• Journal of Sensor Science and Technology
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• v.16 no.5
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• pp.325-330
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• 2007

For the application to optic devices, wafer level package including spacer with particular thickness according to optical design could be required. In these cases, the uniformity of spacer thickness is important for bonding strength and optical performance. Packaging process has to be performed at low temperature in order to prevent damage to devices fabricated before packaging. And if photosensitive material is used as spacer layer, size and shape of pattern and thickness of spacer can be easily controlled. This paper presents polymer bonding using thick, uniform and patterned spacing layer of SU-8 2100 photoresist for wafer level package. SU-8, negative photoresist, can be coated uniformly by spin coater and it is cured at $95^{\circ}C$ and bonded well near the temperature. It can be bonded to silicon well, patterned with high aspect ratio and easy to form thick layer due to its high viscosity. It is also mechanically strong, chemically resistive and thermally stable. But adhesion of SU-8 to glass is poor, and in the case of forming thick layer, SU-8 layer leans from the perpendicular due to imbalance to gravity. To solve leaning problem, the wafer rotating system was introduced. Imbalance to gravity of thick layer was cancelled out through rotating wafer during curing time. And depositing additional layer of gold onto glass could improve adhesion strength of SU-8 to glass. Conclusively, we established the coating condition for forming patterned SU-8 layer with $400{\mu}m$ of thickness and 3.25 % of uniformity through single coating. Also we improved tensile strength from hundreds kPa to maximum 9.43 MPa through depositing gold layer onto glass substrate.

• Horticultural Science & Technology
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• v.18 no.3
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• pp.387-390
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• 2000

The experiment was conducted to investigate the effects of vine management and yield on fruit quality and bud burst of 'Campbell Early' grapevines in Hwaseong and Suwon area. The extreme value of minimum temperature of Hwaseong area, frequently causing cold damage, was lower than that of Suwon area in winter. Narrow spacing, overbearing, and poor vine management were observed in Hwaseong area, where the harvest time was delayed by 7 days compared with that of Suwon area. Total carbohydrate content of bearing mother branches was lower with 1.2~1.7%, and the percentage of bud burst was extremely lower at $-15^{\circ}C$. In Suwon area, there were no differences in cluster and berry size, but soluble solids content was lower and skin coloration was poorer when yield was high. Total carbohydrate content was lower when yield was high. The percentage of bud burst was lower at cold treatments below $-20^{\circ}C$. The results suggest that appropriate yield based on fruit quality is 2.3~2.6 MT/10a.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.2
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• pp.47-53
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• 2014

The paper investigates the limit state of deflection for short and medium span steel girder bridges. Deflection depends on stiffness of steel girders and integrity of the reinforced concrete slab (composite action). Load and resistance parameters are treated as random variables. A probabilistic model is developed for prediction of the deflection. The structural performance can be affected by deterioration of components, in particular corrosion of steel girders. In addition, the creep of concrete can greatly influence the deflection of composite structures. Therefore, the statistical models for creep and corrosion of structural steel are incorporated in the model. Structures designed according to the AASHTO LRFD Code are considered. Load and resistance models are developed to account for time-variability of the parameters. Monte Carlo simulations are used to estimate the deflections and probabilities of serviceability failure. Different span lengths and girder spacing are considered for structures designed as moment-controlled and deflection-controlled. A summary of obtained results is presented.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.108-113
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• 2018

Researches on strengthening and rehabilitation methods are being widely conducted due to the deterioration of existing concrete structures. Use of externally bonded Carbon Fiber Reinforced Polymers (CFRP) strips for the rehabilitation is a cost-effective and time-saving method. Generally, the CFRP layout for the shear strengthening was a uni-directional layout. Many researches have focused on the variables of the uni-directional CFRP layout such as the amount of material, angle, and spacing. Pilot tests indicated that the effective confinement of the concrete member can be provided with the bi-directional CFRP layout than the uni-directional layout. Therefore, the test was carried out after the uni- and bi-directional strengthening work using the same amount of CFRP material. CFRP anchors were installed to prevent unexpected premature CFRP delamination failure before reaching CFRP fracture strain. The effectiveness of the CFRP anchor and bi-directional CFRP layout for shear strengthening was verified based on the principal tensile strain contours.

• Journal of Periodontal and Implant Science
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• v.32 no.4
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• pp.711-719
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• 2002

Background : Terminology is a good index of reflections in conceptional imaginations, trends and technological advances in the field of their own. The purpose of this study is to compare the similarity and difference of terms in periodontology to evaluate the communicability between South and North Korea. These result may be particularly helpful for making glossary, academic communication and social unity at the time of reunion. Methods : This study was carried out by searching northern periodontology terminologies used in literatures published in North Korea and comparing those terms with the southern terms. The standard northen terms were not able to be distinguished, so the terms used frequently were chosen as the standard northern terms. Results : The South and North both use terms that stem from Chinese characters, but this tendency is stronger in the South. The main differences between the South and North are due to the North Korea's effort in converting terms into the native languages. There are also some differences in inscription of foreign language, spelling and spacing, and so on. Conclusion : The terminology using in South and North Korea in the field of periodontology is somewhat different but both side can be capable of communication. Now the basic efforts in both parts must be taken, such as establishing new terms, in order to relieve these differences.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.65-70
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• 2000

