• Journal of Bio-Environment Control
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• v.27 no.4
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• pp.277-284
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• 2018

For the main variables to be selected by the designer for the heating and cooling load calculation in greenhouses, in order to evaluate the effect of these design values on the heating and cooling load, the simulations were carried out by varying the respective design values. Based on these results, we proposed the design values which should pay special attention to selection. The design values which have the greatest effect on the heating load were the overall heat transfer coefficient of the covering material and the design outdoor temperature was next. The effect of the design values according to the number of spans showed little difference. In the case of the single-span greenhouse, the effect of the design values related to the underground heat transfer can not be ignored. However, in the case of the multi-span greenhouse, the effect of the design values related to the underground heat transfer and the infiltration rate were insignificant. The design values which have the greatest effect on the cooling load were the solar radiation into the greenhouse and the evapotranspiration coefficient, followed by the indoor and outdoor temperature difference and the ventilation rate. The effect of the design values showed a great difference between the single-span greenhouse and the multi-span greenhouse, but there was almost no difference according to the number of spans. The effect of the overall heat transfer coefficient of the covering material was negligible in both the single-span greenhouse and the multi-span greenhouse. However, the effect of the indoor and outdoor temperature difference and the ventilation rate on the cooling load was not negligible. Especially, it is considered that the effect is larger in multi-span greenhouse.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.8-15
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• 2006

In this paper, we propose the iterative receiver for LDPC-coded OFDMA systems in uplink environments. Applying the Wiener filtering to pilot symbols, an initial channel estimation can be performed effectively. To reduce the complexity of the Wiener filtering, we approximate Wiener filtering coefficients to pre-determined coefficients according to estimated correlation of channel. After an LDPC decoding process, soft symbol derived by extrinsic information of decoder outputs is used to estimate channel. we also derive the error variance of channel estimation and maximum ratio combined results. Using combined results, the channel correlation is re-estimated. Then the proper Wiener filtering coefficients are chosen according to the re-estimated result of the channel correction. Using a computer simulation, we show that the proposed receiver structure has the better performance than the receiver using only pilot symbols.

• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.395-401
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• 2005

In this paper, the high-band codec for bandwidth scalable wideband speech codec is proposed. The wideband input speech signal is separated into low-band signal and high-band signal, and the low-band signal is encoded by the standard narrow-band speech codec and the high-band signal is encoded by the proposed codec. In the high-band codec. the signal is transformed into frequency domain by MLT on a subframe basis, and MLT coefficients are splitted into magnitude and sign for quantization. The magnitudes of MLT coefficients are arranged into several time-frequency bands and each band is quantized in 2D-DCT domain, where the low-band information is utilized for better performance. The sign of MLT coefficient is quantized based on a priority selection process with the weighting measurement. The objective and subjective performance of wideband speech codec including the proposed high-band codec is measured, and it is confirmed that the proposed codec has better performance than 32kbps G.722.1.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.153-160
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• 2009

In relation to digital elevation model(DEM) production using high resolution satellite imagery, existing studies present that DEM accuracy differently show according to land cover property. This study therefore proposes auto-selection method of window size for correlation matching according to land cover property of IKONOS Geo-level stereo image. For this, land cover classified image is obtained by IKONOS color image with four bands. In addition, correlation-coefficients are computed at regular intervals in pixels of the window-search area to shorten of matching time. As the results, DEM by the proposed method showed more accurate than DEM using the fixed window-size matching. We estimate that accuracy of the proposed DEM improved more than DEM by digital map and ERDAS in agricultural land.

• Korean Journal of Remote Sensing
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• v.25 no.1
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• pp.21-30
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• 2009

The purposes of this paper are to present a selection method of neighboring pixels whose local statistics are similar to the center pixel and combine the selection result with mean curvature diffusion filter to reduce noises in remote sensed imagery. The order of selection of neighboring pixels is critical, especially for finding a pixel belonging to the homogeneous region, since the statistics of the homogeneous region vary according to the selection order. An effective strategy for selecting neighboring pixels, which uses rank-order differences vector obtained by computing the intensity differences between the center pixel and neighboring pixels and arranging them in ascending order, is proposed in this paper. By using region growing method, we divide the elements of the rank-ordered differences vector into two groups, homogeneous rank-ordered differences vector and outlier rank-ordered differences vector. The mean curvature diffusion filter is combined with a line process, which chooses selectively diffusion coefficient of the neighboring pixels belonging into homogeneous rank-ordered differences vector. Experimental results using an aerial image and a TerraSAR-X satellite image showed that the proposed method reduced more efficiently noises than some conventional adaptive filters using all neighboring pixels in updating the center pixel.

