• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.891-895
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• 1996

Performance and efficiency of hybrid (hydraulic-mechanical) pick-up device of deep sea manganese nodules collector are very sensitive to altitude and altitude of pick-up head relative to undulating seafloor. For this reason, motion control of pick-up head relative to the changing deep sea topography and other disturbances is of particular importance in design of pick-up device. The concept of design axiom is applied to a pick-up device of hybrid type. Kinematic analysis conducted in absolute Cartesian coordinates gives position, velocity, and acceleration of the hydraulic cylinders which enable the pick-up head to keep the preset optimal distance from seafloor. Inverse dynamic analysis provides the driving forces of hydraulic cylinders and the reaction forces at each joint. Design sensitivity analysis is performed in order to investigate the effects of possible design variables on the change of the maximum strokes of hydraulic cylinders. The direct differentiation method is used to obtain the design sensitivity coefficients.

• 한국정밀공학회지
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• 제16권8호
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• pp.203-212
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• 1999

This paper describes a deadweight force standard machine with the weight change mechanism which can be used as a primary force standards at a national metrology institute. Since commercial deadweight force machine can generate forces by hanging weights to the weight supporter serially, force steps from deadweight force measuring devices of each having different capacity. In order to increase the force steps, we have specially designed a weight mechanism in which the machine can select the necessary weights and generate the load by hanging the selected weights to the weight supporter. The machine can generate 속 force of the range of 2 kN to 110 kN with force step of 1 kN. All weights have been accurately compensated and calibrated by a mass comparator and its standard uncertainty is less than 2.2 ${\times}\;10^{-6}$. The relative expanded uncertainty of the machine is 1.3 ${\times}\;10^{-5}$.

• 한국정밀공학회지
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• 제15권3호
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• pp.68-74
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• 1998

Performance and efficiency of deep seabed collector is a primary factor for feasibility of commercial deep ocean mining. The efficiency of manganese nodules collector depends on vehicle mobility relative to undulating seafloor and is attributed pickup head to keep altitude and elevation of it against seafloor. For this reason, motion control of pickup head relative to the changing deep-sea topography and other disturbances is of particular importance in design of pickup device. The concept of design axiom is applied to a pickup device of hybrid type in order to evaluate the concept design. Kinematic analysis conducted in absolute Cartesian coordinates gives position, velocity, and acceleration of the hydraulic cylinders which enable the pickup head to keep the preset optimal distance from seafloor. Inverse dynamic analysis provides the driving forces of hydraulic cylinders and the reaction forces at each joint. Design sensitivity analysis is performed in order to investigate the effects of possible design variables on the change of the maximum strokes of hydraulic cylinders. The direct differentiation method is used to obtain the design sensitivity coefficients.

• 소음진동
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• 제7권2호
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• pp.247-254
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• 1997

In the case of a precision equipment, it requires a vibration free environment to provide its proper function. Especially, lithography and inspection devices, which have sub-nanometer class high accuracy and resolution, have come to necessity for producing more improved giga class semiconductor wafers. This high technology equipments require very strict environmental vibration standard in proportion to the accuracy of the manufacturing, inspecting devices. The vibration criteria are usually obtained either by the real vibration exciting test on the equipment or by the analytical calculation. This paper proposes a new method to solve this problem at a time. The permissible vibration level to a precision equipment can be easily obtained by analyzing a process of Frequency Response Function. This paper also demonstrates its effectiveness by applying the proposed method to finding the vibration criteria of a Computer Hard Disk Driver by Impact Test.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.3-10
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• 2008

Micro-electrical discharge machining (micro-EDM) is an effective method for machining all types of conductive materials regardless of hardness. Since micro-EDM is an electro-thermal process, the energy supplied by the pulse generator is an important factor in determining the effectiveness of the process. In this study, an investigation was conducted on the micro-EDM of tungsten carbide (WC) to compare the performance of transistor and resistance/capacitance (RC) pulse generators in obtaining the best quality micro-hole. The performance was measured by the machining time, material removal rate, relative tool wear ratio, surface quality, and dimensional accuracy. The RC generator was more suited for minimizing the pulse energy, which is a requirement for fabricating micro-parts. The smaller-sized debris formed by the low-discharge energy of RC micro-EDM could be easily flushed away from the machined zone, resulting in a surface free of burrs and resolidified molten metal. The RC generator also required much less time to obtain the same quality micro-hole in WC. Therefore, RC generators are better suited for fabricating micro-structures, producing good surface quality and better dimensional accuracy than the transistor generators, despite their higher relative tool wear ratio.

• 한국결정성장학회지
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• 제16권1호
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• pp.43-48
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• 2006

본 2부의 연구에서는 스파크 플라스마 소결의 온도분포, 상대밀도, 입자성장을 해석 하기 위하여 1부 연구의 시뮬레이션 이론을 바탕으로 스파크 플라스마 소결공정을 유한요소법(FEM)과 몬테카를로법(MCM)으로 전산모사하고 실험치와 비교한다. 전산모사를 통하여 소결체의 소결온도가 높을수록 입자성장이 커지고 밀도가 높아져 기계적 성질이 향상되고, 고상 소결에서 몬테카르로 단계가 증가할 수록 기공의 감소와 입자크기의 증대함을 보여 준다.

