• Journal of information and communication convergence engineering
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• v.15 no.4
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• pp.199-204
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• 2017

A compact dual-band half-ring-shaped (HRS) bent slot antenna fed by a coplanar waveguide for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications is presented. The antenna consists of two HRS slots with different lengths and widths. The two HRS slots are connected through an arc-shaped slit, and the upper HRS slot is bent in order to reduce the size of the antenna. The optimized dual-band HRS bent slot antenna operating in the 2.45 GHz WLAN and 3.5 GHz WiMAX bands is fabricated on an FR4 substrate with dimensions of 30 mm by 30 mm. The slot length of the proposed dual-band slot antenna is reduced by 35%, compared to a conventional dual-band rectangular slot antenna. Experimental results show that the proposed antenna operates in the frequency bands of 2.40-2.49 GHz and 3.39-3.72 GHz for a voltage standing wave ratio of less than 2, and measured gain is larger than 1.4 dBi in the two bands.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.1
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• pp.115-122
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• 2021

In this paper, we propose a dynamic slot allocation scheme to improve the slot utilization rate in tactical multi-hop networks in which the channel condition varies due to node movements. The proposed scheme takes advantage of the fact that nodes that are more than three hops apart can use the same slot simultaneously. The frame is divided into two parts: the control period and the data period. To know the available slot information within two-hop distance, the node exchanges a slot allocation information with one-hop neighbors during the control period. The node can get the information on idle slots that are not used within two-hop distance but assigned already to other nodes that are more than three-hop away. The identified idle slot can be used by the node, which increases the slot utilization rate. The performance analysis results of the proposed scheme show that it increases the slot utilization rate sufficiently despite the overhead of the control period in the multi-hop networks of the future soldier system.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.226-228
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• 1998

PBMA_DP 프로토콜은 우선순위에 따른 수락 확률을 변화시켜준다. 수락 확률수치는 요구슬롯(R-slot)의 개수에 영향을 받는다. 따라서 부하가 많아지면 R-slot의 개수를 줄이고, 부하가 적어지면R-slot의 개수를 늘려 성능의 향상을 꾀할 수 있다. 따라서 본 논문에서는 동적으로 R-slot의 개수를 바꾸어주는 알고리즘 두 가지를 제안한다. R-slot위치는 고정시키고 개수만 변화시키는 방식과 R-slot 위치를 변화시키면서 개수도 변화시키는 방식이다. 또한 단말의 개수를 예측하는 방법에 대해 간단히 설명한다. 위의 두 방식에 대한 모의 실험을 시행하여 성능분석을 행한다.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.122-127
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• 2012

Post-wall waveguide structures have attracted a great deal of attention for micro- and millimeter-wave applications. One of the waveguide’s applications is a slotted waveguide array. In order to design the slotted array, the characteristics of a slot unit alone on the post-wall waveguide should be investigated. In this paper, a method for extracting the S-parameters of a unit slot is proposed. This simple method requires only two kinds of waveguides: waveguides without a slot unit and waveguides with a slot unit. Three kinds of slot units are fabricated, and the extracted results show a high level of agreement with predicted (simulated) results. With this method, the equivalent slot length can also be found.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.124-126
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• 2002

최근의 TDMA(Time Division Multiple Access) 알고리즘에 대한 발전 방향을 살펴보면 크게 두 가지로 요약할 수 있다. 먼저, 대용량의 데이터 - 멀티미디어 데이터 등 - 에 대한 활용이 많아짐에 따라 전송할 데이터를 적절하게 Scheduling하여 전송 효율을 증대시키는 접근 방향이 있으며, 또 다른 접근으로는 Time Slot에 대한 재사용성이나 Slot 할당 기법의 개선을 통하여 성능을 향상시키는 방법이 있다. 본 논문에서는 후자에 거론된 Time Slot에 대한 재사용성이나 Slot 할당 기법의 개선 방법 중의 하나인 STDMA(Self-organized TDMA)알고리즘에서, Slot 할당 시의 충돌 회피 방법을 고려하여 기존의 STDMA 알고리즘의 효율을 향상시키고자 한다. 현재 STDMA 알고리즘에서는 가용한 통신 범위 내에서의 Slot에 대한 할당 여부가 알고리즘 내에서 정의되고 있다. 따라서 부가적인 알고리즘의 추가가 없이 Slot할당 상황을 알 수 있으며, 이를 통하여 Slot 할당 단계에서 충돌 회피 방법을 추가하여 Conflict를 회피하도록 할 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.6
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• pp.668-676
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• 2017

