Ayman Kassem

Laser and Pneumatic Lithotripsy in the Endoscopic Management of Large Ureteric Stones: A Comparative Study

Objective: We compared the results of holmium laser and pneumatic intracorporeal lithotripsy for large ureteric calculi in terms of efficacy, safety and complications. Methods: The study was conducted between April 2009 and October 2010. 80 patients divided into two equally matched groups were included in a prospective randomized trial including patients with a ureteric stone size of 0.5–2 cm. A holmium laser with a 550-µm fiber was employed in the laser lithotripsy (LL) group. The Swiss Lithoclast was used in the pneumatic lithotripsy (PL) group. Results: Mean stone size was comparable in both groups, namely 13.1 mm in the PL group and 12.9 mm in the LL group. The early stone-free rate was equal in both groups, while the delayed stone-free rate was 95% in LL and 85% in PL. Stone migration occurred in 12 PL cases and in 5 LL cases. Ureteric perforation occurred in 3 LL cases and in 2 PL cases. Ureteric stricture occurred in 1 case following LL. Conclusion: Both PL and LL are effective and safe modalities in treating large ureteric stones with minor insignificant differences. A pneumatic system may be more efficient with regard to the cost-benefit ratio, which was not studied in the present work; further studies should address this issue.

Analytical Relationships for Linear Quadratic Aeroelastic Flight Control Eigenvalues

Several obstacles limiting the use of contemporary control design techniques in production vehicles are noted. These obstacles restrict one from obtaining insight into the control law augmentation of the vehicle. For example, with the linear quadratic (LQ) state feedback method, detail effects from cost function weight adjustment are not easily understood. Further, the role of each feedback loop is not readily apparent. Fundamental to overcoming this problem is factoring of the LQ characteristic polynomial. Useful analytical expressions, and ultimately the relationships they represent, are sought between basic design parameters of the system and the closed-loop eigenvalues. An approximate analytical factoring technique, previously developed for open-loop applications, is considered as a tool for this closed-loop problem. The e rst two terms of a Taylor series are used to capture the polynomial coefe cient dependencies on the polynomial factors. By analytically inverting the e rst-order sensitivity matrix, corrections to preliminary approximate factors are generated. Expressions for the closed-loop factors are in terms of basic parameters such as stability and control derivatives, structural vibration damping ratio and natural frequency, and cost function weights, allowing key relationships to beuncovered between the design knobs and important closed-loop features.

Efficient Neural Network Modeling for Flight and Space Dynamics Simulation

This paper represents an efficient technique for neural network modeling of flight and space dynamics simulation. The technique will free the neural network designer from guessing the size and structure for the required neural network model and will help to minimize the number of neurons. For linear flight/space dynamics systems, the technique can find the network weights and biases directly by solving a system of linear equations without the need for training. Nonlinear flight dynamic systems can be easily modeled by training its linearized models keeping the same network structure. The training is fast, as it uses the linear system knowledge to speed up the training process. The technique is tested on different flight/space dynamic models and showed promising results.

Adaptive Neuro-fuzzy Controller for Multi-layered Switched Reluctance Motor

ABSTRACT There has been big interest in switched reluctance motor (SRM) due to its simplicity and reasonable cost, however excessive torque ripple is one of the major disadvantages of switched reluctance motor. This paper attempts to reduce torque ripples of Switched Reluctance Motor through building multi-layered motor controlled by a hybrid intelligent system known as Adaptive Neuro-fuzzy Inference System ANFIS. Simulation of the proposed motor is conducted using Matlab Simulink environment 2011 and comparison results with single layer switched reluctance motor for both PI and ANFIS controllers show improvement in behavior of MSRM controlled by ANFIS through reduction in speed settling time as well as torque ripples. General Terms Electrical Machines; Adaptive Control. Keywords Rodrigues et Multi-layer switched reluctance motor; SRM; Torque ripples; ANFIS. 1. INTRODUCTION SRM has received attention due to its inherent simplicity, ruggedness, and low cost. These features make it a good candidate for various general purpose adjustable speed applications [1]. The most unique feature of SRM is its double saliency structure which means both stator and rotor has salient poles. The stator winding has concentrated coils, and shorter end turns than other types of motors, leading to a greater manufacturing economy. Moreover the salient rotor has no conductors or magnets, as shown in fig. 1. The rotor turns to get to a position of minimum reluctance by aligning itself with the stator magnetic field when the stator windings are excited, it is thus considered as the simplest of all electric machine rotors[1],[2]. Simplicity of the construction of SRM makes it inexpensive, the windings are electrically separate from each other which make the machine reliable, and cooling is simpler because the major sources of heat are on the stator. In addition, high speed capability of SRM and high torque to inertia ratio makes it a superior choice in different applications. However, Excessive torque ripple, especially at low speeds prevented SRM from widespread use [3]. Actually there are two approaches to reduce torque ripples: one of them is to improve the magnetic design of the motor, by changing the stator and rotor pole structures [4]. El-Kharashi [5] used the hollow cylindrical rotor to reduce torque ripples. There was no shaft, and the cylindrical rotor was designed to grade the air gap, and consequently the reluctance; which reduced ripples in the torque characteristic. Shang and Shing [6] changed the stator shape to c- shape one, the c-shape created more space for winding and hence became more straightforward, it had more number of turns per phase than traditional SRM; as a result the motor gave higher torque for the same current than in traditional SRM and consequently, minimize the cost of the motor. Daldaban and Ustkoyuncu [7] introduced multi-layer SRM. Their design allowed more space for stator winding and higher starting torque than classical SRM of the same size. The noise was reduced as well as torque ripples. The second approach is to use sophisticated electronic control. The electronic approach is based on selecting an optimum combination of the operating parameters, such as supply voltage, turn on and turn off angles and level of current [4]. al. [8] implemented fuzzy logic controller for reducing torque ripples through turn off angle. Zhang et al. [9] also used fuzzy controller to compute the current compensating signal that added to the main current value in order to reduce torque ripple. While Shang et al. [10] introduced flux-linkage controller using sliding mode technique (SM) with integral compensation (I). The integration of SM with I controller result in reduction of torque ripples when compared to each method alone.

