• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1674-1681
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• 2015

This paper presented an improved analytical method for calculating armature-reaction field in the surface-mounted permanent magnet machines accounting for opening slots. The analytical model is divided into two types of subdomains. The current of the armature is centralized in the center of the slots. The field solution of each subdomain is obtained by applying the interface and boundary conditions of the model. Two 30-pole/36-slot prototype machines with different slot-opening width are used for validation. The FE (finite element) results confirm the validity of the analytical results with the proposed model. The investigation shows that the wider the slot-opening width is, the smaller the peak value of radial and circumferential components of flux density, and the analytical armature-reaction field produced by centralized current in the slots is similar with the armature-reaction field produced by distributed current in the slots in the FE.

• 전자공학회논문지A
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• 제29A권11호
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• pp.1-13
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• 1992

In this DQDB networks, erasure nodes may be allocated on the bus and release slots which already had been read by destination nodes. An important function of the erasure node must be to eliminate as many requests as erased slots used by downstream nodes. In the networks with priorities, following two additional issues must be solved : (1) accurately to guess for which priority the erased slots is to be used, and (2) to find in a short period a request of that priority to cancel. In this paper, we propose two erasure node algorithms based on elimination of the requests. In these algorithms, the requests are eliminated excessively at low load but optimum elimination can be achieved at full load. Simulation results show that these two algorithms have similar access delay to that of existing algorithms at low load and better performance at high load.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.435-435
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• 2010

A inclined slot-excited plasma source is newly designed and constructed for higher flux HNB(Hyperthermal Neutral Beam) generation. The present source is different from the vertical SLAN(SLot ANtenna) sources [1] in two aspects. One is that the slots are inclined, and the other is that the magnetic field is configured to a cusp type. These modifications are intended to make the source plasma operated in sub-milli-torr pressure regime and as thin as possible, both of which is to get higher HNB flux by decreasing the re-ionization rate of the reflected atoms from the neutralizer [2]. The plasma is generated in a quartz tube of internal diameter 170 mm enclosed in a aluminum application chamber of larger diameter 250 mm. The microwave power is fed to the plasma chamber by 8 inclined slots cut into the application chamber wall. The slots are coupled the chamber to a WR280 waveguide wound around it to form a ring resonator. In order to make two slots $\lambda_g/2$ apart in phase, the adjacent slots are rotated in opposite directions. The rotation angle of the slots are set to $60^{\circ}$ from the chamber axis. Between the quartz chamber and the aluminum cylindrical chamber 8 NdFeB magnets are equally spaced and fixed to form the cusp magnetic field confinement and ECR (Electron Cyclotron Resonance) field. In this presentation, the magnetic and electromagnetic simulations, and the measured plasma parameters are given for both the inclined and the vertical slot-excited plasma sources. We also discuss how the sources can be tailored to suit better-performing HNB sources.

• Geomechanics and Engineering
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• 제8권4호
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• pp.495-510
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• 2015

The applications of water jet cutting (WJC) in coal mine have progressed slowly. In this paper, we analyzed the possibility and reasonableness of WJC application to pressure relief in hard coal seam, simulated the distributive characteristics of stress and energy fields suffered by hard coal roadway wallrock and the internal relationships of the fields to the instability due to WJC (including horizontal radial slot and vertical annular slot) on roadway wallrock. The results showed that: (1) WJC can unload hard coal seam effectively by inducing stress release and energy dissipation in coal mass near its slots; its annular slots also can block or weaken stress and energy transfer in coal mass; (2) the two slots may cause "the beam structure" and "the small pillar skeleton", and "the layered energy reservoir structure", respectively, which lead to the increase in stress concentration and energy accumulation in coal element mass near the slots; (3) the reasonable design and optimization of slots' positions and their combination not only can significantly reduce the scope of stress concentration and energy accumulation, but also destroy coal mass structure on a larger scale to force stress to transfer deeper coal mass.

