• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.58-62
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• 2010

This paper presents the effects of RF performance parameters on the Galileo receiver design via simulation after reviewing the requirements of the Galileo receiver structure. At first, we considered the general requirements, structure and characteristics of the Galileo system. Then we designed the Galileo receiver focused on performance requirement of 16 dB C/N which is equal to 15 % Error Vector Magnitude(EVM) by using Advanced Design System(ADS) simulation program. In order to verify the function of Automatic Gain Control(AGC)), we measured the IF output power level by changing the input power level at the front - end of the receiver. We analyzed the performance degradation due to phase noise variations of Local Oscillator(LO) in the Galileo receiver through EVM when the minimum sensitivity level of -127 dBm is applied at the receiver. We also analyzed the performance degradation according to variable Analog-to-Digital Converter(ADC) bits within the Dynamic range, -92 ~ -139 dBm, which has been defined by gain range (-2.5 ~ +42.5 dB) in the AGC operation. The results clearly show that the performance of the Galileo receiver can be improved by increasing ADC bits and reducing Phase Noise of LO.

• Korean Journal of Agricultural and Forest Meteorology
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• v.22 no.2
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• pp.47-56
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• 2020

Decline of pine forests happens in Korea due to various disturbances such as insect pests, forest fires and extreme climate, which may further continue with ongoing climate change. For conserving and reestablishing pine forests, understanding climate-induced future shifts of pine tree distribution is a critical concern. This study predicts future geographical distribution of Pinus densiflora, using Maximum Entropy Model (MaxEnt). Input data of the model are locations of pine tree stands and their environmental variables such as climate were prepared for the model inputs. Alternative future projections for P. densiflora distribution were conducted with RCP 4.5 and RCP 8.5 climate change scenarios. As results, the future distribution of P. densiflora steadily decreased under both scenarios. In the case of RCP 8.5, the areal reductions amounted to 11.1% and 18.7% in 2050s and 2070s, respectively. In 2070s, P. densiflora mainly remained in Kangwon and Gyeongsang Provinces. Changes in temperature seasonality and warming winter temperature contributed primarily for the decline of P. densiflora., in which altitude also exerted a critical role in determining its future distribution geographic vulnerability. The results of this study highlighted the temporal and spatial contexts of P. densiflora decline in Korea that provides useful ecological information for developing sound management practices of pine forests.

• KIPS Transactions on Software and Data Engineering
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• v.5 no.11
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• pp.593-606
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• 2016

Computer simulation is widely used in a variety of computational science and engineering fields, including computational fluid dynamics, nano physics, computational chemistry, structural dynamics, and computer-aided optimal design, to simulate the behavior of a system. As the demand for the accuracy and complexity of the simulation grows, however, the cost of executing the simulation is rapidly increasing. It, therefore, is very important to lower the total execution time of the simulation especially when that simulation makes a huge number of repetitions with varying values of input parameters. In this paper we develop a simulation service system that provides the ability to predict the result of the requested simulation without actual execution for that simulation: by recording and then returning previously obtained or predicted results of that simulation. To achieve the goal of avoiding repetitive simulation, the system provides two main functionalities: (1) storing simulation-result records into database and (2) predicting from the database the result of a requested simulation using statistical machine learning techniques. In our experiments we evaluate the prediction performance of the system using real airfoil simulation result data. Our system on average showed a very low error rate at a minimum of 0.9% for a certain output variable. Using the system any user can receive the predicted outcome of her simulation promptly without actually running it, which would otherwise impose a heavy burden on computing and storage resources.

