Job Satisfaction in Australia -The Effects of Demographic Background, Job Conditions and Psychological Dispositions-

Kim, Wansik김완식 숭실대학교부설 사회과학연구소 1990 社會科學硏究 Vol.8 No.1

Electrochemical Studies on Aqueous Uranium Redox Reactions and Nanoparticle Formation using Boron-doped Diamond Electrode

Wansik Cha,Euo Chang Jung,Hye-ryun Cho 한국방사성폐기물학회 2015 한국방사성폐기물학회 학술논문요약집 Vol.2015 No.05

Solid Phase Characterization and Groundwater Solubility of Synthetic Sklodowskite

Wansik Cha,Junghwan Park,Hye Ran Noh,Hye-Ryun Cho 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

The disposal of spent nuclear fuel (SNF) in a deep geological repository (DGR) is a widely accepted strategy for the long-term sequestration of radiotoxic SNF. Ensuring the safety of a DGR requires the prediction of various reactions and migration behaviors of radionuclides (RNs) present in SNF within its geochemical surroundings. Understanding the dissolution behaviors of mineral phases harboring these RNs is crucial, as the levels of RNs in groundwater are basically linked to the solubility of these solid phases. Accurate measurements of solubility demand the use of welldefined solid materials characterized by chemical compositions and structures. Herein, we attempted the synthesis of sklodowskite, a magnesium-uranyl (U(VI))-silicate, employing a twostep hydrothermal synthetic approach documented previously. Subsequently, we subjected this synthesized sklodowskite to various analytical techniques, including powder X-ray diffraction (pXRD), scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDX), and vibrational spectroscopies (FTIR and Raman). Based on our findings, we confidently identify the obtained mineral phase as sklodowskite (Mg[UO2SiO3OH]2·5H2O). This identification is primarily based on the similarity between its pXRD pattern and the reference XRD pattern of sklodowskite. Furthermore, the measured infrared and Raman spectra show the vibrational modes of UO2 2+ and SiO4 4- ions, particularly within the 700~1,100 cm-1 region, which support that the synthetic mineral has a characteristic layered uranyl-silicate structure of crystalline sklodowskite. Finally, we utilized synthetic minerals to estimate its solubility up to about three months in a model groundwater, where the dissolved species composition is analogous to that of granitic groundwater from the KAERI Underground Research Tunnel. In this presentation, we will present in detail the results of spectroscopic characterizations and the methodology employed to assess the solubility of the U(VI)-silicate solid phase.

Halotolerant Plant Growth Promoting Bacteria Mediated Salinity Stress Amelioration in Plants

Wansik Shin,Ashaduzzaman Siddikee,Manoharan Melvin Joe,Abitha Benson,Kiyoon Kim,Gopal Selvakumar,Yeongyeong Kang,Seonyoung Jeon,Sandipan Samaddar,Poulami Chatterjee,Denver Walitang,Mak Chanratana,Tong 한국토양비료학회 2016 한국토양비료학회지 Vol.49 No.4

Soil salinization refers to the buildup of salts in soil to a level toxic to plants. The major factors that contribute to soil salinity are the quality, the amount and the type of irrigation water used. The presented review discusses the different sources and causes of soil salinity. The effect of soil salinity on biological processes of plants is also discussed in detail. This is followed by a debate on the influence of salt on the nutrient uptake and growth of plants. Salinity decreases the soil osmotic potential and hinders water uptake by the plants. Soil salinity affects the plants K uptake, which plays a critical role in plant metabolism due to the high concentration of soluble sodium (Na<SUP>+</SUP>) ions. Visual symptoms that appear in the plants as a result of salinity include stunted plant growth, marginal leaf necrosis and fruit distortions. Different strategies to ameliorate salt stress globally include breeding of salt tolerant cultivars, irrigation to leach excessive salt to improve soil physical and chemical properties. As part of an ecofriendly means to alleviate salt stress and an increasing considerable attention on this area, the review then focuses on the different plant growth promoting bacteria (PGPB) mediated mechanisms with a special emphasis on ACC deaminase producing bacteria. The various strategies adopted by PGPB to alleviate various stresses in plants include the production of different osmolytes, stress related phytohormones and production of molecules related to stress signaling such as bacterial 1-aminocyclopropane-1-carboxylate(ACC) derivatives. The use of PGPB with ACC deaminase producing trait could be effective in promoting plant growth in agricultural areas affected by different stresses including salt stress. Finally, the review ends with a discussion on the various PGPB activities and the potentiality of facultative halophilic/halotolerant PGPB in alleviating salt stress.

