• Journal of Climate Change Research
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• 제1권2호
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• pp.97-107
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• 2010

A forest project for the sequestration of carbon dioxide helps to reduce the concerntration of greenhouse gas in atmosphere and provides various co-benefits. A lot of forestry-based carbon offset programs have been developing for the purpose of CSR(Corporate Social Responsibility), voluntary GHG emission reduction, and regulatory context etc. in worldwide. We studied major characteristics - project type and criteria, additionality, credits, permanence, carbon accounting and monitoring, co-benefit - of advanced forest carbon offset programs. Also, we tried to comprehend the direction and basic elements to design a domestic program.

• Journal of Korean Neurosurgical Society
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• 제67권1호
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• pp.60-72
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• 2024

Objective : Recently, robotic-assisted spine surgery (RASS) has been considered a minimally invasive and relatively accurate method. In total, 495 robotic-assisted pedicle screw fixation (RAPSF) procedures were attempted on 100 patients during a 14-month period. The current study aimed to analyze the accuracy, potential risk factors, and learning curve of RAPSF. Methods : This retrospective study evaluated the position of RAPSF using the Gertzbein and Robbins scale (GRS). The accuracy was analyzed using the ratio of the clinically acceptable group (GRS grades A and B), the dissatisfying group (GRS grades C, D, and E), and the Surgical Evaluation Assistant program. The RAPSF was divided into the no-breached group (GRS grade A) and breached group (GRS grades B, C, D, and E), and the potential risk factors of RAPSF were evaluated. The learning curve was analyzed by changes in robot-used time per screw and the occurrence tendency of breached and failed screws according to case accumulation. Results : The clinically acceptable group in RAPSF was 98.12%. In the analysis using the Surgical Evaluation Assistant program, the tip offset was 2.37±1.89 mm, the tail offset was 3.09±1.90 mm, and the angular offset was 3.72°±2.72°. In the analysis of potential risk factors, the difference in screw fixation level (p=0.009) and segmental distance between the tracker and the instrumented level (p=0.001) between the no-breached and breached group were statistically significant, but not for the other factors. The mean difference between the no-breach and breach groups was statistically significant in terms of pedicle width (p<0.001) and tail offset (p=0.042). In the learning curve analysis, the occurrence of breached and failed screws and the robot-used time per screw screws showed a significant decreasing trend. Conclusion : In the current study, RAPSF was highly accurate and the specific potential risk factors were not identified. However, pedicle width was presumed to be related to breached screw. Meanwhile, the robot-used time per screw and the incidence of breached and failed screws decreased with the learning curve.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.385-388
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• 2000

In this paper, the Ka-band Dielectric resonator oscillator has been designed and fabricated. The resonator network was simulated using HFSS program. The design method of an oscillator is the small-signal S-parameter design. The Push-push DRO employs a hetero junction FET (NE32484A). The fabricated Push-push DRO shows such characteristics as the phase noise -106 ㏈c/Hz at the 100 ㎑ frequency offset. the output power and fundamental frequency surpression were -6 ㏈m and -29 ㏈c, respectively.

• The Journal of the Korea institute of electronic communication sciences
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• 제9권4호
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• pp.527-536
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• 2014

In this paper, the 50kW aerogenerator which is applicable to the microgrid was designed and analyzed by using commercial simulation program Maxwell 2D. Particularly, the suggested PMSG to reduce the cogging torque introduced the offset and skew concept. The suggested optimal value of offset and skew was decided by 2mm and 60 degree of electric angle. The simulation results of the PMSG when load operation condition showed the average harmonic distortion 1.3%, voltage 322.41V, current 94.95A, and iron loss 9.73W, eddy current loss 73.68W, copper loss 3.52kW. The capacity of aerogenerator calculated 61.56kW, and the suggested design process can be applied to higher capacity generator.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제65권8호
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• pp.1326-1333
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• 2016

It is important to clear the fault and prevent resulting in damage to power system. Although the frequency of generator internal fault is relatively low, it can lead to incalculable damage to power system as well as generator. Especially, loss of field on generator can cause the generator to lose synchronism for a short time if it is not removed promptly. Therefore, it is needed to conduct research on loss of field relay for detecting or clearing the loss of field. However, the setting of the relay may vary in generator operator or engineer, and the relay is not coordinated well with other elements associated with loss of field. In this paper, we address specifically the coordination of positive offset mho loss of field relay which is one of the protection schemes for loss of field. Computer simulations are performed by using ElectroMagnetic Transients Program-Restructured Version (EMTP-RV) based on actual data.

