• Journal of the Korean Crystal Growth and Crystal Technology
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• v.2 no.1
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• pp.10-19
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• 1992

Mn - Zn Ferrite has physical properties of the high initial permeability, saturation magnetic flux density, and low loss factor as a representative magnetic material of soft ferrites, in addition the mechanical property is excellent as a single crystal. Therefore it is important electronic components and used for VTR Head. Mn - Zn Ferrite single crystals with the diameter 8mm were grown in atmosphere mixed with $O_2$ and Ar gas by the Floating Zone(FZ) method that impurities can not be incorporated to the crystals because of not-using the crucible to put in the melt, and the sharp temperature gradient results from making a focus at one point utilizing the infrared ray emitted from the halogen lamp as a heat source. During the crystal growing, the highest temperature of melting area was maintained to be $1650^{\circ}C$, growth rate and rotation rate were 10 mm/hr, 20 rpm respectively. The phases and the growth directions of crystals were determined from the analysis of X RD patterns, Laue, TEM diffraction patterns and etch pit shapes were observed by the optical microscope through the chemical etching. The corelation of optimum conditions for acquiring the better crystals was found out with the growth rate, the length and diameter of melt at the interface according to the diameter of feed rod, and the patterns of growing interface also studied.

• Korean Journal of Agricultural Science
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• v.42 no.3
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• pp.191-199
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• 2015

We conducted this research to observe the changes of surface morphology and composition of clay minerals influenced by various concentrations of fluoric acid. Hydrofluoric acid (HA), a solution of hydrogen fluoride (HF) in water, is a colourless solution that is highly corrosive, capable of dissolving many materials, especially oxides. To do this, we treated several concentrations of HA on the ground soil samples collected from the agricultural experimental station located at Chungnam National University to observe the influence of fluoric acid on the changes of surface structures and elemental composition of clay particles. Generally, microscopic examination showed that the HA can not only attack an edge of clay particles but also start at any point where structural defects and weaknesses predisposed sites to acid. The orderly flake arrangement of clay minerals may reflect certain crystal symmetry elements. The ESEM-EDS results of element composition of clay particles influenced by HA indicated the changes of structures of clay minerals. It is also clear from the formation of etch figures and element composition of clay particles that the product layer at least partially dissolved or disintegrated in the presence of acid. Conclusively, the clay structures can be strongly influenced by concentrations of HA, resulting in changes of physical and chemical properties that can determine the behavior of solute transport as well as mobility of ions in soils.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.37-51
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• 2013

An energy pile encases heat exchange pipes to exchange thermal energy with the surrounding ground formation by circulating working fluid through the pipes. An energy pile has many advantages in terms of economic feasibility and constructability over conventional Ground Heat Exchangers (GHEXs). In this paper, a coil-type PHC energy pile was constructed in a test bed and its thermal performance was experimentally and numerically evaluated to make a preliminary design. An in-situ thermal response test (TRT) was performed on the coil-type PHC energy pile and its results were compared with the solid cylinder source model presented by Man et al. (2010). In addition, a CFD numerical analysis using FLUNET was carried out to back-analyze the thermal conductivity of the ground formation from the Ttype PHC energy RT result. To study effects of a coil pitch of the coil-type heat exchange pipe, a thermal interference between the heat exchange pipes in PHC energy piles was parametrically studied by performing the CFD numerical analysis, then the effect of the coil pitch on thermal performance and efficiency of heat exchange were evaluated. Finally, an equivalent heat exchange efficiency factor for the coil-type PHC energy pile in comparison with a common multiple U-type PHC energy pile was obtained to facilitate a preliminary design method for the coil-type PHC energy pile by adopting the PILESIM2 program.

