• Journal of the Korean Vacuum Society
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• v.18 no.5
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• pp.384-389
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• 2009

ZnO, a wurtzite lattice structure, has attracted much attention as a promising material for light-emitting diodes (LEDs) due to highly efficient UV emission resulting from its large band gap of 3.37 eV, large exciton binding energy of 60 meV, and low power threshold for optical pumping at room temperature. For the realization of LEDs, both n-type ZnO and p-type ZnO are required. Now, n-type ZnO for practical applications is available; however, p-type ZnO still has many drawbacks. In this study, ZnO films were grown on glass substrates by using atomic layer deposition (ALD) and the ZnO films were irradiated by nitrogen ion beams (20 keV, $10^{13}{\sim}10^{15}ions/cm^2$). The effects of nitrogen-beam irradiation on the ZnO structure as well as the electrical property were investigated by using fieldemission scanning electron microscopy (FESEM) and Hall-effect measurement.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.105-105
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• 2011

ZnO is a promising material since it could be applied to many fields such as solar cells, laser diodes, thin films transistors and gas sensors. ZnO has a wide and direct band gap for about 3.37 eV at room temperature and a high exciton binding energy of 60 meV. In particular, ZnO features high sensitivity to toxic and combustible gas such as CO, NOX, so on. The development of gas sensors to monitor the toxic and combustible gases is imperative due to the concerns for enviromental pollution and the safety requirements for the industry. In this study, we investigated the effect of substrate temperature and post-annealing on structural and electrical properties of ZnO thin films. ZnO thin films were deposited by pulsed laser deposition (PLD) at various temperatures at from room temperature to $600^{\circ}C$. After that, post-annealing were performed at $600^{\circ}C$. To inspect the structural properties of the deposited ZnO thin films, X-ray diffraction (XRD) was carried out. For gas sensors, the morphology of the films is dominant factor since it is deeply related with the film surface area. Therefore, the atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM) were used to observe the surface of the ZnO thin films. Furthermore, we analyzed the electrical properties by using a Hall measurement system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2770-2776
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• 2015

The development of efficient wearable antennas is required to implement short range body-centric wireless communication links for various internet of thing applications. We present simulation and measurement results of conductive-fiber-based wearable antennas which can comfortably fabricated directly on usual clothing materials. The proposed antenna is a form of a rectangular patch antenna designed by weaving conductive fibers on a felt substrate. A full-wave electromagnetic simulation tool is used to investigate the antenna performance such as antenna impedance, resonant frequency, and radiation efficiency. Parametric studies show that the radiation efficiency increases from 67.5% to 70.4% by widening the gap between conductive fibers from 0.25mm to 3mm. This implies a wearable antenna with good radiation efficiency can be designed despite of less portion of conductive fibers on the antenna. The simulation results are also verified by measured results with fabricated antennas.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.10
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• pp.5115-5122
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• 2013

This paper has studied about the development and application of landslide collapse prediction real-time monitoring system based on USN to detect and measure the collapse of landslide. The rainfall measuring sensor, gap water pressure sensor, indicator displacement measuring sensor, index inclination sensor, water content sensor and image analysis sensor are selected and these are applied on the test bed. Each sensor's operation and performance for reliability verification is tested by the instrument which is installed in the field. As the result, u-IT based real-time landslide monitoring system which is developed by this research for landslide collapse detection could minimize life and property damages because it makes advance evacuation with collapse risk pre-estimate through real-time monitoring on roadside cut and bedrock slopes. This system is based on the results of this study demonstrate the effect escarpment plan are spread throughout.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.83-92
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• 2005

An electromagnetic acoustic transducer (EMAT) is a unique probe that does not require a couplant or gel and also can usually generate or detect an ultrasonic wave into specimens across a small gap. It, therefore can be applied in a noncontact mode with a high degree of reproducibility. Especially stiffness of composites depends on layup sequence of CFRP(carbon fiber reinforced plastics) laminates. It is very important to evaluate the layup errors in prepreg laminates. A nondestructive technique can therefore serve as a useful measurement for detecting layup errors. This shear wave for detecting the presence of the errors is very sensitive. A decomposition model has been used in the interpretation and prediction of test results. Test results have been com pared with model data. It is found that the high probability shows between tests and the model utilized in characterizing cured layups of the laminates. Also a C-scan method was used for detecting layup of the laminates because of extracting fiber orientation information from the ultrasonic reflection caused by structural imperfections in the laminates. Therefore, it was found that interface C-scan images show the fiber orientation information by using two-dimensional fast Fourier transform (2-D FFT).

• The Journal of the Acoustical Society of Korea
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• v.24 no.4
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• pp.194-201
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• 2005

Since the necessity for the accurate measurement in the field of acoustics, vibration, and ultrasound was internationally increased, CCAUV (Consultative Committee for Acoustics , Ultrasound and Vibration) was created by the CIPM (International Committee for Weights and Measures) in 1998. One of the first activities of CCAUV is the key comparison on 1' standard microphones. The key comparison was done from April. 1999 to April. 2001 and 12 NMIs(National Metrology Institutes) including KRISS (Korea Research Institute of Standards and Science) were participated. The pilot laboratory was the National Physical Laboratory(NPL). The traveling standards were two LSIP(Laboratory Standard 1' Pressure Type) microphones specified in IEC 61094-1 and the calibration frequency ranges covers from 63Hz to 8kHz. In this paper, the analyzed results in the final report were summarized.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.41-48
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• 2013

Emerging three-dimensional television (3DTV) as a new IT product shows a possibility that television is not for just watching broadcasting, but an attractive tool for applying it to our real life. Three dimensional television is generally more effective and attractive than two-dimensional television (2DTV). But it still needs continuous technological improvement to solve its inherent limitations until many customers decide to purchase 3DTVs without hesitation. Innovative products like 3DTV encounter a quality problem leading purchase decision by customers. Quality is regarded as one of the most important factors affecting customers to adopt and use the product. Furthermore, measuring quality effectively is considerable for the 3DTV research. In this paper, we suggest the Analytic Hierarchy Process(AHP) method for evaluating 3DTVs in a view of quality. We describe quality criteria affecting the 3DTV selection through a literature survey and develope an analytical method for measuring quality. We classify the quality of 3DTV into four types and suggest a concept of the quality ratio as a measurement criteria instead of the quality gap. Though a numerical example, we show how priorities of 3DTV with versatile manufacturers is computed.

