• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.4
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• pp.412-418
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• 2020

Generally, the propeller shaft that constitutes the ship shaft system has different patterns of behavior due to the ef ects of engine power, propeller load and eccentric thrust, which increases the risk of bearing failure by causing local load variations. To prevent this, different studies of the propulsion shaft system have been conducted focused the relative inclination angle and oil film retention between the shaft and the support bearing, mainly with respect to the Rules for the Classification of Steel Ships. However, in order to secure the stability of the propulsion shaft via a more detailed evaluation, it is necessary to consider dynamic conditions, including the transient state due to sudden change in the stern wakefield. In this context, a 50,000 DWT vessel was analyzed using the strain gauge method, and the effects of propeller shaft movement were analyzed on the starboard rudder turn which is a typical transient state during normal continuous rate(NCR) operation in ballast draught condition. Analysis results confirm that the changed propeller eccentric thrust acts as a force that temporarily pushes down the shaft to increase the local load of the stern tube bearing and negatively affects the stability of the shaft system.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.93-99
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• 2014

Use of geothermal energy has been increased for its economical application and environmentally friendly utilization. Particularly, for energy piles, a spiral coil type ground heat exchanger (GHE) is more preferred than line type GHEs such as U and W shaped GHEs. A PHC energy pile with spiral coil type GHE was installed in an area of partially saturated dredged soil deposit, and a thermal response test (TRT) was conducted for 240 hours under a continuous operation condition. Besides, remolded soil samples from different layers were collected in the field, and soil specimens were reconstructed according to the field ground condition. Non-steady state probe methods were conducted in the lab, and ground thermal conductivity and thermal diffusivity were measured for the different soil layers. An equivalent ground thermal conductivity was calculated from the lab test results and it was compared with the field TRT result. The difference was less than 5%, which advocates the use of an equivalent ground thermal conductivity for the multi-layered ground. Furthermore, this paper also represents an equivalent ground thermal diffusivity evaluation method which is another very important design parameter.

• Journal of the Korea Computer Graphics Society
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• v.26 no.1
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• pp.17-25
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• 2020

We present a novel multi-core CPU based parallel algorithm for the cell-connectivity information extraction algorithm, which is one of the preprocessing steps for volume rendering of unstructured grid data. We first check the synchronization issues when parallelizing the prior serial algorithm naively. Then, we propose a 3-step parallel algorithm that achieves high parallelization efficiency by removing synchronization in each step. Also, our 3-step algorithm improves the cache utilization efficiency by increasing the spatial locality for the duplicated triangle test process, which is the core operation of building cell-connectivity information. We further improve the efficiency of our parallel algorithm by employing a memory pool for each thread. To check the benefit of our approach, we implemented our method on a system consisting of two octa-core CPUs and measured the performance. As a result, our method shows continuous performance improvement as we add threads. Also, it achieves up to 82.9 times higher performance compared with the prior serial algorithm when we use thirty-two threads (sixteen physical cores). These results demonstrate the high parallelization efficiency and high cache utilization efficiency of our method. Also, it validates the suitability of our algorithm for large-scale unstructured data.

• Korean Journal of Construction Engineering and Management
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• v.21 no.1
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• pp.3-11
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• 2020

In large public construction projects with a certain size or larger that need to be carried out over a number of years, the Authority must secure a budget for construction project management activities by the construction manager. There is no problem if the project management budget secured by the issuing Authority and the project management budget executed by the issuing Authority are the same, but if not, various problems will arise. Therefore, in this study, the following measures were proposed to improve the system for efficient operation of construction project management: First, the construction project management terms and tasks specified in the statutes and the guidelines of government agencies should be unified and the standard for calculating consideration should be unified. Second, the total project cost management guideline should be specified so that the missing construction project manager can receive compensation for the technical proposal. Third, if the project cost is changed in the long-term continuous construction project, the construction project management expense should be adjusted accordingly. Fourth, if construction project management service is required from the Authority, the basis for consignment to a specialized institution should be specified in the total project cost management guideline.

