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CONTENTS
Volume 4, Number 3, May 2017
 

Abstract
The large container ships and fast patrol boats are complex marine structures. Therefore, their global mechanical behaviour has long been modeled mostly by refined beam theories. Important issues of cross section warping and bending-torsion coupling have been addressed by introducing special functions in these theories with inherent assumptions and thus compromising their robustness. The 3D solid Finite Element (FE) models, on the other hand, are accurate enough but pose high computational cost.In this work, different marine vessel structures have been analysed using the well-known Carrera Unified Formulation (CUF). According to CUF, the governing equations (and consequently the finite element arrays) are written in terms of fundamental nuclei that do not depend on the problem characteristics and the approximation order. Thus, refined models can be developed in an automatic manner. In the present work, a particular class of 1D CUF models that was initially devised for the analysis of aircraft structures has been employed for the analysis of marine structures. This class, which was called Component-Wise (CW), allows one to model complex 3D features, such as inclined hull walls, floors and girders in the form of components. Realistic ship geometries were used to demonstrate the efficacy of the CUF approach. With the same level of accuracy achieved, 1D CUF beam elements require far less number of Degrees of Freedom (DoFs) compared to a 3D solid FE solution.

Key Words
hull structures; refined beam theories; unified formulation; component-wise models

Address
A. Pagani, E. Carrera and R. Jamshed: MUL2 Group, Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

Abstract
Automatic trajectory re-planning is an integral part of unmanned aerial vehicle mission planning. In order to be able to perform this task, it is necessary to dispose of formulas or tables to assess the flyability of various typical flight segments. Notwithstanding their importance, there exist such data only for some particularly simple segments such as rectilinear and circular sub-trajectories. This article presents an analysis of a new, very efficient, way for an airplane to fly on an inclined circular trajectory. When it flies this way, the only thrust required is that which cancels the drag. It is shown that, then, much more inclined trajectories are possible than when they fly at constant speed. The corresponding equations of motion are solved exactly for the position, the speed, the load factor, the bank angle, the lift coefficient and the thrust and power required for the motion. The results obtained apply to both types of airplanes: those with internal combustion engines and propellers, and those with jet engines. Conditions on the trajectory parameters are derived, which guarantee its flyability according to the dynamical properties of a given airplane. An analytical procedure is described that ensures that all these conditions are satisfied, and which can serve for producing tables from which the trajectory flyability can be read. Sample calculations are shown for the Cessna 182, a Silver Fox like unmanned aerial vehicle, and an F-16 jet airplane.

Key Words
automatic trajectory planning; airplane circular trajectory; inclined circular trajectories; inclined pendulum trajectories; Dubins 3D trajectories

Address
Gilles Labonté: Department of Mathematics and Computer Science and Department of Electrical Engineering and Computer Engineering, Royal Military College of Canada, Kingston, Ontario, Canada

Abstract
The natural vibration analysis of microbeams resting on visco-Pasternak\'s beam theory is used for description of natural frequencies of the microbeam. The generalized thermoelasticity model is used to obtain the free vibration frequencies due to the coupling equations of a simply-supported microbeam resting on the three-parameter viscoelastic foundation. The fundamental frequencies are evaluated in terms of length-to-thickness ratio, width-to-thickness ratio and three foundation parameters. Sample natural frequencies are tabulated and plotted for sensing the effect of all used parameters and to investigate the visco-Pasternak\'s parameters for future comparisons.

Key Words
thermoelasticity theory; microbeam; vibration frequencies; viscoelastic foundations

Address
Ashraf M. Zenkour: Department of Mathematics, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia; Department of Mathematics, Faculty of Science, Kafrelsheikh University, Kafrelsheikh 33516, Egypt

Abstract
The axial-injection end-burning hybrid rocket proposed twenty years ago by the authors recently recaptured the attention of researchers for its virtues such as no s (oxidizer to fuel mass ratio) shift during firing and good throttling characteristics. This paper is the first report verifying these virtues using a laboratory scale motor. There are several requirements for realizing this type of hybrid rocket: 1) high fuel filling rate for obtaining an optimal s; 2) small port intervals for increasing port merging rate; 3) ports arrayed across the entire fuel section. Because these requirements could not be satisfied by common manufacturing methods, no previous researchers have conducted experiments with this kind of hybrid rocket. Recent advances in high accuracy 3D printing now allow for fuel to be produced that meets these three requirements. The fuel grains used in this study were produced by a high precision light polymerized 3D printer. Each grain consisted of an array of 0.3 mm diameter ports for a fuel filling rate of 98% .The authors conducted several firing tests with various oxidizer mass flow rates and chamber pressures, and analysed the results, including s history, using a new reconstruction technique. The results show that s remains almost constant throughout tests of varying oxidizer mass flow rates, and that regression rate in the axial direction is a nearly linear function of chamber pressure with a pressure exponent of 0.996.

