When studying the structure formation and fragmentation of complex atomic and nuclear systems it is preferable to start with simple systems where all details can be explored. Some of the knowledge gained from studies of atomic dimers can be generalised to more complex systems. Adding a third atom to an atomic dimer gives a first chance to study how the binding between two atoms is affected by a third. Few-body physics is an intermediate area which helps us to understand some but not all phenomena in many-body physics. Very weakly bound, spatially very extended quantum systems with a wave function reaching far beyond the classical forbidden region and with low angular momentum are characterized as halo systems. These unusual quantum systems, first discovered in nuclear physics may also exist in systems of neutral atoms. Since the first clear theoretical prediction in 1977, of a halo system possessing an Efimov state, manifested in the excited state of the bosonic van der Waals helium trimer 42He3, small helium and different spin-polarised halo hydrogen clusters and their corresponding isotopologues have been intensively studied the last three decades. In the work presented here, the existence of the spin-polarized tritium trimer ground state, 31H3, is demonstrated, verifying earlier predictions, and the system's properties elucidated. Detailed analysis has found no found evidence for other bound states and shape resonances in this system. The properties of the halo helium trimers, 42He3 and 42He2-32He have been investigated. Earlier predictions concerning the ground state energies and structural properties of these systems are validated using our three-dimensional finite element method. In the last part of this work we present results on the bound states and structural properties of the van der Waals bosonic atomic trimers Ne3 and Ar3. We believe to be the first to find evidence of a possible shape resonance just above the three-body dissociation limit of the neon trimer.

This article aims to design an innovative polishing method that can do polishing job to a complicated axial symmetric free surface. The main task of the system is to increase the precision of a middle size (diameter range from 50mm to 150mm) free surface with low precision (form error is larger than 10£gm, even reach few hundred £gm. By using the developed polishing system, the precision is expected to reach and order of sub-micron. It is a machining method which able to outcome a precise free surface, and also a high efficient free surface machining method compared to machining technique nowadays. At the beginning of this article, a logical thinking method will be used to set up a number of sub-targets from the task of the article. From those sub-targets, the keys of the polishing method would come out to accomplish the task. They are: 1.The machining tool is deformable and able to match up the shape of the surface of the tool to enlarge the polishing area. This will increase the efficiency of the machining method; 2.The pressure distribution between the tool and work piece is controllable to let the surface area with larger error form has larger machining rate. By accomplish the sub-targets above, a set of form error compensate strategy can be use to remove the error profile of the free surface with high efficiency. To increase the efficiency of the polishing system, the analysis of the force guide by ANSYS (a finite element analysis software) will be done to create a relation between the force applied and the pressure distribution. This will make the pressure distribution construction task easy and the efficiency of polishing will be increased. According to the machining method designed above, a prototype polishing machine will be designed, and a series of experiments will be done on the designed prototype polishing machine to test the workability of the polishing method. The outcome of the experiments shows that the machine not only has good repeatability, but also has a very high machining efficiency. Besides, the machining distribution experiment shows that the machining method has ability to remove the error distribution from the free surface. It means that is able to do precision machining job to the free surface.

Recently, the high-power light-emitting diodes (LEDs) have been used from the traditional indicator purpose to general illumination purpose. The operating environment and requirement has been more severe. The long operating life high efficiency and high reliability are its main feature attracting the lighting community to this technology. The effect of operating temperature on the degradations of high-power blue LEDs is studied in this thesis. The experiment, measurements, and finite element simulations were conducted to investigate the possible causes of LED degradation. The influence of LED material degeneration on the radiometric pattern was analyzed by tracing rays simulation. Different groups of sample LEDs produced by Lumileds, Unity opto technology Co., and Everlight electronics Co. were studied. Different operating ambient temperatures, e.g. 80oC, 100 oC, and 120 oC, were considered in the accelerated aging test. Experimental results indicated that yellowing, carbonization, gel degeneration, lens chapping and deformation were observed during the test. Results also indicated that the operating temperature is the key factor for LED failure mechanism, that is, different operating ambient temperature may lead to different degradation phenomenon. Numerical simulation results shown that the creep caused by high temperature and thermal stress would cause solder takeoff. This takeoff defects were observed in experimental results. Through ray tracing simulation, it is assured that gel degeneration would change the radiometric pattern of the LED significantly.

