• International Journal of Air-Conditioning and Refrigeration
• /
• 제11권3호
• /
• pp.105-113
• /
• 2003

This study developed a practical two-microphone impedance tube method to measure the sound transmission loss of sound isolation materials without the use of an expensive reverberation room or an acoustic intensity probe. In order to evaluate the validation and applicability of the two-microphone impedance tube method, sound transmission losses for several sound isolation materials with different surface density and bending stiffness were measured, and the measured values were compared with the results from the reverberation room method and the theory. From the experimental results, it was found that the accuracy of sound transmission loss obtained by the impedance tube method depends upon the diameter size of the impedance tube (i.e., tested sample size). For sound isolation materials having relatively large bending stiffness such as acryl, wood, and aluminum plates, it was found that the impedance tube method proposed by this study was not valid to measure the sound transmission loss. On the other hand, for sound isolation materials having relatively small bending stiffness such as rubber, polyvinyl, and asphalt sheets, the comparisons of transmission loss between the results from the impedance tube method and the theory showed a good agreement within the range of the frequencies satisfying the normal incidence mass law. Therefore, the two-microphone impedance tube method proposed by this study can be an effective measurement method to evaluate the sound transmission loss for soft sound isolation sheets having relatively small bending stiffness.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
• /
• pp.1440-1443
• /
• 1997

The optimal residual generator based on parity relation approach for the fault detection and isolation of a arge diesel engine actuator position servo system is presented. The closed-loop residual generator is designed to have robustness against modeling errors and noise. Main purpose of the fault detection and isolation system in the process is to detect and isolate two important faults, i.e., actuatro fault and fault of speed sensor, that, if not detected and compensated, degrade the overall control system performance. Simulation results are give to show the practical applicability of the fault detecrtion and isloation scherme.

• E2M - 전기 전자와 첨단 소재
• /
• 제11권10호
• /
• pp.72-77
• /
• 1998

The effects of Al micro-bumps on the magnetic properties of CoCr(Pt)Ta/Cr films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by incorporating Cr/Al underlayers. The cause of the coercivity increase is attributed to the reduction of Co(0002) texture, the increase of magnetic isolation of CoCr(Pt)/Ta grains, and the refinement of CoCr(Pt)/Ta grains deposited on Cr/Al underlayers. The effects of an Al overlayer on the magnetic properties of CoCr(Pt)Ta/Cr films were also studied. The decrease of coercivity squareness is ascribed to the magnetic isolation of CoCr(Pt)Ta grains.

• Archives of Pharmacal Research
• /
• 제26권9호
• /
• pp.735-738
• /
• 2003

The methanolic extract of the twigs of Celtis chinensis was found to show inhibitory activity on acetylcholinesterase (AChE), an enzyme that plays a role in the metabolic hydrolysis of ACh. Bioassay-guided fractionation of the methanolic extract resulted in the isolation of N-p-coumaroyl tyramine. as an inhibitor on AChE. This compound inhibited AChE activity in a dose-dependent manner, and the $IC_50$ value of trans-N-p-coumaroyl tyramine was 34.5 $\mu$g/mL (122 $\mu$M).