• Journal of The Korean Association of Information Education
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• v.11 no.3
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• pp.339-347
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• 2007

Along with developments of information and communication technologies, internet has spread not only all over the society, but also our everyday life deeply. Recently, requirements for e-learning using internet in the educational aspect have a great influence on the changes of school educations. Cyber Home Learning System, in particular, has been implemented throughout the nation for the purpose of reducing private expenditure for education and promoting substantial improvements in quality of public education. However, there have been exposed many problems with respect to quality of operations and managements of the system comparing to its quantitative growth, and so, at this point in time, researcher conducted analysis of actuality of perceptions of both elementary and middle school teachers with a focus on the case of S System in K province. To test this, total 278 participants were sampled from the elementary schools (139 teachers) and the middle schools (139 teachers) located in K province and were asked to complete a survey and the results therefrom were analyzed accordingly. Results from the analyses revealed that elementary school teachers responded more positively than other respondents in the most areas, including supply of a variety of learning contents of S System, quality of contents, and providing for helps insomuch as to complement school works, etcetera. In addition, researcher has found out that, to make the system become all the more efficient, it shall be required to establish a strategy in order to induce students' interest in the system, as well as to construct infrastructure for facilitating the use of computer. And that there are also needs for continuous supports from both the school and the education authority concerned, and for method of flexible operation of curriculum.

• Journal of agricultural medicine and community health
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• v.12 no.1
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• pp.54-62
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• 1987

This study was performed as a part of survey for the operation and interim evaluation of the on-going pilot project of community health in Jeomdong-Myon, Yeoju-Gun, Kyunggi-Province since 1982. Seven Villages (Ri) were selected purposively for the survey from a total of 26 villages in Jeomdong-Myon, target area, under the consideration of the socio-economic background and the distribution of health resources. The target population was the women in age group of 15-44 years in that area and a total of 156 women were interviewed. This study was done by the interview survey using questionnaire which was composed with questions about MCH and FP. The results were as follows; 1) ln the status of maternal health, (1) the proportion of receiving antenatal care was relatively high (67.1%) in this area, but the starting time of antenatal care was delayed to 7 months or more of gestational period in 22 percent. Therefore some intervention would be necessary for advancing the time of antenatal care. (2) The proportion of home delivery was decreased according to the rank of birth-order. And more than 50 percent of delivery attendants were mothers-in-law or neighbors. The fact indicates that the health education for non-professional delivery attendents would be necessary for improving home delivery and the content of education would be preferable to focussing to the method of hygienic delivery attending. (3) The comprehensive health service and education would be recommended for the postnatal care, because of the extremely low rate of postnatal care in this area. 2) In the status of child health, (1) the pro-portion of breast feeding was 90.2 percent, and the weaning started after 12 months of birth in 12.7 percent. This indicates the necessity of education about the weaning program. (2) The proportion of completed basic vaccination was 39.6% and the main reason of missing vaccination was poor accessibility in terms of time. For that, the supply of vaccine to primary health care units (health subcenters) should be continuous, not infrequent nor occassional. 3) The proportion of respondants who were using contraceptive methods currently was 79.8 percent and in 44.7 percent they accepted the permanent contraceptive methods. Those results are distinct in this area. But it seems a serious health problem that 53.2 percent of respondants were experienced the induced abortion for birth control.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.3
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• pp.489-497
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• 2009

Occurrence of multiple cysts in jaw bone is rare compared to solitary cysts. numerous cysts occurring in jaw bone which not accompany any syndromes are defined as multiple jaw cysts, and most of these cases in children are keratocystic odontogenic tumor (KCOT) Multiple KCOT occurring in children are often associated with basal cell nevus syndrome(BCNS), so if multiple cysts are found on the radiograph, we suspect this syndrome and pursue clinical and pathological tests. In this case, a pediatric patient, reporting with multiple cysts in the jaw was suspected of BCNS, but hasn't shown any other symptoms of this syndrome up to date, and has kept repeating surgical operation and recurrence of the tumor. Although no symptoms besides multiple jaw cysts is present, it is often reported that other symptoms appear late in the patient's age. Therefore, in cases where multiple odontogenic tumors are found in children, continuous radiographic and clinical follow-ups in order to check the progress of the syndrome is considered important.

