• The Journal of Korean Institute for Practical Engineering Education
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• v.1 no.1
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• pp.7-12
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• 2009

The worldwide spread of the internet has made it an important topic in our everyday lives. It has not only changed ordinary lives, but also the whole spectrum of modern society. Thus, it is necessary to understand the characteristic changes in learners as well as social demand in this drastic transformation period and to modify the goal and methods of learning to nurture future intellects. To achieve this, there have been recent attempts to invent new learning methods involving Web 2.0, which focuses on the user. Out of the various aspects of Web 2.0, the blog is expected to invoke learner-oriented education and active discussions between learners, in that the individual manages the blog autonomously and there is much interaction between users. This study will construct a learning system using the blog, apply it on real learners, and analyze its effect on the learners' scholastic achievements, interests, and learning transfer.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2087-2089
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• 2003

The presence of narrowband interference (NBI) in Direct-sequence code division multiple access (DS/CDMA) systems is an inevitable problem when the interference is strong enough. The improvement in the system performance employs by adaptive narrowband interference suppression techniques. Basically there have been two types of method for narrowband interference suppression estimator/subtracter approaches and transform domain approaches. In this paper the focus is on the type of estimator/subtracter approaches. However, the binary direct sequence (DS) signal, that acts as noise in the prediction process is highly non-Gaussian. The case of a Gaussian interferer with known in an autoregressive (AR) signal or a digital signal and also in a sinusoidal signal (Tone) that included in is paper. The proposed NBI suppression is presence in an adaptive IIR notch filter for lattice structure and more powerful by using a variable step-size algorithm. The simulation results show that the proposed algorithm can significantly increase the convergence rate and improved system performance when compare with adaptive least mean square algorithm (LMS).

• Journal of Digital Convergence
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• v.16 no.9
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• pp.405-412
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• 2018

When a film company decides whether to invest or not in a scenario is the appropriate time to predict box office success. In response to market demands, AI based scenario analysis service has been launched, yet the algorithm is by no means perfect. The purpose of this study is to present a prediction model of movie scenario's box office hit based on human brain processing mechanism. In order to derive patterns of visual, auditory, and cognitive stimuli on the time spectrum of box office animation hit, this study applied Weber's law and brain mechanism. The results are as follow. First, the frequency of brain stimulation in the biggest box office movies was 1.79 times greater than that in the failure movies. Second, in the box office success, the cognitive stimuli codes are spread evenly, whereas in the failure, concentrated among few intervals. Third, in the box office success movie, cognitive stimuli which have big cognition load appeared alone, whereas visual and auditory stimuli which have little cognitive load appeared simultaneously.

• 전자공학회논문지 IE
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• v.47 no.2
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• pp.60-65
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• 2010

In this paper, we propose a dual-band filtering method optimized to DBO-CSS systems which are alternatively transmitted in low and high bands. The conventional channel filter which passes entire signal bandwidth causes a problem that excessive noise in neighboring sub-band is added while one of signals in two sub-bands is received. The dual-band filtering proposed in this paper can overcome the performance degradation in the conventional filtering method without increase of hardware complexity. The proposed method is based on two filters to be matched with DBO-CSS signals receiving alternatively and can exclude the undesired noise in neighboring sub-band. Simulation results for the proposed method show better performance about 2.5dB than the conventional one.

• Publications of The Korean Astronomical Society
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• v.15 no.spc2
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• pp.21-25
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• 2000

The ionosphere, the atmosphere of the earth ionized by solar radiations, has been strongly varied with solar activity. The ionosphere varies with the solar cycle, the seasons, the latitudes and during any given day. Radio wave propagation through or in the ionosphere is affected by ionospheric condition so that one needs to consider its effects on operating communication systems normally. For examples, sporadic E may form at any time. It occurs at altitudes between 90 to 140 km (in the E region), and may be spread over a large area or be confined to a small region. Sometimes the sporadic E layer works as a mirror so that the communication signal does not reach the receiver. And radiation from the Sun during large solar flares causes increased ionization in the D region which results in greater absorption of HF radio waves. This phenomenon is called short wave fade-outs. If the flare is large enough, the whole of the HF spectrum can be rendered unusable for a period of time. Due to events on the Sun, sometimes the Earth's magnetic field becomes disturbed. The geomagnetic field and the ionosphere are linked in complex ways and a disturbance in the geomagnetic field can often cause a disturbance in the F region of the ionosphere. An enhancement will not usually concern the HF communicator, but the depression may cause frequencies normally used for communication to be too high with the result that the wave penetrates the ionosphere. Ionospheric storms can occur throughout the solar cycle and are related to coronal mass ejections (CMEs) and coronal holes on the Sun. Except the above mentioned phenomena, there are a lot of things to affect the radio communication. Nowadays, radio technique for probing the terrestrial ionosphere has a tendency to use satellite system such as GPS. To get more accurate information about the variation of the ionospheric electron density, a TEC measurement system is necessary so RRL will operate the system in the near future.

