• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1507-1510
• /
• 2005

This study was carried out as a part of the research on the development of a maskless and electroless process for fabricating metal micro/nanostructures by using a nanoindenter and an electroless deposition technique. $2-\mu{m}-deep$ indentation tests on Ni and Cu samples were performed. The elastic recovery of the Ni and Cu was 9.30% and 9.53% of the maximum penetration depth, respectively. The hardness and the elastic modulus were 1.56 GPa and 120 GPa for Ni and 1.49 GPa and 100 GPa for Cu. The effect of single-point diamond machining conditions such as the Berkovich tip orientation (0, 45, and $90^{\circ}$) and the normal load (0.1, 0.3, 0.5, 1, 3, and 5 mN), on both the deformation behavior and the morphology of cutting traces (such as width and depth) was investigated by constant-load scratch tests. The tip orientation had a significant influence on the coefficient of friction, which varied from 0.52-0.66 for Ni and from 0.46-0.61 for Cu. The crisscross-pattern sample showed that the tip orientation strongly affects the surface quality of the machined area during scratching. A selective deposition of Cu at the pit-like defect on a p-type Si(111) surface was also investigated. Preferential deposition of the Cu occurred at the surface defect sites of silicon wafers, indicating that those defect sites act as active sites for the deposition reaction. The shape of the Cu-deposited area was almost the same as that of the residual stress field.

• Korean Journal of Human Ecology
• /
• v.15 no.3
• /
• pp.457-467
• /
• 2006

The following research compares two mostly-used apparel systems that are used in colleges of Korea, Gerber and PAD, by analyzing advantages and disadvantages of their Dart, Tuck and Pleats-related functions in pattern construction process. The results are the following: First, regarding transformation methods, Gerber system was able to use pivot method, while PAD system was able to use both pivot and slash method. As for movement, distribution, synthesis, folding, producing additional Dart function, the PAD system was not able to synthesize more than two Darts, and only showed differences for other functions. On the other hand, the diamond-shape Dart and diagonal Dart can be produced only in PAD system, while none of curvy shaped Dart can be produced in both systems. Second, as for pattern outer line connection capability, which is a Dart automatic transformation function, both systems showed unnatural shapes and need for correction. Third, when constructing according to the type of Tuck, we could distribute multiple Darts at a time with PAD system, while with Gerber system, distribution into multiple Darts at a time was impossible at all. Fourth, when constructing according to the contour of Pleats, Gerber system made it possible to make construction of multiple lines and box/inverted Pleats with just one order, but PAD system required repetitive tasks, which remains room for enhancement in regard to such inefficiency.

• Fashion & Textile Research Journal
• /
• v.7 no.1
• /
• pp.56-62
• /
• 2005

Fancy Yarn has developed diverse textures in fabrics, reducing the time in yarn and fabric production or apparel making in order to develop creative goods. In this study aimed to propose the use of a 4D box system to make fancy yarn shapes with loops, knops and spirals and the like. The change in texture was analysed and simulated to produce a suitable fabric image by using the fancy yarns fabric. The results are as follows. The plain weave, 2/2 basket weave, 2/2 twill weave, 2/2 2 complete broken weaves, and 5 harness sateen weaves were woven and a fabric image formed. In the case of the loop and the knop yarns fabric image, compared to the twisted fabric image the surface was covered by loops or some parts became partially black. In the case of the spiral shape it showed pattern continuity in spiral shapes 1, 2 and 3. The more twisted spirals produced a diamond shaped pattern or a twill line and a herring bone shaped twill line. An evenly distributed black fabric image appeared in 5 harness sateen weave. For the loop shape the broken weave or 5 harness sateen weave was produced; basket weave and broken weave for the knop yarn 1 or knop yarn 2; and for the spiral shape a plain fabric or 5 harness sateen weave were produced much similar to the fabric image. The surface texture of the mapped image compared to the twisted fabric image produces fancy yarn fabric images covered with loops or irregular spots caused by the knop and the spiral. Therefore it is appropriate or suitable for the simulation of tweed or woolen wool fabrics. The fabric image which produced consistent and continuous lines is therefore more suitable for simulations of twill or herringbone fabric images.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.8 s.185
• /
• pp.171-177
• /
• 2006

