Design and simulation of a magnetohydrodynamic micro-pump to provide time varying tensile force for vibration suppression in viscoelastic micro-beams

A. Alipour,M. H. Korayem,D. Younesian 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.5

In this paper, a new strategy for providing tensile force to suppress the transverse vibration of a micro-beam is introduced. This axial tensile force is supplied by a specific fluid flow called "magnetohydrodynamics" (MHD), which flows in a micro-pump, and then the fluid enters the micro-beam. The micro-beam is vibrated by an oscillating external force acting at its base. Therefore, a fluid structure interaction problem arises. The pressure of the fluid is increased due to the Lorentz force appears in the micro pump, and is directed by the channel towards the micro-beam and suppress the vibration of the micro-beam. It was observed that when the magnetic field rises from 0.25 Tesla to 0.5 Tesla, the amplitude of the micro-beam fluctuations will decrease from 13 6 10 m - ´ to 13 3 10 m - ´ . Assuming a laminar and incompressible flow, the finite volume method (FVM) is used to solve the governing equations. In the design of the micropump, the parameters studied are the value of the magnetic field, the amount of voltage applied to the micro-pump, the external force oscillation amplitude and the Reynolds number, and the effect of each parameter on the fluid and micro-beam behavior. The results show that with increasing fluid pressure in the micro-pump, the micro-beam vibration is suppressed. In addition, the pressure of the fluid along the micro-beam remains constant at 0.1 percent.

마이크로 금형 부품을 위한 마이크로 절삭가공 기술

하석재,박정연,김건희,윤길상 한국금형공학회 2019 한국금형공학회지 Vol.13 No.1

In this paper, we studied the micro tool deflection, micro cutting with low temperature, and deformation of micro ribs caused by cutting forces. First, we performed an integrated machining error compensation method based on captured images of tool deflection shapes in micro cutting process. In micro cutting process, micro tool deflection generates very serious problems in contrast to macro tool deflection. To get the real images of micro tool deflection, it is possible to estimate tool deflection in cutting conditions modeled and to compensate for machining errors using an iterative algorithm correcting tool path. Second, in macro cutting fields, the cryogenic cutting process has been applied to cut the refractory metal but, the serious problem may be generated in micro cutting fields by the cryogenic environment. However, if the proper low temperature is applied to micro cutting area, the cooling effect of cutting heat is expected. Such effect can make the reduction of tool wear and burr formation. For verifying this passibility, the micro cutting experiment at low temperature was performed and SEM images were analyzed. Third, the micro pattern was deformed by the cutting forces and the shape error occurred in the sidewall multi-step cutting process were minimized. As the results, the relationship between the cutting conditions and the deformation of micro-structure during micro cutting process was investigated.

Micro-EDM 가공에서 Micro-Spot 이용한 표면 형상의 예측 모델에 관한 연구

이철수(Cheol Soo Lee),김종민(Jong Min Kim),허은영(Eun Young Heo),김동수(Dong Soo Kim) (사)한국CDE학회 2011 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2011 No.1

Recently with increased demand of micro mechanical and electronic devices, interests are focused on machining of micro parts. Accordingly, a lot of researches have been progressed for fabrication or micro parts using MMT (Micro Machining Technology) or MEMS (Micro Electromechanical System), etc. and concerned machining technologies. As Micro Machining Technology (MMT) has low production cost and is able to overcome limit of the materials, it has very important position over MEMS technology. Metal forming in micro unit has been suggested in various methods for a long time and a lot of related data has been accumulated. However, the existing machines such as micro lathe, micro milling or micro drilling, etc. have factors to be overcome to allow machining in micro unit precision. In order to overcome these machining problems, a lot of researches on machining such as micro channel or hole, etc. using complex machining technique, Micro EDM, rather than the existing methods have been being progressed. This study intents to measure shape of surface for micro discharging machining using micro spot that is a unit machining of micro discharging machining and surface shape from micro discharging using it.

