• 한국산학기술학회논문지
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• 제11권4호
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• pp.1325-1332
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• 2010

미세증가감수지수 검사는 감각신경성난청의 세부 병변을 감별하기 위하여 사용되는 누가현상을 판별하는 검사이다. 본 논문은 PC 기반 소프트웨어로 구현한 미세증가감수지수 검사 소프트웨어를 기술한다. 구현된 소프트웨어는 검사자의 검사 참여 유 무에 따라 수동 검사와 자동 검사의 두 가지 모드를 제공함으로써 경제적인 검사가 진행 될 수 있게 한다. 또 필요할 경우에 자동으로 차폐를 수행한다. 그리고 1dB의 순간 상승음에 대한 검사뿐만 아니라 2dB와 5dB 상승음에 대한 검사도 지원함으로써 보다 정확한 검사 결과를 얻을 수 있도록 한다.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.312.3-313
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• 2002

Recently we have reported that various hydroxystilbenes show strong inhibition of human P450 1 activity. A series of synthetic trans-stilbene derivatives were prepared and their inhibitory potentials were evaluated with the bacterial membrane of recombinant human P450 1A1, 1A2 or 1B1 coexpressed with human NADPH-P450 reductase to find new candidates for cancer chemoprevention, Of the compounds tested. SY-021 (3.5-dimethoxyphenyl vinyl thiophene) exhibited a potent inhibition of human P450 181 with an IC$_{50}$ value of 2 nM. SY-021 also showed the inhibitrion of P450 1A1 with IC$_{50}$ value of 61 nM and P450 1A2 with IC$_{50}$ value of 11 nM. SY-021 showed 31-fold selectivity for P450 1B1 over P450 1A1 and 6-fold selectivity for P450 1B1 over 1A2. We have further investigated the inhibition kinetics of P450 1A1. 1A2 and 1B1 by SY-021. The modes of inhibition by SY-021were non-compeitive for all three P450 1 enzymes. Effect of preincubation with NADPH on inhibition of P450 1B1 by SY-021 was determined. These results suggest that SY-021 is one of the mostj potent inhibitor of human P450 1 enzymes and may be considered as a good candidate for a cancer chemopreventive agent in human

• 한국강구조학회 논문집
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• 제13권1호
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• pp.61-69
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• 2001

본 연구에서는 거더와 가로보로 이루어진 패널을 특별 직교 이방성 판이론을 응용하여 해석하였다. 거더와 가로보는 H 형단면을 사용하였으며, 임의의 단면과 지점을 갖고 임의의 하중을 받는 보다 탑의 진동해석 방법이 발표된 바가 있다. 본 논문에서는 특별 직교 이방성 판이론을 강교량에 응용하였으며, 해석한결과를 제시하였다. 이러한 진동 해석을 위하여 처짐의 영향을 고려한 다양한 방법이 검토되었다. 이러한 목적으로 본 논문에서는 유한차분법을 사용하였다. 고유진동수에 대한 $D_{22}$ 탄성계수의 영향을 철저히 검토하였다. 본 연구에서는 제시한 판이론을 수치해석을 해본 결과 빔이론 보다 강성이 2.43배인 것을 알 수 있었다.

• 한국해양학회지
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• 제21권4호
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• pp.245-258
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• 1986

入射長波에 의해 발생하는 강제 副振動 現象을 밝히기 위한 2次元 數値모델을 개발하여 우리나라주요 港灣中 副振動이 가장 빈번히 觀測되는 迎日 과 浦港新項 에 적용하였다. 本 硏究의 結果는 다음과 같다. 1. 數値모델에 의해 구한 硏究 海灣 의 固有週期는 迎日 의 경우 제1固有週期는 약 70분이고, 第2固有週期는 약 25분 이며 浦港新項의 경우 第1固有週期는 약 25분이고, 제 2고유주기는 약 7.5분이다. 이는 理論式 Spectrum 분석, 統計調査에 의해 구한 週期와도 잘 일치함이 確認되었 다. 2. 迎日 第2固有週期와 浦港新項의 第1固有週期는 거의 같다. 그러므로 迎日 내로 25분주기의 長波가 들어올 때 浦港新項내의 海面 副振動은 강하게 增幅될 수 있다.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.29-37
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• 2011

