• Proceedings of the KOR-KST Conference
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• 2007.11a
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• pp.878-887
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• 2007

• The Journal of the Acoustical Society of Korea
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• v.23 no.1
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• pp.47-53
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• 2004

We propose a new speech enhancement algorithm based on left-right Hidden Markov Model (HMM) with state decision using Log-likelihood Ratio Test (LRT). Since the conventional HMM-based speech enhancement methods try to improve speech quality for all states, they introduce huge computational loads inappropriate to real-time implementation. In the left-right HMM, only the current and the next state are considered for a possible state transition so to reduce the computational complexity. In this paper, we propose a method to decide the current state by using the LRT on the previous state. Experimental results show that the proposed method improves the speed up to 60% with 0.2∼0.4 dB degradation of speech quality compared to the conventional method.

• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.119-124
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• 2010

Light rail is an electric railway system, characterized by its ability to operate single or multiple car consists (trains) along exclusive rights-of-way at ground level, on aerial structures, in subways or in streets, able to board and discharge passengers at station platforms or at street, track, or car-floor level and normally powered by overhead electrical wires. Depending upon the specific system, the light rail lends some major advantages to urban settings. The evaluation of light rail technology as a potential component of regional transit systems has been the subject of extensive studies throughout the country in the past decade. For the study, feasibility was defined as "the ability of an LRT system to achieve certain level of transportation market in comparison with other transportation alternatives." This paper describes the feasibility study to evaluate a proposed light rail development project. The minimum are those LRT systems that would met to make a project feasible for further evaluation.

• The Journal of the Acoustical Society of Korea
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• v.10 no.1
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• pp.20-29
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• 1991

A fundamental assumption in conventional linear predictive coding (LPC) analysis procedure is that the input to an all-pole vocal tract filter is white process. In the case of periodic inputs, however, a pitch bias error is introduced into the conventional LP coefficient. Multi-pulse (MP) LP analysis can reduce this bias, provided that an estimate of the excitation is available. Since the prediction error of conventional LP analysis can be modeled as the sum of an MP excitation sequence and a random noise sequence, we can view extracting MP sequences from the prediction error as a classical detection and estimation problem. In this paper, we propose an algorithm in which the locations and amplitudes of the MP sequences are first obtained by applying a likelihood ratio test (LRT) to the prediction error, and LP coefficients free of pitch bias are then obtained from the MP sequences. To verify the performance enhancement, we iterate the above procedure with adaptive threshold at each step.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2D
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• pp.183-187
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• 2012

This study is to prepare the emergency response procedures for an unmanned LRT (Light Rapid Transit) which is being commercially operated recently. This emergency response procedure adds several particular characteristics which happens in the hardware and software aspects at the unmanned LRT in addition to the present emergency response procedures. The emergency response procedure has to conform to the emergency response planning. For doing that this emergency response procedure includes three important sub systems. First of all, the functional emergency response system has been developed. Secondly, Standard Operation Procedure (SOP) is suggested for the better and faster emergency response between emergency response personnel and institutes. Thirdly, emergency response training and drilling system is also provided for emergency response personnel. Finally, a software program for emergency response training and drilling will be developed and suggested to be used for the emergency response personnel.

• Journal of the Korean Society for Railway
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• v.18 no.5
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• pp.502-511
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• 2015

The purpose of this study is to prioritize the importance of urban railway service quality through statistical analysis. This was done to maximize customer satisfaction by providing customers of urban railway services (including LRT), operated by the local government, with a better customized service quality. It was hoped that this project would boost the need for public transportation by increasing customer satisfaction, which would eventually lead to more profitable revenue. The results of validity certification of expectations and perceptions before and after the use of government funded urban railway and private sector invested urban railways show that there are gaps for 18 items for the government funded urban rail projects (p<.01), while there is no significant difference for 2 items between expectation and perception (p>.05); private sector invested urban railway projects show differences for all 20 items (p<.001). Therefore, IPA analysis is conducted to improve the service quality; this should lead to a remedy that focuses on service quality. The findings of this study will contribute to providing management strategies for boosting customer satisfaction and creating revenue through customized service quality in the urban railway operating industry (including LRT), which is currently suffering from chronic deficits.

