• Radiation Oncology Journal
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• v.29 no.2
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• pp.107-114
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• 2011

Purpose: To assess the degree and clinical impact of location error of the dens on the X-axis during radiotherapy to brain and head and neck tumors. Materials and Methods: Twenty-one patients with brain tumors or head and neck tumors who received three-dimensional conformal radiation therapy or intensity-modulated radiation therapy from January 2009 to June 2010 were included in this study. In comparison two-dimensional verification portal images with initial simulation images, location error of the nasal septum and the dens on the X-axis was measured. The effect of set-up errors of the dens was simulated in the planning system and analyzed with physical dose parameters. Results: A total of 402 portal images were reviewed. The mean location error at the nasal septum was 0.16 mm and at the dens was 0.33 mm (absolute value). Location errors of more than 3 mm were recorded in 43 cases (10.7%) at the nasal septum, compared to 133 cases (33.1%) at the dens. There was no case with a location error more than 5 mm at the nasal septum, compared to 11 cases (2.7%) at the dens. In a dosimetric simulation, a location error more than 5 mm at the dens could induce a reduction in the clinical target volume 1 coverage (V95: 100%${\rightarrow}$87.2%) and overdosing to a critical normal organ (Spinal cord V45: <0.1%${\rightarrow}$12.6%). Conclusion: In both brain and head and neck radiotherapy, a relatively larger set-up error was detected at the dens than the nasal septum when using an electronic portal imaging device. Consideration of the location error of the dens is necessary at the time of the precise radiation beam delivery in two-dimensional verification systems.

• Progress in Medical Physics
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• v.9 no.3
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• pp.137-141
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• 1998

The purposes of this report are to evaluate whether lead ball and steel ball could be used as protective material of radiation and to acquire physical data of them for protecting 4-10 MV X-ray beams. Lead balls of diameter 2.0～2.5mm or steel balls of diameter 1.5～2.0 mm were filled in an acrylic box of uniform width. An MV radiograph of metal balls in a box were taken to ascertain uniformity of ball distribution in the box. Average density of metal ball and linear attenuation coefficient of metal balls for 4～10 MV X -rays were measured. At the time of measurement of linear attenuation coefficient, Farmer ionization chamber was used and to minimize the scatter effect, distance between the ball and the ionization chamber was 70 cm and field size was 5.5cm${\times}$5.5cm. For comparison, same parameters of lead and steel plates were measured. The distribution of metal balls was uniform in the box. The density of a mixture of lead-air was 6.93g/cm$^3$, 0.611 times density of lead, and the density of a mixture of steel-air was 4.75g/cm$^3$, 0.604 times density of steel. Half-value layers of a mixture of lead-air were 1.89 cm for 4 MV X-ray, 2.07 cm for 6 MV X-ray and 2.16 cm for 10 MV X-ray, and approximately 1.64 times of HVL of lead plate. Half-value layers of a mixture of steel-air were 3.24 cm for 4 MV X-ray, 3.70 cm for 6 MV X-ray and 4.15 cm for 10 MV X-ray, and approximately 1.65 times of HVL of lead plate. Metal balls can be used because they could be distributed evenly. Average densities of mixtures of lead-air and steel-air were 6.93g/cm$^3$, 4.75g/cm$^3$ respectively and approximately 1.65 times of densities of lead and steel. Product of density and HVL for a mixture of metal-air are same as the metal.

• Journal of Nutrition and Health
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• v.43 no.2
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• pp.171-180
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• 2010

