• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.866-872
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• 2010

In this paper, we developed a digital soldering station based on PID controller, which supply stable power by controlling the current of heater of soldering iron. The proposed system designed PID controller to converge quickly to the set up temperature by user, and regain the lost of heat by external factors quickly. PID controller, designed by Ziegler-Nichols' tuning method, decides triac's trigger timing using setting temperature and present temperature to control the phase of AC 24V power that supply to the heater. Also, we give the function that shows present temperature and setting temperature of iron, and working time by graphic LCD. And during the rest time, we decided the power saving and extension of iron tip by dropping to the optimal temperature. Two experiments had implemented in $25^{\circ}C$ laboratory to confirm the performance of proposed method. The first experiment took 12sec, 13sec, 16sec, 18sec, reaching to $200^{\circ}C$, $300^{\circ}C$, $400^{\circ}C$, $480^{\circ}C$ respectively which result showed shorten of rising time than previous method. In the loading experiment of $300^{\circ}C$, $400^{\circ}C$, $480^{\circ}C$ steady state showed temperature drop of $3.8^{\circ}C$, $4.1^{\circ}C$, $4.5^{\circ}C$ which result showed the low temperature deviation than previous method.

• Polymer(Korea)
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• v.28 no.3
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• pp.239-244
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• 2004

Effect of lubricants on the rheological and thermal properties of poly(butylene terephthalate) [PBT] were investigated. Calcium stearate and adipic acid glycol polyester (AhGP) were used as processing lubricants for PBT. Decrease of melt viscosity was accomplished by the addition of 1 wt％ of lubricants. It was understood that melt viscosity was affected by the enhancement of chain mobility of PBT with AhGP as an internal lubricant as well as the lubricity on processing equipment developed by calcium stearate as an external lubricant. Lubricants also influenced chain scission of PBT which caused the viscosity drop as well. In addition, lubricant is resulted in the lowering of thermal stability, however, this might be minimized by adding less than 3 wt％ of calcium stearate as a lubricant. As a consequence, calcium stearate as an external lubricant is more effective to control the melt viscosity of PBT with minimizing of chain scission and thermal instability in PBT.

• Journal of The Geomorphological Association of Korea
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• v.19 no.2
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• pp.133-143
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• 2012

To evaluate the kinetic energy of the raindrops, the drop size distribution and the terminal velocity of the raindrops had been measured from January to September 2010 using the laser-optical disdrometer in KIGAM, Daejeon, Korea. The relationship between kinetic energy (KE) and rainfall intensity (I) was computed as logarithmic and exponential model, respectively, under the rainfall intensity of about 142mm/h. The exponential model is more suitable for the relationship of KE-I than the logarithmic model, because the exponential model presented better fit for KE over 50mm/h of rainfall intensity. Meanwhile, the differences of the total kinetic energy existed in rainfall events with almost same total rainfall depth, and KE values of Daejeon at high rainfall intensity underestimated rather than the others under temperate climate. Therefore, these differences of KE in rainfall events and geographical regions imply the result from the variations of rainfall intensity within a rainfall event.

• International Area Studies Review
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• v.20 no.1
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• pp.23-51
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• 2016

This study analyzed the expected economic effects of the Korea-GCC FTA and sought strategies for industrial cooperation. To see the economic effects of Korea-GCC FTA, we analysed the effect of the oil tariff reduction of economy by Vector Autoregression(VAR) model. The estimation results shows that following the abolishment of the tariff on crude oil imports, GDP, GNI and consumption are expected to grow by 0.212%, 0.389% and 0.238%, respectively. Meanwhile, investment, export and import are estimated to drop by 0.462%, 0.413% and 0.342%, respectively. As for prices, producer prices are to rise by 6.356%p, whereas consumer prices fall by 2.996%p. In short, the Korea-GCC FTA and resultant abolishment of the tariff on crude oil imports followed by the decline in crude oil prices will result in declining prices whilst macroeconomic indices, such as GDP, GNI and consumption, will increase exerting positive effects on domestic economic growth. Also, it is necessary to proactively respond to GCC member states' industrial diversification policies for FTA-based industrial cooperation to diversify the sources of crude oil and natural gas imports for further resource risk management.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.86-95
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• 2019

Recently, the applications of carbon fiber have been broader than ever when it comes to such industrials as automobiles, ships, aerospace, civil engineering and architecture because of their lightweight-ness and high mechanical properties. This study analyzed mechanical properties and flexural behavior of carbon fiber reinforced cement composites(CFRC) with different fiber contents and fiber lengths, and also impact resistance by natural drop test on mortar specimens was compared and examined. In addition, contents of carbon fiber(CF) were varied by 0.5%, 1.0%, 2.0% and 3.0%. Fiber lengths was used for 6 mm and 12 mm, respectively. As a result of the test, the flow value was very disadvantageous in terms of fluidity due to the carbon fiber ball phenomenon, and the unit weight was slightly reduced. In particular, the compressive strength was decreased with increasing carbon fiber contents. On the other hand, the flexural strength was the highest with 12 mm fiber length and 2% fiber content. As the results of the impact resistance test, the specimens of plain mortar takes about 2~3 times to final fracture, while the specimens of CFRC is somewhat different depending on the increase of the fiber contents. However, when the fiber length is 12 mm and the fiber content is 2%, the impact resistance was the highest.