외경 500um 금속기어개발에 관한 연구

허영무(Y.M. Heo),장성호(S.H.Chang),신광호(S.H.Shin),김종덕(J.D.Kim),제태진(T.J.Je) 한국소성가공학회 2011 금형가공 심포지엄 Vol.2011 No.9

At present there are many studies are carried out to develop micro parts. A micro drive unit assembled with several micro movable parts is needed to industrialize the functional micro parts such as micro pump, micro-chip, micro motor and micro gear etc. In this study, making micro metal gear with outer diameter 500um, a powder injection molding process was used. To make micro metal part, it is needed micro shape cavity & core in molds for filling of feedstocks there are several methods to make micro shape or pattern such as LIGA process, laser machining, micro etching and micro milling process etc. But these micro methods are expensive and needed some special facilities to fabricate. So in this study, conventional machining methods were tested to make micro gear cavity shape. The preliminary studies were conducted to evaluate the filling of cavity and machine that. Finally outer diameter 500um level micro gear was injection molded and debinded and sintered. Some incomplete filling was occurred in the end of filling at gear teeth using 17-4PH 3F feedstock. The final sintered micro metal gear showed about 434um of outer diameter.

An annulus-type micro reforming system integrated with a two-staged micro-combustor

Lee, J.H.,Do, G.S.,Moon, H.J.,Kwon, O.C. Elsevier 2010 International journal of hydrogen energy Vol.35 No.4

<P><B>Abstract</B></P><P>A new configuration of a micro reforming system integrated with a micro-combustor is studied experimentally and computationally. The micro-combustor as a heat source is a simple cylinder, which is easy to fabricate, but is two-staged (expanding downstream) to control ignition and stable burning. A micro-evaporator to vaporize methanol–water mixtures and a micro-reformer to convert the vaporized methanol–water mixtures to hydrogen are annuli, which are effective to transfer heat from the first and second-stage micro-combustors, respectively. The annulus-type micro reforming system is designed to produce 1–10W (based on lower heating value, LHV) of hydrogen using the steam reforming method. The molar ratio of water to methanol, the feed rate of water–methanol mixtures, the micro-combustor inlet velocity of fuel–air mixtures and the micro-combustor materials substantially affect the performance of the designed micro reforming system. Under optimized design and operating conditions, the micro reforming system produces 6.9W (based on LHV) of hydrogen with a conversion rate of 97.5%, an overall system efficiency of 39.7% and a carbon monoxide concentration of 6.7ppm. Thus, the present configuration can be applied to practical micro reforming systems for use with fuel cells.</P>

유럽연합의 마이크로크레딧 정책과 시사점

박동규 ( Tong Kyu Park ),박창균 ( Chang Gyun Park ),오규택 ( Gyu Taek Oh ) 한국EU학회 2009 EU학연구 Vol.14 No.2

We observe increased interests in micro-credit from both academia and policy makers mainly because they believe that it could be used an alternative device for credit provision to the poor to help enhance their income generating ability. However, some argue that micro-credit is not an appropriate approach to stimulate micro-enterprises in Korean context since there already exists too many suppliers in the markets for which most micro-enterprises provide their products. We pay attention to the fact that the competitive edge of micro-enterprises can be enhanced through innovative activities of micro-entrepreneurs with better technology and easier access to financial resources provided by micro-credit institutions. We suggest that policy makers in Korea should recognize the strategy value of micro-credit in combating two most debated problems recently in Korea; higher unemployment and worsening income distribution. It is also much desirable that we should build a new micro-credit model applicable to Korean environment. European experiences can provide insightful implications in designing a new micro-credit policy framework. First, micro-credit is regarded as useful policy tool to achieve both higher employment and less income inequality. Second, long-term sustainability of micro-enterprises is the ultimate target. Third, EU does not involved in direct relationship with individual micro-enterprises. Instead, MC institutions are the main target of MC policy. Fourth, a variety of policy measures to support MC are taken to cope with diverse needs of MC institutions. The measures include loan, guarantee, equity and quasi-equity investment, and technical assistance. The paper finally propose four important tasks in formulating a new MC model applicable to Korean context. First, policy goals should be clarified. Two goals, enhancing competitiveness of micro-enterprises and improving income distribution, can be pursed through promoting MC. Second, MC institutions should be allowed to exercise decision making power including setting the level of interest rate, without interruptions from outside in order to achieve long-term sustainability. Third, a new microfinance investment fund can be established. Both private and public sectors can participate in establishing the fund to ensure stable funding source for MC institutions. Fourth, policy support should be more focused on MC infrastructure such as establishment of MC network, building the framework for training MC experts, and capacity building for MC institutions.

