Search results for: nonlinear AIDS model

Authors: Takashi Shimizu, Tomoaki Hashimoto

Abstract:

A class of implicit systems is known as a more generalized class of systems than a class of explicit systems. To establish a control method for such a generalized class of systems, we adopt model predictive control method which is a kind of optimal feedback control with a performance index that has a moving initial time and terminal time. However, model predictive control method is inapplicable to systems whose all state variables are not exactly known. In other words, model predictive control method is inapplicable to systems with limited measurable states. In fact, it is usual that the state variables of systems are measured through outputs, hence, only limited parts of them can be used directly. It is also usual that output signals are disturbed by process and sensor noises. Hence, it is important to establish a state estimation method for nonlinear implicit systems with taking the process noise and sensor noise into consideration. To this purpose, we apply the model predictive control method and unscented Kalman filter for solving the optimization and estimation problems of nonlinear implicit systems, respectively. The objective of this study is to establish a model predictive control with unscented Kalman filter for nonlinear implicit systems.

Keywords: optimal control, nonlinear systems, state estimation, Kalman filter

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Authors: Qiuling Xie, Shanliang Zhu, Zongdi Sun

Abstract:

In this paper, we analyzed the correlation relationship among PM2.5 from other five Air Quality Indices (AQIs) based on the grey relational degree, and built a multivariate nonlinear regression equation model of PM2.5 and the five monitoring indexes. For the optimal control problem of PM2.5, we took the partial large Cauchy distribution of membership equation as satisfaction function. We established a nonlinear programming model with the goal of maximum performance to price ratio. And the optimal control scheme is given.

Keywords: grey relational degree, multiple linear regression, membership function, nonlinear programming

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Authors: Ebrahim Hassan Kapeel, Ahmed Mohsen Kamel, Hossan Hendy, Yehia Z. Elhalwagy

Abstract:

Interest in autopilot design has been raised intensely as a result of recent advancements in Unmanned Aerial vehicles (UAVs). Due to the enormous number of applications that UAVs can achieve, the number of applied control theories used for them has increased in recent years. These small fixed-wing UAVs are suffering high non-linearity, sensitivity to disturbances, and coupling effects between their channels. In this work, the nonlinear dynamic inversion (NDI) control lawisdesigned for a nonlinear small fixed-wing UAV model. The NDI is preferable for varied operating conditions, there is no need for a scheduling controller. Moreover, it’s applicable for high angles of attack. For the designed flight controller validation, a nonlinear Modified PI-D controller is performed with our model. A comparative study between both controllers is achieved to evaluate the NDI performance. Simulation results and analysis are proposed to illustrate the effectiveness of the designed controller based on NDI.

Keywords: UAV dynamic model, attitude control, nonlinear PID, dynamic inversion

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Authors: Onyebueke Godwin, Okwarafor Friday

Abstract:

Introduction: Persons with HIV/AIDS disease are predisposed to mental health disorders such as depression and suicide. HIV/AIDS, being a chronic medical illness with antecedent stigmatization ostracization, leads to low mood, low self-esteem, and a tendency to kill oneself due to the burden of the disease in terms of cost and disability. The aim of one study was to examine the prevalence of depression and risk of suicide among HIV/AIDS patients compared to negative persons. Instruments: The Major Depressive Episode and Suicidality modules of the MINI-Neuropsychiatric inventory were used to screen the attendees. Report: The prevalence of depression and risk of suicide were 27.8% and 7.8%, respectively, for the HIV positive subjects, but 1208% and 2.2%, respectively, for negative subjects. Conclusion and Significance: Persons with HIV/AIDS usually present with mental health symptoms, but the attending physicians usually pay attention to physical symptoms. The symptoms of the disease or the side effects of the medication may mask the mental health disease. Recommendation: There is need to screen HIV/AIDS patents for mental health disorders during clinic visits.

