• Journal of the Korean Association of Geographic Information Studies
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• v.2 no.1
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• pp.12-31
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• 1999

Topex/Poseidon satellite altimetric data are used to estimate characteristics on the oceanic and atmospheric correction factors, and the mean sea level and its variations in the Yellow Sea, the East China Sea and the East Sea from September 1992 through August 1994(70cycles). For the atmospheric correction factors, the variations of dry troposphere, humid troposphere, ionosphere and inverted barometer were very small as a few centimeters, but the variations of electromagnetic bias were higher than other factors. For the oceanic correction factors, the variations of ocean tide(35cm in track 127 and 60cm in track 214) showed high ranges compared to elastic tide(5cm in track 127 and 1cm in track 214) and loading tide(1.8cm in track 127 and 1cm in track 214). It should be understood that the variations of ocean free surface is mainly under the influence of, firstly, ocean tide and, secondly, electromagnetic bias. Mean sea level in the Yellow Sea are higher than in the rest of Seas. Then its range generally comprised between -60cm and 210cm with mean value of about 100cm. Also its variations showed high values in the Yellow Sea and East China Sea, especially 5.689cm in Youngampo. This result is mainly due to the effects of local topography and tidal current.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.796-804
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• 2010

It is important to use the comb type pilot allocation for the continuous channel and efficient processing. And DFT-spreading OFDM is used a lot to solve high PAPR problem of OFDM system. However, PAPR is increased again when comb type pilot is used to estimate channel characteristics. So, in this paper, we employ a new SLM method to DFT-spreading OFDM system to reduce increased high PAPR. And we suggest an effective method to transmit side information without additional bandwidth. Pilot and side information must be preserved from jamming or intentional interferences since those are very important in DFT spread OFDM system using SLM. So, in this paper, we like to analyze and simulate the performance of DFT spread OFDM system based on SLM against jamming signal. To remedy the vulnerable shortcomings of DFT spread OFDM about jamming or intentional interferences, we employ FH(Frequency Hopping) method and analyze system performance under the several jamming conditions such as MTJ(Multi Tone Jamming) and PBJ(Partial Band Jamming).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.588-594
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• 2015

Although GPS technology for location positioning system has been widely used, it is difficult to be used in intelligent transport systems, due to the large positioning error and limited area for receiving radio signals. Thanks to the rapid development of LED technology, LED lights become popular in many applications. Especially, visible light communications (VLC) has raised a lot of interests because of the simultaneous functioning of LED illumination and communication. Recent studies on positioning system using VLC mainly focused on indoor environments and still difficult to satisfy positioning accuracy and simple implementation simultaneously. In this paper, we propose a positioning system based on VLC using the coordinate information of LEDs installed on the road infrastructure. Extracting the LED signal, obtained through VLC, from the easily accessible camera image, it is possible to estimate the position of the car on the road. Simulation results show that the proposed scheme can achieve a high positioning accuracy of 1 m when large number of pixels is utilized and the distance from the LED light is close.

• Journal of Biosystems Engineering
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• v.26 no.5
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• pp.461-468
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• 2001

