• Journal of KIISE:Information Networking
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• v.33 no.5
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• pp.395-406
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• 2006

In ad hoc networks, the limited battery capacity of nodes affects a lifetime of network Recently, a large variety of power-aware routing protocols have been proposed to improve an energy efficiency of ad hoc networks. Existing power-aware routing protocols basically consider the residual battery capacity and transmission power of nodes in route discovery process. This paper proposes a new power-aware routing protocol, TDPR(Traffic load & lifetime Deviation based Power-aware Routing protocol), that does not only consider residual battery capacity and transmission power, but also the traffic load of nodes and deviation among the lifetimes of nodes. It helps to extend the entire lifetime of network and to achieve load balancing. Simulations using ns-2[14] show the performance of the proposed routing protocol in terms of the load balancing of the entire network, the consumed energy capacity of nodes, and an path's reliability TDPR has maximum 72% dead nodes less than AODV[4], and maximum 58% dead nodes less than PSR[9]. And TDPR consumes residual energy capacity maximum 29% less than AODV, maximum 15% less than PSR. Error messages are sent maximum 38% less than PSR, and maximum 41% less than AODV.

• Progress in Medical Physics
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• v.17 no.4
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• pp.201-206
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• 2006

In this study, we have fabricated the noninvasive tube voltage meter which can observe the waveform of tube voltage and measure the tube voltage by using the Intensity of X-ray beam irradiated from radiotherapy simulator and also investigated the feasibility for clinical applications. Two pin photodiodes acting as X-ray detectors were arranged in parallel at the position of ${\pm}1.4cm$ in the y-axis of X-ray field and the aluminum filters with different thickness were placed above them. Using this detector, we could get the ratio ($r_{eff}$) of the relative output voltage which is proportional to the thickness of the filters. And the logarithm of effective peak tube voltage ($InkV_{p,eff}$) was obtained by Victoreen's NERO 6000M used as reference tube voltage meter. From the linear regression analysis of $r_{eff}$ and In $kV_{p,eff}$ the correlation coefficient (r) of linear equation was obtained to be 0.996 for the calibration of the tube voltage meter. Therefore, we suggest that the noninvasive tube voltage meter fabricated in this study can be used for clinical applications due to Its high accuracy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2164-2170
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• 2010

Digital Radio Frequency Memory, ( as DRFM ), is a device with the ability to restore output to the input RF signal in the required time after storing the incoming RF signals. Therefore DRFM is widely used in Jammer, EW Simulator, Target Echo Generator, and so on. This paper proposes its hardware implementation composed with the high frequency part and the digital processing part consisting of RF input/output module and local oscillator module. It is also proposed the replicated signal generation method which is consisted of the Analog-Digital conversion in the form of pulsed RF signal quantization, and FPGA to save and produce the playback signal, and RF signals to produce a Digital-Analog Conversion in the digital processing unit. This proposed scheme applied to test board and confirmed the validity of the proposed scheme through the test results obtained by the simulated input signals.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.4
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• pp.357-365
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• 2013

The 4 by 4 series slot sub-array antenna is proposed using substrate integrated waveguide(SIW) technology for 35 GHz of Ka band application. The proposed antenna is realized with multi-layered structure for compact size and easy integration features. 4 by 4 radiating slots are arrayed on top PCB with equal spacing and the feeding SIWs are arranged on middle and bottom PCBs for uniform power distribution. The multi-layered antenna is realized using RT/Duroid 5880 that has dielectric constant of 2.2 and the total antenna size is $750.76mm^2$. The individual parts such as radiators and feeding networks are simulated using full-wave simulator CST MWS. Furthermore, the total sub-array antenna also fabricated and measured the electrical performances such as impedance bandwidth under the criteria of -10 dB(490 MHz), maximum gain(18.02 dBi), sidelobe level(SLL)(-11.0 dB), and cross polarization discrimination (XPD)(-20.16 dB).

• Journal of Korean Society of Transportation
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• v.29 no.5
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• pp.67-78
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• 2011

This paper analyzes the characteristics of drivers' workload observed from with 30 participant drivers with respect to two physio-physiological parameters. For investigating physio-physiological characteristics of road drivers, bio-signals from brain's occipital lobe between simulation experiment and real driving experiment are collected and analyzed. The major findings from the analysis are summarized as follows: First, the drivers' physio-physiological workload is a good parameter for explaining the workload characteristics of road drivers. Secondly, the two physio-physiological workload parameters selected, i.e., beta value and relative energy parameter, are revealed to be statistically significant. Thirdly, it is also revealed to be statistically significant to select 90 percentile measurements in simulator experiment to explain the road drivers' characteristics. Finally, the maximum workload of road design driver is 31.72 in beta parameter, whereas the minimum workload is 1.296 in relative energy parameter.

