• Proceeding of EDISON Challenge
• /
• 2015.03a
• /
• pp.324-329
• /
• 2015

First-principles investigations on the hybrid one dementional hexagonal hybrboron-nitride nano ribbons (BNNRs) with a armchair graphene nano-ribbons(AGRNRs), are presented. Electronics properties of the mixed armchair BNC nano-ribbon (BNCNRs) structure show control of a band gap on all cases at the special K-point. And we have studied, the band gap is direct in all cases. The band gap of mixed ABNCNRs could be divided into three groups (${\Delta}3p$, ${\Delta}3p+1$ and ${\Delta}3p+2$) and decrease with the increase of the width. Also these results show similar to the AGNRs case. Different from the band gap value ordering of AGNRs (${\Delta}3p+1$ > ${\Delta}3p$ > ${\Delta}3p+2$), the ordering of ABNCNRs is ${\Delta}3p$ > ${\Delta}3p+1$ > ${\Delta}3p+2$. The discrepancy may come from the differences between the edges of AGRNRs and the boundaries of hybrid BNCNRs. In addition, the bandgap of ABNCNRs are much smaller than those of the corresponding AGNRs. Our results show that the origin of band gap for BNCNRs with armchair shaped edges arises from both quantum confinement effect of the edges. These results similar to thecase of AGNRs. These properties of hybrid BN/C nano-ribbon structure may offer suitable bandgap to develop nnanoscale electronics and solar cell beyond individual GNRs and BNNRs.

• Steel and Composite Structures
• /
• v.19 no.3
• /
• pp.661-678
• /
• 2015

Buckling Restrained Braces (BRB) have been widely used in the construction industry as they utilize the most desirable properties of both constituent materials, i.e., steel and concrete. They present excellent structural qualities such as high load bearing capacity, ductility, energy-absorption capability and good structural fire behaviour. The effects of size and type of filler material in the existed gap at the steel core-concrete interface as well as the element's cross sectional shape, on BRB's fire resistance capacity was investigated in this paper. A nonlinear sequentially-coupled thermal-stress three-dimensional model was presented and validated by experimental results. Variation of the samples was described by three groups containing, the steel cores with the same cross section areas and equal yield strength but different materials (metal and concrete) and sizes for the gap. Responses in terms of temperature distribution, critical temperature, heating elapsed time and contraction level of BRB element were examined. The study showed that the superior fire performance of BRB was obtained by altering the filler material in the gap from metal to concrete as well as by increasing the size of the gap. Also, cylindrical BRB performed better under fire conditions compared to the rectangular cross section.

• Journal of computational fluids engineering
• /
• v.16 no.3
• /
• pp.95-103
• /
• 2011

In the block type VHTR core, there are inevitable gaps among core blocks for the installation and refueling of the fuel blocks. These gaps are called bypass gap and the bypass flow is defined as a coolant flows through the bypass gap. Distribution of core bypass flow varies according to the reactor operation since the graphite core blocks are deformed by the fast neutron irradiation and thermal expansion. Furthermore, the cross-flow through an interfacial gap between the stacked blocks causes flow mixing between the coolant holes and bypass gap, so that complicated flow distribution occurs in the core. Since the bypass flow affects core thermal margin and reactor efficiency, accurate prediction and evaluation of the core bypass flow are very important. In this regard, experimental and computational studies were carried out to evaluate the core bypass flow distribution. A multi-block experimental apparatus was constructed to measure flow and pressure distribution. Multi-block effect such as cross flow phenomenon was investigated in the experiment. The experimental data were used to validate a CFD model foranalysis of bypass flow characteristics in detail.

• Journal of the Korean Society of Physical Medicine
• /
• v.7 no.3
• /
• pp.349-356
• /
• 2012

Purpose : This study was designed to investigate the effects of pulsed electromagnetic field on functional recovery and expression of GAP-43 after incomplete spinal cord injury (SCI) in rats. Methods : To confirm the damage of SCI and effects of pulsed electromagnetic field, 20 Sprague-Dawley male rats were used and divided randomly 2groups (SCI, PEMF). Incomplete SCI was induced by using modified NYU drop model. After operation, functional recovery test, immunohistochemistry and western blot analysis were measured at 1, 2, 3 weeks. Pulsed electromagnetic field were apply three weeks (one times a day, five days a week and twenty minutes a session). Results : In the this study, applications of pulsed electromagnetic field after incomplete SCI induced the significant improvement in functional recovery and expression of neurotrophic factor. The results were as follows; Foot print test, PEMF were significantly decreased than the SCI (p<.05). Expression of GAP-43, PEMF were significantly increased than the SCI at 2 and 3 weeks (p<.05). Conclusion : In conclusion, pulsed electromagnetic field were positive effect in functional recovery and expression of GAP-43 after incomplete SCI in rats.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.2
• /
• pp.96-107
• /
• 2018

Flow analysis using computational fluid dynamics was conducted to investigate the effect of the igniter flame caused by the gap between the igniter and the propellant grain in a solid rocket motor. Two propellant grain types were assumed; namely cylinder type (1 mm, 3 mm, and 5 mm gap) and the slot type. The slot type had two igniter hole locations. One was located at the small gap of the propellant grain, and the other one was located at the large gap. In the case of the cylinder type, the pressure in the igniter zone was higher with a thinner gap. Additionally, in the case of the cylinder type, the pressure difference between the igniter installed zone and the free volume was also higher as the gap became lower. The cylinder types were affected by the gap distance, but the slot types were not. Moreover, the results of the slot types were similar to the 5-mm gap case of the cylinder type.

