Design of Observer-Based Robust Power System Stabilizers

Power systems are subject to undesirable small oscillations that might grow to cause system shutdown and consequently great loss of national economy. The present manuscript  proposes two  designs for observer-based robust power system stabilizer (PSS) using Linear Matrix Inequality (LMI) approach to damp such oscillations. A model to describe power system dynamics for different loads is derived in the norm-bounded form. The first controller design is based on the derived model to achieve  robust stability against load variation. The design is based on a new Bilinear matrix inequality (BMI) condition. The BMI optimization  is solved interatively in terms of Linear Matrix Inequality (LMI) framework. The condition contains a symmetric positive definite full matrix to be obtained, rather than the commonly used block diagonal form. The difficulty in finding a feasible solution is thus alleviated. The resulting LMI is of small size, easy to solve. The second PSS design shifts the closed loop poles in a desired region so as to achieve a favorite  settling time and damping ratio via a non-iterative solution to a set of LMIs.  The approach provides a systematic way to design a robust output feedback PSS which  guarantees good dynamic performance for different loads. Simulation results based on single-machine and multi-machine power system models verify the ability of the proposed PSS to satisfy control objectives for a wide range of load conditions

DIVERSITY OF ETHNICITY AND STATE INVOLVEMENT ON URBAN INFORMALITY IN BEIRUT

Urban informality has become the dominant feature of urban growth on Beirut City and its periphery. Beirut context, as the rest of Lebanese cities, sheds light on a new era of controversy on urban informality. The appearance of urban informality in Beirut is due to the ways that the state being involved on such areas and its affect on shaping the urban fabric, the ways that the influence of various sociopolitical circumstances the country being passed through by which informal areas being established, and the complexity of ethnicity structure within Lebanese society. Understanding the diversity of the state power and ethnicity structure of the society during various periods of the establishment of informal housing areas would enable the state and housing professionals to provide a clear policy strategy to tackle urban informality. Each marginal area needs special treatment according to its religion and ethnicity structure‚ to be remolded within the society.informality; urbanization; state; ethnicity; Lebanon.

Life-cycle of fatigue sensitive structures under uncertainty

Fatigue is the one of the main contributors to problems related to structural safety of civil and marine structures. Life-cycle management (LCM) techniques considering various uncertainties can be used to predict the safe service life of fatigue sensitive structures, plan for their future inspections and support the decision making process regarding maintenance and repair actions. This paper provides a brief overview of the LCM of fatigue sensitive civil and marine structures under uncertainty. Probabilistic performance prediction, inspection scheduling and maintenance optimization for such structures are discussed

The Dahshour (Egypt) Earthquake of 12th of October 1992

On the 12th of October, 1992 an earthquake of 5. 7 moment magnitude hit Dahshour (Egypt) and the surrounding area. The characteristics of the building stock exposed to this earthquake is firstly presented in the paper. Then, the Dahshour earthquake is discussed in terms of the lessons that can be learned by engineers. The paper presents a short description of the geotechnical effects and the observed patterns of damage of the existing building categories and monuments. Finally, a list of the most important conclusions is introduced

A unified approach for numerical simulation of viscous compressible and incompressible flows over adiabatic and isothermal walls

A new formulation (including the choice of variables, their non-dimensionalization, and the form of the artificial viscosity) is proposed for the numerical solution of the full Navier-Stokes equations for compressible and incompressible flows with heat transfer. With the present approach, the same code can be used for constant as well as variable density flows. The changes of the density due to pressure and temperature variations are identified and it is shown that the low Mach number approximation is a special case. At zero Mach number, the density changes due to the temperature variation are accounted for, mainly through a body force term in the momentum equation. It is also shown that the Boussinesq approximation of the buoyancy effects in an incompressible flow is a special case. To demonstrate the new capability, three examples are tested. Flows in driven cavities with adiabatic and isothermal walls are simulated with the same code as well as incompressible and supersonic flows over a wall with and without a groove. Finally, viscous flow simulations of an oblique shock reflection from a flat plate are shown to be in good agreement with the solutions available in literature

ECONOMICS OF PRODUCTIVE TRAITS OF SOME EGG-LAYER STRAINS UNDER EGYPTIAN CONDITIONS

University College of North Wales, Bangor, Gwynedd LL57 2UW Wales, Inited KingdomAverage Cost Curve, Profitabilityu, Mortality Rate, Eggs Yield per Hen Housed Per Month, Feed Consumption, Farm Management, Livestock Production/Industries, Production Economics, Productivity Analysis, Research Methods/ Statistical Methods,

Frameworks for Component-based Simulation

AbstractThe need to reduce development costs of simulation models has led to recent efforts for setting simulation standards that foster model reuse and interoperability. Specifically, the High Level Architecture (HLA) is a new simulation standard supported by the US Defense Modeling and Simulation Office (DMSO). It has been adopted as the standard technical architecture for all US Department of Defense simulations. In the meantime, the commercial sector has had successful efforts in developing enabling technologies for distributed computing; namely, the Common Object Request Broker Architecture (CORBA) by the Object Management Group (OMG). CORBA is a large and complex set of specifications and protocols that utilizes the objectoriented paradigm to achieve distributed object-oriented computing environments that allow object interoperability and reuse. When used as an infrastructure for simulation model reuse and interoperability, both HLA and CORBA exhibit merits and limitations. Since HLA and CORBA were developed independently, need exists for a comparative evaluation of the two architectures as a basis for component-based simulation. In this paper, both HLA and CORBA are presented in the context of component-based simulation model development and interoperability. The two architectures are compared against four comparison criteria that are related to their conceptual foundation and design

New Current-Mode Bandpass Filters Using Three Single-Output ICCIIs

New current-mode bandpass filters using three single outputs inverting second generation current conveyors (ICCII) are introduced. The first circuit uses two ICCII+ and one ICCII−, and realizes an inverting bandpass response. This circuit has one floating resistor and no independent gain control. The second circuit uses three ICCII− and realizes a noninverting bandpass response. The third circuit uses three ICCII+ and realizes also a noninverting bandpass response. The second and third circuits employ four grounded resistors and two grounded capacitors and have independent control on Q and on the center frequency gain by varying a single grounded resistor. Spice simulation results using 0.5 um CMOS transistors are included to support the theoretical analysis

HEPATO-RENAL EFFECTS OF CEFOTAXIME IN ALBINO RATS

Objective: The present study was carried out to evaluate the adverse effects of cefotaxime at two different doses on some biochemical parameters in albino rats. Histopathological changes in liver and kidney induced by cefotaxime were also investigated.Methods: Thirty rats were randomly divided into 3 equal groups; the first group was received distilled water and kept as a control. The second group was received cefotaxime (90 mg/kg b. wt), while the third group was received cefotaxime (180 mg/kg b. wt). Cefotaxime at different doses were injected intramuscularly (IM) twice daily at 12 h intervals for 7 consecutive days.Results: The obtained results showed that, cefotaxime produced significant elevation in creatinine, urea, sodium, potassium, calcium concentrations and decrease concentrations of both glucose and total protein in the serum of treated rats. Also, cefotaxime caused an elevation in some biochemical parameters as (Aspartate aminotransferase (AST), Alanine aminotransferase (ALT), total bilirubin, Cholesterol, Triglycerides and Low density lipoprotein-cholesterol (LDL-chol) and decrease in albumin, High density lipoprotein-cholesterol (HDL-chol) concentrations in serum of treated rats. Histopathological alterations were observed in liver and kidney.Conclusions: It could be concluded that administration of cefotaxime induced some adverse effects on biochemical parameters as well as histopathological changes in liver and kidney.Â