• Progress in Superconductivity and Cryogenics
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• v.15 no.4
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• pp.26-29
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• 2013

Smart fault current controller (SFCC) proposed in our previous work consists of a power converter, a high temperature superconducting (HTS) DC reactor, thyristors, and a control unit [1]. SFCC can limit and control the current by adjusting firing angles of thyristors when a fault occurs. SFCC has complex structure because the HTS DC reactor generates the loss under AC. To use the DC reactor under AC, rectifier that consists of four thyristors is needed and it increases internal resistance of SFCC. For this reason, authors propose a hybrid type superconducting fault current limiter (SFCL). The hybrid type SFCL proposed in this paper consists of a non-inductive superconducting coil and two thyristors. To verify the feasibility of the proposed hybrid type SFCL, simulations about the interaction of the superconducting coil and thyristors are conducted when fault current flows in the superconducting coil. Authors expect that the hybrid type SFCL can control the magnitude of the fault current by adjusting the firing angles of thyristors after the superconducting coil limits the fault current at first peak.

• Smart Structures and Systems
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• v.3 no.4
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• pp.405-422
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• 2007

A new hybrid damping technique for vibration reduction in flexible structures, wherein a combination of layers of hard passive damping alloys and active (smart) magnetostrictive material is used to reduce vibrations, is proposed. While most conventional vibration control treatments are based exclusively on either passive or active based systems, this technique aims to combine the advantages of these systems and simultaneously, to overcome the inherent disadvantages in the individual systems. Two types of combined damping systems are idealized and studied here, viz., the Noninteractive system and the Interactive system. Frequency domain studies are carried out to investigate their performance. Finite element simulations using previously developed smart beam elements are carried out on typical metallic and laminated composite cantilever beams treated with hybrid damping. The influence of various parameters like excitation levels, frequency (mode) and control gain on the damping performance is investigated. It is shown that the proposed system could be used effectively to dampen the structural vibration over a wide frequency range. The interaction between the active and passive damping layers is brought out by a comparative study of the combined systems. Illustrative comparisons with 'only passive' and 'only active' damping schemes are also made. The influence and the mode dependence of control gain in a hybrid system is clearly illustrated. This study also demonstrates the significance and the exploitation of strain dependency of passive damping on the overall damping of the hybrid system. Further, the influence of the depthwise location of damping layers in laminated structures is also investigated.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.154-161
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• 2009

In order to implement continuous-path motion on a robot, it is necessary to blend one joint motion to another joint motion near a via point in a trapezoidal form of joint velocity. First, the velocity superposition using parametric interpolation is proposed. Hybrid motion blending is defined as the blending of different two type's motions such as blending of joint motion with linear motion, in the neighborhood of a via point. Second, hybrid motion blending algorithm is proposed based on velocity superposition using parametric interpolation. By using a 3-axis SCARA (Selective Compliance Assembly Robot Arm) robot with $LabVIEW^{(R)}$ $controller^{(1)}$, the velocity superposition algorithm using parametric interpolation is shown to result in less vibration, compared with PTP(Point- To-Point) motion and Kim's algorithm. Moreover, the hybrid motion $algorithm^{(2)}$ is implemented on the robot using $LabVIEW^{(R)(1)}$ programming, which is confirmed by showing the end-effector path of joint-linear hybrid motion.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.479-485
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• 2020

We evaluated the hatchability of fertilized eggs from six hybrid combinations of highly valued grouper species inhabiting temperate and warm waters, with the goal of establishing a novel hybrid with enhanced growth and viability during the culturing period in the temperate waters of Korea. Hybrid combinations with red-spotted grouper females exhibited high hatchability with high a fertilization and hatching rate of fertilized eggs and a low deformity rate of hatched larvae. Conversely, hybrid combinations with kelp grouper females had very low hatching rates and very high deformity rates; commercial production of seed from such crosses would be difficult without improving hatchability. The hatchabilities of convict grouper ♀×giant grouper ♂ and kelp grouper ♀×red-spotted grouper ♂ were lower than those of maternal purebreds, but these two hybrid combinations were expected to produce potentially large quantities of hatched larvae. In the above evaluation, promising hybrid combinations were identified for commercial production of seed. For these hybrids to contribute to the development of Korea's mariculture industry, mass production of fertilized eggs and seeds is necessary, along with the development of advanced rearing techniques, such as the identification of a suitable rearing temperature.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.288-296
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• 2009

