• Radiation Oncology Journal
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• v.19 no.1
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• pp.74-80
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• 2001

Purpose : Irradiation cones by using backscatter electrons are made for the treatment of superficial small lesions of skin, oral cavity, and rectum where a significant dose gradient and maximum surface dose is desired. Methods and Materials : Backscatter electrons are produced from the primary electron beams from the linear accelerators. The design consists of a cylindrical cone that has a thick circular plate of high atomic number medium (Pb or Cu) attached to the distal end, and the plate can be adjusted the reflected angle. Primary electrons strike the metal plate perpendicularly and produce backscatter electrons that reflect through the lateral hole for treatment. Using film and a parallel plate ion chamber, backscatter electron dose characteristics are measured. Results : The depth dose characteristic of the backscatter electron is very similar to that of the hard x-ray beam that is commonly used for the intracavitary and superficial lesions. The basckscatter electron energy is nearly constant and effectively about 1.5 MeV from the clinical megavoltage beams. The backscatter electron dose rate of $35\~85\;cGy/min$ could be achieved from modern accelerators without any modification. and the depth in water of $50\%$ depth dose from backscatter electron located at 6mm for $45^{\circ}$ angled lead scatter. The beam flatness is dependent on the slit size and the depth of treatment, but is satisfactory to treat small lesions. Conclusions : The measured data for backscatter electron energy, depth dose flatness dose rate and absolute dose indicates that the backscatter electrons are suitable for clinical use.

• Journal of the Korea Concrete Institute
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• v.20 no.1
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• pp.117-125
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• 2008

In the domestic construction industry field nowadays, the usage of deck plates is currently increasing due to the lack of construction workers and the rised in construction cost. However, using deck plates manufactured by thin zinc galvanization in underground structures is criticised because it can lead to increase in maintenance cost caused by rust generation and water leakage. As a solution for this particular problem, deck plates created by Lath and Mortar instead of zinc galvanized steel sheets were developed. This paper deals with the experimental study on flexural behavior of deck plate using metal lath and mortar. Seventeen fullscale specimens were constructed and tested with different type of truss, the diameter of the top and bottom bar, and the thickness of slab. Tests results show that LAMO deck displayed equal performance such as zinc galvanized steel sheets.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.237.1-237.1
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• 2010

Recent developments such as concern over global warming, depletion of fossil fuels and increase in energy demands by the increasing world population has eventually lead to mass production of electricity using renewable sources. Ocean contains energy in form of thermal energy and mechanical energy: thermal energy from solar radiation and mechanical energy from the waves and tides. The current paper looks at generating power using waves. The primary objective of the present study is to maximize the primary energy conversion (first stage conversion) of the base model by making some design changes. The model entire consisted of a numerical wave tank and the turbine section. The turbine section had three components; front guide nozzle, augmentation channel and the rear chamber. The augmentation channel further consisted of a front nozzle, rear nozzle and an internal fluid region representing the turbine housing. Different front guide nozzle configuration and rear chamber design were studied. As mentioned, a numerical wave tank was utilized to generate waves of desired properties and later the turbine section was integrated. The waves in the numerical wave tank were generated by a piston type wave maker which was located at the wave tank inlet. The inlet which was modeled as a plate wall which moved sinusoidally with the general function, $x=asin{\omega}t$. In addition to primary energy conversion, observation of flow characteristics, pressure and the velocity in the augmentation channel, rear chamber as well as the front guide nozzle are presented in the paper. The analysis was performed using the commercial code of the ANSYS-CFX. The base model recorded water power of 29.9 W. After making the changes, the best model obtained water power of 37.1 W which represents an increase of approximately 24% in water power and primary energy conversion.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.322-327
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• 2012

Parallel-plate-type scanning sensors have been commercially used for X-ray imaging sensors. In this study, we manufactured the scan typed 1D X-ray image sensor that can be used to obtain scanning images, by using the plasma display panel (PDP) fabrication process. We fabricated drift and pixel electrodes in the glass chamber and injected Xe gas at atmospheric pressure. We evaluated the intensity of a pixel signal depending on the bias voltage on the drift electrode and investigated the characteristics of shielding effect on the single pixel using lead (Pb). The adsorption rate of X-ray photon is low (4%) on the soda lime glass (1.1mm) and the electrical signal detected on the X-ray sensor was increased in the high bias voltage. We acquired digital X-ray scanning image with our DAS (data acquisition system) and sensor scanning system.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.3
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• pp.39-46
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• 2016

