• Journal of Digital Convergence
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• v.12 no.11
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• pp.273-279
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• 2014

In this paper, we propose a novel algorithm for three dimensional positioning system and implement a system over indoor wireless channel. A commercial modules are used for mobile and fixed nodes which are product of German company Nanotron Co. This module adopts chirp spread spreading scheme as modulation method to improve the ranging resolution and the module satisfies the IEEE standard 802.15.4a. The distance computation is based on received signal strength(RSS) levels and trilateration method. A testbed was set up to measure and compare the positioning estimation error of the proposed algorithm. The experiments results showed that the accuracy of location estimation was sufficiently good as much as 1m distance error in a wireless environment in an office building.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.3
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• pp.9-18
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• 2007

The small and medium sized dams have the fill dam type of a lot of occasions, which are often weak in cases of major floods. For this reason, although a countermeasure is in great need, due to the importance of the facilities and financial situations, no direct safety measures have been taken. In this study, in order to minimize construction expenditure for practical safety measures in cases of major floods, the overflow section of spillway has been analyzed focusing on how the overflow capacity will increase in the case of partially rebuilding a part of the overflow section of spillway favorable for hydraulic conditions. The labyrinth weir and movable weir was chosen for reconstruction models of the overflow section. Moreover, for analyzing the after-effects of the reconstruction, a small scale dam was temporarily chosen for various experiments such as the hydraulic model testing and the three dimension numerical evaluation through the use of Flow-3D.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.1-7
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• 2011

In this work, an analytical models for the threshold voltage and flat band voltage have been suggested and proved using 3-dimensional device simulator. The method for device design guideline and its example in nanowire junctionless transistor and example of device design of was also presented. One can find that the suggested model for threshold voltage and flat band voltage agrees with 3-dimension simulation results. The threshold voltage and flat band voltage are decreased with the increase of nanowire radius, gate oxide thickness, and channel impurity doping concentration. When the work function of gate material and the ratio of ON and OFF current is given, the device design guide line for nanowire junctionless transistor has been proposed. It is known that the device with high impurity channel concentration can be fabricated with th decreased of nanowire radius and gate oxide thickness.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.444-451
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• 2017

In this paper, we have evaluated and analyzed OTFS(Orthogonal Time Frequency Space) modulation and OTFS-MIMO(Multiple Input Multiple Output) system. OTFS modulation can concisely compensate delay-Doppler spreading effect by using 2D(2-Dimension) iDFT (inverse Discrete Fourier Transform) and DFT(Discrete Fourier Transform) operation. It enables OTFS system to transmit high-speed data. Especially, OTFS-MIMO system can transmit all data streams without performance degradation on high Doppler frequency channel. As simulation results, we have confirmed that $1{\times}1$ OTFS system's achievable rate is a similar to each stream of $2{\times}2$ OTFS-MIMO system. That is, we have also confirmed that $2{\times}2$ MIMO system can completely achieve double achievable rate in comparison with OTFS system on high Doppler frequency channel.

• Journal of the Korean Institute of Telematics and Electronics
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• v.12 no.4
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• pp.28-34
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• 1975

텔레비젼 수신용 안테나로써 가장 널리 사용되고있는 Yagi안테나는 구조가 간단하고 지향성 이득등이 좋으나 방사주파수에 대한 반파장길이의 소자를 사용하므로 칫수가 커지고 주파수대역이 좁다. 따라서 설치 취급등에 불편을 느낄 경우가 많다. 한편 최근 일반적으로 아무곳에서나 용이하계 설치할 수 있을만큼 소형이면서 화질이 좋은 수상이 가능한 수신안테나에 대한 요망이 커지고 있는데 본 연구에서는 그 파장에 비해서 소형인 폴디드·다이폴 안테나 소자 2개를 좁은 간격으로 배열하고 이들을 이상결합하므로써 VHF텔레비젼전파의 고채널 주파수대에서 비교적 양한 단일지향성을 얻고 있다. 본 안테나에 능동소자를 이용한 저잡음광대역증폭기를 삽입한다면 다소자 Yagi안테나에 비나될 전후방비를 갖는위에 그의 이득도 크게 증가되어 일반수상안테나로 뿐만 아니라 고우스트 방지용실내안테나로서 상당한 기여틀 할것으로 생각된다. The Yagi antenna, which is most widely used for television receiving, has simple form and good directiyity as well as high gain, but it must be made with linear elements of half wave length. Therefore, the dimension of multi-element Yagi antenna becomes bulky and so a(ten it is inconvenient to install and handle, because of its big size. Moreover the frequency band width of the Yagi antenna is usually not broad enough to cover the total frequency range of VHF TV channels in our country. Recently, the aemand for an antenna which is not only small enough to install it easily anywhere but also assures good quality of pictures is generally increasing. In this study 2 elements o( folded dipole, which is small compared to its electrical ways length, are fixed parallel to each other with a narrow distance and the emfs induced in them are made to get together with some phase difference. This new phased array antenna has shown a relatively good unidirectivity through over the high channel VHF television frequency hand as well as the good PIB ratio which is comparable to that of multielements Yagi antenna. As a result this new antenna will be used as a VHF high channel TV receiving antenna and it may become better antighost antenna when used inside the room than other room antennas.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.51 no.9
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• pp.449-454
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• 2002

