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Efficient Orbit Propagation of Orbital Elements Using Modified Chebyshev Picard Iteration Method
Get PDFThis paper focuses on propagating perturbed two-body motion using orbital elements combined with a novel integration technique. While previous studies show that Modified Chebyshev Picard Iteration (MCPI) is a powerful tool used to propagate position and velocity, the present results show that using orbital elements to propagate the state vector reduces the number of MCPI iterations and nodes required, which is especially useful for reducing the computation time when including computationally-intensive calculations such as Spherical Harmonic gravity, and it also converges for > 5.5x as many revolutions using a single segment when compared with cartesian propagation. Results for the Classical Orbital Elements and the Modified Equinoctial Orbital Elements (the latter provides singularity-free solutions) show that state propagation using these variables is inherently well-suited to the propagation method chosen. Additional benefits are achieved using a segmentation scheme, while future expansion to the two-point boundary value problem is expected to increase the domain of convergence compared with the cartesian case. MCPI is an iterative numerical method used to solve linear and nonlinear, ordinary differential equations (ODEs). It is a fusion of orthogonal Chebyshev function approximation with Picard iteration that approximates a long-arc trajectory at every iteration. Previous studies have shown that it outperforms the state of the practice numerical integrators of ODEs in a serial computing environment; since MCPI is inherently massively parallelizable, this capability is expected to increase the computational efficiency of the method presented
Modeling Impacts on Space Situational Awareness PHD Filter Tracking
Get PDFIn recent years, probabilistic tracking methods have been becoming increasingly popular for solving the multi-target tracking problem in Space Situational Awareness (SSA). Bayesian frameworks have been used to describe the objects' of interest states and cardinality as point processes. The inputs of the Bayesian framework filters are a probabilistic description of the scene at hand, the probability of clutter during the observation, the probability of detection of the objects, the probability of object survival and birth rates, and in the state update, the measurement uncertainty and process noise for the propagation. However, in the filter derivation, the assumptions of Poisson distributions of the object prior and the clutter model are made. Extracting the first-order moments of the full Bayesian framework leads to a so-called Probability Hypothesis Density (PHD) filter. The first moment extraction of the PHD filter process is extremely sensitive to both the input parameters and the measurements. The specifics of the SSA problem and its probabilistic description are illustrated in this paper and compared to the assumptions that the PHD filter is based on. As an example, this paper shows the response of a Cardinality only PHD filter (only the number of objects is estimated, not their corresponding states) to different input parameterizations. The very simple Cardinality only PHD filter is chosen in order to clearly show the sole effects of the model mismatch that might be blurred with state estimation effects, such as non-linearity in the dynamical model, in a full PHD filter implementation. The simulated multi-target tracking scenario entails the observation of attitude stable and unstable geostationary objects
A Unification of the Concepts of the Variational Iteration, Adomian Decomposition and Picard Iteration Methods; and a Local Variational Iteration Method
Get PDFThis paper compares the variational iteration method (VIM), the Adomian decomposition method (ADM) and the Picard iteration method (PIM) for solving a system of first order nonlinear ordinary differential equations (ODEs). A unification of the concepts underlying these three methods is attempted by considering a very general iterative algorithm for VIM. It is found that all the three methods can be regarded as special cases of using a very general matrix of Lagrange multipliers in the iterative algorithm of VIM. The global variational iteration method is briefly reviewed, and further recast into a Local VIM, which is much more convenient and capable of predicting long term complex dynamic responses of nonlinear systems even if they are chaotic
Modeling of Muscle Force at Varied Joint Angles of the Human Arm and Estimation of Gripping Force Using Surface EMG
