• Journal of Sensor Science and Technology
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• v.20 no.1
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• pp.1-7
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• 2011

Undoped and Sb-doped $SnO_2$ nanofibers were prepared by electrospinning and their responses to $H_2$, CO, $CH_4$, $C_3H_8$, and $C_2H_5OH$ were measured. In the undoped $SnO_2$ nanofibers, the gas response ($R_a/R_g$, $R_a$: resistance in air, $R_g$: resistance in gas) to 100 ppm $C_2H_5OH$ was very high(33.9), while that to the other gases ranged from 1.6 to 2.2. By doping with 2.65 wt% Sb, the response to 100 ppm $C_2H_5OH$ was decreased to 4.5, whereas the response to $H_2$ was increased to 3.0. This demonstrates the possibility of detecting a high $H_2$ concentration with minimum interference from $C_2H_5OH$ and the potential to control the gas selectivity by Sb doping.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.6
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• pp.1327-1335
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• 2012

TPMS (Tire Pressure Monitoring System) is a safety assistant system to prevent the serious accident due to the damaged tire by the abnormal tire pressure. It is designed to transmit the measured data for pressure and temperature of tires from the sensor unit installed in each tire to signal processing unit installed in a vehicle. Based on the received information, a driver monitors the condition of tires using a display device, to maintain the optimum travelling condition. Since TPMS should employ the wireless communication technique, it may suffer from various interferences from external electrical or electronics devices. In order to suppress them, the beamforming techniques such as switching, minimum-variance distortionless-response (MVDR), and generalized sidelobe canceler (GSC) have been considered for TPMS. In this paper, we calculate computational complexities of three beamformers and suggest mathematical basis to compare their performance of the complexity.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.1
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• pp.129-135
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• 2003

Optical fiber has many advantages, such as high reliability, long lifetime, immunity to the electromagnetic interference, high speed response and low cost. In this study, we proposed and developed an optical fiber impact and pressure sensor for prevention of accident which occurs in the automatic system or auto door. The principle of the sensor is to detect different optical intensity caused by variation of a speckle pattern due to the external perturbation. Speckle pattern appears at the end of a multimode fiber in which coherent beam propagates. The fabricated sensor in this study was tested. As a result of experiments, amplitude of the output signal isn't linear, but it has sufficient sensitivity for a sensor. Moreover, we can control sensitivity of the sensor by an amplifier at receiver. It has several advantages which are ability of detection at all point on the multimode fiber, large sensitive area, and many application areas for a sensing impact and pressure.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4188-4206
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• 2016

Power control is widely used to reduce co-channel interference in wireless networks and guarantee the signal-to-interference plus noise ratio (SINR) of ongoing connections. This technique is also effective for wireless body area networks (WBANs). Although achieving satisfactory SINR is important for WBAN users, they may not be willing to achieve it at arbitrarily high power levels since power is a scarce resource in WBANs. Besides, for WBANs with different purposes, the QoS requirements and concern about the power consumption may be different. This motivates us to formulate the power control problem using the concepts from microeconomics and game theory. In this paper, the QoS objective is viewed as a utility function, which represents the degree of user satisfaction, while the power consumption is viewed as a cost function. The power control problem consequently becomes a non-cooperative multiplayer game, in which each player tries to maximize its net utility, i.e., the utility minus the cost. Within this framework, we investigate the Nash equilibrium existence and uniqueness in the game and derive the best response solution to reach the Nash equilibrium. To obtain the optimal transmission power in a distributed way, we further propose a utility-based and QoS-aware power control algorithm (UQoS-PCA). Tunable cost coefficient in UQoS-PCA enables this scheme to be flexible to satisfy diverse service requirements. Simulation results show the convergence and effectiveness of the proposed scheme as well as improvements over existing algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.9
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• pp.519-527
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• 2014

Adaptive arrays can minimize contributions from interferences incident onto an sensor array while preserving a signal the direction vector of which corresponds to the array steering vector to within a scalar factor. If there exist errors in the steering vector, severe performance degradation can be caused since the desired signal is misunderstood as an interference by the array. This paper presents an adaptive beamforming method which is robust against steering vector errors, exploiting a range of the desired signal direction. In the presented method, an correlation matrix of array response vectors is obtained through integration over the direction range and a minimization problem is formulated using some eigenvectors of the correlation matrix such that a more accurate steering vector than initially given one can be found. The minimization problem is transformed into a relaxed SDP (semidefinite program) problem, which can be effectively solved since it is a sort of convex optimization. Simulation results show that the proposed method outperforms existing ones such as ORM (outside-range-based method) and USM (uncertainty-based method).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.2
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• pp.122-127
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• 2001