• Membrane Journal
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• v.24 no.2
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• pp.100-106
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• 2014

In this work, soluble polyimides were synthesized and characterized from 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) and two diamines such as 4,4'-diaminodiphenylether (ODA), 1,4-phenylenediamine (p-PDA). Their thermal properties were analyzed with differential scanning calorimeter (DSC). The gas permeability coefficients (P) and ideal selectivity for $CH_4$ and $CO_2$ of the prepared polyimide membranes were measured with a time-lag apparatus. DOCDA-ODA, DOCDA-p-PDA showed good permeability and selectivity; the permeabilities of $CO_2$ was 6.10, 0.74 barrers and the selectivity of $CO_2/CH_4$ were 67.03, 46.25, respectively. Therefore, DOCDA-ODA showed good possibility as gas separation membrane.

• Membrane Journal
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• v.17 no.3
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• pp.184-190
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• 2007

This study reports on the pervaporation separation of a volatile organic compound(VOC), dichloromethane(DCM) from water using fluorinated copolysiloxaneimide membranes. The copolysiloxaneimide membranes were prepared from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride(6FDA) and two diamines(polysiloxane diamine(SIDA), 2-(perfluorohexyl)ethyl-3,5-diaminobenzene(PFDAB)). By varying the ratio of flexible polysiloxane diamine(SIDA)/rigid fluorinated aromatic diamine(PFDAB) from 0/100 to 100/0 mol%, five copolysiloxaneimide membranes were prepared success- fully. The pervaporation properties of DCM/water were examined in terms of two diamine monomer ratio at room temperature and the feed composition of 0.05 wt% in water. It was found that the increase in SIDA content led to high permeation flux and pervaporation selectivity towards DCM by the enhanced sorption/sorption selectivity and diffusion coefficient/diffusion selectivity due to the increased hydrophobicity and fractional free volume.

• Membrane Journal
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• v.1 no.1
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• pp.34-43
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• 1991

The relationships between affinity of membranes and optimum operation conditions were investigated in the pervaporation of water(1)/ethanol(2) mixture through cellulose acetate(CA) membranes having more affinity to water and silicone rubber(SR) membranes having more affinity to ethanol. CA and SR membranes were prepared and amount of sorption, sorption selectivity, pervaporation separation factor and pervaporation rate in both of membranes were determined and compared. The effects of downstream pressure were analyzed using Thompson diagram and the sorption and pervaporation characteristics with composition of feed and operation temperature were examined in terms of affinity, activity coefficient, plasticizing effect and activation energy of individual species. In the separation of water through CA membranes, high performance of both pervaporation separation factor (water to ethanol, $[\alpha^2_1]_{PV}$) and pervaporation rate was obtained in the conditions of low downstream pressure, middle range of feed concentration and high temperature. In the separation of ethanol through SR membranes, pervaporation separation factor(ethanol to water, $[\alpha^2_1]_{PV}$) increased with downstream pressure and decreased with concentration of ethanol in feed and operation temperature, while pervaporation rate showed opposite trends to those of ($[\alpha^2_1]_{PV}$).

• Journal of the Korean Data and Information Science Society
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• v.20 no.5
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• pp.819-827
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• 2009

This study was conducted to investigate the relationship between the sociodemographic factors and the Korean consumers palatability evaluation grades with Hanwoo sensory evaluation data. The dichotomy logistic regression model and the multinomial logistic regression model are fitted with the independent variables such as the consumer living location, age, gender, occupation, monthly income, and beef cut and the the palatability grade as the dependent variable. Stepwise variable selection procedure is incorporated to find the final model and odds ratios are calculated to find the associations between categories.

• Journal of Broadcast Engineering
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• v.4 no.2
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• pp.155-163
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• 1999

In this paper, we propose novel scene change detection and key frame selection techniques, which use two feature images, i.e., DC and edge images, extracted directly from MPEG compressed video. For fast edge image extraction. we suggest to utilize 5 lower AC coefficients of each DCT. Based on this scheme, we present another edge image extraction technique using AC prediction. Although the former is superior to the latter in terms of visual quality, both methods all can extract important edge features well. Simulation results indicate that scene changes such as cut. fades, and dissolves can be correctly detected by using the edge energy diagram obtained from edge images and histograms from DC images. In addition. we find that our edge images are comparable to those obtained in the spatial domain while keeping much lower computational cost. And based on HVS, a key frame of each scene can also be selected. In comparison with an existing method using optical flow. our scheme can select semantic key frames because we only use the above edge and DC images.