• 한국측량학회지
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• 제27권2호
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• pp.149-157
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• 2009

GPS측량에 있어서 GPS위성의 궤도정보는 측량정확도에 영향을 미치는 요소중의 하나이며, GPS측량을 위해 제공되는 위성궤도정보에는 방송력과 정밀력, IGS신속력과 IGS초신속력이 있다. 본 연구에서는 경상북도 울진지역에 연구대상지역을 선정하고 GPS관측을 실시하였으며, 74개의 기선에 대하여 TGO를 이용하여 방송력과 정밀력을 사용하여 기선해석을 실시하고 그 결과를 비교하였다. 비교결과 방송력과 정밀력에 의한 차이는 거의 없는 것으로 나타났으며, 기선길이의 상대정밀도에 있어서 방송력의 경우 0.708ppm, 정밀력의 경우 0.706ppm으로 나타나 정밀력을 사용한 결과가 약간 우수한 것으로 나타났다.

• 한국정밀공학회지
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• 제16권3호통권96호
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• pp.164-173
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• 1999

Robot calibration needs accurate measurements of robot end-effector position at a number of different robot configurations. One of the efficient ways of the measurement is "Touching on Jig" method suggested in [7], which utilizes a touch sensor and a fixture consisting of various sizes of blocks. By moving the end-effector to touch the surface of a block whose position relative to the other is known, the end-effector position relative to the fixture coordinate system can be obtained at the instant of touching. However, the global size of fixture is too small to cover the various configurations of the robot. Because of the manufacturing difficulties, the fixture cannot be manufactured large enough for well distributed position measurement. It results in the improvement of robot accuracy only in the limited space near to the fixture rather than over the whole space of the robot working volume. The paper proposes a method to resolve the above problem by measuring the end-effector positions with respect to several different coordinate system using the same measurement devices. It is found that the proposed method leads the improvements of robot position accuracy over the large space of working volume. The experimental studies are performed to show the validity of the method and their results are discussed.

• 한국축산식품학회지
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• 제43권6호
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• pp.949-960
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• 2023

This research aimed to validate a high-performance liquid chromatography method for the quantitative determination of bixin and norbixin in various foods. The Diode Array Detector (495 nm) technique was used. Method was validated for specificity, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, and accuracy, and the measurement uncertainty was assessed. The calibration curve showed excellent linearity (r²≥0.9999) over the tested concentration range of 0.2-25 mg/L. The LOD and LOQ were 0.03-0.11 and 0.02-0.05 mg/L for bixin and norbixin, respectively. The intra-and inter-day accuracies and precisions were 88.0±1.3-97.0±0.5% and 0.2%-2.6% relative SD (RSD) for bixin and 88.2±0.8-105.8±0.8% and 0.3%-2.7% RSD for norbixin, respectively. Inter-laboratory validation for accuracy and precision was conducted in three laboratories, and these results all met the AOAC guidelines. In addition, the relative expanded uncertainty (<22%) satisfied the CODEX recommendation. Furthermore, products distributed in Korea were monitored for annatto extracts using the proposed method to demonstrate its application. The developed analytical method is reliable for quantifying bixin and norbixin in various foods.

• 한국대기환경학회지
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• 제33권3호
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• pp.277-288
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• 2017

Previous studies of health effects of $PM_{2.5}$ performed spatial monitoring campaigns to assess spatial variability of $PM_{2.5}$ across people's residences. Highly reliable portable and cost-effective samplers will be useful for such campaigns. This study aimed to investigate applicability of the Deployable Particulate Impact Sampler(DPIS), one of the compact impact samplers, to spatial monitoring campaigns of $PM_{2.5}$ in Seoul, Korea. The investigation focused on the consistency of $PM_{2.5}$ concentrations measured by DPISs compared to those by the Low-volume Cyclone sampler (LCS). LCS has operated at a fixed site in the Seoul National University Yeongeon campus, Seoul, Korea since 2003 and provided qualified $PM_{2.5}$ data. $PM_{2.5}$ sampling of DPISs was carried out at the same site from November 17, 2015 through February 3, 2016. $PM_{2.5}$ concentrations were quantified by the gravimetric method. Using a duplicated DPIS, we confirmed the reliability of DPIS by computing relative precision and mean square error-based R squared value ($R^2$). Relative precision was one minus the difference of measurements between two samplers relative to the sum. For accuracy, we compared $PM_{2.5}$ concentrations from four DPISs (DPIS_Tg, DPIS_To, DPIS_Qg, and DPIS_Qo) to those of LCS. Four samplers included two types of collection filters(Teflon, T; quartz, Q) and impaction discs(glass fiber filter, g; pre-oiled porous plastic disc, o). We assessed accuracy using accuracy value which is one minus the difference between DPIS and LCS $PM_{2.5}$ relative to LCS $PM_{2.5}$ in addition to $R^2$. DPIS showed high reliability (average precision=97.28%, $R^2=0.98$). Accuracy was generally high for all DPISs (average accuracy=83.78~88.88%, $R^2=0.89{\sim}0.93$) except for DPIS_Qg (77.35~78.35%, 0.82~0.84). Our results of high accuracy of DPIS compared to LCS suggested that DPIS will help the assessment of people's individual exposure to $PM_{2.5}$ in extensive spatial monitoring campaigns.