• Geomechanics and Engineering
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• 제31권2호
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• pp.129-147
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• 2022

The properties of soil are naturally highly variable and thus, to ensure proper safety and reliability, we need to test a large number of samples across the length and depth. In pile foundations, conducting field tests are highly expensive and the traditional empirical relations too have been proven to be poor in performance. The study proposes a state-of-art Particle Swarm Optimization (PSO) hybridized Artificial Neural Network (ANN), Extreme Learning Machine (ELM) and Adaptive Neuro Fuzzy Inference System (ANFIS); and comparative analysis of metaheuristic models (ANN-PSO, ELM-PSO, ANFIS-PSO) for prediction of bearing capacity of pile foundation trained and tested on dataset of nearly 300 dynamic pile tests from the literature. A novel ensemble model of three hybrid models is constructed to combine and enhance the predictions of the individual models effectively. The authenticity of the dataset is confirmed using descriptive statistics, correlation matrix and sensitivity analysis. Ram weight and diameter of pile are found to be most influential input parameter. The comparative analysis reveals that ANFIS-PSO is the best performing model in testing phase (R² = 0.85, RMSE = 0.01) while ELM-PSO performs best in training phase (R² = 0.88, RMSE = 0.08); while the ensemble provided overall best performance based on the rank score. The performance of ANN-PSO is least satisfactory compared to the other two models. The findings were confirmed using Taylor diagram, error matrix and uncertainty analysis. Based on the results ELM-PSO and ANFIS-PSO is proposed to be used for the prediction of bearing capacity of piles and ensemble learning method of joining the outputs of individual models should be encouraged. The study possesses the potential to assist geotechnical engineers in the design phase of civil engineering projects.

• 한국지구과학회지
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• 제37권7호
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• pp.389-397
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• 2016

${\delta}$ Scuti형 변광성 BO Lyn의 파장에 따른 광도곡선 차이를 알아보기 위해서 보현산천문대의 1.8m 반사망원경과 적외선 검출기 KASINICS를 이용한 측광 관측을 수행하였다. 2011년 3월 26일부터 4월 1일까지 총 7일간의 관측 자료로 J, H, Ks필터 광도곡선을 얻어 기존에 보고된 V필터에서의 광도곡선과 비교하여 주기, 극대점, 진폭, 형태에 대한 차이를 알아보았다. 적외선 광도곡선의 주기 분석 결과 단일 주파수해 $f_1=10.712cycle/day$, 주기$P=0.09335{\pm}0.00002days$의 값을 얻었으며, 파장에 따른 주기의 차이는 나타나지 않았다. 적외선에서는 $2f_1$에 해당하는 주파수가 검출되었는데, 이는 고진폭 ${\delta}$ Scuti형 변광성의 특징인 비대칭적인 광도곡선의 형태를 잘 설명해준다. 극대점의 위치를 비교한 결과 계산된 V필터의 예상 극대점보다 관측된 적외선 극대점이 전체 주기의 약 0.3에 해당하는 만큼 더 늦게 나타났다. 진폭은 ${\Delta}J/{\Delta}V=0.328$, ${\Delta}H/{\Delta}V=0.216$, ${\Delta}Ks/{\Delta}V=0.211$로 파장이 길어질수록 변광의 폭이 더 작게 나타났다. 파장에 따른 극대점의 지연과 변광폭의 차이는 맥동변광성의 밝기 변화가 주로 온도변화에 기인하기 때문인 것으로 여겨진다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권2호
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• pp.189-195
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• 2005

This paper presents a new velocity estimation strategy for a non-salient permanent magnet synchronous motor drive without high frequency signal injection or special PWM pattern. This approach is based on the d-axis current regulator output voltage of the drive system, which contains the rotor position error information. The rotor velocity can be estimated through a rotor position tracking PI controller that controls the position error at zero. For zero and low speed operation, the PI gain of the rotor position tracking controller has a variable structure according to the estimated rotor velocity. Then, at zero speed, the rotor position and velocity have sluggish dynamics because the varying gains are very low in this region. In order to boost the bandwidth of the PI controller during zero speed, the loop recovery technique is applied to the control system. The PI tuning formulas are also derived by analyzing this control system by frequency domain specifications such as phase margin and bandwidth assignment.