This study aims at investigating the health and nutritional status of the adults according to frequency of eating out. One day food intake data were collected by 24 hr recall dietary survey and body size, blood pressure and some blood lipids and other constituents were measured on 137 Daejeon metropolitan citizens 20 yrs old and above who visited Chungnam National University Hospital for physical examination during the period of December 6, to December 15, 2008. The frequency of eating out were categorized into four levels: less than once a week, once a week, 2-3 times a week, 4 times a week and above. Body mass Index, waist circumference, blood pressure, blood lipid, blood glucose, GPT and GOT did not showed any significant difference according to the frequency of eating out of the subjects. Though, systolic blood pressures and serum levels of total cholesterol and LDL-cholesterol showed a little tendency to be high in the subjects eating out 2-3 times a week. In the contrary, serum triglyceride level tended to be low in the same group. The subjects eating out 4 times a week and over took more total protein, animal protein, animal fat, phosphorus and vitamin $B_2$ than any other group. Also protein energy ratio was the highest in the group eating out 4 times a week and above and they took more animal food group, other food group, beverages teas and alcohols than other groups eating out. These results showed that higher frequency of eating out leads to higher intake of protein, fat, phosphorus, animal food groups and other food groups (oils, beverages, seasonings) and to lower intake of vitamin C and plant food groups. It, thus, suggested that the strategy for restaurant business is required to provide the menu substituted animal food by more plant food.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.67-72
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• 2018

This study was conducted to investigate a potential of Yellow poplar (Liriodendron tulipifera L.) as a raw material for the manufacturing of particleboard (PB) and oriented strandboard (OSB). PB panels were prepared at the parameters of $0.7g/cm^3$ density, 15 mm thickness, three-layer, $E_1$ grade urea-formaldehyde (UF) resin, emulsion wax, and hardener. OSB panels were manufactured with a density of $0.65g/cm^3$, thickness of 10 mm, and $E_1$ grade of UF resin. Particle size of the face layer of PB was 20~80 mesh with 7~9% moisture content (MC), while that of core-layer was 3~20 mesh with 3~5% MC, which was similar to the production condition of commercial PB. As a result, the manufactured PB panels with 15.8 mm thickness, $0.7g/cm^3$ density, and 5.8% MC satisfied the requirement of bending strength of 15 type PB of Korean Industrial Standard (KS F 3104). Both internal bonding (IB) strength and surface screw withdrawal resistance also satisfied the requirement of 18 type PB of the standard. But, the edge screw withdrawal resistance satisfied the requirement of 15 type PB of the standard. These differences in properties could be due to the slenderness ratio of raw particles. In case of OSB panels with 10.7 mm thickness, $0.68g/cm^3$ density, and 5.8% MC satisfied all the requirements of bending strength, screw withdrawal resistance, and IB strength of 18 type PB of the standard. These results suggest that Yellow poplar wood has a good potential as a raw material for the production of PB and OSB.

• Journal of dental hygiene science
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• v.14 no.2
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• pp.114-122
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• 2014

The purpose of this study was to analyze the effect of mediating variables on the relationship between job stress and stress response. A survey was conducted to 243 clinical dental hygienists from January 15, 2013 to March 20, 2013 and the data were analyzed using t-test, one-way ANOVA, Pearson's correlation analysis, and hierarchical multiple regression analysis. The subjects who worked in poor working environment, had high level of role conflict and overload and aggressive nature showed high stress responsivity (p<0.01). The variable that showed mediation effect on the relationship between job stress and physical discomfort, depression was shown to be personality type (p<0.05). Also, the variable that showed mediation effect on the relationship between job stress and turnover intention was social support (p<0.05). According to the results, personality type and social support were shown to be important parameters when it came to the relationship between job stress and stress response. Therefore, in order to reduce negative outcomes caused by stress, it is suggested to provide an educational opportunity on self-control management while increasing social support from the organizational and structural level. Especially, it is asked to expand the system that provides encouragement and recognition to feel the sense of achievement in the course of their duty execution.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.863-870
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• 2016

We investigated the physical/chemical phenomena that a slow loss of $CO_2$ inventory into sodium after the sodium-$CO_2$ boundary failure in printed circuit heat exchangers (PCHEs), which is considered for the supercritical $CO_2$ Brayton cycle power conversion system of a sodium-cooled fast reactor (SFR). The first phenomenon is plugging inside narrow sodium channels by micro cracks and the other one is damage propagation referred to as wastage combined with the corrosion/erosion effect. Experimental results of plugging shows that sodium flow immediately stopped as $CO_2$ was injected through the nozzle at $300{\sim}400^{\circ}C$ in 3 mmID sodium channels, whereas sodium flow stopped about 60 min after $CO_2$ injection in 5 mmID sodium channels. These results imply that if pressure boundary of sodium-$CO_2$ fails a narrow sodium channel would be plugged by reaction products in a short time whereas a relatively wider sodium channel would be plugged with higher concentration of reaction products. Wastage by the erosion effect of $CO_2$ (200~250 bar) hardly occurred regardless of the kinds of materials (stainless steel 316, Inconel 600, and 9Cr-1Mo steel), temperature ($400{\sim}500^{\circ}C$), or the diameter of the $CO_2$ nozzle (0.2~0.8 mm). Velocities at the $CO_2$ nozzle were specified as Mach 0.4~0.7. Our experimental results are expected to be used for determining the design parameters of PCHEs for their safeties.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.4
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• pp.439-446
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• 2007

