• Atmosphere
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• v.29 no.4
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• pp.501-509
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• 2019

Asian Dust is a meteorological phenomenon that sand particles are raised from the arid and semi-arid regions-Taklamakan Desert, Gobi Desert and Inner Mongolia in China-and transported by westerlies and deposited on the surface. Asian dust results in a negative effect on human health as well as environmental, social and economic aspects. For monitoring of Asian Dust, Korea Meteorological Administration operates 29 stations using a continuous ambient particulate monitor. Kim et al. (2016) developed an automatic quality check (AQC) algorithm for objective and systematic quality check of observed PM₁₀ concentration and evaluated AQC with results of a manual quality check (MQC). The results showed the AQC algorithm could detect abnormal observations efficiently but it also presented a large number of false alarms which result from valid error check. To complement the deficiency of AQC and to develop an AQC system which can be applied in real-time, AQC has been modulated. Based on the analysis of instrument status codes, valid error check process was revised and 6 status codes were further considered as normal. Also, time continuity check and spike check were modified so that posterior data was not referred at inspection time. Two-year observed PM₁₀ concentration data and corresponding MQC results were used to evaluate the modulated AQC compared to the original AQC algorithm. The results showed a false alarm ratio decreased from 0.44 to 0.09 and the accuracy and the probability of detection were conserved well in spite of the exclusion of posterior data at inspection time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.2B
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• pp.44-52
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• 2005

This paper proposes a neural network prediction model to improve the valid packet transmission rate for the QoS(Quality of Service) of multimedia transmission. The Round Trip Time(RTT) and Packet Loss Rate(PLR) are predicted using a neural network and then the transmission rate is decided based on the predicted RTT and the PLR. The suggested method will improve the transmission rate since it uses the rate control factors corresponding to time of data is being transmitted, while the conventional one uses the transmission rate determined based on the past informations. An experimental set-up has been established using a Linux PC system, and the multimedia data are transmitted using UDP protocol in real time. The valid transmitted packets are about 5% higher than the one in the conventional TCP-Friendly congestion control method when the suggested algorithm was applied.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.195-198
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• 1997

This paper proposes the effective compensation method of the rotor time constant of induction motor. An indirect vector control method is highly dependent on the motor parameters. To solve the problem of performance degradation due to parameter variation in an indirect vector control of induction motor, we compensate the rotor time constant by current error feedback. The proposed method is a simple on-line rotor time constant compensation method using the information from terminal voltages and currents. As the current error, difference between current command and estimated current, approaches to zero, the value of rotor time constant in an indirect vector controller follows the real value of induction motor. This scheme is valid transient region as well as steady state region regardless of low or high speed. This method is verified by computer simulation. For this, we constructed the simulation model of induction motor, indirect vector controller and current regulated PWM (CRPWM) voltage source inverter (VSI) using SIMULINK in MATLAB.

• Journal of the Korean Statistical Society
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• v.35 no.4
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• pp.453-458
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• 2006

It is well known fact for the iid data that the limiting standard errors of sample autocorrelations are all unity for all time lags and they are asymptotically independent for different lags (Brockwell and Davis, 1991). It is also usual practice in time series modeling that this fact continues to be valid for white noise series which is a sequence of uncorrelated random variables. This paper contradicts this usual practice for white noise. We consider a sequence of martingale differences which belongs to white noise time series and derive exact joint asymptotic distributions of sample autocorrelations. Some implications of the result are illustrated for conditionally heteroscedastic time series.

• Nuclear Engineering and Technology
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• v.4 no.2
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• pp.102-108
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• 1972

Time-dependent neutron transport equation with delayed neutrons is analytic-ally solved in the case of isotropic scattering with constant cross sections. The equations in the two divided time regions are obtained from the original equation by the asymptotic method. It is shown that the approximate solutions in each time region are uniformly valid in time to the order of the inverse magnitude of the velocity.

• Bulletin of the Korean Chemical Society
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• v.7 no.3
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• pp.224-228
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• 1986

A nonlinear theory is presented for the fluctuations of intermediates in the Brusselator near the critical point caused by diffusion. The method used is the two time scaling method different from the conventional method in the sense that a slight nonlinear effect is included in the initial time region where the linear approximation is conventionally valid. The result obtained by the nonlinear theory shows that fluctuations close to the critical point approach the value of a stable steady state or deviate infinitely from an unstable steady state, as time goes to infinity, while the linear theory gives approximately time-independent fluctuations. A brief discussion is given for the correlation at a time between fluctuating intermediates when the system approaches a stable steady state.

• Communications for Statistical Applications and Methods
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• v.29 no.3
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• pp.353-371
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• 2022

This paper analyzes death counts after World War II of several countries to identify and to compare their stochastic structures. The stochastic structures that this paper entertains are three structural time series models, a local level with a random walk model, a fixed local linear trend model and a local linear trend model. The structural time series models assume that a time series can be formulated directly with the unobserved components such as trend, slope, seasonal, cycle and daily effect. Random effect of each unobserved component is characterized by its own stochastic structure and a distribution of its irregular component. The structural time series models use the Kalman filter to estimate unknown parameters of a stochastic model, to predict future data, and to do filtering data. This paper identifies the best-fitted stochastic model for three types of death counts (Female, Male and Total) of each country. Two diagnostic procedures are used to check the validity of fitted models. Three criteria, AIC, BIC and SSPE are used to select the best-fitted valid stochastic model for each type of death counts of each country.