This study was performed as a part of the research on the development of a maskless and electroless process for fabricating metal micro/nanostructures by using a nanoindenter and an electroless deposition technique. $2-{\mu}m$-deep indentation tests on Ni and Cu samples were performed. The elastic recovery of the Ni and Cu was 9.30% and 9.53% of the maximum penetration depth, respectively. The hardness and the elastic modulus were 1.56 GPa and 120 GPa for Ni and 1.51 GPa and 104 GPa for Cu. The effect of single-point diamond machining conditions such as the Berkovich tip orientation (0, 45, and $90^{\circ}$ ) and the normal load (0.1, 0.3, 0.5, 1, 3, and 5 mN), on both the deformation behavior and the morphology of cutting traces (such as width and depth) was investigated by constant-load scratch tests. The tip orientation had a significant influence on the coefficient of friction, which varied from 0.52-0.66 for Ni and from 0.46- 0.61 for Cu. The crisscross-pattern sample showed that the tip orientation strongly affects the surface quality of the machined are a during scratching. A selective deposition of Cu at the pit-like defect on a p-type Si(111) surface was also investigated. Preferential deposition of the Cu occurred at the surface defect sites of silicon wafers, indicating that those defect sites act as active sites for the deposition reaction. The shape of the Cu-deposited area was almost the same as that of the residual stress field.

• Tribology and Lubricants
• /
• v.37 no.3
• /
• pp.106-111
• /
• 2021

There are several studies on reducing the friction that occurs on the relative sliding contact surface of moving parts under extreme environments. In particular, a solid lubricated bearing is studied to solve the tribological problem with friction reduction and durability parts using solid lubricants (lead or silver) in a vacuum atmosphere. Galinstan is mainly used as a liquid metal lubricant, but it is inevitable to have limited tribological applications owing to its high coefficient of friction. Many researchers work on surface texturing for surface modification and precision processing methods. To increase durability and low friction, DLC coating with hydrophobicity is applied on the contact surface texture. Therefore, using an untextured specimen, a dimple specimen, and a DLC-coated dimple specimen under liquid metal lubrication, this paper presents the following experimental sliding friction characteristics in the sliding friction test. 1) The average coefficient of friction of the DLC-coated dimple specimen and dimple specimen are lower compared to that of a non-patterned specimen. 2) In the DLC-coated dimple specimens, the average coefficient of friction changes according to the change in the dimple density. 3) DLC-coated dimple specimens with a density of 12.5 have the lowest average coefficient of friction under 41.6 N of normal load and 143.3 RPM.

• Proceedings of the IEEK Conference
• /
• 2002.07a
• /
• pp.188-191
• /
• 2002

To reduce the bit-rate of video sequences by removing temporal redundancy, motion estimation techniques have been developed. However, the high computational complexity of the problem makes such techniques very difficult to be applied to high-resolution applications in a real time environment. For this reason, low computational complexity motion estimation algorithms are viable solutions. If a priori knowledge about the motion of the current block is available before the motion estimation, a better starting point for the search of n optimal motion vector on be selected and also the computational complexity will be reduced. In this paper, we present an adaptive block matching algorithm based on temporal correlations of consecutive image frames that defines the search pattern and the location of initial starting point adaptively to reduce computational complexity. Experiments show that, comparing with DS(Diamond Search) algorithm, the proposed algorithm is about 0.1∼0.5(㏈) better than DS in terms of PSNR and improves as much as 50% in terms of the average number of search points per motion estimation.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2004.10a
• /
• pp.818-821
• /
• 2004

With a rapid development in the area of micro and ultra precision technology, the micro surface machining of small size parts are explosively increased. Especially, to improve efficiency of various beams in lens and reflector, non-rotational symmetric form and several mm level heights changeable surface can be machined at a time. These geometric complex 3D surface cannot be machined by general short stroke FTS. The long stroke FTS if firmly needed to move directly several mm and have nm level positioning accuracy for the complex surface form. The long stroke FTS used linear motors to drive moving unit long and fine, aero static bearings to decrease friction and moving errors in guide way, optical linear scale with nm level resolution to measure position of FTS. Furthermore, to increase the performance of acceleration of FTS, the light material, such as AL is used for the structure and the high stiffness box type structure is selected. In this paper, the genetic algorithm approach is described to determine a set of design parameters for auto tuning. The authors have attempted to model the design problem with the objective of minimizing the error, such as variable pattern change. This method can give the better alternative than existing other method.

