• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.26-26
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• 2003

During fabrication process for the large space optical surfaces, the traditional bound abrasive grinding with bronze bond cupped diamond wheel tools leaves the machine marks and the subsurface damage to be removed by subsequent loose abrasive lapping. We explored a new grinding technique for efficient quantitative control of precision CNC grinding for space optics materials such as Zerodur. The facility used is a NANOFORM-600 diamond turning machine with a custom grinding module and a range of resin bond diamond tools. The machining parameters such as grit number, tool rotation speed, work-piece rotation speed, depth of cut and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis methods. The effectiveness of the grinding prediction model was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment details, the results and implications are presented.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.29-33
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• 2012

The demand for 3D wafer level integration has been increasing significantly. Although many technical challenges of wafer stacking are still remaining, wafer stacking is a key technology for 3D integration due to a high volume manufacturing, smaller package size, low cost, and no need for known good die. Among several new process techniques Cu-to-Cu wafer bonding is the key process to be optimized for the high density and high performance IC manufacturing. In this study two main challenges for Cu-to-Cu wafer bonding were evaluated: misalignment and bond quality of bonded wafers. It is demonstrated that the misalignment in a bonded wafer was mainly due to a physical movement of spacer removal step and the bond quality was significantly dependent on Cu bump dishing and oxide erosion by Cu CMP.

• Journal of the Korean Wood Science and Technology
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• v.48 no.3
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• pp.393-404
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• 2020

This study examined the material properties of MDF manufactured using acetylated pinus radiata fibers against moisture and compared the properties with the fiberboard quality standards of KS F 3200. Since acetylated MDF shows very low moisture content, water absorption and thickness swelling than the quality standards, it is expected to have an excellent dimensional stability. The bending strength in wetting condition of the acetylated MDF reached approximately 70% of the bending strength in dry condition, making it suitable for the quality standards. The internal bond of the acetylated MDF in the wetting condition was higher than the minimum internal bond of the quality standards in the dry condition, showing a good water resistance. Since the water droplet contact angle of the acetylated MDF is larger than that of untreated MDF, it is determined that it contributes in improving the water resistance due to the low wettability.

• Journal of Ginseng Research
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• v.31 no.1
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• pp.34-43
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• 2007

Background: Previous research has suggested that single doses of a standardised Panax ginseng extract can decrease fasted blood-glucose levels and modulate cognitive performance in healthy young volunteers. The latter has generally been seen in terms of improved secondary memory performance. However, both the cognitive effects of chronic administration of ginseng and the potential modulation of working memory have received comparatively little research attention. Aims: The current double-blind, placebo-controlled, balanced cross-over study investigated the effects of 8-weeks administration of Korean ginseng extract (200 mg) on cognitive performance, gluco-regulatory parameters and ratings of subjective mood and 'quality of life'. Methods: 'Eighteen healthy young participants were assessed pre-dose and 3 hours post-dose on the mornings of Day 1, Day 29 and Day 57 of 8 week treatment regimens of both placebo and ginseng. A four-week placebo wash-out separated the treatment phases. Each assessment included the Cognitive Drug Research battery, computerised working memory tasks, and Bond-Lader mood scales. The WHO Quality of Life scale (WHOQOL-BREF) was completed once per visit. Gluco-regulatory parameters were assessed with assays of blood glucose, insulin and HbA1c. Results: Data from the 16 participants that completed the study showed that there were no significant, acute treatment related differences on Day 1 of treatment, or in gluco-regulatory parameters throughout the study. However, time related performance improvements were evident following chronic administration of ginseng on the '3-Back' and 'Corsi-block' computerised working memory tasks. Ginseng was also associated with an improved score on the 'social relations' subscale of the WHOQOL-100, and a significant shift on the 'calm' factor of the Bond-Lader mood scales (from calm/relaxed towards excited/tense). Conclusion: The results of the current study suggest that Korean ginseng extract can modulate working memory performance and subjective ratings of 'quality of life' and mood. Replication with a larger sample size may further elucidate the actions of this product.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.3
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• pp.328-335
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• 2000

Statement of the problem. Recently an innovative method of fabricating indirect restorations by gold electroforming has been developed. But the bond quality and strength of the gold coping to the porcelain is uncertain. Purpose of study. The purpose of this study is to analyze and evaluate the electroformed gold surface for mechanical bonding between the gold and the ceramic veneering. Methods/material. Electroformed disks were made using electroforming technique. And the surface of the electroformed coping was analyzed after sandblasting, heat-treatment, bonding agent application, opaque porcelain firing with scanning electron microscopy and energy dispersive x-ray analysis. Results. In the analysis with SEM, Sandblasting made the sharp edges and undercuts on the electroformed surface, and after bonding agent application, net-like structure were created on the electroformed surface. In the energy dispersive x-ray analysis it is confirmed that electroformed surface contains some impurities. Conclusion. With the use of sandblasting and bonding agent, electroformed surface seems to be enough to bond with veneering porcelain.

