• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.4724-4747
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• 2016

To efficiently reduce on-grid energy consumption, the admission control algorithm in the hybrid energy powered cellular network (HybE-Net) with base stations (BSs) powered by on-grid energy and solar energy is studied. In HybE-Net, the fluctuation of solar energy harvesting and energy consumption may result in the imbalance of solar energy utilization among BSs, i.e., some BSs may be surplus in solar energy, while others may maintain operation with on-grid energy supply. Obviously, it makes solar energy not completely useable, and on-grid energy cannot be reduced at capacity. Thus, how to control user admission to improve solar energy utilization and to reduce on-grid energy consumption is a great challenge. Motivated by this, we first model the energy flow behavior by using stochastic queue model, and dynamic energy characteristics are analyzed mathematically. Then, fuzzy logic based admission control algorithm is proposed, which comprehensively considers admission judgment parameters, e.g., transmission rate, bandwidth, energy state of BSs. Moreover, the index of solar energy utilization balancing is proposed to improve the balance of energy utilization among different BSs in the proposed algorithm. Finally, simulation results demonstrate that the proposed algorithm performs excellently in improving solar energy utilization and reducing on-grid energy consumption of the HybE-Net.

• Journal of Power Electronics
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• 제18권6호
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• pp.1830-1843
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• 2018

In this paper, the generation of a reference current and voltage signal based on a Kalman filter is offered for a 3-phase 4wire UPQC (Unified Power Quality Conditioner). The performance of the UPQC is improved with source voltages that are distorted due to harmonic components. Despite harmonic and frequency variations, the Kalman filter is capable enough to determine the amplitude and the phase angle of load currents and source voltages. The calculation of the first state is sufficient to identify the fundamental components of the current, voltage and angle. Therefore, the Kalman state estimator is fast and simple. A Kalman based control strategy is proposed and implemented for a UPQC in a distribution system. The performance of the proposed control strategy is assessed for all possible source conditions with varying nonlinear and linear loads. The functioning of the proposed control algorithm with a UPQC is scrutinized and validated through simulations employing MATLAB/Simulink software. Using a FPGA SPATRAN 3A DSP board, the proposed algorithm is developed and implemented. A small-scale laboratory prototype is built to verify the simulation results. The stated control scheme for the UPQC reduces the following issues, voltage sags, voltage swells, harmonic distortions (voltage and current), unbalanced supply voltage and unbalanced power factor under dynamic and steady-state operating conditions.

• Biomolecules & Therapeutics
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• 제31권5호
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• pp.573-582
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• 2023

Muscle atrophy is characterized by the loss of muscle function. Many efforts are being made to prevent muscle atrophy, and exercise is an important alternative. Methylglyoxal is a well-known causative agent of metabolic diseases and diabetic complications. This study aimed to evaluate whether methylglyoxal induces muscle atrophy and to evaluate the ameliorative effect of moderate-intensity aerobic exercise in a methylglyoxal-induced muscle atrophy animal model. Each mouse was randomly divided into three groups: control, methylglyoxal-treated, and methylglyoxal-treated within aerobic exercise. In the exercise group, each mouse was trained on a treadmill for 2 weeks. On the last day, all groups were evaluated for several atrophic behaviors and skeletal muscles, including the soleus, plantaris, gastrocnemius, and extensor digitorum longus were analyzed. In the exercise group, muscle mass was restored, causing in attenuation of muscle atrophy. The gastrocnemius and extensor digitorum longus muscles showed improved fiber cross-sectional area and reduced myofibrils. Further, they produced regulated atrophy-related proteins (i.e., muscle atrophy F-box, muscle RING-finger protein-1, and myosin heavy chain), indicating that aerobic exercise stimulated their muscle sensitivity to reverse skeletal muscle atrophy. In conclusion, shortness of the gastrocnemius caused by methylglyoxal may induce the dynamic imbalance of skeletal muscle atrophy, thus methylglyoxal may be a key target for treating skeletal muscle atrophy. To this end, aerobic exercise may be a powerful tool for regulating methylglyoxal-induced skeletal muscle atrophy.

