• Journal of Construction Engineering and Project Management
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• v.8 no.1
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• pp.10-21
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• 2018

Many construction projects involve a plethora of safety-related problems that can cause loss of productivity, diminished revenue, time overruns, and legal challenges. Incorporating data collection and analytics methods can help overcome the root causes of many such problems. However, in a dynamic construction workplace collecting data from a large number of resources is not a trivial task and can be costly, while many contractors lack the motivation to incorporate technology in their activities. In this research, an Android-based mobile application, Preemptive Construction Site Safety (PCS2) is developed and tested for real-time location tracking, trajectory prediction, and prevention of potential collisions between workers and site hazards. PCS2 uses ubiquitous mobile technology (smartphones) for positional data collection, and a robust trajectory prediction technique that couples hidden Markov model (HMM) with risk-taking behavior modeling. The effectiveness of PCS2 is evaluated in field experiments where impending collisions are predicted and safety alerts are generated with enough lead time for the user. With further improvement in interface design and underlying mathematical models, PCS2 will have practical benefits in large scale multi-agent construction worksites by significantly reducing the likelihood of proximity-related accidents between workers and equipment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.3
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• pp.353-358
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• 1998

This paper presents development of a LNA operating at 1.71 ∼ 1.18 GHz used for a receiver of KOREA PCS base station and transponder. Using resistive decoupling circuits, a signal at low frequency is dissipated by a resistor. This design method increases the stability of the LNA and suitable for input stage matching. The LNA consists of low noise GaAs FET ATF-10136 and internally matched VNA-25. The LNA is fabricated with both the RF circuit and the self-bias circuits in aluminum housing. As a result, the characteristics of the LNA implemented here shows 30 dB in gain and 0.85 dB in noise figure.

• Proceedings of the KIEE Conference
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• summer
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• pp.1477-1479
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• 2004

Increasing numbers of photovoltaic arrays are being connected to the power utility through the power conditioning systems (PCS). This has raised potential problems of network protection. If, due to the action of the PCS, the local network voltage and frequency remain within regulatory limits when the utility is disconnected, then islanding is said to occur. In this paper, the representative methods to prevent the islanding are described and a PSIM-based model and analysis of the reactive power variation (RPV) method are presented. A novel phase detector using the all-pass filter and digital phase locked loop (DPLL) is proposed especially for the single-phase PCS. Finally, this paper provides the simulation and experimental results with a single-phase 3kW prototype PCS. Islanding test method of IEEE Std. 929-2000 was performed for verification.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.230-231
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• 2007

계통연계형 태양광 시스템을 구성하고 있는 전력변환장치인 PCS(power conditioning system)는 일반적으로 그 내부에 입력전력 평활용 Capacitor, DC-DC Converter, DC link Capacitor, DC-AC Inverter 및 L-C Filter 등으로 구성된다. 이러한 태양광 시스템의 구성은 주로 태양광 어레이와 PCS의 DC-DC Converter 및 DC-AC Inverter의 수와 연결 방법에 따라 여러 가지로 구성할 수가 있다. 본 논문에서 제안할 시스템의 구성은 하나의 태양광 어레이를 다수의 계통 연계형 태양광 PCS가 공유하는 형태인데, 이러한 시스템의 주요 장점은 첫째, 일사량에 따라 각각의 PCS가 모두 정격에서 운전하도록 하여 변환효율을 개선할 수 있다는 점과 둘째, 태양광 어레이의 용량 확장에 따른 PCS 장치의 용이한 확장성 그리고 셋째, 연결되어 있는 다수의 PCS 중 하나의 태양광 PCS가 고장으로 인하여 유지 및 보수가 필요할 때에도 그 외의 다른 정상적인 태양광 PCS는 지속적인 발전이 가능한 장점 등을 갖는다. 본 논문에서는 태양광 어레이의 출력을 공유하는 병렬운전용 태양광 PCS의 구성에 대하여 연구하고, 그 병렬운전기법을 제시하여 이에 대한 타당성을 시뮬레이션으로 검증하고자 한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1174-1180
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• 2018

In December 2017, the government announced plans to increase the current proportion of renewable energy from 7% to 20% by 2030 through a plan called the Renewable Energy 3020 Implementation Plan. Therefore, the demand for installation of photovoltaic(PV), wind turbine(WT) and battery energy storage system(BESS) is expected to increase. In particular, the system combined with energy storage system(ESS) is expected to take up a large portion since PV and WT can receive high renewable energy certificates(REC) weights when combined with ESS. In this study, we calculate the optimal capacity of the power conditioning system(PCS) and the BESS by comparing the economical efficiency and maximize the efficiency of the PV-BESS system in which the PV and the BESS are connected. By analyzing the system marginal price(SMP) and REC, it maximize profits through application of REC weight 5.0 and optimal charge-discharge scheduling according to the SMP changes.

• Journal of the Korean Solar Energy Society
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• v.31 no.2
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• pp.22-30
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• 2011

In recently, inductor and transformer is the common device using widely in the photovoltaic system and power electronics. Therefore, each inductor and transformer has different core loss and iron loss depending on the size and kinds of core materials, it is important to analyze loss characteristics for better transformer efficiency. This paper offers an efficiency calculation method for PCS inductor and transformer loss, and different kinds of core materials are analyzed for optimized PCS design.

