• Journal of Korea Multimedia Society
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• v.8 no.12
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• pp.1589-1596
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• 2005

The imprecise real-time system provides flexibility in scheduling time-critical tasks. Most scheduling problems of satisfying both 0/1 constraint and timing constraints, while the total error is minimized, are NP complete when the optional tasks have arbitrary processing times. Liu suggested a reasonable strategy of scheduling tasks with the 0/1 constraint on uniprocessors for minimizing the total error. Song et al suggested a reasonable strategy of scheduling tasks with the 0/1 constraint on multiprocessors for minimizing the total error. But, these algorithms are all off-line algorithms. On the other hand, in the case of on line scheduling, Shih and Liu proposed the NORA algorithm which can find a schedule with the minimum total error for a task system consisting solely of on-line tasks that are ready upon arrival. But, for the task system with 0/1 constraint, it has not been known whether the NORA algorithm can be optimal or not in the sense that it guarantees all mandatory tasks are completed by their deadlines and the total error is minimized. So, this paper suggests an optimal algorithm to search minimum total error for the imprecise on-line real-time task system with 0/1 constraint. Furthermore, the proposed algorithm has the same complexity, O(N log N), as the NORA algorithm, where N is the number of tasks.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.3
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• pp.646-653
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• 2007

This paper tries to find out how a household's purchase probability and purchase time changes as time passes. Previous studies show that a highly educated family with high income, which is usually an early adopter in a new product adoption, tends to be an early adopter of DTV. On the contrary, in the dynamic sense of diffusion, this study shows that an average household's purchase probability would become higher and its purchase time would come sooner than later, as price falls sharply. As time passes, it turns out that DTV is becoming a necessary good rather than a luxury good. Thus, in the future, either a household's popuation characteristics or information on new product are not expected to affect the probability of a household's purchasing DTV.

• The Journal of Korean Physical Therapy
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• v.12 no.2
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• pp.121-132
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• 2000

This study was carried out to determine the influencing of electrical stimulation to cervicothoracic sympathetic ganglion(CTSG; stellate ganglion) u the sympathetic tone. For the purpose of this study. the stimulation was given to both the interferential current stimulation(ICS: AMF 100Hz) group consisting of 10 person(males 8, females 2) and the transcutaneous nerve electrical stimulation(TENS: 100 Hz) group of 10(males 7, females 3) in the right side of the trachea with probe electrodes. Then. the temperature changes on the surfaces of the forehead. cheek, neck and internal ear of cephalocervix, which is subject to the influence of the cervicothoracic sympathetic ganglion, and the palm. which is the end of the upper limbs. measured before. immediately alter. 10 minutes after and 20 minutes after experiment. The results are summarized as follows. 1. The emergence of remarkable Horner's symptoms which appear due to the changes of the tone of cervicothoracic sympathetic ganglion was not seen. However, in the interferential current stimulation group there were two felt the sense of warmth in the facial region and one person who felt it in the upper limbs, and in the transcutaneous nerve electrical stimulation group there was each one person who felt the sense of warmth in the facial region and in the upper limbs, respectively. Both groups have each one person who felt the sense of oppression in the eyelids. Three persons of the interferential current stimulation group and two persons of the transcutaneous nerve electrical stimulation group have the sense of hoarse voice or numbness in the neck. These are the symptoms that appeared during stimulation, so it is difficult for them to be considered as the direct effects of the changes of the tone of cervicothoracic sympathetic ganglion. 2. The t-test was performed to determine the significance between the right, which is the experimental side, and the left, which is the non-experimental side. Significance between the right, which is the experimental side, and the left, which is the non-experimental side. Significant changes were seen in the necks of the interferential current stimulation group and in the cheeks and internal ears of the transcutaneous nerve electrical stimulation immediately after experiment(P<.05). And the interferential current stimulation group showed a very high significance in the cheeks immediately after experiment and in the necks ten minutes after experiment(p<.01). Therefore, it could be seen that the electrical stimulation had an influencing on the changes of body temperature of the cephalocervix. 3. In both the interferential current stimulation group and the transcutaneous nerve electrical stimulation group, the forecheads, checks and necks of the cephalocervix in the experimental side(right) rather than the non-experimental side(left) had mostly a statistically significant rise in temperature immediately after experiment. The one-way ANOVA was carried out to determine the temperature change of on the surface of the body with the lapse of time; before, immediately after, ten minutes after and tewenty minutes after experiment. But no statistical significance was found from both the right and left sides.

• Journal of Music and Human Behavior
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• v.13 no.1
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• pp.41-60
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• 2016

This study investigated how people who became blind midway through life used music and how these uses differed according to individual factors. Sixty-one late-blind adults aged 40 to 60 years attending six welfare centers for the blind in Seoul and Gyeonggi region participated in this research. Participants were asked to complete a 25-question survey in Braille on music utilization and preference, as well as the purpose of music utilization. The response rate was 87.1%. The results were as follows. First, with regard to listening preference, they reported preferring to listen to upbeat popular music on the radio when resting at home. They liked to sing along to lyrics reminiscent of personal memories. String instruments were preferred when playing an instrument. With regard to the reason for using music, inducing mood change was found to be the biggest reason, followed by seeking enjoyment, comfort, sense of achievement, and sense of belonging. Third, for people with adventitious visual impairments, individual factors, such as gender, level of disability, and period without eyesight, did not reveal any significant differences. Last, participants were found to obtain a higher sense of belonging through music compared to those having low vision. Regarding time without eyesight, it appeared that the shorter the period, the higher the sense of belonging participants had from utilizing music, and vice versa. This study provides fundamental information for organizing an effective music program that can meet the needs and demands of people with adventitious visual impairments.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.1-7
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• 2012

