• Journal of Dental Rehabilitation and Applied Science
• /
• v.19 no.1
• /
• pp.27-33
• /
• 2003

Excessive heat generation at the implant-bone interface may cause irreversible bone damage and loss of osseointegration. The effect of heat generation in vitro at the implant surface caused by abutment reduction with high-speed dental turbine was examined. Titanium-alloy abutments connected to a titanium alloy screw-implant embedded in an acrylic-resin block in a $37^{\circ}C$ water bath were prepared. Temperature changes were recorded via embedded thermocouples at the cervix and apex of the implant surface. Analysis of variance for repeated measures was used to compare seven treatment groups. Fifty seconds of continuous cutting with air and water coolant caused a mean temperature increase of $1.24^{\circ}C$ at apex and $5.77^{\circ}C$ at cervix. Similar intermittent cutting caused increase of $2.50^{\circ}C$ at apex and $1.64^{\circ}C$ at cervix. But, continuous cutting with air coolant caused a mean temperature increase of $6.47^{\circ}C$ at apex and $5.77^{\circ}C$ at cervix. Similar intermittent cutting caused increase of $6.47^{\circ}C$ at apex and $5.77^{\circ}C$ at cervix. Preparation of implant abutment does not lead to detrimental effect on peri-implant tissues provided that adequate cooling. However, without water cooling, extreme overheating could be provoked, reaching the critical temperature that would lead to irreversible bone damage within only a few seconds.

• Korean Journal of Construction Engineering and Management
• /
• v.19 no.2
• /
• pp.96-106
• /
• 2018

The government adopted activation policy of real estate to overcome low economic growth rate. Real estate activation plan adopted by the government raised credit limit by lowering the regulation, and reduced real estate investment cost by reducing the base rate. Also, delayed transfer tax on multi-house owner to activate real estate investment and resolved purchase right resale. Relief of real estate regulate caused increase of housing sales and price increase, and the real estate market changed to overheating aspect such as premium upon completion of lot sale in a short time. Such market atmosphere greatly increased household debs as owners own houses based on 'financial debt' instead of their income. Since 2017, real estate policy was reinforced to reduce household debts and lending rate was raised due to rise of base rate, accordingly, burden of household debt is expected to increase. This research suggested a plan for the Financial Supervisory Service to efficiently manage the financial world by analyzing the cause and problem of household debs.

• KIEAE Journal
• /
• v.16 no.6
• /
• pp.167-172
• /
• 2016

Purpose: The solar water heater with natural circulation has been used for several decades in the world as it is automatically operated without a pump and controller and is easy to maintain and repair. After the subsidy was offered from 2012, the solar water heater with natural circulation is becoming increasingly popular in Korea. Recently, the development of a wall-integrated solar water heater, which improves the applicability of buildings and prevents the overheating in the summer, is being developed. On the other hand, the design and performance evaluation data of solar water heaters are very inadequate, and analysis of heat and flow is required to develop a new type of solar water heater. Method: Therefore, in this study, we proposed a new simplified system analysis model that reflects heat and pressure loss from the test results of KS B ISO 9806-1 (Solar collector test method), assuming that the collector is a simple pipe system, the validity of which was verified through experiments. Result: As a result, first, the RMSE of the system circulation flow rate and the average temperature of the inlet and outlet of the collector according to the experimental results and the simulation are 0.05563 and 0.88530, respectively, which are very consistent. Secondly, the mass flow rate is increased linearly with the increase of the solar radiation, and the mass flow rate is 0.0104 ~ 0.0180kg/s in the range of $200{\sim}380W/m^2$ of solar irradiance. Compared with the test flow rate 0.0764kg / s of the test collector, it showed a level of less than 20%.

• Journal of the Korean Electrochemical Society
• /
• v.15 no.1
• /
• pp.1-11
• /
• 2012

Recently lithium ion secondary batteries (LIB) have rapidly developed because of their advantages such as high energy densities and capacities. Among them, an electrical vehicle which is the one of the environmental-friendly transportation facilities has been received a great attention, but, it is needed to overcome several obstacles of the LIB performances. LIB is practically adapted to Hybrid Electric Vehicle (HEV), but the issues for high capacities, long life time and safety should be solved. Moreover, LIBs still have some possibilities of explosion in the case of overheating of the used organic electrolyte and overcharging of the cell. Hence, it is urgently needed to replace the liquid electrolytes into the solid electrolytes due to the safety issues. Therefore, in this review, we summarized and discussed the research trends of the solid electrolyte to solve the concerns of safety and capacity of LIBs and published patents and articles.

• Transactions of the KSME C: Technology and Education
• /
• v.2 no.1
• /
• pp.57-63
• /
• 2014

In this paper new air-cooling system utilizing Stirling engine was proposed for improving efficiency in solar photovoltaic power generation. The solar cell plate was equipped with semi-circular channel for air flow on the backside. Beta-type Stirling engine was installed on the plate and its flywheel was connected to a motor fan by a transmission belt. A forced convective air flow for heat radiation was generated by the operation of the self-starting Stirling engine. The performance tests for power generation of solar cell with or without the proposed air-cooling system were conducted under halogen lamp. From the experimental results, it was found that decline in output voltage of the solar cell with proposed cooling system was 25% less than that of the solar cell without cooling system.