Get PDFThis paper aims to determine the force required for holding the objects by human hand. A static analysis is performed on mathematical models to obtain holding force considering lower arm as class three lever and by varying the joint angles. Three mathematical models are discussed to quantify the force required to hold any object, for different weight of the object and the joint angles. A noninvasive experimentation using surface electromyogram was performed to determine the forces required by human hand for the same objects used in the mathematical modeling. Twenty-one male subjects participated in this test and were asked to hold different objects. EMG signals were recorded and converted into grip force in Newton. The EMG to Force conversion was accomplished by the equation derived from the Hills model. The experimentation revealed that subjects in the age group of 20-50 years generated more grip force as compared to those above the age of fifty years. The values of muscle force obtained from the experimentation are optimum values which depend upon the nature of the gripping habits subjects are used to. Whereas, in the case of mathematical models yielded maximum force required to sustain the weight placed on the hand considering it as a mechanical system. The study revealed an average gripping force of 85 Newton required to hold the objects weighing between 0.015 kg to 1.18 kg used in the experimentation. The mathematical model resulted in an average of 162 Newton muscle force to hold the object having similar weights
Differential Responses of Cultured MC3T3-E1 Cells to Dynamic and Static Stimulated Effect of Microgravity in Cell Morphology, Cytoskeleton Structure and Ca<sup>2+</sup> Signaling
Get PDFRandom positioning machine (RPM) and diamagnetic levitation are two essential ground-based methods used to stimulate the effect of microgravity in space life science research. However, the force fields generated by these two methods are fundamentally different, as RPM generates a dynamic force field acting on the surface in contact with supporting substrate, whereas diamagnetic levitation generates a static force field acting on the whole body volume of the object (e.g. cell). Surprisingly, it is hardly studied whether these two fundamentally different force fields would cause different responses in mammalian cells. Thus we exposed cultured MC3T3-E1 osteoblasts to either dynamically stimulated effect of microgravity (d-µg) with RPM or statically stimulated effect of microgravity (s-µg) with diamagnetic levitation, respectively, for 3 h. Subsequently, the cells were examined for changes in cell morphology, cytoskeleton (CSK) structure and Ca2+ signaling. The results show that compared to the condition of normal gravity (1g), both d-µg and s-µg resulted in decrease of cell area and disruption of the microfilaments and microtubules in MC3T3-E1 cells, but cells under d-µg were more smooth and round while those under s-µg exhibited more protrusions. The decrease of cell area and disruption of microfilaments and microtubules induced by d-µg but not s-µg were rescued by inhibition of the stretch-activated channel by gadolinium chloride (Gd). Inhibition of calmodulin (CaM) by inhibitor, W-7, promoted the effects of s-µg on cell area and CSK filaments, but inhibition of calmodulin-dependent protein kinase (CaMK) by inhibitor, KN-93, weakened d-µg-induced effects on cell area and cytoskeleton. In addition, both d-µg and s-µg decreased the CaM expression and CaMKⅡ activity in MC3T3-E1 cells. Furthermore, s-µg resulted in decrease of the intracellular free Ca2+ concentration ([Ca2+]i) in MC3T3-E1 cells, which was reversed by disrupting microfilaments with cytochalasin B (CytB). Instead, d-µg induced increase of [Ca2+]i, which was inhibited by Gd. Taken together these data suggest that dynamic and static stimulated microgravity cause different responses in MC3T3-E1 cells. The dynamic force field acts on stretch-activated channels to induce microfilaments disruption and Ca2+ influx in MC3T3-E1 cells whereas the static force field directly induces microfilament disruption, which in turn decreases the [Ca2+]i in MC3T3-E1 cells. Such findings may have important implications to better understanding microgravity related cellular events and their applications
Influence of the Extraction Temperature on the Properties of Biopolymers Obtained from Tannery Wastes
Get PDFThe tanning i ndustry generates very large quantities of industrial wastes. The advancement of European policy and legislation protecting the environment has prompted the transformation of tannery solid waste materials into valuable co-products, useful to be recycled or employed in other industries. The objective of this work is to obtain gelatine from tannery wastes, in order to reuse it as natural microencapsulating agent in the production of active materials with functional properties. Concretely, this paper focuses on the influence of the extraction temperature on gelatine properties and its microencapsulating ability. An alternative enzymatic pre-treatment to the conventional alkaline one is proposed in order to save costs and reduce time, as well as to reduce the environmental impact. Gelatines with different characteristics and functional properties could be successfully extracted from enzymatically pre-treated tannery wastes. The optimisation of the extraction temperature allowed tannery wastes to be recycled by obtaining medium grade gelatine suitable for microencapsulation purposes
Investigation of CNSL-Based Hybrid Sol in Conventional Polymeric Material
