• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.8
• /
• pp.701-713
• /
• 2009

This paper studies a method for reducing performance degradation due to losing sub-carrier orthogonality caused by power transient between physical channels in LTE uplink transmission. The pattern of inter-carrier interference(ICI) caused by power transient is different from what has been studied for doppler shift, in that its pattern occurs at front and rear sides of channels in each period of power transient. The reason of ICI's occurrence results from power difference between channels, power transient duration, multi-path channel delay spread, and numbers of sub-carrier. New criterion is proposed to find out number of taps of multi-tap equalizer enough to improve the ICI. The scheme is to determine the number of taps of multi-tap equalizer when a normalized interference or a normalized ICI is greater than a normalized noise. Simulation results show that the number of taps is flexibly adjusted according to SNR(Signal to Noise Ratio) of a received signal to improve Bit Error Rate(BER), while the complexity of the proposed scheme is reduced down to 88 percentage of the classical method.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.12 no.3
• /
• pp.139-148
• /
• 2000

In this paper, the interaction of oblique incident waves with a bottom-mounted and fluid-filled flexible membrane structure is investigated in the frame of linear hydro-elastic theory. The static shape of a membrane structure containing the fluid of a specific density is initially unknown and must be calculated before the hydrodynamic analysis. To solve hydrodynamic problem, the fluid domain is divided into the inner and outer region. The inner solution based on discrete membrane dynamic model and simple-source distribution over the entire fluid boundaries is matched to the outer solution ba~ed on an eigenfunction expansion method. The numerical results were compared to a series of Ohyama's experimental results. The measured reflection and tran¬smission coefficients reasonably follow the trend of predicted values. Using the computer program developed, the performance of a bottom-mounted and fluid-filled flexible membrane strocture is tested with various system parameters (membrane shape, internal pressure, density ratio) and wave characteristics (wave frequencies, incident wave angle). It is found that a bottom-mounted and fluid-filled flexible membrane structure can be an effel;tive wave barrier if properly designed.

• Korean Journal of Environmental Agriculture
• /
• v.9 no.1
• /
• pp.15-22
• /
• 1990

The efects of application time on the persistence of chlorothalonil in sesame plants and its persistence in soil were studied in the field. A procedure was used which permited the analysis of residues of Chlorothalonil (DACONIL 2787) in sesame(Sesamum indicum L.)and soil. The procedure was based on the multiresidue analytical method using an polarized acetonitrile solution or acidified acetone as the extracting solvent. The DACONIL 2787 is separated from the fat in the extracts by using an activated alumina and Florisil chromatogaphic column. Residues of DACONIL 2787 were determined by subjecting the alternate eluate from the Florisil column to gas chromatographic analysis(ECD). Residue of chlorothalonil in sesame are proved to 0.06 ppm for six sprays, 3rd day before harvest The half-life of chlorothalonil in soil proved to be 8.9 days and residues of chlorothalonil was only 0.03 ppm 100 days after application of 15 ppm.

• Journal of the Korean Vacuum Society
• /
• v.22 no.6
• /
• pp.321-326
• /
• 2013

The effect of rapid thermal annealing (RTA) on the optical properties of digital-alloy InGaAlAs multiple quantum well (MQW) structures have been investigated by using photoluminescence (PL) and time-resolved PL measurements as a function of RTA temperature. The MQW samples were annealed from $700^{\circ}C$ to $850^{\circ}C$ for 30 s in a nitrogen atmosphere. The MQW sample annealed at $750^{\circ}C$ exhibited the strongest PL intensity and the narrowest FWHM (Full width at half maximum), indicating the reduced nonradiative recombination centers and the improved interfaces between the wells and barriers. The MQW samples annealed at $800^{\circ}C$ and $850^{\circ}C$ showed the decreased PL intensities and blueshifted PL peaks compared to $750^{\circ}C$-annealed sample. The blueshift of PL peak with increasing RTA temperatures are ascribed to the increase of aluminum due to intermixing of gallium (Ga) and aluminum (Al) in the interfaces of InGaAs/InAlAs short-period superlattices. The decrease of PL intensity after annealing at $800^{\circ}C$ and $850^{\circ}C$ are attributed to the interface roughening and lateral composition modulation caused by the interdiffusion of Ga and Al and indium segregation, respectively. With increasing RTA temperature the PL decay becomes slower, indicating the decrease of nonradiative defect centers. The optical properties of digital-alloy InGaAlAs MQW structures can be improved significantly with optimum RTA conditions.

• Korean Journal of Remote Sensing
• /
• v.32 no.2
• /
• pp.171-183
• /
• 2016

Land Surface Temperature (LST) retrieved from Landsat 8 measured from 2013 to 2014 and it is corrected by surface temperature observed from ground. LST maps are retrieved from Landsat 8 calculate using the linear regression function between raw Landsat 8 LST and ground surface temperature. Seasonal and annual LST maps developed an average LST from season to annual, respectively. While the higher LSTs distribute on the industrial and commercial area in urban, lower LSTs locate in surrounding rural, sea, river and high altitude mountain area over Seoul and surrounding area. In order to correct the LST, linear regression function calculate between Landsat 8 LST and ground surface temperature observed 3 Korea Meteorological Administration (KMA) synoptic stations (Seoul(ID: 108), Incheon(ID: 112) and Suwon(ID: 119)) on the Seoul and surrounding area. The slopes of regression function are 0.78 with all data and 0.88 with clear sky except 5 cloudy pixel data. And the original Landsat 8 LST have a correlation coefficient with 0.88 and Root Mean Square Error (RMSE) with $5.33^{\circ}C$. After LST correction, the LST have correlation coefficient with 0.98 and RMSE with $2.34^{\circ}C$ and the slope of regression equation improve the 0.95. Seasonal and annual LST maps represent from urban to rural area and from commercial to industrial region clearly. As a result, the Landsat 8 LST is more similar to the real state when corrected by surface temperature observed ground.