• Journal of the Korean Society of Radiology
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• v.13 no.1
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• pp.141-146
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• 2019

Radiation sources used in the field of industrial non-destructive pose a risk of exposure due to ageing equipment and operator carelessness. Thus, the need for a safety management system to trace the location of the source is being added. In this study, Monte Carlo Simulation was performed to analyse the angle dependence of the unit-cell comprising the line-array dosimeter for tracking the location of radiation sources. As a result, the margin of error for the top 10% of each slope was 5.90% at $0^{\circ}$, 8.08% at $30^{\circ}$, and 20.90% at $60^{\circ}$. The ratio of the total absorbed dose was 83.77% at $30^{\circ}$ and 53.36% at $60^{\circ}$ based on $0^{\circ}$(100%) and showed a tendency to decrease with increasing slope. For all gradients, the maximum number was shown at $30^{\circ}$ No. 9 pixels, and for No. 10, there was a tendency to drop 7.24 percent. This study has shown a large amount of angle dependence, and it is estimated that the proper distance between the source and line-array dosimeters should be maintained at a distance of not less than 1 cm to reduce them.

• Journal of Industrial Convergence
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• v.19 no.4
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• pp.95-102
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• 2021

This study aims to verify the effect of mother's career-related behavior on the intention of multicultural youths to school dropout intention and the mediating effect of academic adaptation. To this end, 1,121 middle school seniors were sampled in the 7th (2017) data of the Multicultural Youth Panel Survey, and the influence relationship of the model presented as a three-step method of analysis of the mediated effects of Baron & Kenny and the Sobel test were conducted. First, the analysis showed that mother's support, a subfactor of mother's career-related behavior, had a negative effect on dropout intention, and that mother's interference had a positive effect. Second, academi adaptation has been shown to have a negative effect on dropout intention. Third, mother's support, a subfactor of mother's career-related behavior, showed a positive influence on academi adaptation, and mother's interference showed a negative effect. Fourth, academi adaptation has been shown to be mediated in the relationship between career-related behavior and dropout intention. Based on the above results, practical implications were presented.

• Korean Journal of Acupuncture
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• v.38 no.4
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• pp.282-289
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• 2021

Objectives : The purpose of this study is to construct a model of the possible thermal runaway of electronic moxibustion and to implement an appropriate risk management method. Methods : To reproduce the system error situation of the electronic moxibustion circuit equipped with microcontroller unit, temperature sensor and heater, a code was set to disable the signal input to temperature sensor and maintain "high" heating signal to heater. The temperature change of electronic moxibustion was compared between 3 types of heater module; module 1 consisting of a combination of heater+0 ohm+0 ohm resistance, module 2 consisting of a combination of heater+Polymeric Positive Temperature Coefficient (PPTC)+0 ohm resistance, and module 3 consisting of a combination of heater+PPTC+10 ohm resistance. The temperature change was measured using a polydimethylsiloxane (PDMS) silicone phantom. After maintaining surface temperature of the phantom at 31~32℃ for 20 seconds, electronic moxibustion was applied. After operating electronic moxibustion, the temperature change was measured for 660 seconds on the surface and 900 seconds at 2 mm depth. Results : Regardless of the module type, the time-dependent change in temperature showed a rapid rise followed by a gentle curve, and a sharp drop in temperature after reaching the maximum temperature about 10 minutes after the switching the moxibustion on. Temperature measured at the depth of 2 mm below the surface increased slower and to a lesser extent. Module 1 reached highest peak temperature with largest change of temperature at both depths followed by module 2, and 3. Conclusions : Through the combination of PPTC+resistance with the heater of electronic moxibustion, it is possible to limit the rise in temperature even with the software error. Thus, this setting can be used as an independent safety measure for the electronic moxibustion control unit.

• Journal of Korea Entertainment Industry Association
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• v.14 no.3
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• pp.363-373
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• 2020

The purpose of this study was to improve the gait ability and quality of life of stroke patients by combining virtual reality technology and a visual feedback gait training program with entertainment elements. Ten stroke patients with circumduction gait were selected. The visual feedback treadmill gait training program using virtual reality technology and a force plate measurement system was conducted 30 minutes a day, 5 days a week, with 25 sessions in 5 weeks. To investigate the effects of this gait training program, evaluations using the joint range-of-motion test, muscle activity tests, Berg balance scale (BBS), gait analysis, and stroke-specific quality-of-life scale (SS-QOL) were performed before and after intervention. Statistically significant differences were found in the joint range of motion and muscle activity of the affected side from the initial swing phase to the mid-swing phase of the gait cycle, dynamic balance, gait function, and quality of life (p <0.05). The results of this study indicate that the gait training program improved the foot drop, muscle activity, dynamic balance, and gait ability of stroke patients with circumduction gait, thereby improving the quality of life of the patients. Therefore, we recommend the application of the visual feedback treadmill gait training program using virtual reality technology and a force plate measurement system to improve gait ability and quality of life of stroke patients with circumduction gait.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.212-217
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• 2022

Large thermal stress due to the difference between silicon carbide and graphite's coefficients of thermal expansion could be formed during crystal growing process of silicon carbide (SiC) at high temperature. The large thermal stress could separate the SiC seed crystals from graphite components, which bring about the drop of the seed crystal during crystal growth. However, the bonding properties of SiC seed crystal module has hardly reported so far. In this study, SiC and graphite were bonded using 3 types of bonding agents and a three-point bending tests using a mixed-mode flexure test were conducted for the bonded samples to evaluate the bonding characteristics between SiC and graphite. Raman spectroscopy, X-ray Photoelectron Spectroscopy, and X-ray Computed Tomography were used to analyze the bonding characteristics and the microstructures of the SiC-graphite interfaces bonded with the bonding agents. As results, an excellent bonding agent was chosen to fabricate SiC seed crystal module with 50 mm in diameter. An SiC single crystal with 50 mm in diameter was successfully grown without falling out during top seeded solution growth of SiC at high temperature.