• Journal of dental hygiene science
• /
• v.12 no.3
• /
• pp.253-258
• /
• 2012

Dental amalgam is an alloy composed of a mixture of approximately equal parts of elemental liquid mercury and an alloy powder. Amalgam has been the most popular and effective restorative material used in dentistry. Despite the long history and popularity of dental amalgam as a restorative material, there have been periodic concerns regarding the potential adverse health effects arising from exposure to mercury in amalgam. Since children are more at risk for mercury toxicity, we aimed to assess the association between dental amalgam filling and urinary mercury concentration in children. 581 of elementary school children in grades 1st4th were conveniently recruited from two schools located in Daegu city, Korea. To obtain dental caries experience states, oral examination were conducted using the full term for DFS index, number of amalgam filling surfaces and the type of filling materials. A questionnaire was used to collect information about general characteristics and the frequencies of tooth brushing, gum chewing and fish/seafood consumption. The statistical analysis was done using the SPSS 18.0 program. The mean urinary mercury concentration in children having more surfaces was highest. As a results Urinary mercury concentration of children who have 79 teeth of amalgam filling and more than 10 is higher than without amalgam filling. The number of amalgam filling surface is closely related with urinary mercury concentration.

• Korean Journal of Weed Science
• /
• v.14 no.3
• /
• pp.171-175
• /
• 1994

Physiological changes in Eleocharis kuroguwai Ohwi as affected by bensulfuron-methyl {Methyl 2-[[[[[(4, 6-dimethoxy-2-pyrimidinyl)amino]carbonyl]amino] sulfonyl]methyl]benzoate} was determined to relate the characteristics with regrowth behavior. There were no changes in relative growth rate(RGR) during the period of growth cessation after application of bensulfuron-methyl. RGR's of the growth ceseased plants caused at 39 and 51 g/ha began to increase in between 25 and 30 days after application (DAA) and between 30 and 35 DAA, respectively. In untreated plant tuber carbohydrate rapidly decreased right after emergence and almost consumed within 40 days. There was no carbohydrate consumption during the period of growth cessation in bensulfuron-methyl-applied plant, but the content started to rapidly decrease with regrowth. Tuber viability lasted for 30 days in untreated plant, while tubers were viable for 60 and 70 days after application of bensulfuron-methyl at 39 and 51 g/ha, respectively. During the period of growth cessation the plants kept minimum respiration and photosynthesis, but with regrowth respiration and photosynthesis were resumed and rapidly increased.

• The Korean Journal of Food And Nutrition
• /
• v.29 no.3
• /
• pp.392-403
• /
• 2016

The purpose of this study was to investigate the relations between HbA1c level and health risk factor. For analysis, 330 elderly women aged 65 years and over were recruited in Jeonla province, Korea. The subjects were classified into two groups according to their HbA1c level; the diabetic group (HbA1c level${\geq}6.5%$, n=68, 20.6%) and control group (HbA1c level<6.5%, n=262, 79.4%). Demographic characteristics were collected, as well as information on physical measurements, blood tests for biochemical indicators, a health status and health-related life style, dietary behavior, favorite food groups, consumption frequency of food groups and nutrient intake. Educational level of the diabetic group was significantly lower than that of the control group. The height of the diabetic group was shorter, and percentage fat of the diabetic group was higher than those of the control group. In the diabetic group, the higher concentrations of creatinine and activity of alkaline phosphatase were found to be significantly unfavorable factors. Therefore, the diabetic group was assumed to be at risk of decreased liver and renal function. The self-rated health level of the diabetic group has a declining tendency, while the medicine intake was significantly higher than that of the control group, but there are no significant differences in visiting frequency of hospital and community health center. The distribution of physical activity showed a significant difference between the groups. Although there are no significant differences in nutrient intake, the diabetic group had relatively inferior nutrient intake of diet, especially vitamin C, as contrasted with the control group. In conclusion, the weight control and increasing physical activity may be effective in the prevention of the diabetes and continuous education and intervention by specialized nutritionists will be needed for diabetic patients. These results could be useful to plan effective strategies to increase the health-life expectancy and the prevention of the diabetes of Korean elderly people living in rural areas.