Synthesis and Characterization of Ca-Silicate Bearing Uranium Minerals

Wansik Cha,Junghwan Park,Hye Ran Noh,Euo Chang Jung,Sang Ho Lim,Hye-Ryun Cho,Hee-Kyung Kim 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2

Nuclear spent fuel (SNF) disposal in deep geological repositories is considered as one of sound options for the long-term and safe sequestration of radiotoxic SNF and the sustainable use of nuclear energy. The chemical behaviors of various radionuclides originated from SNF should be well understood to evaluate the migrational behaviors of radionuclides and their reactions and interactions with various geochemical components. Formation of secondary minerals, colloids, other insoluble precipitates is of interest since the concentrations of radionuclides in groundwaters can be limited by the solubility of those solid phases. Particularly when evaluating their solubility, the use of well-defined solid materials in terms of chemical composition and molecular structure is crucial to obtain reliable measurement results. In this study, a synthetic calcium uranyl silicate (Ca-U(VI)-silicate, or uranophane) was prepared and characterized by using various analytical methods including powder X-ray diffraction (pXRD), scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDX), and vibrational (FTIR and Raman) spectroscopies. Uranyl silicate minerals are significant to the disposal of nuclear wastes. Our simulation demonstrates that uranophane (Ca[UO2SiO3OH]2·5H2O), one having a U:Si ratio of 1:1, can be a mineral species limiting U(VI) solubility under groundwater conditions in Korea. For the preparation of Ca-U(VI)-silicate, we applied a two-step hydrothermal synthetic procedure reported in literature with modification. Briefly, we conclude that the obtained mineral phase is the ‘α-uranophane’; our characterization results show that the structural and spectroscopic properties of the synthetic Ca-U(VI)-silicate agree well with those of α-uranophane. For instance, the pXRD patterns obtained from the solid show nearly identical diffraction peak positions with those from the reference XRD pattern. From IR and Raman spectroscopy it is noticed that the stretching modes of UO2 2+ and SiO4 4- ions result in strong absorption bands in a region of 700 ~ 1,100 cm-1. Elemental compositions of the synthetic solids were also estimated by using EDX analysis, which results in a Ca:U:Si ratio close to 1:2:2 on average. However, we found that it is difficult to obtain good crystallinity of uranophane, which can be observable by using SEM and its image analysis. We believe that this work serves as a model study to provide synthetic routes of radionuclide-related mineral phases and applicable solid phase characterization methods. In the presentation, the potential use of the U(VI)-silicate solid phase for the upcoming groundwater solubility measurements will be discussed. Keywords: Hexavalent Uranium, Silicate

Resection A Surgery

Wansik Yu,Ho Young Chung 대한외과학회 2010 Annals of Surgical Treatment and Research(ASRT) Vol.79 No.3

Purpose: We evaluated the clinical implication of Resection A surgery retrospectively to identify whether quality of surgery can be used as a selection factor for adjuvant therapy in patients with gastric cancer. Methods: Prognosis of 902 patients with gastric cancer who underwent Resection A surgery was evaluated. Results: Among all discharged patients, 77 patients (8.5%) died of recurrent disease, 55 patients (6.1%) died without recurrent disease. Five-year survival rate of all discharged patients was 91.6% and 10-year survival rate 87.1%. Statistically significant prognostic factors were depth of invasion (P<0.001), lymph node metastasis (P<0.001), stage (P<0.001), tumor location (P=0.036) and size (P=0.001), extent of gastric resection (P<0.001), and chemotherapy (P<0.001) on univariate analyses. However, depth of invasion (P=0.001), lymph node metastasis (P<0.001), and total gastrectomy (P<0.001) emerged as statistically significant poor prognostic factor on a multivariate analysis. Adjuvant chemotherapy did not increase the survival rate of patients after Resection A surgery, even in patients with stage Ⅱ disease. Conclusion: In selecting the patients for adjuvant therapy, both the stage of gastric cancer and the quality of surgery should be considered.