• Journal of Korea Water Resources Association
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• v.45 no.12
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• pp.1321-1330
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• 2012

In this study, the daily inflow at the basin of Chungju dam is predicted using wavelet-artificial neural network for nonlinear model. Time series generally consists of a linear combination of trend, periodicity and stochastic component. However, when framing time series model through these data, trend and periodicity component have to be removed. Wavelet transform which is denoising technique is applied to remove nonlinear dynamic noise such as trend and periodicity included in hydrometeorological data and simple noise that arises in the measurement process. The wavelet-artificial neural network (WANN) using data applied wavelet transform as input variable and the artificial neural network (ANN) using only raw data are compared. As a results, coefficient of determination and the slope through linear regression show that WANN is higher than ANN by 0.031 and 0.0115 respectively. And RMSE and RRMSE of WANN are smaller than those of ANN by 37.388 and 0.099 respectively. Therefore, WANN model applied in this study shows more accurate results than ANN and application of denoising technique through wavelet transforms is expected that more accurate predictions than the use of raw data with noise.

• Journal of Biomedical Engineering Research
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• v.24 no.4
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• pp.319-328
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• 2003

The purpose of this paper is to develop a medical laser system using the semiconductor diode laser in order to photodynamic cancel therapy as a light source. The ideal light source for photodynamic therapy would be a homogeneous nondiverging light with variable spot size and specific wavelength with stability. After due consideration in this point, in this paper, we used a diode laser resonator of 635nm wavelength. The development laser system have a statistical laser out beam with accuracy control using the constant current control of method and clinic-friendly with compact. In order to protect the diode resonator from the over-current, the rush-current and electrical fault, we specially designed. The most importance therapeutic factor are the radiation mode for cancer therapy. So we developed the radiation mode of CW(Continuous Wave), long pulse, short pulse, and burst pulse and can adjust the exposure time from several milli-second to several minute. The experimental result shows that laser beam power was increased linear from 10mW to 300mW according to the increasing input current and the increasing exposure time. The developed new compact diode laser system have a stability of output power and specific wavelength with easy control and transportable for many applications of PDT.

• Korean Journal of Construction Engineering and Management
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• v.21 no.4
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• pp.38-49
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• 2020

As the quality of life has been improving, people are getting higher interest and higher expectation for safety. However, the accident rate at the construction site is still high. Therefore, it is urgent to secure the safety at the construction work. Due to the nature of the construction industry, construction sites are directly exposed to the external environment. The possibility of accident occurrence is increased due to various factors such as the always variable processes, the diversity of manpower input, the increase in vulnerable class, and the danger of construction equipment..Particularly, the disasters occurring at the small- or medium-sized construction sites (budget ≤ 12 billion KRW) account for 88.9% of the total disasters at construction sites (73.4% for casualty). It was due to the lack of management caused by the absence of supervisors and insufficient safety measures. Moreover, it is difficult for the small- or medium-sized construction sites to apply basic safety measures such as safety education and safety facility installation by themselves in order to prevent disasters because they don't have sufficient safety organizations. It is because they have relatively less safety personnel and poorer technology system than large-sized construction sites. Therefore, in order to reduce accidents in construction, it is necessary to prevent accidents at the small- and medium-sized construction sites. From this point of view, the objectives of this study were to identify the key risk items causing accidents frequently by analyzing the accidents at construction sites and identifying problems associated with safety management, and to secure the safety at the small- and medium-sized construction sites.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.11
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• pp.66-76
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• 2009

The motion estimation in video encoding system occupies the biggest part. So, we require the motion estimator with efficient structure for real-time operation. And for motion estimator's implementation, it is desired to design hardware module of an exclusive use that perform the encoding process at high speed. This paper proposes motion estimation detection block(MED), 41 SADs(Sum of Absolute Difference) calculation block, minimum SAD calculation and motion vector generation block based on parallel processing. The parallel processing can reduce effectively the amount of the operation. The minimum SAD calculation and MED block uses the pre-computation technique for reducing switching activity of the input signal. It results in high-speed operation. The MED and 41 SADs calculation blocks are composed of adder tree which causes the problem of critical path. So, the structure of adder tree has changed the most commonly used ripple carry adder(RCA) with carry skip adder(CSA). It enables adder tree to operate at high speed. In addition, as we enabled to easily control key variables such as control signal of search range from the outside, the efficiency of hardware structure increased. Simulation and FPGA verification results show that the delay of MED block generating the critical path at the motion estimator is reduced about 19.89% than the conventional strukcture.

