• 비파괴검사학회지
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• 제30권3호
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• pp.200-206
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• 2010

In ultrasound-excited thermography, the injected ultrasound to an object is transformed to heat and the appearance of defects can be visualized by thermography camera. The advantage of this technology is selectively sensitive to thermally active defects. Despite the apparent simplicity of the scheme, there are a number of experimental considerations that can complicate the implementation of ultrasound excitation thermography inspection. Factors including acoustic horn location, horn-crack proximity, horn-sample coupling, and effective detection range all significantly affect the detect ability of this technology. As conclusions, the influence of coupling pressures between ultrasound exciter and specimen was analyzed, which was dominant factor in frictional heating model.

• Transactions on Electrical and Electronic Materials
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• 제8권2호
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• pp.53-57
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• 2007

In this study, a novel slurry containing ceria as the abrasive particles was analyzed in terms of its frictional, thermal and kinetic attributes for interlayer dielectric (ILD) CMP application. The novel slurry was used to polish 200-mm blanket ILD wafers on an $IC1000_{TM}$ K-groove pad with in-situ conditioning. Polishing pressures ranged from 1 to 5 PSI and the sliding velocity ranged from 0.5 to 1.5 m/s. Shear force and pad temperature were measured in real time during the polishing process. The frictional analysis indicated that boundary lubrication was the dominant tribological mechanism. The measured average pad leading edge temperature increased from 26.4 to $38.4\;^{\circ}C$ with the increase in polishing power. The ILD removal rate also increased with the polishing power, ranging from 400 to 4000 A/min. The ILD removal rate deviated from Prestonian behavior at the highest $p{\times}V$ polishing condition and exhibited a strong correlation with the measured average pad leading edge temperature. A modified two-step Langmuir-Hinshelwood kinetic model was used to simulate the ILD removal rate. In this model, transient flash heating temperature is assumed to dominate the chemical reaction temperature. The model successfully captured the variable removal rate behavior at the highest $p{\times}V$ polishing condition and indicates that the polishing process was mechanical limited in the low $p{\times}V$ polishing region and became chemically and mechanically balanced with increasing polishing power.

• 소음진동
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• 제9권4호
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• pp.643-651
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• 1999

A brief description of the current technology (contact-start-stop) employed in most of today's hard disk drive is presented. The dynamics and head/disk interactions during a start/stop process are very complicated and no one has been able to accurately model the interactions. Thus, the head/disk interface that meets the start/stop durability and stiction requirements are always developed statistically. In arriving at a solution. many sets of statistical tests are run by varying several parameters. such as, the carbon overcoat thickness. lubricant thickness. disk surface roughness, etc. Consequently, the cost associated III developing an interface could be significant since the outcome is difficult to predict. An alternative method known as Load/Unload technology alters the problem set. such that. the start/stop performance can be designed in a predictable manner. Although this techno¬logy offers superior performance and significantly reduces statistical testing time, it also has some potential problems. However. contrary to the CSS technology. most of the problems can be solved by design and not by trial and error. One critical problem is that of head/disk contacts during the loading and unloading processes. These contact can cause disk and slider damage because the contacts are likely to occur at high disk speeds resulting in large friction forces. Use of glass substrate disks also may present problems if not managed correctly. Due to the low thermal conductivity of glass substrates. any head/disk contacts may result in erasure due to frictional heating of the head/disk interface. In spite of these and other potential problems. the advantage with L/UL system is that these events can be understood. analyzed. and solved in a deterministic manner.

• Tribology and Lubricants
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• 제29권6호
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• pp.372-377
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• 2013

This study investigated the interface temperatures for the sliding friction of three types of pins fabricated with thermocouple wires by the suction casting method. Optical microscopy was used to examine the surrounding material state at the bonding interface with the thermocouple wires. Friction tests were performed under dry sliding conditions against stainless steel 304 at nominal stresses of 1.42-4.25 MPa and sliding speeds of 0.5-1.25 m/s. Tribological data were collected using a custom-made pin-on-disk apparatus that measured the interface temperature and corresponding friction coefficient. Static tests were performed to demonstrate the functionality and reliability of the thermocouple wires-combined temperature sensor (TCTS). Each TCTS showed good linearity and sensitivity and very similar response times for the thermocouple and critical temperature during sliding friction.