• Journal of Venture Innovation
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• v.3 no.1
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• pp.165-182
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• 2020

This research shows solutions for relieving the reversibility of the VAT system, and the solutions will be reviewed with current issues about supporting welfare. The Followings provide practical implementing solutions for each issue. Since the VAT is taxed for all goods and services as a general consumption tax, it is efficient tax policy for resource allocation comparing to income tax. On the other hand, because of the reversibility of the tax burden is also treated as a non-effective tax system for fair taxation. Even it is a non-effective tax system, the VAT system takes the most portion from the total national tax. In South Korea economic system, it is hard to raise the VAT rate because the economic effects are tremendous. For the long-term, the possibility of increasing the VAT rate is unavoidable, considering the economy, society, environment and energy, and aging. Therefore, a variety of substituted policies for the reversibility should be covered once there is a conference for the increase in the VAT rate. This research provides foundational solutions by acknowledging the reversibility of the tax burden in terms of the effective value-added tax rate. The followings are four solutions. First, it is required to adjust the duty-free system for relieving the reversibility and expand the tax-free system as well as individual consumption tax items. Second, The relief of reversibility should be worked by imposing higher the tax rate for high-income people' goods and services. Third, the adjustment of the duty-free system could be considered due to relieve the reversibility of the VAT. Last, it is considered to adjust of the simplified taxation system because the simplified taxation system is seriously against the tax-transfer principles.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.191-195
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• 2005

The port entry system of the inner harbor in Pyeongtaek (Asan) was planned as lock-gate in 'Master plan project on port planning in Asan industry base(1990)', but was changed to tidal harbor in 'Project maintaining Master Plan for comprehensive development of Pyeongtaek (Asan) port(2001)'. Accordingly, southern sea bank constructed under the lower part of Seohae-bridge will be removed so that inbound/outbound vessels for the inner harbor can navigate at all times. However, in the view of the safety on passing through the lower of Seohae-bridge, navigating conditions for the inner harbor will be restricted in the single-way of 50,000 DWT vessel and the two-day of vessel less than 30,000 DWT. Therefore, this study carried out the estimation of traffic congestion arising from these vessels with above restrictions after supposing annual inbound/outboubd vessel's numbers for loading and unloading cargo surveyed on the inner harbor.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.9 no.1
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• pp.41-49
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• 2011

This study purposes to conduct visual feedback and body posture control training on stroke patients with pusher syndrome in order to reduce their pusher syndrome. This study also examines changes resulting from the training and applies the guidelines necessary for documentation of patient/customer management. The participant for this study was one patient with pusher syndrome. The study progressed from a medical examination of the subject followed by evaluation, diagnosis, prognosis, intervention and treatment plan, and finally re-examination in order of precedence. Problems in the participant's functional activities, difficulties in changes from sitting postures into standing postures, and maintaining standing postures were determined as primary restrictions on activities and the improvement of these activities was set up as a goal through discussions with the patient. Interventions were mainly implemented to reduce the pusher syndrome with visual feedback provided using mirrors and exercises focusing on leaning in order to maintain posture while sitting. Changes from supine postures to sitting postures and the degree of changes in maintaining standing postures were compared between before and after the intervention by measuring times in the same environment and the degree of pusher syndrome was measured using the SCP tool. The process of this clinical practice was documented. The SCP score that indicates the degree of changes in the participant's pusher syndrome changed from 3.75 points to 0.8 point indicating a decrease in pushing. Among functional activities, posture changes from sitting postures to standing postures and maintaining standing postures were improved. In addition, since the patient could maintain standing postures, the patient could walk indoors. In this case study, mirrors and body posture control training used as interventions to relieve pusher syndromes can be easily applied in clinics to examine the form of functional recovery. The results indicated that these intervention methods were effective and thus it is thought that the results can be used as basic data to utilize these intervention methods diversely. In addition, the documentation of patient/client management was applied as actual documentation in Korean and based on the results, we could show decision making processes for patients' functional goals and objectively explain problems, prognoses and changes made through the interventions.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.4
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• pp.318-331
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• 1995

The c - axis oriented single crystal of $LiNbO_3$ and $LiNbO_3$ : 5mol%MgO was success-fully grown by Floating zone method using halogen lamp as a heat source. The effects of the sintering condition of the feed rod and the atmosphere gas during the crystal growth on the be havior of the feed rod/melt interface were studied for growing crystal with the high quality, and then, the optimum growth conditions were determined by studying the experimental param eters, such as gas flow rate, pulling rate, rotation speeds of the feed rod and the seed. The grown crystals were analyzed using the chemical etching to observe the tch pattern and the ICP (Inductively Coupled Plasma) to determine the composition uniformity and the impurity content of Fe. The effects of additive (5 mol % MgO) on the transmittance and refractive index was, also, analyzed. In order to compare the nonlinear optical oharacteristics of $LiNbO_3$ with those of the other optical materials, the nonlinear optical refractive index ($n_2$) was calcu l lated using the measured refractive index.