Loss of postural stability can possibly lead to slip and fall accidents in the number of workplaces and everyday life. This study was aimed to examine the effects of whole body fatigue and partially limited visual field on the ability of maintaining postural balance during quiet standing. A group of twelve healthy male subjects participated in the experiment. Before and after experiencing the whole body fatigue induced by bicycling exercises, the position coordinates of subject's center of pressure (COP) were obtained under the two levels of visual field condition (i.e., open visual field and limited visual field). Four levels of the whole body fatigue examined were rest, 300watt, 600watt, and 900watt. Position coordinates of COPs measured on a force plate were then converted into the total length of postural sway path in both the medio-lateral (ML) direction and the anterior-posterior (AP) direction. Two-way ANOVA result showed that the length of sway path in the AP direction became significantly larger as the whole body fatigue accumulated. Post-hoc test revealed statistically significant differences between rest and 900watt and between 300watt and 900watt. The significant increase of the sway length was also found when the visual field was partially obstructed by the boxes. In the ML direction, however, there was no statistically significant difference of the postural sway in both the AP and ML directions. The results imply that the ability of maintaining postural stability can be reduced significantly due to such tasks along with whole body fatigue. The postural balance can also be impaired by the limited visual field.

• Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.349-362
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• 2016

The numerical solutions of unsteady hydromagnetic natural convection Couette flow of a viscous, incompressible and electrically conducting fluid between the two vertical parallel plates in the presence of thermal radiation, thermal diffusion and diffusion thermo are obtained here. The fundamental dimensionless governing coupled linear partial differential equations for impulsive movement and uniformly accelerated movement of the plate were solved by an efficient Finite Element Method. Computations were performed for a wide range of the governing flow parameters, viz., Thermal diffusion (Soret) and Diffusion thermo (Dufour) parameters, Magnetic field parameter, Prandtl number, Thermal radiation and Schmidt number. The effects of these flow parameters on the velocity (u), temperature (${\theta}$) and Concentration (${\phi}$) are shown graphically. Also the effects of these pertinent parameters on the skin-friction, the rate of heat and mass transfer are obtained and discussed numerically through tabular forms. These are in good agreement with earlier reported studies. Analysis indicates that the fluid velocity is an increasing function of Grashof numbers for heat and mass transfer, Soret and Dufour numbers whereas the Magnetic parameter, Thermal radiation parameter, Prandtl number and Schmidt number lead to reduction of the velocity profiles. Also, it is noticed that the rate of heat transfer coefficient and temperature profiles increase with decrease in the thermal radiation parameter and Prandtl number, whereas the reverse effect is observed with increase of Dufour number. Further, the concentration profiles increase with increase in the Soret number whereas reverse effect is seen by increasing the values of the Schmidt number.

• Journal of Life Science
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• v.8 no.3
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• pp.339-347
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• 1998

As a part of a study on the development of microbiological methods for petroleum exploration, the distribution of the avarafe survival rate for heterotrophs to various heavy metal ions and hydrocarbons were surveyed and compared by the use of plate count method. In consequence of the avarage survival rate to heavy metal ions(2 hours treatment) and hydrocarbons(1 hour treatment) for heterotrophs isolatinf from soil samples(50cm depth) which located in Doum mountain(A, B and D site) and Aedowon(C site) at Pohang area, the survival rate of heterotrophs for nickel(600ppm), cobalt(500ppm), cadmiun(100ppm), mercury(20ppm), zinc(400 ppm) and lead(500ppm) were 73.7%, 82.6%, 76.8%, 9.5%, 77.8% and 73.6% at A site and 67.9%, 82.5%, 86.0%, 5.8%, 82.5% and 91.7% at B site, 87.8%, 79.8%, 87.5%, 7.0%, 84.2% AND 47.7% AT c SITE, AND 71.8%, 76%, 85.9%, 1,2%, 79.6% AND 88.3% AT D site, respectively. Also the survival rate of heterotrophs from A,B,C and D site to pentane and hexane(each concentration is 20%) were 26.7% and 42.5%, 11.8% and 8.1%, 44.3% and 36.2%, and 12% and 3.5%, respectively. therefore, heterotrophs from B and D site that alternated gravelstone, muddy sandstone and sandstone were higher survival rate to the heavy metal ions than heterotrophs from A site which mainly composed gravelstone. Also, heterotrophs from C site which mainly composed muddy sandstone and once produced natural gas were showed relatively higher survival rate to the heavy metal ions and hydrocarbons than the other sites. Consequently, we confirmed that the distributions of tolerant heterotrophs to heavy metal ions and hydrocarbons were differ from the lithological compositon.