• Journal of Welding and Joining
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• v.19 no.5
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• pp.512-519
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• 2001

Sink roll has been used in molten Zn-0.2%Al alloy bath of continuous galvanizing line in sinking and stabilizing process of the steel strip in molten metal bath. In this process, although the scraper scraps off the sink roll surface, the dross compounds is builded up on the sink roll surface and the life time of the sink roll is shorten by the dross compounds. The present study was investigated the application of the spray coating layer on sink roll body for improving durability In molten Zn-0.2%Al alloy. Through the durability tests in molten Zn-0.2%Al alloy with various ceramic and cermet coating layer, the optimum bond and top coating material was obtained. As the results, the system of STS430F base metal, WC-l7Co bond and $ZrO_2-SiO_2$ top coating was clarified to be the best quality of durability in molten Zn-0.2%Al alloy.

• Journal of Welding and Joining
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• v.14 no.2
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• pp.71-78
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• 1996

In order to rpovide proper SMT design criteria in a systematic way, a mathematical formulation has been developed to predict the configuration of the solder fillet formed between the gullwing type lead and rectangular pad. Effects of SMT design parameters such as the solder volume and pad dimension on the solder profile are investigated using the FEM that calculates the 3D configuration by minimizing the energy due to surface tension and gravity in the equilibrium state. Design criteria of QFP and SOP are illustrated by plotting the acceptable range of the solder volume with respect to the length and width ratios of the pad and lead. The results show that the acceptable design range increases with increase in the pad length and width. The pad length has more significant effects on design criteria compared with the pad width, and Bond number can be utilized to predict the joint quality.

• Journal of the Korean Ceramic Society
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• v.45 no.5
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• pp.251-255
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• 2008

Microwave dielectric properties of $MgTiO_3,\;MgWO_4,\;MgNb_2O_6$, and $MgTa_2O_6$ were investigated based on the structural characteristics. The dielectric constant (K) was dependent on the dielectric polarizabilities of the specimens, and the deviation of the observed dielectric polarizabilities (${\alpha}_{obs.}$) from the theoretical dielectric polarizabilities (${\alpha}_{theo.}$) were decreased with increasing of Mg-site bond valence. Quality factors (Qf) were affected by the sharing type of $MgO_6$ and $BO_6$ octahedra. Temperature coefficient of resonant frequency (TCF) was decreased with increasing of average octahedral distortion.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.305-307
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• 2004

One set of rotor coils is required per each large generator rotor assembly, Rotors consist of two directly opposing poles. Each pole requires from 5 to 9 coils. Each coil is made up of two halves identified on the connection end. These coil halves will be joined together by butt brazing process during subsequent rotor assembly. Each half coil is made up of typically 4 to 9 layers of copper conductors. Because of Generator rotor is rotated very high speed with 3,600RPM, the quality soundness of brazed joints is very important at each coil. But, it is very difficult to be optimized non-destructive evaluation, because c-coil has the long shape and evaluation is to be done assembled condition. In this paper introduce newly developed inspection process and acceptance standards for the ultrasonic inspection of " C" coil butt braze. This inspection system is a semi-automatic ultrasonic flaw detector with data acquisition and retention capable of assessing the relative lack of bond of brazed butt joints

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.329-329
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• 2000

In this paper, a spindle system using an electromagnetic exciter is proposed to compensate a spindle disturbance such as unbalance and machining force etc A spindle compliance can be readily varied with a disturbance which is generated by the interact ion between the spindle / workpiece structure and the cutting process dynamics. The varied compliance is one of the major constraints that deteriorates the surface quality of workpiece. This paper suggests a compliance compensation by using the EME in the proposed spindle system. To compensate the varied compliance, firstly a spindle system modeling was conducted by using the bond graph. Then the model is simulated by numerical analysis method and an optimal EME position is determined to compensate a disturbance effectively through simulation, which makes the bearing load to be minimized