It is blown that the loudness is one of the most important metrics in assessing the sound quality and a calculation method for loudness has been standardized for steady sounds. In this study, a new loudness model is suggested for dealing with the transient sound for a unified analysis of various practical sounds. A signal processing technique is introduced for this purpose, which is required for the band subdivision and the prediction of band-level change of transient sounds. In addition, models for the post-masking and the temporal integration are adopted in the analysis of the loudness of transient sounds. In order to solve the problem of the conventional loudness model in the pure-tone signal processing, a critical band filter is employed in the analysis, which consists of 47 critical filters having a filter spacing of a half of the critical bandwidth. For testing the effectiveness of the present model, the predicted responses are compared with the experimental data and it is observed that they are in good agreements.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.303-310
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• 2002

Overbreak occurred inevitably in a tunnel excavation, Is the main factor for increasing cost and time in tunnel projects. Furthermore the damage to the remained rock mass related to the overbreak can give rise to a serious safety problem in tunnels. As a rule of thumb, causes for the overbreak are inaccuracy in drilling, the wrong design of blasting and selection of explosives, and heterogeneity in rock mass. Specially, the geological features of the rock mass around periphery of an excavation are very important factors, so a lot of researches have been conducted to describe these phenomena. But the quantitative geological classification of the rock mass for the overbreak and the method for decreasing the amount of the overbreak have not been established. Besides, the technical improvement of the charge method is requested as explosives for the smooth blasting have not functioned efficiently. In this study, the working face around periphery of an excavation has been continuously sectionalized to 5∼6 parts, and the new Blastability Index for the overbreak based on 6 factors of RMD(Rock Mass Description), UCS(Uniaxial Compressive Strength) JPS(Joint Plane Spacing), JPO(Joint Plane Orientation), JPA(Joint Plane Aperture) and FM(Filling Material) is proposed to classify sections of the working face. On the basis of this classification, the distance between contour holes and the charging density are determined to minimize the overbreak. For controlling the charging density and improving the function of explosives, the New Deck Charge(N.D.C) method utilizing the deck charge method and detonation transmission in hole has been developed.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.945-948
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• 2008

Nanocomposite materials provides efficient reinforcement, thermal endurance, and many other advantages depending on the additives used, with applications in the aerospace, automotive, and biomedical industries. Here, epoxy based nanocomposites were synthesized in the presence of Cloisite 15A and characterized with TEM, XRD, TGA, and DMA. To determine the effect of the clay d-spacing, Cloisite 20A was also used to synthesize the nanocompostes. In addition to the traditional hot plate method, an ultrasonicator was used to investigate the effect of different types of mixing on the properties of the nanocomposite; no significant effect was found. An examination of the nanocomposite morphology revealed that all the nanocomposites synthesized yielded an intercalated structure. When 5 wt% of Cloisite 15A was used with 20 min sonication time, the storage modulus increased 10% over the neat(no clay) nanocomposite. In general, the presence of Cloisite 15A produced a better storage modulus than Cloisite 20A.

• Journal of the Korean Society of Propulsion Engineers
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• v.6 no.1
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• pp.47-54
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• 2002

This paper presents the results of an experimental investigation on the combustion of single droplets and 1-D droplet arrays of jet A-1 fuel droplets in atmospheric pressure. Experimental results indicate that burning rate constants$({\kappa}_c)$ of jet A-1 fuel droplets were independent of initial droplet size as $0.915{mm}^2$/sec. It was acquired a general relationship expressing the variation of $d^2$ with time for droplet burning For 1-D droplet arrays $(l/d_o$=1.208{\sim}2.922)$/TEX>, the burning rate constant ${\kappa}_c$ decreased with decreasing droplet spacing $l/d_o$ and, The effect on combustion rate constant ${\kappa}_c$ was stronger to second fuel droplet than third fuel droplet with uniform droplet distance

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.16-23
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• 2006

This paper presents the development of the fast Direction Finder using direct conversion method, which can intercept for short pulse signal of less' than 1 msec. in RF Down Converter, and CVDF(Correlative Vector Direction Finding) algorithm, which estimates DoA (Direction of Arrival). The configuration and characteristics of direction finder using 5-channel equi-spaced circular array antenna are presented and the direct conversion techniques for removing tuning time using I/Q demodulator are described. The CRLB of our model is derived, the principles of 2 kind of CVDF algorithm are explained and their characteristics are compared with CRLB w.r.t the number of samples and spacing ratio. The RF Down Converter prototype using direct conversion method is manufactured, the 2 kind of CVDF algorithm are applied and their performance are analyzed. Finally it is confirmed the LSE based CVDF algorithm is better than correlation-coefficient based except for ambiguity protection capabilities.