Keywords: depression, HIV/AIDS, suicidality

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Authors: Fatima Kiran

Abstract:

This study investigates the HIV/AIDS coverage in the selected newspapers. The premises of the study depend upon the fact that informing public about any social issue that effects people’s life is among one of the fundamental functions of media, such as HIV/AIDS is one of prime importance. In this study two most prime newspapers of Pakistan Daily Jang and Daily Dawn were analyzed. This paper adopted two approaches for investigation one is content analysis and another is discourse analysis. The content analysis was used to determine the frequency of HIV/AIDS content coverage. Discourse analysis was used to determine consciousness of these newspapers on covering HIV/AIDS stories with correct language and terminologies according to the given media guideline of UNICEF. Total 368 editions from 1st July 2017 to 31st December 2017 were sampled for the study. The result of the study indicates that newspapers have severely underestimated the severity of HIV/AIDS. The coverage given by newspapers is dissatisfactory. Selected newspapers used inappropriate terminologies and language in the stories which shows negligence of newspapers regarding HIV/AIDS issue.

Keywords: Pakistani newspapers, HIV/AIDS, coverage, public awareness, content analysis, discourse analysis, press consciousness

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Authors: Luke S. Carlos A. Thompson

Abstract:

The medical model of disability, though beneficial for the medical professional, is often exclusionary, restrictive and dehumanizing when applied to the lived experience of disability. As a result, a critique of this model was constructed called the social model of disability. Much of the language used to articulate the purpose behind the social model of disability can be summed up within the word inclusion. However, this essay asserts that inclusiveness is an incomplete aspiration. The social model, as it currently stands, does not aid in creating a society where those with impairments actually belong. Rather, the social model aids in lessening the visibility, or negative consequence of, difference. Therefore, the social model does not invite society to welcome those with physical and intellectual impairments. It simply aids society in ignoring the existence of impairment by removing explicit forms of exclusion. Rather than simple inclusion, then, this essay uses John Swinton’s concept of friendship and Jean Vanier’s understanding of belonging to better articulate the intended outcome of the social model—a society where everyone can belong.

Keywords: belong, community, differently-able, disability, exclusion, friendship, inclusion, normality

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Authors: Abdullah Eqal Al Mazrooei

Abstract:

In this paper, a nonlinear dynamical system is presented. This system is a bilinear class. The bilinear systems are very important kind of nonlinear systems because they have many applications in real life. They are used in biology, chemistry, manufacturing, engineering, and economics where linear models are ineffective or inadequate. They have also been recently used to analyze and forecast weather conditions. Bilinear systems have three advantages: First, they define many problems which have a great applied importance. Second, they give us approximations to nonlinear systems. Thirdly, they have a rich geometric and algebraic structures, which promises to be a fruitful field of research for scientists and applications. The type of nonlinearity that is treated and analyzed consists of bilinear interaction between the states vectors and the system input. By using some properties of the tensor product, these systems can be transformed to linear systems. But, here we discuss the nonlinearity when the state vector is multiplied by itself. So, this model will be able to handle evolutions according to the Lotka-Volterra models or the Lorenz weather models, thus enabling a wider and more flexible application of such models. Here we apply by using an estimator to estimate temperatures. The results prove the efficiency of the proposed system.

Keywords: Lorenz models, nonlinear systems, nonlinear estimator, state-space model

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Authors: Felix Jr. Garde, Eric Augustus Tingatinga

Abstract:

Most analysis procedures of reinforced concrete (RC) slabs are based on elastic theory. When subjected to large forces, however, slabs deform beyond elastic range and the study of their behavior and performance require nonlinear analysis. This paper presents a numerical model to simulate nonlinear behavior of RC slabs using rigid body-spring discrete element method. The proposed slab model composed of rigid plate elements and nonlinear springs is based on the yield line theory which assumes that the nonlinear behavior of the RC slab subjected to transverse loads is contained in plastic or yield-lines. In this model, the displacement of the slab is completely described by the rigid elements and the deformation energy is concentrated in the flexural springs uniformly distributed at the potential yield lines. The spring parameters are determined from comparison of transverse displacements and stresses developed in the slab obtained using FEM and the proposed model with assumed homogeneous material. Numerical models of typical RC slabs with varying geometry, reinforcement, support conditions, and loading conditions, show reasonable agreement with available experimental data. The model was also shown to be useful in investigating dynamic behavior of slabs.

