• 천문학회지
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• 제47권6호
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• pp.279-291
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• 2014

I show that the WFIRST microlensing survey will enable detection and precision orbit determination of Kuiper Belt Objects (KBOs) down to $H_{vega}=28.2$ over an effective area of ${\sim}17deg^2$. Typical fractional period errors will be ${\sim}1.5%{\times}10^{0.4(H-28.2)}$ with similar errors in other parameters for roughly 5000 KBOs. Binary companions to detected KBOs can be detected to even fainter limits, $H_{vega}=29$, corresponding to R~30.5 and effective diameters D~7 km. For KBOs H~23, binary companions can be found with separations down to 10 mas. This will provide an unprecedented probe of orbital resonance and KBO mass measurements. More than a thousand stellar occultations by KBOs can be combined to determine the mean size as a function of KBO magnitude down to H~25. Current ground-based microlensing surveys can make a significant start on finding and characterizing KBOs using existing and soon-to-be-acquired data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1043-1047
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• 2003

With the advancement of micro-systems and nanotechnology, the need for ultra-precision fabrication techniques has been steadily increasing. In this paper, a novel nano-structure fabrication process that is based on the fundamental understanding of nano-scale tribological interaction is introduced. The process, which is called Mechano-Chemical Scanning Probe Lithography (MC-SPL), has two steps, namely, mechanical scribing for the removal of a resist layer and selective chemical etching on the scribed regions. Organic monolayers are used as a resist material, since it is essential for the resist to be as thin as possible in order to fabricate more precise patterns and surface structures. The results show that high resolution patterns with sub-micrometer scale width can be fabricated on both silicon and various metal surfaces by using this technique.

• 한국기계가공학회지
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• 제2권3호
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• pp.56-61
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• 2003

This paper described about on-machine profile measurement of aspheric surfaces using contact probing technique in ultra precision machine. A contact probe has been designed as a sensing device to obtain measuring resolutions in nanometer regime using a circle leaf spring mechanism and a capacitive-type sensor. The contact probe which is installed on the z-axis is In touch with the aspheric objects which is fixed on the spindle of the diamond turning machine(DTM) during the measuring procedure. The x, z-axis motions of the machine are monitored by a set of two orthogonal plane mirror type laser interferometers. As a results, the developed contact probe on-machine measurement system showed 10 nanometers repeatability with a ${\pm}2{\sigma}$ and uncertainty of 200 nmPv.

• 한국기계가공학회지
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• 제11권5호
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• pp.76-81
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• 2012

The continuing demand for increasingly slimmer and brighter liquid crystal display(LCD) panels has led to an increased focus on the role of the light guide panels(LGPs) or optical films that are used to obtain diffuse, uniform light from the backlight unit(BLU). And the most basic process in the production of such BLU components is the micromachining. LCD BLUs comprise various optical elements such as a LGP, diffuser sheet, prism sheet, and protector sheet with micro patterns. High aspect ratio patterns are required to reduce the number of sheets and enhance light efficiency, but there is a limit to the aspect ratio achievable for a given material and cutting tool. Therefore, this study comprised a series of experimental evaluations conducted to determine the machining feasibility in microcutting various aspect ratio patterns on electroless nickel plated die materials when using single-crystal diamond tools. Cutting performance was evaluated at various cutting speeds and depths of cut using different machining methods and machine tools.

• 한국기계가공학회지
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• 제11권3호
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• pp.41-47
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• 2012

Surface roughness is widely used as an index for processing degree of accuracy. Recently, regression analysis to predict the machining results are actively used to characterize a cutting operations. In the past, diamond machining had been used for ultra precision cutting operation, but now industrial diamond tools like PCD(Polycrystaline Diamond) has been widely used in ultraprecision machining of nonferrous metals. In this study, the authors focus on the effect of PCD tool property on the surface roughness of different types of aluminum alloy after cutting process by CNC operated lathe. Based on the regression analysis approach on a surface roughness data obtained by experiment, predictive analysis of surface roughness is effective to achieve better surface quality.

• 한국기계가공학회지
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• 제11권1호
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• pp.1-6
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• 2012

The polishing of silicon wafers has an important role in semiconductor manufacturing. Generally, getting a flat surface such as a mirror is the purpose of the process. The wafer surface roughness is affected by many variables such as the characteristics of the carrier head unit, operation, speed, the pad and slurry temperature. Optimum process conditions for experimental temperature, pH value, down-force, slurry ratio are investigated, time is used as a fixed factor. This study carried out a series of experiments at varying platen, chuck rpm and oscillation cpm taking particular note of the difference between the rpm and the affect it has on the surface roughness. In this experiment determine the optimum conditions for polishing silicone wafers.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.405-409
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• 2003

We explored a new rough grinding technique on optics materials such as Zerodur. The facility used is a NANOFORM-600 diamond turning machine with a custom grinding module and range of diamond resin bond wheel. The grinding parameters such as workpiece rotation speed depth of cut and feed rate were altered while grinding the workpiece surfaces of 20m in diameter. Surface roughness is measured by Form Talysurf series2. Our target is to define grinding conditions producing the surface roughness better than 0.02${\mu}{\textrm}{m}$ Ra and the form accuracy of around 0.2${\mu}{\textrm}{m}$ PV.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.167-172
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• 2003

The machining method by using end-milling tool has been applying in machining structures of various shapes because of the availability. Recently, all kinds of industries based on the parts of micro shape are developing, and the demands of mechanical micro machining technology are Increasing suddenly to produce these parts. According to such changes, the technology of the micro end-milling machining is applying as one of the most important machining means. This research is to aim at developing machining technology for various micro structures using micro end-mill. This paper introduces micro mechanical machining system with ultra precision, and demonstrates methods manufacturing all sorts of parts and moldings for industry and examples of applicable machining by using micro end-milling tool of micro sizes from hundreds to tens in diameter.

• 한국생산제조학회지
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• 제23권4호
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• pp.361-367
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• 2014

Ultra-precision positioning plays a crucial role in emerging technologies such as electronics, bioengineering, optics, and various nanofabrication technologies. As a result, various nanopositioning methods have been presented. In particular, nanopositioning using a flexure mechanism and piezo-electric actuator is one of the most valuable methods because of its friction-free motion and subnanometer-scale motion resolution. In this study, a rotational nanoactuator based on a right-circular flexure mechanism and piezo-electric actuator was developed through a consideration of the kinematics and structural deformation. An experimental setup was constructed to verify the performance expectation. Consequently, it was demonstrated that the developed system had a maximum rotational angle of about 0.01 rad, as well as sufficient linearity with respect to the input voltage.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권1호
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• pp.16-22
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• 2013

This paper presents the analysis and optimization of air-core permanent magnet linear synchronous motor with overlapping concentrated windings to achieve high thrust density, high thrust per copper losses and low thrust ripple. For the motor design, we adopt equivalent magnetizing current (EMC) method to analyze the magnetic field and give analytical formulae for calculation of motor parameters such as no-load back EMF, dynamic force, thrust density and thrust per copper losses. Further, we proposed a multi-objective optimization by genetic algorithm to search for the optimum parameters. The design optimization is verified by 2-D Finite Element analysis (FEA).