• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.4
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• pp.229-234
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• 2017

In this study, we fabricated a TFT gas sensor with ZnO nanorods grown by hydrothermal synthesis. The suggested devices were compared with the conventional ZnO film-type TFTs in terms of the gas-response properties and the electrical transfer characteristics. The ZnO seed layer is formed by atomic-layer deposition (ALD), and the precursors for the nanorods are zinc nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) and hexamethylenetetramine ($(CH_2)6N_4$). When 15 ppm of NO gas was supplied in a gas chamber at $150^{\circ}C$ to analyze the sensing capability of the suggested devices, the sensitivity (S) was 4.5, showing that the nanorod-type devices respond sensitively to the external environment. These results can be explained by X-ray photoelectron spectroscopy (XPS) analysis, which showed that the oxygen deficiency of ZnO nanorods is higher than that of ZnO film, and confirms that the ZnO nanorod-type TFTs are advantageous for the fabrication of high-performance gas sensors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.7
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• pp.521-526
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• 2018

In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. In this study, we fabricated a $NO_X$ gas sensor by using a multi-walled carbon nanotube (MWCNT)/zinc oxide (ZnO) composite film. The fabricated MWCNT/ZnO gas sensor was then treated by a $450^{\circ}C$ temperature process to increase its detection sensitivity for NOx gas. We compared the detection characteristics of a ZnO film gas sensor, MWCNT film gas sensor, and the MWCNT/ZnO composited film gas sensor with and without the heat-treatment process. The fabricated gas sensors were used to detect $NO_X$ gas at different concentrations. The gas sensor absorbed $NO_X$ gas molecules, exhibiting increased sensitivity. The sensitivity of the gas sensor was increased by increasing the gas concentration. Additionally, while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained its sensitivity for detecting $NO_X$ gas. Compared with ZnO, the MWCNT film gas sensor is excellent for detecting $NO_X$ gas. From the experimental results, we confirmed the enhanced gas sensor sensing mechanism. The increased effect by electronic interaction between the MWCNT and ZnO films contributes to the improved sensor performance.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.918-927
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• 2018

Based on the actual operating environment of transformer, the aging tests of nitrile butadiene rubber (NBR) were conducted systematically under four conditions: in air, in transform oil, under compression in air and under compression in transform oil to studythe effect of high temperature, transform oil and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber and predict the lifetime. The effects of liquid media and compression stress simultaneously on the thermal aging behaviors of nitrile butadiene rubber were studied by using characterization methods such as IR spectrosc-opy, thermogravimetric measurements, Differential Scanning Calorimetry (DSC) measurements and mechanical property measurements. The changes in physical properties during the aging process were analyzed and compared. Different aging conditions yielded materials with different properties. Aging at $70^{\circ}C$ under compression stress in oil, the change in elongation at break was lower than that aging in oil, but larger than that aging under compression in air. The compression set or elongation at break as evaluation indexes, 50% as critical value, the lifetime of NBR at $25^{\circ}C$ was predicted and compared. When aging under compression in oil, the prediction lifetime was lower than in air and under compression in air, and in oil. It was clear that when predicting the service lifetime of NBR in oil sealing application, compression and media liquid should be involved simultaneously. Under compression in oil, compression set as the evaluation index, the prediction lifetime of NBR was shorter than that of elongation at break as the evaluation index. For the life prediction of NBR, we should take into account of the performance trends of NBR under actual operating conditions to select the appropriate evaluation index.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.1
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• pp.117-124
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• 2018

Junctionless amorphous InGaZnO thin film transistors with different film thickness have been fabricated. Their device performance parameters were extracted and gate oxide breakdown voltages were analyzed with different film thickness. The device performances were enhanced with increase of film thickness but the gate oxide breakdown voltages were decreased. The device performances were enhanced with increase of temperatures but the gate oxide breakdown voltages were decreased due to the increased drain current. The drain current under illumination was increased due to photo-excited electron-hole pair generation but the gate oxide breakdown voltages were decreased. The reason for decreased breakdown voltage with increase of film thickness, operation temperature and light intensity was due to the increased number of channel electrons and more injection into the gate oxide layer. One should decide the gate oxide thickness with considering the film thickness and operating temperature when one decides to replace the junctionless amorphous InGaZnO thin film transistors as BEOL transistors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.3
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• pp.189-194
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• 2014

In this paper, PV modules using a low-temperature conductive film(LT-CF) as a bonding material between a cell and a solder free ribbon were produced and chracterized, which is more environmental-friendly, cost effective and high efficient. Mainly, filed electrical performance of PV modules using three different types of bonding material; a convetional solder ribbon(SR), a LT-CF and a light-capturing Ribbon(LCR) were compared to comfirm the feasibility of LT-CF as a bonding material. The filed test were conducted for 3 months and results were discussed in terms of amount of output energy production and efficiency.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.121-122
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• 2006