Keywords: RC slab, nonlinear behavior, yield line theory, rigid body-spring discrete element method

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Authors: Hassan Al Salman

Abstract:

We consider a nonlinear parabolic cross diffusion model arising in applied mathematics. A fully practical piecewise linear finite element approximation of the model is studied. By using entropy-type inequalities and compactness arguments, existence of a global weak solution is proved. Providing further regularity of the solution of the model, some uniqueness results and error estimates are established. Finally, some numerical experiments are performed.

Keywords: cross diffusion model, entropy-type inequality, finite element approximation, numerical analysis

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Authors: M. Seguini, D. Nedjar

Abstract:

In this paper, the nonlinear analysis of Timoshenko beam undergoing moderate large deflections and resting on nonlinear two-parameter random foundation is presented, taking into account the effects of shear deformation, beam’s properties variation and the spatial variability of soil characteristics. The finite element probabilistic analysis has been performed by using Timoshenko beam theory with the Von Kàrmàn nonlinear strain-displacement relationships combined to Vanmarcke theory and Monte Carlo simulations, which is implemented in a Matlab program. Numerical examples of the newly developed model is conducted to confirm the efficiency and accuracy of this later and the importance of accounting for the foundation second parameter (Winkler-Pasternak). Thus, the results obtained from the developed model are presented and compared with those available in the literature to examine how the consideration of the shear and spatial variability of soil’s characteristics affects the response of the system.

Keywords: nonlinear analysis, soil-structure interaction, large deflection, Timoshenko beam, Euler-Bernoulli beam, Winkler foundation, Pasternak foundation, spatial variability

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Authors: Mounir Bekaik, Messaoud Ramdani

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We present in this work a new technique of stabilization for fault nonlinear systems. The approach we adopt focus on a fuzzy Luenverger observer. The T-S approximation of the nonlinear observer is based on fuzzy C-Means clustering algorithm to find local linear subsystems. The MOESP identification approach was applied to design an empirical model describing the subsystems state variables. The gain of the observer is given by the minimization of the estimation error through Lyapunov-krasovskii functional and LMI approach. We consider a three tank hydraulic system for an illustrative example.

Keywords: nonlinear system, fuzzy, faults, TS, Lyapunov-Krasovskii, observer

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Authors: P.-W. Tsai, C.-Y. Chen, C.-W. Chen

Abstract:

In this paper, the stability analysis of a GA-Based adaptive fuzzy sliding model controller for a nonlinear system is discussed. First, a nonlinear plant is well-approximated and described with a reference model and a fuzzy model, both involving FLC rules. Then, FLC rules and the consequent parameter are decided on via an Evolved Bat Algorithm (EBA). After this, we guarantee a new tracking performance inequality for the control system. The tracking problem is characterized to solve an eigenvalue problem (EVP). Next, an adaptive fuzzy sliding model controller (AFSMC) is proposed to stabilize the system so as to achieve good control performance. Lyapunov’s direct method can be used to ensure the stability of the nonlinear system. It is shown that the stability analysis can reduce nonlinear systems into a linear matrix inequality (LMI) problem. Finally, a numerical simulation is provided to demonstrate the control methodology.

Keywords: adaptive fuzzy sliding mode control, Lyapunov direct method, swarm intelligence, evolved bat algorithm

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Authors: Binu Sahayam

Abstract:

