• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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• pp.1492-1509
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• 2017

The wireless sensor network (WSN) is a key technology to support the Internet of things (IoT) paradigm. The efficiency of the MAC protocol in WSN is very important to take scalability with restricted wireless resources. The DESYNC-TDMA has an advantage of simple distributed slot allocation inspired by nature, but there is a critical disadvantage of split slots by firing message. The basic split slot model has less efficiency for continuous packet transmitting because of wasting of the slots less than the packet size. In this paper, we propose a firing offset adjustment scheme to improve the efficiency of slot utilizations, which can manage the slot assigned to each node as a single large block, called the single slot model. The performance analysis models for both the existing and the proposed schemes are also derived. Experimental results show that the proposed method provide better efficiency of slot utilization than the existing schemes without any loss of the nature of the desynchronization.

• ETRI Journal
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• 제23권1호
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• pp.33-38
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• 2001

A numerical simulation and an experimental implementation of T-shaped microstrip-fed printed slot array antenna are presented in this paper. The proposed antenna with relative permittivity 4.3 and thickness 1.0mm is analyzed by the finite-difference time-domain (FDTD) method. The dependence of design parameters on the bandwidth characteristics is investigated. The measured bandwidth of twin-slot array antenna is from 1.37 GHz to 2.388 GHz, which is approximately 53.9 % for return loss less than or equal to -10 dB. The bandwidth of twin-slot is about 1.06 % larger than that of single-slot antenna. The measured results are in good agreement with the FDTD results.

• 전기학회논문지
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• 제66권1호
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• pp.27-32
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• 2017

In this paper, slot less type high-speed and compact motor was designed. it was selected through change of stator coil distribution for the optimal performance of the motor. In this paper, designed motor was expected to be very vulnerable to heat dissipation in a compact motor. Therefore, to ensure reliability in the design result, winding and permanent magnet damage caused by the losses of motor was analyzed by thermal analysis and demagnetization analysis. Using the result, whether motor burnout was confirmed by motor performance degradation and insulation breakdown.

• Journal of Magnetics
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• 제15권3호
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• pp.103-107
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• 2010

We investigated spin-polarized current switching of Pac-man type II (PM-II) nanoelements in Pac-man shaped nanoscale spin-valves (Co/Cu/Py) using micromagnetic simulations. The effects of slot angle and antiferromagnetic (AFM) layer were simulated to obtain optimum switching in less than 2 ns. At a critical slot angle of $105^{\circ}$, the lowest current density for anti-parallel to parallel (AP-P) switching was observed due to no vortex or antivortex formation during the magnetic reversal process. All other slot angles for AP-P formed a vortex or antivortex during the magnetization reversal process. Additionally, a vortex or anti-vortex formed for all slot angles for parallel to anti-parallel (P-AP) switching. The addition of an AFM layer caused the current density to decrease significantly for AP-P and P-AP at slot angles less than $90^{\circ}$. However, at slot angles greater than $90^{\circ}$, the current density tended to decrease by less amounts or actually increased slightly as shape anisotropy became more dominant. This allowed ultra-fast switching with 5.05 and $5.65{\times}10^8\;A/cm^2$ current densities for AP-P and P-AP, respectively, at a slot angle of $105^{\circ}$.

• 한국산업보건학회지
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• 제3권2호
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• pp.204-212
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• 1993

