• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.602-607
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• 2002

In this paper, we proposed an approach to efficiently compress and transmit multiresoltion 3D lariat models for multimedia and very low bit rate applications. A personal facial model is obtained by a 3D laser digitizer, and further re-quantized at several resolutions according to different scope of applications, such as animation, video game, and video conference. By deforming 2D templates to match and re-quantize a 3D digitized facial model, we obtain its compressed model. In the present study, we create hierarchical 2D lariat wireframe templates are adapted according to facial feature points and the proposed piecewise chainlet affined transformation(PACT) method. The 3D digitized model after requantization are reduced significantly without perceptual loss. Moreover the proposed multiresoulation lariat models possessed of hierarchial data structure are apt to be progressively transmitted and displayed across internet.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.205-212
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• 2013

The previous chatting systems have generally used methods based on lexical agreement between users' input sentences and target sentences in a database. However, these methods often raise well-known lexical disagreement problems. To resolve some of lexical disagreement problems, we propose a three-step sentence searching method that is sequentially applied when the previous step is failed. The first step is to compare common keyword sequences between users' inputs and target sentences in the lexical level. The second step is to compare sentence types and semantic markers between users' input and target sentences in the semantic level. The last step is to match users's inputs against predefined lexico-syntactic patterns. In the experiments, the proposed method showed better response precision and user satisfaction rate than simple keyword matching methods.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.75-81
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• 2008

The authors present a more accurate analysis of the bit error rate (BER) performance for multicode code division multiple access (CDMA) systems equipped with a multipath interference canceler (MPIC) over multipath fading channels. At first, we consider the problem of previous researches. It is that the previous analyses do not match with simulations even in the case without MPIC. This mismatch also causes the difference between the analysis and simulations when an MPIC is applied. Therefore, what is needed is to verify the reason of this mismatch at the initial stage. Numerical results obtained from the proposed analytical method indicate that the performance mismatch between the previous analysis and simulations is caused by not fie Gaussian approximation which is generally used at the performance analysis of CDMA systems but the additional Gaussian approximation (AGA) for multipath interferences. Based on this effect, we propose a more accurate performance analysis not using AGA and its accuracy is verified by simulations. Furthermore, it is confirmed that the proposed analysis presents an analytical lower bound which can be achieved by MPIC.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.682-685
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• 2017

An experimental study was carried out to investigate the injection characteristics of non-circular effervescent type twin-fluid nozzles. For this purpose, two types of non-circular nozzles (E1, E2) and one kind of circular nozzle (C) were used. At this time, the Aerorator mounted on the nozzle used three different diameters to match the aspect ratio with the nozzle exit area. Therefore, experiments were performed according to three aspect ratios for each nozzle, and a total experiments were conducted. Experiments were carried out by controlling the amount of air flowing after fixing the flow rate of the liquid, and the nozzle internal pressure and SMD were measured, and the jet image was taken from the nozzle. The discharge coefficients of the three kinds of nozzles were compared with the conventional equation and the Jedelsky's equation, and the Jedelsky's equation was found to be about 4 times larger. The droplet size (SMD) injected from the nozzle was found to be smaller in the non-circular shape than in the circular shape, which is expected to be caused by the difference of the discharge coefficient values.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.5
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• pp.543-548
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• 2014

Multiple-model based speech recognition framework (MMSR) has been known to be very successful in speech recognition. Since it uses multiple hidden Markov modes (HMMs) that corresponds to various noise types and signal-to-noise ratio (SNR) values, the selected acoustic model can have a close match with the test noisy speech. However, since the number of HMM sets is limited in practical use, the acoustic mismatch still remains as a problem. In this study, we experimentally determined the optimal SNR mapping between the test noisy speech and the HMM set to mitigate the mismatch between them. Improved performance was obtained by employing the SNR mapping instead of using the estimated SNR from the test noisy speech. When we applied the proposed method to the MMSR, the experimental results on the Aurora 2 database show that the relative word error rate reduction of 6.3% and 9.4% was achieved compared to a conventional MMSR and multi-condition training (MTR), respectively.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.5
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• pp.1025-1034
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• 2009

In steel making production line, steel slabs are given a unique identification number. This identification number, Slab management number(SMN), gives information about the use of the slab. Identification of SMN has been done by humans for several years, but this is expensive and not accurate and it has been a heavy burden on the workers. Consequently, to improve efficiency, automatic recognition system is desirable. Generally, a recognition system consists of text localization, text extraction, character segmentation, and character recognition. For exact SMN identification, all the stage of the recognition system must be successful. In particular, the text localization is great important stage and difficult to process. However, because of many text-like patterns in a complex background and high fuzziness between the slab and background, directly extracting text region is difficult to process. If the slab region including SMN can be detected precisely, text localization algorithm will be able to be developed on the more simple method and the processing time of the overall recognition system will be reduced. This paper describes about the slab region localization using SIFT(Scale Invariant Feature Transform) features in the image. First, SIFT algorithm is applied the captured background and slab image, then features of two images are matched by Nearest Neighbor(NN) algorithm. However, correct matching rate can be low when two images are matched. Thus, to remove incorrect match between the features of two images, geometric locations of the matched two feature points are used. Finally, search rectangle method is performed in correct matching features, and then the top boundary and side boundaries of the slab region are determined. For this processes, we can reduce search region for extraction of SMN from the slab image. Most cases, to extract text region, search region is heuristically fixed [1][2]. However, the proposed algorithm is more analytic than other algorithms, because the search region is not fixed and the slab region is searched in the whole image. Experimental results show that the proposed algorithm has a good performance.

