• International Journal of Highway Engineering
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• v.16 no.4
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• pp.21-33
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• 2014

PURPOSES: The purpose of this study was to break away from the workforce method using cold-mix asphalt mixtures and has a constant quality and has develop repair materials of pre-production asphalt-precast types. METHODS: The selection of the repair material was determined as the results obtained through physical properties of materials and the field applicability. In case of repair materials, values obtained through Marshall stability test & the dynamic stability test & retained stability test as well as the site conditions was considered. In case of adhesive, test results were obtained through examination of the bond strength(tensile, shear) and the field applicability of the adhesive was examined through combined specimens to simulate field applications. RESULTS : According to the results of laboratory tests, in the case of repair materials, Marshall stability and dynamic stability, retained stability of cold-mix reaction type asphalt mixture is the highest. In the case of adhesive, two-component epoxy-urea has a very high bonding strength(tensile, shear) was most excellent. According to the results of field tests, when epoxy-urea was excellent workability. Also, the repair body through actual mock-up test did not occur large deformation and fracture after 12 months. CONCLUSIONS : A suitable repair material is cold-mix reaction type mixture of asphalt-precast, a suitable adhesive is a two-component epoxy-urea.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.75-75
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• 1996

The rapid expansion for the auto-industry and the worldwide trend toward non-asbestos friction materials for brake lining force our industry to transfer into non-asbestos ones from asbestos-based friction materials. Furthermore, it is imperative for the friction materials to have technological excellence and lower production cost to be competitive in the world market. There is no known theoretical procedures to formulate friction materials. It, rather, depends on the trial and error process. Thus, it is quite clear how important it is to accumulate the know-how on the formulation and manufacturing the friction material. This study concerns the practical ways of conceptualizing the formulation and optimizing the manufacturing process. This study focused on the development of formulation for non-asbestos friction material as well as deriving the physical properties of the trial product to prove its validity and applicability. Elaboration of the formula and optimizing scheme of the manufacturing process to get better quality are also sought. Physical properties were obtained by constant velocity test dynamotest, hardness test and strength test. Differential scanning calorimeter was also used to analyze the thermal reactions of organic constituents, microstructures, bond effects, and degree of mixture.

• Journal of Advanced Marine Engineering and Technology
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• v.20 no.2
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• pp.7-14
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• 1996

The rapid expansion for the auto-industry and the worldwide trend toward non-asbestos friction materials for brake lining force our industry to transfer into non-asbestos ones from asbestos-based friction materials. Furthermore, it is imperative for the friction materials to have technological excellence and lower production cost to be competitive in the world market. There is no known theoretical procedures to formulate friction materials. It, rather, depends on the trial and error process. Thus, it is quite clear how important it is to accumulate the know-how on the formulation and manufacturing the friction material. This study concerns the practical ways of conceptualizing the formulation and optimizing the manufacturing process. This study focused on the development of formulation for non-asbestos friction material as well as deriving the physical properties of the trial product to prove its validity and applicability. Elaboration of the formula and optimizing scheme of the manufacturing process to get better quality are also sought. Physical properties were obtained by constant velocity test dynamotest, hardness test and strength test. Differential scanning calorimeter was also used to analyze the thermal reactions of organic constituents, microstructures, bond effects, and degree of mixture.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.211.1-211.1
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• 2014

Recently, the scaling of conventional planar NAND flash devices is facing its limits by decreasing numbers of electron stored in the floating gate and increasing difficulties in patterning. Three-dimensional vertical NAND devices have been proposed to overcome these issues. Atomic layer deposition (ALD) is the most promising method to deposit charge trap layer of vertical NAND devices, SiN, with excellent quality due to not only its self-limiting growth characteristics but also low process temperature. ALD of silicon nitride were studied using NH3 and silicon chloride precursors, such as SiCl4[1], SiH2Cl2[2], Si2Cl6[3], and Si3Cl8. However, the reaction mechanism of ALD silicon nitride process was rarely reported. In the present study, we used density functional theory (DFT) method to calculate the reaction of silicon chloride precursors with a silicon nitride surface. DFT is a quantum mechanical modeling method to investigate the electronic structure of many-body systems, in particular atoms, molecules, and the condensed phases. The bond dissociation energy of each precursor was calculated and compared with each other. The different reactivities of silicon chlorides precursors were discussed using the calculated results.

• Journal of electromagnetic engineering and science
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• v.9 no.1
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• pp.25-31
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• 2009

This paper describes CMOS VCO circuit design procedures and techniques for multi-band/multi-standard RF transceivers. The proposed techniques enable a 4 GHz CMOS VCO to satisfy all requirements for Quad-band GSMIEDGE and WCDMA standards by achieving a good trade-off among important specifications, phase noise, power consumption, modulation performance, and chip area efficiency. To meet the very stringent GSM T/Rx phase noise and wide frequency range specifications, the VCO utilizes bond-wire inductors with high-quality factor, an 8-bit coarse tune capbank for low VCO gain(30$\sim$50 MHz/V) and an on-chip $2^{nd}$ harmonic noise filter. The proposed VCO is implemented in $0.13{\mu}m$ CMOS technology. The measured tuning range is about 34 %(3.17 to 4.49 GHz). The VCO exhibits a phase noise of -123 dBc/Hz at 400 kHz offset and -145 dBc/Hz at 3 MHz offset from a 900 MHz carrier after LO chain. The calculated figure of merit(FOM) is -183.5 dBc/Hz at 3 MHz offset. This fully integrated VCO occupies $0.45{\times}0.9\;mm^2$.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.988-989
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• 2006

