• The Journal of the Korea institute of electronic communication sciences
• /
• v.16 no.1
• /
• pp.125-134
• /
• 2021

With the rapid development of the film industry, the number of films is significantly increasing and movie recommendation system can help user to predict the preferences of users based on their past behavior or feedback. This paper proposes a movie recommendation system based on the latent factor model with the adjustment of mean and bias in rating. Singular value decomposition is used to decompose the rating matrix and stochastic gradient descent is used to optimize the parameters for least-square loss function. And root mean square error is used to evaluate the performance of the proposed system. We implement the proposed system with Surprise package. The simulation results shows that root mean square error is 0.671 and the proposed system has good performance compared to other papers.

• Journal of the Korean Professional Engineers Association
• /
• v.22 no.2
• /
• pp.19-25
• /
• 1989

Utilizing a cosine transform in image compression has several recognized performance benefits, resulting in the ability to attain large compression ratio with small quality loss. Also, various models incorporating Human Visual System (HVS) to Discrete Cosine Trans-form (DCT) scheme are considered. Using the exact frequency components of DCT basis function, the optimum modulation transfer function (MTF) is obtained analytically. The errors at a block boundary which is important factor in transform coder are criteria for error measurement. The HVS weight coding results in perceptually higher quality images compared with the unweighted scheme.

• Proceedings of the IEEK Conference
• /
• 2001.06a
• /
• pp.405-408
• /
• 2001

In this paper, we design tracking filter that get frequency range from 30 to 88 ［MHz］ for FH/BFSK communication system. This filter use for switching componet BJT. as result, This tracking filter has a insertion loss of 0.77~1.93［dB］. And it has a cutoff characteristic 30/3［dB］ shape factor of 3.9~6.2［dB］. The tracking filter satisfy its specification

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2006.11a
• /
• pp.387-392
• /
• 2006

A small supersonic wind tunnel was designed and built to study the flow characteristics of a supersonic impulse turbine cascade. Experiments are performed to find flow characteristics of supersonic turbine with the cascade positions and to find factor of expansion loss. The supersonic cascade with a 2-dimensional supersonic nozzle was tested with the cascade positions. Firstly, the flow was visualized by Z-type Schlieren system. Finally, highly complicated flow patterns including shocks, nozzle-cascade interaction and shock boundary layer interactions, flow characteristics of the supersonic turbine were observed.

• Proceedings of the KIEE Conference
• /
• 1999.07c
• /
• pp.1183-1185
• /
• 1999

The basic purpose of economic dispatch problem is that minimize fuel cost with inequality constraint of generator output. To solve this problem it is very important to express power loss equation that have quadratic function of generator output power included B-coefficient. This Paper presents a method in determining B-coefficient by use A-matrix that is calculated by loss re-distribution algorithm (LRDA) considering voltage dependent load model (VDLM)s. The Proposed algorithm is tested with IEEE 6 bus sample system, which shows the result in each cases by the change of load component factor.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.25 no.6
• /
• pp.490-495
• /
• 2020

The power loss of large-capacity systems using single-phase inverters has attracted considerable attention. In this study, optimal switching sequence model prediction control at a low switching frequency is proposed to reduce the power loss in a high-power inverter system, and a compensation method that can be utilized for model prediction control is developed to reduce errors in accordance with sampling values. When a three-level, single-phase inverter using a switching frequency of 600 Hz and a sampling frequency of 12 kHz is adopted, the power factor is improved from 0.95 to 0.99 through 3 kW active power control. The performance of the controller is also verified.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.17 no.10
• /
• pp.2273-2280
• /
• 2013

This article introduces the next-generation air surveillance system and investigates how to design of front-end low noise amplifier of the ground station receiver. In consideration of the international standard documentation and the performance of existing products, the study conducts the link budget on the entire system so that it can be competitive in terms of receive sensitivity or reliability. To obtain a proper low noise amplifier, standards of design are decided so that such factors as gain, gain flatness, and reflective loss can be optimal. In its design, the bias circuit appropriate for the characteristics of low power, low noise, or high gain was built, and according to the results of the simulation conducted after the optimal design, its gain was 16.24dB, noise factor was 0.36dB, input-output reflective loss was -18dB and -28dB each, and frequency stability was 1.11. According to the results measured after the design, its gain was 17dB, noise factor was 0.51dB, gain flatness was 0.23dB, and input-output reflective loss was -18.28dB and -24.50dB each, so the results gained were suitable for building the overall system.

• Journal of Korea Society of Industrial Information Systems
• /
• v.24 no.2
• /
• pp.57-63
• /
• 2019

In order to facilitate the supply of gradually increasing power demand, it is also necessary to increase the number of power cables for power transmission as well as generation facilities. However, the expansion of electric power cables for supplying power to most urban areas requires a space for installation of additional cables, and the space for installing cables in domestic downtown areas is insufficient at present. The superconducting power cable, which can transmit more power with the same size, has emerged as an alternative to overcome the insufficient cable installation space. However, superconducting power cables, which have the advantage of large power transmission, have some losses in the AC (Alternating Current) system. Therefore, the design and analysis of AC losses are essential to introduce superconducting power cables in AC power transmission systems. In this paper, we analyze the AC loss of various superconducting power cables and consider the actual superconducting power cables and their application to the system. Although there is a theoretical calculation method of AC loss for single superconducting wire, it is not easy to calculate AC loss of superconducting power cable with large number. Therefore, the authors intend to analyze various kinds of superconducting power cable AC loss by using electromagnetic finite element analysis considering E-J (Electric field-Current density) characteristics of superconductivity. The analysis of the AC loss characteristics of the superconducting power cable will be an important factor in the design and development of the superconducting power cable to be applied to the actual system.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.20 no.2
• /
• pp.72-78
• /
• 2021

This paper proposes a wide-band dual-polarization stacked patch array antenna for satellite SAR system applications. The array antenna was designed for loss minimization and wide-band characteristics to enhance the performance of the SAR system and optimize it for active return loss in applications to active phased arrays. The fabricated array antenna showed a performance of 19.26%/19.79% fractional bandwidth within the -10 dB reference level of the active return loss and showed loss characteristics of 0.797 dB/0.799 dB averaged within the operational frequency for both H/V-polarization cases. The pattern performance was verified by comparing the measured patterns with the calculated patterns obtained by the array factor.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.05d
• /
• pp.38-42
• /
• 2003

The use of VPI impregnated mica tape as high voltage insulation for large rotating electric machines requires a careful balance of processes and materials to obtain the desired electrical, mechanical and thermal characteristics. The stator insulation systems such as epoxy bonded high voltage mica tape have been produced for many years. One such system employing an epoxy and anhydride impregnating resin developed by Hyundai Heavy Industries, Co. (hereafter, HHI), to satisfy customer requests for an epoxy bonded insulation system. HHI applies the following electrical and thermal evaluations such as dielectric breakdown, voltage endurance, dissipation factor vs. temperature, isothermal weight loss, and so on. A detailed laboratory evaluation can describe specific physical limitations for an insulation system and permit development of long-term operation guidelines that permit full utilization of the proposed system. HHI has found these evaluations very helpful in qualifying insulation system for the repair of both large motors and generators.