• The Journal of the Acoustical Society of Korea
• /
• v.35 no.3
• /
• pp.216-222
• /
• 2016

Generation of a quiet zone in noisy environment is undoubtedly of considerable realistic significance. This paper describes development and implementation of a multichannel real-time active noise control (ANC) system for 3 dimensional noisy environment to enhance the quiet zone performance in terms of size and noise cancellation gain. The proposed ANC system employes a multichannel delay-compensated filtered-X least mean square (FXLMS) algorithm; its real-time implementation is designed in TMS320C6713 digital signal processor (DSP) board. The system is evaluated for cancelling various tonal frequency noises in the range from 100 to 500 Hz, and the performance is then illustrated by measuring the quiet zone in terms of sound pressure level (SPL) attenuation. Experiment results show that a quiet zone of quiet with satisfactory size and maximum 24 dB noise attenuation is successfully generated.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.2
• /
• pp.212-219
• /
• 1998

Unburned hydrocarbon is a key contributor to both the fuel economy and emissions of automotive engine. Cyclic variation of HC emission is of importance, especially during throttle transients. The real time measurement of hydrocarbon is particularly important to obtain a better understanding of the mechanisms for combustion and emissions, especially during cold start and throttle transient condition. This paper reports the cycle resolved measurement technique of unburned hydrocarbons to quantify rapid changes of in-cylinder concentration in the vicinity of spark plug by using the Fast Response Flame Ionization Detector(FRFID). While this instrument actually measures fuel concentration, its results can be indicative of the AFR behaviour. In order to understand the rapid change of hydrocarbons with cylinder pressure, it is necessary to study the response time delay of the system, including the time associated with gas transportation to FID. And signal from FRFID is correlated with cylinder pressure data to relate changes in mixture preparation to the classic analysis, such as indicated mean effective(IMEF) and ignition delay, etc.

• Journal of Korean Academy of Nursing
• /
• v.30 no.3
• /
• pp.659-669
• /
• 2000

Many patients of acute myocardial infarction showed delay time before seeking treatment although they needed immediate thrombolytic therapy once they perceived their symptoms. The objectives of this study were to identify the relationship between clinical symptoms and the delay, and to find the time spent before seeking the treatment. This study was a retrospective research. The delay time for the treatment consisted of the length of delay from symptom onset to patients' decision (T1), from patients' decision making to finding transportation (T2), and from taking transportation to the first hospital arrival(T3). The subjects were 89 patients who were admitted in the ICU and Cardiac Ward at Chonnam University Hospital with the first attack of acute myocardial infarction. Center, USA The data was collected for three months from March 1st to May 31st of 1998 through questionnaires and reviewing patients' charts: The chart information was suppled by two nurses working at the ICU and Cardiac Ward. The data was analyzed by using frequency, mean and ANOVA through the SAS program. The results of study summarized as follows: 1. Sixty two patients (69.7%) were male and twenty seven patients (30.3%) were female, the ratio of male to female was 2.3 : 1. 2. In daily life, the 70.8% of the patients felt chest pain and discomfort fatigue in 67.4%, dyspnea in 57.3%, and pain in arm, neck, and jaw in 52.8%. During the attack, 97.8% of the patients felt chest pain and discomfort dyspnea in 82.1%, pain in arm, neck, jaw in 67.4% and perspiration in 51.7%. 3. The length of time a patient spent seeking time for treatment (T1+T2+T3) was 94.6 minutes, in which the time for patients' decision making for treatment (T1) was 70.3 minutes, time for finding transportation (T2) was 8.2 minutes, and time for the transportation of the patient to the first hospital (T3) was 16.1 minutes. Time for patients' decision making to go to a hospital(T1) was 74.2% of the total time sought for treatment. 4. The differences of time sought for treatment between perceptions about the seriousness of the symptoms were significant (F= 6.5, p< .01). The more serious the heart symptoms they felt, the shorter the seeking time for treatment. 5. The differences of the time delay before treatment between the degree of the symptoms were significant (F= 2.9, p< .05). The patients with the typical chest pain and discomfort spent shorter the seeking time for treatment than those with the atypical symptoms of acute myocardial infarction. 6. The differences of transportation time to the first hospital between the types of cars that the patients used, were significant (F= 4.3, p< .01). When the patients used 119 or 129 they spent the least time (5.3 minutes) for transportation, and followed by way of an ambulance (15.6 minutes), private car (20.6 minutes), and taxi (24.8 minutes).