A two-dimensional numerical investigation is performed to study the influence of slot width of multi-stage stationary floating overtopping wave energy devices on overtopping flow rate and performance. The hydraulic efficiency based on captured crest energy of different device layouts is compared with that of single-stage device to determine the effect of the geometrical design. The results show optimal trends giving a huge increase in overtopping energy. Plots of efficiency versus the relative slot width show that, for multi-stage devices, the greatest hydraulic efficiency is achieved at an intermediate value of the variable within the parametric range considered, relative slot width of 0.15 and 0.2 depending on design layouts. Moreover, an application of adaptive slot width of multi-stage device is investigated. The numerical results show that the overall hydraulic efficiency of non-adaptive and adaptive slot devices are approximately on par. The effect of adaptive slot width on performance can be negligible.

• Journal of Electrical Engineering and Technology
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• v.1 no.1
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• pp.85-91
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• 2006

Recently, the reduction of electromagnetic vibration and noise of a capacitor motor (CRM) has become a very important subject from the standpoint of environmental improvement. Therefore, the authors have studied the characteristics of the dominant electromagnetic vibration of the CRM under load condition. In this paper, the effects of slot combination and skewed slot on the dominant electromagnetic vibration of a CRM under load condition are discussed both theoretically and experimentally. As a result, the characteristics of the dominant electromagnetic vibration for the slot combination and the reduction effect of the skewed slot on the electromagnetic vibration are clarified for a 4-pole CRM.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.243-250
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• 2002

This paper designed a compact printed meandered scot antenna which to integrate in wireless LAN and proposed a printed dual meandered slot antenna for improving bandwidth. A printed dual meandered slot antenna is calculated by using the mehtod of FDTD. The calculated results showed good agreement with the measured results. As a result of measurement, the bandwidth(VSWR< 2) of single meandered slot antenna is 115 MHz and the bandwidth of dual meandered slot antenna is 164 MHz. The dual meandered slot antenna bandwidth has been improves to that of 43% comparing to single meandered slot antenna.

• Journal of Magnetics
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• v.21 no.1
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• pp.78-82
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• 2016

Cogging torque will affect the performance of a permanent magnet Brushless DC Motor (BLDCM), thus the reduction of cogging torque is key for BLDCM optimization. In this paper, the phase shifting of cogging torque for a fractional-slot concentrated winding BLDCM is analyzed using the Maxwell tensor method. Moreover, a 9-slot 10-pole concentrated winding BLDCM driven by ideal square waveform is studied with the finite element method (FEM). An effective method to reduce the cogging torque is obtained by adjusting the slot opening. In addition, the influences of different slot openings on back electromotive force (back-EMF), air gap flux density and flux linkage are investigated and experimentally validated using the prototype BLDCM.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.1
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• pp.1-8
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• 2001

This study deals with the experimental and numerical investigations to design the high performance otter board. Experiment was carried out to determine the most effective slot size of single-slot cambered otter board in the circulation water channel of BAEK KYUNG IND. Co. LTD. Numerical analysis was done by the commercial CFD code, FLUENT, to provide some valuable physical interpretations and finally to design the otter board section by numerical method. The major results are as follows ; 1. In experiment, the maximum lift and drag coefficients of simple cambered type otterboard were 1.41, 0.55, respectively, at the angle of attack $28^\circ$, while those of slot one with slot size 0.02C (C denotes the chord length) were 1.72, 0.42 at the angle of attack $24^\circ$. 2. The hydrodynamic characteristics depending upon slot size shows the greatest at 0.02C of the slot size. 3. Numerical results well visualized the streamlines, pressure fields, and speed vectors of a simple cambered and slot cambered otter board with slot size 0.02C. The slot cambered one with slot size 0.02C was shown that pressure field was distributed moderately on front and back side of otter board. And, the delay and decrease of separation were favorably achieved by flow through slot. 4. Computed result on the pattern of hydrodynamic field and the values of $C_L$ and $C_D$ by the commercial CFD code, FLUENT, show almost the same as those of the experimental result.