In order to simulate both physically and visually realistic soft tissuedeformations, the Finite Element Method (FEM) is the mostpopular choice in the literature. However it is non-trivial to modelcomplex behaviour of soft tissue with sufficient refresh rates, especiallyfor haptic force feedback which requires an update rate ofthe order of 1 kHz. In this study the use of asynchronous regions isproposed to speed up the solution of FEM equations in real-time. Inthis way it is possible to solve the local neighborhood of the contactwith high refresh rates, while evaluating the more distant regions atlower frequencies, saving computational power to model complexbehaviour within the contact area. Solution of the different regionsusing different methods is also possible. To attain maximum efficiencythe size of the regions can be changed, in real-time, in responseto the size of the deformation.

There are many causes of structural failure. One of the most important factors leading to material failure is residual stress. This stress represents effects left in structures after processing or removal of external loads including changes in shape and crystallite size. In aggregate, residual stress changes the mechanical behaviour of materials. Various measurement techniques encompassing destructive, semi destructive, and non-destructive testing can be used to measure residual stresses. Thin plates are common in engineering applications. This thesis analyzes residual stresses on circular AISI 1020 steel alloy plates after removal of external loads using two-dimensional X-ray diffraction. Two identical thin circular plates are used in this experiment; one of which is statically loaded. The other plate is used as a control specimen. Residual stresses in the plates are measured using two-dimensional X-ray diffraction and the measurements are compared to those obtained using finite element analysis. It was found that experimentally measured residual stress occurred due to manufacture processing. Also, modules A and B showed the external effect of applying not enough to reach the plastic region to deform specimen 2 and obtain residual stress results distribution.

The objective of this research was to better understand how impact angle influences headform dynamic response and brain tissue deformation. A bare headform was impacted using a pneumatic linear impactor at 5.5 m/s. The impacts were directed on the front and side location at angles of 0, 5, 10 and 15° rightward rotations as well as -5, -10 and -15° (leftward) rotations at the side to examine the characteristics of the head and neckform on the results. Peak resultant linear and rotational accelerations from the headform as well as peak maximum principal strain (MPS) and von Mises stress (VMS) estimated from a brain finite element model were used to measure the effect of impact angle. Significant results were dependent upon the impact angle and location as well as the dependent variable used for comparison (p <0.05). Impact angle produced significant differences in rotational acceleration and MPS at both the front and side; however angle only had an effect on VMS and linear acceleration at the front and side locations, respectively. These findings show that the effect of impact angle is asymmetrical and is specific to the dependent variable. This study suggests that varying impact angle alone may not be as influential on headform dynamic response and brain tissue deformation and that the severity of an impact may be more of a function of how both location and angle create high risk conditions.

Micro-motion devices may share a common architecture such that they have a main body of compliant material and some direct actuation elements (e.g., piezoelectric element). The shape of such a compliant material is designed with notches and holes on it, and in this way one portion of the material deforms significantly with respect to other portions of the material a motion in the conventional sense of the rigid body mechanism. The devices of this kind are called compliant mechanisms. Computer tools for the kinematical and dynamic motion analysis of the compliant mechanism are not well-developed. In this thesis a study is presented towards a finite element approach to the motion analysis of compliant mechanisms. This approach makes it possible to compute the kinematical motion of the compliant mechanism within which the piezoelectric actuation element is embedded, as opposed to those existing approaches where the piezoelectric actuation element is either ignored or overly simplified. Further, the developed approach allows computing the global stiffness and the natural frequency of the compliant mechanism. This thesis also presents a prototype compliant mechanism and a test bed for measuring various behaviors of the prototype mechanism. It is shown that the developed approach can improve the prediction of motions of the compliant mechanism with respect to the existing approaches based on a comparison of the measured result (on the prototype) and the simulated result. The approach to computation of the global stiffness and the natural frequency of the compliant mechanism is validated by comparing it with other known approaches for some simple mechanisms.