HPA MMIC to W/G Antenna Transition Loss Analysis and Development Results of W-band Transmitter Module

Wansik Kim,Juyong Jung,Juyoung Lee,Jongpil Kim 국제문화기술진흥원 2019 International Journal of Advanced Culture Technolo Vol.7 No.4

This paper will read about a multichannel frequency-modulated continuous wave (FMCW) radar sensor with switching transmit (TX) antennas is developed at W-band. To achieve a high angular resolution, a uniform linear array consisting of 5 switching-TX and 12 receive (RX) antennas is employed with the digital beamforming technique. The overall radar front-end module comprises a W-band transceiver and TX/RX antennas. A multichannel transceiver module consists of 5 up-conversion and 12 down-conversion channels, where one of the TX channels is sequentially switched ON. For developing transmitter, we developed an HPA (high power amplified) MMIC chip for W-band radar system and fabricated a transmitter module using this chip. In order to develop the W-band transmitter, we analyzed the important antenna transition structure from HPA MMIC line to W/G (Waveguide)antenna via M/S(microstrip) and fabricated it with 5 transmission channels. As a result, the output power of the transmitter was within 1 dB of the error range after analysis and measurement under normal temperature and environmental conditions.

Evaluation of Spectroscopic Methods for Determination of Hydrogen Peroxide as a Radiolysis Product

Wansik Cha,Yubin Kim 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2

Radiation from spent nuclear fuel (SNF) is one of key factors affecting the dissolution process of SNF and the source term from repository. The dissolution rate of uranium dioxide (UO2) matrix of SNF is expected to control the release of radionuclides from SNF in contact with water under geological disposal conditions. Based on the oxidative dissolution mechanism, the solubility of UO2 can increase significantly if the reducing environment near the fuel surface is altered by water radiolysis caused by radiation from SNF. Therefore, the analysis of water radiolysis products such as radicals (·OH, ·OH2, eaq, ·H) and molecules (H3O+, H2, H2O2) is perquisite for studies on the rate of such dissolution process to determine oxidation/dissolution mechanism and related rate constants. In this study we examined the two-known spectroscopic methods developed for H2O2 determination; one is the luminol-based chemiluminescence (luminol-CL) method and the other is the spectrophotometry using ferrous oxidation-xylenol orange complexation (FOX). Their applicability for quantitative analysis of H2O2 in potential aqueous samples from SNF dissolution studies was evaluated in terms of the analytical dynamic range (ADR), the limit of detection (LOD) and the interfering effects of various metal ions possibly present in real samples. The luminol-CL method exploits the chemiluminescence reaction caused by luminol; when in the presence of a metallic catalyst (e.g., Cu2+, Co2+), luminol emits a blue light (425 nm) at pH 10- 11 in response to oxidizing agents such as hydrogen peroxide. Although a flow-through reaction system is routinely employed to enhance the analytical sensitivity we achieved the ADR up to ~200 μM and LOD < 1 μM by a batch-wise CL detection using conventional cuvette cells and an intensified charge-coupled device (ICCD). Interestingly, it turned out that the interfering effects of other metal ions (e.g., UO2 2+, U4+, Fe2+ and Fe3+) is minimal, which should be advantageous for the luminol-CL method to be employed for samples potentially containing other metal ions. On the other hand, the FOX method spectrophotometrically analyzes H2O2 based on the difference in color (or absorption spectra) of Fe-xylenol orange (XO) complexes. Initially, the Fe2+-XO complex was provided in working solutions at pH 3, which was subsequently mixed with samples having H2O2 and allowed for quantitative oxidation of Fe2+ to Fe3+. Typically, by monitoring the absorbance of Fe3+-XO complex at 560-580 nm (λmax) the ADR up to ~100 μM and LOD ~1.6 μM were achieved. However, it is found that interfering effects from M3+ and M4+ ions are significant; these interfering metal ions can form XO complexes so as to directly contribute the measured absorbance. In contrast, the influence from M2+ ions was found to be negligible. To summarize we conclude that both methods can be applied for H2O2 determination for aqueous samples taken from SNF dissolution tests. However, prior to applying the FOX method the metal ion composition in those samples should be thoroughly identified not to overestimate the H2O2 concentration of samples. More details of underlying chemical reactions in both methods will be discussed in the presentation.

Thermodynamic and Chemical Behaviors of U(IV) Species Under Groundwater Conditions

Wansik Cha,In Hak Yoon,Hyejin Cho,Hye-Ryun Cho 한국방사성폐기물학회 2021 한국방사성폐기물학회 학술논문요약집 Vol.2021 No.11

Electrochemical Studies on Aqueous Uranium Redox Reactions and Nanoparticle Formation using Boron-doped Diamond Electrode

Wansik Cha,Euo Chang Jung,Hye-ryun Cho 한국방사성폐기물학회 2015 한국방사성폐기물학회 학술논문요약집 Vol.13 No.1