A rectangular straight microchannel, integrated with the resistance temperature detectors(RTDs) for temperature sensing and a micro-heater for generating the Temperature gradient along the channel, was fabricated. Its dimension is 57${\mu}{\textrm}{m}$(H)$\times$200${\mu}{\textrm}{m}$(W)$\times$48,050${\mu}{\textrm}{m}$(L), and RTDs were placed at the inner-channel wall. Si wafer was used as a substrate. For the fabrication of RTDs, 5300$\AA$ thick Pt/Ti layer was sputtered on a Pyrex glass wafer. Finally, the glass wafer was bonded with Si wafer by anodic bonding, so that the RTDs are located inside the microchannel. Temperature coefficient of resistance(TCR) values of the fabricated Pt-RTDs were 2800~2950ppm$^{\circ}C$ and the variation of TCR value In the range of O~10$0^{\circ}C$ was less than 0.3％. Therefore, it was proved that the fabricated Pt-RTDs without annealing were excellent as temperature sensors. The temperature distribution in the microchannel was investigated as a function of mass flow rate and heating power. The temperature increase rate diminished with decreasing the applied power and increasing the mass flow rate. It was confirmed from the comparison with the simulation results that the temperature measured inside the microchannel is more accurate than measuring the temperature measured at the outer wall. The proposed temperature sensing method and microchannel are expected to be useful in microfluidics researches.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.425-430
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• 2014

This paper analyzed the change of subthreshold current for gate oxide thickness of double gate(DG) MOSFET. Poisson's equation had been used to analyze the potential distribution in channel, and Gaussian function had been used as carrier distribution. The potential distribution was obtained as the analytical function of channel dimension, using the boundary condition. The subthreshold current had been analyzed for gate oxide thickness, and projected range and standard projected deviation of Gaussian function. Since this analytical potential model was verified in the previous papers, we used this model to analyze the subthreshold current. Resultly, analytical model showed that subthreshold current was influenced by parameters of Gaussian function and gate oxide thickness of DGMOSFET.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.1
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• pp.74-83
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• 1995

To estimate the parameters of a mathematical model of fishes' swimming behavior, the behavior in a experimental water tank was observed and analyzed using the video monitoring system. The tank was equipped with vertical circulation system, and measured $3,500L\;{\times}\;1,500B\;{\times}\;1,000H\;mm$ at flow channel and $1,200L\;{\times}\;900B\;{\times}\;500H\;mm$ at observational part. Rainbow trout, salmo gairdnerii were used as experimental fishes. Their swimming behavior in the tank was observed by the monitoring system, and the positions of every individual were checked at 0.5 second intervals by the image processing of recorded pictures for 5 minutes. The mean swimming speed calculated from the time series data of positions of every individual ranged from 2.5BL cm/sec to 2.9BL cm/sec at the stagnated flow. The mean swimming speed of 10 individuals in a school increased according to the flow speed. The mean swimming depth ranged from 17 cm to 38 cm even though it changed irregularly at the stagnated flow and gradually became stable according to the increase of flow speed. In the present study, the mean distance of individuals from wall of the tank varied from 17.6cm to 21.4cm. The mean distance between the nearest individual varied from 0.4BL cm to 0.7BL cm when 10 individuals in a school were observed. The mean dimension of fish schools became enlarged in all directions according to increase in the number of individuals, and as flow speed increased the horizontal dimension of fish schools expanded while their vertical dimension decreased.

• Water Engineering Research
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• v.2 no.4
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• pp.243-259
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• 2001

Local phenomena around bridge piers and abutments are generally considered to be similar, nevertheless the presence of the incoming boundary layer on the side wall in the abutment case generates extra pressure gradients and consequently a more complex vortex pattern. In the literature, experimental data for bridge abutments are relatively scarce; in particular almost no data are available for the time evolution of the scour. In this work we present the results of several long duration (3 days longrightarrow5weeks) clear water scour laboratory tests around bridge abutments; the time evolution of the erosion process is analysed with respect to local and global characteristic values (maxima, volume, hole shape). In particular we analyse the effect of the constriction ratio b/B between the transversal obstacle dimension and the flume width: in many practical situations abutments (or piers) obstruct a significant portion of the channel, so that the average acceleration due to constriction is expected to increase the scour effects of the local acceleration around the obstacle. Measured values for maximum scour are poorly predicted by literature formulas. Scour depths are positively correlated with the constriction ratio, but increases are smaller than expected from literature indications. Experimental results show that models for bridge piers cannot be directly applied to abutments; in particular, time scales for the latter are significantly larger than for piers.

• Journal of Information Technology Applications and Management
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• v.12 no.4
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• pp.93-104
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• 2005

Recently, RFID/USN is one of fundamental technologies in information and communications networks. Low-Rate WPAN, IEEE802.15.4 is a low-cost communication network that allows wireless connectivity in applications with limited Power and relaxed throughput requirements. Its applications are building automation, personal healthcare, industrial control, consumer electronics, and so on. Some applications require location information. Of course location awareness is useful to improve usability of data Low-Rate WPAN Is regarded as a key specification of the sensor network with the characteristics of wireless communication, computing, energy scavenging, self-networking, and etc. Unfortunately ZigBee alliance propose a lot of applications based on location aware technologies, but the specification and low-rate WPAN devices don't support anything about location-based services. RSSI ( Received Signal Strength indication) is for energy detection to associate, channel selection, and etc. RSSI is used to find the location of a potable device in WLAN. In this paper we studied indoor location awareness using vector matching of RSSI in low-Rate wireless PAN. We analyzed the characteristics of RSSI according to distance and experimented location awareness. We implemented sensor nodes with different shapes and configured the sensor network for the location awareness with 4 fixed nodes and a mobile node. We try to contribute developing location awareness method using RSSI in 3-dimension space.