• 한국ITS학회 논문지
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• 제13권1호
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• pp.61-66
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• 2014

본 논문에서는 LTE 700, GSM 850, GSM 900, GSM 1800, GSM 1900, UMTS 대역에서 동작 가능한 안테나를 설계 제작하였다. 작은 크기의 안테나로 광대역 특성을 얻기 위해 다중대역 모노폴 안테나를 기반으로 커플링 구조를 사용하였고 두 개의 slot을 삽입하여 hexa-band 대역폭 특성을 구현하였다. 시뮬레이션에 의한 최적화된 파라미터를 가지고 제작 하였고 제작된 안테나는 $VSWR{\leq}W3:1$에서 Low 주파수대역 410Hz 대역폭 (0.688-1.098GHz)과 High 주파수대역 643MHz 대역폭 (1.607-2.250GHz)이 측정되어 hexa-band(0.698-0.960GHz, 1.710-2.170GHz) 대역폭을 만족하고 높은 이득 (-0.52-4.68dBi) 및 전방향성 (Omni-directional) 방사 패턴을 얻었다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.546-550
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• 2003

For dual-band operation, it can be done by loading two pair of narrow slots in the equilateral-triangular patch, one embedded close to the side edges of the patch and the other inserted at the bottom edge of the patch. The obtained two operating frequencies are of same polarization planes. The frequency ratio of the two operating frequencies is turnabled by varing the positions and lengths of the inserted slots at the bottom edge of the patch. In this paper, A single-feed equilateral-triangular microstrip patch with two pairs of narrow slot for dual-frequency operation is printed on the substrate(TMN-4 Rosers Co.) of the 60 miles. the antenna radiation characteristics are calculated by Ensemble ver. 5.0 software, and compared with the experimental results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권2호
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• pp.511-527
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• 2024

This paper proposes a block-based self-organizing time-division multiple access (BSO-TDMA) protocol for very high frequency (VHF) data exchange system (VDES) in shipborne ad-hoc networks (SANETs). The BSO-TDMA reduces the collisions caused by the simultaneous transmission of automatic identification system (AIS) messages by uniformly allocating channel resources using a block-wise frame. For this purpose, the BSO-TDMA includes two functional operations: (1) frame configuration and (2) slot allocation. The first operation consists of block division and block selection. A frame is divided into multiple blocks, each consisting of fixed-size subblocks, by using the reporting interval (RI) of the ship. Then, the ship selects one of the subblocks within a block by considering the number of occupied slots for each subblock. The second operation allocates the slots within the selected subblock for transmitting AIS messages. First, one of the unoccupied slots within the selected subblock is allocated for the periodic transmission of position reports. Next, to transmit various types of AIS messages, an unoccupied slot is randomly selected from candidate slots located around the previously allocated slot. Experimental simulations are conducted to evaluate the performance of BSO-TDMA. The results show that BSO-TDMA has better performance than that of the existing SOTDMA.

• Journal of electromagnetic engineering and science
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• 제5권1호
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• pp.21-25
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• 2005

In this paper, a new method is suggested to improve the frequency responses of dual-mode waveguide-filters that employ cross-shaped slots. In accordance with this method, regarding one cross-shaped slot between two cavities, the horizontal(vertical) mode in one cavity can be designed to influence far less the vertical(horizontal) mode in cavity. Therefore, it improves the overall performances. A 4th-order dual-mode filter is taken as an example and it validates the method.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.166-170
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• 2007

This paper discusses stationkeeping of COMS which accommodates two optical payloads. In order to provide good quality images to the users, the east/west stationkeeping which is strong perturbing sources shall be performed outside of mandatory observation time slots asked by users. If the east/west stationkeeping time is resulted inside of the mandatory time slots, it shall be shifted in order to be performed outside of mandatory time slot, or a new stationkeeping shall be planned. This constraint is expected to ask additional fuel consumption in comparison with tradition stationkeeping. This paper analyzes the impact of mandatory time slots to the stationkeeping fuel consumption. Orbit simulations have been conducted to determine validity of given constraints in the light of fuel requirement and stationkeeping accuracy.

• Journal of electromagnetic engineering and science
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• 제11권3호
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• pp.207-212
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• 2011

This paper presents a CPW-fed antenna with three slots. The proposed antenna can operate at 1.9~2.1 GHz and 2.9~3.3 GHz which are generated by the two rectangular slots, and 4.5~11.6 GHz which is generated by the main patch. The semicircle-slot is used as a band-notched filter to stop at a desired band (5.150~5.825 GHz) limited by IEEE 802.11a or HIPERLAN/2 applications. The currents concentrate around corresponding slots at the desired band. The proposed antenna is very small in size, with overall dimensions of $27{\times}32{\times}1\;mm^3$ etched onto an FR4-printed circuit board (PCB).