• Nuclear Engineering and Technology
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• v.48 no.4
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• pp.847-858
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• 2016

An overview is given on the work of the Laboratory of Nuclear Energy Systems at ETH, Zurich (ETHZ) and of the Laboratory of Thermal Hydraulics at Paul Scherrer Institute (PSI), Switzerland on tight-lattice bundles. Two-phase flow in subchannels of a tight triangular lattice was studied experimentally and by computational fluid dynamics simulations. Two adiabatic facilities were used: (1) a vertical channel modeling a pair of neighboring sub-channels; and (2) an arrangement of four subchannels with one subchannel in the center. The first geometry was equipped with two electrical film sensors placed on opposing rod surfaces forming the subchannel gap. They recorded 2D liquid film thickness distributions on a domain of $16{\times}64$ measuring points each, with a time resolution of 10 kHz. In the bubbly and slug flow regime, information on the bubble size, shape, and velocity and the residual liquid film thickness underneath the bubbles were obtained. The second channel was investigated using cold neutron tomography, which allowed the measurement of average liquid film profiles showing the effect of spacer grids with vanes. The results were reproduced by large eddy simulation + volume of fluid. In the outlook, a novel nonadiabatic subchannel experiment is introduced that can be driven to steady-state dryout. A refrigerant is heated by a heavy water circuit, which allows the application of cold neutron tomography.

• The Journal of Fisheries Business Administration
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• v.33 no.2
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• pp.1-29
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• 2002

The main objective of this research aims at analyzing efficiency of government financial transfers(GFTs) to the Korean fisheries sector, using the Linear Structural Relations model(i.e., LISERL model) and the field survey data. Most policies of GFTs tend to be implemented to protect industries with weak competitive advantages such as infant and/or primary industries. Specific policy instruments include income transfers, government loans with lower interest rates, taxes and the like. Fishing activities are made at a highly changeable natural environment of the ocean with a great amount of risk and uncertainty. Fishing households make their livelihood under the small-scale fisheries. Such fisheries and fishing households have also a relatively weak market power. Because of these fisheries characteristics most coastal states have adopted a variety of government support programs. However, despite such a huge government support, during the past several decades the world fishing communities have seen a tendency of continuous fishereis resource overexploitation. For this resason there have been hot debates over the government support policies for fisheries through OECD, FAO, WTO, and UNEP. In general, policy evaluations tend to be made on the basis of benefit-cost(B/C) analysis. However, the B/C analysis may produce results quite different from real ones primarily due to many unmeasurable effects. Thus, the authors composed simple questionaires and let fishermen, government officials and academic people answer the questions. The survery was made in several ways such as post-mail and personal/group interviews. In recent years, for analysis of policy performances and effectiveness, the LISREL model has often been used, which consists of structural and measurement eqquations. This model has a good advantage of transforming unobservable variables to observable ones so that it helps construct endogenous cause and effect relationships among relevant variables. The evaluation was done from the two aspects: policy results and policy effectiveness. The policy result evaluation showed that there is a need for improvement for policy problem perception and decision-making process, while the policy effect evaluation suggested that the policy goals were successfully achieved and social justice was improved from the perspective of the entire society as well. However, the research results showed that the GFT policies rendered little contrubtion to narrowing down the gap between GFT beneficiaries and non-beneficiaries incomes.

• Physical Therapy Korea
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• v.21 no.4
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• pp.56-66
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• 2014

For maintaining adequate psychometric properties when reducing the number of items from an instrument, item level psychometrics is crucial. Strategies such as low item correlation or factor loadings, using classical test theory, have traditionally been advocated. The purpose of this study is to describe the development of a new short form assessing the impact of low back pain on physical activity. Rasch measurement model has been applied to the International Classification of Functioning, Disability and Health Activity Measure (ICF-AM). One hundred and one individuals with low back pain aged 19-89 years (mean age: $48.1{\pm}17.3$) who live in the community were participated in the study. Twenty-seven items of lifting/carrying construct of the ICF-AM were analyzed. Ten items were selected from the construct to create a short form. Item elimination criteria include: 1) high or low mean square (out of the range: .6-1.4 for the fit statistics), 2) similar item calibrations to adjacent items, 3) person separation value, and item-person map for potential gap in person ability continuum. All 10 items of the short form fit to the Rasch model except one item (i.e., carrying toddler on back). Despite its high infit and outfit statistics (1.90/2.17), the item had to be reinstated due to potential gaps at the upper extreme of person ability level. The short form had a slightly better spread of person ability continuum compared to the entire set of item. The created short form separated individuals with low back pain into nearly 4 groups, while the entire set of items separated the individuals into 6 groups. The findings prompted multidimensional models for better explanation of the lifting/carrying domain. The item level psychometrics based on the Rasch model can be useful in developing short forms with rationally retained items.