• Geomechanics and Engineering
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• 제36권2호
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• pp.157-166
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• 2024

Generally, the rubble mound installed on the slope embankment of the open-type wharf is designed based on the impact of wave force, with no consideration for the impact of seismic force. Therefore, in this study, dynamic centrifuge model test results were analyzed to examine the acceleration amplification of embankment reinforced with rubble mound under seismic conditions. The experimental results show that when rubble mounds were installed on the ground surface of the embankment, acceleration response of embankment decreased by approximately 22%, and imbalance in ground settlement decreased significantly from eight to two times. Furthermore, based on the experimental results, one-dimensional site response (1DSR) analyses were conducted. The analysis results indicated that reinforcing the embankment with rubble mound can decrease the peak ground acceleration (PGA) and short period response (below 0.6 seconds) of the ground surface by approximately 28%. However, no significant impact on the long period response (above 0.6 seconds) was observed. Additionally, in ground with lower relative density, a significant decrease in response and wide range of reduced periods were observed. Considering that the reduced short period range corresponds to the critical periods in the design response spectrum, reinforcing the loose ground with rubble mound can effectively decrease the acceleration response of the ground surface.

• 한국군사과학기술학회지
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• 제27권2호
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• pp.189-196
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• 2024

Classification of drones and birds is challenging due to diverse flight patterns and limited data availability. Previous research has focused on identifying the flight patterns of unmanned aerial vehicles by emphasizing dynamic features such as speed and heading. However, this approach tends to neglect crucial spatial information, making accurate discrimination of unmanned aerial vehicle characteristics challenging. Furthermore, training methods for situations with imbalanced data among classes have not been proposed by traditional machine learning techniques. In this paper, we propose a data processing method that preserves angle information while maintaining positional details, enabling the deep learning model to better comprehend positional information of drones. Additionally, we introduce a training technique to address the issue of data imbalance.

• 한국전자파학회논문지
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• 제21권6호
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• pp.573-582
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• 2010

본 논문에서는 고해상도 광대역 영상 레이더용 X-대역 송수신기를 설계, 제작하고 성능 보정을 위한 연구를 수행하였다. 영상 레이더용 송수신기는 송신기, 수신기, 송수신 경로기 및 주파수 발생기로 구성되며, 특히 수신기는 지상 이동 표적 탐지를 위한 2 채널 모노펄스 구조를 가진다. 송수신기는 운용 모드에 따라 고해상도 모드를 위한 deramping 수신 기능을 제공하며, SAR 운용 모드에 적합하게 수신 대역폭 선택 기능을 가진다. 송수신기는 X-대역에서 300 MHz 이상의 대역폭을 가지며, T/R 모듈을 구동시키기에 적합하도록 송신 출력은 13.3dBm이며, 수신 이득은 39 dB, 잡음 지수는 3.96 dB 이하인 성능을 얻었다. 수신 이득은 6 비트 디지털 감쇠기에 의해 제어되며, 이득 조절 범위는 30 dB를 보였다. 수신 동적 범위는 30 dB이며, 수신 I/Q 채널 간 진폭 오차는 ${\pm}$0.38 dB 이내, 위상 오차는 ${\pm}$3.47도 이내를 보였다. 시험 결과, 송수신기는 영상 레이더에서 요구되는 전기적인 성능을 만족하였으며, 또한 영상 레이더의 성능을 크게 좌우하는 펄스 오차 항목이 분석되었으며, 임펄스 응답 특성을 개선하기 위한 보정 기법을 적용하여 개발 목표 규격을 만족하는 것을 확인하였다.

• 한국산학기술학회논문지
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• 제14권1호
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• pp.229-238
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• 2013