• Journal of Korean Philosophical Society
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• v.139
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• pp.1-21
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• 2016

To quickly and accurately grasp the consistency and the true/false of sentence description, we may require the help of a computer. It is thus necessary to research and quickly and accurately grasp the consistency and the true/false of sentence description by computer processing techniques. This requires research and planning for the whole study, namely a plan for the necessary tables and those of processing, and development of the table of the five logic rules. In future research, it will be necessary to create and develop the table of ten basic inference rules and the eleven kinds of derived inference rules, and it will be necessary to build a DB of those tables and the computer processing of sentence logic using server programming JSP and client programming JAVA over its foundation. In this paper we present the overall research plan in referring to the logic operation table, dividing the logic and inference rules, and preparing the listed process sequentially by dividing the combination of their use. These jobs are shown as a variable table and a symbol table, and in subsequent studies, will input a processing table and will perform the utilization of server programming JSP, client programming JAVA in the construction of subject/predicate part activated DB, and will prove the true/false of a sentence. In considering the table prepared in chapter 2 as a guide, chapter 3 shows the creation and development of the table of the five logic rules, i.e, The Rule of Double Negation, De Morgan's Rule, The Commutative Rule, The Associative Rule, and The Distributive Rule. These five logic rules are used in Propositional Calculus, Sentential Logic Calculus, and Statement Logic Calculus for sentence logic.

• Journal of Korea Port Economic Association
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• v.30 no.1
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• pp.23-55
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• 2014

The purpose of this paper is to show the clustering trend and to choose the clustering ports for 3 Korean ports(Busan, Incheon and Gwangyang Ports) by using the self organizing maps based on neural network(SOM) and Tier models for 38 Asian ports during 11 years(2001-2011) with 4 input variables(birth length, depth, total area, and number of crane) and 1 output variable(container TEU). The main empirical results of this paper are as follows. First, clustering results by using SOM show that 3 Korean ports[Busan(26.5%), Incheon(13.05%), and Gwangyang(22.95%) each]can increase the efficiency. Second, according to Tier model, Busan(Hongkong, Sanghai, Manila, and Singapore), Incheon(Aden, Ningbo, Dabao, and Bangkog), and Gwangyang(Aden, Ningbo, Bangkog, Hipa, Dubai, and Guangzhou) should be clustered with those ports in parentheses. Third, when both SOM and Tier models are mixed, (1) efficiency improvement of Busan Port is greater than those of Incheon and Gwangyang ports. (2) Incheon port has shown the slow improvement during 2001-2007, but after 2008, improvement speed was high. (3) improvement level of Gwangyang port was high during 2001-2003, but after 2004, improvement level was constantly decreased. The policy implication of this paper is that Korean port policy planner should introduce the SOM, and Tier models with the mixed two models when clustering among the Asian ports for enhancing the efficiency of inputs and outputs.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.169-180
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• 2018

White light-emitting diodes (LEDs) are more economical than fluorescent lights, and provide high brightness, a high lifetime expectancy, and greater durability. As LEDs are closely connected with people's daily lives, dimming control of LED is an important component in providing energy savings and improving quality of life. In visible light communications systems using these LEDs, multiple input multiple output (MIMO) technology has attracted a lot of attention, in that it can attain the channel capacity in proportion to the number of antennas. This paper analyzes the power performance of three kinds of modulation in visible light communications (VLC) systems applied space-time block code (STBC) techniques. The modulation schemes are return-to-zero on-off keying (RZ-OOK), variable pulse position modulation (VPPM), and overlapping pulse position modulation (OPPM), and dimming control was applied. The power requirements and power consumption were used as metrics to compare the power efficiency in $2{\times}2$ STBC-VLC environments under the three kinds of modulation. We confirm that dimming control affects the communications performance of each modulation scheme. VPPM showed greater consumption among the three modulations, and OPPM showed energy savings comparable to VPPM.