Simulation Methodologies for Satellite Solar Array Dynamics

The purpose of the present thesis is to furnish diverse studies on the dynamic response of satellite solar arrays. The term flexible structure or, briefly, structure has different interpretations and definitions, depending on source and on application. The solar array studied in the present thesis has flexible sub-structures and undergoes large deformations. Structural dynamics is an important basis of many engineering studies associated with engineering structures, such as design, construction, and control. It generally consists of two functions, i.e. free vibration analysis (modal analysis) and response analysis (steady-state and transient analysis). The thesis starts with introducing the solar array considered for our study and then continues with several structural analyses, including nonlinear pre-stressed static analysis, pre-stressed modal analysis, nonlinear full transient analysis and Fast Fourier Transform study on the transient response. The purpose of static analysis is to obtain the configuration of the array under implementing static loads. Modal analysis provides the natural frequencies and mode shapes which are the intrinsic dynamic properties of the structure. Transient analysis is used for evaluating the mechanical behavior of the structure. It gives relations between the intrinsic properties of structure and the external excitations. Transient analysis under different types of inputs will be used to track physical quantities like displacement, rotation, stress, and strain during specific satellite maneuvers. Pointing error will be introduced as a measure of accuracy of Sun tracking maneuver. It will be computed as a postprocessing step on the transient displacement results. To improve the pointing error which will consequently result in higher energy generating performance, two other staggering type input profiles are proposed for each orbit, GEO and LEO. Pointing error and vibration response under the proposed inputs are obtained to determine the efficiency of the new inputs. After a comparison, it will be shown that the proposed inputs are more efficient in the Sun tracking solar array maneuver. At the end, a novel approach in performing mode-superposition transient analysis using modal effective mass tables is introduced. Since it is very common among engineers to assume the first 10 percent or 20 percent of the mode shapes when mode-superposition method is preferred to obtain the transient response, this novel approach shows that even smaller numbers of mode shapes can be assumed to perform this type of analysis and still obtain acceptable results, only if the assumed modes contain the majority of the modal effective mass in a specific direction, depending on the loading condition

Factors affecting phytoplankton fluctuations in the Persian Gulf (Bushehr coastal waters) during winter and spring 2012 - 2013

In this study, surface water samples were collected monthly from five stations inclduing Nayband Bay, Assaloye, Dayer, Kabgan and Bushehr from December 2012 to June 2013. Sampling stations were chosen according to data being collected during algal bloom caused by Cochlodinium polykrikoides in 2008. A total of 45 genera of phytoplankton belongs to four classes were totally identified accounting for 53 species of Bacilariophyceae, 32 species of Dinophyceae, one genus of Euglenophyceae, and one genus of Cyanophyceae. Bacilariophyceae with 89.5% was the most abundant family followed by Dinophyceae with 9.03%, Cyanophyceae with 1.25 % and Euglenophyceae with 0.22 %, respectively. The highest phytoplankton abundance was observed in Bushehr and Nayband Bay stations. In addition to statistical tests, Shannon (Shanon-Winner) and dominance indices were investigated. The lowest variability for Shannon index (1.90) was recorded in Bushehr Station in comparison with other stations. The highest Shanon index was in Dayer station (2.90) with the increase of diversity in Dinophyceae. Evidence of coastal pollution in Dayer along with nutrient inputs from land might be effective in increasing the Shannon index. At 80-90% simmilarity, the results of Cluster analysis separated Dayer station from other stations. It seems that a part of uniformity in phytoplankton abundance is affected by the mild conditions of ambient temperature. The total diversity of phytoplankton in the study area was low. The relative moderation of temperature seems to have contributed to the dominance of diatoms. Yet, the increased volume dust (as emerged by the increased dusty days per year) and the introduction of its accumulation in the Persian Gulf waters, along with other pollutants on phytoplankton communities might be underlaying factors for the dominace of diatoms in the study area

Effects of environmental parameters and nutrients on phytoplankton communities around the shrimp farm complexes in Bushehr Province, in the Persian Gulf

The aim of this work was to be informed and aware of the red tide conditions before the entering of algal blooms in seawater supply canals of the shrimp farm and hatchery complexes in Bushehr Province. Field investigations and monthly samplings have been carried out to determine environmental parameters, nutrients, chlorophyll–a and phytoplankton in the southern part of the input water channels of Mond, Delvar and Heleh farmed shrimp complexes from April to December 2011. The identified phytoplankton belonged to three classes of Bacillariophyceae, Dinophyceae and Cyanophyceae. 12 genera belonging to Dinophyceae, 25 genera to Bacillariophyceae and two genera to Cyanophyceae were observed during the study. The highest average density of total phytoplankton was recorded at Heleh station at 18374 cells/lit. The maximum density of phytoplankton was at Delvar station in December. The highest density of Dinophyceae was observed in August. Alexandrium sp., Ornithocercus and Prorocentrum sp. were the predominant species of Dinophyceae class. Bacillariophyceae are thermo-tolerant and halo-tolerant while Dinophyceae and Cyanophyceae are thermo-intolerant and halo-intolerant. Bacillariophyceae are silica limited while Dinophyceae are phosphorus limited phytoplankton

