Global Journal of Technology and Optimization

The DC-DC converter with chopper method is the briefest DC-DC converters. Chopper means cutting, and it comes from that cutting electric current by switching with the chopper and convert the voltage. A coil works importantly by the chopper method. The electric current flowing through the circuit at every ON/OFF of the switching element suddenly changes, but the coil generates electromotive force to disturb a current change and produces an induced current (Lenz’s law). From this property that this coil behavior as if breath comes to be jam-packed in the electric current like resistance for the alternating current repeating a current change, the coil is called a choke coil. DC-DC converter with the chopper method is the simple circuit which contains a switching element a choke coil, a capacitor, and a diode together, and step down or boosts DC voltage. The purpose of this study is robust control in consideration of the nonlinearity of the DC-DC converter. Switching-mode DC-DC converter controls electricity by opening and shutting of the semiconductor switch. This type of DC-DC converter is small size, light weight and high efficiency. To do output voltage control in consideration of the nonlinearity of the DC-DC converter, the model formula is derived to use state space averaging method. The control system is designed in consideration of the model-type nonlinearity using the operator theory that was one of the nonlinear control theories and confirmed the effectiveness of the control system by MATLAB and experiments with a breadboard.

In this paper, we analyze different aspects and indicators for assessing environmental vulnerability in Upper Draa Valley (pre-Sahara of Morocco). We began this study by realization of a detailed qualitative analysis based on the calculations of 50 indicators of the environmental vulnerability index (EVI), which is developed by Stockholm Environment Institute (SEI). EVI results allow us to classify the region as a vulnerable area to climate change and anthropogenic impacts. This results show also that water and population indicators influencing the existence of their oasean ecosystems. To analyze the water vulnerability under social and climatic scenarios, we used WEAP program, that predicting urban water demand and the SDSM model which traces the simulations of future climate by forcing the model with two IPCC greenhouse gases scenarios (A2 and B2). The outputs of the models (EVI, WEAP, SDSM) serves as a basis of the “Integrative Science for Society and the Environment” (ISSE) model developed by ILTER in 2007, leading to a holistic understanding of vulnerability, in a coupled human–environment dimension.

Human papillomavirus virus-like particles (HPV VLPs) have been shown to be effective in preventing cervical cancer when used as a prophylactic vaccine. However, little attention has been paid to the process of L1 expression and self-assembly of VLPs in vivo. In this study, the methanol concentration is optimized during fermentation to optimize L1 expression and self-assembly into VLPs. HPV 16 L1 was expressed in Pichia pastoris GS115, and successfully self-assembled into HPV 16 VLPs. The results demonstrate that there is a strong correlation between methanol concentration and the expression of HPV L1 as well as VLP formation. During the methanol induction phase, low concentrations of residual methanol (0.1-0.3%) promoted the expression of free L1 and increased the total content of L1, whereas a higher residual methanol concentration (0.32-0.6%) was conducive for the self-assembly of LI into VLPs. To conclude, if the residual methanol concentration is too low or too high, the levels of L1 can easily decrease during the fermentation process.

Computational grid is a network of loosely coupled, heterogeneous and geographically-dispersed computers acting together to perform a large compute-intensive job. In this article, we focus on the existing approaches to grid scheduling, load balancing and fault-tolerance problems. Although grid scheduling, load balancing and fault tolerance are active research areas in grid computing, these areas have largely been and continue to be developed independent of one another each focusing on different aspects of computing. Hence, in this survey, we hope to show that robust applications that can provide efficient results can be designed by collectively considering these areas. To this end, we first provide an introduction to the motivation, grid scheduling, load balancing and fault tolerance concepts of grid computing and discuss the works that have provided significant contributions to each of these areas since its inception until 2013. We discuss their advantages, disadvantages and analyze their suitability for usage in a dynamic grid environment. We conclude that, while important advancements have been made in each of these areas individually, high performance approaches that cumulatively consider these areas still remain to be explored. We also discuss the research work that is missing and what we believe the community should be considering. To the best of our knowledge, no such survey has been conducted in the literature up to now.

The oases of the Draa are part of the biosphere reserve recognized by UNESCO, 2000. These oases are agro systems located in the Saharan region of southern Morocco. They are the main sources of livelihood of the indigenous population. The sustainability of the oasean system for centuries has made him a rich and resilient ecosystem. Despite its aridity and isolation, the population had always been able to adapt and optimize natural resources, which are scarce. However, during the last 50 years extreme events (droughts, floods and locust attacks) have become increasingly frequent, and have a considerable threat. The article is a diagnostic of resilience state and the impact of extreme events on food security and even existence of this heritage.

Different types of flywheel energy storage systems have been studied in this work. A flywheel energy storage system can be thought of as a mechanical battery that stores energy kinetic energy. The objective is to maximize the energy density of the system. However, the parameters that we change to increase the energy stored in the system might cause the system to collapse if we exceed the maximum allowable stress (the yield strength of the flywheel’s rotor material), hence, a stress analysis study for flywheel rotors is essential in order for us to find out if a rotor is capable of withstanding the given conditions in order to avoid failure. The challenge is to reduce the stress on the rotor in order for us to be able to have a greater angular speed. The results show that having a very large or very low number of spokes will cause failure to occur faster. A large number of spokes caused the failure to occur on the spokes, whereas a small number of spokes caused failure to occur on the rim of the rotor.

The Landau-Devonshire theory of ferroelectrics to date has concentrated mainly on bulk materials, thin film geometries, spherical geometries or other, essentially one-dimensional situations. By extending such calculations to three dimensions it is possible to consider a ferroelectric in the form of a box in which the influence of all surfaces of the box are included in the theory. This influence is expected to be important as the size of the box decreases and the surface to volume ratio increases. With interest in nanoscale materials burgeoning, it is of interest to study such size effects and how they influence the distribution in a ferroelectric box. This paper will show how Landau-Devonshire theory can be applied to such a box. After showing how spontaneous polarization profiles can be calculated, an outline of how Maxwell's equations together with Landau-Khalatnikov dynamical equations can be brought in to study the interaction of the nano-box with incident electromagnetic waves.