HIV/AIDS epidemic is in its third decade and has become a virulent disease that threatens the world population. Many countless efforts had been made yet this has become a social and developmental concern. According to UNAIDS 2013 Report, In India around 2.4 million people are currently living with HIV and third in the infection rate. As every country is facing this health issue, this has become a social and developmental concern for India. In country like India, open discussion on sex and sexuality is not possible due to its conventional culture. Educational institution like schools and colleges can create awareness on sex education, life skill education, information on HIV and STD which is lacking. It is very clear that preventive knowledge remains low and this leads to increase in the HIV/AIDS infection rate. HIV/AIDS is a disease which is not curable but preventable, keeping this in mind religious leaders of various have come forward in addressing the issue of HIV/AIDS using various social strategies. The study has been focused on three main India religious teachings Hinduism, Christianity and Islam in addressing the issue of HIV/AIDS and its possible intervention in dealing with HIV/AIDS prevention. The study is important because it highlights the health issues, stigma discrimination, psychological disturbances and insecurity faced by the infected and affected persons. Therefore, this study privileges the role of religious leadership in the efforts and processes of preventing HIV/AIDS, caring and providing support to People living with HIV/AIDS and argues that intervention of religious leadership is an effective measure to confront many of the barriers associated with HIV/AIDS.

Keywords: HIV and AIDS, STDs, religion and religious organisation

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Authors: Veliswa Nonfundo Hoho, Jabulani Gilford Kheswa

Abstract:

HIV/AIDS has been a long-term condition worldwide, which does not only affect physical health but also causes psychological and social challenges in people living with this condition. In Sub-Saharan countries, namely; Nigeria, Uganda, Zimbabwe and South Africa, people living with HIV/AIDS come across different challenges especially after one has disclosed his/her status. They experience stigma and discrimination, isolation, lack of accessing and receiving treatment, lack of support and experience psychological distress. By using the evidence-based systematic review as a form of methodology, journal articles, dissertations, internet, and books were explored. This paper seeks to describe the challenges faced by people living with HIV/AIDS after disclosure, which forms a critical component of HIV/AIDS prevention and treatment interventions. The disclosure process model is used to underpin the study. This theory allows one to understand when and why interpersonal and verbal self-disclosure is beneficial for individuals who live with concealable stigmatized identities such as HIV/AIDS. Literature findings advocate that both negative and positive results were noted after disclosing one’s HIV status and psychosocial well-being of the majority of people living with HIV/AIDS also get affected especially in societies which subscribe HIV/AIDS pandemic to witchcraft. As for the infected homosexuals, research indicates that they suffer in silence and to cover their emotional emptiness due to ostracism, they often report low- self-efficacy with regard to condom use and become susceptible to reinfections which further place their lives at heightened risk for low immune system. In this regard, this paper challenges the policies which protect the dignity of people living with HIV/AIDS and calls for unity and financial support in favour of psychoeducational programmes and support groups aimed at curbing discrimination.

Keywords: disclosure, discrimination, homosexuality, self-efficacy

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Authors: Abhishek Kumar, Nilam

Abstract:

As we know that, time delay exists almost in every biological phenomenon. Therefore, in the present study, we propose a susceptible–infected–recovered (SIR) epidemic model along with time delay, modulated incidence rate of infection, and Holling Type II nonlinear treatment rate. The present model aims to provide a strategy to control the spread of epidemics. In the mathematical study of the model, it has been shown that the model has two equilibriums which are named as disease-free equilibrium (DFE) and endemic equilibrium (EE). Further, stability analysis of the model is discussed. To prove the stability of the model at DFE, we derived basic reproduction number, denoted by (R₀). With the help of basic reproduction number (R₀), we showed that the model is locally asymptotically stable at DFE when the basic reproduction number (R₀) less than unity and unstable when the basic reproduction number (R₀) is greater than unity. Furthermore, stability analysis of the model at endemic equilibrium has also been discussed. Finally, numerical simulations have been done using MATLAB 2012b to exemplify the theoretical results.

Keywords: time delayed SIR epidemic model, modulated incidence rate, Holling type II nonlinear treatment rate, stability

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Authors: Wataru Nakamura, Tomoaki Hashimoto, Liang-Kuang Chen

Abstract:

This paper provides a state estimation method for automatic control systems of nonlinear vehicle dynamics. A nonlinear tire model is employed to represent the realistic behavior of a vehicle. In general, all the state variables of control systems are not precisedly known, because those variables are observed through output sensors and limited parts of them might be only measurable. Hence, automatic control systems must incorporate some type of state estimation. It is needed to establish a state estimation method for nonlinear vehicle dynamics with restricted measurable state variables. For this purpose, unscented Kalman filter method is applied in this study for estimating the state variables of nonlinear vehicle dynamics. The objective of this paper is to propose a state estimation method using unscented Kalman filter for nonlinear vehicle dynamics. The effectiveness of the proposed method is verified by numerical simulations.