This study was performed to investigate the effect of long-term administration of Saengshik on growth parameters of growing rats. Male Sprague-Dawley rats were fed on AIN-93G basal diets for 12 weeks and assigned to the following groups: rats administrated orally with Saengshik at the dose of 1g/kg/day (1xJS ), 2g/kg/day (2xJS), 4g/kg/day (4xJS) and distilled water (Control). Rats were sacrificed at 4, 8, 12 weeks after oral administration. Bone mineral density (BMD) and bone mineral contents (BMC) were measured by PIXImus densitometry and serum insulin-like growth factor-1 (IGF-1) concentration were determined by using EIA method. Body weight and food intake did not show significant changes within groups for 12 weeks. Physical longitudinal growth indexes, body length and femur length were significantly increased in Saengshik-administered groups at 12 weeks, in which BMD and BMC also significantly increased. Also, in blood IGF-1 level, Saengshik-administered groups were remarkedly higher than control group at 4 week (p<0.001), in which significantly higher at 8 week and 12 week. These results suggest a close relation between administration of Saengshik and increment of longitudingal bone growth. Therefore, as the result of this study, it could be expected that the administration of Saengshik for 12 weeks is helpful to the increase of longitudinal growth and growth factors in rats. Furthermore, we propose that the consumption of Saengshik as dietary supplementation may promote to increase in longitudinal bone growth in growing children.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.375-375
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• 2010

CdTe as an absorber material is widely used in thin film solar cells with the heterostructure due to its almost ideal band gap energy of 1.45 eV, high photovoltaic conversion efficiency, low cost and stable performance. The deposition methods and preparation conditions for the fabrication of CdTe are very important for the achievement of high solar cell conversion efficiency. There are some rearranged reports about the deposition methods available for the preparation of CdTe thin films such as close spaced sublimation (CSS), physical vapor deposition (PVD), vacuum evaporation, vapor transport deposition (VTD), closed space vapor transport, electrodeposition, screen printing, spray pyrolysis, metalorganic chemical vapor deposition (MOCVD), and RF sputtering. The RF sputtering method for the preparation of CdTe thin films has important advantages in that the thin films can be prepared at low growth temperatures with large-area deposition suitable for mass-production. The authors reported that the optical and electrical properties of CdTe thin film were closely connected by the thickness-uniformity of the film in the previous study [1], which means that the better optical absorbance and the higher carrier concentration could be obtained in the better condition of thickness-uniformity for CdTe thin film. The thickness-uniformity could be controlled and improved by the some process parameters such as vacuum level and RF power in the sputtering process of CdTe thin films. However, there is a limitation to improve the thickness-uniformity only in the preparation process [1]. So it is necessary to introduce the external or additional method for improving the thickness-uniformity of CdTe thin film because the cell size of thin film solar cell will be enlarged. Therefore, the authors firstly applied the chemical mechanical polishing (CMP) process to improving the thickness-uniformity of CdTe thin films with a G&P POLI-450 CMP polisher [2]. CMP process is the most important process in semiconductor manufacturing processes in order to planarize the surface of the wafer even over 300 mm and to form the copper interconnects with damascene process. Some important CMP characteristics for CdTe were obtained including removal rate (RR), WIWNU%, RMS roughness, and peak-to-valley roughness [2]. With these important results, the CMP process for CdTe thin films was performed to improve the thickness-uniformity of the sputtering-deposited CdTe thin film which had the worst two thickness-uniformities of them. Some optical properties including optical transmittance and absorbance of the CdTe thin films were measured by using a UV-Visible spectrophotometer (Varian Techtron, Cary500scan) in the range of 400 - 800 nm. After CMP process, the thickness-uniformities became better than that of the best condition in the previous sputtering process of CdTe thin films. Consequently, the optical properties were directly affected by the thickness-uniformity of CdTe thin film. The absorbance of CdTe thin films was improved although the thickness of CdTe thin film was not changed.