• Applied Chemistry for Engineering
• /
• v.9 no.2
• /
• pp.193-199
• /
• 1998

The mixtures of ultra-high molecular weight polythylene (UHMWPE), high density polyethylene (HDPE), process oil (mineral oil) and potassium hexatitanate whisker were melted and mixed at $150^{\circ}C$ for 30min, and prepared by compression molding to the specimen of separator of about $200{\mu}m$ thickness at the same temperature and 5000 psi. Thereafter the pores were formed by extracting process oil with organic solvents. In this study, the range of PR (the ratio polymer to process oil) was varied from 0.1 to 0.5 because the specimen turned into rubbery phase at which PR was below 0.1 whereas it changed into gel phase at which PR was above 0.5. When the specimen was treated with nonpolar organic solvents, process oil was extracted nearly 98%. Tensile strength was $31kg/cm^2$ at PR = 0.426, and resistance of specimen was $37m{\Omega}/cm^2$ at PR = 0.186, and $53m{\Omega}/cm^2$ at PR = 0.426. The $N_2$ adsorption-desorption isotherm showed a hysteresis representing regions of capillary condensation, and the surface area at PR = 0.186 was relatively large as $130cm^2/g$. Potassium hexatitanate whisker was randomly dispersed in between PE layers. It might be that the whisker is intercalated through the PE thin layers oriented by compression.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.1
• /
• pp.67-73
• /
• 2006

10 sites in building development areas were selected and the noise level were measured by the apartment floors of apartment complex. With the fitted regression analysis, the distribution ratio($R^2$) and correction coefficient(r) was 25%(0.5) in the NIER('87) and 7.5%(0.274) in the NIER('99), respectively. The measured values of the noise level on the seventh floor of complex did not show a good agreement with the predicted noise level in the NIER('87, '99) formula. However, the developed formula demonstrated that the measured values were reasonably close to the predicted values, indicating the validity and adequacy of the predicted models with the fitted vs residual analysis in the 95% of confidence interval and 95% of predict interval. The results suggested that application of this development model obtained by the results according to the apartment floor can be improved in road traffic noise.

• Journal of Korean Society of Environmental Engineers
• /
• v.28 no.8
• /
• pp.872-877
• /
• 2006

It has been concerned about the indoor air contaminants because of the hours spend in indoor space. These contaminants are emitted from various indoor facilities. Therefore, even though there concentrations are very low, adverse effects can't be ignored. However, treatment technologies are insufficient to deal with these contaminants. For this reason, the objective of this study was to investigate the feasibility of artificial ultraviolet(UV) detoxification using $TiO_2$ system for degrading formaldehyde contaminated indoor air. The experiment was also performed to investigate the formaldehyde removal effect of fluorescence lamp as an alternative UV light source because it is used in indoor as a light source. The results presented demonstrated that as the $TiO_2$ dosage is more and the reaction area is wider, the photocatalytic degradation rate does more enhanced. Degradation of TCE was more rapid used in $UV_{254}$ lamp than in fluorescence lamp. However, if it is operated during enough time, it will be able to remove the considerable quantity of TCE in case of using fluorescence lamp.

• Journal of Astronomy and Space Sciences
• /
• v.26 no.4
• /
• pp.521-528
• /
• 2009

While it is well known that space environment can produce spacecraft anomaly, defining space environment effects for each anomalies is difficult. This is caused by the fact that spacecraft anomaly shows various symptoms and reproducing it is impossible. In this study, we try to find the conditions of when spacecraft failures happen more frequently and give satellite operators useful information. Especially, our study focuses on the geosynchronous satellites which cost is high and required high reliability. We used satellite anomaly data given by Satellite News Digest which is internet newspaper providing space industry news. In our analysis, 88 anomaly cases occurred from 1997 to 2008 shows bad corelation with Kp index. Satellite malfunctions were likely to happen in spring and fall and in local time from midnight to dawn. In addition, we found the probability of anomaly increase when high energy electron flux is high. This is more clearly appeared in solar minimum than maximum period.

• Journal of the Korean Applied Science and Technology
• /
• v.36 no.4
• /
• pp.1281-1289
• /
• 2019

This study was conducted to evaluate the optimal operating condition of ultra-fine bubble washing machine for removing calcium chloride from road concrete structure. The diameter of the ultra-fine bubble was measured to 196.6 ± 100.6 nm and the ultra-fine bubble concentration was measured to 1.36 × 108 cell/ml. As a result of the performance on the spray device of the washing machine, it was confirmed that the washing efficiency of 93% and 91% appeared at 100cm and 150cm of injection distance at 100bar injection pressure. By increasing the ultra-fine bubble generation cycles from 2 to 6, the chloride removal rate increased from 1% to 7%. As the ultra-fine bubble generation air flow was lowered from 4 ml/min to 0.5 ml/min, it was confirmed that the washing efficiency increased up to 30%. The washing efficiency of ultra-fine bubble water was 25% higher than normal water.