본 연구는 대학 엘리트 카나디언 선수들의 등속성 근기능을 검사 및 진단하여 선수들의 기능 향상 및 상해예방을 위한 훈련 방법론에 대한 조언을 하고자 함에 목적이 있다. 경주 소재 D 대학의 평균 8.5년의 경력을 가진 8명의 엘리트 선수들이 실험에 참가했으며, Biodex system III, Biodex stabilizer system, THP 2, Inbody 720이 근기능 검사(peak torque, average power, work fatigue), 동적 균형 검사, 신체성분 검사를 위해 사용되었다. 등속성 근기능 검사는 어깨와 허리, 무릎 관절에 대하여 실시하였으며, 측정 후 동측 불균형과 좌 우측 불균형 정도를 평가하였다. 검사 결과 A3, A4, A5, A6, A8 선수는 어깨의 근력과 파워 훈련이, A1, A2, A7, A8 선수는 어깨의 근지구력 훈련이 필요한 것으로 평가되었다. A2, A5, A8 선수는 허리의 근력과 파워 강화 훈련이 필요하였고, A1, A8 선수는 허리의 근지구력 강화 훈련이 필요하였다. 대부분의 선수들은 무릎과 허리의 동측 근력비가 정상적이지 못했는데, 이의 개선을 위해 A2, A3, A4, A8 선수는 복근의 강화가 필요했고 A3, A5, A6, A7, A8 선수는 햄스트링의 강화가 요구되었다. 선수들의 BMI 평균은 24.90 $kg/m^2$, 체지방율은 12.23%, 반응시간 평균은 324 msec, 밸런스 점수는 각각 2.0 미만으로 나타났다. 이러한 결과를 종합해 볼 때, 카나디언 엘리트 선수들은 근력 불균형에 의한 경기력 저하와 상해 잠재 위험성이 있으므로 정기적인 근기능 검사를 통한 관리와 함께 적절한 훈련 처방이 필요할 것이라 생각된다.

• 조명전기설비학회논문지
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• 제17권6호
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• pp.95-104
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• 2003

전기 철도계통은 기존 전력계통과 달리 단상, 대용량 부하로 필연적으로 전압강하, 전압불평형 및 고조파 왜곡 등의 전력품질의 문제가 발생한다. 이러한 문제점 중 상시전압강하는 전력품질의 가중 중요한 요소로서 SVC(Static Var Compensator) 또는 STACOM(Static Compensator)를 설치하여 전압강하를 보상하는 연구가 수행되었다. 또한 순시전압강하는 고속으로 운전중인 철도차량의 제어 및 안전에 상당한 영향을 미칠것으로 예상된다. 따라서 본 논문에서는 AT(Auto Transformer)급전계통에 적용되는 순간전압강하 보상장치에 관한 연구를 수행하였다. 순간전압강하에 의한 철도차량의 과도해석을 위해 전원, 철도급전변압기, AT, 철도선로 및 철도 차량부하를 모델링 하였다. 또한 순간전압강하 발생시 철도차량부하의 과도특성을 분석하였고 이를 보상하기위한 순간전압강하 보상장치 (DVR:Dynamic Voltage Restorer)를 제안하였다. 순간전압강하 보상 시뮬레이션 결과, 순간전압강하 보상장치의 철도급전계통의 적용은 상당히 유용함을 알수있었다.

• 조명전기설비학회논문지
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• 제21권1호
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• pp.42-51
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• 2007

AC 전기철도 시스템은 동적 단상부하가 빠르게 변화하고, 전철 급전변전소에서 3상 전력을 단상 전력으로 변환한다. 이것은 일반 배전 시스템과 비교해서 AC 전기철도 시스템의 전기적인 현상들이 다르다는 것을 나타낸다. AC 전기철도 열차부하의 전기적인 특성은 동적부하의 운영과 운행 스케줄, 트랙의 구배 등에 따라 연속적인 변화를 받고 있다. 이와 같은 열차부하의 운영에 따른 급전거리가 길어 전압강하, 전압 불평형 및 고조파 왜곡현상 등의 전력 품질 저하요인이 발생하게 된다. 이러한 문제점은 상위계통인 송전시스템의 안정도에 악영향을 줄뿐만 아니라, 전기철도 급전시스템의 전력품질 저하, 전기철도차량의 통신장비, 운행 및 수송량 제한에도 영향을 미치게 된다. 따라서 본 논문에서는 전기철도시스템의 과도상태 평가를 위해 PSCAD/EMTDC를 이용한 평가모델을 제시하고, 전압 강하에 주안점을 두어, 전기철도 급전시스템의 말단 분기점(Sectioning Post)에 정지형 무효전력 보상장치인 단상 배전 STATCOM(Single-phase Static Synchronous Compensator)을 설치하여 그 작용에 따른 전압강하 보상을 평가하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제2권1호
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• pp.24-33
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• 2010

Design of a Pump Jet Propulsor (PJP) was undertaken for an underwater body with axisymmetric configuration using axial/low compressor design techniques supported by Computational Fluid Dynamics (CFD) analysis for performance prediction. Experimental evaluation of the PJP was earned out through experiments in a Wind Tunnel Facility (WTF) using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP), residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle m water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.