• Journal of Radiation Protection and Research
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• v.27 no.1
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• pp.27-35
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• 2002

Characteristics of Amberlite IRN 77, a cation exchange resin, and the mechanisms of its adsorption equilibria with Co(II), Ni(II), Cr(III) and Fe(III) ions were investigated for the application of the demineralizing process in the primary coolant system of a pressurized water reactor (PWR). The optimum dosage of the resin for removal of the dissolved metal ions at $200mgL^{-1}$ was 0.6 g for 100 mL solution. Most of each metal ion was adsorbed onto the resin in an hour from the start of the reaction. Each metal adsorption onto the resin could be well represented by Langmuir isotherms. However, in the case of Fe(III) adsorption, continuous formation of Fe-oxide or -hydroxide and its subsequent precipitation inhibited the completion of the equilibrium between the metal and the adsorbent Cobalt(II) and Ni(II), which have an equivalent electrovalence, were adsorbed to the resin with a similar adsorption amount when they coexisted in the solution. However, Cr(III) added to the solution competitively replaced Co(II) and Ni(II) which were already adsorbed onto the resin, resulting in desorption of these metals into the solution. The result was likely due to a higher adsorption affinity of Cr(III) than Co(II) and Ni(II). This implies that the interactively competitive adsorption of multi-cations onto the resin should be fully considered for an efficient operation of the demineralizing ion exchange process in the primary coolant system.

• Journal of Radiation Protection and Research
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• v.13 no.1
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• pp.8-20
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• 1988

The annual individual and collective doses to the thyroids of four age-dependent groups due to the in-take of I-131 released from the Younggwang nuclear power plant NU-1 & 2, Korea, are estimated using the model presented in ICRP 29. Sensitivity and robustness of the model are analyzed. In case of 0.12% fuel defect during normal operation, the collective dose is founded to be 3.05${\times}10^{-3}$man-thyroid-Sv, which is higher than the value calculated by the GASPAR code, 2.3${\times}10^{-3}$man-thyroid-Sv. The maximal individual annual doses resulting from an acute release are higher than those calculated under the assumption of continuous release by $1.4{\sim}1.7$ times. The most important pathway to the infant is milk and, in contrast, that to child, teen and adult is ingestion of crops. The model used is the calculation appears to be influenced by the variables such as roubstness-index. The weighted committed dose equivalent obtained by the ICRP 29 model is slightly higher than that calculated by the three-compartment model.

• Journal of Environmental Health Sciences
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• v.21 no.4
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• pp.1-9
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• 1995

This study was carried to investigate the biodegradability of phenol in the wastewater with the two sludge blanket-packed bed reactor in series. Each reactor had a dimension of 0.09 m i.d. and 1.5 m height and consisted of two regions. The lower region was a sludge blanket of 0.5 m height and the upper region was a packed-bed of 1 m height. The packed bed region was charged with ceramic raschig rings of 10 mm i.d., 15 mm o.d. and 20 mm length. The reactors were operated at 35$\circ$C and the hydraulic retention time(HRT) was maintained 24 hours. The synthetic wastewater composed of glucose and phenol as major components was fed into the reactor in a continuous mode with incereasing phenol concentration. In addition, the nutrient trace metals($Na^+, Mg^{2+}, Ca^{2+}, PO_4^{3-}, NH_4^+, Co^{2+}, Fe^{2+}$ etc.) were added for growing anaerobes. The phenol concentration of the effluent, the overall gas production, the composition of product gas, the efficiency of COD reduction and the duration of acclimation period were measured to determine the performance of the anaerobic wastewater treatment system as the phenol concentration of the influent was increased from 600 to 2400 mg//l. Successfully stable biodegradation of phenol could be achieved with the anaerobic treatment system from 600 to 1, 800 mg/l of the influent phenol concentration. The upper level of influent phenol loading was high enough to meet most of the practical requirement. The duration of acclimation increased with the phenol loading. At steady state of the influent phenol concentration of 1800 mg/l, the treatment performance indicated the phenol reduction efficiency of 99%, the COD reduction efficiency of 99% and the gas production rate of 37 l/day. At the influent phenol concentration of 2400 mg/l, however, the operation of the treatment system was noted unstable. While the concentration of methane in biogas decreased with increasing the influent phenol loading, the carbon dioxide was increased. However, the concentration of hydrogen was varied negligibly. The concentration of methane was high enough to be used as a fuel. As a result, it is suggested that anaerobic phenol wastewater treament was economical in the sense of energy recovery and wastewater treatment.