• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집E
• /
• pp.690-695
• /
• 2001

The three-dimensional spatial structures of impeller flow created by a six bladed Rushton turbine have identified based on the volumetric velocity information from multi-plane stereoscopic PIV measurements. A total of 10 planes with 2 mm space with a 50 mm by 64 mm size of the field of view were targeted. To reduce the depth of focus, we adopted an angle offset configuration which satisfied the Scheimpflug condition. The distortion compensation procedure was utilized during the in situ calibration. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D, volumetric velocity fields on a 60 degree sector of a cylindrical ring volume enclosing the turbine blade. Using the equi-vorticity surface rendering, the spatial structure of the trailing vortices was clearly demonstrated. Detail flow characteristics of the radial jet reported in previous studies of mixer flows were easily identified.

• Structural Engineering and Mechanics
• /
• 제65권6호
• /
• pp.741-750
• /
• 2018

The aim of this study was to investigate the mechanical responses of a high-speed railway shield tunnel subjected to impact by a derailed train, with emphasis on the protective effect of the secondary lining. To do so, the extended finite element method was used to develop two numerical models of a shield tunnel including joints and joint bolts, one with a cast-in-situ concrete secondary lining and one without such a lining. The dynamic responses of these models upon impact were analyzed, with particular focus on the distribution and propagation of cracks in the lining structures and the mechanical responses of the joint bolts. The numerical results showed that placing a secondary lining significantly constricted the development of cracking in the segmental lining upon the impact load caused by a derailed train, reduced the internal forces on the joint bolts, and enhanced the safety of the segmental lining structure. The outcomes of this study can provide a numerical reference for optimizing the design of shield tunnels under accidental impact loading conditions.

• 상하수도학회지
• /
• 제29권6호
• /
• pp.685-692
• /
• 2015

The concern over the risk of environmental exposure to brominated phenols has been increased and has led the researchers to focus their attention on the study of bromophenol treatment. In this study, the effects of pH and ferrate(VI) dose on the degradation of 2-bromophenol were investigated. The results indicated that the oxidation of 2-bromophenol by liquid ferrate(VI) was found to be highly sensitive to the pH condition. Furthermore, the highest removal efficiency was observed at the neutral condition with the removal efficiency of 94.2%. In addition, experimental results showed that 2-bromophenol removal efficiency increased with increasing of ferrate dosage. Ferrate(VI) dose of 0.23 mM was sufficient to remove most of the 2-bromophenol with the efficiency of 99.73% and kapp value of $2982M^{-1}s^{-1}$. Seven compounds were identified as the intermediate products by the GC/MS analysis.

• 대한기계학회논문집B
• /
• 제27권6호
• /
• pp.773-780
• /
• 2003

The three-dimensional spatial structures of impeller flow created by a six bladed Rushton turbine have identified based on the volumetric velocity information from multi-plane stereoscopic PIV measurements. A total of 10 planes with 2 mm space and a 50 mm by 64 mm size of the field of view were targeted. To reduce the depth of focus, we adopted an angle offset configuration which satisfied the Scheimpflug condition. The distortion compensation procedure was utilized during the in situ calibration. Phase-locked instantaneous data were ensemble averaged and interpolated in order to obtain mean 3-D. volumetric velocity fields on a 60 degree sector of a cylindrical ring volume enclosing the turbine blade. Using the equi-vorticity surface rendering, the spatial structure of the trailing vortices was clearly demonstrated. Detail flow characteristics of the radial jet reported in previous studies of mixer flows were easily identified.

