Green's Matrix for a Second Order Self-Adjoint Matrix Differential Operator

A systematic construction of the Green's matrix for a second order, self-adjoint matrix differential operator from the linearly independent solutions of the corresponding homogeneous differential equation set is carried out. We follow the general approach of extracting the Green's matrix from the Green's matrix of the corresponding first order system. This construction is required in the cases where the differential equation set cannot be turned to an algebraic equation set via transform techniques.Comment: 19 page

The AMSC mobile satellite system

The American Mobile Satellite Consortium (AMSC) Mobile Satellite Service (MSS) system is described. AMSC will use three multi-beam satellites to provide L-band MSS coverage to the United States, Canada and Mexico. The AMSC MSS system will have several noteworthy features, including a priority assignment processor that will ensure preemptive access to emergency services, a flexible SCPC channel scheme that will support a wide diversity of services, enlarged system capacity through frequency and orbit reuse, and high effective satellite transmitted power. Each AMSC satellite will make use of 14 MHz (bi-directional) of L-band spectrum. The Ku-band will be used for feeder links

Effect of Nozzle Divergence Angle on Plume Expansion In Outer-Space Conditions

We carry out numerical simulations to investigate the effect of nozzle divergence angle on back flow of plume expansion into rarefied atmosphere. Results are obtained using open source compressible computational fluid dynamics (CFD) solver. Non-equilibrium slip and jump boundary conditions for velocity and temperature are implemented to capture rarefaction rarefaction effects in the slip flow regime. The solver has been validated with the experimental data for a nozzle flow in the slip flow regime. We explore the non-linear non-equilibrium gas flow physics of a supersonic jet expansion. We report results of pressure, heat and drag coefficients for different divergent angles ( 12 0 , 15 0 and 20 0 ) at 80 km altitude conditions. The slip based results for heat loads significantly under-predict the no-slip ones, while for pressure and drag coefficients, deviations are found to be minute. It is noticed that thrust coefficient of nozzle increases with increase in divergence angle, however, nozzle with divergent angle of 15 0 led to minimum drag and heat transfer load on the critical region. The current study is important from the perspective of the overall aero-thermodynamic design of a typical supersonic rocket model operating under rarefied conditions

An examination of the relationship of governance structure and performance: Evidence from banking companies in Bangladesh

Corporate governance has become increasingly important in developed and developing countries just after a series of corporate scandals and failures in a number of countries. Corporate governance structure is often viewed as a means of corporate success despite prior studies reveal mixed, somewhere conflicting and ambiguous, and somewhere no relationship between governance structure and performance. This study empirically investigates the relationship between corporate governance mechanisms and financial performance of listed banking companies in Bangladesh by using two multiple regression models. The study reveals that a good number of companies do not comply with the regulatory requirements indicating remarkable shortfall in corporate governance practice. The companies are run by the professional managers having no duality and no ownership interest for which they are compensated by high remuneration to curb agency conflict. Apart from some inconsistent relationship between some corporate variables, the corporate governance mechanisms do not appear to have significant relationship with financial performances. The findings reveal an insignificant negative impact or somewhere no impact of independent directors and non-independent non-executive directors on the level of performance that strongly support the concept that the managers are essentially worthy of trust and earn returns for the owners as claimed by stewardship theory. The study provides support for the view that while much emphasis on corporate governance mechanisms is necessary to safeguard the interest of stakeholders; corporate governance on its own, as a set of codes or standards for corporate conformance, cannot make a company successful. Companies need to balance corporate governance mechanisms with performance by adopting strategic decision and risk management with the efficient utilization of the organization’s resources

Mobile satellite service in the United States

Mobile satellite service (MSS) has been under development in the United States for more than two decades. The service will soon be provided on a commercial basis by a consortium of eight U.S. companies called the American Mobile Satellite Consortium (AMSC). AMSC will build a three-satellite MSS system that will offer superior performance, reliability and cost effectiveness for organizations requiring mobile communications across the U.S. The development and operation of MSS in North America is being coordinated with Telesat Canada and Mexico. AMSC expects NASA to provide launch services in exchange for capacity on the first AMSC satellite for MSAT-X activities and for government demonstrations

Investigation of cycling-induced microstructural degradation in silicon-based electrodes in lithium-ion batteries using X-ray nanotomography

The microstructural degradation of a composite silicon electrode at different stages in its cycle life was investigated in 3D using X-ray nano-computed tomography. A reconstructed volume of 36 μm × 27 μm × 26 μm from the composite electrode was imaged in its pristine state and after 1, 10 and 100 cycles. Particle fracturing and phase transformation was observed within the electrode with increased cycling. In addition, a distinct, lower X-ray attenuating phase was clearly resolved, which can be associated with surface film formation resulting from electrolyte breakdown and with silicon particle phase transformation. Changes in quantified microstructural properties such as phase volume fraction and particle specific surface area were tracked. Electrode performance loss is associated with loss of active silicon. These imaging results further highlight the capability of high resolution X-ray tomography to investigate the role of electrode microstructure in battery degradation and failure

Hybrid Thermo-Electrochemical In Situ Instrumentation for Lithium-Ion Energy Storage

Current “state‐of‐the‐art” monitoring and control techniques for lithium‐ion cells rely on full‐cell potential measurement and occasional surface temperature measurements. However, Li‐ion cells are complex multi‐layer devices and as such these techniques have poor resolution, limiting applicability. In this work we develop hybrid thermo‐electrochemical sensing arrays placed within the cell. The arrays are integrated into A5 pouch cells during manufacture and are used to create thermal maps in parallel with anode and cathode electrochemical data. The sensor array can be adapted to a range of cell formats and chemistries and installed into commercial or other industrially relevant cells, incorporating enhanced thermal and electrochemical diagnostic capability into a standard cell build