• Wind and Structures
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• v.32 no.2
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• pp.89-104
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• 2021

Non-synoptic winds generated by tornadoes, downbursts or gust fronts exhibit significant non-stationarity and can cause significant wind load effect on flexible structures such as long-span bridges. However, conventional assumptions on stationarity used to evaluate the structural wind-induced vibration are inadequate. In this paper, an efficient frequency domain scheme based on fast CQC method, which can predict non-stationary buffeting random responses of long-span bridges, is presented, and then this approach is applied to evaluate the buffeting response of a long-span suspension bridge located in a complex mountainous wind environment as an example. In this study, the data-driven method based on one available measured wind speed sample is firstly presented to establish non-stationary wind models, including time-varying mean wind speed, time-varying intensity envelope function and uniformly modulated fluctuating spectrum. Then, a linear time-variant (LTV) system based on the proposed scheme can be generally applied to calculate the non-stationary buffeting responses. The effectiveness and accuracy of the proposed scheme are verified through Monte Carlo time domain simulation implemented in ANSYS platform. Also, the transient effect nature of the bridge responses is further illustrated by comparison of the non-stationary, quasistationary and steady-state cases. Finally, buffeting response analysis with traditional stationary treatment (10 min constant mean plus stationary wind fluctuation) is performed to illustrate the importance of the non-stationary characteristics embedded in original wind speed samples.

• Korean Management Science Review
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• v.32 no.4
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• pp.155-173
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• 2015

Koreatech has adopted a long-term co-op program called IPP (Industry Professional Practice) to address problems in higher education of Korea since 2012, but it was anticipated to face many difficulties in implementing the program due to lack of relevant experiences in Korea. In this regard, a performance evaluation scheme was urgently required to judge the effectiveness of the Co-op program and improve the operational efficiency at the same time. This study aimed to develop comprehensive performance evaluation criteria for the co-op programs on the basis of Kirkpatrick's four-level performance evaluation model for training programs, and apply it to a real Co-op operation to test its feasibility. For this purpose, thorough review on the training program evaluation literature and in-depth analyses of overseas cases of co-op performance evaluation were conducted. Then, a set of Co-op performance evaluation criteria was developed and applied to the Koreatech's Co-op operation in 2013. Two Co-op student questionnaire surveys were administered before and after Co-op terms to measure students' reactions to the Co-op program (Level 1) and changes in participating students' attitudes and competencies (Level 2). In addition, employment rates of Co-op participating and non-participating students were compared (Level 4). The analysis findings showed that participating students were quite satisfied with their jobs and companies, and the Co-op program was effective to a certain degree at enhancing non-major competencies and attitudes to occupation of students. Together, the employment rate of Co-op participants, particularly in small- and medium-sized companies, grew significantly in comparison with that of non-participants. In the last part, several directions for improving the effectiveness of the Co-op programs were discussed.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.315-316
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• 2014

Combustion gases emit various radiation signals by chemical reaction and excited molecules in combustion system. Since temperature measurement of combustion system is very difficult, non-contact temperature measuring methods are being researched. In this paper, we propose optical system of simple structure and implement technique for measuring temperature partially in furnace using radiation wavelength signals of high temperature $CO_2$ gas generated during combustion.

• Journal of Sericultural and Entomological Science
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• v.31 no.2
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• pp.121-126
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• 1989

Two kinds of solution for the measurement of solubilities of Sericin are prepared as followings at temperature 90 deg. C. One has the total carbonate concentration as 0, 50, 100mg CO2/l prepared with non-carbonate distilled water, sodium hydrogen carbonate and 0.1N HCI and NaOH, the other has total hardness, that is, calcium hardness or magnesium hardness as 0, 20, 50, 100mg CaCO2/l respectively prepared with non-carbonate distilled water, calcium carbonate and magnesium oxide. Solubilities of Cocoon layer Sericin at above solution gives following results ; 1. pH shows little effect on the solubility of Sericin at the non-carbonate solution but at the carbonate solution pH shows a sensitive effect on the solubility of Sericin. These means that pH controls the concentration of H2CO3, HCO3-and CO32- which prevent and promote the solution of Sericin. 2. After the cocoon layer treatment at the solution, the initial pH of 4.0, 7.0, 9.0 of the solution changed to 6.0-6.5 at the lower total carbonate solution. However in the higher total carbonate solution pH did not changed very much. This may be explained by the buffer action of carbonate. 3. The effect of the hardness on the solubility of Sericin was not found in the non-carbonate solution with the standard hardness after treatment of cocoon layer.

• Membrane Journal
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• v.22 no.2
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• pp.128-134
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• 2012

In this study, hydroxy polyimide (HPI) was prepared for non-porous membrane by solvent evaporation method. As the result of gas permeance properties measurement, $CO_2$ permeability was 85 Barrer and the $CO_2/N_2$ selectivity was 23 at $30^{\circ}C$. Flat sheet membrane and hollow fiber membrane were prepared by using ternary system of polymer, solvent and non-solvent additive. Morphologies and gas permeance properties were measured by FE-SEM and bubble flow meter. Each $CO_2$ permeability of 18.28 GPU, 70 GPU and $CO_2/N_2$ selectivity of 6.72, 8.63 at $30^{\circ}C$ in the flat sheet membrane and hollow fiber membrane. Hollow fiber membrane has gas permeance property better than flat sheet membrane.