• Research in Plant Disease
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• v.9 no.2
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• pp.57-63
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• 2003

Clubroot disease of curcifer crops caused by Plasmodiophora brassicae had been first reported in 1928 in Korea, and maintained mild occurrence until 1980s. Since 1990s the disease has become severe in alpine areas of Kyonggi and Kangwon, gradually spread to plain fields throughout the country, and remains as the great-est limiting factor for its production. Researches on the disease has begun in late 1990s after experiencing severe epidemics. Survey of occurrence and etiological studies have been carried out, particularly, on the pathogen physiology, race identification, quantification of soil pathogen population, and host spectrum of the pathogen. Ecology of gall formation and its decay, yield loss assessment associated with time of infection, and relationships between crop rotation and the disease incidence was also studied during late 1990s. In studies of its control, more than 200 crucifer cultivars were evaluated for their resistance to the disease. Lime applica-tion to field soil was also attempted to reduce the disease incidence. Resistant radish and welsh onion were recommended as rotation crops with crucifers after 3-year field experiments. However, so for, most studies on clubroot disease in Korea have been focused on chemical control. Two fungicides, fluazinam and flusulfamide, were selected and extensively studied on their application technologies and combination effects with lime application or other soil treatment. To develop environmentally-friendly control methods, solar-disinfection of soil, phosphoric acid as a nontoxic compound, and root-parasiting endophytes as biocontrol agents were examined for their effects on the disease in fields. In the future, more researches are needed to be done on development of resistant varieties effective to several races of the pathogen, establishment of economically-sound crop rotation system, and improvement of soil-disinfection technique applicable to Korean field condi-tion, and development of methodology of pretreatment of fungicides onto seeds and seedbeds.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.3
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• pp.215-226
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• 1999

The experimented rangefinder consist of sets of V/A-Code GPS and sets of L1 C/A-code & carrier phase receivers connected by two spread spectrum radio modems in order to measure relative range and bearing between two ship antennas by real time, comparing and analyzing accuracy of both GPS receivers at the fix point on the land by means of executing zero baseline test by C/A code and by carrier phase as well as measuring distance range 5m, 10m, 15m between each other receivers. The results from the measurement of relative range and bearing are as follows as ;1. According to the results from zero baseline test, the average error by C/A-code receiver is less than 0.1m, which proves theories from published books but when each GPS receivers track different satellites, the range accuracy error becomes up to 100m by means of S/A. Because of this sudden wide range error, rangefinder is not appropriate at relative range measurement without additional modification of the algorism of the GPS receiver itself.2. According to relative range measurement by Carrier Phase and zero baseline test at static condition, the range error is less than 3.5cm in case that it passes more than 5 minutes after GPS sets can track simultaneously more than 6 satellites. Its main reason is understood that the phase center of antenna is bigger than geodetic antenna.3. When range measurement of two receivers from 5m, to 10m to 15m, the each range error is 0.340m, 0.190m, 0.011m and each standard variation is 0.0973m, 0.0884m, 0.0790m. The range error and standard variation are in inverse proportion to distance between two receivers. 4. L1 Carrier Phase GPS generally needs 5 minutes to fix and during this ambiguity search, the relative range and bearing angle is shown to be various.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.5
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• pp.408-417
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• 1996

In this paper, we quantiatively analyze the broadband CDMA systems with high chip rate, which virually eliminates the multipath fading effects by distinguishing each reflected paths in the process of despreading. We model the broadband multipath propagation channel with random time-variant impulse response as a linear filter of tapped delay line to evaluate the performance of broadband CDMA systems in multipath fading environment. This statistical model, based on extensive experimental data, was established to characterize the urban radio propagation medium in various environments. We perform computer simulation of the transmission and reception of broadband CDMA systems by applying it to abve channel model. From the simulation results, we confirm that the broadband CDMA systems inherenly reduce the effects of multipath fading phenomena which causes to degrade the performance of mobile communication systems, based on the results of eye-diagram and BER curve.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.8
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• pp.710-718
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• 1991

In this pape, an analysis approach for the performance of serial search burst-format direct sequence spread-spectrum code acquisiion system using matched filter is presented. And an acquistion system using analog matched filter is analyzed by this approach. And special consideration is focused on the effect of the code autocorelation sideobes. The basic idea of thi approach is the constuction of state tansition digram at the time of random packet arrival and the calculation of the packet loss probability, which is deveoped in terms of the following parameters: the false alarm probability. the etection probability, and the probability of receiver blocking obtained from the blocked customers cleae queeing system model. The analysis results reveal that the performance of the acquisition system is degraded by the effet of the code autocorrelation sidelobes above a certain value of SN/chip.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1351-1360
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• 1999

In frequency selective channels, conventional PN code acquisition schemes are not ideal candidates. This is because they are primarily designed for the AWGN channel. In this paper, a direct-sequence spread-spectrum(DSSS) PN code acquisition system based on digital matched filtering (DMF) with automatic threshold control(ATC) algorithm is presented and analyzed with regards to probability of detection and probability of false alarm. These two important probabilities, the probability of detection ($P_D$) and the probability of false alarm ($P_{FA}$) are derived and analyzed in considering Doppler shift, sampling rate, mean acquisition time, and PN chip rate in frequency selective Rayleigh fading channel when using serial-search method as detection technique. From computer simulation results of a DMF acquisition system model, it is shown that the performance of the acquisition system using ATC algorithm is better than that of constant threshold system.