• Korean Journal of Agricultural Science
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• 제47권4호
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• pp.951-962
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• 2020

One hundred ninety-five countries reached agreement on a new climate treaty in Paris, France to reduce the carbon emissions. South Korea has been selected as a target country for reducing greenhouse gas (GHG) obligations since 2020. In this context, the Korean government developed several GHG emissions reduction programs using forests called the "Forest carbon offset scheme (FCOS)." The forest management method is one of the tools to implement FCOS. Most of the participants registered forest management as the preferred methodology to participate in the FCOS. For a successful implementation of the FCOS, it is necessary to explore the optimal methods by considering the cost-effective aspect of conducting the forest management as a tool to increase carbon absorption. In this context, this study investigated the value optimized FCOS projects based on the forest management methodology in South Korea. Three forest management scenarios, 1) extending the final age of maturity of Pinus densiflora stands (S1), 2) extending the final age of maturity of Quercus acutissima stands (S2), and 3) reforestation with new species (Pinus densiflora to Quercus acutissima) (S3), were examined and evaluated to identify the optimal carbon absorption and value optimized economic perspective. The results of the scenario-based modelling indicated that S3 showed value optimized from an economical perspective, and S2 was the most effective method to absorb carbon among the scenarios. It is anticipated that this paper will contribute to provide valuable information by presenting innovative approaches as a value optimized FCOS implementing tool in a GHG reduction program in South Korea.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• 제28권10호
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• pp.56-62
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• 2014

When fault currents contain decaying DC offset, the peak value of the fault current in the first cycle of the fault period is higher than the fault current during the steady-state period. To reduce the asymmetric fault current, this paper proposes an operation scheme using the series connection of two hybrid type Superconducting Fault Current Limiters (SFCLs) : an auxiliary SFCL and a main SFCL. The proposed method calculates the fault angle by comparing the zero-crossing time with fault detection time. According to the fault angle calculated, an auxiliary SFCL operates to reduce an asymmetric fault current during half a cycle after fault occurrence. After this process, the fault current is limited by a main SFCL. To confirm the usefulness of the proposed method, case studies using Electro-Magnetic Transients Program (EMTP)/Alternative Transient Program (ATP) Draw are perfomed.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제59권8호
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• pp.1360-1365
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• 2010

In this paper, we propose a distance relaying algorithm using a Discrete Fourier Transform (DFT)-based modified phasor estimation method to eliminate the adverse influence of exponentially decaying DC offsets. Most distance relays are based on estimating phasors of the voltage and current signals. A DFT is generally used to calculate the phasor of the fundamental frequency component in digital protective relays. However, the output of the DFT contains an error due to exponentially decaying DC offsets. For this reason, distance relays have a tendency to over-reach or under-reach in the presence of DC offset components in a fault current. Therefore, the decaying DC components should be taken into consideration when calculating the phasor of the fundamental frequency component of a relaying signal. The error due to DC offsets in a DFT is calculated and eliminated using the outputs of an even-sample-set DFT and an odd-sample-set DFT, so that the phasor of the fundamental component can be accurately estimated. The performance of the proposed algorithm is evaluated for a-phase to ground faults on a 345 kV, 50 km, simple overhead transmission line. The Electromagnetic Transient Program (EMTP) is used to generate fault signals. The evaluation results indicate that adopting the proposed algorithm in distance relays can effectively suppress the adverse influence of DC offsets.

• Transactions on Electrical and Electronic Materials
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• 제6권5호
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• pp.229-232
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• 2005

Direct characterization of band alignment at chemical bath deposition $(CBD)-CdS/Cu_{0.93}(In_{1-x}Ga_x)Se_2$ has been carried out by photoemission spectroscopy (PES) and inverse photoemission spectroscopy (IPES). Ar ion beam etching at the condition of the low ion kinetic energy of 400 eV yields a removal of surface contamination as well as successful development of intrinsic feature of each layer and the interfaces. Especially interior regions of the wide gap CIGS layers with a band gap of $1.4\~1.6\;eV$ were successfully exposed. IPES spectra revealed that conduction band offset (CBO) at the interface region over the wide gap CIGS of x = 0.60 and 0.75 was negative, where the conduction band minimum of CdS was lower than that of CIGS. It was also observed that an energy spacing between conduction band minimum (CBM) of CdS layer and valance band maximum (VBM) of $Cu_{0.93}(In_{0.25}Ga_{0.75})Se_2$ layer at interface region was no wider than that of the interface over the $Cu_{0.93}(In_{0.60}Ga_{0.40})Se_2$ layer.

• Journal of the Institute of Electronics and Information Engineers
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• 제52권2호
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• pp.83-88
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• 2015

In this paper, $2mm{\times}2mm$ sized piezoresistive accelerometers were designed and fabricated. Two kinds of accelerometers with different spring structure are designed. One is an accelerometer with 4 beam spring located in the center of the mass, the other is an accelerometer with 8 beam spring located in the vertices of the mass. The modal analysis of the accelerometers and the structural analysis were performed using ANSYS program. The former has the superior sensitivity characteristics of $21.38{\mu}V/V/g$ and the lower offset drift of $154.45ppm/^{\circ}C$ than the latter.