In this study, the silica-based hybrid material with high barrier property was prepared by incorporating ethylene-vinyl alcohol (EVOH) copolymer, which has been utilized as packaging materials due to its superior gas permeation resistance, during sol-gel process. In preparation of this EVOH/$SiO_2$ hybrid coating materials, the (3-glycidoxy-propyl)-trimethoxysilane (GPTMS) as a silane coupling agent was employed to promote interfacial adhesion between organic and inorganic phases. As confirmed from FT-IR analysis, the physical interaction between two phases was improved due to the increased hydrogen bonding, resulting in homogeneous microstructure with dispersion of nano-sized silica particles. However, depending on the range of content of added silane coupling agent (GPTMS), micro-phase separated microstructure in the hybrid could be observed due to insufficient interfacial attraction or possibility of polymerization reaction of epoxide ring in GPTMS. The oxygen barrier property of the mono-layer coated BOPP (biaxially oriented polypropylene) film was examined for the hybrids containing various GPTMS contents. Consequently, it is revealed that GPTMS should be used in an optimum level of content to produce the high barrier EVOH/$SiO_2$ hybrid material with an improved optical transparency and homogeneous phase morphology.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.344-349
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• 2003

The purpose of this study is to ascertain the ability of New type cutter using Hybrid Rocket Propulsion System to cut normal carbon steel and also compound metal like stainless steel which cannot be cut by regular oxygen-acetylene cutter. To compare cutting performance, Two different types of experiment with oxygen-acetylene and Hybrid Combustion cutters were performed. As a result, Hybrid Combustion cutter is used to cut both carbon steel and stainless steel with cutting speed of 400mm/min(carbon steel) and 250mm/min(stainless steel). Otherwise, oxygen-acetylene cutter can be used to cut only carbon steel with cutting speed of 500 $^{\sim}$ 700mm/min. The possibility of Hybrid Combustion cutter as a cutting machine was confirmed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.535-544
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• 1988

In this paper, the hybrid ARQ scheme, which is incorporated the selective-repeat ARQ system with the finite receiver buffer and the single-error-correcting and double-error-detecting(63.56) cyclic Hamming code system, has been investigated. As a result of simulation, the proposed hybrid ARQ scheme shows that that throughput efficiencies are improved by one error correction, and that the reversed codewords due to retransmission are delivered to the user in order by means of detecting two errors. The hybrid ARQ scheme significantly outperforms the FEC or the ideal selective-repeat ARQ system in the respect of throughput and reliability, especially when the channel error rate is approximately in the range from $10^{-2}$~$10^{-3}$.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.10
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• pp.97-107
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• 2009

Recent technologies of the car are focused on improving vehicle's fuel efficiency and developing alternative energy sources. These technologies bring on the development of hybrid car. On the other hand, because of short driving distance, low efficiency of charging and high price, energy storage system need to improve the storage capability. It is very important to understand the existing technologies, grasp the existing patent and establish the technical target to improve the energy storage system. In this paper, technology trends of energy storage system of the hybrid car are analyzed. This study was based on the applied and registered patent in Korea, Japan, U.S.A and Europe until December 2008. The analyses are divided into two categories: a battery system and charging system of the hybrid car. The facts of the level of technology, trends of the R&D of leading companies, key patents, blank of the technology were analyzed. Finally the future R&D strategy of hybrid car are established.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.631-636
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• 2018

This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.1
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• pp.33-40
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• 2000

In this paper, an integrated method for the path planning and motion control of wheeled mobile robots using a hybrid system model and control is presented. The hybrid model including the continuous dynamics and discrete dynamics with the continuous and discrete state vector is derived for a two wheel driven mobile robot. The architecture of the hybrid control system for real time path planning and following is designed which has the 3-layered hierarchical structure : the discrete event system using the digital automata as the higher process, the continuous state system for the wheel velocity controls as the lower process, and the interface system as the interaction process between the continuous system as the low level and the discrete event system as the high level. The reference motion commands for autonomous navigation are generated by the abstracted motion in the discrete event system. The motion control tasks including the feasible path planning and autonomous motion control with various initial conditions are investigated as the applications by the simulation studies.