http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Prediction of creep in concrete using genetic programming hybridized with ANN
Osama A. Hodhod,Tamer E. Said,Abdulaziz M. Ataya 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.5
Time dependent strain due to creep is a significant factor in structural design. Multi-gene genetic programming (MGGP) and artificial neural network (ANN) are used to develop two models for prediction of creep compliance in concrete. The first model was developed by MGGP technique and the second model by hybridized MGGP-ANN. In the MGGP-ANN, the ANN is working in parallel with MGGP to predict errors in MGGP model. A total of 187 experimental data sets that contain 4242 data points are filtered from the NU-ITI database. These data are used in developing the MGGP and MGGP-ANN models. These models contain six input variables which are: average compressive strength at 28 days, relative humidity, volume to surface ratio, cement type, age at start of loading and age at the creep measurement. Practical equation based on MGGP was developed. A parametric study carried out with a group of hypothetical data generated among the range of data used to check the generalization ability of MGGP and MGGP-ANN models. To confirm validity of MGGP and MGGP-ANN models; two creep prediction code models (ACI209 and CEB), two empirical models (B3 and GL 2000) are used to compare their results with NUITI database.
Two-Stages Sliding Fourier Transform for High Performance Phase Angle and Frequency Tracking
Osama Mohammed Arafa 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.5
Sliding discrete Fourier transform (SDFT) gives excellent performance at nominal frequency operation. However, at off - nominal frequency, it generates errors in both magnitude and phase angle due to spectral leakage. Moreover, its harmonic rejection ability is greatly impaired in this case. This paper introduces a method to apply sliding Fourier transform under off -nominal frequency at fi xed sampling rate while fi xing the defects associated with it off -nominal frequency operation. This method involves the use of two stages sliding Fourier transform (SFT). A fi xed window-width SFT in the fi rst stage is used to drive the variable window-width SFT in the second stage. The proposed technique (SFT–SFT) is tested in real time on dSPACE MicroLabBox using pre-generated voltage vectors to simulate the most inconvenient grid conditions. The testing scenarios proved its superior performance compared to the decoupled stationary reference frame PLL method.
Inflation targeting and the uncertainty level in developing countries
( Osama D. Sweidan ),( Benjamin Widner Jr ) 한양대학교 경제연구소 2014 JOURNAL OF ECONOMIC RESEARCH Vol.19 No.2
This paper investigates theoretically using an economic model whether inflation targeting policy is an optimum policy or not in developing countries, where central banks have engaged in quasi fiscal activities. Technically, the paper compares between two strategies; inflation targeting policy and Morris and Shin (2002a) strategy, in which the expected inflation rate is built based on external and internal signals. The result proves that inflation targeting policy is not an optimum under a dependent central bank. Agents in developing countries do not react to inflation targeting policy because of the high uncertainty level. They prefer to rely on external signals. Moreover, we prove that an effective inflation targeting policy requires more economic certainty and stability.
Osama I. El-Sabbagh,Sameh M. El-Nabtity 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.7
New benzotriazoles (5-8) or dibenzodiazepine derivatives (11-18) were synthesized starting from 3-[(2-amino-4,5-disubstitutedphenyl)amino]-5,5-disubstitutedcyclohex-2-enones (1-4) through internal coupling of their diazonium salts or internal Mannich reaction in the presence of aromatic aldehydes. Pharmacological evaluation of benzotriazole and dibenzodiazepine derivatives for their clozapine-like properties revealed that dibenzodiazepine 11 bearing 4-bromophenyl group exhibited the same antipsychotic activity as the reference drug clozapine while the activity of benzotriazole 7 was 25% lesser than that of clozapine. Moreover, compounds 7 and 11 did not show significant CNS depressant activity as well as no or slight neurotoxicity on contrast to clozapine when tested in mice using forced swim, rotarod and horizontal screen tests.
High-Performance Elevator Traction Using Direct Torque Controlled Induction Motor Drive
Osama Mohamed Arafa,Mohamed Elsayed Abdallah,Ghada Ahmed Abdel Aziz 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.3
This paper presents a detailed realization of direct torque controlled induction motor drive for elevator applications. The drive is controlled according to the well-known space vector modulated direct control scheme (SVM-DTC). As the elevator drives are usually equipped with speed sensors, flux estimation is carried out using a current model where two stator currents are measured and accurate instantaneous rotor speed measurement is used to overcome the need for measuring stator voltages. Speed profiling for a comfortable elevator ride and other supervisory control activities to provide smooth operation are also explained. The drive performance is examined and controllers’ parameters are fine-tuned using MATLAB/SIMULINK. The blocks used for flux and torque estimation and control in the offline simulation are compiled for real-time using dSPACE Microlabox. The performance of the drive has been verified experimentally. The results show good performance under transient and steady state conditions.
Osama Mohamed Ahmed Salem,Noheir Taha Hassan Mohamed International Journal of Computer ScienceNetwork S 2023 International journal of computer science and netw Vol.23 No.1
The research aimed to identify the effectiveness of an educational program using 3D glasses as a technological innovation on academic achievement and attitude towards elearning in science in the preparatory stage. The research relied on the analytical descriptive approach and the semi-experimental approach. The research tools were the achievement test and the scale of attitude towards e-learning. An educational program was designed and produced using 3D glasses. The study sample consisted of 60 students from the second grade in the preparatory stage at the Rural Jeddah School. The research concluded to the following results: There was a satistically sigificant difference at the level of sig. (0.05) among the -mean scores of the experiemtal and control group students in the post assessment atthe level of achievement in favor of the experiemental group and therewas a satistically sigificant difference at the level of sig. (0.05) among mean scores of the experiemtal and control group students in the post assessment at the level of attitude towards e-learning in favor of the experiemental group. And it was found that the positive effect of the 3D educational program for improving the level of achievement and the attitude towards e-learning for the students. The program allowed the experimental group students to practice self-learning, interaction, and achievement according to the individual differences among them.
Osama S. Ebrahim,Praveen K. Jain,Goel Nishith 전력전자학회 2008 JOURNAL OF POWER ELECTRONICS Vol.8 No.1
The wind-driven doubly fed induction generator (DFIG) is currently under pressure to be more grid-compatible. The main concern is the fault ride-through (FRT) requirement to keep the generator connected to the grid during faults. In response to this, the paper introduces a novel model and new control scheme for the DFIG. The model provides a means of direct stator power control and considers the stator transients. On the basis of the derived model, a robust linear quadratic (LQ) controller is synthesized. The control law has proportional and integral actions and takes account of one sample delay in the input owing to the microprocessor’s execution time. Further, the influence of the grid voltage imperfection is mitigated using frequency shaped cost functional method. Compensation of the rotor current pulsations is proposed to improve the FRT capability as well as the generator performance under grid voltage unbalance. As a consequence, the control system can achieve ⅰ) fast direct power control without instability risk, ⅱ) alleviation of the problems associated with the DFIG operation under unbalanced grid voltage, and iii) high probability of successful grid FRT. The effectiveness of the proposed solution is confirmed through simulation studies on 2MW DFIG.