• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4C
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• pp.232-240
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• 2011

While the water-filling algorithm is an efficient power allocation method that maximizes the ergodic capacity of adaptive MIMO systems, its excessive residual power causes spectrum loss in real systems employing discrete modulation indices. In this paper we propose new power allocation algorithms that improve the spectral efficiency of MIMO systems by efficiently reallocating the residual power of the water-filling algorithm. We apply the proposed algorithms to the adaptive turbo-coded MIMO system to verify their performance through computer simulation in various environments. Simulation results show that the spectral efficiency of the proposed algorithms is better than that of the water-filling algorithm by about 8.9% at SNR of 20dB in Rayleigh fading environments.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.5
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• pp.547-554
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• 2010

This study intends to analyze how long the landfill site will be available by estimating maximum volume of landfill. Preestimated volume was calculated using digital maps and scheme drawings. The latest reclamation volume was measured using the state-of-the-art airborne LiDAR technology. Based on these data. landfill volume of now, carries in volume of past a few years and subsidence rate were calculated. As a result of study, the remaining capacity of this landfill site was estimated that it would be available till 2045.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.780-783
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• 2010

Net residual dispersion (NRD) available to transmit RZ formats with different 24 wavelength as a function of duty cycles of RZ format and residual dispersion per span (RDPS) is induced by controlling precompensation only in 960 km optical transmission links of single mode fiber (SMF) with inline dispersion management (DM) for compensating of accumulated dispersion. It is confirmed that effective NRD range for different 24 wavelengths is gradually broadening as RDPS is more smaller, and as duty cycle of RZ format is more larger in the same RDPS.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.4
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• pp.71-76
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• 2011

Earth to air heat exchangers made by iron, aluminium, copper and poly-ethylene pipe for single greenhouse heating were experimented and blowers. Earth to air heat exchanger was installed by pipelines in earth tube at 70cm depths and air blower was the heating capacity 3kW/h, As the result, Temperature difference due to temperature history of the inlet and outlet air on the various type in earth tube in greenhouse showed that air temperature at the various type in earth tube, comparison tube were make no difference respectively. Under the experimental condition, heat fluxes and heating load were showed 6,800Kcal/h, 19,699kcal/h generally yield of Lactuca Sativa cultured during days of sowing 90day in greenhouse using copper pipe was 170% incleased.

• Journal of the Society of Naval Architects of Korea
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• v.57 no.6
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• pp.312-321
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• 2020

In this study, machine learning techniques were applied to predict the residual resistance coefficient (Cr) of low-speed full ships. The used machine learning methods are Ridge regression, support vector regression, random forest, neural network and their ensemble model. 19 hull form variables were used as input variables for machine learning methods. The hull form variables and Cr data obtained from 139 hull forms of KRISO database were used in analysis. 80 % of the total data were used as training models and the rest as validation. Some non-linear models showed the overfitted results and the ensemble model showed better results than others.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.4
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• pp.243-250
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• 2022

In the design stage of hull forms, a fast prediction method of resistance performance is needed. In these days, large test matrix of candidate hull forms is tested using Computational Fluid Dynamics (CFD) in order to choose the best hull form before the model test. This process requires large computing times and resources. If there is a fast and reliable prediction method for hull form performance, it can be used as the first filter before applying CFD. In this paper, we suggest the offset-based performance prediction method. The hull form geometry information is applied in the form of 2D offset (non-dimensionalized by breadth and draft), and it is studied using Convolutional Neural Network (CNN) and adapted to the model test results (Residual Resistance Coefficient; C_R). Some additional variables which are not included in the offset data such as main dimensions are merged with the offset data in the process. The present model shows better performance comparing with the simple regression models.

• Journal of Drive and Control
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• v.19 no.1
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• pp.26-33
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• 2022

This study dealt with a self-propelled spinach harvester, which is capable of carrying out sequential harvesting work. This study aimed to find the cause of the harvester's occasional performance deterioration, which occurs in the process of simplifying the hydraulic circuit, using a multi-domain analysis model. The study was carried out in the following manner. First, a hydraulic system analysis model, which combines linear motion, rotary motion, hydrodynamic behavior, and an electrical signal, was developed through SimulationX software, specialized in multi-domain analysis. Second, a scenario for single behavior and coupled behavior was set out on an actuator basis. Third, the flow rate of the hydraulic system, which is not required for the movement of the actuator, was quantitatively analyzed. The results showed that a change in oil temperature was the cause of the harvester's occasional performance deterioration. And the higher the oil temperature, the more serious the performance deterioration, especially as the number of actuators operated simultaneously was small.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.8
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• pp.561-569
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• 2014

