• Ocean and Polar Research
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• v.23 no.3
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• pp.279-284
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• 2001

The natural high productivity of temperate coastal waters in Korea can be used in advantage to reduce the feed costs for the cage-cultured marine carnivorous fish species. By using the night-lights methods an alternative of supplementary feeding strategy can be offered to the cage farmers and maintain sound environmental conditions that could enhance maximum sustainable yields. The aim of this study was to investigate the effects of night-lights which shown positive results on feeding and growth in sea cage cultured rockfish, Sebastes schlegeli. The study showed that for the water around overhead illuminated sea cage, higher zooplankton density was observed at night than during the daytime. Increased amounts of for-age, evidenced by stomach content analyses were observed in the early evening, but decreased amounts were observed in the morning and afternoon. That is, feeding activities of the fish were most intensive from midnight to dawn. In a three month feeding experiment, the results showed that night-lighted groups were superior to groups with the highest feeding efficient. This study suggested that the evidence that night-lights superimposed on only day-lights enhance growth of rockfish in sea cages during summer and winter, with timing of exposure affecting growth of juvenile fish. The capability to control the feeding behavior of marine life via manipulation and external stimuli could considerably benefit the advancement of sea cage aquaculture in coastal areas.

• Laser Solutions
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• v.2 no.3
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• pp.11-18
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• 1999

This paper describes the weldability of carbon steel and stainless steel using 5㎾ $CO_2$ laser system with nearly multi-mode beam and a parabolic focusing mirror. In the laser welding of steels, major welding parameters are focal point, travel speed, beam power, shield gas and gap tolerance, etc.. Two kinds of gases(Ar, He) were used as a assist gas and supplied through the external nozzle. It is very important for optimum condition to remove plasma plume which absorbs laser beam and to obtain deep penetration and sound weld bead. Bead-on-plate welding tests were carried out for the experiments. Penetration data were obtained with various welding parameters and the effects of welding parameters were discussed. Butt welding tests were performed with various conditions. Only the optimum laser parameters assured good weld quality As a result of this study, We achieve the fundamental weldabilities using a high power $CO_2$ laser for carbon steel and stainless steel.

• Journal of Soil and Groundwater Environment
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• v.20 no.3
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• pp.51-64
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• 2015

In the present study, we develop two history matching techniques based on Markov chain Monte Carlo method where radial basis function and Gaussian distribution generated by unconditional geostatistical simulation are employed as the random walk transition kernels. The Bayesian inverse methods for aquifer characterization as the developed models can be effectively applied to the condition even when the targeted information such as hydraulic conductivity is absent and there are transient hydraulic head records due to imposed stress at observation wells. The model which uses unconditional simulation as random walk transition kernel has advantage in that spatial statistics can be directly associated with the predictions. The model using radial basis function network shares the same advantages as the model with unconditional simulation, yet the radial basis function network based the model does not require external geostatistical techniques. Also, by employing radial basis function as transition kernel, multi-scale nested structures can be rigorously addressed. In the validations of the developed models, the overall predictabilities of both models are sound by showing high correlation coefficient between the reference and the predicted. In terms of the model performance, the model with radial basis function network has higher error reduction rate and computational efficiency than with unconditional geostatistical simulation.

• Journal of Welding and Joining
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• v.9 no.4
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• pp.60-68
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• 1991

The weld quality of end cap welds in Pressurized Heavy Water Reactor (PHWR) Fuel is extremely important for the fuel performance in the nuclear reactor. The quality of resistance upset welds is currently evaluated mainly by the metallographic examination although it reveals only two weld cross-sections in a circumference welds. This investigation was, firstly, carried out to determine whether the ultrasonic examination would be applied to detect weld defects in the end cap welds and, secondly, to measure the mechanical strength of upset butt welds as a function of phase shift percentage. The major results obtained in this study are as follows: 1. The weld current and amount of upset shrinkage linearly increased with increasing the phase shift percentage. 2. Above the phase shift 55%, the defects in the welds were completely eliminated with increasing the phase of sound weld was over the thickness of cladding tube. 3. The ultrasonic testing well detected such defects in the end cap welds as upset external crack, upset split, corner crack and irregular weld flash comparing with the results of metallography. 4. The micro-fissure in the corner of the end cap welds was reliably detected by ultrasonic testing. 5. The mechanical strength in the welds increased with increasing phase shift percentage but the fracture did't occur in the welds above 55%.

• Journal of Welding and Joining
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• v.23 no.4
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• pp.73-80
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• 2005

Arc blow being occurred by Electro-Magnetic force(EMF) during the electric arc welding prevents the formation of a sound weldment. In this study, the effects of arc position, groove size, tack weld and base plate on the EMF in a butt-joint welding of mild steel plate are analyzed by a computer simulation based on the finite element method. The EMF can be numerically identified to be caused by a difference of the magnetic flux-density between ahead of and behind the arc in case that the workpiece locates asymmetrically around the uc. When there exists an air gap of groove ahead of the arc in the welding direction, the similar magnetic force has been producted regardless of the arc position and the gap size. The tack weld alleviates the magnetic force to about one fourth at the finish end of the workpiece. The magnetic force can be also significantly reduced with the base plate to about one fifth at the start end of the workpiece containing a tack weld.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.1
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• pp.25-32
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• 2010