• Journal of KIISE
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• v.43 no.2
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• pp.163-176
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• 2016

The contention overhead on the same channel in an NoC architecture can significantly increase a communication delay due to the simultaneous communication requests that occur. To reduce the overall overhead, we propose task-to-tile binding techniques for an NoC-based manycore platform, whereby it is assumed that the task mapping decision has already made. Since the NoC architecture may have multiple memory tiles as its size grows, memory clustering is used to balance the load of memory by making applications access different memory tiles. We assume that the information on the communication overhead of each application is known since it is specified in a dataflow task graph. Using this information, this paper proposes two heurisitics that perform binding of multiple tasks at once based on a proper memory clustering method. Experiments with an NoC simulator prove that the proposed heurisitic shows performance gains that are 25% greater than that of the previous binding heuristic.

• Journal of the Korean Society for Railway
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• v.20 no.4
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• pp.539-549
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• 2017

This paper proposes an analytical methodology of station capacity calculation on high - speed railway. Our method explicitly takes into account the effect of the number of sidings and the combination of train halting patterns (stop - stop, pass - stop, stop - pass, pass - pass) on the capacity of a station. To verify the reliability of our model, we conducted capacity analysis of selected stations using the Railsys simulator. We found that the difference in calculated capacity between our model and Railsys was less than 10%. After Monte Carlo simulation, our model was determined to be a good one. In addition, the consistency in capacity between our model and the train-path allocation program (Korea Rail Network Authority) was statistically significant.

• Journal of IKEEE
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• v.21 no.4
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• pp.338-347
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• 2017

This paper describes the design and fabrication of a high power amplifier which is a component of TDL(Tactical Data Link) aircraft terminal. We applied high-speed frequency hopping technology, cognitive radio technology, and receive filter bank technology to efficiently use limited frequency resources with radar and other communication equipment using the same frequency band. The high-power amplifier is physically composed of a transmitter, a receiver, a mechanical part, and a cable assembly, and is designed to meet temperature characteristics and electrical characteristics such as maximum transmission distance and reception sensitivity. Modeling and simulator were used to satisfy the requirement of high power amplifier. The transmit power and the noise figure were measured at 50.02dBm and 2.682dB, respectively. It was confirmed that all the required specifications were satisfied in the electrical characteristics test and the environmental characteristic test.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.5
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• pp.43-52
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• 2023

Traffic accidents among children have been decreasing after the installation of yellow carpets. However, the explanatory power of the causal relationship between yellow carpet installation and traffic accidents is still insufficient. The yellow carpet effect was analyzed in greater depth using virtual reality (VR) simulation experiments in various situation that could not be evaluated in existing actual vehicle research studies due to difficulties or risks in implementation. A target site where an actual yellow carpet was installed was selected and, implemented into a virtual environment. Subjects were made to, were gaze measurement equipment and ride the simulator. The visual/driving behavior before and after yellow carpet installation was compared, and a t-test analysis was performed for statistical verification. All the results were found to be statistically significant.

• The KIPS Transactions:PartD
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• v.9D no.5
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• pp.755-768
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• 2002

We investigate the effect of the data skew of join attributes on the performance of a pipelined multi-way hash join method, and propose two new hash join methods with load balancing capabilities. The first proposed method allocates buckets statically by round-robin fashion, and the second one allocates buckets adaptively via a frequency distribution. Using hash-based joins, multiple joins can be pipelined so that the early results from a join, before the whole join is completed, are sent to the next join processing without staying on disks. Unless the pipelining execution of multiple hash joins includes some load balancing mechanisms, the skew effect can severely deteriorate system performance. In this paper, we derive an execution model of the pipeline segment and a cost model, and develop a simulator for the study. As shown by our simulation with a wide range of parameters, join selectivities and sizes of relations deteriorate the system performance as the degree of data skew is larger. But the proposed method using a large number of buckets and a tuning technique can offer substantial robustness against a wide range of skew conditions.