Impact between fruits and other materials is a major cause of product damage in harvesting and handling systems. The oriental pears are more susceptible to bruising than other fruits such as European pears and apples, and are required more careful handling. The interest in the handling of the pears for the processing systems has raised the question of the allowable drop height to which pears can be dropped without causing objectionable damage. Drop tests on pears were conducted using an impact device developed by authors to estimate the allowable drop height without bruising. The impact device was constructed to hold in a selected orientation and to release a fruit by vacuum for dropping on to a force transducer. The drop height was adjustable for zero to 60 cm to achieve the desired distance between the bottom of the fruits and the top of the impact force transducer. The transducer was secured to 150 kg$\sub$f/ concrete block. The transducer signal was sampled every 0.17 ms with a strain gage measurement board in the micro computer where it was digitaly stored for later analysis. The selected sample fruit was Niitaka cultivar of pears which is one of the most promising fruit for export in Korea. The pears were harvested during the 1998 harvest season from an orchard in Daejeon. The sample fruit was selected from two groups which were stored for 3 months and 5 months respectively by the method of current commercial practice. The pears were allowed to stabilize at environmental condition(18$^{\circ}C$, 65% rh) of the experimental room. One hundred fifty six pears were tested from the heights of 5, 7.5. 10 and 12.5 cm while measurement were made of impact peak force, contact time, time to peak force, dwell time, pear diameter and mass. The bioyield strength and modulus of elasticity were measured using UTM immediately after each drop test. The allowable drop height was estimated on the base of bioyield strength of the pears in two ways. One was assumed the peak force during impact test increasing linearly with time, and the other was based on the actual drop test results. The computer program was developed for measuring the impact characteristics of the pears and analyzing the data obtained in the study. The peak force increased while contact times decreased with increasing drop height and contact times of the sample from the hard tissue group. The allowable drop height increased with increasing bioyield strength and contact times, and also varied with Poisson\`s ratio, mass and equilibrium radius of the pears. The allowable drop height calculated by a theoretical method was in the range from 1 to 4 cm, meanwhile, the estimated drop height considering the result of the impact test was in the range from 1 to 6 cm. Since the physical properties of fruits affected significantly the allowable drop height, the physical properties of the fruits should be considered when estimating the allowable drop height.

• Journal of Broadcast Engineering
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• v.13 no.1
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• pp.174-184
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• 2008

Complementary color filter array (CCFA) is widely used in consumer-level digital video cameras, since it not only has high sensitivity and good signal-to-noise ratio in low-light condition but also is compatible with the interlaced scanning used in broadcast systems. However, the full-color images obtained from CCFA suffer from the color artifacts such as false color and zipper effects. These artifacts can be removed with edge-adaptive demosaicking (ECD) approaches which are generally used in rrimary color filter array (PCFA). Unfortunately, the unique array pattern of CCFA makes it difficult that CCFA adopts ECD approaches. Therefore, to apply ECD approaches suitable for CCFA to demosaicking is one of the major issues to reconstruct the full-color images. In this paper, we propose a new ECD algorithm for CCFA. To estimate an edge direction precisely and enhance the quality of the reconstructed image, a function of spatial variances is used as a weight, and new color conversion matrices are presented for considering various edge directions. Experimental results indicate that the proposed algorithm outperforms the conventional method with respect to both objective and subjective criteria.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.119-128
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• 1998

This paper describes a filtering algorithm which employs apriori information of SPECT lesion detectability potential for the filtering of degraded projection images prior to the backprojection reconstruction. In this algorithm, we determined m minimum detectable lesion sized(MDLSs) by assuming m object contrasts uniformly-chosen in the range of 0.0-1.0, based on a signal/noise model which provides the capability potential of SPECT in terms of physical factors. A best estimate of given projection image is attempted as a weighted combination of the subimages from m optimal filters whose design is focused on maximizing the local S/N ratios for the MDLS-lesions. These subimages show relatively larger resolution recovery effect and relatively smaller noise reduction effect with the decreased MDLS, and the weighting on each subimage was controlled by the difference between the subimage and the maximum-resolution-recovered projection image. The proposed filtering algoritym was tested on SPECT image reconstruction problems, and produced good results. Especially, this algorithm showed the adaptive effect that approximately averages the filter outputs in homogeneous areas and sensitively depends on each filter strength on contrast preserving/enhancing in textured lesion areas of the reconstructed image.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2523-2529
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• 2014

Location estimation service can be provided outdoors using various location estimation system based on GPS. However, location estimation system is based on existing indoor resources as GPS cannot be used because of insufficient visible satellites and weak signals. The fingerprinting technique that uses WLAN signal, in particular, is good to use indoors because it uses RSSI provided by AP to estimate location. However, its accuracy may vary depending on how accurate data the offline stage used where the fingerprinting map is built. The study sampled various data at the stage that builds the fingerprinting map and suggested a location estimation system that enhances its precision by saving the data of high frequency among them to improve this problem. The suggested location estimation system based on majority sampling data estimates location by filtering RSSI data of the highest frequency at the client and server to be saved at a map, building the map and measuring a similar distance. As a result of the test, the location estimation precision stood at minimum 87.5 % and maximum 90.4% with the margin of error at minimum 0.25 to 2.72m.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.112-121
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• 2020