The modal characteristics of a compressor wheel of an automotive turbocharger have been investigated using an experimental method based on an acoustic frequency response function, p/f(${\omega}$), where p is sound pressure radiated from a structure, and f is impact force. First, a well-defined annular disc with narrow radial slots was examined to check whether the vibro-acoustic test could precisely determine natural quencies and vibration modes of structures showing that the vibro-acoustic test proposed in this paper was comparable to the conventional modal test with an accelerometer and the numerical analysis. The conventional method has been found to be inappropriate for compressor wheel because of additional mass due to the accelerometer and additional damping from the accelerometer cable alter the dynamic responses of the wheel blades. odal characteristics of the wheel have been defined using vibro-acoustic test and verified with the results from another conventional method using a laser vibrometer. Natural quencies and mode shapes of a turbocharger wheel, which can't be precisely obtained with onventional method, could be defined accurately without the additional effects from sensor and cable. Proposed method can be applied to small structures where conventional sensors and cables could generate troubles.

• 한국철도학회논문집
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• 제15권5호
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• pp.423-428
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• 2012

철도차량의 속도가 증가함에 따라 레일 불균일에 의한 가진주파수의 상승으로 인하여 철도차량의 동특성을 고려한 승차감 예측기술이 중요해지고 있다. 철도차량의 동특성은 전산 모드해석과 더불어 시험적으로 검증되어야 한다. 본 연구에서는 철도차량 차체 굽힘모드 시험을 고찰하고, 이를 대체할 수 있는 방안을 제시하였다. 이를 위해 우선 차체 크기비를 반영한 평판 시편을 제적하고, 이를 기존 시험규격인 JIS E7105방법과 충격시험을 사용한 결과를 비교하여 충격시험의 타당성을 검증하였다. 또한 전산해석을 통하여 이를 재현하였다. 타당성이 검증된 결과를 바탕으로 현장 굽힘모드 시험을 유압가진 대신 충격시험으로 대체 가능성을 검토하였다.

• Smart Structures and Systems
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• 제21권3호
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• pp.279-286
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• 2018

The free longitudinal vibration of a circular truncated nanocone is investigated based on the nonlocal elasticity theory. Exact analytical formulations for tapered nanostructures are derived and the nonlinear differential governing equation of motion is developed. The nonlocal small scale effect unavailable in classical continuum theory is addressed to reveal the long-range interaction of atoms implicated in nonlocal constitutive relation. Unlike most previous studies applying the truncation method to the infinite higher-order differential equation, this paper aims to consider all higher-order terms to show the overall nonlocality. The explicit solution of nonlocal stress for longitudinal deformation is determined and it is an infinite series incorporating the classical stress derived in classical mechanics of materials and the infinite higher-order derivative of longitudinal displacement. Subsequently, the first three modes natural frequencies are calculated numerically and the significant effects of nonlocal small scale and vertex angle on natural frequencies are examined. The coupling phenomenon of natural frequency is observed and it is induced by the combined effects of nonlocal small scale and vertex angle. The critical value of nonlocal small scale is defined, and after that a new proposal for determining the range of nonlocal small scale is put forward since the principle of choosing the nonlocal small scale is still unclear at present. Additionally, two different types of nonlocal effects, namely the nonlocal stiffness weakening and strengthening, reversed phenomena existing in nanostructures are observed and verified. Hence the opposite nonlocal effects are resolved again clearly. The nano-engineers dealing with a circular truncated nanocone-based sensors and oscillators may benefit from the present work.

