• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.348-352
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• 2005

본 논문은 조선소에서 계획기간동안 각 플랜트의 생산일정에 따른 블록의 모든 수송요구량이 미리 알려져 있는 정적인(static) 수송환경을 고려한 트랜스포터 일정계획문제를 다룬다. 조선소 내에서 블록들의 수송은 몇 가지 특성을 가진다. 500톤을 초과하는 거대 블록들은 2대 이상이 결합된 새로운 형태의 트랜스포터를 이용하여 운반된다. 운반이 요구되는 블록들 중 일부는 계획기간동안 규정된 출발요구시각에 pick-up되기를 요구하는 반면 나머지 블록들은 계획기간동안 규정된 도착요구시각 전에 delivery되기를 요구한다. 이러한 트랜스포터의 결합 및 시간 제약은 문제를 더욱 복잡하게 하는 요인이 된다. 본 논문에서는 계획기간 내에 모든 블록운반 요구사항들(출발지와 도착지, pick-up과 delivery 시각, 톤수, 결선 등)을 만족시키는 트랜스포터 일정계획문제를 다룬다. 트랜스포터 일정계획문제에서 중요한 주제는 총 로지스틱스 시간 (공차운행시간, delay 시간 및 tardy 시간)을 최소화하기 위해 계획기간 내에 최소의 트랜스포터 운영대수로 각 트랜스포터에 어떤 블록을 할당하고 어떤 순서로 운반할 것인 지를 결정하는 것이다. 이에 본 논문에서는 주어진 트랜스포터 일정계획문제를 해결하기 위해, 1단계에서 최소비용 네트워크 흐름문제를 근간으로 트랜스포터의 최소사용대수를 구하고 이를 기초로 2단계에서 각 트랜스포터에의 블록 할당과 운반순서를 결정하는 2단계 휴리스틱 알고리즘을 제안한다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.6
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• pp.937-944
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• 2013

This paper describes an improved model that can be used for configuring a non-contact pneumatic head to handle a large sheet of glass. The cylindrical head model is of a large size (70 mm). It operates on vortex flow, which can simultaneously generate suction and repulsion over the flat object's surface. The head allows for the minimal non-contact lifting of objects weighing over 3N by using reference conditions (working pressure and head dimensions). Additionally, a functional flow-guide is applied for inducing a developing tangential vortex flow to increase suction and repulsion to the reference head. The cylindrical flow-guide is associated with relatively low tangential velocity. The improved model generates greater lifting force than the reference model, as verified experimentally.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.9
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• pp.418-423
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• 2003

This paper describes an electronic compass using micromachined X- and Y-axis micro fluxgate sensors which were perpendicularly aligned each other to measure X- and Y-axis magnetic fields respectively. The fluxgate sensor was composed of rectangular-ring shaped magnetic core and solenoid excitation(49 turns) and pick-up(46 turns) coils. Excitation and pick-up coil patterns which were formed opposite to each other wound the magnetic core alternatively to improve the sensitivity and to excite the magnetic core in an optimal condition with reduced excitation current. The magnetic core has DC effective permeability of ~1000 and coercive field of ~0.1 Oe. The magnetic core is easily saturated due to the low coercive field and closed magnetic path for the excitation field. To decrease the difference of induced second harmonic voltages from X- and Y-axis, excitation condition of 2.8 $V_{P-P}$ and 1.2 MHz square wave was selected. Excellent linear response over the range of -100 $\mu$T to +100 $\mu$T was obtained with 210 V/T sensitivity. The size of each micro fluxgate sensor excluding pad region was about 2.6${\times}$1.7 $mm^2$ and the power consumption was estimated to be 14 mW.W.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.151-155
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• 2002

This paper presents a micro fluxgate magnetic sensor in printed circuit board (PCB). The fluxgate sensor consists of five PCB stack layers including one layer magnetic core and four layers of excitation and pick-up coils. The center layer as a magnetic core is made of a micro patterned amorphous magnetic ribbon with extremely high DC permeability of ∼100,000 and the core has a rectangular-ring shape. The amorphous magnetic core is easily saturated due to the low coercive field and closed magnetic path for the excitation field. Four outer layers as an excitation and pick-up coils have a planar solenoid structure. The chip size of the fabricated sensing element is 7.3${\times}$5.7m㎡. Excellent linear response over the range of -100${\mu}$T to +100${\mu}$T is obtained with 540V/T sensitivity at excitation square wave of 3V$\_$P-P/ and 360kHz. The very low power consumption of ∼8mW was measured. This magnetic sensing element which measures the lower fields than 50${\mu}$T, is very useful for various applications such as: portable navigation systems, military research, medical research, and space research.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.8
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• pp.702-707
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• 2002