Control Systems: New Approaches to Analysis and Design

This dissertation deals with two open problems in control theory. The first problem concerns the synthesis of fixed structure controllers for Linear Time Invariant (LTI) systems. The problem of synthesizing fixed structure/order controllers has practical importance when simplicity, hardware limitations, or reliability in the implementation of a controller dictates a low order of stabilization. A new method is proposed to simplify the calculation of the set of fixed structure stabilizing controllers for any given plant. The method makes use of computational algebraic geometry techniques and sign-definite decomposition method. Although designing a stabilizing controller of a fixed structure is important, in many practical applications it is also desirable to control the transient response of the closed loop system. This dissertation proposes a novel approach to approximate the set of stabilizing Proportional-Integral-Derivative (PID) controllers guaranteeing transient response specifications. Such desirable set of PID controllers can be constructed upon an application of Widder's theorem and Markov-Lukacs representation of non-negative polynomials. The second problem explored in this dissertation handles the design and control of linear systems without requiring the knowledge of the mathematical model of the system and directly from a small set of measurements, processed appropriately. The traditional approach to deal with the analysis and control of complex systems has been to describe them mathematically with sets of algebraic or differential equations. The objective of the proposed approach is to determine the design variables directly from a small set of measurements. In particular, it will be shown that the functional dependency of any system variable on any set of system design parameters can be determined by a small number of measurements. Once the functional dependency is obtained, it can be used to extract the values of the design parameters

Monitoring of Cochlodinium polykrikoides blooms as a harmful phenomenon in the Persian Gulf (2010-2011)

The monitoring of the harmful bloom of Cochlodinium polykrikoides in the northern Persian Gulf was studied during 2010 to 2011. The results revealed that in the waters of Hormozgan Province, the Diatoms and Dinoflgellates had the highest frequency. No significant difference was found for amount of nutrients in three sub- regions. The bloom of C. polykrikoides was higher in central sub-region in spring and was occurred in the eastern sub-region in summer, but no mortality of fishes was recorded. In Bushehr Province, four classes of Bacillaryophyceae, Cyanophyceae, Dynophyceae and Prymnesiophyceae were determined. Furthermore significant different values of nutrients were recorded. In waters of Khuzestan Province, different values of NH4 were measured for different months. In total, the measured ratio of N: P in all months was lower than Redfield Ratio (16:1) in which subsequently the environmental condition was not suitable for bloom of C. polykrikoides

Finite element approach and mathematical formulation of viscoelastic auxetic honeycomb structures for impact mitigation

Auxetic structures are designed to be used for producing auxetic materials with controllable mechanical properties. The present study treats a design of viscoelastic auxetic honeycomb structures using numerical approach and mathematical formulation for impact mitigation. In order to increase the energy absorption capacity, viscoelastic material has been added into auxetic structure as it has capability to dissipate energy under impact loading. Kelvin-Voigt and Maxwell models were employed to model viscoelastic components. The auxetic structure was then subjected to impact load with linear and nonlinear load functions. Dynamic analysis was carried out on a star honeycomb structure using continuum mechanics. Influence of different parameters on response function was then further studied. The primary outcome of this research is the development of viscoelastic auxetic honeycomb structural design for predicting the impact resistance under impact loading

Dynamical modeling of uncertain interaction-based genomic networks

BACKGROUND: Most dynamical models for genomic networks are built upon two current methodologies, one process-based and the other based on Boolean-type networks. Both are problematic when it comes to experimental design purposes in the laboratory. The first approach requires a comprehensive knowledge of the parameters involved in all biological processes a priori, whereas the results from the second method may not have a biological correspondence and thus cannot be tested in the laboratory. Moreover, the current methods cannot readily utilize existing curated knowledge databases and do not consider uncertainty in the knowledge. Therefore, a new methodology is needed that can generate a dynamical model based on available biological data, assuming uncertainty, while the results from experimental design can be examined in the laboratory. RESULTS: We propose a new methodology for dynamical modeling of genomic networks that can utilize the interaction knowledge provided in public databases. The model assigns discrete states for physical entities, sets priorities among interactions based on information provided in the database, and updates each interaction based on associated node states. Whenever uncertainty in dynamics arises, it explores all possible outcomes. By using the proposed model, biologists can study regulation networks that are too complex for manual analysis. CONCLUSIONS: The proposed approach can be effectively used for constructing dynamical models of interaction-based genomic networks without requiring a complete knowledge of all parameters affecting the network dynamics, and thus based on a small set of available data

Ecological study in ponds of Litopenaeus vannamei

This study has carried out on five earth ponds of Litopenaeus vannamei shrimps investigation and Mahan Siraf farm s which located at Helleh site in the Bushehr province from may 2007. main objectives’ were: (1) Measurements of quality factors in water and sediment, Planktons and benthoses, (2) quality factors’ effects on growth and survival of Litopenaeus vannamei. With respect the time of shrimp stocking and harvesting, the frequencies of water and sediment sampling were done per 10 day and once per month, respectively. both sediment sampling of the pond beds have done before and after harvesting. The measured factors in the water ponds were: pH, salinity, dissolved oxygen, transparency, temperature (Twice a day in the morning and the afternoon), chlorophyll-a, nitrate, nitrite, orthophosphate, iron, biochemical oxygen demand, TSS, TDS, Planktons. The parameters (pH, total organic matter, iron) were measured in sediment. The measurement of grain size has done in two times (before and after harvesting). Independent variables including nitrate, Ammonia, orthophosphate, iron and chlorophyll-a had significant correlations with shrimp weights as dependent variable. Nitrate showed the highest correlation with the shrimp weights (r=0.921). overall correlation of fifth most important factors with the shrimp weights, namely nitrate, orthophosphate, Ammonia, iron and chlorophyll-a was estimated to r=0.999. The results show low concentration of the essential nutrient such as phosphate and nitrate, high concentration of ammonia, undesirable’s transparency, and a great amount of clay in pond beds. On the basis of above description, required to renewing management in fertilizing, feedings, liming qualities of the bed