• Nuclear Engineering and Technology
• /
• v.55 no.6
• /
• pp.2325-2334
• /
• 2023

To study the lubrication performance of tilting-pad thrust bearing (TPTBs) during start-up in nuclear pump, a hydrodynamic lubrication model of TPTBs was established based on the computational fluid dynamics (CFD) method and the fluid-structure interaction (FSI) technique. Further, a mesh motion algorithm for the transient calculation of thrust bearings was developed based on the user defined function (UDF). The result demonstrated that minimum film thickness increases first and then decreases with the rotational speed under start-up condition. The influence of pad tilt on minimum film thickness is greater than that of collar movement at low speed, and the establishment of dynamic pressure mainly depends on pad tilt and minimum film thickness increases. As the increase of rotational speed, the influence of pad tilt was abated, where the influence of the moving of the collar dominated gradually, and minimum film thickness decreases. For TPTBs, the circumferential angle of the pad is always greater than the radial angle. When the rotational speed is constant, the change rate of radial angle is greater than that of circumferential angle with the increase of loading forces. This study can provide reference for improving bearing wear resistance.

• Journal of the Korea Safety Management & Science
• /
• v.17 no.2
• /
• pp.235-240
• /
• 2015

Using a progressive die of the multi-stage drawing product, It was experiments for the Influence of the Products Roundness on the die pad process Safety die model, obstacle countermeasure research safety die design When the die pad is independent structure, Sidewall thickness of the inside 2stage, 3stage, 4stage of the product is thicker, the thickness of the inside 1stage and the bottom is thinner. it was become unstable beacuse the inside 1stage related to the Products Roundness is thinner. When the die pad is Integrated structure, Sidewall thickness of the inside 1stage, 2stage of the product is thicker, and Sidewall 3stage and 4stage was a thin. it was become unstable beacuse the inside 3stage related to the Products Roundness is thinner. Therefore, The appropriate combination of and integrated independent is required for each process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.12
• /
• pp.1027-1033
• /
• 2007

In this research, the polishing pad for W CMP has been analyzed to understand stabilization of polishing performance. For stabilization of process, the polishing pad condition is one of important factors. The polishing pad plays a key role in polishing process, because it contact with reacted surface of wafer[1]. The physical property of pad surface is ruled by conditioning tool which makes roughness and profile of pad surface. Pad surface affects on polishing performance such as RR(Removal Rate) and uniformity in CMP. The stabilized pad surface has stable roughness. And its surface has high level of wettability which can increase the probability of abrasive adhesion on pad. The result of this research is that the reduction of break-in and dummy polishing process were achieved by artificial machining to make stable pad surface. In this research, urethane polishing pad which is named IC pad(Nitta-Haas Inc.) and has micro pore structure, is studied. Because, this type of pad is the most conventional type.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.54-57
• /
• 2001

We studied the characteristics of polishing pad, which can apply STI-CMP process for global planarization of multilevel interconnection structure. Also, we investigated the effects of different sets of polishing pad, such as soft and hard pad. As an experimental result, hard pad showed center-fast type, and soft pad showed edge-fast type. Totally, the defect level has shown little difference, however, the counts of scratch was defected less than 2 on JRlll pad. Through the above results, we can select optimum polishing pad, so we can expect the improvements of throughput and devise yield.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.5
• /
• pp.32-37
• /
• 2004

Polishing processes are widely used in the glass, optical, die and semiconductor industries. Chemical Mechanical Polishing (CMP) especially is becoming one of the most important ULSI processes for the 0.25m generation and beyond. CMP is conventionally carried out using abrasive slurry and a polishing pad. But the surface of the pad has irregular pores, so there is non-uniformity of slurry flow and of contact area between wafer and the pad, and glazing occurs on the surface of the pad. This paper introduces the basic concept and fabrication technique of the next generation CMP pad using micro-molding method to obtain uniform protrusions and pores on the pad surface.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.1
• /
• pp.114-121
• /
• 2015