• Biotechnology and Bioprocess Engineering:BBE
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• 제4권1호
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• pp.12-16
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• 1999

Xenorhabdus nematophilus sp., an insect-pathogenic bacterium, was newly isolated from Korean entomopathogenic nematode of Steinernema carpocapsae, which can be used as a useful bioinsecticide. Primary and secondary form variants of Xenorhabdus nematophilus were observed when cultured in vitro. Primary form variants adsorbed bromothymol blue, while secondary form did not. However, many other characters of two variants were very similar. The variants were all rod-shaped and cell size was highly variable ranging from 0.5 by 2.0 ${\mu}$m to 1.0 by 5.0 ${\mu}$m. Both produced highly toxic substances and killed the insect larva within 20∼38 hr, indicating that insect pathogenicity of Xenorhabdus is not directly associated with its phase variation. In addition, cell-free culture supernatant of Xenorhabdus was sufficient to kill the insect larva by injecting it ito insect hemolymph; however, cell-harboring culture broth was more effective for killing the insect. The use of Xenorhabdus nematophilus may provide a potential alternative to Bacillus thuringiensis (Bt) toxins.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1509-1512
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• 2003

The electric power wheelchair needs to control motor torque and speed for responding to variable actions given by handling a joystick. In this paper a DSP-based BLDC motor controller using a single dc-link current sensor is presented for electric power wheelchair. It is composed by a DSP processor and three-phase inverter module. To control torque, high speed current control is achieved by the PI controller and pulse width modulation (PWM) signals with 25 kHz carrier frequency, which is performed by 200 ${\mu}sec$ cycle. The speed controller computes the new direct current reference from the speed error and the PI control equation. The displacement value by handling the joystick is converted to reference speeds of right and left wheel motors using nonholonomic wheelchair kinematics. Experimental results show that the presented control system is enough to implement a speed servo in wheelchair driving.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.11-14
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• 2004

Digital Video Broadcasting - Satellite (DVB-S) [1] (EN 300 421(bibliography)) was introduced as a standard in 1994. However, by combing with higher order modulation, promise more powerful alternatives to the DVB-S / DVB-DSNG coding and modulation schemes. Variable rate coding and modulation (VCM) may employed to provide different levels of error protection to different service components. Adaptive coding and modulation (ACM) provides more exact channel protection and dynamic link adaptation to propagation conditions, targeting each individual receiving terminal. By these reasons, DVB-S2 introduced. This paper derives exact symbol error rate(SER) of 16-Amplitude Phase Shift Keying(APSK) modulation by using Craig's formula. 16-APSK modulation is used in DVB-S2. The difference between Union Bound and Craig's formula is 1.26dB in low SNR and 0.1dB in high SNR.

• 한국음향학회지
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• 제17권5호
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• pp.57-62
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• 1998

본 논문에서는 입력신호의 시변특성에 따라 분석 필터의 대역을 가변 시키는 필터 뱅크의 구조를 제안한다. 제안된 필터뱅크는 일반적으로 32개의 균일한 대역으로 나누어 임 계대역의 표현을 적절히 표현하지 못하는 Polyphase 필터의 단점을 극복하면서 시스템 설 계에 높은 계산량을 요구하는 QMF-tree 필터의 단점을 보완한다. 본 연구에서는 분할 대역 은 4개에서 26개의 대역으로 가변하고, 웨이블릿 필터중 Daubechies필터를 사용하였다. 제 안된 구조의 부호화기는 128kbps에서 MPEG-a오디오와 비슷한 수준의 CD 음질을 유지하 며, 연산량 비교결과는 PolyPhase filter를 이용한 MPEG보다 부호화, 복호화 과정을 합쳐 다양한 전송률과 음원에서 평균 19%의 감소를 얻었다.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.134-144
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• 2017

This paper presents an adaptive control strategy for the speed control of a four-phase switched reluctance motor (SRM) in automotive applications. The main objective is to minimize the torque ripples, despite the unstructured uncertainties, time-varying parameters and external load disturbances. The bound of perturbations is not required to be known in the developing of the proposed adaptive-based control method. In order to achieve a smooth control effort, some properties are incorporated and the proposed control algorithm is constructed using the Lyapunov theorem where the closed-loop stability and robust tracking are ensured. The effectiveness of the proposed controller in rejecting high perturbed load torque with smooth control effort is verified with comparing of an adaptive sliding mode control (ASMC) and validated with experimental results.

• 산업기술연구
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• 제25권B호
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• pp.203-210
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• 2005

The PWM(Pulse Width Modulated) converter for the AC to DC rectification has become attractive in the industrial variable-speed drive application and the electric utilities due to the following benefits: Nearly the sinusoidal input current with unity power factor; Controllable DC link voltage; Bidirectional power flow. This paper presents a quantitative analysis of single and three phase PWM converter's input and output characteristics as a function of the input filter inductance under balanced and unbalanced conditions. Also, its performance under the supply voltage including harmonics is investigated by simulation with Matlab Simlulink and experiments. These results provide a reference for selecting the reasonable converter's input filter inductance for given harmonics or power factor criterion.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 추계학술대회 논문집
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• pp.254-255
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• 2013

In this paper, four switches three-phase Z-source dynamic harmonic filter is proposed. It has many advantages, such as reduction of the cost, switching loss and smaller drive circuit. In order to reduction harmonics, new PWM modulation technique with a variable index has been suggested that in comparison with a fixed index type has more capability. The paper presents an application of direct current control(DCC) method in Z-source dynamic harmonic filter to reduce the harmonics generated by the non-linear load. The experimental results will verify the validity of the proposed method.