• Journal of electromagnetic engineering and science
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• v.10 no.4
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• pp.303-308
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• 2010

This paper proposes a method for improving the isolation characteristic of multi-input multi-output (MIMO) antennas using a split ring resonator (SRR) array structure between the two radiating elements. The fabricated antenna satisfies the 10 dB return loss requirement in the Mobile-WiMAX frequency band from 3.4 GHz to 3.6 GHz. The isolation between the two radiating elements is improved by approximately 20 dB at the center frequency by inserting a SRR array structure. The measured peak gains of the two elements are 2.3 dBi and 2.4 dBi, respectively.

• Journal of Ocean Engineering and Technology
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• v.25 no.2
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• pp.101-107
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• 2011

In view of the importance of material reduction because of the jump in oil and steel prices, structural design studies for lifting lugs were performed. Hundreds of thousands of such lifting lug structures are needed every year for ship construction. A direct design study was reviewed using the developed design system to increase the design efficiency and provide a way of directly inserting a designer's decisions into the design system process. In order to understand the design efficiency and convenience of a lug structure, parametric studies for prototype lug shapes were performed using the developed design system. From these design studies, various patterns of design parameters for the lug structure according to changes in the main plate length were examined. Based on these parametric study results, design guides were developed for more efficiently suggesting structural data for enormous lug structures. Additionally, a more detailed structural analysis through local strength evaluations will be performed to verify the efficiency of the optimum structural design for a lug structure.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.4
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• pp.335-343
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• 2012

As a matter of fact, it has been not allowed to modify the shape of a vehicle body skeleton since the technical definition for the structure was fixed and the corresponding molds were developed. By the way, if it is available to apply an alternative to reinforce the skeleton without changing its mold, it must be much flexible to improve the performance qualities relevant to not only NVH(noise, vibration and harshness) but also crash and durability. Recently, a solution of so-called composite body becomes available for the need. We present a design method to insert the composite body inside a vehicle body skeleton in order to improve a structure-borne noise at the idle condition. The algorithms, topology optimization and design sensitivity analysis, are applied to mainly search the sensitive structural sections in the body skeleton and to extract the target stiffness of the sections. Inserting the composite bodies into the sensitive portions, it is predicted to achieve the countermeasures which can compromize the design availability in terms of the idle noise and weight. According to the validation result with test vehicles, the concerned noise transfer function is reduced and the idle booming noise is resultantly improved.

• Special Issue of the Society of Naval Architects of Korea
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• 2009.09a
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• pp.93-96
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• 2009

Foundation structure for the main engine heavy spare parts in the engine room is susceptible to resonance problem due to outfitting weight. In addition the deck floor has a large opening for the main engine installation and maintenance, which further weakens the foundation structure. To reinforce the weak structure, two types of approaches have been used; 1) insert an H-pillar below or above the floor and 2) increase the stiffener size. In this paper, the H-pillar approach is used to solve the vibration problem of the foundation structure in the engine room opening area. A commercial program is used to analyze the vibration problem ad to find the location and the size of the H-pillar. Modal test at the quay and on-board vibration measurement during the sea trial have confirmed the validity of inserting an H-pillar below the floor.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.11
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• pp.1662-1667
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• 2012

This paper describes the design of size-reduced ring hybrid couplers (RHC) using a common defected ground structure (CDGS). The proposed RHC consists of double-sided microstrip line and the CDGS patterns which are placed in the common ground plane of the double-sided microstrip line. The effects of DGS as a periodic structure are imposed on both microstrip lines, so the advantages of the existing DGS are doubled. The normal RHC is designed first and folded by the half reference plane with the CDGS realized on the common ground plane. So another trial for size-reduction is performed by folding the RHC and inserting CDGS besides to the conventional DGS. In order to show a design example, a 2GHz RHC is designed and miniaturized using CDGS. The size of the miniaturized RHS is around 50% of the normal one, while the performances are well preserved even after the size-reduction.

