• Parasites, Hosts and Diseases
• /
• v.33 no.1
• /
• pp.19-26
• /
• 1995

Ecological studies of Aedes togoi, the vector of malayan filariasis, were ci,wind out at Tolsando, Yosu and Sokcho area in 1991. The adult population of Aedes togoi was continuously appeared from the first week of April to the end of November showing the highest density in .truly. The larvae of Aedes togoi were found at rock pools from March to December in Sokcho area and the density was highest in July and August, whereas in the southern coastal area (Yosu), the larvae were found throughout the year and the density was the highest in Tune. The rate of larvae inhabited below 0.5% salinity was 45.7% in Sokcho and 51.7% in Yosu. The feeding activity of Aedes togoi was nocturnal, with the peak period of 01 :00-03:00 hours. Indoor feeding activities were slightly higher than outdoors showing the biting ratio of 1 :0.8 (indoor: outdoor). The average number of Aedes togoi attracted to CO2 gas was 8.5 whereas 117 Anophelei sinensis was attracted. The result indicates that CO2 is not an effective attractant for host seeking of Aedes togoi compared to Anopheles sineteis. The most common place was bedroom with 54.5% of total collections and next to stock place (18.2%), floor(9.1%) and kitchen (9.1%).

• Journal of the Korean Association of Geographic Information Studies
• /
• v.18 no.4
• /
• pp.43-58
• /
• 2015

The greenhouse gas emission caused by rapid economic growth and population is increasing in Korea. Also, climate change from greenhouse gases emission is accelerated. IPCC(Intergovernmental Panel on Climate Change) report projects an increase of greenhouse gas emissions by 90% from the year 2000 to 2030(SRES, 2000). Within this context, establishing countermeasures on climate adaptation and mitigation is becoming increasingly important to reduce the negative effect of climate change at a global level. Along with global efforts to tackle climate change, Korean government has incorporated 'Low Carbon Green Growth'strategies into its national policy agenda. Local governments have also conducted a number of studies to devise plans for environmentally friendly and sustainable city development. In this paper, the land-use equilibrium model, which reflects economic and geographical characteristics, is used to analyze the change in residential land use and population density. The target area for study is Jeju island in Korea. With an application of land use equilibrium model, it derived three types of scenarios of the land use change: (1) dispersion scenario-reflecting present-day conditions (2) adaptation scenario-applying adaptation measures to climate change and (3) combined scenario-integrating both adaptation and mitigation measures in model to climate change. By applying dispersion to combined scenario, the general trend shows a downward shift in population density. Subsequently, energy consumption and expected cost associated with casualties were calculated on the basis of the findings of respective scenario. The results show a descending trend in energy consumption and expected casualtie. Therefore, understanding for residential land use and population density of each scenario that analyzed land use equilibrium model in the study is expected to devise a environmental city plan for climate change stabilization and climate adaptation and mitigation.

• Journal of the Korean Applied Science and Technology
• /
• v.31 no.4
• /
• pp.562-571
• /
• 2014

In these days, many countries carry out many renewable energy policies to increase the renewable energy portion and to reduce the GHG(Green House Gas). In Korea, RPS(Renewable Portfolio Standards) focused on over 500MW power producers is conducting. And they are using the bio-fuel oil to meet their RPS quota. The oil is a mixture of animal and vegetable fat or fatty acid ester of them and should satisfy some specifications to use the power generation such as viscosity, pour point, acid number. Depends on the raw materials, quality characteristics of power bio-fuel oil are changed. By adding the power bio-fuel oil, pour point, density, sulfur content and viscosity are decreased and acid number, iodine number, oxygen content are increased. In this study, we test the quality characteristic of power bio-fuel oil and the property changes by the blending ratio of power bio-fuel oil & conventional fuel oil.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.3
• /
• pp.88-97
• /
• 2012

