• Journal of the Korean Solar Energy Society
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• v.21 no.2
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• pp.1-8
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• 2001

The most effective methods for utilizing solar energy are to use the sunlight and solar thermal energy such as hybrid panel simultaneously and to use concentrator. From such a view point systems using various kinds of photovoltaic panels are constructed in the world. However, there has not been a hybrid panel with a concentrator. If the sunlight is concentrated on solar cell, cell conversion efficiency increases and the temperature of the solar cell s increases. As the temperature of the solar cells increases, the cell conversion efficiency gradually decreases. For maintaining the cell conversion efficiency constant, it is necessary to keep solar cell at low temperature. In this paper, after designing a concentration rate for concentrating, we propose a model for cooling the cell and for using wasted heat. And, we compare it with conventional panels after calculating the electrical and thermal efficiency, using the energy balance equation.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.690-693
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• 2005

In this paper, a hybrid PD-servo state feedback control algorithm for swing up inverted pendulum system is proposed. It consists of two parts. The first part is the PD position control for swinging up the pendulum from the natural pendent position to around the upright position and the second part is the servo state feedback control for stabilizing the inverted pendulum in upright position. The first controller is PD controller and it is tuned to control the position of the pendulum by moving the cart back and forth until the pendulum swings up around the upright position. Then the second controller will be switched to stabilize the inverted pendulum in its upright position. The controller in this stage is the servo state feedback controller designed by pole placement. Experimental results of PD type swinging up control system, of stabilizing servo state feedback control system and of the proposed hybrid PD-servo state feedback control system to swing up and stabilize inverted pendulum show that the proposed method is effective and reliable for actual implementation while it is simple.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1039-1043
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• 2005

Despite the many significant advances made in robot architecture, the basic approaches are deliberative and reactive methods. They are quite different in recognizing outer environment and inner operating mechanism. For this reason, they have almost opposite characteristics. Later, researchers integrate these two approaches into hybrid architecture. In such architecture, Reactive module also called low-level motion control module have advantage in real-time reacting and sensing outer environment; Deliberative module also called high-level task planning module is good at planning task using world knowledge, reasoning and intelligent computing. This paper presents a framework of the integrated planning and control for mobile robot navigation. Unlike the existing hybrid architecture, it learns topological map from the world map by using MST (Minimum Spanning Tree)-based SOFM (Self-Organizing Feature Map) algorithm. High-level planning module plans simple tasks to low-level control module and low-level control module feedbacks the environment information to high-level planning module. This method allows for a tight integration between high-level and low-level modules, which provide real-time performance and strong adaptability and reactivity to outer environment and its unforeseen changes. This proposed framework is verified by simulation.

• Advances in nano research
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• v.2 no.1
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• pp.23-56
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• 2014

The significant growth of the Si photovoltaic industry has been so far limited due to the high cost of the Si photovoltaic system. In this regard, the most expensive factors are the intrinsic cost of silicon material and the Si solar cell fabrication processes. Conventional Si solar cells have p-n junctions inside for an efficient extraction of light-generated charge carriers. However, the p-n junction is normally formed through very expensive processes requiring very high temperature (${\sim}1000^{\circ}C$). Therefore, several systems are currently under study to form heterojunctions at low temperatures. Among them, carbon nanotube (CNT)/Si hybrid solar cells are very promising, with power conversion efficiency up to 15%. In these cells, the p-type Si layer is replaced by a semitransparent CNT film deposited at room temperature on the n-doped Si wafer, thus giving rise to an overall reduction of the total Si thickness and to the fabrication of a device with cheaper methods at low temperatures. In particular, the CNT film coating the Si wafer acts as a conductive electrode for charge carrier collection and establishes a built-in voltage for separating photocarriers. Moreover, due to the CNT film optical semitransparency, most of the incoming light is absorbed in Si; thus the efficiency of the CNT/Si device is in principle comparable to that of a conventional Si one. In this paper an overview of several factors at the basis of this device operation and of the suggested improvements to its architecture is given. In addition, still open physical/technological issues are also addressed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.6
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• pp.187-193
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• 2013