Keywords: state estimation, control systems, observer systems, nonlinear systems

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Authors: Sofiane Bououden, Ilyes Boulkaibet

Abstract:

In this paper, a robust model predictive controller (RMPC) for uncertain nonlinear system under actuator saturation is designed to control a DC-DC buck converter in PV pumping application, where this system is subject to actuator saturation and parameter uncertainties. The considered nonlinear system contains a linear constant part perturbed by an additive state-dependent nonlinear term. Based on the saturating actuator property, an appropriate linear feedback control law is constructed and used to minimize an infinite horizon cost function within the framework of linear matrix inequalities. The proposed approach has successfully provided a solution to the optimization problem that can stabilize the nonlinear plants. Furthermore, sufficient conditions for the existence of the proposed controller guarantee the robust stability of the system in the presence of polytypic uncertainties. In addition, the simulation results have demonstrated the efficiency of the proposed control scheme.

Keywords: PV pumping system, DC-DC buck converter, robust model predictive controller, nonlinear system, actuator saturation, linear matrix inequality

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Authors: Viana Hassan

Abstract:

Each year, 600 million tourists travelled abroad to practice several types of tourism. Nowadays, whatever is the type of tourism practiced it considered as a real public health problem which can contribute the spread of several diseases such as AIDS, H1N1, NDM1 With regard to HIV/AIDS, Lebanon is always considered as a low HIV prevalence country. However, the potential risks associated with the mobility of the population, migration and tourism. The total number of cases reported by the ministry of health since 1989 until the end of 2011 is of 1455 cases, with an average of 85 new cases per year over the last three years. The main reason of the increased number is Travel and migration which represent 50% of the risks reported by cumulative cases. Given the interest of this kind of epidemic it would be interesting to study the Evolution of HIV/ AIDS and its relation with travel and tourism The main aim of this research is to study in general the relation between tourism and health, more specific to understand the relation between Tourism and AIDS, the problem of the transmission of HIV in Lebanon, the ways of contamination and the countries in which these people are contaminated.

Keywords: AIDS, tourism, health, Lebanon

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Authors: Tina Abrefa-Gyan

Abstract:

Background: In Ghana and the rest of sub-Saharan Africa, HIV/AIDS is a public health threat and also causes medical crises for many who are infected with the virus. Objective: This study tested a social care intervention developed to help improve the quality of life of those living with HIV/AIDS in Ghana. Method: Adult respondents (N = 248) were assigned to receive the intervention or usual care for six weeks. Results: Results of the study revealed significant differences between the treatment and control groups in their reports of quality of life. Respondents reported better quality of life upon receiving the intervention. Implication: This study sheds light on the positive relationship between the intervention and quality of life among those living with HIV/AIDS in Ghana. Conclusion: The intervention is innovative and novel in the setting. It will, therefore, help to reduce the risks such as depression, low cognitive functioning, and low physical functioning associated with low quality of life among people living with HIV/AIDS in Ghana in specific, and in sub-Saharan Africa in general.

Keywords: social care intervention, HIV/AIDS, Ghana, quality of life

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Authors: Ebrahim H. Kapeel, Ahmed M. Kamel, Hossam Hendy, Yehia Z. Elhalwagy

Abstract:

Interest in autopilot design has been raised intensely as a result of recent advancements in Unmanned Aerial vehicles (UAVs). Due to the enormous number of applications that UAVs can achieve, the number of applied control theories used for them has increased in recent years. These small fixed-wing UAVs are suffering high non-linearity, sensitivity to disturbances, and coupling effects between their channels. In this work, the nonlinear dynamic inversion (NDI) control law is designed for a nonlinear small fixed-wing UAV model. The NDI is preferable for varied operating conditions, there is no need for a scheduling controller. Moreover, it’s applicable for high angles of attack. For the designed flight controller validation, a nonlinear Modified PI-D controller is performed with our model. A comparative study between both controllers is achieved to evaluate the NDI performance. Simulation results and analysis are proposed to illustrate the effectiveness of the designed controller based on NDI.