The ultrasonic welding is with features of high electric conductivity and hot conductivity when it is used in metallic bond, high electric conductivity and hot conductivity when it is used in various metallic bonds, excellent quality when it is used for advanced junction, easiness when it is used in various metallic bonds, being needless for the exhaustive material and being benefit for the environment. Currently the use of ultrasonic welding is increasing in the industrial fields such as the automobile battle, the refrigerator, the air conditioner, the battery and the solar cell junction. But the production ability is insufficient in our country and it is necessary to explore the core technology of the ultrasonic welding. In this paper, the output LC resonance filter and 35kHz squal wave onion occurrence Full Bridge plans was designed. The output examination of the ultrasonic oscillator and the ultrasonic welding examination were done. The method for getting more smooth result in the ultrasonic welding machine system was researched.

• Structural Engineering and Mechanics
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• v.53 no.6
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• pp.1083-1104
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• 2015

This paper provides the results of an experimental investigation into the flexural behavior of continuous two-span unbonded post-tensioned high strength concrete (HSC) beams, strengthened by end-anchored CFRP laminates of different configurations in the hogging region. Implementing two different configurations of end-anchorage systems consisting of steel plates and bolts and carefully monitoring the development of strains throughout the load history using sufficiently large number of strain gauges, the response of beams including the observed crack propagations, beam deflection, modes of failure, capacity enhancement at service and ultimate and the amount of moment redistribution are measured, presented and discussed. The study is appropriate in the sense that it covers the more commonly occurring two span beams instead of the simply supported beams investigated by others. The experiments reconfirmed the finding of others that proper installation of composite strengthening system is most important in the quality of the bond which is essential for the internal transfer of forces. It was also found that for the tested two span continuous beams, the capacity enhancement is more pronounced at the serviceability level than the ultimate. This is an important finding as the design of these beams is mostly governed by the serviceability limit state signifying the appropriateness of the suggested strengthening method. The paper provides quantitative data on the amount of this capacity enhancement.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.1
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• pp.38-45
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• 2002

Evaporative heat transfer characteristics of carbon dioxide have been investi- gated by experiment. The experiments have been carried out for a seamless stainless steel tube of the outer diameter of 9.55 mm, the inner diameter of 7.75 mm and the length of 5.0 m. Direct heating method was used for supplying heat to the refrigerant where the test tube was uniformly heated by electric current which was applied to the tube wall. Experiments were conducted with$CO_2$of purity 99.99% at saturation temperatures of 0.0 to 10.5$^{\circ}C$, heat fluxes of 12 to 27kW/$m^2$s and mass fluxes of 212 to 530 kg/$m^2$s. The heat transfer coefficients of $CO_2$are decreased as the vapor quality increases and these phenomena are explained by dimensionless Weber and Bond numbers. The heat transfer coefficients of$CO_2$increase when the heat and mass fluxes increase, and the saturation temperature effects are minor in the test range of this study. The present experimental data are compared with six renowned correlations with root-mean-squared deviations ranging from 23.0 to 94.9% respectively.

• Journal of the Korea Institute of Building Construction
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• v.14 no.2
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• pp.163-169
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• 2014

Engineers in the construction field have been using bonded waterproofing sheets in an attempt to resolve the imbalance in the quality, the risk of fire, safety of workers, and environmental pollution, as well as to eliminate separate use of organic adhesives on the surface of concrete. Recently, self-laminated waterproofing sheets have been developed. The purpose of this research is to find an appropriate processing speed according to the changes in physical properties, and visual observation of the waterproofing sheets laminated by the aluminum thin-film and viscosity layer that can be attached through self-adhesiveness on the surface of concrete and waterproofing sheets. Therefore, this research is conducted using a physical performance test. Based on the result of the test, when the high-frequency inductive heating apparatus was used, an improved adhesion and bonding stability effect were confirmed after the anti-hydrostatic pressure and bond strength in the temperature condition, and the surface observation in the processing speed condition.

• Advances in concrete construction
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• v.11 no.3
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• pp.261-270
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• 2021

In this study, a new understanding is presented on the microcracking behavior of high strength concrete (HSC) with steel fiber addition having prior compressive loading history. Microcracking behavior at critical stress (σcr) region, using seven fiber addition volume of 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, and 2.0% was evaluated, at two aspect ratios (60 and 75). The specimens were loaded up to a specified compressive stress levels (0.70fc-0.96fc), and subsequently subjected to split tensile tests. This was followed by microscopic analyses afterwards. Four compressive stress levels as percentage of fc were selected according to the linearity end point based on stress-time (σ-t) diagram under uniaxial compression. It was seen that pre-compression has an effect on the linearity end point as well as fiber addition where it lies within 85-91% of fc. Tensile strength gain was observed in some cases with respect to the 'maiden' tensile strength as oppose to tensile strength loss due to the fiber addition with teething effect. Aggregate cracking was the dominant failure mode instead of bond cracks due to improved matrix quality. The presence of the steel fiber improved the extensive failure pattern of cracks where it changes from 'macrocracks' to a branched network of microcracks especially at higher fiber dosages. The applied pre-compression resulted in hardening effect, but the cracking process is similar to that in concrete without fiber addition.