• Tuberculosis and Respiratory Diseases
• /
• v.44 no.1
• /
• pp.162-174
• /
• 1997

Background : Metabolic cooperation via gap junctional intercellular communication (GJIC) is an important mechanism of the bystander effect in gene therapy using the Herpes Simplex Virus thymidine kinase/ganciclovir (HSVtk) "prodrug" system. Since retinoids have been reported to increase GJIC by induction of connexin 43 expression, we hyporthesized that treatment of tumor cells with retinoic acid could augment the bystander effect of the HSVtk/GCV system and result in improved tumor cell killing by enhancing GJIC. Methods : We transferred HSVtk gene to SKHep-J cell line that does not express connexin43, and also transferred the gene to human and murine mesothelioma cell lines that express connexin43. We verified that retinoic acid enhanced GJIC utilizing a functional double-dye transfer study and evaluated the effects of retinoic acid on the growth rate of tumor cells. We then tested the effects of retinoic acid on bystander-mediated cell killing. Results : Addition of all-trans retinoic acid (RA) increased GJIC in cell lines expressing connexin 43 and was asspciated with more efficient in vitro bystander killing in cells transduced with HSVtk via adenoviral and retroviral vectors. In contrast, there was no increase in the efficiency of the bystander effect after exposure to RA in a cell line which had no delectable connexin 43. Conclusion : These results provide evidence that retinoids can augment the efficiency of cell killing with the HSVtk/GCV system by enhancing bystander effect and may thus be a promising new approach to improve responses in gene therapy utilizing the HSVtk system to treat tumors.

• Korean Management Science Review
• /
• v.34 no.3
• /
• pp.1-14
• /
• 2017

This study empirically analyzes the impact of inventory management performance on the energy efficiency in Korean petrochemical companies. The concept of the distance function is used to define the energy efficiency and the estimation of the distance function is performed using the stochastic frontier analysis. The inventory turnover is selected as the variable indicating the inventory management performance of the company. The main results of this study are as follows. First, the inventory turnover has a positive impact on energy efficiency. Second, during the period over 2011~2015, while the gap in energy efficiency among the companies expanded, the average energy efficiency decreased. Third, the average energy efficiency in upstream process companies was greater than downstream process companies and the gap in energy efficiency among downstream process companies was greater than upstream process companies. Fourth, the average marginal effect of inventory turnover on energy efficiency increased gradually from 2011 to 2015. Finally, the average marginal effect of inventory turnover in downstream process companies was greater than upstream process companies, and the gap in the marginal effect of inventory turnover among downstream process companies was greater than upstream process companies. These results together imply the importance of inventory management in terms of energy efficiency.

• Electrical & Electronic Materials
• /
• v.8 no.4
• /
• pp.472-477
• /
• 1995

The degree of the photodoping process in Ag(100[.angs.])/a-Se$_{75}$Ge$_{25}$(1500[.angs.]) films has measured as a function of the photon energy between 1.5[eV] and 2.9[eV] with the exposing time. The "window" characteristics of Ag occur at 3400[.angs.] (3.65[eV]) and Ag is almost transparent in this region. It is shown that transmittance is almost constant (40-50%) for the wavelength ranges of our experiment. It is found that the energy gap of a unexposed a-Se$_{75}$Ge$_{25}$ film is 1.81[eV]. Ag photodoping process results in the photodarkening effect which the absorption edge shifts to the long wavelength. Especially, very large band shift (-0.3[eV]) is obtained by exposing He-Ne laser(6328[.angs.]).. We have obtained "the U-type property" for Ar He-Ne and semiconductor laser. It is associated with the variation of energy gap(E$_{g}$) with photo-dose and substantially is explained by DWP model.l.gap(E$_{g}$) with photo-dose and substantially is explained by DWP model.

• Membrane and Water Treatment
• /
• v.8 no.6
• /
• pp.529-541
• /
• 2017

A multi-effect air gap membrane distillation (ME-AGMD) module for pesticide wastewater treatment is studied with internal heat recovery, sensible heat of brine recovery, number of stages and the use of fresh feed as cooling water in a single module is implemented in this study. A flat sheet polytetrafluroethylene (PTFE) membrane was used in the 4-stage ME-AGMD module. The maximum value of permeate flux could reach $38.62L/m^2h$ at feed -coolant water temperature difference about $52^{\circ}C$. The performance parameter of the module like, specific energy consumption and gain output ratio (GOR) was investigated for the module with and without heat recovery. Also, the module performance was characterized with respect to the separation efficiency of several important water quality parameters. The removal efficiency of the module was found to be >98.8% irrespective water quality parameters. During the experiment the membrane fouling was caused due to the deposition of the salt/crystal on the membrane surface. The membrane fouling was controlled by membrane module washing cycle 9 h and also by acidification of the feed water (pH=4) using 0.1M HCl solution.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.14 no.4
• /
• pp.1-10
• /
• 2006

A computational study was carried out in order to investigate the ground effect of a circular cylinder in the presence of a moving wall at a Reynolds number of 2.0${\times}$104. The viscous-incompressible Navier-Stokes equations and Spalart-Allmaras turbulent model of the commercial CFD code were adopted for this numerical analysis. The moving wall was set parallel with the freestream, and the speed of motion was equal to the freestream velocity. The gap ratio is defined as the distance ratio between the circular cylinder diameter and the height from the moving wall. The numerical results show that there are the differences among the each of the stages in evidence of the vorticity contours and the polar diagrams of $C_l$ vs. $C_d$. The 4 stages of the gap ratio are defined according to the flow features, whose stages are divided into small, intermediate, large and convergence gap ratios, respectively.