• 한국약용작물학회지
• /
• 제13권4호
• /
• pp.182-185
• /
• 2005

사람들의 생명연장과 각종 만성질환, 악성종양 등의 증가에 따른 우수한 항생제의 계속적인 개발로 많은 생명을 구할 수 있게 되었지만 반면 항생제를 지나치게 사용하여 이에 많은 부작용이 생기고 내성균도 많아지면서 중증감염이 증가되어 여러 가지의 새로운 문제점에 직면하게 되었다. 안전성이 있는 새로운 항균물질의 개발 목적으로 예비 검색 결과 선택된 독활을 추출하여 컬럼 크로마토그래피를 반복 수행한 결과 2종의 항균 효과를 보여주는 화합물을 분리하였다 이들 화합물은 물리 화학적 성질 및 분광학적 분석을 통하여 화합물 1은 mp가 $166{\sim}167^{\circ}C$인 백색침상, $C_{20}H_{30}O_2$의 분자식을 갖는 (-)-pimara-8(14), 15-dien-19-oic acid 즉, continentalic acld으로 동정하였으며, 화합물 2는 mp가 $164{\sim}165^{\circ}C$인 백색침상, $C_{29}H_{48}O$의 분자식을 갖는 $(24E)-stigmasta-5,\;22-dien-3{\beta}-ol$, 즉 stigmasterol으로 동정하였으며 항균효과를 측정한 결과 두 화합물 모두 유의성 있는 결과를 나타내었으며, 이 중 화합물 1인 continentalic acid이 더욱 우수한 활성을 나타내었다. 특히 그람 양성균인 S. aureus에서 MIC가 $7.8\;{\mu}g/ml$, E. faecalis에서는 MIC가 $12.5\;{\mu}g/ml$에서 비교적 강한 억제 효과를 보였으며, 화합물 2에서는 S. aureus에서 MIC가 $7.8\;{\mu}g/ml$, S. epidemidis에서는 MIC가 $12.5\;{\mu}g/ml$에서 억제 효과를 보여 주었으나 그람 음성균에서 $100\;{\mu}g/ml$ 이상으로 항균활성이 측정되지 않았다. 따라서 화합물 1과 화합물 2는 그람 양성균에 대한 새로운 항균제로 개발에 유용한 화합물이 될 것으로 기대된다.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제14권4호
• /
• pp.427-435
• /
• 2014

Segmented-channel MOSFETs (SegFETs) can achieve both good performance and variation robustness through the use of $HfO_2$ (a high-k material) to create the shallow trench isolation (STI) region and the very shallow trench isolation (VSTI) region in them. SegFETs with both an HTI region and a VSTI region (i.e., the STI region is filled with $HfO_2$, and the VSTI region is filled with $SiO_2$) can meet the device specifications for high-performance (HP) applications, whereas SegFETs with both an STI region and a VHTI region (i.e., the VSTI region is filled with $HfO_2$, and the STI region is filled with $SiO_2$) are best suited to low-standby power applications. AC analysis shows that the total capacitance of the gate ($C_{gg}$) is strongly affected by the materials in the STI and VSTI regions because of the fringing electric-field effect. This implies that the highest $C_{gg}$ value can be obtained in an HTI/VHTI SegFET. Lastly, the three-dimensional TCAD simulation results with three different random variation sources [e.g., line-edge roughness (LER), random dopant fluctuation (RDF), and work-function variation (WFV)] show that there is no significant dependence on the materials used in the STI or VSTI regions, because of the predominance of the WFV.

• Smart Structures and Systems
• /
• 제29권3호
• /
• pp.499-512
• /
• 2022

This work proposes a novel contactless vibration damping and thermal isolation tripod platform based on Superconducting Magnetic Levitation (SML). This prototype is suitable for cryogenic environments, where classical passive, semi active and active vibration isolation techniques may present tribological problems due to the low temperatures and/or cannot guarantee an enough thermal isolation. The levitating platform consists of a Superconducting Magnetic Levitation (SML) with inherent passive static stabilization. In addition, the use of Operational Modal Analysis (OMA) technique is proposed to characterize the transmissibility function from the baseplate to the platform. The OMA is based on the Stochastic Subspace Identification (SSI) by using the Expectation Maximization (EM) algorithm. This paper contributes to the use of SSI-EM for SML applications by proposing a step-by-step experimental methodology to process the measured data, which are obtained with different unknown excitations: ambient excitation and impulse excitation. Thus, the performance of SSI-EM for SML applications can be improved, providing a good estimation of the natural frequency and damping ratio without any controlled excitation, which is the main obstacle to use an experimental modal analysis in cryogenic environments. The dynamic response of the 510 g levitating platform has been characterized by means of OMA in a cryogenic, 77 K, and high vacuum, 1E-5 mbar, environment. The measured vertical and radial stiffness are 9872.4 N/m and 21329 N/m, respectively, whilst the measured vertical and radial damping values are 0.5278 Nm/s and 0.8938 Nm/s. The first natural frequency in vertical direction has been identified to be 27.39 Hz, whilst a value of 40.26 Hz was identified for the radial direction. The determined damping values for both modes are 0.46% and 0.53%, respectively.

