• Current Photovoltaic Research
• /
• v.8 no.1
• /
• pp.17-26
• /
• 2020

It is clear that monocrystalline Silicon (Si) ingots are the key raw material for semiconductors devices. In the present industries markets, most of monocrystalline Silicon (Si) ingots are made by Czochralski Process due to their advantages with low production cost and the big crystal diameters in comparison with other manufacturing process such as Float-Zone technique. However, the disadvantage of Czochralski Process is the presence of impurities such as oxygen or carbon from the quartz and graphite crucible which later will resulted in defects and then lowering the efficiency of Si wafer. The heat transfer plays an important role in the formation of Si ingots. However, the heat transfer generates convection in Si molten state which induces the defects in Si crystal. In this study, a crystal growth simulation software was used to optimize the Si crystal growth process. The furnace and system design were modified. The results showed the melt-crystal interface shape can affect the Si crystal growth rate and defect points. In this study, the defect points and desired interface shape were controlled by specific crystal growth rate condition.

• Nuclear Engineering and Technology
• /
• v.38 no.3
• /
• pp.201-210
• /
• 2006

This article presents a brief overview of an important area of neutron scattering: the general principles and techniques of elastic, quasielastic and inelastic scattering from a system composed predominately of incoherent scatterers. The methodology is then applied to the study of water, specifically when it is confined in nanometer-scale environments. The confined water exhibits uniquely anomalous properties in the supercooled state. It also nourishes biological functions, and supports essential chemical reactions in living systems. We focus on recent investigations of water encapsulated in nanoporous silica and carbon nanotubes, hydrated water in proteins and water or hydroxyl species incorporated in nanostructured minerals. Through these scientific examples, we demonstrate the advantages derived from the high sensitivity of incoherent neutron spectroscopy to hydrogen atom motions and hydrogen-bond dynamics, aided by rigorous data interpretation method using molecular dynamics simulations or theoretical modelling. This enables us to probe the inter-/intramolecular vibrations and relaxation/diffusion processes of water molecules in a complex environment.

• Journal of Korean Elementary Science Education
• /
• v.27 no.3
• /
• pp.244-251
• /
• 2008

One of the problems with testing for the presence of $CO_2$ is that the results are not visible. In order to over-come this weak point, a new testing method was developed with BTB indicator equipment, that made the gas visible. After that, the experiment was performed and tested the effects of the new visible equipment. The visible equipment could be adapted to regular class use successfully. Also, it was effective in that it reduced waste of gas, minimized danger potential through use of $CO_2$ canisters and candle-sticks, and also increased knowledge about indicators. The new experimental method and equipment affected the students' interest. It is possible that the students' positive participation was due to their interest in the new apparatus and application of the visual senses. The new system was tested fer its effects on teaching content and helping to produce sustained memory of the content. There were no significant differences between the groups in terms of content learning on initial content memory. However, when students in both groups were tested 4 months later, the visual experiment group sustained memory performance, while the other group showed a significant decrease. Generally, boys score higher than girls in terms of interest and participation in experimental activities. In this case, however, there were no difference between groups. It may have been due to introduction of new equipment and different methods from the textbooks. So, this could increase participation in science using various experiments.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2003.05a
• /
• pp.294-299
• /
• 2003

The efficiency of complex slurry preparation route for the development of high performance RS-SiCf/SiC composites has been investigated. The green bodies for RS-SiC and RS-SiCf/SiC composite materials prior to the infiltration of molten silicon were prepared with various C/SiC complex matrix slurries, which associated with both different sizes of starting SiC particles and blending ratios of starting SiC and carbon particles. The reinforcing materials in the composite system were uncoated and C coated Tyranno SA SiC fiber. The characterization of RS-SiC and RS-SiCf/SiC composite materials was examined by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, process optimization methodology is discussed.

• Environmental Engineering Research
• /
• v.19 no.3
• /
• pp.197-203
• /
• 2014

This study estimated spatial and seasonal variation of water quality to understand characteristics of Nakdong river basin, Korea. All together 11 parameters (discharge, water temperature, dissolved oxygen, 5-day biochemical oxygen demand, chemical oxygen demand, pH, suspended solids, electrical conductivity, total nitrogen, total phosphorus, and total organic carbon) at 22 different sites for the period of 2003-2011 were analyzed using multivariate statistical techniques (cluster analysis, principal component analysis and factor analysis). Hierarchical cluster analysis grouped whole river basin into three zones, i.e., relatively less polluted (LP), medium polluted (MP) and highly polluted (HP) based on similarity of water quality characteristics. The results of factor analysis/principal component analysis explained up to 83.0%, 81.7% and 82.7% of total variance in water quality data of LP, MP, and HP zones, respectively. The rotated components of PCA obtained from factor analysis indicate that the parameters responsible for water quality variations were mainly related to discharge and total pollution loads (non-point pollution source) in LP, MP and HP areas; organic and nutrient pollution in LP and HP zones; and temperature, DO and TN in LP zone. This study demonstrates the usefulness of multivariate statistical techniques for analysis and interpretation of multi-parameter, multi-location and multi-year data sets.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
• /
• v.14 no.2
• /
• pp.198-206
• /
• 2001

Recurrent Bell's palsy is a very rare case and have been reported that shows the incidence to be approximately 10 per cent in the Bell's palsy patents. It is generally accepted that facial paralysis caused by compression of the facial nerve by tumor develops slowly and has an unremitting course, however, reported cases have described the rare association of recurrent facial paralysis and intracranial tumor, and the same recovery rate. Usual symptoms of Bell's palsy include subacute facial palsy, hyperacusis on the affected side, postauricular pain on the affected side, altered sensation of taste, and partial trigeminal distribution hypesthesias. Complete resolution of symptoms is usually seen in 2-3months in $75-85\%$ of cases, with $25-35\%$ showing varying degrees of residual effects. We report a case of 4th ipsilateral recurrent Bell's palsy in a 14-year-old women, which was occurred in every winters. We treated her with acupuncture, moxibustion, herbal medication, carbon and silver spike point, and used House-Brackmnn grading system(HBGS) and the Fisch Detailed Evaluation of Facial Symmetry(DEFS) to assess the degree of paralysis in each part of face.

