• 소음진동
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• 제7권1호
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• pp.71-79
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• 1997

The objective of this study is to investigate experimentally the effect of surface conditions of the plate on the impinging jet noise. The experimental results about the spectrum, the sound pressure level and the directivity are pressented and discussed in relation with the surface conditions. Regardless of the surface conditions, the pure tones of high level are generated at the same frequency band and the overall sound power level of impinging jets is much higher than that of the free jet. However, the velocity dependence of the sound pressure level and the directivity are different between smooth surfaces and rough surfaces. The dependence of sound pressure level on the jet velocity shows that the smooth surface generates quadrupole-type sound like free jets. However, the perforated or the rough surface radiates sound power exactly proportional to the sixth power of the jet velocity, indicating that the source is fixed dipole type. The directivities of 1/3 octave band sound pressure level for both the free and impinging jet show the peak directivity at 115$^\circ$ upstream, probably due to the refraction associated with velocity gradient.

• 한국지진공학회논문집
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• 제5권3호
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• pp.29-36
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• 2001

국내 일반 국도상의 교량을 분석한 결과 형상비가 2.5 내외로서 휨-전단 파괴 거동이 예측되는 교각이 다수 존재하는 것으로 나타났으나 기존의 교각 내진 특성 연구는 주로 휨 파괴 거동을 보이는 교각에 대해 수행되어 왔다. 본 연구에서는 휨-전단 복합모드가 작용하여 파괴에 이를 가능성이 많은 형상비 2.5 내외인 기존 교각을 대상모델로 선정하고 실물크기 모형 및 축소모형 시험체를 제작하여 준정적 실험(quasi static test)을 수행하였다. 실험결과로부터 상사효과(scale effect)가 교각 내진 성능평가에 미치는 영향을 분석하였고, 또한 비내진 상세인 실험대상 교량에 대해 역량스펙트럼법을 이용하여 내진성능을 평가하였다.

• Archives of Pharmacal Research
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• 제21권3호
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• pp.291-297
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• 1998

Cop protein has been overexpressed in Escherichia coli using a T7 RNA polymerase system. Purification to apparent homogeneity was achieved by the sequential chromatography on ion exchange, affinity chromatography, and reverse phase high performance liquid chromatography system. The molecular weight of the purified Cop was estimated as 6.1 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). But the molecular mass of the native state Cop was shown to be 19 kDa by an analytical high performance size exclusion chromatography, suggesting a trimer-like structure in 50 mM Tris-HCI buffer (pH 7.5) containing 100 mM NaCl. Cop protein Was calculated to contain $39.1% {\alpha}-helix, 16.8% {\beta}-sheet$, 17.4% turn, and 26.8% random structure. The DNA binding property of Cop protein expressed in E. coli Was preserved during the expression and purification process. The isoelectric point of Cop was determined to be 9.0. The results of amino acid composition analysis and N-terminal amino acid sequencing of Cop showed that it has the same amino acid composition and N-terminal amino acid sequence as those deduced from its DNA sequence analysis, except for the partial removal of N-terminal methionine residue by methionyl-aminopeptidase in E. coli.

• Tribology and Lubricants
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• 제10권4호
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• pp.43-50
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• 1994

In order to elucidate the effects of co-existing additives (S$_{8}$, TBP: Tri butyl phosphate, ZnDTP: Zinc-dialkyl dithiophosphate) and the role of reacted surface film on the friction behavior of MoDTP (molybdenum dialkyl dithiophosphate), a friction experiment using a dual circular pipe edge surface type friction tester and XPS (X-ray photoelectronic spectrum) surface analysis were conducted. Friction reduction with MoDTP lubricant was proved to be greatly influenced by co-existing additive species. It was dependent on the properties of the film formed through the reaction between the additive and the surface. Phosphate film reduced the friction coefficient of MoDTP through suppression of diffusion of Mo compounds towards the metal substrate. On the other hand, sulfate film, which is inherently rich in lattice defects, did not lead to any appreciable friction reduction with MoDTP since the diffusion of the Mo compound towards the metal substrate was not effectively suppressed. With ZnDTP additive, the sulfide film formed through decomposition greatly influenced the lubricating performance of MoDTP. As such, properties of surface films formed from additives were proved to yield significant influence on the lubrication performance of MoDTP.

• Structural Engineering and Mechanics
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• 제64권2호
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• pp.213-223
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• 2017

Bridges are lifeline and integral components of transportation system that are susceptible to seismic actions, their vulnerability assessment is essential for seismic risk assessment and mitigation. The vulnerability assessment of bridges common in Pakistan is very important as it is seismically very active region and the available code for the seismic design of bridges is obsolete. This research presents seismic vulnerability assessment of three real case simply supported multi-span reinforced concrete bridges commonly found in northern Pakistan, having one, two and three bents with circular piers. The vulnerability assessment is carried through the non-linear dynamic time history analyses for the derivation of fragility curves. Finite element based numerical models of the bridges were developed in MIDAS CIVIL (2015) and analyzed through with non-linear dynamic and incremental dynamic analyses, using a suite of bridge-specific natural spectrum compatible ground motion records. Seismic responses of shear key, bearing pad, expansion joint and pier components of each bridges were recorded during analysis and retrieved for performance based analysis. Fragility curves were developed for the bearing pads, shear key, expansion joint and pier of the bridges that first reach ultimate limit state. Dynamic analysis and the derived fragility curves show that ultimate limit state of bearing pads, shear keys and expansion joints of the bridges exceed first, followed by the piers ultimate limit state for all the three bridges. Mean collapse capacities computed for all the components indicated that bearing pads, expansion joints, and shear keys exceed the ultimate limit state at lowest seismic intensities.