• Geomechanics and Engineering
• /
• 제36권6호
• /
• pp.563-573
• /
• 2024

In this study, various countermeasures used to mitigate tunnel deformations due to nearby multi-propped basement excavation in soft clay are explored by three-dimensional numerical analyses. Field measurements are used to calibrate the numerical model and model parameters. Since concrete slabs can constrain soil and retaining wall movements, tunnel movements reach the maximum value when soils are excavated to the formation level of basement. Deformation shapes of an existing tunnel due to adjacent basement excavation are greatly affected by relative position between tunnel and basement. When the tunnel is located above or far below the formation level of basement, it elongates downward-toward or upward-toward the basement, respectively. It is found that tunnel movements concentrate in a triangular zone with a width of 2 H_e (i.e., final excavation depth) and a depth of 1 D (i.e., tunnel diameter) above or 1 D below the formation level of basement. By increasing retaining wall thickness from 0.4 m to 0.9 m, tunnel movements decrease by up to 56.7%. Moreover, tunnel movements are reduced by up to 80.7% and 61.3%, respectively, when the entire depth and width of soil within basement are reinforced. Installation of isolation wall can greatly reduce tunnel movements due to adjacent basement excavation, especially for tunnel with a shallow burial depth. The effectiveness of isolation wall to reduce tunnel movement is negligible unless the wall reaches the level of tunnel invert.

• Journal of Microbiology and Biotechnology
• /
• 제14권4호
• /
• pp.730-736
• /
• 2004

This study aims at characterizing the bacteriophages isolated from activated sludge performing enhanced biological phosphorous removal (EBPR) to understand the interactions between the phage-host system and bacterial community. Sixteen bacterial isolates (E1-E16) were isolated as host bacterial strains from EBPR activated sludge for phage isolation. Forty bacteriophages based on their plaque sizes (2 plaques on E4, 4 on E8, 11 on E10, 5 on E14, 18 on E16) were obtained from filtered supernatant of the EBPR activated sludge. Each bacteriophage did not make any plaque on bacterial strains tested in this study except on its own host bacterial strain, respectively, indicating that the bacteriophages are with narrow host specificity. However, fourteen of the forty bacteriophages obtained in this study lost their virulent ability even on their own host bacteria. All of the lytic phages showed similar one-step growth patterns and had long latent period (about 9 hours) to reproduce their phage particles in their host bacterial cells. On the other hand, their probable burst sizes (6 to 48 per host cell) were large enough to actively lyse their host bacterial cells. Therefore, it could be implied that bacteriophages are also important members of the microbial community in EBPR activated sludge, and lytic phages directly decrease the population size of their host bacterial groups in EBPR activated sludge by lysis.

• 한국동물위생학회지
• /
• 제36권2호
• /
• pp.111-119
• /
• 2013

The aim of this study was to investigate the isolation frequency and antimicrobial resistance of Escherichia coli (E. coli) and Enterococcus spp. from domestic beef and pork on sale in Seoul, Korea. A total of 106 (10.4%) E. coli and 114 (11.2%) Enterococcus spp. from 635 domestic beef and 381 pork samples were isolated and examined for susceptibility to 15 and 11 antimicrobial agents, respectively. The most frequent antimicrobial resistance observed in E. coli isolates was to ampicillin (38.6%), followed by streptocmycin (34.9%) and tetracycline (32.0%). The most frequent antimicrobial resistance in E. faecium isolates was to erythromycin (53.8%) and rifampin (46.1%), and in E. faecalis isolates was to tetracycline (55.7%) and rifampin (55.0%). Among the isolates, multi-drug resistant (MDR) E. coli and Enterococcus spp. strains showing resistances to more than two antimicrobial agents tested were 10.4% and 11.2%, respectively. As a result, appropriate protocols for antimicrobial agents and strategies to reduce antimicrobial resistance will be needed in future.