• International Journal of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.203-210
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• 2023

In this paper, we develope a stock trading system that automatically buy and sell stocks in Kiwoom Securities' HTS system. The system is made by using Kiwoom Open API+ with the Python programming language. A trading strategy is based on an enhanced system query method called a Condition-Search. The Condition-Search script is edited in Kiwoom Hero 4 HTS and the script is stored in the Kiwoom server. The Condition-Search script has the advantage of being easy to change the trading strategy because it can be modified and changed as needed. In the HTS system, up to ten Condition-Search scripts are supported, so it is possible to apply various trading methods. But there are some restrictions on transactions and Condition-Search in Kiwoom Open API+. To avoid one problem that has transaction number and frequency are restricted, a method of adjusting the time interval between transactions is applied and the other problem that do not support a threading technique is solved by an IPC(Inter-Process Communication) with multiple login IDs.

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.4
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• pp.13-20
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• 1980

The integral equation method to solve the boundary-value problem of a 2-dimensional body oscillating in the presence of a free surface generally breaks down at and near irregular frequencies due to the hypothetical flow inside the body. In this paper singularity distributions were extended to an inner free surface to remove the irregular frequency as Ohmatsu's work in 1978, and the solution for the above problem was found by using stream function. For various bodies including Lewis form cylinders, the hydrodynamic forces were calculated numerically at various wave numbers. From the results we concluded that the irregular frequencies can be removed even for the Lewis form cylinder as Ohmatsu done for circular cylinders, and calculated hydrodynamic forces by the present method are little higher than those of Ohmatsu's when the singularities are put on the inner free surface of the body. We specially point out that the solution for heaving motion converges in an oscillatory manner but not for swaying and rolling motions.

• The Journal of the Acoustical Society of Korea
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• v.31 no.1
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• pp.19-28
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• 2012

The time-domain solution from the Kirchhoff integral equation for an exterior problem is not unique at certain eigen-frequencies associated with the fictitious internal modes as happening in frequency-domain analysis. One of the solution methods is the CHIEF (Combined Helmholtz Integral Equation Formulation) approach, which is based on employing additional zero-pressure constraints at some interior points inside the body. Although this method has been widely used in frequency-domain boundary element method due to its simplicity, it was not used in time-domain analysis. In this work, the CHIEF approach is formulated appropriately for time-domain acoustic boundary element method by constraining the unknown surface pressure distribution at the current time, which was obtained by setting the pressure at the interior point to be zero considering the shortest retarded time between boundary nodes and interior point. Sound radiation of a pulsating sphere was used as a test example. By applying the CHIEF method, the low-order fictitious modes could be damped down satisfactorily, thus solving the non-uniqueness problem. However, it was observed that the instability due to high-order fictitious modes, which were beyond the effective frequency, was increased.

• Journal of Technology Innovation
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• v.25 no.4
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• pp.189-209
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• 2017

Financial institutions around the world, including financially advanced nations, widely operate a credit information sharing system to ease off information asymmetry between financial institutions and financial consumers. This study analyzed the credit problem data that is actually being shared among financial institutions in Korea, and classified credit problem data into three categories; Frequency, Period, Amount. In survival analysis, this study analyzed how different types of credit problem influence on survival period of companies. Next, in comparative analysis, this study verified a difference between start-up companies and existing companies on classified conditions of the credit problems. After conducting a survival and comparative analysis of the credit information of 449,579 companies of 8 years' actual information sharing in Korea, it showed that the number of the frequency of accidents showed a positive(+) correlation with the survival period. This provides contrary evidence to the financial institutions' risk policies that the number of the frequency of accidents is a negative factor. Furthermore, since the start-up companies that are under 7 years old show more positive aspect in the survival period than existing companies, it draws a policy implication that the credit information sharing system need to be improved by taking account of characteristics of the start-up companies.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.8 no.2
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• pp.199-206
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• 1997

Object：The purpose of this study was to investigate frequency and risk factor of violence toward parents seen in adolescents. We also want to apply this data toward developing a prevention program for adolescent violence. Method：A total of 1,345 students from 5 middle schools in Seoul, participated in this study：675 males, 670 females. We administered self-reporting questionnaire including violence toward parents, exposure to violence, family history of alcoholism, substance abuse of adolescetnt and dermographic data etc. Result：The frequency of boys’ violence toward parent was 2.8%, which was significantly higher than girls’(p<0.001). The frequency of violence toward the father was higher than the mother. The risk factors for violence toward parents were sex, parental alcohol problem, adolescent alcohol-smoking-drug problem, exposure to violence at home in the last year and exposure to violence in the life(p<0.0001). The grade, punishment, socioeconomic status, educational level of parent were not significantly related to violence toward parents. Conclusion：These suggest that adolescent violence toward parents is not rare problem any more and preventive intervention is needed for high-risk groups, that is related with experience domestic violence, substance abuse, alcoholic parent.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.5
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• pp.197-206
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• 2014