• Food Science of Animal Resources
• /
• v.34 no.3
• /
• pp.395-402
• /
• 2014

The current study was conducted to identify technology for the production of high quality pork, based on the meat consumption habits of consumers. Macsumsuk, a type of kaolinite (a clay mineral), and/or a mixture of herbs (Mori Folium, Sophorae Radix, Glycyrrhizae Radix, Citri Leiocarpae Exocarpium, and Pogostemi Herba) were added to the diets of fattening pigs. Sixty barrow pigs (4 kinds of treatment ${\times}5$ pigs/treatment ${\times}3$ replicates) were randomly assigned to either the Control (no additives), T1 (3% Macsumsuk), T2 (3% Herb mixtures), or T3 (3% Macsumsuk + 3% Herb mixtures) groups, and were fed the diets for 60 d. Dressed weights were in the order of T1 ($93.40{\pm}4.68kg$) > T2 ($91.40{\pm}6.52kg$) > Control ($88.80{\pm}1.57kg$) > T3 ($86.80{\pm}2.01kg$). Back-fat thickness of the Control animals ($23.2{\pm}1.03mm$) was significantly greater than that of the various treatment groups (p<0.01). Numeric values representing the carcass yield and quality grade were higher for all the treated groups than the Control group, thought the difference was not statistically significant. Crude fat content was significantly higher in the Control group ($2.23{\pm}0.34%$) than in the treated groups (p<0.05). The addition of both Macsumsuk and herb mixtures into the diets of the pigs significantly reduced cooking loss of the pork compared to the Control (p<0.05). No statistically significant changes were observed in the shear force (average $5.87{\pm}0.54kg/cm^2$), water holding capacity (average $54.59{\pm}3.16%$), or CIE values of the pork, whereas cholesterol levels significantly decreased (p<0.01) in those fed Macsumsuk and/or the herb mixtures. No significant changes in fatty acid composition, total saturated fatty acid (SFA), total unsaturated fatty acid (UFA), or UFA/SFA ratios were observed by any of the treatments. In conclusion, the results obtained from this study suggest that the addition of Macsumsuk and/or herb mixtures into the diets of growing and fattening pigs improves the pork quality by reducing cooking loss, decreasing cholesterol content, and enhancing sensory characteristics.

• Fire Science and Engineering
• /
• v.33 no.4
• /
• pp.35-40
• /
• 2019

In this study, the mass flow rate of the heat release rate equation, which is the major factor of the oxygen consumption method, was analyzed for the fundamental investigation of the cone-calorimeter (5 m length and 0.3 m diameter). The shapes of a completely empty inside, 3 mm pore diameter mesh and pore diameter 10 mm honeycomb with 0.76 porosity were constructed using the cone-calorimeter. To calculate the mass flow rate, four bi-directional probes and thermocouples were installed in a uniform position in the vertical direction of flow. The velocity gradient and flow perturbation were measured from the increase in Reynolds number. As the flow capacity increased, the speed gradient increased in all three shapes relative to the turbulence intensity. In addition, the deviation of extended uncertainty to the mass flow was completely low in the order of empty space, mesh (d_p = 3 mm) and honeycomb (d_p = 10 mm and 𝜖 = 0.76) at the 95% confidence level. The results can be used in designs to improve the flow stability of the cone calorimeter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.03a
• /
• pp.16-16
• /
• 2010

GaN-based light-emitting diodes (LEDs) are attracting great interest as candidates for next-generation solid-state lighting, because of their long lifetime, small size, high efficacy, and low energy consumption. However, for general illumination applications, the external quantum efficiency of LEDs, determined by the internal quantum efficiency (IQE) and the light extraction efficiency, must be further increased. The IQE is determined by crystal quality and epitaxial layer structure and high value of IQE more than 70% for blue LEDs have been already reported. However, there is much room for improvement of light extraction efficiency because most of the generated photons from active layer remain inside LEDs by total internal reflection at the interface of semiconductor with air due to the high refractive index difference between LEDs epilayer (for GaN, n=2.5) and air (n=1). The light confining in LEDs will be reabsorbed by the metal electrode or active layer, reducing the efficacy of LEDs. Here, we present the first demonstration of enhanced light extraction by forming a MgO nano-pyramids structure on the surface of vertical-LEDs. The MgO nano-pyramids structure was successfully fabricated at room temperature using conventional electron-beam evaporation without any additional process. The nano-sized pyramids of MgO are formed on the surface during growth due to anisotropic characteristics between (111) and (200) plane of MgO. The ZnO layer with quarter-wavelength in thickness is inserted between GaN and MgO layers to increase the critical angle for total internal reflection, because the refractive index of ZnO (n=1.94) could be matched between GaN (n=2.5) and MgO (n=1.73). The MgO nano-pyramids structure and ZnO refractive-index modulation layer enhanced the light extraction efficiency ofV-LEDs with by 49%, comparing with the V-LEDs with a flat n-GaN surface. The angular-dependent emission intensity shows the enhanced light extraction through the side walls of V-LEDs as well as through the top surface of the n-GaN, because of the increase in critical angle for total internal reflection as well as light scattering at the MgO nano-pyramids surface.