Internal Model Control-Based Adaptive Attitude Tracking

The attitude of a spacecraft is its orientation in space. The orientation is with respect to a particular reference like the Earth and Sun [1]. The spacecraft is considered to be a rigid body whose attitude can be described by two sets of equations, namely, the kinematics equation, which relates the time derivatives of the orientation angles to the an- gular velocity vector and the dynamics equation, which describes the time evolution of the angular velocity vector [2, 3]. Various parameterizations of the attitude exist to represent the orientation angles. A comprehensive survey of attitude representations is given in [4]. The attitude control problem was first presented in the literature in [5]. A general procedure for the design and analysis of a three-axis, large-angle attitude control system was developed based on properties common to all attitude control systems. In [6], a general framework is prepared for the analysis of attitude tracking control of a rigid body using the non- singular unit quaternion representation. An adaptive tracking control scheme wherein the unknown spacecraft inertia matrix is compensated using linear parameterization is discussed in [7]. Reference [8] proposes an adaptive attitude tracking controller that identifies the inertia matrix via periodic command signals. Reference [9] discusses the adaptive attitude tracking control using synthesized velocity from attitude measurements by incorporating a velocity filter formulation.

SYMBOLIC ANALYSIS OF LINEAR QUADRATIC CONTROL NUMERATOR AND DENOMINATOR FACTORS

This paper introduces a new method to uncover functional relationships between design parameters of a contemporary control design technique and the resulting closed-loop properties. The method generates such relationships through analytical expressions and is based on order of magnitude analysis. Efforts concentrated on the linear-quadratic state-feedback control-design technique applied to an aeroelastic flight control task. By applying an order of magnitude analysis to the basic system parameters, the Riccati equation can be reduced to a set of simple approximate equations which can be solved in closed-form. After forming the closed-loop transfer function polynomials from the vehicle state-space matrices and the gain matrix, another order of magnitude simplification is considered to analytically factor these polynomials, in an approximate sense. The technique has yielded expressions which are amendable for understanding relationships and still provide sufficient accuracy.

Commercial Cameras Accurate Focal Length Estimation for Satellite Optical Observation

Commercial camera utilization for space applications has attracted the attention of vast number of researches. Accurate spacecraft attitude determination requires a good estimation of the camera optical parameters. For star sensors, it is common to estimate focal length, optical distortion, and principal point. These parameters are considered to be critical for star identification algorithms which are utilized to identify certain stars located at the captured image. This process is usually characterized by a huge computational effort which is very sensitive to these parameters. Samaan M (2012) utilizes a commercial off-the-shelf camera as a low cost star tracker. Camera optical parameters and lens distortion are estimated in Zhou F (2015), Dzamba T (2009), discusses the problem of characterization of field curvature and lens astigmatism aberrations. Pal M, Bhat M (2009), solves the problem of spacecraft attitude determination independent of the problem of camera calibration except for the distortion of the camera lens. The star spot location is estimated in Liu HB (2011) based on Kalman filter only. Samaan MA (2001) uses only two methods to estimate the camera focal length. Samaan MA (2003) used the least squares to optimally estimate the focal length.

Aerospace engineering department at Cairo University: Past, present, and future

The beginning of modern engineering education in Egypt dates back to 1816 when the famous ruler “Wali”; Mohammed Ali Pasha established “Madrasat El-Mohandeskhana” (which means the School of Engineering). This start was 92 years before the establishment of Cairo University which became a reality on December 21st, 1908. In 1935, it was renamed as the “Faculty of Engineering”. The Faculty of Engineering has kept this name ever since. Aerospace engineering department was established in 1953 under the name of “Aeronautics Engineering” and it played an important role for promoting the economic and strategic growth in Egypt since its inception. This paper aims to reflect past, present and future research and development in Aerospace Engineering department at Cairo University. It will shed some light on the department capabilities and accomplishments and future hopes and vision.

Using USAF DATCOM to Predict Nonlinear Aerodynamics of Structurally Impaired Aircraft

This paper presents an approach to predict the nonlinear aerodynamics of a structurally damaged aircraft model based on the engineering level aerodynamic prediction methods, DATCOM. Raw results from the code provide good correlation with wind tunnel data at very low angles of attack, but accuracy deteriorates rapidly as the angle of attack increases. A new methodology is then proposed which combines the experimental results of healthy aircraft with the predicted aerodynamics of the damaged cases, to yield better correlation between experimental and predicted aerodynamic coefficients for damaged aircraft. Three damage- configurations are studied at supersonic speeds. The methodology can be used to quickly generate aerodynamic model for damaged aircraft for simulation and reconfigurable control. Copyright

A general framework for lumbar spine modelling and simulation

A general framework for modelling and simulation of the dynamic, three-dimensional motion response of the human lumbar-spine is presented in this paper. Lumbar vertebrae are modelled as rigid bodies and all other Flexible Joint Structures (FJS) (i.e., ligaments, cartilage, muscles, and tendons) are modelled collectively as massless springs and dampers. Coupling coefficients, providing additional constraints, are incorporated into the model. Unknown model coefficients (nominally spring, damping and coupling coefficients) are automatically determined by systematically matching the model predictions to spine forced displacement-time data. A robust parameter optimisation module (Monte Carlo routine and Genetic Algorithm (GA)) was developed for this purpose. Two test cases were included for parameters estimation and model verification.