692 research outputs found
E-Bayesian estimation for the Lomax distribution based on type-II censored data
AbstractThis paper is concerned with using the E-Bayesian method for computing estimates of the unknown parameter and some survival time parameters e.g. reliability and hazard functions of Lomax distribution based on type-II censored data. These estimates are derived based on a conjugate prior for the parameter under the balanced squared error loss function. A comparison between the new method and the corresponding Bayes and maximum likelihood techniques is conducted using the Monte Carlo simulation
Prevalence of HCV Infections Among Hemodialysis Patients in Al Gharbiyah Governorate, Egypt
Introduction: Hepatitis C virus (HCV) is a significant problem for patients undergoing hemodialysis (HD) treatment. This medical problem has never been studied in Al Gharbiyah Governorate; this study was conductedaiming to estimate the prevalence of anti-HCV positive patients and the incidence of seroconversion in its different HD units.Methods: All 2351 patients maintained on HD in the eight towns of Al Gharbiyah Governorate were interviewed and their anti-HCV status was tested by a third-generation enzyme immunoassay. Patients whotested negative for anti-HCV at the start of the study were re-assessed monthly for HCV seroconversion and at the end of the study all patients were screened for HCV antibodies. Results: At the start of our study in March 2011, we found that 824 out of 2351 patients (35%) were anti-HCV reactive. At the end of study in November 2011, we found that HCV seroconversion occurred in 168 out of1527 patients (11%) who were HCV free at the start of the study. By the end of the study, a total of 42.2% were found to be anti-HCV reactive.Conclusion: The study demonstrated high prevalence of anti-HCV in HD units in Al Gharbiyah Governorate. Similar studies must be conducted in all Egyptian governorates’ HD units to evaluate this major health problem all over Egypt. We also encourage strict application of preventive strategies for HCV infection in all health institutes, especially HD units
Optimum PID Controller with Fuzzy Self-Tuning for DC Servo Motor
DC motors are simple and controllable, making them a popular choice for various applications. However, the speed and load characteristics of DC motors can change, making it difficult to control them effectively. This paper proposes an optimum PID controller with fuzzy self-tuning for DC servo motors. The controller uses two steps to adjust the PID gains: The ACS algorithm is employed to identify the optimal PID gains in the first step. A fuzzy logic (FLC) controller is employed in the second stage to further fine-tune the gains. The FLC considers two cost functions: the first function is the sum of the squares of the error between the controlled output and reference input. The second function is a mathematical expression that specifies the required characteristics of the system response. The fuzzy self-tune then uses a set of rules to adjust the PID gains in response to changes in the system. The rules are based on the two cost functions designed to maintain the optimum PID gains for various operating settings. The outcomes of the two functions are: Kp = 5.2381, Ki = 7.0427, and Kd = 0.49468, with rising time = 0.2503, overshoot = 2.5079, and settling time = 10.4824 in the first cost function. The second cost function outcomes are Kp = 8.1381; Ki = 8.6427; and Kd = 0.49468. The FST-PID controller's performance is evaluated using Matlab-Simulink. The proposed controller was tested on a DC servo motor, and the results showed good performance in both steady-state and transient responses. The controller also maintained the optimum PID gains in the event of changes or disturbances. So, the motor's speed can effectively control under a variety of conditions
Dynamics and control of quadcopter using linear model predictive control approach
This paper investigates the dynamics and control of a quadcopter using the Model
Predictive Control (MPC) approach. The dynamic model is of high fidelity and nonlinear, with
six degrees of freedom that include disturbances and model uncertainties. The control approach
is developed based on MPC to track different reference trajectories ranging from simple ones
such as circular to complex helical trajectories. In this control technique, a linearized model is
derived and the receding horizon method is applied to generate the optimal control sequence.