• The Journal of the Acoustical Society of Korea
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• v.31 no.7
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• pp.472-479
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• 2012

This paper is aimed to design 9.2 kbps low bits late transform excitation coder that target to voice and audio signal. To set up low bit rate, we used Band-selection in frequency domain and gain-shape quantization and AbS structure. To decrease lots of calculation from ABS structure, we used each band IDFT and synthesis. And we designed non-transfer band for performance by inserting comfort noise. We propose coder that has low bit rate and similar performance comparing with original 10.4 kbps AMR-WB+ TCX mode.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1409-1420
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• 2015

In this paper, an algorithm using two bi-quad filters to suppress the wide-band resonance for PMSM servo systems is proposed. This algorithm is based on the double bi-quad filters structure, so it is named, "double bi-quad filter." The conventional single bi-quad filter method cannot suppress unexpected mechanical terms, which may lead to oscillations on the load side. A double bi-quad filter structure, which can cancel the effects of compliant coupling and suppress wide-band resonance, is realized by inserting a virtual filter after the motor speed output. In practical implementation, the proposed control structure is composed of two bi-quad filters on both the forward and feedback paths of the speed control loop. Both of them collectively complete the wide-band resonance suppression, and the filter on the feedback path can solve the oscillation on the load side. Meanwhile, with this approach, in certain cases, the servo system can be more robust than with the single bi-quad filter method. A step by step design procedure is provided for the proposed algorithm. Finally, its advantages are verified by theoretical analysis and experimental results.

• Journal of Ocean Engineering and Technology
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• v.23 no.2
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• pp.104-109
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• 2009

In the view of the importance of material reduction due to the jump in oil and steel prices, an optimized structural system for lifting lugs was developed. Such a system is needed hundreds of thousands of times a year. A direct design process was added to this developed optimized system to increase the design efficiency and provide a way of directly inserting a designer's decisions into the design system process. In order to verify the system efficiency and convenience, several new prototype lug shapes were suggested using the developed system. From these research results, it was found that the slope of the main plate of the lug structure has a tendency to move from about 45 degrees to about 60 degrees and the design weight was reduced from an initial value of about 32kgf to about $15{\sim}19kg_f$ after the redesign. Based on these initial research results, an efficient reduction in steel weight was expected considering the enormous consumption of lug structures per year. Additionally, a more detail structural analysis through local strength evaluations will be performed to verify the efficiency of the optimum structural design for a lug structure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1103-1108
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• 2010

This paper proposes a new type of PIFA with a capacitor structure inserted into the feeding loop. It operates in GSM900, DCS, PCS, and W-CDMA frequency bands. By inserting the capacitor, it shows the effect of lowering the return loss from -2.73 dB to -6.26 dB at the parallel frequency, 2.01 GHz. The improvement of the poor radiation property near the parallel resonance frequency leads to a broadband operation in the upper band, DCS, PCS, and W-CDMA.

• 한국기계연구소 소보
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• s.16
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• pp.127-136
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• 1986

Recently deck crane of multi purpose cargo vessel (MPCV) is designed to posi¬tion in side instead of in the center line of the upper deck with a view to reduce the transportation cost and shipbuilding cost by shortening the length of ship. In this paper, the crane post was at first designed according to the crane maker’s specification and parent ship and the structure is analysed with Finite Ele¬ment Method. Through the careful reviews on the result of analysis, the final design of crane post was modified. The crane post is designed as a cylindrical in upper part and hexagonal in lower part instead of cylindrical on the whole as before. The connecting part of crane post is designed with the form of mixture of the cylinderical and hexagonal. Since the center of cylindrical and hexagonal section are not on the same line, it is expected to have the stress concentration. So, in order to attenuate the concentrated stress on the connecting part, the upper and lower parts was stiffened by inserting plate to enlarge the area of welding. The structure of deck part includes the tank side floor which is depend on the lower structure of the crane post that would support the force of the crane post by placing with 1.5 frame interval of the vertical plate.