To measure the traffic pollutants with high temporal and spatial resolution under real conditions, a mobile emission laboratory (MEL) was designed. The equipment of the mini-van provides gas phase measurements of CO, NOx, CO2 and THC (Total hydrocarbon), and number density & size distribution measurements of fine and ultra-fine particles by a fast mobility particle sizer (FMPS) and a condensation particle counter (CPC). The inlet sampling port above the bumper enables the chasing of different type of vehicles. This paper introduces the technical details of the MEL and presents data from the experiment in which a MEL chases a city bus fuelled by diesel, DME and Bio-diesel. The dilution ratio was calculated by the ratio of ambient NOx and tail-pipe NOx. Most particles from the bus fuelled by diesel were counted under 300 nm and the peak concentration of the particles was located between 30 and 60 nm. However, most particles in the exhaust of the bus fuelled by DME were nano-particles (diameter: less than 50 nm). The bus fuelled by Bio-diesel shows less particle emissions compare to diesel bus due to the presence of the oxygen in the fuel.

• Electrical & Electronic Materials
• /
• v.9 no.8
• /
• pp.789-798
• /
• 1996

The double nitride layer Metal Nitride Oxide Semiconductor(MNOS) structures were fabricated by variating both gas ratio and nitride thickness, and by duplicating nitride deposited and one nitride layer MNOS structure to improve nonvolatile memory characteristics of MNOS structures by Low Pressure Chemical Vapor Deposition(LPCVD) method. The nonvolatile memory characteristics of write-in, erase, memory retention and degradation of Bias Temperature Stress(BTS) were investigated by the homemade automatic .DELTA. $V_{FB}$ measuring system. In the trap density double nitride layer structures were higher by 0.85*10$^{16}$ $m^{-2}$ than one nitride layer structure, and the AVFB with oxide field was linearly increased. However, one nitride layer structure was linearly increased and saturated above 9.07*10$^{8}$ V/m in oxide field. In the erase behavior, the hole injection from silicon instead of the trapped electron emission was observed, and also it was highly dependent upon the pulse amplitude and the pulse width. In the memory retentivity, double nitrite layer structures were superior to one nitride layer structure, and the decay rate of the trapped electron with increasing temperature was low. At increasing the number on BTS, the variance of AVFB of the double nitride layer structures was smaller than that of one nitride layer structure, and the trapped electron retention rate was high. In this paper, the double nitride layer structures were turned out to be useful in improving the nonvolatile memory characteristics.

• Journal of the Korea Institute of Building Construction
• /
• v.12 no.4
• /
• pp.377-385
• /
• 2012

In this study, the Impact resistance of steel fiber and organic fiber reinforced concrete and mortar was evaluated and the improvement in toughness resulting from an increase in compressive strength and mixing fiber for impact resistance on performance was examined. The types of fiber were steel fiber, PP and PVA, and these were mixed in at 0.1, 0.5 and 1.0 vol.%, respectively. Impact resistance is evaluated with an apparatus for testing impact resistance performance by high-speed projectile crash by gas-pressure. For the experimental conditions, Specimen size was $100{\times}100{\times}20$, 30mm ($width{\times}height{\times}thickness$). Projectile diameter was 7 and 10 mm and impact speed is 350m/s. After impact test, destruction grade, penetration depth, spalling thickness and crater area were evaluated. Through this evaluation, it was found that as compressive strength is increased, penetration is suppressed. In addition, as the mixing ratio of fiber is increased, the spalling thickness and crater area are suppressed. Organic fibers have lower density than the steel fiber, and population number per unit area is bigger. As a result, the improvement of impact resistance is more significant thanks to dispersion and degraded attachment performance.