Motor imagery based Brain-computer Interface(BCI), which has recently attracted attention, is the technique for decoding the user's voluntary motor intention using Electroencephalography(EEG). For classifying the motor imagery, event-related desynchronization(ERD), which is the phenomenon of EEG voltage drop at sensorimotor area in ${\mu}$-band(8-13Hz), has been generally used but this method are not free from the performance degradation of the BCI system because EEG has low spatial resolution and shows different ERD-appearing band according to users. Common spatial pattern(CSP) was proposed to solve the low spatial resolution problem but it has a disadvantage of being very sensitive to frequency-band selection. Discriminative filter bank common spatial pattern(DFBCSP) tried to solve the frequency-band selection problem by using the Fisher ratio of the averaged EEG signal power and establishing discriminative filter bank(DFB) which only includes the feature frequency-band. However, we found that DFB might not include the proper filters showing the spatial pattern of ERD. To solve this problem, we apply a band-selection process using CSP feature vectors and linear discriminant analysis to DFBCSP instead of the averaged EEG signal power. The filter selection results and the classification accuracies of the existing and the proposed methods show that the CSP feature is more effective than signal power feature.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.3-10
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• 2014

Direct conversion receiver(DCR) gets noticed for integration and cost reduction of wireless communication systems instead of the heterodyne receiver which uses complex filter. But DCR has several factors in performance degradation. One of them is I/Q imbalance phenomenon, that is amplitude and phase mismatch between real and imaginary part of receiver. Accordingly, researches are being carried to improve the I/Q imbalance problem. However, the tendency of the broaden bandwidth of communication systems, low pass filter(LPF) mismatch problem affects severely in I/Q mismatch phenomenon at the DCR. To study this problem, we generated 10MHz broadband signal and shifted it ${\pm}8MHz$ from the center frequency. The signal is affected by LPF mismatch and it appears as frequency selective distortion. Thus, LPF mismatch model is added to I/Q imbalance model which conventionally dealt with amplitude and phase mismatches. In addition, we proposed the compensation method for each factors of mismatch. As the simulation results, the proposed I/Q mismatch compensator resolves the frequency selective distortion which occurred by the existing LPF mismatch.

• Journal of Communications and Networks
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• v.5 no.4
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• pp.319-327
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• 2003

We consider the problem of low-sampling rate high-resolution channel estimation and timing for digital ultrawideband (UWB) receivers. We extend some of our recent results in sampling of certain classes of parametric non-bandlimited signals and develop a frequency domain method for channel estimation and synchronization in ultra-wideband systems, which uses sub-Nyquist uniform sampling and well-studied computational procedures. In particular, the proposed method can be used for identification of more realistic channel models, where different propagation paths undergo different frequency-selective fading. Moreover, we show that it is possible to obtain high-resolution estimates of all relevant channel parameters by sampling a received signal below the traditional Nyquist rate. Our approach leads to faster acquisition compared to current digital solutions, allows for slower A/D converters, and potentially reduces power consumption of digital UWB receivers significantly.

• International Journal of Control, Automation, and Systems
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• v.6 no.6
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• pp.948-953
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• 2008

In high dynamic situations, the GPS carrier tracking loop requires a wide bandwidth to track a carrier signal because the Doppler frequency changes more rapidly with time. However, a wide bandwidth allows noises within the bandwidth of the tracking loop to pass through the loop filter. As these noises are used in the numerical controlled oscillator(NCO), the carrier tracking loop of a GPS receiver shows a degraded performance in high dynamic situations. To solve this problem, an adaptive two-stage Kalman filter, which offers the NCO a less noisy phase error, can be used. This filter is based on a carrier phase dynamic model and can adapt to an incomplete dynamic model and a quickly changed Doppler frequency. The performance of the proposed tracking loop is verified by several simulations.

• Journal of Korean Port Research
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• v.14 no.3
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• pp.373-378
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• 2000

Oil spill in sea water is the most frequent and significant problem of marine pollution. As an early detection sensor of the pollution, an activated carbon coated quartz crystal is prepared and examined for its performance of detection sensitivity and stability. Powdered activated carbon and phenol resin is coated on the surface of the sensor and the sensor is baked for an hour. Adsorption of acetone dissolved in water and salt water is measured using frequency shift of quartz crystal at different concentrations of solute material. The outcome indicates that the sensor preparation is adequate and the measurement of solute concentration is stable and sensitive enough to be implemented on the monitoring of solute concentration is stable and sensitive enough to be implemented in the monitoring of organic pollution of sea water.