• Microbiology and Biotechnology Letters
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• v.36 no.3
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• pp.209-214
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• 2008

VBNC (Viable but nonculturable) state is an adaptive response of cells in adverse environments, which lead cell not grow on routine nutrient agar. In this study, we induced VBNC in Escherichia coli using copper and verify the characterization of it. After treatment of copper, we didn't detect any cells via plate cultivation, namely, colony forming unit (CFU) was zero. However, we identified the existence of VBNC by staining live cells with Live/Dead BacLight bacterial viability kit and counting them through flow cytometry. Then we isolated genomic DNA and RNA from VBNC-induced cells and analyzed the stability of them. Degradation of RNA is more severe than that of DNA and RNA is degraded as specific fragments. In addition, we showed the morphology of VBNC cell by Bio-Transmission Electron Microscope (Bio-TEM). VBNC cell showed impaired periplasmic space and inner and outer membrane were separated and the amount of cytosol were significantly decreased.

• Imaging Science in Dentistry
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• v.43 no.3
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• pp.145-151
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• 2013

Purpose: This study was performed to evaluate and compare the radiopacity of dentin, enamel, and 8 restorative composites on conventional radiograph and digital images with different resolutions. Materials and Methods: Specimens were fabricated from 8 materials and human molars were longitudinally sectioned 1.0 mm thick to include both enamel and dentin. The specimens and tooth sections were imaged by conventional radiograph using #4 sized intraoral film and digital images were taken in high speed and high resolution modes using a phosphor storage plate. Densitometric evaluation of the enamel, dentin, restorative materials, a lead sheet, and an aluminum step wedge was performed on the radiographic images. For the evaluation, the Al equivalent (mm) for each material was calculated. The data were analyzed using one-way ANOVA and Tukey's test (p<0.05), considering the material factor and then the radiographic method factor, individually. Results: The high speed mode allowed the highest radiopacity, while the high resolution mode generated the lowest values. Furthermore, the high resolution mode was the most efficient method for radiographic differentiation between restorative composites and dentin. The conventional radiograph was the most effective in enabling differentiation between enamel and composites. The high speed mode was the least effective in enabling radiographic differentiation between the dental tissues and restorative composites. Conclusion: The high speed mode of digital imaging was not effective for differentiation between enamel and composites. This made it less effective than the high resolution mode and conventional radiographs. All of the composites evaluated showed radiopacity values that fit the ISO 4049 recommendations.

• Tribology and Lubricants
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• v.31 no.1
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• pp.6-12
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• 2015

This paper investigates the stick-slip characteristic of magnetorheological elastomer (MRE) between an aluminum plate and the surface of the MRE. MRE is a smart material and it can change its mechanical behavior with the interior iron particles under the influence of an applied magnetic field. Stick-slip is a movement of two surfaces relative to each other that proceeds as a series of jerks caused by alternate sticking from friction and sliding when the friction is overcome by an applied force. This special tribology phenomenon can lead to unnecessary wear, vibration, noise, and reduced service life of work piece. The stick-slip phenomenon is avoided as far as possible in the field of mechanical engineering. As this phenomenon is a function of material property, applied load, and velocity, it can be controlled using the characteristics of MRE. MRE as a soft smart material, whose mechanical properties such as modulus and stiffness can be changed via the strength of an external magnetic field, has been widely studied as a prospective replacement for general rubber in the mechanical domain. In this study, friction force is measured under different loads, speed, and magnetic field strength. From the test results, it is confirmed that the stick-slip phenomenon can be minimized under optimum conditions and can be applied in various mechanical components.