• Korean Institute of Interior Design Journal
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• v.20 no.6
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• pp.262-271
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• 2011

The purpose of this study was to classify types of family visitors' behaviors more concretely, which could be useful in planning of exhibition spaces in a science museum, with given priority to their behaviors according to interaction between them, and to understand characteristics of the behaviors. With this view, the scope of this study was restricted to subjects, who were family visitors of Gwacheon National Science Museum, consisting of parents and their one elementary school child per family unit. For understanding their behaviors, itinerary tracking and observation method of behavior were conducted. Moreover, for understanding substantial types and characteristics of family visitors' behaviors, multivariate analysis was applied. Accordingly, the results of the study are as follows. First, as a result of factor analysis, two main factors were derived. In other words, they were 'Durability of viewing' as the first and 'Interactivity between family members' as the second, which were shown valid in classification of the types of their behaviors. Second, according to the factors derived, the types of their behaviors were classified into in-depth cooperative viewing, selective independent viewing, interest concentration child-led viewing and consideration parent-led viewing. They were shown valid in topological localization and classification, as a result of analysis of the main factors. Third, in view of common characteristics of the types, it is judged that active orientation prior to regular viewing could encourage visitors coming to the museum for the first time to feel more friendly to unfamiliar exhibition environments, during the initial seek time, and to reduce visual supersaturation. Fourth, it is judged that distributed arrangement of exhibits, which result in continuous standby, could avoid confused visitor circulation by the estimated time required for viewing.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.21 no.1
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• pp.37-42
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• 2015

Background: This study investigates the impact of the cervical musculoskeletal intervention on post-traumatic stress disorder patient's cervical pain levels and depression factor. Methods: Thrty neck pain patients diagnosed with post-traumatic stress disorder were enrolled. Neck exercise training using a sling system was applied to the experimental group and self-neck movement exercise, modification of the McKenzie exercise, was applied to the control group. Both groups were checked every week whether they performed or not. Both groups performed their exercise for 35 minutes for a time and 3 times per week. Total period of the intervention was 6 weeks. To compare the effects of interventions, threshold of cervical tenderness and depression level were measured before and after the each intervention and also measured at follow-up. Results: Painthreshold of left trapezius showed a significant difference between two groups at three points. It increased 19.71% in the experimental group after the intervention compared to before the intervention. At follow-up it also increased 20.06% in the experimental group. Pain threshold of right trapezius showed a significant difference at three points. It increased 18.35% in the experimental group after the intervention compared to before the intervention. At follow-up it also increased 15.93% in the experimental group. According to the result interaction between groups and measurement time in both side of trapezius was valid. Depression level showed significant difference in the experimental group between three points. It decreased 18.07% after the intervention compared to before the intervention and decreased 15.21% at follow-up. According to the result interaction between groups and measurement time in depression level was valid. Conclusions: This study has important implications as the therapeutic strategy, high potent of improving symptoms, shows effect to a subject who has psychological problem such as posttraumatic stress disorder (PTSD).

• Journal of The Korean Association For Science Education
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• v.15 no.1
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• pp.92-103
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• 1995

Since the late of 1960,s, the improvement of science inquiry skills has been one of the most important goals in secondary science education. To achieve this goal, it is essential to develop a valid and reliable instrument for evaluating science inquiry skills. The purpose of this study is to develop a valid and reliable instrument for evaluating science inquiry skills for high school students. The instrument is developed through R & D procedure, which includes two field trials of the instrument. This study has formed a clear definition of the elements of science inquiry skills (formulating a hypothesis, controlling variables, designing an experiment, numeric calculation, graphing experimental data, inference, determining relationship, determining causalities, predicting experimental results , drawing a conclusion, formulating a generalization or model), and established the goals of assessment and developed the items of assessment. The instrument, Test of Earth Science Inquiry Skills, consists of 33 items which measure 11 science inquiry skills. There are content-free items for each science inquiry skills. This study has selected 11 science inquiry skills which are considered appropriate for being evaluated by paper-and-pencil test with SIEI (Hur,1984). The content validity of items, objectivity of the scoring keys and clarity of the items were checked by six experienced specialists in science education. At the same time, the two field trials has been executed and produced the reliability of the instrument, item difficulty index, and the effectiveness of distracters. The first field trial was performed using a sample of 304 high school students, and the second one using a sample of 872 high school students. Because the content validity is 84 % and the reliability (K-R 20) is 0.84, the developed instrument in this study is considered valid and reliable. The difficulty index is 49.4 %, answer ratio 59.1 %, the discrimination index 0.47 and the effectiveness of distracters evenly distributed, which also suffice the criteria of good instrument. The developed instrument in this study can diagnosis the well-developed science inquiry skills and the ill-developed science inquiry skills of the students, and trace the degree of the improvement of science inquiry skills.