• Journal of the Korean Chemical Society
• /
• v.44 no.6
• /
• pp.573-580
• /
• 2000

MPT, which has been developed recently, is very tolerant to aqueous samples. Several types of MPT have been investigated and is found that the double concentric tube could sustain a stable plasma at a low plasma gas flow rate. However, the tip of torch is easily ruined. Triple concentric torch has shown the best stability and the plasma shape, much like that of ICP, especially when the central channel is quartz. The plasma is exposed and mixed with air as is suggested from the background spectrum, which leads to quenching of He MPT. Sensitivity of helium MPT equipped with a membrane desolvator has shown 10 times lower than that of Argon MPT for most of elements except for the ones with relatively high excitation energy. He MPT requires small plasma flow rate (about 1.6 L/min), stable and simple to use. Excitational temperature and electron number density measured are 4950 K and 3.28 ${\times}$ $10^{14}cm^{-3}$, respectively.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1491-1493
• /
• 2000

Continuing improvement of microprocessor performance involves in the device size. This allow greater device speed, an increase in device packing density, and an increase in the number of functions that can reside on a single chip. However this has led to propagation delay, crosstalk noise, and power dissipation due to resistance-capacitance(RC) coupling become significant due to increased wiring capacitance, especially interline capacitance between the metal lines on the same metal level. So, MSSQ which has the permittivity between 2.5-3.2 is used to prevent from these problems. For pattering MSSQ(Methylsilsequioxane), we use RIE(Reactive Ion Etching) and MERIE(Magnetically enhanced Reactive Ion Etching) which could provide good anisotropic etching. In this study, we optimized the flow rate of $CF_{4}/O_2$ gas, RF power to obtain the best etching rate and roughness and also analyzed the etching result using $\alpha$-step profilemeter, SEM, infrared spectrum and AFM.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2004.03a
• /
• pp.75-78
• /
• 2004

Various jet engines (Turbine engine family and RAM Jet engine) have been developed for high speed aircrafts. but their application to hypersonic flight is restricted by principle problems such as increase of total pressure loss and thermal stress. Therefore, the development of next generation propulsion system for hypersonic aircraft is a very important subject in the aerospace engineering field, SCRAM Jet engine based on a key technology, Supersonic Combustion. is supposed as the best choice for the hypersonic flight. Since Supersonic Combustion requires both rapid ignition and stable flame holding within supersonic air stream, much attention have to be given on the mixing state between air stream and fuel flow. However. the wider diffusion of fuel is expected with less total pressure loss in the supersonic air stream. So. in this study the direction of fuel injection is inclined 30 degree to downstream and the total pressure of jet is controlled for lower penetration height than thickness of boundary layer. Under these flow configuration both streams, fuel and supersonic air stream, would not mix enough. To spread fuel wider into supersonic air an aerodynamic force, baroclinic torque, is adopted. Baroclinic torque is generated by a spatial misalignment between pressure gradient (shock wave plane) and density gradient (mixing layer). A wedge is installed in downstream of injector orifice to induce an oblique shock. The schlieren optical visualization from side transparent wall and the total pressure measurement at exit cross section of combustor estimate how mixing is enhanced by the incidence of shock wave into supersonic boundary layer composed by fuel and air. In this study non-combustionable helium gas is injected with total pressure 0.66㎫ instead of flammable fuel to clarify mixing process. Mach number 1.8. total pressure O.5㎫, total temperature 288K are set up for supersonic air stream.

• International Journal of Fluid Machinery and Systems
• /
• v.9 no.1
• /
• pp.66-74
• /
• 2016

Concerning the numerical simulation of high-speed water jet with intensive cavitation this paper presents a practical compressible mixture flow method by coupling a simplified estimation of bubble cavitation and a compressible mixture flow computation. The mean flow of two-phase mixture is calculated by URANS for compressible fluid. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase varying with the mean flow, and the effect of cavitation on the flow turbulence is considered by applying a density correction to the evaluation of eddy viscosity. High-speed submerged water jets issuing from a sheathed sharp-edge orifice nozzle are treated when the cavitation number, ${\sigma}=0.1$, and the computation result is compared with experimental data The result reveals that cavitation occurs initially at the entrance of orifice and bubble cloud develops gradually while flowing downstream along the shear layer. Developed bubble cloud breaks up and then sheds downstream periodically near the sheath exit. The pattern of cavitation cloud shedding evaluated by simulation agrees experimental one, and the possibility to capture the unsteadily shedding of cavitation clouds is demonstrated. The decay of core velocity in cavitating jet is delayed greatly compared to that in no-activation jet, and the effect of the nozzle sheath is demonstrated.