A Review on the Analysis and Experiment of Fluid Flow and Mixing in Micro-Channels

Simon Jayaraj,Sangmo Kang,Yong Kweon Suh 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.3

The studies with respect to micro-channels and micro-mixers are expanding in many dimensions. Most significant area of micro-mixer study is the flow analysis in various micro-channel configurations. The flow phenomena in microchannel devices are quite different from that of the macro-scale devices. An attempt is made here to review the important recent literature available in the area of micro-channel flow analysis and mixing. The topics covered include the physics of flow in micro-channels and integrated simulation of the micro-channel flow. Also, the flow control models and electro-kinetically driven micro-channel flows are dealt in detail. A survey of important numerical methods, which are currently popular for micro-channel flow analysis, is carried out. Different options for mixing in microchannels are provided, in sufficient detail.

Research on Operation and Control of Micro-Grid System

Cunxu Wang,Xingfeng Xiao,Aijun Zhang,Xiaoyu Sun 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.7

Micro-grid is the significant part of the distribution network in the future of smart grid, which has advanced and flexible operation and control pattern, and integrates distributed clean energy. It is a study of the direction of the grid in the future. In the paper, it gives an account of the operation and control of micro-grid. First, the concept of micro-grid, the structure and characteristics of the typical micro-grid and the significance of the development of micro-grid are analyzed. Second, it introduces typical control strategy which contains the integrated control strategy of Micro-grid and a typical control mode of Micro-power. At last, based on a comprehensive control strategy, it proposed the operation mode of Micro-grid.

Evaluation on Ground Surface Accuracies of Large-Depth and Steeply Micro-Structured SiC Surfaces

Ping Li,Xiaochu Liu,Junwu Chen 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.2

Microstructures can be used to enhance technical surfaces with additional functionalities, which are driving advances in many fields of industrial applications. However, it is difficult to obtain 3D valid information about large-depth and steeply micro-structured surfaces owing to the limitation of the white light interferometric measurements. Therefore, the registration of bisection-measured micro-topographies is proposed using the interactive closest point (ICP) method combined with the genetic algorithm, with the objective of evaluating the micro-form and micro-profile accuracies of a micro-structured surface. First, a diamond grinding-wheel V-tip was employed to fabricate micro-pyramid-structured SiC; subsequently, 3 ideal point models were constructed to match the measured point clouds using the ICP method; finally, the non-dominated sorting genetic algorithm-II (NSGA-II) was used to micro-alignment the bisection-measured point clouds with regard to micro-form and micro-profile errors. It is shown that the registration accuracy is dominated by the ideal profile point number, but the registration efficiency depends on the ideal point number. The the NSGA-II could improve the registration accuracy of micro-profile by 42.6% compared with traditional ICP matching. It is confirmed that the micro-grinding is able to control the micro-form and the micro-profile accuracies within 4%.

Micro/Meso-scale Shapes Machining by Micro EDM Process

Kim Young-Tae,Park Sung-Jun,Lee Sang-Jo Korean Society for Precision Engineering 2005 International Journal of Precision Engineering and Vol.6 No.2

Among the micro machining techniques, micro EDM is generally used for machining micro holes, pockets, and micro structures on difficult-cut-materials. Micro EDM parameters such as applied voltage, capacitance, peak current, pulse width, duration time are very important to fabricate the tool electrode and produce the micro structures. Developed micro EDM machine is composed of a 3-axis driving system and RC circuit equipped with pulse generator. In this paper, using micro EDM machine, the characteristics of micro EDM process are investigated and it is applied to micro holes, slots, and pockets machining. Through experiments, relations between machined surface and voltages and between MRR and feedrate are investigated. Also the trends of tool wear are investigated in case of hole and slot machining.