pp.28-30
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• 2005

Because of high population diversity in soil microbial communities, it is difficult to accurately assess the capability of biodegradation of toxicant by microbes in soil and sediment. Identifying biodegradative microorganisms is an important step in designing and analyzing soil bioremediation. To remove non-important noise information, it is necessary to selectively enrich genomes of biodegradative microorganisms fromnon-biodegradative populations. For this purpose, a stable isotope probing (SIP) technique was applied in selectively harvesting the genomes of biphenyl-utilizing bacteria from soil microbial communities. Since many biphenyl-using microorganisms are responsible for aerobic PCB degradation In soil and sediments, biphenyl-utilizing bacteria were chosen as the target organisms. In soil microcosms, 13C-biphenyl was added as a selective carbon source for biphenyl users, According to $13C-CO_2$ analysis by GC-MS, 13C-biphenyl mineralization was detected after a 7-day of incubation. The heavy portion of DNA(13C-DNA) was separated from the light portion of DNA (12C-DNA) using equilibrium density gradient ultracentrifuge. Bacterial community structure in the 13C-DNAsample was analyzed by t-RFLP (terminal restriction fragment length polymorphism) method. The t-RFLP result demonstates that the use of SIP efficiently and selectively enriched the genomes of biphenyl degrading bacteria from non-degradative microbes. Furthermore, the bacterial diversity of biphenyl degrading populations was small enough for environmental genomes tools (metagenomics and DNA microarrays) to be used to detect functional (biphenyl degradation) genes from soil microbial communities, which may provide a significant progress in assessing microbial capability of PCB bioremediation in soil and groundwater.

• Bulletin of the Korean Chemical Society
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• 제20권6호
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• pp.689-695
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• 1999

Supercritical fluid extraction (SFE), ultrasonic extraction (USE), and accelerated solvent extraction (ASE) were compared with the well known Soxhlet extraction for the extraction of polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins(PCDDs) from the XAD-2 resin which was used to adsorb PCDDs in the atmosphere. XAD-2 resin spiked with five PCDDs was chosen as a sample. The optimum conditions for the extraction of PCDDs by SFE were turned out to be the use of CO2 modified with 10% toluene at 100 ℃ and 350 atm, with 5 min static extraction followed by 20 min dynamic extraction. SFE gave a good extraction rate with good reproducibility for PCDDs ranging from 68 to 98%. The ultrasonic extraction of PCDDs from XAD-2 was investigated and compared with other extractions. A probe type method was compared with a bath type. Two extraction solvents, toluene and acetone were compared with their mixture. The use of their mixture in probe type, with 9 minutes of extraction time, was found to be the optimum condition. The average recovery of the five PCDDs for USE was 82-93%. Accelerated solvent extraction (ASE) with a liquid solvent, a new technique for sample preparation, was performed under elevated temperatures and pressures. The effect of tem-perature on the efficiency of ASE was investigated. The extraction time for a 10 g sample was less than 15 min, when the organic solvent was n-hexaneacetone mixture (1 : 1, v/v). Using ASE, the average recoveries of five PCDDs ranged from 90 to 103%. SFE, USE, and ASE were faster and less laborious than Soxhlet extraction. The former three methods required less solvent than Soxhlet extraction. SFE required no concentration of the solvent extracts. SFE and ASE failed to perform simultaneous parallel extractions because of instrumental limitations.