The paper proposes a hierarchical fault detection method for the high voltage equipment using a microphone array which detects the location of fault and the thermal imaging and CCD cameras which verifies the fault and stores the image, respectively. There are partial arc discharges on the faulty insulators, which generates a specific pattern of sound. Detecting the signal using the microphone array, the location of the faulty insulator can be estimated. The 6th band-pass filter was applied to remove noise signal from wind or external influence. When the mobile robot carries the thermal and CCD cameras to the possible place of the fault insulator, the fault insulators or power transmission wires can be detected by the thermal images, which are caused by the aging or natural erosion. Finally, the CCD camera captures the image of the fault insulator for the record. The detection scheme of fault location using the microphone array and the thermal images have been proved to be effective through the real experiments. As a result of this research, it becomes possible to use a mobile robot with the integrated sensors to detect the fault insulators instead of a human being.

• Journal of Korean Association for Spatial Structures
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• v.16 no.2
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• pp.39-45
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• 2016

Membrane structure is a system that is stabilized by maintaining a tensile state of the membrane material that originally cannot resist the bending or pressure. Also, it is a system that allows the whole membrane structure to bear external loads caused by wind or precipitation such as snow, rain and etc. Tension relaxation phenomenon can transpire to the tension that is introduced to the fabric over time, due to the innate characteristics of the membrane material. Thus, it is important to accurately understand the size of the membrane tension after the completion of the structures, for maintenance and management purposes. The authors have proposed the principle of theoretically and indirectly measuring the tension by vibrating the membrane surface with sound waves exposures against the surface, which is compartmentalized by a rectangular boundary, and by measuring the natural frequency of the membrane surface that selectively resonates. The authors of this paper measured the tension of preexisting membrane structure for its maintenance by using the developed portable measurement equipment. Through analyzing the measurement data, the authors review the points that should be improved and the technical method for the new maintenance system of membrane tension.

• The Korean Society of Law and Medicine
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• v.13 no.1
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• pp.41-69
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• 2012

First introduced in 1977, Korean health care system reached to national coverage in short period of time never seen before in any other countries, and rated as successful system protecting the health of the public at relatively low price. However, despite those positive evaluations, some of fraudulent medical organizations or pharmacies are hindering the sound development of the national health care system with meticulous false billing exaggerating the number of patients or the days of their treatment. To prevent aforementioned nursing home fraud and false billing, the misconduct should be punished as subject to the criminal law and severally punished for fines and payments which far exceed the expected amount of illicit gains as it is basically violation of criminal fraud, other than the forced return of illicit gains based on civil laws. Furthermore, the Health Insurance Review and Assessment Service should strengthen and complement the fraud investigators, the review process, and the professional training to raise the detection rates. It might also want to review ways to implement whistleblower rewarding system and rewards for evidences of healthcare fraud to overcome the limits of external review.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.7
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• pp.323-331
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• 2021

This paper examines the relationship between ownership structure and level cash holdings in an emerging country, namely, Saudi Arabia, by constructing a corporate governance mechanism (foreign ownership, family ownership, institutional and managerial ownership). This paper uses data from 100 listed firms at Saudi Stock Exchange (TADAWUL) from 2011 to 2019. The firm's decision to hold cash has come to the fore in the last two or three years as a result of the recent global financial crisis, and the impact that this has had on the firms' ability to raise funds from external sources. Using the random-effect generalized least square (GLS) regression model, the findings reveal that foreign and family ownership negatively influences cash holdings, while managerial ownership has a positive association with cash holdings. Further, institutional ownership did not have a direct effect on cash holdings in Saudi Arabia. Our results suggest that ownership structure include foreign ownership, family and managerial ownership is an essential vehicle to promote the performance of cash holding of all the 100 public-listed non-financial firms in Saudi Arabia. We recommend that sound policies should be targeted toward foreign ownership, family, and managerial ownership since they are essential to improve cash holding in Saudi Arabian firms.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.7
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• pp.433-446
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• 2021

This study aims to identify the elasticities and casualties of financial performance and determinants of the mining and extractive companies listed in Jordan's stock market over the 2005-2018 period. The conceptual framework is based on the Resource-Based View theory and Arbitrage Pricing theory is used to describe the relationship between the external environment and the financial performance of the companies. Profitability ratio (return on assets) is utilized as a proxy of financial performance measurement. Meantime, the company's characteristics, macroeconomic variables, and non-economic factors are utilized as independent factors. Data sources are panel data set for mining and extractive companies over the above period. Fully Modified Ordinary Least Square (FMOLS), Dynamic Ordinary Least Squares (DOLS), and Pooled Mean Group (PMG) methods are applied. The empirical findings indicated that company size, sales growth, financial leverage, liquidity, and GDP growth were the critical determinants of mining and extractive companies' financial performance in the Amman Stock Exchange. Thus, the findings conclude that company characteristics and GDP growth mainly drive financial performance. Moreover, the findings reveal that a bidirectional causal elasticity exists between GDP and financial leverage and return on assets (ROA). Sound financial performance can be obtained by paying more attention to GDP growth and firms' characteristics.