Key Words
hybrid rockets; stabilized combustion; regression characteristics

Address
Yuji Saito, Toshiki Yokoi: Graduate school of Engineering, Hokkaido University, Japan
Lukas Neumann: Faculty of Engineering, Technical University of Berlin, Germany
Hiroyuki Yasukochi, Kentaro Soeda: Institute for Photon Science and Technology, The University of Tokyo, Japan
Tsuyoshi Totani, Masashi Wakita and Harunori Nagata: Faculty of Engineering, Hokkaido University, Japan

Abstract
With rapid growth in the complexity of large scale engineering systems, the application of multidisciplinary analysis and design optimization (MDO) in the engineering design process has garnered much attention. MDO addresses the challenge of integrating several different disciplines into the design process. Primary challenges of MDO include computational expense and poor scalability. The introduction of a distributed, collaborative computational environment results in better utilization of available computational resources, reducing the time to solution, and enhancing scalability. SORCER, a Java-based network-centric computing platform, enables analyses and design studies in a distributed collaborative computing environment. Two different optimization algorithms widely used in multidisciplinary engineering design-VTDIRECT95 and QNSTOP-are implemented on a SORCER grid. VTDIRECT95, a Fortran 95 implementation of D. R. Jones‟ algorithm DIRECT, is a highly parallelizable derivative-free deterministic global optimization algorithm. QNSTOP is a parallel quasi-Newton algorithm for stochastic optimization problems. The purpose of integrating VTDIRECT95 and QNSTOP into the SORCER framework is to provide load balancing among computational resources, resulting in a dynamically scalable process. Further, the federated computing paradigm implemented by SORCER manages distributed services in real time, thereby significantly speeding up the design process. Part 1 covers SORCER and the algorithms, Part 2 presents results for aircraft panel design with curvilinear stiffeners.

Key Words
service-oriented computing; federated computing; deterministic global optimization; stochastic optimization; multidisciplinary design

Address
Chaitra Raghunath: Department of Computer Science, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA
Layne T. Watson: Department of Computer Science, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA; Department of Mathematics, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA; Department of Aerospace & Ocean Engineering, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA
Mohamed Jrad, Rakesh K. Kapania: Department of Aerospace & Ocean Engineering, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA
Raymond M. Kolonay: AFRL/RQVC, 2210 8th Street, Bldg. 146, Wright-Patterson Air Force Base, Dayton, OH 45433, USA

Abstract
With rapid growth in the complexity of large scale engineering systems, the application of multidisciplinary analysis and design optimization (MDO) in the engineering design process has garnered much attention. MDO addresses the challenge of integrating several different disciplines into the design process. Primary challenges of MDO include computational expense and poor scalability. The introduction of a distributed, collaborative computational environment results in better utilization of available computational resources, reducing the time to solution, and enhancing scalability. SORCER, a Java-based network-centric computing platform, enables analyses and design studies in a distributed collaborative computing environment. Two different optimization algorithms widely used in multidisciplinary engineering design-VTDIRECT95 and QNSTOP-are implemented on a SORCER grid. VTDIRECT95, a Fortran 95 implementation of D. R. Jones\' algorithm DIRECT, is a highly parallelizable derivative-free deterministic global optimization algorithm. QNSTOP is a parallel quasi-Newton algorithm for stochastic optimization problems. The purpose of integrating VTDIRECT95 and QNSTOP into the SORCER framework is to provide load balancing among computational resources, resulting in a dynamically scalable process. Further, the federated computing paradigm implemented by SORCER manages distributed services in real time, thereby significantly speeding up the design process. Part 1 covers SORCER and the algorithms, Part 2 presents results for aircraft panel design with curvilinear stiffeners.

Key Words
service-oriented computing; federated computing; deterministic global optimization; stochastic optimization; multidisciplinary design

Address
Chaitra Raghunath: Department of Computer Science, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA
Layne T. Watson: Department of Computer Science, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA; Department of Mathematics, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA; Department of Aerospace & Ocean Engineering, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA
Mohamed Jrad, Rakesh K. Kapania: Department of Aerospace & Ocean Engineering, Virginia Polytechnic Institute & State University, Blacksburg, VA 24061, USA
Raymond M. Kolonay: AFRL/RQVC, 2210 8th Street, Bldg. 146, Wright-Patterson Air Force Base, Dayton, OH 45433, USA

Abstract
Kalman filter based spacecraft attitude estimation has been used in many space missions and has been widely discussed in literature. While some models in spacecraft attitude estimation include spacecraft dynamics, most do not. To our best knowledge, there is no comparison on which model is a better choice. In this paper, we discuss the reasons why spacecraft dynamics should be considered in the Kalman filter based spacecraft attitude estimation problem. We also propose a reduced quaternion spacecraft dynamics model which admits additive noise. Geometry of the reduced quaternion model and the additive noise are discussed. This treatment is easier in computation than the one with full quaternion. Simulations are conducted to verify our claims.

Key Words
extended Kalman filter; linearization; spacecraft attitude estimation

Address
Yaguang Yang: Office of Research, NRC, 21 Church Street, Rockville, 20850, USA
Zhiqiang Zhou: NASA Langley Research Center, Hampton, VA 23681, USA


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