[en] In dealing with drastic and enthusiastic nuclear power generation plan in Korea, some attention should be paid to optimization study on nuclear power strategies with regard to nuclear fuel cycle. As one of system approaches, this study attempts to cover the problems of optimal combinations of reactor type, the requirements of nuclear fuel cycle, the treatment of spent fuel and the available timing of FBR, through minimizing the nuclear systems costs-reactor operation and maintenance cost, nuclear fuel cost and construction cost, by using Mixed Integer Linear Programing (MILP) technique. However, this study put the emphasis on the building of MILP model in itself due to incompleteness of MILP computer code, without presenting any kinds of concrete solutions. To make this MILP model actually be used for utilization, further study has to be done

[en] According to conductivity mechanism of semiconductor, we have investigated the conductivity of polycrystalline CdTe. It was based upon space-charge-limited region and band model structure of amorphous semiconductor. We have found by analysis of experimental results that the conductivity mechanism was trap-dominated. The activation energy (phi=0.05 eV) was calculated from experimental data and was not dependent on thickness of sample. (author)

[en] The Wolak mine is located in Hwanggang-ri mining district and is producing tungsten and molybdenum ores. Temperature of mineral-formation of quartz veins in Kwang-cheon ore deposit is estimated by means of heating stage microscope and decrepitation and pressure of mineral-formation is calculated using Shatagin's empirical equation. A grain size of -45 - +80 mesh (0.18 - 0.32mm) is most satisfactory for decrepitation method. Compared with homogenization temperature and decrepitation temperature, the temperature at the beginning of decrepigraph corresponds to homogenization temperature, and the temperature at the maximum frequency of decrepigraph corresponds to the temperature corrected by pressure which is calculated by Shatagin's equation. Vertical temperature variation is determined that the decrepitation temperature is gradually increased with depth at No. 1 vein. The temperature and pressure of mineral-formation in Wolak mine is estimated as about 350degC and 1213.4 atm. (Author)

[en] CdSe thin film was prepared on the slide glass by the evaporation method in a vacuum of about 10^-6 torr. By analyzing the T-lambda and R-lambda data for the thin film at normal incidence of light, the refractive index, n and absorption coefficient α, absorption index k, and the dielectric loss tanσ were obtained and related to the conditions of the evaporation. The refractive index was 2.50 for A-type and 2.75 for B-type in the region of long wavelength. The absorption coefficient was in the order of approximately 10⁵ cm^-1 and was invariant in the region of long wavelength. The absorption index k was in range of 0.13 approximately 0.36. The permittivity epsilon and tanσ were in range of 7 approximately 12 and 0.86 approximately 0.26 respectively. (author)

[en] The drift mobility of carriers in the vitreous Se thin films were measured by the Haynes-Schokley method. It had been shown that the hole mobility was about 0.83 cm³/V-sec and the drift velocity showed no time dependence. It had also been shown that the value of Pool-Frenkel parameter was approximately 2 from the I-V curve. (Author)

[en] A differential pressure during the operation of MOV (motor operated valve) is one of the most important parameters for the evaluation of required stem thrust. Most MOV applications can be approximated as being steady state since the valve stroke times are long and the ensuing flow acceleration/deceleration effects are small. However, for the some rapid closing valve, flow acceleration/deceleration effects may have to be accounted for. Under such condition, the pressure is higher than steady state pressure build up during a closing stroke. In this study, we performed the analysis for the one valve, which is a rapid closing MOV in nuclear power plant. The velocity distribution and fluid flow pattern were analyzed by using FLUENT code. and differential pressure profile were analyzed by usin g Flowmaster code. The calculation result by Flowmaster code was very similar to the differential pressure of the field test

[en] The prognosis of intracranial germinoma producing the human chorionic gonadotropin (hCG) is controversial due to limited information. We undertook a retrospective analysis to determine whether this type of tumor has similar clinical course and prognosis to hCG non-secreting germinoma. Thirty-one histologically confirmed intracranial germinoma patients who had pretreatment hCG examination in serum/CSF were treated with radiotherapy between 1980 and 1996. hCG level was measured by immunoradioassay of beta subunit of hCG. Six patients had elevated serum hCG levels and were defined as having hCG secreting germinoma. All except three patients received craniospinal axis irradiation. The follow-up ranged from 19-175 months with a median of 63 months. hCG secreting germinoma accounted for 19% of intracranial germinoma cases. Elevated hCG levels ranged from 39-260 IU/l in serum. No difference was found between hCG non-secreting germinoma and hCG secreting germinoma in terms of patient or treatment characteristics. There was no recurrence among the six hCG secreting germinoma patients. The 5-year overall and disease-free survival rates were 96% for patients with hCG non-secreting germinomas and 100% for the patients with hCG secreting germinomas. The survival difference was not significant (p = 0. 59). Our results suggest that elevated level of hCG did not result in any differences in the clinical characteristics or survival after radical radiotherapy in histologically confirmed intracranial germinoma