This paper presents a micro fluxgate sensor in printed circuit board (PCB). The fluxgate sensor consists of five PCB stack layers including one layer magnetic core and four layers of excitation and pick-up coils. The center layer as a magnetic core is made of a micro patterned amorphous magnetic ribbon and the core has a rectangular-ring shape. The amorphous magnetic core is easily saturated due to the low coercive field and closed magnetic path for the excitation field. Four outer layers as an excitation and pick-up coils have a planar solenoid structure. The chip size of the fabricated sensing element is 7.3$\times$5.7$\textrm{mm}^2$. Excellent linear response over the range of -100$\mu$T to +100$\mu$T is obtained with 540V/T sensitivity at excitation square wave of 3 $V_{p-p}$ and 360kHz. The very low power consumption of ~8mW was measured. This magnetic sensing element, which measures the lower fields than 50$\mu$T, is very useful for various applications such as: portable navigation systems, military research, medical research, and space research.h.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.1009-1012
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• 1999

Recently, there is a strong need of DVD (Digital Versatile Disk) system of high density. high speed, and high accuracy System performances mostly depend on not only optical system, but also servo technology to drive it. Therefore, we investigate main technology concerned with optical pick-up unit based on 4.7GB DVD-RAM and analyzes technology of optical and servo systems that are required for high density high speed and high accuracy from the viewpoint of control. And then, we design a linear controller based on specification of 4.7GB DVD-RAM that is commercially available now. We analyze the dynamic characteristics of optical system that is coupled with control system and verify effect on performance indices of servo due to Parameter variation of pick-up by simulation. Finally, we will propose controller design specifications and provide direction of technical development for servo system and problems coupled with high capacity for 15GB level in the future.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.12
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• pp.1997-2003
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• 2003

Recently, there have been many researches and developments in optical disc drive by high density of track and high access speed. Therefore, the optical pick-up should guarantee highly accurate dynamic characteristics for the wide bandwidth in order to cope with this trend. These demands for optical pick-up actuator can be solved by improvements of lens-holder through the following methods. The first way is the analysis of the sensitivity matrix of design variables for vibration modes after appropriate design parameters are selected like shapes and local dimensions of a lens-holder. The second way is the optimization of design variables by calculating sequential linear programming after the problem of extending bandwidth are converted to problem of minimizing adequate objective function. In the result, modified FE model is obtained through several iterations by finite difference scheme(FDS). While results of the first way show better convergence of the target frequency, the second result shows better reduction of mass increase.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.277-282
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• 2004

This paper concerns about dynamic analysis of an underwater test miner, which operates on cohesive soil. The test miner consists of tracked vehicle and pick-up. device. The motion oj pick-up device relative to the vehicle chassis is controlled by two pairs of hydraulic cylinders. The test miner is modeled by means of a commercial software. A terramechanics model of cohesive soft soil is implemented to the software and applied to dynamic analysis of the test miner model. The dynamic responses of test miner are studied with respect to of four different types of terrain conditions.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.424-429
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• 2004

The 4-probe method with a voltage tap on terminals has been used for the measurement of the critical current of multi-strand high-T$_{c}$ superconducting(HTS) cables. And the critical current of cables is obtained as the measured total current divided by the number of conductor when the terminal voltage exceeds the predetermined criterion of critical current. However, because of the non-uniform current distribution due to the different critical current, shapes, and other characteristics of each conductor, this is not applicable method to the multi-strand HTS cable. To determine the critical current of multi-strand HTS cable, the critical current of each conductor must be measured with different method. h this paper, the current distribution and the critical current of each conductors in multi-strand cable were measured with specially made Pick-up coils and voltage taps. It is presented that the real critical current of multi-strand is smaller than sum of each conductors. The main cause of non-uniform current distribution is the difference between the resistances appeared in each HTS wires.s.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.163-170
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• 2004

In order to produce high-quality optical components, aspheric lenses have been widely applied in recent years. An aspheric lens consists of aspheric surfaces instead of spherical ones, which causes difficulty in the design process as well as the manufacturing procedure. Although injection molding is widely used to fabricate optical lenses owing to its high productivity, there remains lots of difficulty to determine appropriate mold design factors and injection molding parameters. In the injection molding fields, computer simulation has been effectively applied to analyze processes based on the shell analysis so far. Considering the geometry of optical lenses, however, numerical analysis based on solid elements has been reported as more reliable approach than shell -based one. The present work covers three-dimensional injection molding simulation using MP1/Flow3D and relevant deformation analysis of an injection molded plastic lens based on solid elements. Numerical analysis has been applied to the injection molding processes of an aspheric lens for a photo pick-up device. The reliability of the proposed approach has been verified in comparison with the experiments.