Soft vibrational mode associated with incommensurate orbital order in multiferroic CaMn7_7O12_{12}

We report inelastic light scattering measurements of lattice dynamics related to the incommensurate orbital order in $\mathrm{CaMn_7O_{12}}$. Below the ordering temperature $T_\mathrm{o} \approx 250 \,\mathrm{K}$, we observe extra phonon peaks as a result of Brillouin-zone folding, as well as a soft vibrational mode with a power-law $T$-dependent energy, $\Omega = \Omega_{0}(1 - T/T_{\mathrm{o}})^{1/2}$. This temperature dependence demonstrates the second-order nature of the transition at $T_\mathrm{o}$, and it indicates that the soft mode can be regarded as the amplitude excitation of the composite order parameter. Our result strongly suggests that the lattice degrees of freedom are actively involved in the orbital-ordering mechanism.Comment: 7 pages, 8 figure

Design, fabrication and characterization of monolithic embedded parylene microchannels in silicon substrate

This paper presents a novel channel fabrication technology of bulk-micromachined monolithic embedded polymer channels in silicon substrate. The fabrication process favorably obviates the need for sacrifical materials in surface-micromachined channels and wafer-bonding in conventional bulk-micromachined channels. Single-layer-deposited parylene C (poly-para-xylylene C) is selected as a structural material in the microfabricated channels/columns to conduct life science research. High pressure capacity can be obtained in these channels by the assistance of silicon substrate support to meet the needs of high-pressure loading conditions in microfluidic applications. The fabrication technology is completely compatible with further lithographic CMOS/MEMS processes, which enables the fabricated embedded structures to be totally integrated with on-chip micro/nano-sensors/actuators/structures for miniaturized lab-on-a-chip systems. An exemplary process was described to show the feasibility of combining bulk micromachining and surface micromachining techniques in process integration. Embedded channels in versatile cross-section profile designs have been fabricated and characterized to demonstrate their capabilities for various applications. A quasi-hemi-circular-shaped embedded parylene channel has been fabricated and verified to withstand inner pressure loadings higher than 1000 psi without failure for micro-high performance liquid chromatography (µHPLC) analysis. Fabrication of a high-aspect-ratio (internal channel height/internal channel width, greater than 20) quasi-rectangular-shaped embedded parylene channel has also been presented and characterized. Its implementation in a single-mask spiral parylene column longer than 1.1 m in a 3.3 mm × 3.3 mm square size on a chip has been demonstrated for prospective micro-gas chromatography (µGC) and high-density, high-efficiency separations. This proposed monolithic embedded channel technology can be extensively implemented to fabricate microchannels/columns in high-pressure microfludics and high-performance/high-throughput chip-based micro total analysis systems (µTAS)

Cooperative Robots

The topic of this master thesis is cooperative robots. The master and slave configuration is to be used for cooperative tasks and the task chosen is to move a flexible beam together. A trajectory is fed to the master robot to move it to the desired positions. The slave robot then follows the movement of the master robot by force control using force measurements from a force sensor. All experiments are performed in the Robotics Laboratory at the Department of Automatic Control at Lund Institute of Technology. The robots used are an ABB IRB 6 robot and an ABB IRB 2000 robot. The ABB IRB 6 robot is assigned to be the master robot and the ABB IRB 2000 robot as the slave robot. The ABB IRB 2000 robot is equipped with a force and torque sensor of type JR3 for force control. The thesis can be divided broadly into three parts. The first part is a background study of the robot systems and kinematics, on path and trajectory generation and also on the various robot force control schemes. The second part is about optimal trajectory generation. The desired path is first expressed in terms of path index in Cartesian space. It is then converted to joint space with variable step size to ensure that the deviation from the original path is kept within a given limit. The optimal trajectory is then generated using Linear Programming. The third part consists of the application of parallel force/motion control schemes to the slave robot to enable it to follow the master robot. The motion controller is simply the builtin controllers of the IRB 2000 robot. The force controllers used are direct force, impedance and admittance controllers. The schemes are first tested in Matlab Simulink where the robots are simulated by a first order system for each joint. The force measurements are generated by a contact model which simulates the contact forces and torques between the gripper of the IRB 2000 robot and the beam. The resulting joint values are then sent to a Java visualization program written in the platform Eclipse

Mirror energy difference and the structure of loosely bound proton-rich nuclei around A = 20

The properties of loosely bound proton-rich nuclei around A = 20 are investigated within the framework of nuclear shell model. In these nuclei, the strength of the effective interactions involving the loosely bound proton s1=2 orbit are significantly reduced in comparison with those in their mirror nuclei. We evaluate the reduction of the effective interaction by calculating the monopole-baseduniversal interaction (VMU) in the Woods-Saxon basis. The shell-model Hamiltonian in the sd shell, such as USD, can thus be modified to reproduce the binding energies and energy levels of the weakly bound proton-rich nuclei around A = 20. The effect of the reduction of the effective interaction on the structure and decay properties of these nuclei is also discussed.Comment: accepted by Physical Review

Decomposing and valuing callable convertible bonds: a new method based on exotic options

In the framework of Black-Scholes-Merton option pricing models, by employing exotic options instead of plain options or warrants, this paper presents an equivalent decomposition method for usual Callable Convertible Bonds (CCB). Furthermore, the analytic valuation formulae for CCB are worked out by using the analytic formulae for those simpler securities decomposed from CCB. Moreover, this method is validated by comparing with Monte Carlo simulation. Besides, the effects of call clauses, coupon clauses and soft call condition clauses are analyzed respectively. These give lots of new insights into the valuation and analysis of CCB and much help to hedge their risks.Callable convertible bonds; Equivalent decomposition; Up-and-out calls; American binary calls; Derivative pricing

Global dynamics of a harmonically excited oscillator with a play : Numerical studies

This work was supported by the National Secretariat of Science, Technology and Innovation of Ecuador (SENESCYT); the Escuela Superior Politécnica del Litoral of Ecuador (ESPOL); the National Natural Science Foundation of China (11272268, 11572263) and Scholarship of China. A.S.E. Chong and Y. Yue acknowledge the hospitality of the Centre of Applied Dynamics Research at the University of Aberdeen.Peer reviewedPostprin