• Corrosion Science and Technology
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• v.21 no.2
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• pp.89-99
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• 2022

A versatile method for performing non-cyanide electroless gold plating using thiomalic acid (TMA) as a complexing agent and 2-aminoethanethiol (AET) as a reducing agent was investigated. It was found that TMA was an excellent complexing agent for gold. It can be used in electroless gold plating baths at a neutral pH with a high solution stability, makes it a potential candidate to replace conventional toxic cyanide complex. It was found that one gold atomic ion could bind to two TMA molecules to form the [2TMA-Au⁺] complex in a solution. AET can be used as a reducing agent in electroless gold plating solutions. The highest current density was obtained at electrode rotation rate of 250 to 500 rpm based on anodic and cathodic polarization curves with the mixed potential theory. Increasing AET concentration, pH, and temperature significantly increased the anodic polarization current density and shifted the plating potential toward a more negative value. The optimal gold ion concentration to obtain the highest current density was 0.01 M. The cathodic current was higher at a lower pH and a higher temperature. The current density was inversely proportional to TMA concentration.

• Journal of Powder Materials
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• v.10 no.5
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• pp.305-309
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• 2003

We report on the formation and chemical leaching of non-equilibrium $Al_{0.6}(Fe_{75}Co_{25})$ alloy produced by rod milling. X-ray diffractometry, transmission electron microscopy, differential scanning calorimetry, scanning electron microscopy, and vibrating sample magnetometry were used to characterize the as-milled and leached specimens. After 400 h, only the $Al_{0.4}Fe_{0.6}$ peak of the body-centered cubic type was present in the XRD pattern. The entire rod milling process could be divided into three different stages of milling: agglomeration, disintegration, and homogenization. The saturation magnetization, $M_s$ decreased with increased milling time, the $M_s$ of the powders before milling was about 113.8 emu/g, the $M_s$ after milling for 400 h was about 11.55 emu/g. Leaching of the Al in KOH of the Al at room temperature from the as-milled powders did not induce any significant change in the diffraction pattern. After the leached specimen had been annealed at $600^{\circ}C$ for 1 hour, the nanoscale crystalline phases were transformed into the bcc Fe, cubic Co, and $CoFe_2O_4$ phases. On cooling the specimen from 85$0^{\circ}C$, the degree of magnetization increased slightly, then increased sharply at approximately 364.8$^{\circ}C$, indicating that the bcc $Al_{0.4}Fe_{0.6}$ phase had been transformed to the Fe and Co phases.

• Journal of Environmental Science International
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• v.20 no.8
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• pp.987-995
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• 2011

Co-planar PCBs(polychlorinated biphenyls) of non-ortho are investigated in soil and ginseng on the North Gyeongbuk with HRGC/HRMS. PCB77 in soil on Yeongju and Sangju are detected 0.0007 pgTEQ/g and 0.0009 pgTEQ/g, respectively. PCB81 in soil on Yeongju and Sangju are detected 0.0113 pgTEQ/g and 0.0108 pgTEQ/g, respectively. Also PCB126 in soil on Yeongju and Sangju are detected 0.0907 pgTEQ/g and 0.0944 pgTEQ/g, respectively. But PCB169 in soil on Yeongju and Sangju is not detected. Total Co-planar PCBs of non-ortho in soil on Yeongju and Sangju are 0.1027 pgTEQ/g and 0.1061 pgTEQ/g, respectively. PCB77 in ginseng on Yeongju and Sangju are detected 0.0008 pgTEQ/g. Then PCB81 in ginseng on Yeongju and Sangju are detected 0.0104 pgTEQ/g and 0.0112 pgTEQ/g, respectively. But PCB126 in ginseng on Yeongju and Sangju are detected 0.0585 pgTEQ/g and 0.0579 pgTEQ/g, respectively. PCB169 in ginseng on Yeongju and Sangju is not detected. Total Co-planar PCBs of non-ortho in ginseng on Yeongju and Sangju are 0.0697 pgTEQ/g and 0.0700 pgTEQ/g, respectively. Relationship of PCBs in between soil and ginseng shown significance($R^2$ : 0.99).

• Ocean Systems Engineering
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• v.2 no.1
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• pp.17-31
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• 2012

This study investigated the behavior of a non-isothermal $CO_2$ bubble formed through a leak process from a high-pressure source in a deep sea. Isenthalpic interpretation was employed to predict the state of the bubble just after the leak. Three modes of mass loss from the rising bubble were demonstrated: dissolution induced by mass transfer, condensation by heat transfer and phase separation by pressure decrease. A graphical interpretation of the last mode was provided in the pressure-enthalpy diagram. A threshold pressure (17.12 bar) was identified below which the last mode was no longer present. The second mode was as effective as the first for a bubble formed in deep water, leading to faster mass loss. To the contrary, only the first mode was active for a bubble formed in a shallow region. The third mode was insignificant for all cases.

• Journal of the Korean Society of Combustion
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• v.17 no.4
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• pp.30-37
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• 2012

The flame lengths and NOx emission characteristics of syngas $H_2$/CO turbulent non-premixed jet flames were investigated. The flame length which is the main parameter governs NOx emission was studied for various syngas compositions. The flame length was compared with previous correlation between Froude number and flame height and it shows that they have good agreements. It was confirmed that the turbulent jet flames herein investigated are in the region of buoyancy-momentum transition. NOx emission was reduced with increased Reynolds number and CO contents in syngas fuel and with decreased fuel nozzle diameter which is attributed by decreased flame residence time. Previous EINOx scaling based on flame residence time of $L_f^3/(d_f^2U_f)$ satisfies only the jet flame in momentum-dominated region, not buoyancy-momentum transition region. The simplified flame residence time ($L_f/U_f$) was adopted in modified EINOx scaling. The modified scaling satisfies the jet flames not only in momentum-dominated region but in buoyancy-momentum transition region. The scaling is also satisfied with $H_2$/CO syngas jet flames.