• 한국생산제조학회지
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• 제20권1호
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• pp.40-46
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• 2011

This paper is to investigate the effects of the asymmetrical support stiffness on the stability of a supercritical driveshaft with asymmetrical shaft stiffness and anisotropic bearings. The equations of motion is derived for a system including a rigid disk, a massless flexible asymmetric shaft, anisotropic bearings and a support beam. The Floquet theory is applied to perform the stability analysis with the variation of the support stiffness, the shaft asymmetry, the shaft damping and the shaft speed. The results show that the asymmetric support stiffness is closely related to the stability caused by primary resonance as well as the supercritical operation. First, the stiffness variation can stabilize the system around primary resonance by weakening the parametric resonance from the shaft asymmetry. Second, it also improve the stability characteristics at a supercritical operation when the support stiffness is not so high relative to the shaft stiffness.

• 한국추진공학회지
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• 제16권1호
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• pp.79-85
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• 2012

본 조사에서는 주로 비 축대칭 스피닝, 열처리와 스피닝, 그리고 자유 맨드릴 스피닝 등에 대한 신기술을 동향을 문헌을 통하여 조사하였다. 기존의 재래식, 전단, 튜브 스피닝은 모두 축대칭 맨드릴(제품의 최종 제품의 내경과 같은)을 사용하여 가공하여 왔으나, 신 기법에서는 비 축대칭 맨드릴이나, 맨드릴이 없이, 또 열처리를 동반한 스피닝 공법이 시도되고 있다.

• Journal of Power Electronics
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• 제7권1호
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• pp.21-27
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• 2007

This paper investigates a PID fuzzy controller for output voltage regulation of a current-doubler-rectified asymmetric half-bridge (CDRAHB) DC/DC converter. The controller is a PD-type fuzzy controller in parallel with a linear integral controller. The PD type fuzzy controller is for providing the varying gain at the different operating conditions to regulate the output voltage. The linear integral controller is for removing the steady-state error of the output voltage. In order to show the outstanding dynamic characteristics of the proposed controller, PSIM simulation studies are carried out and compared to the results for which the conventional loop gain design method is used.

• 대한화학회지
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• 제57권5호
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• pp.591-598
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• 2013

A series of chiral prolinamide compounds with pyridine-2, 6-dicarboxylic acid moieties derived from L-proline have been designed and synthesized, their catalytic properties for direct asymmetric aldol reactions were also studied in this article. These catalysts gave the aldol product in high yield (87%) and high enantioselectivity, up to 85%, of the anti-structure at room temperature but gave disappointing results at a lower temperature or when additive was added. Conditions, including solvents, temperature and additives were screened for the reactions. Moreover, the influence of presence of water on yield and stereoselectivity was also discussed.

• 생명과학회지
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• 제13권6호
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• pp.794-798
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• 2003

라세믹 phenyl oxirane 기질에 대한 asymmetric biohydrolysis 활성이 우수한 Rhodosporidium toruloides SJ-4를 생촉매로 이용하여 입체선택적 가수분해 반응을 통해 라세믹 phenyl oxirane 기질로부터 광학활성 (S)-phenyl oxirane를 회분식으로 생산하는 실험을 수행하였다. (R)-phenyl oxirane 이성질체에 대한 초기 가수분해 속도에 영향을 주는 실험인자들인 pH, 반응온도, DMSO cosolvent 첨가량 등에 대해 중심합성계획법을 이용한 반응표면 분석을 통해 가수분해반응 속도를 향상시킬 수 있는 최적 반응조건을 결정하였다. pH 7.4, 반응온도 34℃ 및 DMSO 첨가량 2.3%(v/v)의 조건에서 라세믹 기질 초기 농도 100mM로부터 약 10시간 정도의 반응을 통해 ee 값이 100%인 광학적으로 순수한 (S)-phenyl oxirane를 24% 정도 (이론수율 = 50%)의 높은 수율로 얻을 수 있었다. ^u Batch production of (S)-phenyl oxirane was investigated using epoxide hydrolase activity of Rhodosporidium toruloides SJ-4. Effect of reaction condition of asymmetric biohydrolysis of racemic phenyl oxirane was analyzed and optimized by response surface methodology. The optimal conditions of pH, temperature and DMSO cosolvent ratio were 7.4, 34 ℃, and 2.3%(v/v), respectively. The final yield was enhanced up to 67%, and reaction times required to reach 99% ee (enatiomeric excess) decreased down to 50% by response surface methodology Enantiopure (S)-phenyl oxirane with 100% enantiopurity and 24% yield (theoretical yield = 50%) was obtained from racemic substrate.