• Tribology and Lubricants
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• 제10권3호
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• pp.29-38
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• 1994

The friction and wear of mild steel at dry sliding surfaces under different vacuum conditions have been investigated to understand the wear mechanisms. For the test, a ball-ondisk typed wear-rig has been built and implemented, allowing control of sliding speed, load and vacuum. Results show that, at a high sliding velocity, friction of low carbon steel (SS41) under a high vacuum is much higher than that of ambient condition and wear is much severer. It is due to lack of effective oxidation film formation on which steel surfaces could protect themselves against the severe wear. It has been shown, however, that there is a critical regime with contact conditions (at a low sliding velocity, a low load, and under a medium vacuum) at which effective, protective films of low carbon steel have been built on the surfaces in a friction process with a self-regulating way, resulting in both very low coefficients of friction (about 0.3) and mild wear. In order to investigate the protective films on steel surfaces, the worn surfaces and the wear debris have been experimentally analyzed with SEM, AES/SAM and XRD. A theoretical analysis of frictional heating at sliding surfaces, and an experimental analysis of the influence of oxidation wear under various vacuum conditions are described. The important variables on which self-formations of protective films at dry sliding surfaces depend, and the wear mechanisms are also investigated.

• 한국수소및신에너지학회논문집
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• 제10권1호
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• pp.41-48
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• 1999

산업단지에서 손실되는 막대한 폐열을 효율적으로 회수하고 이를 인근의 배후 도시에서 활용하기 위해서는 이에 적합한 열수송기술이 필요하다. 현재 온수나 증기에 의한 열수송은 배관을 통하여 열손실 및 마찰손실 등이 발생하므로 수송거리는 3 내지 5km가 한계이다. 그러나 대부분의 공단이 도시지역에서 10km 이상 떨어져 있으므로 이들 지역에서 발생되는 폐열을 적절히 활용하기 위해서는 새로운 열수송시스템이 개발되어야 한다. 본 연구에서는 수소저장합금이 수소를 흡수 또는 방출하면서 발열반응과 흡열반응을 일으키는 특성을 이용하여 산업공단지역의 폐열로부터 수소저장합금의 수소를 방출시키고, 이 수소를 인근 도시지역에 파이프라인으로 수송한 후 필요시 또 다른 수소저장합금과 반응시켜 열을 얻을 수 있는 열수송시스템에 대하여 고찰하였다. 이 시스템에서는 난방의 목적 외에도 수소의 흡수 방출온도가 낮은 합금을 이용하여 냉열을 얻을 수도 있으며, 폐열의 저장수단으로, 또한 수소를 수송함으로서 열수송의 수단으로 활용할 수 있다. 이에 따라 수소저장합금을 이용한 열수송기술의 문제점과 열수송시스템의 구성기술에 대하여도 검토하였다.

• 대한기계학회논문집A
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• 제36권7호
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• pp.723-730
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• 2012

상온의 인발공정에서 소재는 인발다이를 통과하면서 직경이 줄어들고 길이가 늘어난다. 인발다이와 소재가 접촉한 면에서의 압력과 미끄럼 운동에 의해 소재에는 탄성회복, 인발 다이에는 마찰과 마모가 생긴다. 또한, 소재의 변형 및 마찰열로 인해 소재와 다이의 온도가 상승하며 이로 인해 지정된 다이 내경으로 제품이 가공되기 어려우며 소재의 선경은 지정된 직경 또는 다이 내경과 다르게 된다. 본 논문에서는 다이의 온도분포를 고려하여 소재의 탄성회복, 다이의 탄성변형, 그리고 다이와 소재의 열변형이 인발제품의 선경변화에 미치는 영향을 정량적으로 분석하였다. 네 가지 요인 중에서 소재의 탄성회복의 영향이 선경변화량의 대부분을 차지함을 확인하였다. 선경변화에 영향을 주는 인자들을 고려하여 지정된 치수와 차이를 주지 않는 초기 다이를 설계하였고, 설계된 초기 다이를 이용하여 지정된 치수의 인발제품을 얻을 수 있었다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1096-1101
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• 2009

