• Journal of Microbiology and Biotechnology
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• 제20권12호
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• pp.1624-1629
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• 2010

Bacterial cell-to-cell communication, termed quorum sensing (QS), leads to coordinated group behavior in a cell-density-dependent fashion and controls a variety of physiological processes including virulence gene expression. The repressor of the lsr operon, LsrR, is the only known regulator of LuxS/AI-2-mediated QS in Salmonella. Although lack of lsrR did not result in noticeable differences in Salmonella survival, the down-regulation of QS as a result of lsrR overexpression decreased Salmonella survival within macrophages. We found that impaired growth of Salmonella overexpressing lsrR within macrophages was due largely to its hypersensitivity to NADPH-dependent oxidative stress. This, in turn, was a result of decreased expression of genes involved in the oxidative stress response, such as sodA, sodCI, and sodCII, when lsrR was overexpressed. These results suggest that down-regulation of QS by excess LsrR can lower Salmonella virulence by hampering Salmonella evasion from oxidative killing within macrophages.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.232-235
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• 2002

Recently developed liquid silicone rubber (LSR) can be cured by platinum catalyzed additional hydrosilylation mechanism and has the advantage of no byproduct compared to traditional millable peroxide curing silicone rubber. We investigated the characteristics of dielectric breakdown of silicone rubber and adhesion properties between semi-conductive LSR and insulating LSR for high voltage application of pre-molded joint (PMJ). In order to understand the dielectric breakdown characteristics, we used the sheet samples and the paired type rogowski insert electrode system. The breakdown strength and adhesion strength of LSR (E-3) were superior to those of several silicone rubbers. Adhesion strength could be improved by curing at high temperature without post-curing process or enhanced by post-curing process. When LSR (E-3) was cured at $(150^{\circ}C{\times}10min$ semi-conductive )${\times}$ ($175^{\circ}C{\times}10min$ insulation), it showed the high breakdown strength with low standard deviation, and good adhesion strength. In this results, we could apply this process to the fabrication of PMJ without post-curing.

• 한국생산제조학회지
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• 제23권2호
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• pp.206-212
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• 2014

Liquid silicone rubber (LSR) has been widely used in automotive, electrical, and medical components. Thus, research on the use of LSR in the injection molding process is required to obtain high-quality and high-performance products. In this study, a mold was fabricated to examine the effects of the process parameters on the molding and mechanical properties of LSR parts. A computer-aided engineering analysis was used to optimize the air vent depth and curing temperature to decrease the flash at the air vents caused by the low viscosity of LSR. Temperature and pressure sensors were mounted in the mold to determine the effects of the process parameters on the temperature and pressure in the cavity. The tensile strength of the LSR parts was also examined in relation to the process parameters.

• 한국산학기술학회논문지
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• 제18권7호
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• pp.310-315
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• 2017

자동차용 방수커넥터는 외부로부터 방수가 필요한 전장부품인 와이어 하네스(Wire Harness)에 연결되어 있는 핵심기능부품이며 특히 와이어씰(Wire Seal) 부품은 고온, 다습, 저온, 먼지, 약품 등의 복합적 환경에서도 체결부 기밀성이 확보되어야 한다. 이러한 와이어씰은 최근 기존의 고상실리콘고무(Heat Cure Rubber)대신 친환경 소재이며 기계적 특성이 우수한 액상실리콘고무(LSR)를 적용하고 있다. 그리고 LSR용 와이어씰을 액상사출성형(Liquid Injection Molding)공정으로 제조할 경우 고상실리콘고무를 제조 하긴 위한 압축성형방식에 비해 사이클타임이 10배이상 빠르고 스크랩이 발생하지 않아 재료의 손실이 없으며 가류 및 생산을 위한 전후처리 과정이 필요 없기 때문에 원가 절감효과가 큰 이점이 있다. 하지만, 방수커넥터를 제조하기 위한 LSR 다캐비티 사출성형공정에서는 일정한 품질의 제품을 확보하기 위하여 캐비티간 균일한 경화온도를 유지하는 것이 중요하다. 본 연구에서는 캐비티간 온도 편차를 최소화 하기 위하여 카트리지 히터의 용량을 위치마다 다르게 설계한 후 열전달 해석과 최적화 모듈을 연계하여 최적의 카트리지 히터 용량을 빠르고 효율적으로 도출하였다. 최적화 해석결과 일정한 히터 용량을 적용한 경우에 비하여 캐비티간 온도 편차는 $13.1^{\circ}C$에서 $8.1^{\circ}C$로 감소 시켜 균일 경화를 위한 온도 편차 $10^{\circ}C$ 이내인 설계 기준을 만족시킬 수 있었다.

