• Explosives and Blasting
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• v.28 no.2
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• pp.50-58
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• 2010

This study explores the slot-drilling method that has not yet enough been studied in Korea and intends to provide a theoretical framework for putting the method into practice in a construction site. The possible reduction of ground vibration by implementing slot-drilling methods is addressed. Two main subjects dealt with include the variation of vibration velocity that is based on the distance between the slot-drilling and the epicenter of blasting and the analysis of appropriate effective dimension of slot-drilling width and height to control blasting vibration. This study shows that effect of vibration reduction decreases when distance of the slot-drilling and the epicenter of blasting is getting larger and also reveals that there is a correlation between the slot size and the vibration velocity at any point.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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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.

• Journal of electromagnetic engineering and science
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• v.17 no.2
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• pp.57-64
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• 2017

In this paper, an asymmetric compact multiband slot antenna is proposed for global positioning system (GPS), worldwide interoperability for microwave access (WiMAX), and wireless area network (WLAN) applications. The top plane, a ground is composed of a rectangular slot with a trapezoidal-like stub, an inverted U-shaped slot at the right side of the rectangular slot, an inverted L-shaped slot at the left side of the rectangular slot, and three stubs. The proposed antenna is fed by an asymmetric cross-parasitic strip on the bottom plane. By properly designing the slots and stubs, four resonant frequency bands are achieved with -10 dB reflection coefficient bandwidths of 50 MHz, 400 MHz, 390 MHz, and 830 MHz in the 1.57 GHz GPS band, 2.4 GHz WLAN band, 3.5 GHz WiMAX band, and 5.5 GHz WLAN bands, respectively. The antenna has a total compact size of $13mm{\times}32mm{\times}0.8mm$. Simulated and measured results indicate that the proposed antenna has sufficient bandwidth and good radiation performance in each band.

• ETRI Journal
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• v.31 no.5
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• pp.506-509
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• 2009

A novel design of a compact square-ring slot microstrip antenna for achieving circular polarization (CP) operation is proposed and experimentally studied. By using an arrow-shaped slot structure as a radiating element, the resonant frequency of the proposed antenna is significantly lowered, which can lead to a large size reduction for fixed frequency operation. The CP radiation characteristics are achieved by loading with proper asymmetry, which can be placed diagonally. A prototype of the proposed design is implemented and its performance is measured. Measured results show that radiation patterns with good CP characteristics are obtained at the resonant frequency.

• Journal of Advanced Navigation Technology
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• v.21 no.4
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• pp.353-358
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• 2017

In order to reduce the size of the previous stepped slot antenna for UWB applications(3.1 ~ 10.6 GHz) to half, an open ended stepped slot antenna is proposed. The proposed antenna consists of a stepped slot etched on the ground plane as radiation part and a microstrip feed-line with rectangular patch on the top plane for wideband impedance matching. The proposed antenna is designed and fabricated on the FR4 substrate with dielectric constant of 4.3, thickness of 1.6 mm and size of $28.5{\times}32mm^2$. The measured impedance bandwidth (${\mid}S_{11}{\mid}{\leq}-10dB$) of the fabricated antenna is 7.99 GHz(3.01~11 GHz) which is sufficient to cover UWB band (3.1 ~ 10.6 GHz). In particular, it has been observed that antenna has a good omnidirectional radiation patterns and high gain over the entire frequency band of interest even though the size of the proposed antenna is reduced to half when compared with the previous antenna.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.8 s.350
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• pp.103-109
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• 2006

In this paper, single-feed equilateral triangular microstrip antennas(ETMA) for circular polarization(CP) are designed and studied experimentally. It is demonstrated that by embedding a narrow slot or a cross of unequal slot lengths in the triangular patch circularly polarized radiation RHCP(right-hand circularly polarized wave), LHCP(left-hand circularly polarized wave) of microstrip antennas can easily be achieved using by strategically positioned coaxial single probe feed. And the size of a triangular microstrip patch antenna is smaller than that of a conventional rectangular or circular patch at a given frequency. A single-feed ETMA with a horizontal narrow slot is printed on the substrate of 60 mils thick and the other ETMA with a corss slot of unequal slot lengths is printed on the same substrate. The antenna radiation characteristics are calculated by ENSEMBLE(Ver. 5.0) software, and compared with the experimental results. This results show that the antenna size reduction of about $17%{\sim}2l%$ is obtained as compared to the regular-size CP design.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.3
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• pp.470-475
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• 2012

In Q-algorithm of EPCglobal Class-1 Gen-2 RFID system, the initial value of $Q_{fp}$, which is the slot-count parameter, is not defined in the standard. And the values of weight C, which is the parameter for incrementing or decrementing the slot-count size, are not determined. Therefore, if the number of tags is small and we let the initial $Q_{fp}$ be large, the number of empty slot will be large. On the other hand, if we let the initial $Q_{fp}$ be small in spite of many tags, almost all the slots will be collided. Also, if the reader selects an inappropriate weight, there are a lot of empty or collided slots. As a result, the performance will be declined because the frame size does not converge to the optimal point quickly during the query round. In this paper, we propose a scheme to allocate the optimal initial $Q_{fp}$ through the tag number estimation and select the weight based on the slot-count size of current query round.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.48-52
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• 1995

Chipping is an unavidable phenomean in the slot grinding process of hard and brittle materials. However,it should be reduced for the improvement of surface integrity in the manufacture of optical and semiconductor components. Electrolytic In-process Dressing (ELID) technique for metal bonded superabrasive grinding wheel has been developed for mirror surface grinding of hard and brittle materials. Electrically dressed wheel surface has sharply exposed abrasives and results in lower grinding force, higher grinding efficiency in grinding. The paper deals with a newly developed method for slot grinding using ELID and was implemented to improve grooved surface quality and decreases chipping size on the edge of the groove. As a result, we accomplished shipping-free grooves and obtained the clear ground sufaces on glass and tungsten carbide.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.773-781
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• 2000

We proposed an eccentric annular ring microstrip slot antenna for improving a narrow bandwidth of the conventional annular ring microstip slot antenna. The proposed antenna has an asymmetric slot and a normal microstrip feedline. This antenna is analyzed and optimized by using the finite difference time domain (FDTD) method. The impedance bandwidth of the optimized antenna is more than 1 octave that is much broader than the conventional annular ring microstrip slot antenna for the same size.

• Journal of electromagnetic engineering and science
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• v.5 no.3
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• pp.126-131
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• 2005

To increase the efficiency of an applicator during microwave hyperthermia therapy, first, the length from the antenna end to a slot is varied to get the optimal matching of the characteristic impedance at the frequency of 2.45 GHz. Using the electric and thermal constants of biological tissue, we compose a phantom to calculate temperature increment as well as the resonance characteristics and the SAR distributions. The proposed 3-slot sleeve antenna inserted in an applicator plays an effective role in increasing the therapy size in the view of heating performance as electromagnetic energy tends to concentrate on not feed point direction but treatment area. The SAR is then used in combination with a finite difference heat transfer equation to determine the temperature distribution. Also, in order to shorten treatment time and increase therapy size, a square-array structure is suggested and analyzed.