Although MPC is computer expensive, it is highly effective to deal with the different types of
nonlinearities and constraints such as actuators’ saturation and model uncertainties. The MPC
parameters (control and prediction horizons) are selected by trial-and-error approach. Several
simulation scenarios are performed to examine and evaluate the performance of the proposed
control approach using MATLAB and Simulink environment. Simulation results show that this
control approach is highly effective to track a given reference trajectory
Anti-diabetic properties of Securinega virosa (Euphorbiaceae) leaf extract
This study was undertaken to evaluate the hypoglycemic effect of methanol extract of securinega virosa leaves on blood levels of streptozocin-induced diabetes rats. Three doses of the extract (100, 300 and 600 mg/kg) were administered intraperitoneally. After 2 h of extract administration there was no significant change in the blood glucose levels in all the three doses of the extract. Also after 4, 8 and 24 h of extract administration there was a significant (p < 0.05 - 0.001) decrease in the blood glucose levelsin all the three doses of the extract. The preliminary phytochemical screening revealed the presence of reducing sugars, cardiac glycosides, resin, tannins, saponins, glycosides, flavonoids, glycerin carbohydrate, anthraquine and steroids. The median lethal dose (LD50) in rats was calculated to be 1264.9 mg/kg body weight
Removal Of Methylene Blue By Adsorption Of Water Hyacinth Derived Active Carbon Embedded With Cobalt Nanoparticles
In this research, active carbon-based catalyst synthesis and characterization were tested for potential catalysts to be used in dye removal of methylene blue (MB). Water hyacinth is one of the major problems that is facing humankind and especially here in Egypt. One of the implications of industrial activities is environmental pollution. Dyes used in the production of textiles, paper, and clothes are one of the major pollutants. The waste of those dyes discharged into water supplies without treatment or with ineffective treatment harmfully impacts the environment. In this research, the treatment is implemented using active carbon-based catalysts using embedded nanoparticles. This leads to a huge increase in the adsorbent\u27s surface area, also increasing the adsorbent efficiency. The activated carbon was derived from water hyacinth that grows near the Nile River. Water hyacinth has many practical uses as it can absorb heavy metals like lead and dyes. Water hyacinth was converted into activated carbon through carbonization. Different dyes were used with different contact times in fixed conditions
Multi-level selection and the issue of environmental homogeneity
In this paper, I identify two general positions with respect to the relationship between environment and natural selection. These positions consist in claiming that selective claims need and, respectively, need not be relativized to homogenous environments. I then show that adopting one or the other position makes a difference with respect to the way in which the effects of selection are to be measured in certain cases in which the focal population is distributed over heterogeneous environments. Moreover, I show that these two positions lead to two different interpretations – the Pricean and contextualist ones – of a type of selection scenarios in which multiple groups varying in properties affect the change in the metapopulation mean of individual-level traits. Showing that these two interpretations stem from different attitudes towards environmental homogeneity allows me to argue: a) that, unlike the Pricean interpretation, the contextualist interpretation can only claim that drift or selection is responsible for the change in frequency of the focal trait in a given metapopulation if details about whether or not group formation is random are specified; b) that the traditional main objection against the Pricean interpretation – consisting in arguing that the latter takes certain side-effects of individual selection to be effects of group selection – is unconvincing. This leads me to suggest that the ongoing debate about which of the two interpretations is preferable should concentrate on different issues than previously thought
Structure-activity relationships and molecular docking studies of chromene and chromene based azo chromophores
The design of novel materials with significant biological properties is a main target in drug design research.
Chromene compounds represent an interesting medicinal scaffold in drug replacement systems. This report illustrates a successful synthesis and characterization of two novel series of chromene compounds using multi-component reactions. The synthesis of the first example of azo chromophores containing chromene moieties has also been established using the same methodology. The antimicrobial activity of the new molecules has been tested against seven human pathogens including two Gm+ve, two Gm-ve bacteria, and four fungi, and the results of the inhibition zones with minimum inhibitory concentrations were reported as compared to reference drugs. All the designed compounds showed significant potent antimicrobial activities, among of them, four potent compounds 4b, 4c, 13e, and 13i showed promising MIC from 0.007 to 3.9 μg/mL. In addition, antiproliferative analysis against three target cell lines was examined for the novel compounds. Compounds 4a, 4b, 4c, and 7c possessed significant antiproliferative activity against three cell lines with an IC50 of 0.3 to 2 μg/mL. Apoptotic analysis was performed for the most potent compounds via caspase enzyme activity assays as a potential mechanism for their antiproliferative
effects. Finally, the computational 2D QSAR and docking simulations were accomplished for structure-activity relationship analyses
Reliability, risk and lifetime distributions as performance indicators for life-cycle maintenance of deteriorating structures
This is the author’s version of a work that was accepted for publication in Reliability Engineering & System Safety. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.ress.2013.09.013Structural capacity deterioration is among the main causes of increasing failure probabilities
of structural systems, thus maintenance interventions are a crucial task for their rational
management. Several probabilistic approaches have been proposed during the last decades for
the determination of cost-effective maintenance strategies based on selected performance
indicators. However, benefits and drawbacks of each performance indicator with respect to
the others should be further analyzed. The objective of this paper is to investigate
probabilistic approaches based on the annual reliability index, annual risk, and lifetime
distributions for life-cycle maintenance of structural systems. Maintenance schedules are
obtained for representative series, parallel, and series-parallel systems considering total
restoration of component resistances whenever a prescribed threshold, based on a selected
performance indicator, is reached. Effects related to different structural configurations and
correlation among failure modes are investigated. The superstructure of an existing bridge is
used to illustrate the presented approaches
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