• Environmental Engineering Research
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• 제22권4호
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• pp.339-346
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• 2017

The objective of this study is the evaluation of the performance of a large-scale respirometer (LSR) of 17.7 L in the determination of the methane generation rate constant (k) values. To achieve this objective, a comparison between anaerobic (GB21) and LSR tests was conducted. The data were modeled using a linear function, and the resulting correlation coefficient ($R^2$) of the linear regression is 0.91. This result shows that despite the aerobic conditions, the biodegradability values that were obtained from the LSR test produced results that are similar to those from the GB21 test. In this respect, the LSR test can be an indicator of the anaerobic biodegradability for landfill waste. In addition, the results show the high repeatability of the tests with an average coefficient of variance (CV) that is lower than 10%; furthermore, the CV for the LSR is lower than that of the GB21, which indicates that the LSR-test method could provide a better representation of waste samples. Therefore, the LSR method allows for both the prediction of the long-term biodegradation potential in a shorter length of time and the reduction of the sampling errors that are caused by the heterogeneity of waste samples. The k values are $0.156y^{-1}$ and $0.127y^{-1}$ for the cumulative biogas production (GB21) and the cumulative oxygen uptake for the LSR, respectively.

• Design & Manufacturing
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• 제7권1호
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• pp.60-63
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• 2013

Recently, Silicone that one of the thermo-sets is used to making optical products such as LED lenses because of excellent thermal properties. LED lenses are required to keep the precise dimensions, so they must be molded to have the minimum deformation. Thermo-sets have the expansion characteristic on the part of thermal property, it is important to optimize the cure condition so that the deformation of the part become minimum. In this study, to investigate the relationship between the shrinkage by the curing and expansion by the thermal properties of the resin, reactive injection experiment was performed by setting the variables such as mold setting temperature, cure time. As a result, it was confirmed that there was a interval while the thermal properties were transferred to more active during the cure process. It is expected to help in determining the reactive injection molding conditions of the thermo-set parts as well as LED lens in order to reduce the amount of deformation.

• 한국시뮬레이션학회논문지
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• 제12권1호
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• pp.11-19
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• 2003

Dubins showed that any shortest path of a car-like robot consists of exactly three path segment which are either arcs of circles of radius r(denoted C), or straight line segments(denoted S). Possible six types classified into two families, i.e. CSC and CCC. CSC includes 2 types(LRL and RLR) and CSC includes 4 types(LSL, RSR, LSR, RSL). This paper proposes new formulae for CSC family to find the shortest smooth path between the initial and final configurations of a car-like robot. The formulae is used for finding connection points explicitly between C\longrightarrowS and S\longrightarrowC which are necessary for real applications. The formulae have simple forms mainly because they are transformed into origin of their original coordinates of initial and target configuration, and derived from a standard forms which are a representative configuration of LSL and LSR type respectively. The proposed formulae, which are derived from the standard forms, are simple and new method.

