• Title/Summary/Keyword: Mechanisms

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Strategy and progress to establish a micro-assembly technology archive considering the mechanisms of joining- and manipulating- processes

  • Takahashi, Kunio
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.367-369
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    • 2005
  • For the purpose of the optimization or the break through of production processes, it is essential to understand or theoretically interpret dominant mechanisms of the processes, and further more, archive them. and utilize them combining some of them which are needed. Especially in the technology for micro- or nano-scaled objects, adhesion phenomenon is no more negligible, because the adhesion force is proportional to the size of objects meanwhile gravity force is proportional to the third power of it. Author has been working about the mechanisms for micro-assembly processes, which include joining processes and manipulation processes. In the present paper, the strategy and the progress to establish the micro-assembly technology archive are introduced. Some of the mechanisms are introduced with related basic approaches to the adhesion phenomena. Also it will be expressed that our data base project for the surface and interfacial energies is strongly related to these basic approaches.

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Design of a Change Management Framework for Group Collaborative Systems (그룹협동 시스템을 위한 변화관리 모형의 설계)

  • 허순영
    • Journal of the Korean Operations Research and Management Science Society
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    • v.20 no.3
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    • pp.1-16
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    • 1995
  • Group collaborative systems are recently emerging to support a group of users engaged in common tasks such as group decision making, engineering design, group scheduling, or collaborative writing. This paper provides an change management framework for the group collaborative system to facilitate managing dependency relationship between shared objects and dependent user views, and coordinating change and propagation activities between the two in distributed computing environments. Specifically, the framework adopts an object-oriented database paradigm and presents several object constructs capturing dependency management and change notification mechanisms. First, it introduces change management mechanisms with transient shared objects and secondly, it extends them into presistent object computing environment by integrating transaction management mechanisms and change notification mechanisms. A prototype change management framework is developed on a commercial object-oriented database management system.

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Cholinergic Activity Related to Cardiovascular Regulation in Rostral Ventrolateral Medulla of Spontaneously Hypertensive Rats

  • Lee, Seok-Yong;Lee, Sang-Bok
    • The Korean Journal of Physiology and Pharmacology
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    • v.3 no.1
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    • pp.29-34
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    • 1999
  • The hyperactivity of cholinergic system in the RVLM of spontaneously hypertensive rats (SHR) may contribute to the sustained elevation of blood pressure. However, the hyperactivity mechanisms of cholinergic system are controversial. Thus, to clarify the mechanisms of cholinergic hyperactivity in RVLM of the SHR, we studied the activities of enzymes that participate in the biosynthesis and degradation of acetylcholine (ACh) and the density of muscarinic receptors in RVLM of the 14- to 18-week-old SHR and age-marched Wistar Kyoto rats (WKY). Choline acetyltransferase activity was far greater in RVLM of SHR than that of WKY. $[^3H]ACh$ release from RVLM was also greater in SHR than in WKY. Acetylcholinesterase activity and $[^3H]NMS$ binding of RVLM slice of SHR were not significantly different from that of WKY. These results suggest that the enhanced cholinergic mechanisms in the RVLM of SHR is due to the enhanced presynaptic cholinergic tone rather than the altered postsynaptic mechanisms.

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Tribological Behavior of Silicon Carbide Ceramics - A Review

  • Sharma, Sandan Kumar;Kumar, B. Venkata Manoj;Kim, Young-Wook
    • Journal of the Korean Ceramic Society
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    • v.53 no.6
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    • pp.581-596
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    • 2016
  • A comprehensive review on sliding and solid particle erosion wear characteristics of silicon carbide (SiC) ceramics and SiC composites is provided. Sliding or erosion wear behavior of ceramics is dependent on various material characteristics as well as test parameters. Effects of microstructural and mechanical properties of SiC ceramics are particularly focused to understand tribological performance of SiC ceramics. Results obtained between varieties of pairs of SiC ceramics indicate complexity in understanding dominant mechanisms of material removal. Wear mechanisms during sliding are mainly divided in two groups as mechanical and tribochemical. In solid particle erosion conditions, wear mechanisms of SiC ceramics are explained by elastic-plastic deformation controlled micro-fracture on the surface followed by radial-lateral crack propagation beneath the plastic zone.

Static Gait Generation of Quadruped Walking Robot (4각 보행 로봇의 정적 걸음새 생성)

  • Kim, Nam-Woong;Sin, Hyo-Chol;Kim, Kug-Weon
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.16 no.6
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    • pp.217-222
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    • 2007
  • This paper describes a static gait generation process and a mechanical design process of leg mechanisms for quadruped robots. Actually robot walking is realized with the joint motion of leg mechanisms. In order to calculate the time-angle trajectories for each joint of leg mechanisms, we generate end-tip trajectories with time for each leg in the global inertial coordinate system intuitively, followed by coordinate transformations of the trajectories into the local coordinates system fixed in each leg, finally the angle-time trajectories of each joint of leg mechanisms are obtained with inverse kinematics. The stability of the gait generated in this paper was verified by a multi-body dynamic analysis using the commercial software $ADAMS^{(R)}$. Additionally the mechanical specifications such as gear reduction ratio, electrical specifications of motor and electrical power consumption during walking have been confirmed by the multi-body dynamic analysis. Finally we constructed a small quadruped robot and confirmed the gait.

