• Earthquakes and Structures
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• 제7권6호
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• pp.955-967
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• 2014

Storage racks are used worldwide in industries and commercial outlets due to the advantage of lighter, faster erection and easy alteration of pallet level as required. The studies to understand the behaviour of cold formed steel pallet racks, under seismic action is one of the emerging area of research. The rack consists of perforated uprights and beams with hook-in end connector, which enables the floor height adjustments. The dynamic characteristics of these racks are not well established. This paper presents the dynamic characteristics of 3-D single bay two storey pallet rack system with hook-in end connectors, which is tested on shake table. The sweep sine test and El Centro earthquake acceleration is used to evaluate the seismic performance of the cold formed steel pallet racks. Also an attempt is made to evaluate the realistic dynamic characteristics by using STAAD Pro software. Modal analysis is performed by incorporating the effective moment of inertia of the upright, which considers the effect of presence of perforations and rotational stiffness of the beam-to-upright connection to determine the realistic fundamental frequency of pallet racks, which is required for carrying out the seismic design. Finite element model of the perforated upright section has been developed as a cantilever beam through which effective moment of inertia is evaluated. The stiffness of the hook-in connector is taken from the previous study by Prabha et al. (2010). The results from modal analysis are in good agreement with the respective experimental results.

• 대한정형도수물리치료학회지
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• 제29권1호
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• pp.41-52
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• 2023

Background: Bulgarian split squat (BSS) is beneficial to improve dynamic balance ability and muscle activity of lower extremities, however its effects have not been fully investigated. Therefore, this study aimed to compare changes in dynamic balance ability and muscle properties according to various modifications of BSS exercises. Methods: Thirty healthy male volunteers participated in this study, and they were randomly divided into three different groups. The subjects performed the BSS exercise either on a stable surface with the eyes opened (n=10) or eyes closed (n=10), and on an unstable support plane with eyes opened (n=10) conditions, respectively. Dynamic balance ability was measured via Biodex balance system under the eyes-opened and closed conditions. Additionally, muscle properties of the rectus femoris (RF), vastus medialis (VM) and vastus lateralis (VL) were evaluated. Results: Dynamic balance ability did not show the significant differences among the groups that performed the BSS exercises. However, in the Unstable group, there were significant differences in the overall stability index and anterior posterior stability index under the eyes-closed condition between pre-exercise and post-exercise. In comparison of muscle properties according to the groups, RF muscle showed a significant difference in amount of change of elasticity (p=.038). Additionally, there were significant changes in post measurements of VM muscle tone (p=.016), stiffness (p=.012) and elasticity (p=.002). VL muscle, however had no significant differences in muscle properties. Conclusion: These results indicate that BSS exercises could induce the alteration of RF and VM muscle properties, in particular VM muscle which is susceptible to weakness. Thus, BSS could be applied in various ways as an effective rehabilitation exercise.

• 한국기계가공학회지
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• 제15권3호
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• pp.122-129
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• 2016

In modern industries, in whichwhere high productivity is one of the most important concerns, machine tools are facing difficulties to satisfy the high high-speed operation, while and at the same time achieve the precision machining. Generally, the vibrations of the structure increase proportionally to the square of the operating speed so that the precision machining is severely damaged with increased speed. which is a must for the high productivity. Therefore, the suppression of the structural vibrations of the machine tools is the a major concern in the machine tool industry in order to achieve the high productivity and the precision machining simultaneously. In this study, the dynamic properties of a machining center structure were analyzed through the experiment and the computer simulations, and furthermore the results from those were compared to confirm the validity of the simulation model. The design alterations were deduced from the analysis and applied to the simulation model to investigate the effects of those alterations to suppress the vibrations of the machine. The result shows that the relatively simple design alterations, without redesigning the main structure of the machine, can suppress the vibrations effectively.

• 한국터널지하공간학회 논문집
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• 제6권1호
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• pp.41-50
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• 2004

본 논문에서는 기존댐 인접지에 터널구조물을 건설하기 위한 발파시, 폭괴하중으로 인한 지반진통이 댐 제체와 간극수암에 마치는 영향을 고찰하였다. 댐의 안정성 검토는 발파시 발생하는 코어부의 최대입자속도 (Peak Particle Velocity)를 계산하여 수행하였다. 간극수와 지반진동간의 상호 연계해석을 위하여 댐 제체에 대한 정상상태 흐름해석을 수행하여 간극수압 분포를 파악하고, 유발된 과잉간극수암 및 유효응력분포로 발파하중이 인접지반에 미치는 영향을 분석하였다. 또한 발파와 같은 급속하중 재하 후 과잉간극수압의 증가 및 소산현상 해석을 위하여 Finn & Byrne Model을 적용하여 하중재하 전후의 유효응력 변화양상을 검토하였다.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3385-3390
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• 2010

$Li^+$ ion complex of azacrown ether with restricted motion of freedom and pseudo-bilateral symmetry was studied by infrared spectroscopy, which has shown simplified and broadened vibrational features. The C=O and N-H stretching bands, in particular, shows anomalous broadening nearly ${\sim}50\;cm^{-1}$. The density functional calculation at the level of BP86/6-31+$G^{**}$ shows that $Li^+$ ion is trapped and rather free to move around inside the cavity, as much as about $0.70\;{\AA}$. Through the relocation of $Li^+$ ion inside the cavity, the conformational changes would occur rapidly in its symmetry $C_1\;{\rightleftarrows}\;C_2\;{\rightleftarrows}\;C_1$$. The potential barrier was obtained to be merely ~2.2 kJ/mol for $C_1\;{\rightarrow}\;C_2$. During this conformational alteration, the amide backbone twists concurrently its dihedral angle side to side about up to ${\pm}3$ degree. Selected vibrational modes were interpreted in terms of the force constant variations of local symmetry coordinates between conformations in the framework of $C_1\;{\rightleftarrows}\;C_2\;{\rightleftarrows}\;C_1$.