In this paper, we investigated the throughput of a cognitive radio network where two primary frequency channels (PCs) are sensed and opportunistically accessed by N secondary users. The sharing sensing member (SSM) protocol is introduced to sense both PCs simultaneously. According to the SSM protocol, N SUs (Secondary User) are divided into two groups, which allows for the simultaneous sensing of two PCs. With a frame structure, after determining whether the PCs are idle or active during a sensing slot, the SUs may use the remaining time to transmit their own data. The throughput of the network is formulated as a convex optimization problem. We then evaluated an iterative algorithm to allocate the optimal sensing time, fusion rule and the number of members in each group. The computer simulation and numerical results show that the proposed optimal allocation improves the throughput of the SU under a misdetection constraint to protect the PCs. If not, its initial date of receipt shall be nullified.

• The Journal of the Acoustical Society of Korea
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• v.17 no.4E
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• pp.3-10
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• 1998

This paper concerns the dynamical behavior, in probabilistic sense, of a feedforward neural network performing auto association for novelty. Networks of retinotopic topology having a one-to-one correspondence between and output units can be readily trained using back-propagation algorithm, to perform autoassociative mappings. A novelty filter is obtained by subtracting the network output from the input vector. Then the presentation of a "familiar" pattern tends to evoke a null response ; but any anomalous component is enhanced. Such a behavior exhibits a promising feature for enhancement of weak signals in additive noise. As an analysis of the novelty filtering, this paper shows that the probability density function of the weigh converges to Gaussian when the input time series is statistically characterized by nonsymmetrical probability density functions. After output units are locally linearized, the recursive relation for updating the weight of the neural network is converted into a first-order random differential equation. Based on this equation it is shown that the probability density function of the weight satisfies the Fokker-Planck equation. By solving the Fokker-Planck equation, it is found that the weight is Gaussian distributed with time dependent mean and variance.

• ETRI Journal
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• v.36 no.4
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• pp.545-553
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• 2014

This paper proposes an algorithm to sense orthogonal frequency-division multiplexing (OFDM) signals in cognitive radio (CR) systems. The basic idea behind this study is when a primary user is occupying a wireless channel, the covariance matrix is non-diagonal because of the time domain cross-correlation of the cyclic prefix (CP). In light of this property, a new decision metric that measures the power of the data found on two minor diagonals in the covariance matrix related to the CP is introduced. The impact of synchronization errors on the signal detection is analyzed. Besides this, a likelihood-ratio test is proposed according to the Neyman-Pearson criterion after deriving probability distribution functions of the decision metric under hypotheses of signal presence and absence. A threshold, subject to the requirement of probability of false alarm, is derived; also the probabilities of detection and false alarm are computed accordingly. Finally, numerical simulations are conducted to demonstrate the effectiveness of the proposed algorithm.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.121-129
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• 2005

In this paper, we consider a periodic preventive maintenance(PM) policy in which each PM reduces the hazard rate of amount proportional to the failure intensity, which increases since the last PM and slows down the wear-out speed to that of new one. And the proportion of reduction in hazard rate decreases with the number of PMs. Our model is similar to $ARI_1$ proposed by Doyen and Gaudoin(2004) in the sense of reduction of hazard rate. Our model has totally different wear-out pattern of hazard rate after PM's, however, and the proportion of reduction depends on the number of PM's. Assuming that the system undergoes only minimal repairs at failures between PM's, the expected cost rate per unit time is obtained. The optimal number N of PM and the optimal period x, which minimize the expected cost rate per unit time are discussed. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.4
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• pp.75-84
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• 1995

Fault simulators are used for accurate evaluation of fault coverages of digital circuits. But fault simulation becomes time and memory consuming job because computation time is proportional to wquare of size of circuits. Recently, several approximate algorithms for testability analysis have been published to cope with the problems. COP is very fast but cannot be used for sequential circuits, while STAFAN can ve used for sequential circuits but requires large amount of computation because it utilizes logic simulation results. In this paper EXTASEC(An Extension of Testability Analysis for Sequential Circuits) is proposed. It is an extension of COP in the sense that it is the same as COP for combinational circuits, but it can handle sequential circuits, Xicontrollability and backward line analysis are key concept for EXTASEC. Performance of EXTASEC is proven by comparing EXTASEC with a falut simulator, STAFAN, and COP for ISCAS circuits, and the result is demonstated.

• Journal of Communications and Networks
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• v.15 no.3
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• pp.245-251
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• 2013

This paper addresses the issue of time-difference-of-arrival (TDOA) estimation for complex noncircular signals. First, under the wide-sense stationary assumption, we derive the maximum likelihood (ML) estimator and the Cramer-Rao lower bound for Gaussian noncircular signals in Gaussian circular noise. The ML estimator uses the second-order statistics information of a noncircular signal more comprehensively when compared with the cross-correlation (CC) and the conjugate CC estimators. Further, we present a scheme to modify the traditional signal-selective TDOA methods for noncircular signals on the basis of the cyclostationarity of man-made signals. This scheme simultaneously exploits the information contained in both the cyclic cross-correlation (CCC) and the conjugate CCC of a noncircular signal.