• Tuberculosis and Respiratory Diseases
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• v.40 no.3
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• pp.283-291
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• 1993

Background: Long-term low flow oxygen therapy not only increases survival, but also improves the quality of life in patients with chronic obstructive pulmonary disease (COPD) with chronic hypoxemia. For the assessment and improvement of the status of home oxygen therapy, we analyzed clinical experience of 26 patients who have been administered low flow oxygen at home. Method: Twenty-six patients (18 men and 8 women) who have been received long-term oxygen therapy (LTOT) at home were examined. We reviewed physical characteristics, clinical history, pulmonary function test, ECG, arterial blood gas analysis, hemoglobin and hematocrit, types of oxygen devices, inhalation time per day, concentration of administered $O_2$, duration of $O_2$ therapy, and problems in the home oxygen therapy. Results: The underlying diseases of patients were COPD 14 cases, far advanced old pulmonary tuberculosis 9 cases, bronchiectasis 2 cases, and idiopathic pulmonary fibrosis 1 case. The reasons for LTOT at home were noted for cor pulmonale 21 cases, for dyspnea on exertion and severe ventilatory impairment 4 cases, and for oxygen desaturation during sleep 1 case. The mean values of aterial blood gas analysis before home oxygen therapy were $PaO_2$ 57.7 mmHg, $PaCO_2$ 48.2 mmHg, and $SaO_2$ 87.7%. And the mean values of each parameters in the pulmonary function test were VC 2.05 L, $FEV_1$ 0.92 L, and $FEV_1$/FVC% 51.9%. Nineteen patients have used oxygen tanks as oxygen devices, 1 patient oxygen concentrator, 2 patients oxygen tank and liquid oxygen, and other 4 patients oxygen tank together with portable oxygen. The duration of oxygen therapy was below 1 year in 3 cases, 1~2 years in 15 cases, 3~5 years in 6 cases, 9 years in 1 case, and 10 years in 1 case. All patients have inhalated oxygen with flow rate less than 2.5 L/min. And only 10 patients have inhalated oxygen more than 15 hours per day, but most of them short time per day. Conclusion: For the effective oxygen administration, it is necessary that education for long-term low flow oxygen therapy to patients, their family and neighbor should be done, and also the institutional backup for getting convenient oxygen devices is required.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.401-412
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• 2016

It is extremely difficult to apply conventional grouting methods to subsea tunnelling construction in the high water pressure condition. In such a condition, the rapid artificial freezing method can be an alternative to grouting to form a watertight zone around freezing pipes. For a proper design of the artificial freezing method, the influence of salinity on the freezing process has to be considered. However, there are few domestic tunnel construction that adopted the artificial freezing method, and influential factors on the freezing of the soil are not clearly identified. In this paper, a series of laboratory experiments were performed to identify the physical characteristics of frozen soil. Thermal conductivity of the frozen and unfrozen soil samples was measured through the thermal sensor adopting transient hot-wire method. Moreover, a lab-scale freezing chamber was devised to simulate freezing process of silica sand with consideration of the salinity of pore-water. The temperature in the silica sand sample was measured during the freezing process to evaluate the effect of pore-water salinity on the frozen rate that is one of the key parameters in designing the artificial freezing method in subsea tunnelling. In case of unfrozen soil, the soil samples saturated with fresh water (salinity of 0%) and brine water (salinity of 3.5%) showed a similar value of thermal conductivity. However, the frozen soil sample saturated with brine water led to the thermal conductivity notably higher than that of fresh water, which corresponds to the fact that the freezing rate of brine water was greater than that of fresh water in the freezing chamber test.