The plate heat exchanger(PHE) in heat pump has two flow streams of the refrigerant and water. The flow direction of the refrigerant, unlike that of water, can be changed by a 4-way valve depending on operating condition. Therefore the flow arrangement is a parallel flow for heating and a counter flow for cooling, respectively. In this study, the effects of the flow direction of the water on the heat transfer rate are investigated experimentally. The experiments are carried out for brazed plate heat exchangers under a parallel and counter flow conditions in evaporation and condensation. The experimental parameters in this study include the mass flux of the refrigerant 410A from 3 to $14\;kg/m^2s$ and the flow patterns for the pressure of PHE fixed at 0.97 and 2.46 MPa. The results show that both the heat transfer rate and frictional pressure drop across the PHE increase with the mass flux. The heat transfer rate of the refrigerant 410A for evaporation show great sensitivity to flow direction of the water. The heat transfer rate for evaporation with a counter flow are 5-30% higher than that with a parallel flow.

• 한국환경과학회지
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• 제15권10호
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• pp.919-928
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• 2006

The present study applied an atmospheric flow field model in Gwangyang-Bay which can predict local sea/land breezes formed in a complex terrain lot the development of a model that can predict short term concentration of air pollution. Estimated values from the conduct of the atmospheric flow field were used to evaluate and compare with observation data of the meteorological stations in Yeosu and the Yeosu airport, and the effect of micrometeorology of surround region by the coastal area reclamation was predicted by using the estimated values, Simulation results, a nighttime is appeared plainly land breezes of the Gwangyang-bay direction according to a mountain wind that formed in the Mt. of Baekwooun, Mt. of Youngchui. Land winds is formed clockwise circulation in the north, clockwise reverse direction in the south with Gangyang-bay as the center. Compared with model and observation value, Temperature is tend to appeared some highly simulation value in the night, observation value in the daytime in two sites all, but it is veil accorded generally, the pattern of one period can know very the similarity. And also, wind speed and wind direction is some appeared the error of observation value and calculation results in crossing time of the land wind and sea land, it can see that reproducibility is generally good, is very appeared the change land wind in the nighttime, the change of sea wind in the daytime. And also, according to change of the utilization coefficient of soil before and after development with Gwangyang-Bay area as the center. Temperature after development was high $0.55\sim0.67^{\circ}C$ in the 14 hoots, also was tend to appear lowly $0.10\sim0.22^{\circ}C$ in the 02 hours, the change of u, v component is comparatively tend to reduced sea wind and land wind, it is affected ascending air current and frictional power of the earth surface according to inequality heating of the generation of earth surface.

• Food Science and Biotechnology
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• 제14권3호
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• pp.305-310
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• 2005

Flaxseed is outstanding for lignans and oil rich in ${\alpha}$-linolenic acid which protect against several major illnesses. Better understanding of processing and storage characteristics of flaxseed will increase options for food use. Lignans and oil are found in the hull and embryo, respectively. Comparison of pearling and impact-dehulling processes for separation of lignan and oil-rich fractions showed the impact process was less effective, but easier to scale-up. Screw-pressing embryo reduced oil yield compared to whole seed, but doubled productivity and sharply reduced frictional heating of the oil. Flaxseed hull and embryo, also whole, ground and steamed-ground samples, were stable up to 30 weeks in closed containers at $23^{\circ}C$. Steamed-ground samples in open trays at $40^{\circ}C$ deteriorated markedly (peroxide value > 100 by 22 weeks); yet, whole seed remained stable. Incorporation of 18% flaxseed embryo into yellow perch feed increased ${\alpha}$-linolenic acid to 13 to l4% of muscle and liver lipids, compared to 0.5 to 0.7% in the no-embryo control. Feed conversion ratio, weight gain, and survival were similar. These studies are helping to establish the technological base for processing and utilizing flaxseed and flaxseed fractions to improve human diets.