• The Journal of Korean Physical Therapy
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• v.34 no.2
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• pp.57-62
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• 2022

Purpose: The purpose of this study was to determine the effects of bilateral visual feedback training with visual targets on the postural balance and fall efficacy of stroke patients with hemiparesis. Methods: A total of 24 stroke patients with hemiparesis were randomly assigned to either a bilateral visual feedback training (BVFT, n=8) group, unilateral visual feedback training (UVFT, n=8) group, or a control group (n=8). The BVFT and UVFT groups performed weight-bearing training on the bilateral (less-affected and affected side) or unilateral side (affected side) with visual feedback using visual targets. The control group performed squat training without visual feedback using visual targets. The training program was conducted in the form of 3 sets a day, 3 times a week, for 4 weeks. The participants were evaluated using the Berg balance scale (BBS), lateral reaching test (LRT), timed up and go test (TUG), and the activities-specific balance confidence scale (ABC). Results: In the intra-group comparison after the intervention, the BVFT group showed a significant difference in the BBS, TUG, affected and less-affected side LRT, and ABC (p<0.05). The UVFT group showed a significant difference in the BBS and ABC (p<0.05). In the inter-group comparison after the intervention, the BVFT group showed significant improvements in their BBS, affected side LRT, and TUG, when compared to the control group (p<0.05). Conclusion: These findings show that bilateral visual feedback training with visual targets during bilateral weight-bearing exercises can improve the postural balance function in stroke patients.

• The Journal of the Acoustical Society of Korea
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• v.27 no.7
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• pp.372-378
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• 2008

Voice activity detectors (VAD) are important in wireless communication and speech signal processing, In the conventional VAD methods, an expression for the likelihood ratio test (LRT) based on statistical models is derived in discrete Fourier transform (DFT) domain, Then, speech or noise is decided by comparing the value of the expression with a threshold, This paper presents a new statistical VAD method based on a signal subspace approach, The probabilistic principal component analysis (PPCA) is employed to obtain a signal subspace model that incorporates probabilistic model of noisy signal to the signal subspace method, The proposed approach provides a novel decision rule based on LRT in the signal subspace domain, Experimental results show that the proposed signal subspace model based VAD method outperforms those based on the widely used Gaussian distribution in DFT domain.

• The Journal of the Acoustical Society of Korea
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• v.26 no.1
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• pp.16-24
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• 2007

Voice activity detectors (VADs) are important in wireless communication and speech signal processing. In the conventional VAD methods. an expression for the likelihood ratio test (LRT) based on statistical models is derived. Then, speech or noise is decided by comparing the value of the expression with a threshold. We propose a new method with the modified decision rule based on the Gaussian distribution and the uniformly most power (UMP) test. This method requires the distribution of the absolute value of the incoming speech signal. Then we can obtain the final decision through the relation between the Rayleigh distributions. This VAD method can detect speech without a priori signal-to-noise ratio (SNR) which is required in the conventional VAD algorithms. Additionally, in the various VAD performance tests, the proposed VAD method is shown to be more effective than the traditional scheme.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2006.11a
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• pp.384-389
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• 2006

The needs for Light Railroad Transit(LRT) have been increased due to the heavy traffic congestions in large cities like Seoul, Korea. Korean government is seeking the LRT system development (including planning, designing, construction, and maintenance and operations) in terms of public-private-partnership (PPP). At the private sector side, it is crucial to estimate the life cycle cost (LCC) to project the cash flow during the O&M period. Since the most construction and O&M cost of LRT project is at the bridge construction, a cost analysis model and a cost breakdown structures (CBS) on LRT bridges are discussed through in depth literature reviews. Construction and maintenance cost of bridges are collected and analyzed. LCC is analyzed by types of bridge superstructures and historical data of repair and rehabilitation (R&R) is investigated. There have been scarce number of LCC analysis on railway bridges. This research delivers a well-defined CBS and maintenance cost data, which will be a great benefit to the systematic maintenance strategy development for railroad bridges.