• Korean Management Science Review
• /
• v.32 no.1
• /
• pp.35-47
• /
• 2015

The purpose of this paper is to find an optimal weaving connection method of sweater threads while weaving intarsia sweater by the genetic algorithm. The objective function was devised to minimize labor cost and lessen the amount of thread usage. In order to create the parental population group in the genetic algorithm, we developed five thread connection methods. Besides, elite chromosome screening methods for the offspring group was selected both to the whole chromosome thread elite and to a color-coded elite thread chromosome. Commonly used diamond pattern in Intarsia sweater manufacturing was applied to the experiments. The experimental results showed that thread system saved the labor and material costs than woven method under the existing software. When weaving Intarsia sweater in the field, we can apply the developed genetic algorithm to improve productivity of weaving connection method.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.17 no.12
• /
• pp.1246-1253
• /
• 2007

The recent issue of optical pickup actuators is to apply optical storage devices to mobile devices such as a cellular phone and PDA. It requires actuators to become smaller than conventional types. As the size becomes smaller, the magnetic force is reduced and the assembly of optical pickup actuators becomes more difficult. In addition, its dynamic characteristics are changed. In this paper, methods to improve magnetic forces and dynamic characteristics are suggested and the optimal result of the plate spring design is obtained. A diamond shape magnet and the fine pattern coil (FPC) are used to improve magnetic forces and damping elements are attached to decrease the peak magnitude of the mode instead of using structural damping, mostly for the purpose of improving the accuracy of the finite element simulation. To get more stable dynamic characteristics than conventional ones, a plate spring is applied to the optical pickup actuator and it is optimized with topology and parameter optimization to obtain the concept and the detail design, respectively.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.44-44
• /
• 2011

현존하는 초경도 박막물질 중 입방정 질화붕소(cBN)은 철계 금속과의 반응안정성 및 낮은 온도에서의 합성가능성 등 많은 장점을 가지고 있다. 그러나 필수로 수반되는 이온충돌 효과로 인해 박막 내 높은 잔류응력으로 인한 박리 현상으로 응용이 어려운 실정에 있다. 현재까지 이를 개선하기 위해 수소를 첨가하여 박막의 잔류응력을 줄이는 연구, B4C 타겟을 이용하여 B-C-N 의 gradient layer를 설계하여 점진적으로 잔류응력을 감소시키는 연구 등 많은 연구들이 진행되고 있다. 본 연구에서는 MOCVD로 만들어진 NCD(Nano Crystalline Diamond) buffer layer 위에 RF-UBM(unbalanced magnetron) PVD를 이용하여 BN을 증착시켰다. hBN 타겟을 이용하여 2mTorr에서 400W 의 RF 파워를 사용하여 기판에 RF bias를 인가해 실험하였다. cBN 박막과 기판의 lattice mismatch 를 줄이기 위해서 본 연구소에서 제공되는 NCD 기판을 사용하였으며, 다이아몬드 기판과 cBN 박막의 1:1 에피성장을 이루기 위해 상온에서부터 800도까지 온도 변화를 주어 cBN을 증착시켰다. FTIR(Fourier transform infrared spectroscopy)로 $sp^2$구조인 hBN과 $sp^3$구조인 cBN의 성장유무를 확인하였으며, FTIR peak intensity 차이로 박막내 cBN의 함량을 계산하였고, Scratch test로 박막과 기판사이의 밀착력을 상대적으로 비교하였으며, 격자의 에픽성장을 확인하기 위해 FIB 의 작업을 거쳐 HRTEM 으로 각 위치별로 SAD pattern를 이용하여 성장거동을 확인하였다.