• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.251-264
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• 2000

Organic removal from synthetic wastewater by electrochemical methods was investigated with various operating parameters, such as current density, retention time, electrode gap and $Cl^-/COD_{Cr}$ ratio. In electrolysis, dioxide iridium coated titanium ($IrO_2/Ti$) and stainless steel plate were used for anode and cathode respectively. The $COD_{Cr}$ removal efficiencies between plate type anode and net type anode were about same effect, but electrolytic power using net type anode is low than plate type anode. The $Cl^-/COD_{Cr}$ ratio was about $1.3kgCl^-/kgCOD_{Cr}$ when organic removal obtained 70 %, $Cl^-/COD_{Cr}$ ratio needs $2.2kgCl^-/kgCOD_{Cr}$ so as to organic completely remove. The removal efficiency of organics increased with current density, retention time and $Cl^-/COD_{Cr}$ ratio, but decreased with increasing electrode gap. The relationship of operating conditions and $COD_{Cr}$ removal efficiencies are as follows. $$COD_{Cr}(%)=80.0360(Current\;density)^{0.4451}{\times}(HRT)^{0.8102}{\times}(Gap)^{-0.4915}{\times}(Cl^-/COD_{Cr})^{0.5805}$$ There existed a competition between the removals for $COD_{Cr}$ and ammonium during electrolysis, the removal of ammonium was shown to be dominant and $COD_{Cr}$ removal was low. But $COD_{Cr}$ removal was raised as addition of alkalinity.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.2_1
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• pp.115-124
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• 2020

In wireless power transfer (WPT) system, the conventional compensation topologies only can provide a constant current (CC) or constant voltage (CV) output under their resonant conditions. It is difficult to meet the CC and CV hybrid charging requirements without any other schemes. In this study, a switching hybrid topology (SHT) is proposed for CC and CV electric vehicle (EV) battery charging. By utilizing an additional capacitor and two AC switches (ACSs), a double-side LCC (DS-LCC) and an inductor and double capacitors-series (LCC-S) topologies are combined. According to the specified CC and CV charging profile, the CC and CV charging modes can be flexibly converted by the two additional ACSs. In addition, zero phase angle (ZPA) also can be achieved in both charging modes. In this method, because the operating frequency is fixed, without using PWM control, and only a small number of devices are added, it has the benefits of low-cost, easy-controllability and high efficiency. A 3.3-kW experimental prototype is configured to verify the proposed switching hybrid charger. The maximum DC efficiencies (at 3.3-kW) of the proposed SHT is 92.58%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1789-1796
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• 2012

In this paper, a new high-efficiency CMOS bridge rectifier for driving RFID tag chips is designed and analyzed. The input stage of the proposed rectifier is designed as a cascade structure connected with two NMOSs for reducing the gate capacitance by circuitry method, which is the main path of the leakage current that is increased when the operating frequency is increased. This gate capacitance reduction technique using the cascade input stage for reducing the gate leakage current is presented theoretically. The output characteristics of the proposed rectifier are derived analytically using its high frequency small-signal equivalent circuit. For the general load resistance of $50K{\Omega}$, the proposed rectifier shows better power conversion efficiencies of 28.9% for 915MHz UHF (for ISO 18000 -6) and 15.3% for 2.45GHz microwave (for ISO 18000-4) than those of 26.3% and 26.8% for 915MHz, and 13.2% and 12.6% for 2.45GHz of compared other two existing rectifiers. Therefore, the proposed rectifier may be used as a general purpose rectifier to drive tag chips for various RFID systems.

• Current Photovoltaic Research
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• v.6 no.3
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• pp.74-80
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• 2018

Recently, perovskite solar cells have shown tremendous improvement in power conversion efficiencies. Moreover, they have potential in semitransparent solar cell applications due to their high absorption coefficients. In order to fabricate semitransparent perovskite solar cells with good performance, it is essential to consider the suitability of transparent electrode materials in various aspects, such as transparency, conductivity and fabrication process. In this review, candidate materials for transparent electrodes in perovskite solar cells including carbon-based nanomaterials, conductive polymers and metallic nanostructures are discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.300-304
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• 2015

This paper presents an omnidirectionally beam-steerable orthogonal loop resonator for wireless power transfer. The resonator is composed of two orthogonal loops. These connections of two loops and the current direction on the loops are determined by the control of switch. The magnetic field direction is determined by the vector sum of each loop current. The beam is steerable to eight directions by four switch modes. Using the suitable switch mode, the simulation and measurement efficiencies in the whole azimuthal direction are 56.3~60.0 %(deviation 3.7 %) and 41.2~48.7 %(deviation 7.5 %), respectively. The results show a little variation of transmission efficiency in the azimuthal direction.