• 천문학회지
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• 제29권spc1호
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• pp.173-174
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• 1996

We have mapped $17 deg^2$ region toward Galactic anticenter in $^{12}CO$ J = 1 - 0 using the 3 mm SIS receiver on the 14 m telescope at Taeduk Radio Astronomy Observatory (TRAO). The region mapped in this paper is the first target of the Galactic AntiCenter CO Survey Project (GACCOS) and was selected comparing with IRAS Sky Survey Atlas (ISSA) images at 100${\mu}m$. Molecular emission of the target area is found to be very extended and is well matching with the FIR emission boundary. There are several pieces of clouds, and as some of spectra show several peaks, there seem to be several clouds overlapped in some directions. The Velocity of Local Standard of Rest ($V_{LSR}$) of the CO emission of the mapped region ranges from -20 to +10 km/s. It is also found that the two cloudlets located around I = $180^{\circ}$ have $V_{LSR}$ = -20 km/s, which is very abnormal. The peak antenna temperature of 13 K arises near the H II Region S241.

• 천문학논총
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• 제12권1호
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• pp.63-84
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• 1997

We carried out high-resolution(FWHM=3' .3) HI 21 cm observations of the supernova remnant(SNR) PKS0607+17 and HII region S261 using Arecibo 305-m telescope. The observation was to investigate whether the high-velocity(HV) gas detected in the southern area of PKS0607+17 by Koo & Heiles(1991) is physically associated with the SNR or not. The velocity of the HV gas ranges from +64 km/s to +87 km/s, which is difficult to result from the Galactic rotation. The HV gas could be the gas accelerated by supernova blast wave. However, because the observation of Koo and Heiles(1991) was carried out using Hat Creek radio telescope(FWHM $\simeq$ 36'), the association of the HV gas with the SNR could not be investigated. Using the Arecibo HI 21cm data, we have found that the HV gas appears m the southern part of the SNR and its velocity ranges from +61 km/s to +77 km/s. But the HV gas is scattered m the whole field, not only toward PKS0607+17 but also outside the SNR Accordingly the HV gas is probably not associated with the SNR, but is accidentally aligned along the same line of sight toward the SNR. Instead we have found that HI clouds at low velocities could be possibly associated with the SNR. In Arecibo HI 21cm channel maps the HI gas seems to surround the southern boundary of the SNR at $V_{LSR}$ = +19.6 ~ +40.2 km/s. But because the region of the Arecibo HI 21cm observation is not wide enough to examine the HI gas distribution, we investigated this area using the Berkely low-latitude HI survey data(Weaver & Williams 1974) too. There we found HI gas surrounding the radio continuum boundary of PKS0607+17 at $V_{LSR}$ = +21.6 ~ +258 km/s. It is possible that this HI gas is associated with the SNR, in which case, the velocity of the SNR $V_o$ $\simeq$ +26 km/s, its distance d $\simeq$ 12.5 kpc and its radius R $\simeq$ 145 pc. If we assume that the expansion velocity is ~10 km/s, then the age of the SNR is $\sim4.4\times10^6$ years. PKS0607+17 could be one of the oldest SNRs in the Galaxy. We also studied HI propertities of the HII region S261, which is $\sim1^{\circ}$ away from PKS0607+17. There has been no high-resolution m 21 cm observational study on S261. We discovered HI cloud located at the north-eastern part of S261 at $V_{LSR}$ = +5 km/s ~ +10 km/s, which is possibly associated with the HII region. The central velocity of the HI cloud $V_{LSR}$ = +7.2 km/s and the corresponding distance d = 1.5 kpc. This velocity is comparable to the radio recombination line velocities.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.123-127
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• 2003

액상실리콘으로 이루어진 초고압전력케이블용 프리몰드 접속재의 반도전-절연체 계면접합체를 다양한 제조조건과 조합별로 제조하여 계면접착력에 대한 영향을 검토하였다. 후가교적용 시 계면접착력이 강화되며 grade조합에 따른 특성차이가 존재하였다. 하지만 고온 장시간의 후가교 조건에서는 계면간의 화학적 결합력의 저하로 인해 오히려 접착력이 낮아지기도 하였다. 절연 RTV와의 계면접착성은 S-1재료가, 절연 LSR의 경우에는 S-3 재료가 가장 우수하였으며 도전안정성 측면에서도 S-3 재료가 상대적으로 유리하였다. 매입형 전극체를 제조하여 절연파괴거동을 연구한 결과 계면접착성과의 직접적인 상관관계는 크지 않음을 알 수 있었다.