• Earthquakes and Structures
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• 제15권4호
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• pp.411-417
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• 2018

To solve the seismic response problem of a vertical floating roof tank with base isolation, the floating roof is assumed to experience homogeneous rigid circular plate vibration, where the wave height of the vibration is linearly distributed along the radius, starting from the theory of fluid velocity potential; the potential function of the liquid movement and the corresponding theoretical expression of the base shear, overturning the moment, are then established. According to the equivalent principle of the shear and moment, a simplified mechanical model of a base isolation tank with a swinging effect is established, along with a motion equation of a vertical storage tank isolation system that considers the swinging effect based on the energy principle. At the same time, taking a 150,000 m 3 large-scale storage tank as an example, a numerical analysis of the dampening effect was conducted using a vibration mode decomposition response spectrum method, and a comparative analysis with a simplified mechanical model with no swinging effect was applied.

• Journal of Ginseng Research
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• 제10권2호
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• pp.209-217
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• 1986

Yeast alcohol dehydrogenates and ginseng saponin interaction has been investigated to understand the non-specific enzyme stimulating effect of the saponin of Panax ginseng C.A. Meyer. It was confirmed that several amphiphiles such as sodium dodecyl sulfate(SDS), Triton X-100, sodium taurodeoxycholate (Na-TDC) as well as ginseng saponin mixture and purified ginseng glycosides lowered Km values of yeast alcohol dehydrogenase (ADH) for ethanol and NAD in the presence of the above amphiphiles suggesting that the surface activity of the amphiphiles might play a significant role in the ADH catalyzed reactions. Conformational change of yeast alcohol dehydrogenase in the presence of the above amphiphiles at their optimal concentration for the maximum activity was studied. Circular dichroism (C.D) spectrum of yeast ADH showed that the conformational change of the enzyme occurred in the presence of above amphiphiles. Fluorescence data also showed that the hydrophobic area increased in the presence of above amphiphiles. Examination of the interaction between ADH and ginseng saponin using radioactive saponin showed that there might be a very weak interaction between them. From the above results, it was concluded that the non-specific enzyme stimulating effect of the saponin might be due to the change of polarity of the enzyme solution in the presence of the saponin.

• Macromolecular Research
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• 제12권5호
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• pp.501-506
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• 2004

We have investigated the spectral properties of DNA, including its electric absorption, circular and linear dichroism (CD and LD), and fluorescence emission, in the DNA-linear polyethyleneimine (LPEI) and DNA-branched polyethyleneimine (BPEI) complexes at various polymer concentrations. The spectral properties of both complexes are similar. We observed a relatively moderate change in the absorption and CD spectra at low amine/DNA phosphate (NIP) ratios (< 0.5), followed by a drastic collapse within the N/P range from 0.8 and 1.0. The absorption and CD spectra recovered as the N/P ratio increased to ca. 1.2. In contrast, the LD and emission of ethidium intercalated between the DNA bases decreased almost linearly at N/P ratios between 0.0 and 1.0. These spectra never recovered at higher N/P ratios. We believe that the moderate changes in the spectrum at low N/P ratios occurred because of electrostatic interactions between DNA and BPEI, while the collapsed spectra at N/P ratios between 0.5 and 1.5 occurred because of condensation/aggregation of the DNA. Considering the structure of the polymers, we suggest that the secondary amino group of LPEI and all three amino groups of BPEI are equally involved in DNA condensation.

• BMB Reports
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• 제35권2호
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• pp.178-185
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• 2002

The Arabidopsis thaliana S-Adenosylmethionine decarboxylase (AdoMetDC) cDNA ($GenBank^{TM}$ U63633) was cloned. Site-specific mutagenesis was performed to introduce mutations at the conserved cysteine $Cys^{50}$, $Cys^{83}$, and $Cys^{230}$, and $lys^{81}$ residues. In accordance with the human AdoMetDC, the C50A and C230A mutagenesis had minimal effect on catalytic activity, which was further supported by DTNB-mediated inactivation and reactivation. However, unlike the human AdoMetDC, the $Cys^{50}$ and $Cys^{230}$ mutants were much more thermally unstable than the wild type and other mutant AdoMetDC, suggesting the structural significance of cysteines. Furthermore, according to a circular dichroism spectrum analysis, the $Cys^{50}$ and $Cys^{230}$ mutants show a higher a-helix content and lower coiled-coil content when compared to that of wild type and the other mutant AdoMetDC. Also, the three-dimensional structure of Arabidopsis thaliana AdoMetDC could further support all of the data presented here. Summarily, we suggest that the $Cys^{50}$ and $Cys^{230}$ residues are structurally important.

• 한국전자파학회논문지
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• 제11권8호
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• pp.1414-1419
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• 2000

본 논문에서는 임의 배열 안테나에 입사하는 다중 협대역 인코히런트 신호를 분리 추정하기 위한 분해능 향상 알고리즘을 제안한다. 도래각 추정 알고리즘의 분해능은 배열 안테나 개구면의 크기에 좌우되므로 분해능을 좋게 하기 위해서는 개구면을 크게 해야 한다. 그러나 실환경하에서 배열 안테나의 개구면 크기를 증기시키는 것은 비 실용적이므로 배열 안테나의 센서간격을 가상적으로 확장시킴으로서 개구면의 크기를 증가시키고 적절한 변환 행렬을 사용하여 이 가상 배열 안테나의 스티어링 행렬을 구하는 방안을 제시한다. 시뮬레이션을 통하여 비교분석한 결과 등간격 협대역 인코히런트 신호가 원형배열 안테나에 입사되었을 경우에 제안된 방법이 표준 MUSIC보다 뛰어난 분해성능을 보여주었다.