Keywords: attitude control, nonlinear PID, dynamic inversion

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Authors: Swapan Maiti, Dipanwita Roy Chowdhury

Abstract:

Nonlinear functions are essential in different cryptoprimitives as they play an important role on the security of the cipher designs. Rule 30 was identified as a powerful nonlinear function for cryptographic applications. However, an attack (MS attack) was mounted against Rule 30 Cellular Automata (CA). Nonlinear rules as well as maximum period CA increase randomness property. In this work, nonlinear rules of maximum period nonlinear hybrid CA (M-NHCA) are studied and it is shown to be a better crypto-primitive than Rule 30 CA. It has also been analysed that the M-NHCA with single nonlinearity injection proposed in the literature is vulnerable against MS attack, whereas M-NHCA with multiple nonlinearity injections provide maximum length cycle as well as better cryptographic primitives and they are also secure against MS attack.

Keywords: cellular automata, maximum period nonlinear CA, Meier and Staffelbach attack, nonlinear functions

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Authors: Tawatchai Apidechkul

Abstract:

This operational research was conducted and divided into two phases: the first phase aimed to determine the risk behaviors used a cross-sectional study design, following by the community participatory research design to develop the HIV/AIDS preventive model among the Akha youths. The instruments were composed of completed questionnaires and assessment forms that were tested for validity and reliability before use. Study setting was Jor Pa Ka and Saen Suk Akha villages, Mae Chan District, Chiang Rai, Thailand. Study sample were the Akha youths lived in the villages. Means and chi-square test were used for the statistical testing. Results: Akha youths in the population mobilization villages live in agricultural families with low income and circumstance of narcotic drugs. The average age was 16 (50.00%), 51.52% Christian, 48.80% completed secondary school, 43.94% had annual family income of 30,000-40,000 baht. Among males, 54.54% drank, 39.39% smoked, 7.57% used amphetamine, first sexual intercourse reported at 14 years old, 50.00% had 2-5 partners, 62.50% had unprotected sex (no-condom). Reasons of unprotected sex included not being able to find condom, unawareness of need to use condoms, and dislike. 28.79% never been received STI related information, 6.06% had STI. Among females, 15.15% drank, 28.79% had sexual intercourse and had first sexual intercourse less than 15 year old. 40.00% unprotected sex (no-condom), 10.61% never been received STI related information, and 4.54% had STI. The HIV/AIDS preventive model contained two components. Peer groups among the youths were built around interests in sports. Improving knowledge would empower their capability and lead to choices that would result in HIV/AIDS prevention. The empowering model consisted of 4 courses: a. human reproductive system and its hygiene, b. risk-avoid skills, family planning, and counseling techniques, c. HIV/AIDS and other STIs, d. drugs and related laws and regulations. The results of the activities found that youths had a greater of knowledge and attitude levels for HIV/AIDS prevention with statistical significance (χ2-τεστ= 12.87, p-value= 0.032 and χ2-τεστ= 9.31, p-value<0.001 respectively). A continuous and initiative youths capability development program is the appropriate process to reduce the spread of HIV/AIDS in youths, particularly in the population who have the specific of language and culture.

Keywords: AIV/AIDS, preventive program, effective, hill tribe

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Authors: Ruth Muturi Wanjiku

Abstract:

HIV/AIDS in Kenya for unborn and young kids. HIV/AIDS is a significant health concern in Kenya, with an estimated 1.5 million people living with the disease. Unfortunately, many of these individuals are unaware of their HIV status, and the disease continues to spread among the population or unborn kids. HIV/AIDS can be transmitted from an infected mother during pregnancy, childbirth, or breastfeeding. However, with early testing and treatment, the risk of mother-to-child transmission can be significantly reduced. Therefore, it is crucial for pregnant women to get tested and receive appropriate medical care. For young kids, HIV/AIDS education is critical to preventing the spread of the disease. It is essential to teach children about the importance of safe sex practices, avoiding risky behaviors such as sharing needles and getting tested regularly. Additionally, children should be taught about the stigma surrounding HIV/AIDS and encouraged to treat individuals living with the disease with compassion and respect. In conclusion, HIV/AIDS is a significant health concern in Kenya that affects individuals of all ages. For unborn kids, early testing and treatment are critical to reducing the risk of mother-to-child transmission. For young kids, education about HIV/AIDS and safe sex practices is essential to preventing the spread of the disease and reducing stigma. It is essential to promote awareness and encourage individuals to get tested and seek medical care if they believe they may be infected with HIV/AIDS.

Keywords: AIDS, HIV, children, pregnant

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Authors: Shangerganesh Lingeshwaran

Abstract:

In this presentation, we have performed numerical simulations for a reaction-diffusion equation with various nonlinear density-dependent diffusion operators and proliferation functions. The mathematical model represented by parabolic partial differential equation is considered to study the invasion of gliomas (the most common type of brain tumors) and to describe the growth of cancer cells and response to their treatment. The unknown quantity of the given reaction-diffusion equation is the density of cancer cells and the mathematical model based on the proliferation and migration of glioma cells. A standard Galerkin finite element method is used to perform the numerical simulations of the given model. Finally, important observations on the each of nonlinear diffusion functions and proliferation functions are presented with the help of computational results.

Keywords: glioma invasion, nonlinear diffusion, reaction-diffusion, finite eleament method

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Authors: Nicolò Vaiana, Giorgio Serino

Abstract:

In this paper, an advanced Nonlinear Exponential Model (NEM), able to simulate the uniaxial dynamic behavior of seismic isolators having a continuously decreasing tangent stiffness with increasing displacement in the relatively large displacements range and a hardening or softening behavior at large displacements, is presented. The mathematical model is validated by comparing the experimental force-displacement hysteresis loops obtained during cyclic tests, conducted on a helical wire rope isolator and a recycled rubber-fiber reinforced bearing, with those predicted analytically. Good agreement between the experimental and simulated results shows that the proposed model can be an effective numerical tool to predict the force-displacement relationship of seismic isolation devices within the large displacements range. Compared to the widely used Bouc-Wen model, unable to simulate the response of seismic isolators at large displacements, the proposed one allows to avoid the numerical solution of a first order nonlinear ordinary differential equation for each time step of a nonlinear time history analysis, thus reducing the computation effort. Furthermore, the proposed model can simulate the smooth transition of the hysteresis loops from small to large displacements by adopting only one set of five parameters determined from the experimental hysteresis loops having the largest amplitude.

Keywords: base isolation, hardening behavior, nonlinear exponential model, seismic isolators, softening behavior

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Authors: Xinhuang Wu, Yousef Sardahi

Abstract:

A hybrid and optimal multi-loop control structure combining linear and nonlinear control algorithms are introduced in this paper to regulate the position of a quadcopter unmanned aerial vehicle (UAV) driven by four brushless DC motors. To this end, a nonlinear mathematical model of the UAV is derived and then linearized around one of its operating points. Using the nonlinear version of the model, a sliding mode control is used to derive the control laws of the motor thrust forces required to drive the UAV to a certain position. The linear model is used to design two controllers, XG-controller and YG-controller, responsible for calculating the required roll and pitch to maneuver the vehicle to the desired X and Y position. Three attitude controllers are designed to calculate the desired angular rates of rotors, assuming that the Euler angles are minimal. After that, a many-objective optimization problem involving 20 design parameters and ten objective functions is formulated and solved by HypE (Hypervolume estimation algorithm), one of the widely used many-objective optimization algorithms approaches. Both stability and performance constraints are imposed on the optimization problem. The optimization results in terms of Pareto sets and fronts are obtained and show that some of the design objectives are competing. That is, when one objective goes down, the other goes up. Also, Numerical simulations conducted on the nonlinear UAV model show that the proposed optimization method is quite effective.