Signal Transduction Mechanisms Mediating Surfactant Phospholipid Secretion in Isolated Type II Cell (Type II Cell 분리체로부터 Surfactant 인지질의 분비를 매개하는 신호변환 기전)

  • Park, Sung-Soo
    • Tuberculosis and Respiratory Diseases
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    • v.43 no.2
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    • pp.123-127
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    • 1996
  • Secretion of surfactant phospholipid can be stimulated by a variety of agonists acting via at least three different signal transduction mechanisms. These include the adenylate cyclase system with activation of cAMP-dependent protein kinase; activation of protein kinase C either directly or subsequent to activation of phosphoinositide-specific phospholipase C and generation of diacylglycerols and inositol trisphosphate; and a third mechanism that involves incresed $Ca^{2+}$ levels and a calmodulin-dependent step. ATP stimulates secretion via all three mechanisms. The protein kinase C pathway is also coupled to phopholipase D which, acting on relatively abundant cellular phospholipids, generates diacylglycerols that further activate protein kinase C. Sustained protein kinase C activation can maintain phosphatidylcholine secretion for a prolonged period of time. It is likely that interactions between the different signaling pathways have an important role in the overall physiological regulation of surfactant secretion.

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Effects of Ligusticum Chuanxiang on blood circulation and oxidative stress (천궁의 혈액순환과 항산화적 효과)

  • Park Yeong-Chul;Lee Sun-Dong;Heo Yong;Kim Hyun-Soo;Lee In-Seon
    • Journal of Society of Preventive Korean Medicine
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    • v.6 no.2
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    • pp.86-94
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    • 2002
  • Ligusticum Chuanxiong and its components were reviewed in terms of pharmacodynamic mechanisms. Three components of about 40 chemical components in Chuanxiong tetramethylpyrazine, ferulinolol and Butylidenephthalide have mainly been studied for its pharmacodynamic mechanisms which are focused on the increase in blood flow and anti-oxidative stress. The mechanisms for the effects of Chuanxiong on the increase in blood flow can be summarized as four ways, 1) anti-coagulation 2) blocker of ${\beta}1$ adrenergic receptor 3) cellular control of Ca++ level 4) collagen synthesis. Chuanxiong also showed the effectiveness on free radical-induced injury. It seems that its effectiveness is also related to the mechanisms for the increase in blood flow.

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Workspace Optimization and Kinematic Performance Evaluation of 2-DOF Parallel Mechanisms

  • Nam Yun-Joo;Park Myeong-Kwan
    • Journal of Mechanical Science and Technology
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    • v.20 no.10
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    • pp.1614-1625
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    • 2006
  • This paper presents the kinematics and workspace optimization of the two different 2-DOF (Degrees-of-Freedom) planar parallel mechanisms: one (called 2-RPR mechanism) with translational actuators and the other (called 2-RRR mechanism) with rotational ones. First of all, the inverse kinematics and Jacobian matrix for each mechanism are derived analytically. Then, the workspace including the output-space and the joint-space is systematically analyzed in order to determine the geometric parameters and the operating range of the actuators. Finally, the kinematic optimization of the mechanisms is performed in consideration of their dexterity and rigidity. It is expected that the optimization results can be effectively used as a basic material for the applications of the presented mechanisms to more industrial fields.

Comparison Study of 2-D OF Parallel Mechanisms: Workspace Optimization and Kinematic Performance (2자유도 병렬 기구의 비교 연구 : 작업영역 최적화 및 기구학적 성능)

  • Nam, Yun-Joo;Lee, Yuk-Hyung;Park, Myeon-Kwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.12 s.255
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    • pp.1564-1572
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    • 2006
  • This paper presents the kinematics and workspace optimization of the two different 2-DOF (Degrees-of-Freedom) planar parallel mechanisms: one (called 2-RPR mechanism) with translational actuators and the other (called 2-RRR mechanism) with rotational ones. First of all, the inverse kinematics and Jacobian matrix of each mechanism are derived analytically. Then, the workspace including the output-space and the joint-space is systematically analyzed in order to determine the geometric parameters and the operating range of the actuators. .Finally, the kinematic optimization of the mechanisms is performed with regards to their dexterity, stiffness and space utilization. It is expected that the optimization results can be effectively used as a basic material for the applications of the presented mechanisms to more industrial fields.

Modelling the Densification Behaviour of Powders Considering Diffusion and Power-Law Creep Mechanisms during Hot Isostatic Pressing (열간정수압압축 시 확산기구 및 Power-law크립기구를 고려한 분말 치밀화거동의 모델링)

  • 김형섭
    • Journal of Powder Materials
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    • v.7 no.3
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    • pp.137-142
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    • 2000
  • In order to analyze the densification behaviour of stainless steel powder compacts during hot isostatic pressing (HIP) at elevated temperatures, a power-law creep constitutive model based on the plastic deformation theory for porous materials was applied to the densification. Various densification mechanisms including interparticle boundary diffusion, grain boundary diffusion and lattice diffusion mechanisms were incorporated in the constitutive model, as well. The power-law creep model in conjunction with various diffusion models was applied to the HIP process of 316L stainless steel powder compacts under 50 and 100 MPa at $1125^{\circ}C$. The results of the calculations were verified using literature data. It could be found that the contribution of the diffusional mechanisms is not significant under the current process conditions.

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