• Journal of the Semiconductor & Display Technology
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• v.19 no.2
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• pp.55-59
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• 2020

Copper Oxide (CuO) films were deposited on the n-type silicon wafer by rf magnetron sputtering for heterojunction solar cells. And then the samples were treated as a function of the annealing temperature (300-600℃) in a vacuum. Their electrical, optical and structural properties of the fabricated heterojunction solar cells were then investigated and the power conversion efficiencies (PCE) of the fabricated p-type copper oxide/n-type Si heterojunction cells were measured using solar simulator. After being treated at temperature of 500℃, the solar cells with CuO film have PCE of 0.43%, Current density of 5.37mA/㎠, Fill Factor of 39.82%.

• Applied Chemistry for Engineering
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• v.33 no.4
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• pp.352-366
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• 2022

Nuclear power plant operations for electricity generation, rare-earth mining, nuclear medical research, and nuclear weapons reprocessing considerably increase radioactive waste, necessitating massive efforts to eradicate radioactive waste from aquatic environments. Cobalt (⁵⁸Co) and strontium (⁹⁰Sr) radioactive elements have been extensively employed in energy generation, nuclear weapon testing, and the manufacture of healthcare products. The erroneous discharge of these elements as pollutants into the aquatic system, radiation emissions, and long-term disposal is extremely detrimental to humans and aquatic biota. Numerous methods for treating radioactive waste-contaminated water have emerged, among which the adsorption process has been promoted for its efficacy in eliminating radioactive waste from aquatic habitats. The current review discusses the adsorptive removal of radioactive waste from aqueous solutions using low-cost adsorbents, such as graphene oxide, metal-organic frameworks, and inorganic metal oxides, as well as their composites. The chemical modification of adsorbents to increase their removal efficiency is also discussed. Finally, the current state of ⁵⁸Co and ⁹⁰Sr removal performances is summarized and the efficiencies of various adsorbents are compared.

• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.3
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• pp.241-255
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• 2012

Three types of 100 kW-class tidal stream turbines are proposed and their performance is studied both numerically and experimentally. Following a wind turbine design procedure, a base blade is derived and two additional blades are newly designed focusing more on efficiency and cavitation. For the three designed turbines, a CFD is performed by using FLUENT. The calculations predict that the newly designed turbines perform better than the base turbine and the tip vortex can be reduced with additional efficiency increase by adopting a tip rake. The performance of the turbines is tested in a towing tank with 700 mm models. The scale problem is carefully investigated and the measurements are compared with the CFD results. All the prediction from the CFD is supported by the model experiment with some quantitative discrepancy. The maximum efficiencies are 0.49 (CFD) and 0.45 (experiment) at TSR 5.17 for the turbine with a tip rake.

• Journal of Broadcast Engineering
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• v.18 no.6
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• pp.884-894
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• 2013

In this paper, we investigate the characteristics of power amplifiers and simplified memoryless non-linear power amplifier models for energy efficient communication system. First, we present the transfer function of GaAs FET (Gallium Arsenide Field Effect Transistor) that is widely used for high power amplifier. From those investigations, we introduce the instantaneous efficiencies and methods of amplification by assuming that the saturated current is constant, while perfect linearity is exploited under knee voltage. Then, we discuss four non-linear power amplifier models in a baseband signal processing. Finally, we explain the specified total power consumption model in a base station to achieve the resonable analysis for energy efficient communication.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.spc
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• pp.1-19
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• 2020

Based on the current high-level radioactive waste management basic plan and the analysis results of spent nuclear fuel characteristics, such as dimensions and decay heat, an improved geological disposal concept for spent nuclear fuel from domestic nuclear power plants was proposed in this study. To this end, disposal container concepts for spent nuclear fuel from two types of reactors, pressurized water reactor (PWR) and Canada deuterium uranium (CANDU), considering the dimensions and interim storage method, were derived. In addition, considering the cooling time of the spent nuclear fuel at the time of disposal, according to the current basic plan-based scenarios, the amount of decay heat capacity for a disposal container was determined. Furthermore, improved disposal concepts for each disposal container were proposed, and analyses were conducted to determine whether the design requirements for the temperature limit were satisfied. Then, the disposal efficiencies of these disposal concepts were compared with those of the existing disposal concepts. The results indicated that the disposal area was reduced by approximately 20%, and the disposal density was increased by more than 20%.