The mechanism of soil-reinforcement interaction for a reinforced embankment on soft clay has been explored by conducting a parametric study using a coupled non-linear elastoplastic finite element program. One of the major issues in the design of a reinforced embankment on soft clay is the magnitude of tension that can be mobilized in the geosynthetic reinforcement. Previous research using geotechnical centrifuge modelling and present research using finite element modelling has confirmed that the tension mobilized in the reinforcement is only of the order of active lateral thrust in the embankment. The parametric study has revealed that the soil-reinforcement interaction mechanism depends on the ratio of embankment height to the depth of the clay layer. The embankment behaves similar to a rigid footing in case of deep clay deposit. In this case, the failure mechanism is similar to a slip circle and there is very little contribution from the clay-reinforcement interface towards the mobilization of reinforcement tension. However, if the depth of clay deposit is small, the soil-reinforcement interaction mode is similar to direct shear failure and slip surface is located close to the clay-reinforcement interface. In this case, the contribution of clay-reinforcement interface towards the tension mobilized in the reinforcement is higher and therefore, the contribution of the reinforcement towards overall stability of the embankment is greater. Based on the results of the parametric study a novel serviceability criterion is proposed that aims to limit the lateral deformation of the clay foundation at the toe of the embankment by limiting the allowable mobilized tension in the reinforcement. A simple procedure for the evaluation of the efficiency of soil-reinforcement interface for reinforced embankments on soft clays is also proposed. The validity of the proposed serviceability criterion and the design charts was successfully tested using two field case studies. Sackville test embankment constructed to failure in 1989 and a levee test section that remained serviceable after construction in 1987 at Plaquemine, Louisiana were able to confirm the validity of the serviceability criterion proposed in the present study.

<p>Methodologies for the analysis and computer simulations of active optimal vibration control of complex elastic structures are considered. The structures, generally represented by a large number of degrees of freedom (DOF), are to be controlled by a comparatively small number of actuators.</p><p>Various techniques presently available to solve the optimal control problems are briefly discussed. A Parametric optimization technique that is versatile enough to solve almost any type of optimization problems is found to give poor accuracy and is time consuming. More promising is the optimality equations approach, which is based on Pontryagins principle. Several new numerical procedures are developed using this approach. Most of the problems in this thesis are analysed in the modal space. Even complex structures can be approximated accurately in the modal space by using only few modes. Different techniques have been first applied to the cases where the number of modes to control was the same as the number of actuators (determined optimal control problems), then to cases in which the number of modes to control is larger than the number of actuators (overdetermined optimal control problems). </p><p>The determined optimal control problems can be solved by applying the Independent Modal Space Control (IMSC) approach. Such an approach is implemented in the Beam Analogy (BA) method that solves the problem numerically by applying the Finite Element Method (FEM). The BA, which uses the ANSYS program, is numerically very efficient. The effects of particular optimization parameters involved in BA are discussed in detail. Unsuccessful attempts have been made to modify this method in order to make it applicable for solving overdetermined or underactuated problems. </p><p>Instead, a new methodology is proposed that uses modified optimality equations. The modifications are due to the extra constraints present in the overdetermined problems. These constraints are handled by time dependent Lagrange multipliers. The modified optimality equations are solved by using symbolic differential operators. The corresponding procedure uses the MAPLE programming, which solves overdetermined problems effectively despite of the high order of differential equations involved.</p><p>The new methodology is also applied to the closed loop control problems, in which constant optimal gains are determined without using Riccatis equations.</p>

This work develops a methodology for full engine FEA simulation of the fan blade off containment test for a jet engine using LS-Dyna. The fan blade off containment test is a safety requirement involving the intentional release of a fan blade when the engine is running at full power. The released blade must not pierce or fracture the engine cases during the impact or rotating unbalance. The novel feature of the LS-Dyna simulation is the extensive full engine geometry as well as the widespread use of nonlinearities (mainly plasticity and friction) to absorb the large kinetic energies of the engine rotors. The methodology is simple to use, runs quickly and is being recognized by industry as a contender for widespread implementation. Future applications look promising enough that the methodology warrants further development and refinement.