A Moving Frame Algorithm for High Mach Number Hydrodynamics

We present a new approach to Eulerian computational fluid dynamics that is designed to work at high Mach numbers encountered in astrophysical hydrodynamic simulations. The Eulerian fluid conservation equations are solved in an adaptive frame moving with the fluid where Mach numbers are minimized. The moving frame approach uses a velocity decomposition technique to define local kinetic variables while storing the bulk kinetic components in a smoothed background velocity field that is associated with the grid velocity. Gravitationally induced accelerations are added to the grid, thereby minimizing the spurious heating problem encountered in cold gas flows. Separately tracking local and bulk flow components allows thermodynamic variables to be accurately calculated in both subsonic and supersonic regions. A main feature of the algorithm, that is not possible in previous Eulerian implementations, is the ability to resolve shocks and prevent spurious heating where both the preshock and postshock Mach numbers are high. The hybrid algorithm combines the high resolution shock capturing ability of the second-order accurate Eulerian TVD scheme with a low-diffusion Lagrangian advection scheme. We have implemented a cosmological code where the hydrodynamic evolution of the baryons is captured using the moving frame algorithm while the gravitational evolution of the collisionless dark matter is tracked using a particle-mesh N-body algorithm. The MACH code is highly suited for simulating the evolution of the IGM where accurate thermodynamic evolution is needed for studies of the Lyman alpha forest, the Sunyaev-Zeldovich effect, and the X-ray background. Hydrodynamic and cosmological tests are described and results presented. The current code is fast, memory-friendly, and parallelized for shared-memory machines.Comment: 19 pages, 5 figure

Experimental and theoretical analyses of three-dimensional surface crack propagation

2011-2012 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Nonclassicality of photon-added squeezed vacuum and its decoherence in thermal environment

We study the nonclassicality of photon-added squeezed vacuum (PASV) and its decoherence in thermal environment in terms of the sub-Poissonian statistics and the negativity of Wigner function (WF). By converting the PASV to a squeezed Hermite polynomial excitation state, we derive a compact expression for the normalization factor of m-PASV, which is an m-order Legendre polynomial of squeezing parameter r. We also derive the explicit expression of WF of m-PASV and find the negative region of WF in phase space. We show that there is an upper bound value of r for this state to exhibit sub-Poissonian statistics increasing as m increases. Then we derive the explicit analytical expression of time evolution of WF of m-PASV in the thermal channel and discuss the loss of nonclassicality using the negativity of WF. The threshold value of decay time is presented for the single PASV.Comment: 14 pages and 7 figure

Evaluation of different setups for the measurement of drug penetration into the nail

The aim of this study was to conduct permeation using 3 different setups: Franz diffusion cells, wet cotton ball, and agar gel to investigate whether the same permeation results would be obtained with a nail lacquer formulation. Subsequently, 4 nail lacquers were used in 2 of permeation setups to detect whether the order of best to worst formulation was the same in the different setups

Transformation of UML interaction diagrams into contract specifications for object-oriented testing

Testing is an important means to ensure the quality of software systems. Contract specification can be used to formally specify the cluster level of object-oriented software, which can then be tested using TACCLE, an advanced methodology for object-oriented testing. The use of formal specifications as a testing base has many advantages. However, such specifications are not easily understood and therefore not widely used in the software industry. On the other hand, UML, a semi-formal modeling language, is becoming increasingly popular and widely accepted. In particular, UML interaction diagrams specify the dynamic, interacting behavior among the objects of an object-oriented system. If the transformation of UML interaction diagrams into Contract specifications can be automated, the TACCLE methodology can be applied directly to test object-oriented software at the cluster level. In this paper, a method to transform UML interaction diagrams into Contract specifications is proposed based on the UML meta-model. A prototype has been developed. © 2007 IEEE.published_or_final_versio

Realizing serine/threonine ligation: scope and limitations and mechanistic implication thereof

published_or_final_versio

Self-focused acoustic ejectors for viscous liquids

Author name used in this publication: K. W. kwok2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Narrowband Single-Pole Double-Throw Filtering Switch Based on Dielectric Resonator

© 2001-2012 IEEE. In this letter, a narrowband single-pole double-throw (SPDT) filtering switch based on dielectric resonators (DRs) is presented. It consists of two DRs shared by two channels for size reduction. Printed circuit boards are embedded in the metal cavity to integrate the PIN diodes. The switching between two channels is enabled by controlling the PIN diodes connected to the two output feeding lines. The electromagnetic field distributions of the DR at the TE -{11\delta } mode are studied to control the coupling between the DR and two output feeding lines. When one channel is on, the PIN diode for this channel is turned off, which does not introduce loss and affect the linearity. For the off-state channel, isolation is obtained by controlling the coupling between the DR and output feeding line, which is considerably enhanced. For demonstration, the DR filtering SPDT switch is implemented. The measured results exhibit that the proposed filtering SPDT switch has narrow bandwidth, low loss, high isolation, and high linearity

Low-loss narrowband filtering switch based on coaxial resonators

© 2013 IEEE. In this paper, a narrowband filtering switch with low loss and high selectivity is presented based on coaxial resonators for the first time. PIN diodes mounted on the printed circuit boards are embedded into a coaxial filter to enable ON and OFF states. In the ON-state, the PIN diodes are turned OFF, which do not introduce the loss and affect the linearity. Two transmission zeros are generated by a novel feeding structure, which improves the skirt selectivity. In the OFF-state, the PIN diodes are turned on. Then, lumped capacitors are loaded to the coaxial resonators so that the resonant frequencies of the resonators are changed. The passband at the operating frequency cannot be formed, resulting in high isolation. For demonstration, the coaxial-resonator-based filtering switch is designed and fabricated. Good agreement between simulated and measured results verifies the proposed ideas. Comparison with other reported filtering switches is given. The proposed filtering switch shows the advantages of high Q-factor, relatively compact size, and wide stopband responses, which is attractive in wireless systems