• Journal of Oral Medicine and Pain
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• v.32 no.1
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• pp.35-43
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• 2007

This study was conducted to investigate the preventing effects of OPB (water extracts of Rehmannia glutinosa Libosch and Eleutherococcus senticosus Max) on bone loss in ovariectomized rats. Twenty Sprague Dawley rats of 13 week-old were divided into two groups: control group (ovariectomized, OVX)) and experimental group (OVX + OPB). The preventing effects of OPB on bone loss, OPB were fed with 100 mg OPB/kg body weight from 3 days after ovariectomization. The duration of the treatment period was 8 weeks. All bone mineral density, bone mineral content indices and bone strength indices measured by peripheral quantitative computerized tomography (pQCT) and serum bone marker assessment were carried out at end of experiment. pQCT scanning showed that OVX induced a significant decrease in cancellous bone mineral density in the proximal tibia ($-29.8{\pm}3.0%$). These decreases were significantly prevented by the administration of OPB 100 mg/kg ($-21.4{\pm}2.3%$. p<0.05). Bone strength indices showed significant difference between OVX and OPB treated rats (anti-fracture, anti-twisting, p<0.05). These data suggested that administration of OPB inhibited the loss of bone in OVX rats. CTx level were lower than in the OPB-treated animals compared with OVX. However there was no significant difference between OVX and OPB treated OVX rat. Our results suggest that OPB is effective in preventing the development of bone loss induced by ovariectomy in rats.

• Journal of Periodontal and Implant Science
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• v.37 no.1
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• pp.91-102
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• 2007

The long term success of periodontal treatment is dependent upon the effectiveness of the main-tenance care program after active treatment. The purpose of this study was to evaluate whether nutraceutical containing PRF-K2 as natural product from plant and seaweed has beneficial effects on clinical parameters, gingival crevicular fluid (GCF) volume and GCF cytokine levels during main- tenance phase after periodontal treatment. Among the generally healthy and non-smoking. moderate to severe chronic periodontitis patients during maintenance phase in Department of Periodontics, Chonnam National University Hospital, twenty eight patients took nutraceutical containing PRF-K2 (Oscotec Inc. Cheonan, Korea) for 3 months as experimental group and sixteen patients received only maintenance care as control group. Clinical examination and GCF collection were performed at baseline, 1, 2 and 3 months of experiment. Total amounts and concentrations of GCF IL-1{\beta}, IL-1ra and $PGE_2$ were evaluated using ELISA kit. In probing pocket depth, experimental group showed the tendency of more reduction than control group after 3 months of experiment. Sulcus bleeding index (SBI) and GCF volume were significantly decreased in experimental group(p<0.05), whereas they were increased in control group. GCF IL-1{\beta} level tended to decrease in both experimental and control group and IL-1ra concentration tended to increase in experimental group and to decrease in control group. IL-1ra/IL-1{\beta} ratio tended to increase in experimental group and to decrease in control group during experimental period. GCF $PGE_2$ amount did not show any change in experimental group and tended to increase in control group. These results suggest that nutraceutical supplement which contain PRF-K2 could improve perio-dontal condition during maintenance phase after periodontal therapy.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.189-196
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• 2012

The heavy moderator acts as the ultimate heat-sink in an operating CANDU reactor. HUKINS has been developed to investigate moderator flow patterns. HUKINS consists of a 38.4-mm-thick cylindrical shell with a 0.95 m inner diameter and 88 sus-tubes that produce a total heat of 10 kW. A chemical visualization method was selected to estimate the occurrence of typical moderator flow patterns. Momentum-dominated flow, mixed flow, and buoyancy-dominated flow are detected under conditions of a heat load of 7.7 kW and input mass flow rates of 4, 7, and 11 L/min. The experimental results are similar to the results of a CFD simulation that consisted of approximately 1.9 million grids and was conducted using the k-${\varepsilon}$ turbulence model. Therefore, both the present experiments and simulations using HUKINS, a 1/8-scale model, represent all three important flow patterns expected in the real CANDU6 reference reactor. Thus, it has been demonstrated that HUKINS could be useful in the study of CANDU6 moderator circulation.