• Korean Journal of Materials Research
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• v.26 no.6
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• pp.337-341
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• 2016

Cu-30 vol% SiC composites with relatively densified microstructure and a sound interface between the Cu and SiC phases were obtained by pressureless sintering of PCS-coated SiC and Cu powders. The coated SiC powders were prepared by thermal curing and pyrolysis of PCS. Thermal curing at $200^{\circ}C$ was performed to fabricate infusible materials prior to pyrolysis. The cured powders were heated treated up to $1600^{\circ}C$ for the pyrolysis process and for the formation of SiC crystals on the surface of the SiC powders. XRD analysis revealed that the main peaks corresponded to the ${\alpha}$-SiC phase; peaks for ${\beta}$-SiC were newly appeared. The formation of ${\beta}$-SiC is explained by the transformation of thermally-cured PCS on the surface of the initial ${\alpha}$-SiC powders. Using powder mixtures of coated SiC powder, hydrogen-reduced Cu-nitrate, and elemental Cu powders, Cu-SiC composites were fabricated by pressureless sintering at $1000^{\circ}C$. Microstructural observation for the sintered composites showed that the powder mixture of PCS-coated SiC and Cu exhibited a relatively dense and homogeneous microstructure. Conversely, large pores and separated interfaces between Cu and SiC were observed in the sintered composite using uncoated SiC powders. These results suggest that Cu-SiC composites with sound microstructure can be prepared using a PCS coated SiC powder mixture.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.3
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• pp.910-932
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• 1996

A problem of determining the effective conductivity of a useful model of sphere-matrix type, disordered three-phase composite media is considered. Specifically, a three-phase media in which two-phase composite spheres, consisting of spheres of conductivity $k_2$((phase 2) and concentric shells of conductivity $k_3$(phase 3), are randomly distributed in a matrix of conductivity $k_1$( (phase 1) is considered. As for the structure models configuring three-phase composite media, three different structure models of PCS, PS-1 and PS-2 models are defined, which are analogous to well-established PCS, PS structure models of two-phase composite media. Futhermore, a generalized PS-PCS structure model is proposed to incorporate thesee three different models in one. Effective condectivity $k^{\ast}$of multiphaes composite media is greatly influenced by the phase connectivity of each disspersed phase material, as well as phase conductivities and phase volume fractions. Phase connectivity of three-phase PCS, PS-1, PS-2 composite media is quantified by the impentrability parameter $\lambda$. Mathematically rigorous first-order cluster bounds on $k^{\ast}$ are derived for these models of three-phase composite media, and as computation examples, first-order cluster bounds on $k^{\ast}$ for three-phase composites consisting of largely different phase conductivities are computed and compared as function of concnectivity parpmeter $\lambda$. Results and discussions are given.

• The Journal of Fisheries Business Administration
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• v.15 no.1
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• pp.58-80
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• 1984

The classification of islands is prerequisite for establishing a development policy to vitalize many-sided function of islands. We try to classify the 440 inhabited islands which exist in Jeon-Nam area and Kyong-Nam area by means of PCA. PCA begins with making correlation matrix of orignal variables. From this matrix we can comprehend the rough relationships between two variables. Next, we look for the eigenvalues which are roots of characteristic equation of correlation matrix. The number of eigenvalues is equal to that of original variables. We choose the largest eigenvalue λ$_1$among them and then look for the eigenvector of correlation matrix corresponding to the largest eigenvalue. Linear combination of eigenvector obtained above and original variables is namely first Principal Component (PC). Using an eigenvalue criterion(λ$\geq$ 1), we choose 3 PCs in Jeon-Nam area and 2 PCs in Kyong-Nam area. But we decide to consider only two PCs in both areas to faciliate a comparative analysis. Now, loss of information is 31.7% in Jeon-Nam area and 26.64% in Kyong-Nam area. PCs extracted by preceding procedure have characteristics as follows. The first PC relates to aggregate size of islands in case of both areas. The second PC relates to income per household, factors of agricultural production and factors of fisheries production in Jeon-Nam area, but in Kyong-Nam area it means distance from island and income per household. A classification of islands can be attained by plotting component scores of each island in graph used two PCs as axes and grouping similiar islands. 6 groups are formed in Jeon-Nam area and 5 groups in Kyong-Nam area. The result of this study in kyong-Nam area accords with prior result of study.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.71-78
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• 2015

Since most education organizations such as Universities have a plenty of PCs, much electric power can be wasted if their power states are not managed properly. This paper introduces the RPM(Remote Power Management) software system implemented to reduce a waste of PC power in Universities. The System manager can monitor power state of all PCs in a University and turn off PCs or change power states of PCs to low power states. The RPM consists of three software modules. First, Power Controller, which is installed in each user PC, saves the power by changing low power state by utilizing low power algorithm proposed in this paper. Also it reports power state of its PC to Power Server on the state changed. Second, Power Server module gathers power state information of all PCs, stores them in a DB, and sends all or some parts of the information to Power Viewer whenever the manager asks. The manager can turn off or change a certain PC to low power state. We evaluated the performance of power saving for the RPM and the result showed achievement of 40% power saving.