[en] The temperature variations of the diffusion coefficient D(T), thermal diffusion ratio k_T(T) and thermal conductivity k(T) in a dilute solution of ³He atoms in two-dimensional liquid helium are evaluated explicitly by solving the kinetic equations via phonon-phonon, phonon-roton, roton-roton, impurity-elementary excitation and impurity-impurity scatterings. In the low-temperature region, the main contributions to D(T) and k(T) come from the interactions between phonons and impurities, while in the high-temperature region the interactions between impurities and whole elementary excitations contribute more strongly to D(T) and k(T) than those of only elementary excitations. For a dilute solution, the thermal diffusion ratio k_T(T), neglecting the internal mass counterflow, is much smaller than the effective thermal diffusion ratio k_T(T), which is a function of thermostatic properties. The effective thermal conductivity k_eff is much larger than the thermal conductivity. The behaviors of the two-dimensional diffusion coefficient and thermal conductivity are much like the bulk case, where they exhibit exponential decay with increasing temperature, although they are much smaller than those of the bulk case

[en] Situations where a gas and a liquid flow together in a pipe occur in various terrestrial applications, such as gas dissolution in liquid in the chemical and pharmaceutical industries, oil and gas pipelines, nuclear power plants, and two-phase flow heat exchangers, to name a few examples. A study of bubble generation for constant gas-flux condition by single-nozzle injection in a coflowing liquid is reported. Focusing on single-bubble generation in the dynamic and bubbly flow regime, the onset condition for bubble coalescence is investigated. The role of various forces involved in the bubble formation process is studied, and an overall force balance describing bubble dynamics is developed. Gas-momentum flux and buoyancy in normal gravity enhance, while the surface-tension force at the nozzle rim inhibits bubble detachment. On the other hand, liquid drag and inertia can act both as attaching or detaching forces, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with the present reduced-gravity experiment and available normal-gravity experiments. Effects of the fluid properties, injection geometry, and flow conditions on bubble size are investigated

[en] Full text: The objectives of this study are to investigate the significance of apoptotic death compared to total cell death after γ-ray irradiation in human Hand N cancer cell lines and to find out correlation between apoptosis and radiation sensitivity. Materials and Method: Head and neck cancer cell lines (PCI-1, PCI-13, and SNU-1066), leukemia cell line (CCRF-CEM), and fibroblast cell line (LM217) as a normal control were used for this study. Cells were irradiated using Cs-137 animal experiment irradiator. Total cell death was measured by clonogenic assay. Annexin-V staining was used to detect the fraction of apoptotic death. The resulting data was analyzed with two parameters, apoptotic index (AI) and apoptotic fraction(AF). AI is ratio of apoptotic cells to total cells, and AF is ration of apoptotic cell death to mutant frequencytion ex(Number of apoptotic cells) / (Number of total cells counted) AF = {(AI) / (1-survival fraction)} x 100 (%) Results. Surviving fraction at 2 Gy (SF2) were 0.741, 0.544, 0.313, 0.302, and 0.100 for PCI-1, PCI-13, SNU-1066, CCRF-CEM, and LM217 cell lines, respectively. Apoptosis was detected in all cell lines. Apoptotic index reached peak value at 72 hours after irradiation in head and neck cancer cell lines, and that was at 24 hours in CCRF-CEM and LM217. Total cell death increased exponentially with increasing radiation dose from 0 Gy to 8 Gy, but the change was minimal in apoptotic index (Fig. 1.). Apoptotic fractions at 2 Gy were 46%, 48%, 46%, 24%, and 19% and at 6 Gy were 20%, 33%, 35%, 17%, and 20% for PCI-1, PCI-13, SNU-1066, CCRF-CEM, and LM217, respectively. The radioresistant cell lines showed more higher apoptotic fraction at 2 Gy (Table 1.), but there was not such correlation at 6 Gy. Conclusion: All cell lines used in this study showed apoptosis after irradiation, but time course of apoptosis was different from that of leukemia cell line and normal fibroblast cell line. Reproductive cell death was more important mode of cell death than apoptotic death in all cell lines used in this study. But there was correlation between apoptotic fraction and radiation sensitivity at 2 Gy