• 한국입자에어로졸학회지
• /
• 제13권2호
• /
• pp.53-63
• /
• 2017

As semiconductor process was highly integrated, particle contamination became a major issue. Because particle contamination is related with process yields directly, particles with a diameter larger than half pitch of gate should be controlled. PBMS (Particle beam mass spectrometry) is one of powerful nano particle measurement device. It can measure 5~500 nm particles at ~ 100 mtorr condition in real time by in-situ method. However its usage is restricted to research filed only, due to its big device volume and high price. Therefore aperture changeable aerodynamic lenses (ACALs) which can control particle focusing characteristics by changing its aperture diameter was proposed in this study. Unlike conventional aerodynamic lenses which changes particle focusing efficiency when operating condition is changed, ACALs can maintain particle focusing efficiency. Therefore, it can be used for a multi-monitoring system that connects one PBMS and several process chambers, which greatly improves the commercialization possibility of the PBMS. ACALs was designed based on Stokes number and evaluated by numerical method. Numerical analysis results showed aperture diameter changeable aerodynamic lenses can focus 5 to 100 nm standard particles at 0.1 to 10 torr upstream pressure.

• 한국환경복원기술학회지
• /
• 제6권4호
• /
• pp.17-23
• /
• 2003

Restoration ecology is undergoing rapid growth as academic field over the last 15 years. The specification of goals for restoration projects is frequently described as the most important component of a project. The endeavor for universal development of goals for ecological restoration continues to generate many discussion and controversy. I discuss the importance of restoration goals and diverse roots of restoration ecology, and show how the complex lineages within restoration ecology. I review the three major theme that currently are used to develop the restoration goals : restoration of species, restoration of whole ecosystem or landscapes, and the restoration of ecosystem services. Restoration ecology, landscape ecology and conservation biology share goals to conserve biodiversity, but differ in focus of approach. I review the differences among three fields. Conservation biology has been more zoological, more descriptive, and theoretical, and more emphasized the population and genetic research. However, restoration ecology has been more plant ecological, more experimental, and emphasized the community and plant succession. Landscape ecology has emphasized the interaction of ecosystem and dispersal among populations. I suggest the integration of restoration ecology, landscape ecology and conservation biology. For example, conservation biology will contribute to the preservation of original habitats by population study, restoration ecology will contribute to regenerate damaged ecosystem and ex situ preservation, and landscape ecology will contribute to restoration of population and landscape.

• 지구물리와물리탐사
• /
• 제10권4호
• /
• pp.332-344
• /
• 2007

경북 포항 부근에서 지열에너지 개발을 위하여 굴착된 심부 시추공에서 다양한 물리검층을 수행하였다. 물리검층의 주요 목적은 지층층서 해석, 원위치 물성 평가, 대수층 추정 등이다. 물리검층 자료 중에서 자연감마선검층 자료를 시추공 BH-1호공의 코어검층과 비교하여 제3기 반고결 퇴적층 및 백악기 퇴적층과 관입암 등의 지층 층서를 해석하였다. 원위치 지층 물성 대비도표는, 제3기 퇴적층, 백악기 퇴적층과 관입암 등의 지질 구분에 효과적으로 이용되었다. 시추공 BH-4호공의 심도 1981.3 m에서의 온도는 $82.51^{\circ}C$로 측정되었으나 안정된 상태에서 측정한 시추공 BH-2호공의 온도가 시추직후 교란된 상태에서 측정된 온도보다 높았음을 고려할 때, 실제 온도는 이보다 $5{\sim}6^{\circ}C$ 정도 높을 것으로 예상된다. 온도/전기전도도 변화율검층, 암편로그에서 대수층으로 추정되는 구간이 다수 존재하는 것으로 해석되었다.