• Fire Science and Engineering
• /
• v.22 no.2
• /
• pp.91-96
• /
• 2008

This research studied about the cause analysis of fire that was occurred in far infrared rays heater to base on the fire examples. Fire of electric heater was apt to commit error that handled an over-heating accident by judged molten mark in heat ray. Molten mark which was attached in heat ray was appeared to the form of layer short circuit by other metal material, but other metal material was not found beside the ingredient of heat wire which was mixed to an alloy of Fe-Cr-Al according to result of ingredient distribution by SEM/EDX. Also, the result of overheating experiment by layer short circuit and overvoltage showed higher febrility than normal, but there was no possibility of fire occurrence. This paper will be contributed to science for cause analysis of electric fire through analyzing physical, chemical and flame features of burnout heater on the basis of diagnosis of fire that was happened in infrared rays heater.

• Food Science of Animal Resources
• /
• v.29 no.1
• /
• pp.82-90
• /
• 2009

This study was carried out to evaluate the effects of microwave power level on cooking properties of ground pork patties (fat level: 20%). Each patty was cooked from a thawed state to $76.7^{\circ}C$ (center temperature) in a microwave oven with power levels of 40% (360 W), 60% (540 W), 80% (720 W), and 100% (full power, 900 W), respectively. Cooking rate increased with power level, and the non-uniformity also increased with time during cooking. Overheating at the edge of the patties was observed for all power levels, and maximum temperature differences in between the edge position and center position were found in patties cooked at the 900 W power level. Compositional properties, total cooking loss, and drip loss were not affected by power level, although moisture content was lower at the edge than at the center position. As the power level increased, the reduction in patty diameter of cooked patties increased while the reduction in patty thickness decreased. Pork patties cooked at lower power levels (360 W and 540 W) had higher shear force values than those cooked at higher power levels (720 W and 900 W). Few changes were observed in instrumental color values.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.11
• /
• pp.193-198
• /
• 2012

An LED converter used to operate an LED with high efficiency and long lifespan, activates an LED by keeping voltage and current constant. In spite of voltage drop by LED's overheating and over-voltage by damage of a power line and by circuit problem, most existing LED converters supply unchanged constant voltage and current to the LED. Eventually, LED is out of order because of over-voltage or over-current. To avoid the breakdown of an LED by over-voltage and over-current, we propose a new scheme which deactivate the PWM circuit in the event of over-current generating. The PWM circuit operates below the pre-determined level of current. While the over-voltage is generated in PWM circuit, the feedback circuit makes the PWM circuit stopped and therefore prevents LED from being damaged by over-voltage and over-current.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.10
• /
• pp.652-658
• /
• 2016

Thermal batteries use inorganic salt as electrolyte, which is inactive at room temperature. As soon as heat pellets are fired by an igniter, all the solid electrolytes are instantly melted into excellent ionic conductors. However, the abnormal heat generation by the igniter flame or heat pellets causes the thermal decomposition of the electrode and the melting of the anode, eventually leading to a thermal runaway, which results in overheating or explosion. The thermal runaway can be significantly reduced by the adoption of $Zr/BaCrO_4$ heat papers. In this study, the heat papers with various ratios of fuel (Zr) and oxidizer ($BaCrO_4$) were prepared by the paper-making process. We have investigated the calorimetric value, burning rate, and ignition sensitivity. The ignition test of heat pellets and the discharge test of thermal batteries were also carried out. At the composition of 40 wt.% of Zr, the heat papers showed the highest specific calorimetric value and burning rate. As a result, $Zr/BaCrO_4$ heat paper made by the paper-making process has shown the applicability for thermal batteries.

• Journal of Electrical Engineering and Technology
• /
• v.11 no.3
• /
• pp.781-789
• /
• 2016

Busbar has been used as electric conductor within extra high voltage (EHV) gas insulated switchgear (GIS), which makes EHV GIS higher security, smaller size and lower cost. However, the main fault of GIS is overheating of busbar connection parts, circuit breaker and isolating switch contact parts, which has been already restricting development of GIS to a large extent. In this study, a coupled magneto-flow-thermal analysis is used to investigate the thermal properties of GIS busbar in steady-state. A three-dimensional (3-D) finite element model (FEM) is built to calculate multiphysics fields including electromagnetic field, flow field and thermal field in steady-state. The influences of current on the magnetic flux density, flow velocity and heat distribution has been investigated. Temperature differences of inner wall and outer wall are investigated for busbar tank and conducting rod. Considering the end effect in the busbar, temperature rise difference is compared between end sections and the middle section. In order to obtain better heat dissipation effect, diameters of conductor and tank are optimized based on temperature rise simulation results. Temperature rise tests have been done to validate the 3-D simulation model, which is observed a good correlation with the simulation results. This study provides technical support for optimized structure of the EHV GIS busbar.