This study was conducted to evaluate ventilation efficiency of 4-stage slot hood by variation of slot width, flow rate, hood size and baffle size. The slot velocity, control velocity and plenum velocity were related to slot width and the distance between source of contamination and hood. The results obtained from laboratory experiment for local exhaust ventilation systems were as follows ; 1. When slot widths were constant(equally changed) and the velocity was 6-10 m/s, the slot velocity from 1st slot to 4th slot gradually decreased. As the slot width-to-slot length ratio(WLR) decreased, the slot velocity of each stage increased. But if WLR value was less than 0.04, the slot velocity decreased. 2. When slot velocity exceeded 10 m/s with constant slot widths, the slot velocity of each stage was uniform. 3. When the slot velocity was uniform within 10 m/s and the first slot width was 14-20 mm, the slot width ratio between 1st slot and each of three other slots were 1, 1.25, 1.5 and 3.0, respectively. 4. The slot and plenum velocity were uniform when exhaust flow rate changed from 14 to $19m^3/min$ and there were no hood splitter vanes. 5. When the slot velocity at each stage was uniform, the control velocity at site 30 cm away from hood No.2 increased from 0.15-0.30 to 0.25-0.45 m/s and the control distance from 20 to 30 cm(about 1.5 times).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.9-12
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• 2003

Brushless do motors have been replacing brush type motors in machine tool and robotics applications over the last number of years This Paper deals with the design and application of the slot-less permanent magnet synchronous motor (PMSM). The slot-less PMSM eliminates rotational cogging torque due to permanent magnet preferred positions decreases core loss and thus increases efficiency, provides excellent torque-to-volume and power-to-volume ratios, and has a linear current versus torque relation. The PMSM with slot-less stator is designed and manufactured, which will be used for high speed and high efficiency application such a medical instruments.

• ETRI Journal
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• 제35권1호
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• pp.58-68
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• 2013

Five-phase reservation protocol (FPRP) is a contention-based media access control protocol for wireless ad hoc networks. FPRP uses a five-phase reservation process to establish slot assignments based on time division multiple access. It allows a node to reserve only one slot in an information frame. Once a node has reserved a slot, it will cease contending for other slots. As a result, there may be less contending nodes in the remaining slots, so the time slots in an information frame are not fully used by FPRP. To improve time slot utilization, this paper proposes an improved pseudo-Bayesian algorithm, based on which an improved contention access mechanism for FPRP is proposed, in which nodes are allowed to contend for more than one slot in a reservation frame according to a certain probability/priority. Simulation results indicate that the proposed mechanism performs better than FPRP in time slot utilization and hence the network throughput under various scenarios.

• Journal of electromagnetic engineering and science
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• 제2권1호
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• pp.50-55
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• 2002

In this paper, Ive propose a bow-tie-shaped meander slot antenna find by a microstrip line to achieve compact size as well as wideband characteristic. While conventional bow-tie slot antennas exhibit wide band characteristic, they have relatively large size. On the other hand, the meander slot antennas are very small, but they reveal quite narrow bandwidth (typically less than 1 %). To realize miniaturized antennas balling large bandwidth, combination of the bow-tie slot and the meander slot geometries is proposed in this paper. Theoretical results show that the proposed antenna with uniform slot width is 65.5 % smaller than that of the conventional bow-tie antenna in size, while the bandwidth is 3 times larger than that of the meander slot antenna. Moreover, the non-uniform slot width antenna shows 60 % smaller in size and about 3.5 times wider in bandwidth than the previous antennas. Measured antenna performance reveals excellent agreement with the predicted values.

• 대한수의학회지
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• 제60권3호
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• pp.139-144
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• 2020

Ten cadavers were studied to compare the accessibility of cervical vertebral canal with conventional standard ventral slot and modified slanted ventral slot. One group performed standard ventral slot procedures at the C3-4, C5-6. The other group performed modified slanted ventral slot with inverted cone technique procedures at the C3-4, C5-6 computed tomography was performed before and after surgery. The accessibility of cervical vertebral canal with conventional standard ventral slot and modified slanted ventral slot using computed tomography in C3-4 and C5-6 intervertebral space was compared. Although smaller ostectomy was performed in the modified slanted ventral slot, some lesions were more accessible but limitations were obvious in C3-4 and C5-6 intervertebral disk space. After the disc material has been identified through accurate preoperative diagnostic imaging, less morbidity and complications can be expected if the appropriate surgical method is selected based on the lesion of compression.

• Journal of information and communication convergence engineering
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• 제15권4호
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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.