• 한국지반환경공학회 논문집
• /
• 제9권2호
• /
• pp.39-46
• /
• 2008

개발사업과 산업발달로 인하여 발생되는 유해화학물질과 유류사용량이 늘면서 화학물질과 유류를 저장하는 지하저장탱크에서의 오염물질 유출로 토양 및 지하수 오염이 심각해지고 있다. 또한, 산업지역, 공장지대가 밀집된 매립 지반에서는 투수계수가 낮아 오염물질 추출에 한계가 있다. 이러한 문제해결 방안의 하나로 연약지반 개량공법에서 사용되고 있는 연직배수재를 이용하여 기존의 복원기술인 토양세정공법의 효율을 증진시킨 연직배수시스템에 대한 연구를 수행하였다. 오염된 지반의 복원을 목적으로 사용한 연직배수시스템의 적용성 평가를 위하여 오염토양 복원시 오염지반에 영향을 주는 인자에 대한 유효성 등을 분석하였다. 본 연구에서는 연직배수시스템의 적용성을 위하여 오염토양 복원시 오염지반에 영향을 주는 인자에 대한 공학적 특성을 바탕으로 파일럿 규모의 실내 오염복원 실험을 통한 오염물질의 복원효율 등을 분석하였다. 또한, 염화나트륨을 복원실험의 추적자로 사용하였고, 도출된 결과를 바탕으로 SEEP/W와 CTRAN/W 유한요소해석 프로그램을 이용하여 압력수두와 지속시간에 따른 농도변화, 각각의 지반조건에 대한 복원률의 오염물질 흐름 해석을 통한 유효성을 평가하였다. 결과, 오염지반의 투수계수는 흐름속도와 연직배수재를 통한 추출률과 관계되며, 흐름속도와 추출률은 분산지수에 영향을 미치게 되어 결국 원위치 오염복원 과정시 중요한 역할을 하게 된다.

• 한국환경복원기술학회지
• /
• 제27권2호
• /
• pp.17-28
• /
• 2024

In order to achieve the management goals (30by30) mandated by the Kunming-Montreal Global Biodiversity Framework, this study established the site-level assessment criteria for OECMs, tailored to domestic circumstances using the Delphi analysis. Subsequently, a site-level assessment was conducted on the National Gariwangsan Natural Recreation Forest. As a result of the study, the initial step involved presenting criteria for the site-level assessment of OECMs, with 'consent for the assessment and recognition of OECM by competent and management authority' proposed as a prerequisite. Subsequently, seven evaluation criteria were established, including 'other than a legally protected area', 'spatially separated area with defined boundaries', 'effective in-situ conservation of biodiversity', 'sustainable management based on the competent and management authority', 'long-term sustainability of conservation outcomes', and 'provision of ecosystem services'. The results of applying site-level assessment criteria to the National Gariwangsan Natural Recreation Forest indicate that six criteria were met, while one criterion (sustainable management based on the competent and management authority) requires further improvement. Specifically, the key competent and management authorities for the National Gariwangsan Natural Recreation Forest are the Korea Forest Service and the National Natural Recreation Forest Management Office, with competent and management organizations established. However, the management focus is primarily on providing forest recreation services centered on users and facilities, making it difficult to confirm the long-term biodiversity conservation plans and implementation by the competent and management authorities. Therefore, it is deemed necessary to improve the long-term biodiversity conservation plans and implementation for the recognition of the National Gariwangsan Natural Recreation Forest as an OECM.

• 천문학회보
• /
• 제37권2호
• /
• pp.101.2-101.2
• /
• 2012

Shocks are ubiquitous in astrophysical plasmas: bow shocks are formed by the interaction of solar wind with planetary magnetic fields, and supernova explosions and jets produce shocks in interstellar and intergalactic spaces. The global morphologies of these shocks are usually described by a set of magnetohydrodynamic (MHD) equations which tacitly assumes local thermal equilibrium, and the resulting Rankine-Hugoniot shock jump conditions are applied to obtain the relationship between the upstream and downstream physical quantities. While thermal equilibrium can be achieved easily in collisional fluids, it is generally believed that collisions are infrequent in astrophysical settings. In fact, shock widths are much smaller than collisional mean free paths and a variety of kinetic phenomena are seen at the shock fronts according to in situ observations of planetary shocks. Hence, both the MHD and kinetic equations have been adopted in theoretical and numerical studies to describe different aspects of the physical phenomena associated with astrophysical shocks. In this paper, we present the results of 3D relativistic particle-in-cell (PIC) simulations for ion-electron plasmas, with focus on the shock structures: when a jet propagates into an unmagnetized ambient plasma, a shock forms in the nonlinear stage of the Weibel instability. As the shock shows the structures that resemble those predicted in MHD systems, we compare the results with those predicted in the MHD shocks. We also discuss the thermalization processes of the upstream flows based on the time evolutions of the phase space and the velocity distribution, as well as the wave spectra analyses.