Keywords: optimal control, many-objective optimization, sliding mode control, linear control, cascade controllers, UAV, drones

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Authors: Mohamed Belhorma, Aboubakar S. Bouchikhi, Belkacem Bounab

Abstract:

This paper addresses modeling a Double A-Arm suspension, a three-dimensional nonlinear model has been developed using the multibody systems formalism. Dynamical study of the different components responses was done, particularly for the wheel assembly. To validate those results, the system was constructed and simulated by RecurDyn, a professional multibody dynamics simulation software. The model has been used as the Objectif function in an optimization algorithm for ride quality improvement.

Keywords: double A-Arm suspension, multibody systems, ride quality optimization, dynamic simulation

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Authors: Mohd Asrul Affendi Bin Abdullah

Abstract:

Sample size calculation is especially important for zero inflated models because a large sample size is required to detect a significant effect with this model. This paper verify how to present percentage of power approximation for categorical and then extended to zero inflated models. Wald test was chosen to determine power sample size of AIDS death rate because it is frequently used due to its approachability and its natural for several major recent contribution in sample size calculation for this test. Power calculation can be conducted when covariates are used in the modeling ‘excessing zero’ data and assist categorical covariate. Analysis of AIDS death rate study is used for this paper. Aims of this study to determine the power of sample size (N = 945) categorical death rate based on parameter estimate in the simulation of the study.

Keywords: power sample size, Wald test, standardize rate, ZINBDR

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Authors: E. Shahsavari, R. Ghasemi, A. Akramizadeh

Abstract:

This paper presents a new method to design nonlinear feedback linearization controller for polymer electrolyte membrane fuel cells (PEMFCs). A nonlinear controller is designed based on nonlinear model to prolong the stack life of PEM fuel cells. Since it is known that large deviations between hydrogen and oxygen partial pressures can cause severe membrane damage in the fuel cell, feedback linearization is applied to the PEM fuel cell system so that the deviation can be kept as small as possible during disturbances or load variations. To obtain an accurate feedback linearization controller, tuning the linear parameters are always important. So in proposed study NSGA_II method was used to tune the designed controller in aim to decrease the controller tracking error. The simulation result showed that the proposed method tuned the controller efficiently.

Keywords: nonlinear dynamic model, polymer electrolyte membrane fuel cells, feedback linearization, optimal control, NSGA_II

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Authors: Nicolò Vaiana, Filip C. Filippou, Giorgio Serino

Abstract:

The solution of the nonlinear dynamic equilibrium equations of base-isolated structures adopting a conventional monolithic solution approach, i.e. an implicit single-step time integration method employed with an iteration procedure, and the use of existing nonlinear analytical models, such as differential equation models, to simulate the dynamic behavior of seismic isolators can require a significant computational effort. In order to reduce numerical computations, a partitioned solution method and a one dimensional nonlinear analytical model are presented in this paper. A partitioned solution approach can be easily applied to base-isolated structures in which the base isolation system is much more flexible than the superstructure. Thus, in this work, the explicit conditionally stable central difference method is used to evaluate the base isolation system nonlinear response and the implicit unconditionally stable Newmark’s constant average acceleration method is adopted to predict the superstructure linear response with the benefit in avoiding iterations in each time step of a nonlinear dynamic analysis. The proposed mathematical model is able to simulate the dynamic behavior of seismic isolators without requiring the solution of a nonlinear differential equation, as in the case of widely used differential equation model. The proposed mixed explicit-implicit time integration method and nonlinear exponential model are adopted to analyze a three dimensional seismically isolated structure with a lead rubber bearing system subjected to earthquake excitation. The numerical results show the good accuracy and the significant computational efficiency of the proposed solution approach and analytical model compared to the conventional solution method and mathematical model adopted in this work. Furthermore, the low stiffness value of the base isolation system with lead rubber bearings allows to have a critical time step considerably larger than the imposed ground acceleration time step, thus avoiding stability problems in the proposed mixed method.

Keywords: base-isolated structures, earthquake engineering, mixed time integration, nonlinear exponential model

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