• Advances in concrete construction
• /
• v.8 no.2
• /
• pp.145-154
• /
• 2019

The present experimental study addresses the structural response of reinforced concrete (RC) beams strengthened in shear. Thirteen RC beams were divided into four different sets to investigate the effect of transverse and longitudinal steel reinforcement ratios, concrete compressive strength change and orientation for installing carbon fiber-reinforced polymer (CFRP) laminates. Then, we employed a shear strengthening solution through externally bonded reinforcement in grooves (EBRIG) and externally bonded reinforcement (EBR) techniques. In this regard, rectangular beams of $200{\times}300{\times}2000mm$ dimensions were subjected to the 4-point static loading condition and their load-displacement curves, load-carrying capacity and ductility changes were compared. The results revealed that using EBRIG method, the gain percentage augmented with the increase in the longitudinal reinforcement ratio. Also, in the RC beams with stirrups, the gain in shear strength decreased as transverse reinforcement ratio increased. The results also revealed that the shear resistance obtained by the experimental tests were in acceptable agreement with the design equations. Besides, the results of this research indicated that using the EBRIG system through vertical grooves in RC beams with and without stirrups caused the energy absorption to increase about 85% and 97%, respectively, relative to the control.

• Korean Journal of Remote Sensing
• /
• v.35 no.1
• /
• pp.137-149
• /
• 2019

Traffic emissions are the main cause of environmental pollution in cities and respiratory problems amongst people. This study developed a model based on an integration of support vector regression (SVR) algorithm and geographic information system (GIS) to map traffic carbon monoxide (CO) concentrations and produce prediction maps from micro level to macro level at a particular time gap in a day in a very densely populated area (Utara-Selatan Expressway-NKVE, Kuala Lumpur, Malaysia). The proposed model comprised two models: the first model was implemented to estimate traffic CO concentrations using the SVR model, and the second model was applied to create prediction maps at different times a day using the GIS approach. The parameters for analysis were collected from field survey and remote sensing data sources such as very-high-resolution aerial photos and light detection and ranging point clouds. The correlation coefficient was 0.97, the mean absolute error was 1.401 ppm and the root mean square error was 2.45 ppm. The proposed models can be effectively implemented as decision-making tools to find a suitable solution for mitigating traffic jams near tollgates, highways and road networks.

• Journal of Korea Soil Environment Society
• /
• v.2 no.1
• /
• pp.83-90
• /
• 1997

Aiming at the treatment of large volumes of gas with a low concentration of poorly water soluble VOC(Volatile Organic Compound), a new system is proposed: the combination absorption tower/bioreactor. In the scrubber part of the bioscrubbing system, the contaminating compounds are absorbed in a aqueous phase. The contaminated scrubbing liquid is transported to the bioreactor, where the compounds are biodegraded by aerobic microorganisms (mainly to carbon dioxide, water, and biomass). In this study, separation of a volatile organic compound(VOC) out of a waste gas stream has been carried out using a re-cyclable high boiling point extrant(HBE). The liquid stream containing a high boiling point entrant(HBE) scrubs the gas stream in a direct gas-liquid countercurrent contacting operation in a packed tower for the removal of said component from the gaseous stream. A packed-bed column using Pall Ring was set up in order to simulate practical conditions for the scrubbing tower. The liquid stream transported to the bioreactor is recovered and recycled to the scrubber. The model gas, which contained 400 mg/$\textrm{m}^3$ of toluene, at a rate of 100 L/min, flowed into the packed column where the scrubbing liquid trickled over the packing in countercurrent to the rising gas at 10~15L/min. The bioscrubber designed for large volume air streams containing VOCs showed removal efficiency up to 80% in an optimum operating conditions during the tests fer removing toluene from an air stream by scrubbing the air stream with HBE.

• Journal of the Korea Society of Computer and Information
• /
• v.21 no.5
• /
• pp.177-184
• /
• 2016

Since 1980s, 30 years has passed after issues on environmental refugee began to appear. However, why environmental refugee is not considered as refugee officially in international society? Above all, it seems that main point is the responsibility given to those developed countries if they, whom led the climate changes, officially acknowledge environmental refugee. The problem is that environmental refugee has no direct responsibility for causing climate changes. Actually. the responsibility should be granted to the developed and industrialized countries which caused climate changes. In accordance to the refugee protection system established under current international law, it is difficult to include them into refugee category and thus, they can hardly have enough support. It is urgently needed that new refugee treat which have the new standard and solution added to it shall be adopted. To allow new refugee treat to be effective it is compulsory to have constant and binding policy determination and willingness of execution from a united international organization. Of course, before this, countries should try to have common recognition on recognizing new refugee problem and its seriousness as well as solving those problems together. In reality, it is worth considering adoption of semi-forceable type of system as a more effective way, which allocates responsibility of accepting refugee by amount of carbon emitted. Also, as refugee issue has an important influence on mother company and the third countries, execution process of the system has to be defined clearly. For those permanent organizations, they should accurately define environmental factors making refugee and set standards to minimize possibility of abuse and misuse.