In multi-agent systems, How to coordinate the behaviors of the agents through learning is a very important problem. The most important problems in the multi-agent system are to accomplish a goal through the efficient coordination of several agents and to prevent collision with other agents. In this paper, we propose a novel approach by using hybrid learning strategy. It is used hybrid learning strategy to control the multi-agent system efficiently by using the spatial relationship among the agents. Through experiments, we can see approximate faster the goal then other strategies and avoids collision among the agents.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.131-140
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• 2018

A broadcast scheduling scheme is an essential technique to improve the performance of data broadcast systems. This paper explores the problem of data broadcast over multiple channels to reduce query response time, and proposes a new hybrid data broadcast scheduling scheme named HDAMA. The proposed scheme employs the strategy that combines the advantages of push-based broadcast and pull-based broadcast. HDAMA could enhance the performance of query response time since it is capable of controlling the influence of access probability properly reflecting the characteristics of multi-data queries and broadcasting pull data items relatively on time. Simulation is performed to evaluate the performance of the proposed scheme. The simulation results show that the performance of HDAMA is superior to other schemes in terms of the average response time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.7
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• pp.467-476
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• 2014

Recently, various services which use the fused form of broadcasting and communication are being offered over the Internet globally. To provide various interactive services through connected smart TV on wired or wireless network, the seamless multimedia service is key feature. In this paper, Dynamic Adaptive Streaming over HTTP (DASH)is adopted to develop cost-effective adaptive streaming system for Open Hybrid TV(OHTV) service. This system can provide seamless adaptive streaming service for IP VOD, Video Clips, Ad insertion which are defined in OHTV.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.4
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• pp.281-291
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• 2017

Nowadays, as traffic jams are a daily elementary problem in both developed and developing countries, systems to monitor, predict, and detect traffic conditions are playing an important role in research fields. Comparing them, researchers have been trying to solve problems by applying many kinds of technologies, especially roadside sensors, which still have some issues, and for that reason, any one particular method by itself could not generate sufficient traffic prediction results. However, these sensors have some issues that are not useful for research. Therefore, it may not be best to use them as stand-alone methods for a traffic prediction system. On that note, this paper mainly focuses on predicting traffic conditions based on a hybrid prediction approach, which stands on accuracy comparison of three prediction models: multinomial logistic regression, decision trees, and support vector machine (SVM) classifiers. This is aimed at selecting the most suitable approach by means of integrating proficiencies from these approaches. It was also experimentally confirmed, with test cases and simulations that showed the performance of this hybrid method is more effective than individual methods.

• Composites Research
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• v.29 no.4
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• pp.138-144
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• 2016

Recently, electromagnetic interference (EMI) shielding materials have been extensively developed and significantly considered to protect electronic systems from harmful electromagnetic waves. Although, metal-based materials show high electrical conductivity and EMI shielding effectiveness, they have several challenging problems such as high density and corrosion. Carbon-based materials have been acclaimed as alternative EMI materials due to light weight, high mechanical properties, resistance to corrosion and excellent electrical conductivity. Here, we introduce 1-phase and 2-phase carbon materials as well as 3-phase hybrid carbon materials. The 3-phase hybrid carbon materials composed of metal nanoparticles, carbon nanotubes and graphene can be used as a promising EMI shielding material.

• Smart Structures and Systems
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• v.22 no.2
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• pp.139-150
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• 2018

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to expand the operational range of a regular generator through a simple and robust active control strategy. It has a broad range of applications in hybrid vehicles, wind turbines, water turbines, and similar technologies. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with an active control system, which adjusts the overlap ratio based on the desired output power at different rotor speeds for a specific application, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator results in reduced torque loss of the generator and an increased rotational speed of the generator rotor. A VEG can improve the fuel efficiency of hybrid vehicles; it can also expand operational ranges of wind turbines and water turbines and harness more power.