Get PDFThe performance properties of conventional polymeric material have been investigated by modifying it with cashew nut shell liquid (CNSL) derived hybrid precursor. The synthesis of hybrid material involved formation of maleic anhydride adduct of CNSL followed by silane modifi cation and subsequent hydrolysis and condensation with tetra ethyl orthosilicate. The developed hybrid material was characterized by a number of instrumental techniques like FT-IR, 1H-NMR and 13C-NMR, as reported in our earlier work. In the present work, we have investigated the effect of CNSL-based hybrid material on the performance properties of conventional alkyd-melamine formaldehyde-based stoving system. The synthesized material was used as a modifi er at various concentrations (15, 30 and 50 wt% of alkyd resin). The developed coating formulations were applied on mild steel and cured at 120 °C for 30 minutes. Further, the completely cured coatings were evaluated for optical, thermal, mechanical, chemical and solvent resistance properties, hydrolytic stability, UV resistance, corrosion resistance, morphological behavior and elemental distribution properties. The study conducted showed that incorporation of CNSL-based hybrid materials improved overall performance properties by forming crosslinked silane network within the material along with strong metal-oxygen-silicon covalent bond at metal coating interface
Thermal Degradation of Type I Collagen from Bones
Get PDFThe denaturation processes of collagen in the temperature range between 450 K and 670 K are revealed through studies performed on cow rib bones by means of mechanical spectroscopy, differential scanning calorimetry, thermogravimetry, scanning electron microscopy and infrared spectroscopy. The conformational change of the collagen molecules from a triple helix structure to a random coil was found at around 510 K. It was determined that the transformation is developed through the viscous movement of fibrils with an activation energy of (127 ± 8) kJ/mol. The second stage of massive bulk deterioration of the collagen was found at around 600 K, which leads to the loss of the mechanical integrity of the bulk collagen. In addition, an easy-to-handle viscoelastic procedure for obtaining the activation energy of the denaturation process from mechanical spectroscopy studies was also shown
Preparation and Characterization of Poly(butylene succinate) Bionanocomposites Reinforced with Cellulose Nanofiber Extracted from Helicteres isora Plant
Get PDFIsora nanofibers (INF) were produced by a combined thermal-chemical-mechanical method from Helicteres isora plant. The resulting fibers were analyzed using transmission electron microscopy and scanning electron microscopy, which showed a network-like structure with a length of 600 nm, width of 50 nm and an aspect ratio of 12. Fourier transform infrared spectroscopy indicated that chemical treatments progressively removed noncellulosic constituents. X-ray diffraction analysis revealed that crystallinity increased with successive chemical treatments. Using the synthesized isora nanofibers, poly(butylene succinate) (PBS)-based biodegradable nanocomposites were prepared. The nanocomposites were processed using a Brabender twin-screw compounder and an injection molding machine. Effects of INF on the mechanical properties of nanocomposites were investigated. Tensile and flexural moduli of PBS-INF nanocomposites showed an increase with increase in INF content owing to the network formation of the nanofibers in the PBS matrix, whereas toughness and strain-at-break exhibited the opposite trend. Tensile and flexural strengths showed an increase up to 1.5 phr of INF loading, beyond which they were observed to decline owing to agglomeration of INF. Theoretically predicted tensile strength and Young’s modulus were found to increase with INF content; however, there existed a mismatch between theoretical predictions and experimental observations
On Improving the Celebrated Paris’ Power Law for Fatigue, by Using Moving Least Squares
Get PDFIn this study, we propose to approximate the a－n relation as well as the da/dn－∆K relation, in fatigue crack propagation, by using the Moving Least Squares (MLS) method. This simple approach can avoid the internal inconsistencies caused by the celebrated Paris’ power law approximation of the da/dn－∆K relation, as well as the error caused by a simple numerical differentiation of the noisy data for a－n measurements in standard fatigue tests. Efficient, accurate and automatic simulations of fatigue crack propagation can, in general, be realized by using the currently developed MLS law as the “fatigue engine” [da/dn versus ∆K], and using a high-performance “fracture engine” [computing the K-factors] such as the Finite Element Alternating Method.
In the present paper, the “fatigue engine” based on the present MLS law, and the “fracture engine” based on the SafeFlaw computer program developed earlier by the authors, in conjunction with the COTS software ANSYS, were used for predicting the total life of arbitrarily cracked structures.
By comparing the numerical simulations with experimental tests, it is demonstrated that the current approach can give excellent predictions of the total fatigue life of a cracked structure, while the celebrated Paris’ Power Law may miscalculate the total fatigue life by a very large amount