This study was carried out to get the characteristics of anaerobic digestion for chemical/biological sludge produced from municipal sewage treatment plant for phosphorus. Anaerobic mesophilic batch tests showed that the ultimate biodegradability of waste activated sludge showed 31%, PACl sludge 24%, Alum sludge 26%, respectively. At the S/I 1.0, 75% of total biodegradable volatile solids (TBVS) of waste activated sludge was degraded with an initial rapid decay coefficient, k1 of $0.1129day^{-1}$ and 74% of TBVS of PACl sludge with k1 of $0.0998day^{-1}$, and 76% of TBVS of Alum sludge with k1 of $0.1091day^{-1}$ for 20 days. During the operation of SCFMRs, the 3 reactor (Control, PACl, Alum) pH maintained 6.7~7.0 and the reactor alkalinity maintained 1,800~ 2,200 mg/L as $CaCO_3$. The average biogas production rates of SCFMRs fed with PACl sludge and Alum sludge were 0.089 v/v-d and 0.091 v/v-d, respectively, which was 27~28% lower than that of the control (0.124 v/v-d) at an HRT (hydraulic retention times) of 20 days. And the methane content during the operation ranged 70~76% in 3 reactor. The average TVS removal efficiency of SCFMRs fed with PACl sludge and Alum sludge were 19.6% and 19.9%, respectively, at an HRT of 20 days, which showed 4% lower than that of the control (23.8%). The average BVS removal efficiency of SCFMRs fed with PACl sludge and Alum sludge were 25.8% and 26.9%, respectively, at an HRT of 20 days, which was 8~9% lower than that of the control (34.5%).

• Journal of Bio-Environment Control
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• v.25 no.2
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• pp.83-88
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• 2016

In this study, previously reported surplus solar energy-related study result and current status of fan coil unit (FCU) for cooling and heating installed in the current sites were briefly examined and then a method to determine the number of FCUs required to recover surplus solar energy was schematically proposed to provide basic data for researchers and technical engineers in this field. The maximum, mean, and minimum outside temperatures during the experiment period were about $28.2^{\circ}C$, $4.4^{\circ}C$, and $-11.5^{\circ}C$, respectively. The horizontal surface solar radiation level outside the greenhouse was in a range of $0.8-20.5MJ{\cdot}m^{-2}$ and mean and total solar radiation were $10.8MJ{\cdot}m^{-2}$ and $1,187.5MJ{\cdot}m^{-2}$. The mean temperature and relative humidity in the greenhouse during the daytime were in a range of 18.8-45.5 and 53.5-77.5%. The total surplus solar energy recovered from the greenhouse during the experiment period was approximately 6,613.4MJ, which could supplement about 6.7% of the total heating energy 98,600.2 MJ. In addition, the number of FCUs installed for heating varies case to case, although similar FCUs are used. Thus, it is necessary to study the installation height, orientation and installation distance as well as the appropriate number of FCUs from the efficient and economical viewpoints. The required numbers of FCUs for surplus solar energy recovery were 8.4-10.9units and 6.1-8.0units based on air mass and circular flow rate that passed through the FCUs. Considering calculation methods and the risks such as efficiency and use environments of FCUs, it was found that about nine units (one unit per $24m^3$ approximately) needed to be installed. The required number of FCUs for surplus solar energy recovery was around one unit per $24m^3$ approximately.

• The Korean Journal of Applied Statistics
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• v.23 no.1
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• pp.139-150
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• 2010

In recent years, more generic drug products became available. The current regulation for assessing the bioequivalence of two drug formulations is based on the concept of average bioequivalence. This approach has been indicated to be insufficient for assessing switchability between two drug formulations and US FDA has adopted individual bioequivalence as one of the bioequivalence criterion since 2001. The US FDA recommends that individual bioequivalence be assessed based on $2\;{\times}\;4$ crossover design, while a $2\;{\times}\;3$ crossover design may be used as an alternative design to reduce the length and cost of the study. In this paper, a statistical procedure for assessment of individual bioequivalence under $3\;{\times}\;2$ crossover designs is proposed and some statistical points are discussed with $2\;{\times}\;3$ crossover design and $2\;{\times}\;3$ extra-reference design through simulation studies.