• Journal of the Korean Society of Safety
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• v.26 no.1
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• pp.1-7
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• 2011

When the pumps stopped in the operation by the power failure, the hydraulic transients take place in the sudden change of a velocity of pipe line. Each and every water hammer problem shows the critical stage to be greatly affected the facts of safety and reliability in case of power failure. The field tests of the water hammer executed at Cheong-Yang booster pump station having an air chamber. The effects were studied by both the practical experiments and the CFD(Computational Fluid Dynamics : Surge 2008). The result states that the system with water hammering protection equipment was much safer when power failure happens. The following data by a computational fluid dynamic analysis are to be shown below, securing the system stability and integrity. (1) With water hammering protection equipment. (1) Change of pressure : Up to $15.5\;kg/cm^2$ in contrary to estimating $16.88\;kg/cm^2$. (2) Change rate of water level : 52~33% in contrary to estimating 55~27%. (3) Note that the operational pressure of pump runs approx. 145 m, lowering 155 m of the regularity head of pump. (4) Note that the cycle of water hammering delays from 80 second to 100 second, together with easing the function of air value at the pneumatic lines. (2) Change of pressure without water hammering protection equipment : Approximate $22.86\;kg/cm^2$. The comprehensive result says that the computational fluid dynamics analysis would match well with the practical field-test. It was able to predict Max. or Min. water hammering time in a piping system. This study aims effectively to alleviate water hammering in a pipe line to be installed with air chamber at the pumping station and results in making the stability of pump system in the end.

• Journal of Biomedical Engineering Research
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• v.27 no.5
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• pp.274-281
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• 2006

In this paper, we propose a ubiquitous $SaO_2$ monitoring system for patients using oxygen therapy. For these patients, the ability to monitor oxygen saturation ubiquitously is very important fur accurate adjustment of ventilator's flow rate to match the patient's time-varying requirements with the shortest lag time possible. We have developed a portable device to measure $SaO_2$ and transmit it to hospital in real-time or in store-and-forward mode through the integration of $Bluetooth^{TM}$ technology and the code division multiple access (CDMA) cellular network. We also developed software for doctors to receive and manage the patients' $SaO_2$ information. Performance of the developed system was evaluated as acceptable by assessing the accuracy of the measured oxygen saturation value and the stability of communication network. Test results in real clinical setting demonstrate that our system is feasible for immediate use in home oxygen therapy.

• Journal of KIISE:Databases
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• v.30 no.4
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• pp.408-419
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• 2003

Data warehouses are usually dedicated to the processing of quires issued by decision support system(DSS). The response time of DSS queries is typically several orders of magnitude higher than the one of OLTP queries. Since DSS queries are often submitted interactively, techniques for reducing their response time are important. The caching of query results is one such technique particularly well suited to the DSS environment. In this paper, we present a cache manager for such an environment. Specifically, we define a canonical form of query. The cache manager looks up a query based on the exact query match or using a suggested query split process if the query is found is non-canonical form or in canonical form, respectively. It dynamically maintains the cache content by employing a profit function which reflects in an integrated manner the query execution cost, the size of query result, the reference rate, the maintenance cost of each result due to updates of their base tables, and the frequency of such updates. We performed the experimental evaluation and it positively shows the performance benefit of our cache manager.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.8
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• pp.3862-3888
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• 2017

In high diversity node situation, single-channel MAC protocols suffer from many collisions. To solve this problem, the research of multichannel MAC protocol has become a hotspot. And the cyclic quorum-based multichannel (CQM) MAC protocol outperformed others owing to its high frequency utilization. In addition, it can avoid the bottleneck that others suffered from and can be easily realized with only one transceiver. To obtain the accurate performance of CQM MAC protocol, a Markov chain model, which combines the channel hopping strategy of CQM protocol and IEEE 802.11 distributed coordination function (DCF), is proposed. The metrics (throughput and average packet transmission delay) are calculated in performance analysis, with respect to node number, packet rate, channel slot length and channel number. The results of numerical analysis show that the optimal performance of CQM protocol can be obtained in saturation bound situation. And then we obtain the saturation bound of CQM system by bird swarm algorithm (BSA). Finally, the Markov chain model and saturation bound are verified by Qualnet platform. And the simulation results show that the analytic and simulation results match very well.