• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.803-814
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• 2022

The Lao government is continuously developing hydro-power dams in addition to the existing eight power plants in the Nam Ngum River basin and is expanding the power capacity of the existing power plants to meet the expected increase in electricity demand. Accordingly, the Lao government has requested an update on the existing reservoir operating rule curve in order to run the power plants efficiently. To this end, this study reviewed the current independent operating system as well as the joint operating system in order to maximize the annual power generation produced by a power plant by using CSUDP, general-purpose dynamic programming (DP) software. The appropriate operating regulation curve forms (URC/LRC, MRC) were extracted from the DP results, and the annual power generations were simulated by inputting them as the basic operating data of the reservoir operation set of the HEC-ResSim program. By synthesizing the amount of the annual power generation simulated, the existing operation regulation curve, the operational performance, and the opinion of the field operator, the optimal reservoir operation regulation curves that maximize the annual power generation of the target power plant were developed. Results revealed that a system operating in conjunction with the reservoir produces about 2.5 % more power generation than an independent reservoir due to the synergistic effect of the connection.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.11
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• pp.1066-1070
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• 2010

In wireless network, energy efficiency is an important design consideration for continuous multimedia streaming service. This paper proposes a new streaming system, called BACASS (Buffer-Aware and Content-Aware Streaming System) that working on the 802.11e U-APSD (Unscheduled Automatic Power Save). The BACASS leads the DP (Doze Period) of U-APSD for improving energy efficiency by utilizing the PSNR based on content-aware and client buffer occupancy that is hinged on a network-aware streaming system using SVC. The simulation results demonstrate the effectiveness of the proposed streaming system.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.69-72
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• 2003

The paper presents implementation of a PV fuzzy logic power tracking controller. Using maximum power point tracker with the intermediate converter can increase the system efficiency by matching the PV system to the load. A new fuzzy MPPT is proposed, where fuzzy inputs parameters are dp/dI and the last incremental of duty of duty ratio $L{\delta}D$, and the output is the new incremental value $(new{\delta}D)$ according to the maximum power point under various illumination levels.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.208-222
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• 2021

Managing with the presence of sea ice is the primary challenge in the operation of floating platforms in the Arctic region. It is widely accepted that offshore structures operating in Arctic conditions need station-keeping methods as well as ice management by icebreakers. Dynamic Positioning (DP) is one of the station-keeping methods that can provide mobility and flexibility in marine operations. The presence of sea ice generates complex external forces and moments acting on the vessel, which need to be counteracted by the DP system. In this paper, an icevaning control algorithm is proposed that enables Arctic offshore vessels to perform DP operations. The proposed icevaning control enables each vessel to be oriented toward the direction of the mean environmental force induced by ice drifting so as to improve the operational safety and reduce the overall thruster power consumption by having minimum external disturbances naturally. A mathematical model of an Arctic offshore vessel is summarized for the development of the new icevaning control algorithm. To determine the icevaning action of the Arctic offshore vessel without any measurements and estimation of ice conditions including ice drift, task and null space are defined in the vessel model, and the control law is formulated in the task space. A backstepping technique is utilized to handle the nonlinearity of the Arctic offshore vessel's dynamic model, and the Lyapunov stability theory is applied to guarantee the stability of the proposed icevaning control algorithm. Experiments are conducted in the ice tank of the Korea Research Institute of Ships and Ocean Engineering to demonstrate the feasibility of the proposed approach.

• Food Science and Preservation
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• v.23 no.7
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• pp.923-930
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• 2016

The purpose of this study was to improve the quality of the steamed rice cakes added with powder and extract of Schisandra chinensis (SC). Steamed rice cakes were prepared by adding SC using 1% hot-air dried SC powder (DP), hot-air dried SC extract (DE), freeze dried SC powder (FP) and, frozen SC extract (FE). After packaging with nylon/polyethylene films, the cakes were stored at $25^{\circ}C$ for 5 days. The FE-treated steamed rice cake had the lowest pH value. The $L^*$ value of the control cakes was highest immediately after processing and decreased during storage. The $a^*$ values of FP- and FE-treated steamed rice cakes were higher than those of DP- and DE-treated cakes. The $b^*$ values of DP- and DE-treated steamed rice cakes were higher than those of FP- and FE-treated cakes. Total phenolic contents of DP and DE were lower than those of FP and FE. Anthocyanin contents of DP- and DE-treated steamed rice cakes were lower than those of FP- and FE-treated cakes. Schisandrin contents of DP- and FP-treated steamed rice cakes were lower than those of DE- and FE-treated cakes. Ferric reducing antioxidant power assays revealed that DP and DE had lower antioxidant powers than those of FP and FE. The results of this study indicate that, among the treatments methods used, the steamed rice cake treated with FE had the highest functional component and antioxidant activity levels.