• The Journal of the Korea Contents Association
• /
• v.17 no.3
• /
• pp.589-595
• /
• 2017

We present an estimation model for optimal channel capacity required to data traffic transmission. The optimal channel capacity should be calculated in order to satisfy the permitted transmission delay of each wireless data services. Considering the discrete-time operation of digital communication systems and batch arrival of packet-switched traffic for various wireless services, $Geo^x$/G/1 non-preemptive priority queueing model is analyzed. Based on the heuristic interpretation of the mean waiting time, the mean waiting times of various data packets which have the service priority. Using the mean waiting times of service classes, we propose the procedure of determining the optimal channel capacity to satisfy the quality of service requirement of the mean delay of wireless services. We look forward to applying our results to improvement in wireless data services and economic operation of the network facilities.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.39 no.1
• /
• pp.23-28
• /
• 2021

Data analysis research using deep learning has recently been studied in various field. In this paper, we conduct a GNSS (Global Navigation Satellite System)-based meteorological study applying deep learning by estimating the ZWD (Zenith tropospheric Wet Delay) through MLP (Multi-Layer Perceptron) and LSTM (Long Short-Term Memory) models. Deep learning models were trained with meteorological data and ZWD which is estimated using zenith tropospheric total delay and dry delay. We apply meteorological data not used for learning to the learned model to estimate ZWD with centimeter-level RMSE (Root Mean Square Error) in both models. It is necessary to analyze the GNSS data from coastal areas together and increase time resolution in order to estimate ZWD in various situations.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.9
• /
• pp.1847-1853
• /
• 2011

Analysis of an indoor propagation channel has conventionally used the ray-tracing method. But, in this paper, we had modelling the channel for three dimensional indoor structure by the finite difference time domain method for three dimensional full wave analysis. An excitation signal of the FDTD method used plane wave. The plane wave was excited using the total field/scattered field method. And absorbing boundary condition used the perfectly matched layer method with 7 layers. An living room for the simulation of indoor channel modeling is surrounded the wall that be composed of the wood, the conductor, the glass and concrete. When there are furniture in the living room or not, it were simulated, respectively. As simulation results, we could identify the fading effect of multipath at indoor propagation environment, calculated mean excess delay and rms delay spread for the receiver design.

• The Journal of the Acoustical Society of Korea
• /
• v.17 no.3E
• /
• pp.43-46
• /
• 1998

Many of the active noise control system utilize a form of the least mean square(LMS) algorithm. This paper discusses the dependence of the convergence rate on the acoustic error path in the popular algorithm which is conventional "filtered-x LMS" and introduces new algorithm "constrained filtered-x LMS". The proposed method increase the convergence region regardless of the time-delay in the acoustic error path. In the algorithms, coefficients of the controller are adapted using the residuals of constrained structure which are defined in such a way that the control process become stationary. Advantages of constrained filtered-x LMS algorithm is illustrated by convergence analysis in the mean sense.

• Journal of Navigation and Port Research
• /
• v.40 no.2
• /
• pp.51-56
• /
• 2016

Expressways mean the primary arterial highways with a high level of efficiency and safety. However, Gyeongbu and Namhae expressways connected with Busan ports are showing travel time delay by increased traffic including the medium/large-sized vehicles of about 20% compared to those of about 13% regardless of the peak periods. This study, thus, intends to analyze lane traffic characteristics in the basic 8-lane segments of the above-mentioned expressways, compute the planning and buffer times based on travel time reliability, find the lane speed showing a higher correlation with planning time between the lane speeds in the basic 8-lane segments, and finally suggest a correlation model for predicting the planning time in expressways.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.16 no.10
• /
• pp.941-950
• /
• 1991

channel is severely degraded by multipath delay time spread. In this paper. We propose a simple multipath delay time detection method, which has a merit of in serviceable, yet simple H/W realizability for $\pi/4$ shift QPSK by detecting cross channel interference. A $\pi/4$ shift QPSK signal originally has quadrature channel(Q-ch) component. Thus in order to measure CCI between in-phase channel(I-ch) and quadrature channel(Q-ch), which closely related to multipath delay time, Frequency doubling scheme(frequency doubler) and differential detector is proposed, which makes $\pi/4$ shift QPSK signal look like BPSK and also makes it possible for CCI to be detected at I-ch detector output. To get an information from time varying I-ch output signal under the multipath lading environment, a method for obtaining the mean of the absolute value$(V_{MABS}(t))$ and another one for obtaining the root mean square value$(V_{RMS}(t))$ of CCI are proposed. Furthermore, a relationship between delay spread and CCI is also analyzed. In order to confirm theoretical results, computer simulation has been carried out under the quasi-static and Reyleigh distributed two ray multipath fading environments. A fairly good result was obtained. However it was also shown that this method is sensitive to bandwidth restriction to some extent. In addition, some idea for a simple hardware realization for the frequency doubler are given.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.47 no.3
• /
• pp.1-4
• /
• 2010

RS-485, communication bases from small network system must prepare in collision. The collision is that mean the data transfer breaks. For a stabilized communication chooses 1:N polling methods. But polling is low speed in addition to maybe overload Master device. So, usual N:N Prefers a communication. In this case, must be preparing to avoid collision or some solutions. Generally, to after collision retransmits after short time. It's called delay time for short time. When making a delay time, uses address of each systems. (Address of each node) If the many nodes collided, the each node has different delay time. When making a delay time, uses a usual random number. Making a random number is hard job. So uses a usual pseudorandom number. It is more difficult from small size MCU. The Chaos random number provides stabled value. Finally, when uses the Chaos random number, the stability and reliability of system get better.