• Environmental and Resource Economics Review
• /
• v.19 no.3
• /
• pp.597-632
• /
• 2010

There is general agreement that global warming is occurring and that the main contributor to this probably is the buildup of green house gasses, GHG, in the atmosphere. Two main contributors are the utilization of fossil fuels and the deforestation of many regions of the world. The burning of fossil fuels increases atmospheric carbon while the burning of fuel-wood reducing fossil fuel consumption along with its forest source maintain an atmospheric carbon level. The standing timber in the forests is a carbon sink, as are wood buildings and structures, and fossil fuel in the ground. This paper is designed to examine a number of current issues related to mitigating the global warming problem through forestry. For this purpose, we develop a modeling approach by integrating timber market, fossil fuel market and carbon cycling model. We use discrete time optimal control theory to identify optimal time paths, the laws of motion, and stationary stats solutions of endogenous variables in the model. On the basis of these results, we identify the optimal amounts of subsidies to be provided or taxes to be imposed by the regulatory agency to mitigate atmospheric carbon accumulation. We also present a numerical example to help illustrate the characteristics of variables in the model when the social cost for atmospheric carbon incrementally shifts upward. A surprising result is that the social cost function for atmospheric carbon has a very smaller impact on the optimal rotation period than previous literature suggested.

• Journal of Convergence for Information Technology
• /
• v.10 no.7
• /
• pp.33-40
• /
• 2020

This work tackles the problem of conventional reinforcement learning scheme which has a relatively long training time to reduce energy consumption in underwater network. The enhanced scheme adjusts the learning range of reinforcement learning based on distance estimation. It can be reduce the scope of learning. To take account the fact that the distance estimation may not be accurate due to the underwater wireless network characteristics. this research added noise in consideration of the underwater environment. In simulation result, the proposed AQ-NAV scheme has completed learning much faster than existing method. AQ-NAV can finish the training process within less than 40 episodes. But the existing method requires more than 120 episodes. The result show that learning is possible with fewer attempts than the previous one. If AQ-NAV will be applied in Underwater Networks, It will affect energy efficiency. and It will be expected to relieved existing problem and increase network efficiency.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.42 no.6
• /
• pp.23-36
• /
• 2005

PLLs have been widely used for many applications including communication systems. This paper presents a VCO with an improved negative skewed delay scheme and a PLL using this VCO. The proposed VCO and PLL are intended for replacing traditional LC oscillators and PLLs used in communication systems and other applications. The circuit designs of the VCO and PLL are based on 0.18um CMOS technology with 1.8V supply voltage. The proposed VCO employs subfeedback loops using pass-transistors and needs two opposite control voltages for the pass transistors. The subfeedback loops speed up oscillation depending on the control voltages and thus provide a high oscillation frequency. The two voltage controls have opposite frequency gain characteristics and result in low phase-noise. The 7-stage VCO in 0.18um CMOS technology operates from $3.2GHz\~6.3GHz$ with phase noise of about -128.8 dBc/Hz at 1MHz frequency onset. For 1.8V supply voltage, the current consumption is about 3.8mA. The proposed PLL has dual loop-filters for the proposed VCO. The PLL is operated at 5GHz with 1.8V supply voltage. These results indicate that the proposed VCO can be used for radio frequency operations replacing LC oscillators. The circuits have been designed and simulated using 0.18um TSMC library.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.39 no.6
• /
• pp.34-42
• /
• 2002

In this paper, we propose a temperature independent the detective voltage source in voltage detector. The value of a detective voltage source is designed to become m times of silicon bandgap voltage at zero absolute temperature. By properly choosing the temperature coefficient of diode, the temperature coefficient of a concave voltage nonlinearities generated by the ${\Delta}V_{BE}$ section of diode between base and emitter of transistors with a different area can be summed with convex nonlinearities the $V_{BE}$ voltage to achieve the near zero temperature coefficient of the detective voltage source. We designed that the value of a detective voltage can be varied by ${\Delta}V_{BE}$, the $V_{BE}$multiplier circuit and resistor. In order to verify the performance of a proposed detective voltage source, we manufactured the voltage detector IC for 1.9V which is fabricated in $6{\mu}m$ Bipolar technology and measured the operating characteristics, the temperature coefficient of a detective voltage. To reduce the deviation of a detective voltage in the IC process step, we introduced a trimming technology, ion implantation and an isotropic etching. In manufactured IC, the detective voltage source could achieve the stable temperature coefficient of 29ppm/$^{\circ}C$ over the temperature range of -30$^{\circ}C$ to 70$^{\circ}C$. The current consumption of a voltage detector constituted by the proposed detective voltage source is $10{\mu}A$ from 1.9V-supply voltage at room temperature.