• Ocean Systems Engineering
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• v.3 no.4
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• pp.275-294
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• 2013

Side-by-side offloading operations are widely utilized in engineering practice. The hydrodynamic interactions between two vessels play a crucial role in safe operation. This study focuses on the coupled effects between two floating bodies positioned side-by-side as a shuttle tanker-FPSO (floating production, storage and offloading) system. Several wave directions with different side-by-side distances are studied in order to obtain the variation tendency of the horizontal hydrodynamic coefficients, motion responses and mean drift forces. It is obtained that the coupled hydrodynamics between two vessels is evidently distinguished from the single body case with shielding and exaggerating effects, especially for sway and yaw directions. The resonance frequency and the peak amplitude are closely related with side-by-side separation distance. In addition, the horizontal hydrodynamics of the shuttle tanker is more susceptible to coupled effects in beam waves. It is suggested to expand the gap distance reasonably in order to reduce the coupled drift forces effectively. Attention should also be paid to the second peaks caused by hydrodynamic coupling. Since the horizontal mean drift forces are the most mainly concerned forces to be counteracted in dynamic positioning (DP) system and mooring system, prudent prediction is beneficial in saving consumed power of DP system and reducing tension of mooring lines.

• Journal of Electrical Engineering and Technology
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• v.8 no.6
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• pp.1261-1268
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• 2013

This study proposes a voltage and reactive coordinative control strategy with distributed generator (DG) in a distribution power system. The aim is to determine the optimum dispatch schedules for an on-load tap changer (OLTC), distributed generator settings and all shunt capacitor switching on the load and DG generation profile in a day. The proposed method minimizes the real power losses and improves the voltage profile using squared deviations of bus voltages. The results indicate that the proposed method reduces the real losses and voltage fluctuations and improve receiving power factor. This paper proposes coordinated voltage and reactive power control methods that adjust optimal control values of capacitor banks, OLTC, and the AVR of DGs by using a voltage sensitivity factor (VSF) and dynamic programming (DP) with branch-and-bound (B&B) method. To avoid the computational burden, we try to limit the possible states to 24 stages by using a flexible searching space at each stage. Finally, we will show the effectiveness of the proposed method by using operational cost of real power losses and voltage deviation factor as evaluation index for a whole day in a power system with distributed generators.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.329-337
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• 2016

With the increasing deployment of distributed generators in the distribution system, a very large search space is required when dynamic programming (DP) is applied for the optimized dispatch schedules of voltage and reactive power controllers such as on-load tap changers, distributed generators, and shunt capacitors. This study proposes a new optimal voltage and reactive power scheduling method based on dynamic programming with a heuristic searching space reduction approach to reduce the computational burden. This algorithm is designed to determine optimum dispatch schedules based on power system day-ahead scheduling, with new control objectives that consider the reduction of active power losses and maintain the receiving power factor. In this work, to reduce the computational burden, an advanced voltage sensitivity index (AVSI) is adopted to reduce the number of load-flow calculations by estimating bus voltages. Moreover, the accumulated switching operation number up to the current stage is applied prior to the load-flow calculation module. The computational burden can be greatly reduced by using dynamic programming. Case studies were conducted using the IEEE 30-bus test systems and the simulation results indicate that the proposed method is more effective in terms of saving electric charges and improving the voltage profile than loss minimization.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.2
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• pp.61-70
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• 2012

Recently due to the increasing of the importance on the green energy is getting higher by implementing EERS(Energy Efficiency Resource Standards) and NA(Negotiated Agreement) such as lacks of natural resources and The United Nations Framework Convention on Climate Change. And the most practical solution is CHP(Combined Heat and Power) which performs the best energy efficiency. This paper developed optimal operation mechanism of CES(Community Energy System) for enhancement of energy efficiency using CHP(Combined Heat and Power), PLB(Peak Load Boiler) and ACC(ACCumulator) capacities. This method optimally operated these capacities calculated the maximum profits by Dynamic Programing. Through the case studies, it is verified that the proposed algorithm of can evaluate availability.

• Journal of Power System Engineering
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• v.19 no.2
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• pp.70-77
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• 2015

Nowadays, car manufacturers applied many high strength steels such AHSS or UHSS to car bodies for weight lightening. Therefore, a variety of applied steel sheet to car bodies increased and the needs of simulation to evaluate weldability also increased in order to reduce the cost and time. In this study, resistance spot welding simulations for DP 780 Steel with 1.0 and 1.4 mm thickness were conducted with respect to lobe curve. 2 regression models to estimate tensile shear strength were suggested and they were second order polynomial regression model and optimized second order regression model. The performance of these models was evaluated in terms of the coefficient of determinant and average error rate.