• Structural Engineering and Mechanics
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• 제63권3호
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• pp.281-292
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• 2017

Architecture constraints in buildings may typically cause irregularities in the distribution of stiffness and mass and consequently causes non-compliance of centers of mass, stiffness and strength. Such buildings are known as asymmetric buildings the distribution of strength and stiffness is one of whose main challenges. This distribution is more complicated for concrete buildings with RC shear walls in which stiffness and strength are interdependent parameters. The flexibility under the foundation is another subject that can affect this distribution due to the variation of dynamic properties of the structure and its constituting elements. In this paper, it is attempted to achieve an appropriate distribution pattern by expressing the effects of foundation flexibility on the seismic demand of concrete shear walls and also evaluate the effects of this issue on strength and stiffness distribution among lateral force resistant elements. In order to understand the importance of flexibility in strength and stiffness distribution for an asymmetric building in different conditions of under-foundation flexibility, the assigned value to each of the walls is numerically calculated and eventually a procedure for strength and stiffness distribution dependencies on flexibility is provided.

• 한국전산유체공학회지
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• 제11권3호
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• pp.22-27
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• 2006

Flow around a guided missile in high maneuver, i.e. at a high angle of attack, shows complex phenomena. It is well known that even in geometrically symmetric conditions the flow around a missile at high angles of attack can generate unexpected large side forces and yaw moments due to asymmetric vortices. In this paper, a CFD code (FLUENT) based on the Navier-Stokes equations was used for the numerical analysis to find a suitable numerical mechanism for generation of asymmetric vortices. It is shown that a numerical technique of applying different surface roughness to a specific area of the missile nose surface gives the best fit in comparison with the experimental results. In addition, a numerical investigation of variations of side forces and pressure distributions with angle of attack and roll angle was conducted for the purpose of identifying the source of vortex asymmetries.

• 한국대기환경학회지
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• 제19권5호
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• pp.551-560
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• 2003

Particle deposition in human lungs was investigated theoretically by using asymmetric five-lobe lung model. The volumes of each of the five lobes were different, thereby forming an asymmetric lung structure. The tidal volume and flow rate of each lobe were scaled according to lobar volume. The total and regional deposition with various breathing patterns were calculated by means of tracking volume segments and accounting for particle loss during inhalation and exhalation. The deposition fractions were obtained for each airway generation and lung lobe, and dominant deposition mechanisms were investigated for different size particles. Results show that the tidal volume and flow rate have a characteristic influence on particle deposition. The total deposition fraction increases with an increase in tidal volume for all particle sizes. However, flow rate has dichotomous effects: a higher flow rate results in a sharp increase in deposition for large size particles, but decreases deposition for small size particles. Deposition distribution within the lung shifts proximally with higher flow rate whereas deposition peak shifts to the deeper lung region with larger tidal volume. Deposition fraction in each lobe was proportional to its volume. Among the three main deposition mechanisms, diffusion was dominant for particles < 0.5 ${\mu}{\textrm}{m}$ whereas sedimentation and impaction were most influential for larger size particles. Impaction was particularly dominant for particles> 8 ${\mu}{\textrm}{m}$. The results may prove to be useful for estimating deposition dose of inhaled pollutant particles at various breathing conditions.

• Journal of Contemporary Eastern Asia
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• 제20권2호
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• pp.259-277
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• 2021

This article investigates the geopolitics of the energy transition era, concentrating on China's solar photovoltaic (PV) industry. Authors have noted that the rise of renewables is changing the geopolitical landscape of world energy systems, but these new energy sources carry their own technical characteristics and geopolitical implications. Bearing this in mind, this research answers the questions: What are the structural factors that facilitate China's use of renewable energy to achieve political goals, and what are their implications? In order to analyze the data, I devise an analytical framework based on the energy statecraft literature and contrast rival explanations, particularly the "prosumer theory" and the premise of less geopolitical interdependence in a renewable-centered world. I show that asymmetric interdependence in the solar PV sector is already a reality. China's solar PV industry is a case that suffices all conditions (centrality in industrial capacity, market share, and companies' compliance, but to a lesser extent in critical materials and technological endowments) in the solar PV sector to devise effective strategies aimed at reaping benefits out of its asymmetric interdependence with the rest of the world.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1994년도 춘계공동학술대회논문집; 창원대학교; 08월 09일 Apr. 1994
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• pp.741-741
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• 1994