Recently, poly-Si TFT-LCD starts to be mass produced using excimer laser annealing (ELA) poly-Si. The main reason for this is the good quality poly-Si and large area uniformity. We report the influence of channel length and width on poly-Si TITs performance. Transfer characteristics of n-channel poly-Si thin film transistors fabricated on polycrystalline silicon (poly-Si) thin film transistors (TFTs) with various channel lengths and widths of $2-30{\mu}m$ has been investigated. In this paper, we analyzed the data of n-type TFTs. We studied threshold voltage ($V_{TH}$), on/off current ratio ($I_{ON}/I_{OFF}$), saturation current (I_{DSAT}$), and transconductance ($g_m$) of n-channel poly-Si thin film transistors with various channel lengths and widths.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.32-38
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• 2017

Plasticizers play roles in increasing plasticity or fluidity during mixing. Representative plasticizers are DOS, DOA, IDP and BTTN. In particular, BTTN is an energy plasticizer that helps propellant performance and is widely used. However these compounds are sensitive relatively. So, in order to develop insensitive energetic plasticizer, synthesis of one of the derivatives of triazole, 4,5-bis (azido methyl)-(1-butyl)-1,2,3-triazole (1-DABTR), was studied. Also, the compound was characterized by NMR, IR spectroscopy, and physicochemical properties such as glass transition temperature, melting point, decomposition temperature, density, viscosity and impact sensitivity were measured. In addition, the heats of formation (${\Delta}H_f$) of 1-DABTR was also calculated using Gaussian 09.

• Computers and Concrete
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• v.15 no.1
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• pp.103-126
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• 2015

Thermal effects are significant loads for assessing concrete dam behaviour during operation. A new methodology to estimate thermal loads on concrete dams taking into account processes which were previously unconsidered, such as: the evaporative cooling, the night radiating cooling or the shades, has been recently reported. The application of this novel approach in combination with a three-dimensional finite element method to solve the heat diffusion equation led to a precise characterization of the thermal field inside the dam. However, that approach may be computationally expensive. This paper proposes the use of a new one-dimensional model based on an explicit finite difference scheme which is improved by means of the reported methodology for computing the heat fluxes through the dam faces. The improved model has been applied to a case study where observations from 21 concrete thermometers and data of climatic variables were available. The results are compared with those from: (a) the original one-dimensional finite difference model, (b) the Stucky-Derron classical one-dimensional analytical solution, and (c) a three-dimensional finite element method. The results of the improved model match well with the observed temperatures, in addition they are similar to those obtained with (c) except in the vicinity of the abutments, although this later is a considerably more complex methodology. The improved model have a better performance than the models (a) and (b), whose results present larger error and bias when compared with the recorded data.

• Geomechanics and Engineering
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• v.10 no.6
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• pp.757-774
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• 2016

Soils are usually weak in tension therefore different materials such as geosynthetics are used to address this inadequacy. Worldwide annual consumption of geosynthetics is close to $1000million\;m^2$, and the value of these materials is probably close to US$1500 million. Since the total cost of the construction is at least four or five times the cost of the geosynthetic itself, the impact of these materials on civil engineering construction is very large indeed. Nevertheless, there are several significant problems associated with geosynthetics, such as creep, low modulus of elasticity, and susceptibility to aggressive environment. Carbon fiber reinforced polymer (CFRP) was introduced over two decades ago in the field of structural engineering that can also be used in geotechnical engineering. CFRP has all the benefits associated with geosynthetics and it boasts higher strength, higher modulus, no significant creep and reliability in aggressive environments. In this paper, the performance of a CFRP reinforced retaining wall is investigated using the finite element method. Since the characterization of behavior of soils and interfaces are vital for reliable prediction from the numerical model, soil and interface properties are obtained from comprehensive laboratory tests. Based on the laboratory results for CFRP, backfill soil, and interface data, the finite element model is used to study the behavior of a CFRP reinforced wall. The finite element model was verified based on the results of filed measurements for a reference wall. Then the reference wall simulated by CFRP reinforcements and the results. The results of this investigations showed that the safety factor of CFRP reinforced wall is more and its deformations is less than those for a retaining wall reinforced with ordinary geosynthetics while their construction costs are in similar range.

• Food Science and Preservation
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• v.10 no.4
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• pp.574-583
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• 2003

There have been a lot of research efforts on development of active food packaging structures and materials in the form of plastic films and containers, along with investigating novel polymers and bioactive compounds for packaging purpose, in order to improve storage stability and safety of foods during distribution and sale. Recently, great interests focus on antimicrobial package films, as an active packaging system, made from synthetic plastic polymer% and natural biopolymers containing various antimicrobial substances for food packaging applications. In this active system, substances are slowly released onto the food surface. However, antimicrobial activity as well as physical properties of the films can be significantly influenced by several factors such as polymer matrix, antimicrobial compounds, and interactions between polymers and compounds. Thus, this study reviews present status of antimicrobial food packaging films in overall performance aspects including types of polymers and active substances, test for antimicrobial activity, and changes in mechanical and antimicrobial properties by preparation method.