The high stability of the interference pattern is very important in the case of measuring interference when a phase noise like a vibration occurs in the measuring environment. In this paper, we proposed the method of phase noise filtering by BaTiO$_3$ with the characteristic of SPPCM. Also, a beam with a shape of an ellipse was incident into BaTiO$_3$ by using the tilted lens so as to improve the reflectivity and the response time. And we confirmed the result by optical experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1154-1163
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• 2007

For orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP) should be longer than the length of channel impulse response. In order to prevent a loss of bandwidth efficiency due to the use of a CP, residual intersymbol interference cancellation (RISIC) method has recently been developed. In this paper, we first apply the RISIC algorithm to the space-time block coded (STBC) OFDM and the space-frequency block coded (SFBC) OFDM with insufficient CP. It is shown that in the STBC OFDM, tail cancellation as well as cyclic restoration of the RISIC should be repeated. Second, we propose iterative channel estimation method for the RISIC in the STBC OFDM system with insufficient CP. Based on the expectation-maximization (EM) algorithm, the proposed estimation method exploits the extrinsic probabilities of the channel decoder iteratively. The performance of the proposed method is evaluated by computer simulation in a multipath fading environment.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.5
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• pp.1-9
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• 1989

In binary digital transmission system the band-limiting is required for the better transmission efficiency. But in the case of band-limiting the intersymbol-interference (ISI) usually takes place. In this paper, in an attempt to design band-limiting filter which has minimum ISI and maximum stop-band loss, first, making use of analog filter by combining Binary Transversal Filter (BTF) and analog filter (4th Butterworhfilter), we found the value that minimizes ISI phenomenon by getting step response of rectangular pulse resulting from BTF in time domain. Second, we found filter characteristic we want to in frequency domain for band-limiting and minimized the error. And then we obtained resistor value (Tap coefficient) in order to design algorithm for optimum filter. Also we showed the example of simulation in case we established the resistors with 3,5 and 7 respectively. With 7 resistors set, we identified that the ripple of about minus 30dB was taken place.

• Journal of Oral Medicine and Pain
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• v.40 no.2
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• pp.47-54
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• 2015

Purpose: Besides depression and anxiety, recently pain catastrophizing has been emphasized for an important psychological factor explaining pain response in various pain conditions including temporomandibular disorders (TMDs). The aims of this study were to evaluate pain catastrophizing of TMD patients and to investigate how the level of pain catastrophizing related with clinical variables and psychometric morbidity. Methods: Inclusion criterion was all new TMD patients ${\geq}18$ years old attending the Department of Orofacial Pain and Oral Medicine of Dankook University Dental Hospital (Cheonan, Korea) over three-month period in 2014, who completed questionnaires. The questionnaires included the Brief Pain Inventory (BPI), Pain Catastrophizing Scale (PCS), and Symptom Check List- 90-Revised (SCL-90-R). All of them were examined clinically and diagnosed. Results: One hundred fifty five patients diagnosed as TMDs were participated in this study (mean age of $38.7{\pm}15.2$ years, male:female=1:2.5). Mean PCS score of the patients was 17.3 with standard deviation of 12.6. By the median of the PCS score (i.e., 15), the subjects were categorized into the high (${\geq}15$) and low catastrophizers (<15). Increased pain severity and interference and increased score of psychological features of SCL-90-R were found in the TMD patients with higher level of catastrophizing (p<0.001) and there was weak to moderate correlation between those factors (p<0.05). Difference in catastrophizing level was not found for other variables such as age, gender, duration of pain, education level and types of TMDs. Conclusions: Conclusively, pain catastrophizing of TMD patients relates positively to pain severity and pain interference. In addition to depression and anxiety, pain catastrophizing is positively correlated with variable other psychological morbidity such as somatization, obsessive- compulsive, interpersonal sensitivity, paranoid ideation and psychoticism. Types of TMD diagnosis do not seem to affect catastrophizing level. The results of this study suggest that pain catastrophizing should be emphasized and assessed in the TMD patients.

• Journal of Navigation and Port Research
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• v.35 no.8
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• pp.643-647
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• 2011

In this paper, we study the application of DSSS(Direct Sequence Spread Spectrum) in underwater acoustic communication for robust the ISI(Inter-Symbol Interference. We confirm the application of DSSS in underwater acoustic communication in underwater by the simulation with underwater channel impulse response and experiment. As a simulation result, the BER of QPSK technique is $1.14{\times}10^{-1}$ and the BER of DSSS technique is $6.73{\times}10^{-3}$. And we performed the experiment of DSSS technique in underwater. As a experiment result, the BER of QPSK technique is $3.19{\times}10^{-1}$ and the BER of DSSS technique is $5.17{\times}10^{-4}$.