In suspension bridges, hanger cables are the main load-supporting members. The tension of the hanger cables of a suspension bridge is a very important parameter for assessing the integrity and safety of the bridge. In general, indirect methods are used to measure the tension of the hanger cables of a suspension bridge in traffic use. A representative indirect method is the vibration method, which extracts modal frequencies from the cables' responses and then measures the cable tension using the cables' geometric conditions and the modal frequencies. In this study, the image processing technique is applied to facilitate the estimation of the dynamic responses of the cables using the image signal, for which a portable digital camcorder was used due to its convenience and cost-efficiency. Ambient vibration tests were conducted on a suspension bridge in traffic use to verify the validity of the back analysis method, which can estimate the tension of remote hanger cables using the modal frequencies as a parameter. In addition, the tension estimated through back analysis method, which was conducted to minimize the difference between the modal frequencies calculated using finite element analysis of the hanger cables and the measured modal frequencies, was compared with that measured using the vibration method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.609-617
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• 2016

In general, Personal Navigation Systems (PNSs) can be defined systems to acquire pedestrian positional information. GPS is an example of PNS. However, GPS can only be used where the GPS signal can be received. Pedestrian Dead Reckoning (PDR) can estimate the positional information of pedestrians using Inertial Measurement Unit (IMU). Therefore, PDR can be used for GPS-disabled areas. This paper proposes a PDR scheme considering various movement types over GPS-disabled areas as combat environments. We propose a movement distance estimation scheme and movement direction estimation scheme as pedestrian's various movement types such as walking, running and crawling using IMU. Also, we propose a fusion algorithm between GPS and PDR to mitigate the lack of accuracy of positional information at the entrance to the building. The proposed algorithm has been tested in a real test bed. In the experimental results, the proposed algorithms exhibited an average position error distance of 5.64m and position error rate in goal point of 3.41% as a pedestrian traveled 0.6km.

• Journal of Korean Neurosurgical Society
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• v.30 no.7
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• pp.907-915
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• 2001

Objective : Percutaneous vertebroplasty is often complicated by the presence of multiple fractures or non-localizing pain in the patients with osteoporotic vertebral fractures. The purpose of this study is to estimate the value of preoperative radiologic studies in the localization of symptomatic vertebrae and to determine the factors which can influence on the clinical results. Materials and Methods : We retrospectively reviewed the clinical and radiologic data of 57 vertebrae in 30 patients underwent percutaneous vertebroplasty for osteoporotic vertebral compression fractures. Inclusion criteria was severe pain(McGill-Melzack score 3, 4 or 5) associated with the acute vertebral fractures and absence of spinal nerve root or cord compression sign. Acute symptomatic vertebral fracture was determined by the presence of signal change on MR images or increased uptake on whole body bone scan. Results : Pain improvement was obtained immediately in all patients and favorable result was sustained in 26 patients(86.7%) during the mean follow-up duration of 4.7 months(5 complete pain relief, 21 marked pain relief). Those who underwent vertebroplasty for all acute symptomatic vertebrae had significantly better clinical result than those who did not. Further vertebral collapse and eventual bursting fracture occurred in 1 vertebra which showed intradiskal leakage of bone cement and disruption of cortical endplate on postoperative CT scan. Conclusion : Preoperative MR imaging and whole body bone scan are very useful in determining the symptomatic vertebrae, especially in the patients with multiple osteoporotic vertebral fractures. To obtain favorable clinical result, the careful radiologic evaluation as well as clinical assessment is required. Control of PMMA volume seems to be the most critical point for avoiding complications.