• 반도체디스플레이기술학회지
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• 제16권1호
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• pp.34-39
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• 2017

Semiconductor is one of the most internationally competitive areas among domestic industries, the major concern of which is the stability of the wafer manufacturing processes. The first process for the manufacturing of the semiconductor wafers is the ingot growing. The vibrations are supposed to be the most important factors for the ingot quality. In order to maintain the ingot quality, the growers have the automatic shut-down equipments which are activated by vibrations, and are sensitive enough to react to the earthquakes generated in Japan. In this study, the structure of an ingot grower was analyzed through experiments and computer simulations, and further the effects of design alterations to suppress the vibrations have been investigated. The final result shows that the vibrations can be reduced substantially to improve the stability of the structure.

• 한국발생생물학회지:발생과생식
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• 제13권1호
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• pp.13-23
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• 2009

최근에 이루어진 세포생물학적, 유전학적 연구들을 통하여 미토콘드리아의 구조 변화가 매우 역동적이며, dynamin- related protein(DRP)와 같은 다양한 단백질에 의해 조절된다는 것이 알려지게 되었다. 미토콘드리아가 ATP 합성을 통한 세포내 신진대사에 관여하며, 소포체와 상호작용을 통하여 칼슘 이온 농도의 항상성 유지, 그리고 세포 사멸에서 중요한 역할을 한다는 사실을 고려해 볼 때, 미토콘드리아 구조 역동성 조절은 정상적인 세포의 성장과 항상성 유지와 매우 밀접한 관계에 있다. 이러한 점에서, 미토콘드리아의 구조 역동성 변화가 신경세포의 발달에 큰 영향을 줄 것으로 생각된다. 이 논문에서는 미토콘드리아의 구조 역동성을 조절하는 단백질들을 소개하고, 신경세포의 발달과정에서 미토콘드리아의 구조 역동성 조절의 중요성에 대하여 전망하고자 한다.

• Current Optics and Photonics
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• 제5권4호
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• pp.351-361
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• 2021

Speckle imaging is capable of dynamic data acquisition at high spatiotemporal resolution, and has played a vital role in the functional study of biological specimens. The presence of various optical scatterers within the tissue causes alteration of speckle contrast. Thus structures like blood vessels can be delineated and quantified. Although laser speckle imaging is frequently used, an optimization process to ensure the maximum speckle contrast has not been available. In this respect, we here report an experimental procedure to optimize speckle contrast via applying different combinations of varying polarization of the illuminating laser light and multiple analyzer angles. Specifically, samples were illuminated by the p-polarization, 45°-polarization, and s-polarization of the incident laser, and speckle images were recorded without and with the analyzer rotated from 0° to 180° (Δ = 30°). Following the baseline imaging of a solid diffuser and a fixed brain sample, laser speckle contrast imaging (LSCI) was successfully performed to visualize in vivo mouse-brain blood flow. For oblique laser illumination, the maximum contrast achieved with p-polarized and s-polarized light was perpendicular to the analyzer's axis. This study demonstrates the optimization process for maximizing the speckle contrast, which can improve blood-flow estimation in vivo.

• 반도체디스플레이기술학회지
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• 제17권3호
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• pp.59-64
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• 2018

In recent years, the solar cell market has steadily grown with the demand for new energies. And wire sawing is one of the most critical processes in manufacturing solar cell wafer which is supposed to affect the breakage of wafers most during the process and afterwards. Generally, the defects of the wafers are generated from the structural vibrations of the machine. In the sawing process, the vibrations cause unnecessary normal stress on the cut surface of wafers, and eventually create the surface damage or leave the residual stress. In this study, the dynamic properties of a wire saw have been analyzed through the frequency response test and the computer simulation. And the effects of the design alterations have been investigated to stabilize the machine structure and further to reduce the vibrations. The result shows that relatively simple design alterations of supporting structure without any change of major parts of the machine can suppress the vibrations of the machine effectively.

• 융합보안논문지
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• 제18권3호
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• pp.27-35
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• 2018

공인인증서는 개인을 증명하거나 통신간의 위변조 등을 방지하기 위하여 공인인증기관에서 발행하는 전자화된 정보로써 사이버 상의 인감도장이라 할 수 있다. 공인인증서는 암호화 된 파일의 형태로 PC 및 스마트폰에 저장되어 인터넷뱅킹 및 스마트뱅킹 서비스를 이용할 때 개인을 증명하기 위해 사용하기 때문에 외부로 유출될 경우 위험할 수 있다. 급증하는 안드로이드 기반 악성 어플리케이션 중 파일로 존재하는 공인인증서와 개인정보 등을 외부의 서버에 전송하는 악성 어플리케이션 또한 발견되고 있다. 본 논문은 공인인증서 탈취 악성코드를 사전에 판단하여 차단하기 위해 안드로이드 기반 동적 분석 도구인 DroidBox를 이용하여 공인인증서 외부 유출행위 여부를 판단하는 방안을 제안한다.