• Journal of the Korean Ceramic Society
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• v.48 no.4
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• pp.328-333
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• 2011

The influence of Al-doped ZnO (AZO) thin films degraded under high temperature and damp heat on the performance deterioration of Cu(In,Ga)$Se_2$ (CIGS) solar cells was investigated. CIGS solar cells with AZO/CdS/CIGS/Mo structure were prepared on glass substrate and exposed to high temperature ($85^{\circ}C$) and damp heat ($85^{\circ}C$/85% RH) for 1000 h. As-prepared CIGS solar cells had 64.91% in fill factor (FF) and 12.04% in conversion efficiency. After exposed to high temperature, CIGS solar cell had 59.14% in FF and 9.78% in efficiency, while after exposed to damp heat, it had 54.00% in FF and 8.78% in efficiency. AZO thin films in the deteriorated CIGS solar cells showed increases in resistivity up to 3.1 times and 4.4 times compared to their initial resistivity after 1000 h of high temperature and damp heat exposure, respectively. These results can be explained by the decreases in carrier concentration and mobility due to diffusion or adsorption of oxygen and moisture in AZO thin films. It can be inferred that decreases in FF and conversion efficiency were caused by an increase in series resistance, which resulted from an increase in resistivity of AZO thin films degraded under high temperature and damp heat.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.30 no.1
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• pp.58-66
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• 2020

Objectives: The objective of this study was to develop formaldehyde samples for quality control (QC) and to test the applicability of proficiency analytical testing in Korea. Methods: We made formaldehyde samples with certified standard solutions (formaldehyde in water or acetonitrile) and 2,4-dinitrophenylhydrazine (2,4-DNPH)-coated silicagel tubes. Four levels of formaldehyde concentration were tested for storage stability at room temperature and at 4℃ over three months. Analytical proficiency testing was performed with four or 36 institutes. Results: Formaldehyde sample tubes were easily made through the injection of standard solutions and the average efficiencies of recovery were 95-101%. The coefficients of variation (CV) of the formaldehyde samples were 1.39-2.55%. The recovery efficiencies fell between 90% and 110% at the concentration range of 1-10 ㎍/sample over three months storage at refrigerated and room temperature. The CVs were less than 5% in the proficiency analytical testing. By adjusted proficient ranges, 64% of the results of the second proficiency analytical testing were acceptable. Conclusions: The formaldehyde samples made by injection on 2,4-DNPH-coated silicagel tubes were stable and applicable for quality control.

• Journal of the Korean Solar Energy Society
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• v.32 no.3
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• pp.11-18
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• 2012

To expect accurately the maximum power of solar cell module under various installation conditions, it is required to know the performance characteristics like temperature dependence. Today, the PV (photovoltaic) market in Korea has been growing. Also BIPV (building integrated photovoltaic) systems are diversified and become popular. But thermal dependence of PV module is little known to customers and system installers. In IEC 61215,a regulation for testing the crystalline silicon solar cell module, the testing method is specified for modules. However there is limitation for testing the module with diverse application examples. In extreme installation method, there is no air flow between rear side of module and ambient, and it can induce temperature increase. In this paper, we studied the roof type installation of PV module on the surface of one-axis tracker system. We measured temperature on every component of PV module and compared to open-rack structure. As a result, we provide the foundation that explains temperature characteristics and NOCT (nominal operation cell temperature) difference. The detail description will be specified as the following paper.

• Journal of Applied Reliability
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• v.14 no.2
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• pp.93-96
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• 2014

RFID (Radio Frequency IDentification) system is recognition technology which can maintain various object's information. Reliability of RFID tags is the most important factor in RFID system. In this paper, we proposed ALT (Accelerated Life Test) method for UHF RFID tags. Temperature and humidity were adopted as stress factors and the accelerated life tests were conducted in three different conditions. We performed failure analysis for identifying failure mechanism and statistical analysis of test data. In the statistical analysis, we employed Inverse Power law for relationship between tag's life and stress. Through the statistical analysis, we proposed acceleration factor for several levels of temperature-humidity. The reliability qualification test plans were also designed for the tag's target reliability.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1319-1327
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• 2001

The results of stand and field testing of a combustion chamber for a heavy-duty 150 MW gas turbine are discussed. The model represented one of 14 identical segments of a tubular multican combustor constructed 1:1 scale. The model experiments were executed at a lower pressure than that in a real gas turbine. Combustion efficiency, pressure loss factor, pattern factor, liner wall temperature, flame radiation, fluctuating pressure and NOx emission were measured at partial and full loads for both model and on-site testing. The comparison of these items in the stand and field test results led to has the development of a method of calculation and the improvement of gas turbine combustors.