In conventional LEDs, a mesa-structure is usually used and it causes the current to be overcrowded in a specific region. We propose a novel structure of GaN-based LED to overcome this problem. In order to distribute the current in an active region, a spreading pad is inserted at the p-type region in the GaN based LED device. The inserted spreading pad helps the current flow because it is more conductive than the p-type GaN layer. By performing electrical and optical simulations, the effects of the spreading pad insertion are confirmed. The results of electrical simulation show that the current spreads more uniformly and more radiative recombination is produced as well. Moreover, from the optical simulation, it is revealed that the ITO is less absorptive material than p-GaN if the condition of specific wavelength sources is satisfied. Considering all of the results, we can conclude that the luminescent power is enhanced by the spreading pad.

• Advances in Traditional Medicine
• /
• v.10 no.4
• /
• pp.319-321
• /
• 2010

Plant saponins are widely distributed amongst plants and have a wide range of biological properties. Icosahydropicenic acid, $C_{51}H_{80}O_{19}$ ((4S,6bS)-8a-((4,5-dihydroxy-6-methyl-3-((3R)-3,4,5-trihydroxy-6-methyl-tetrahydro-2H-pyran-2-yloxy)-tetrahydro-2H-pyran-2-yloxy)carbonyl)-2-hydroxy-4, 6a, 6b, 11, 14b-pentamethyl-11-(2-methylprop-1-enyl)-3-(3,4,5-trihydroxy-6-(hydroxymethyl) - tetrahydro-2Hpyran-2-yloxy)-1, 2, 3, 4, 4a, 5, 6, 6a, 6b, 7, 8, 8a, 9, 10, 11, 12, 12a, 14, 14a, 14b-icosahydropicene-4-carboxylic acid), a new saponin was first time isolated from the roots of Clerodendrum Serratum (L) Moon (Verbenaceae). The structure elucidation of the compound was carried out by $^1H$ NMR and DART-MS studies.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.445-446
• /
• 2002

The purpose of this study was to investigate the effect of micro holes, pattern structure and elastic modulus of pads on the polishing behavior such as the removal rate and WIWNU (within wafer non-uniformity) during CMP. The regular holes on the pad act as the superior abrasive particle's reservoir and regular distributor at the bulk pad, respectively. The superior CMP performance was observed at the laser processed bulk pad with holes. Also, th ε groove pattern shape was very important for the effective polishing. Wave grooved pad showed higher removal rates than K-grooved pad. The removal rate was linearly increased as the top pad's elastic modulus increased.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.41 no.5
• /
• pp.939-949
• /
• 2017

This study uses 3D printing technology to design and fabricate a fall impact protection pad with a spacer fabric structure. The design of the pads consists of hexagonal three-dimensional units connected in a honey-comb shape; in addition, the unit consists of a surface layer and a spacer layer. Protect pads were designed as either a hexagonal type or diamond type according to the surface layer structure; subsequently, a spacer filament was also designed as the most basic I-shape type. Designed pads were printed using four types of flexible filaments to select suitable material for a fall impact protection pad. Impact protection performance and bending stiffness were evaluated for the eight type of pad outputs. As a result of the impact protection performance evaluation, when the force of 6,500N was applied, the force passed through the pad was in the range of 1,370-2,132N. FlexSolid$^{(R)}$ and Skinflex$^{TM}$ showed good protection performance and cubicon flexible filament showed the lowest protection. NinjaFlex$^{(R)}$ was found to be the most flexible in the bending stiffness evaluation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.356-357
• /
• 2005

Chemical mechanical polishing (CMP) allows the planarization of wafers with two or more materials at their surfaces. Especially, polishing pad is considered as one of the most important consumables because of its properties. Subject of this investigation is to apply CMP for planarization of shallow trench isolation structure using microstructure pad. Microstructure pad is designed to have uniform structure on its surface and fabricated by micro-molding technology. And then STI CMP performances such as oxide dishing and nitride corner rounding are evaluated.