• The Journal of Advanced Prosthodontics
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• 제11권3호
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• pp.187-192
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• 2019

PURPOSE. The purpose of this in vitro study was to investigate the fracture loads and modes of failure for the full range of natural teeth under simulated occlusal loading. MATERIALS AND METHODS. One hundred and forty natural teeth were taken from mandibles and maxillas of patients. There were 14 groups of teeth with 10 teeth in each group (5 males and 5 females). Each specimen was embedded in resin and mounted on a positioning jig, with the long axis of the tooth at an inclined angle of 30 degrees. A universal testing machine was used to measure the compression load at which fracture of the tooth specimen occurred; loads were applied on the incisal edge and/or functional cusp. RESULTS. The mean fracture load for the mandibular first premolar was the highest (2002 N) of all the types of teeth, while the mean fracture load for the maxillary first premolar was the lowest (525 N). Mean fracture loads for the mandibular and maxillary incisors, and the first and second maxillary premolars, had significantly lower values compared to the other types of teeth. The mean fracture load for the teeth from males was significantly greater than that for the teeth from females. There was an inverse relationship between age and mean fracture load, in which older teeth had lower fracture loads compared to younger teeth. CONCLUSION. The mean fracture loads for natural teeth were significantly different, with dependence on tooth position and the sex and age of the individual.

• Bulletin of the Korean Chemical Society
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• 제9권6호
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• pp.345-349
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• 1988

The polycrystalline powder of (CaLa) (MgMo)$O_6$ has been prepared at $1350^{\circ}C$ in $H_2/H_2O$ and $N_2$ flowing atmosphere. The powder X-ray diffraction pattern indicates that (CaLa) (MgMo)$O_6$ has a monoclinic perovskite structure with the lattice constants $a_0=b_0=7.901(1){\AA}$, $c =7.875(1){\AA}\;and\;{\gamma}=89^{\circ}$16'(1'), which can be reduced to orthorhombic unit cell, a = 5.551(1) ${\AA}$, b = 5.622(1) ${\AA}$ and c = 7.875(1) ${\AA}$. The infrared spectrum shows two strong absorption bands with their maxima at 590($ν_3$) and 380($ν_4$) cm, which are attributed to $2T_{1u}$ modes indicating the existence of highly charged molybdenum octahedron $MoO_6$ in the crystal lattice. According to the magnetic susceptibility measurement, the compound follows the Curie-Weiss law below room temperature with the effective magnetic moment 1.83(1)$_{{\mu}B}$, which is well consistent with that of spin only value (1.73 $_{\mu}_B$) for $Mo^{5+}$ with $4d^1$-electronic configuration within the limit of experimental error. From the thermogravimetric analysis, it has been confirmed that (CaLa) (MgMo)$O_6$ decomposes gradually into $CaMoO_4,\;MoO_3,\;MgO,\;La_2O_3$ and unidentified phases due to the oxidation of $Mo^{5+}$ to $Mo^{6+}$.

• Wind and Structures
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• 제37권6호
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• pp.445-460
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• 2023

Accurate estimation of modal parameters (i.e., natural frequency, damping ratio) of tall buildings is of great importance to their structural design, structural health monitoring, vibration control, and state assessment. Based on the combination of variational mode decomposition, smoothed discrete energy separation algorithm-1, and Half-cycle energy operator (VMD-SH), this paper presents a method for structural modal parameter estimation. The variational mode decomposition is proved to be effective and reliable for decomposing the mixed-signal with low frequencies and damping ratios, and the validity of both smoothed discrete energy separation algorithm-1 and Half-cycle energy operator in the modal identification of a single modal system is verified. By incorporating these techniques, the VMD-SH method is able to accurately identify and extract the various modes present in a signal, providing improved insights into its underlying structure and behavior. Subsequently, a numerical study of a four-story frame structure is conducted using the Newmark-β method, and it is found that the relative errors of natural frequency and damping ratio estimated by the presented method are much smaller than those by traditional methods, validating the effectiveness and accuracy of the combined method for the modal identification of the multi-modal system. Furthermore, the presented method is employed to estimate modal parameters of a full-scale tall building utilizing acceleration responses. The identified results verify the applicability and accuracy of the presented VMD-SH method in field measurements. The study demonstrates the effectiveness and robustness of the proposed VMD-SH method in accurately estimating modal parameters of tall buildings from acceleration response data.