• Journal of Applied Reliability
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• v.17 no.2
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• pp.136-142
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• 2017

Purpose: In this paper, we propose a test method for evaluating the life time of the inverter which is one of the main internal configuration systems in order to evaluate the life time of the power supply for the vehicle. Methods: The performance and failure criteria required for the development of the accelerated life test method were established and the Taguchi method was used to derive the stress factors affecting performance and reliability. Results: The major stress of the product degradation were considered to be high temperature. Conclusion: The acceleration factor was estimated through a two-level high temperature test and a test methods was designed to guarantee the accelerated life time of the inverter.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.1
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• pp.14-20
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• 2003

Piezoelectric ultrasonic transducers for high temperature contact measurement were developed. These high temperature ultrasonic transducers (HTUT) consisted of bismuth titanate piezoceramic element whose Curie temperature is higher than $600^{\circ}C$, a backing material of the mixture of tungsten powder and inorganic binder, an inner alumina tube, a wear Plate and a housing. The operational frequencies or the HTUT were 1.04 and 2.08 MHz, respectively. Various commercially available couplants for high temperature were evaluated and compared. As a couplant for high temperature ultrasonic testing between HTUT and test specimen, gold epoxy was selected. The peak amplitude of pulse-echo signals from steel test specimen decreased with increasing temperature. The operational temperature of the HTUT reached up to $500^{\circ}C$ at which the continuous contact measurement was possible.

• Journal of Applied Reliability
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• v.16 no.3
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• pp.202-207
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• 2016

Purpose: The purpose of this study is main factors (environmental conditions, pattern spacing, pattern material) that effect the ion-migration of PCB. Methods: Recently, the electronic components are becoming more high density of electronic device, so that electronic circuits have smaller pitches between the patten and more vulnerable to insulation failure. so the reliability of electric insulation of device has become an ever important issue as device contact pitches of pattern. Usually, ion-migration occurs in high temperature and high humidity environment as voltage is applied to the circuit. Under high temperature and high humidity, voltage applied electronic components respond to applied voltages by metals's electrochemical ionization and a conducting filament forms between the anode and cathode across a nonmetallic medium. This leads to short-circuit failure of the electronic component. Results: we studied ion-migration that occurs in accordance with the main factors (environmental conditions, pitches, pattern material). The PCB pattern material was made by two different types of material (free solder, OSP) for this research and pitches of pattern is 0.15mm, 0.3mm, 0.5mm. PCB was experimented in the environmental conditions (high temperature $120^{\circ}C$, high temperature and high humidity $85^{\circ}C$, 85%RH) and was analyzed for ion-migration through the experiment results. Conclusion: We confirmed that environmental condition, pitches of pattern, pattern material had effect on ion-migration of PCB.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.8 no.1
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• pp.1-10
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• 2002

The actual specific migration data for antioxidants and di-ethylhexyl adipate from plastic food packaging materials being used for fatty food and at high temperature into various food simulants were obtained and compared in accordance with the testing methods and conditions in EU, USA and Korea or Japan. In the case of food packaging material for high temperature use, especially in a thick film such as polypropylene in $450{\mu}m$ thickness, a significant difference in the migration value for antioxidants was observed depending on the migration testing condition and simulants used as defined in the each country areas. Considering the reduction factor of 2 to 5 as being currently applied in EU and USA regulations, the migration values obtained by testing methods of Korea or Japan can exhibit actually higher than those of EU and USA. The migration testing conditions are required to be specified diversely according to the actual exposure temperature of packaging materials.

• Journal of Powder Materials
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• v.10 no.5
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• pp.325-332
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• 2003

The effect of extrusion temperature on the microstructure and mechanical properties was studied in gas atomized TEX>$Al_{81}Si_{19}$ alloy powders and their extruded bars using SEM, tensile testing and wear testing. The Si particle size of He-gas atomized powder was about 200-800 nm. Each microstructure of the extruded bars with extrusion temperature (400, 450 and 50$0^{\circ}C$) showed a homogeneous distribution of primary Si and eutectic Si particles embedded in the Al matrix and the particle size varied from 0.1 to 5.5 ${\mu}m$. With increasing extrusion temperature from 40$0^{\circ}C$ to 50$0^{\circ}C$, the ultimate tensile strength (UTS) decreased from 282 to 236 ㎫ at 300 K and the specific wear increased at all sliding speeds due to the coarse microstructure. The fracture behavior of failure in tension testing and wear testing was also studied. The UTS of extrudate at 40$0^{\circ}C$ higher than that of 50$0^{\circ}C$ because more fine Si particles in Al matrix of extrudate at 40$0^{\circ}C$ prevented crack to propagate.