On the logarithmic comparison theorem for integrable logarithmic connections

Let $X$ be a complex analytic manifold, $D\subset X$ a free divisor with jacobian ideal of linear type (e.g. a locally quasi-homogeneous free divisor), $j: U=X-D \to X$ the corresponding open inclusion, $E$ an integrable logarithmic connection with respect to $D$ and $L$ the local system of the horizontal sections of $E$ on $U$. In this paper we prove that the canonical morphisms between the logarithmic de Rham complex of $E(kD)$ and $R j_* L$ (resp. the logarithmic de Rham complex of $E(-kD)$ and $j_!L$) are isomorphisms in the derived category of sheaves of complex vector spaces for $k\gg 0$ (locally on $X$)Comment: Terminology has changed: "linear jacobian type" instead of "commutative differential type"); no Koszul hypothesis is needed in theorem (2.1.1); minor changes. To appear in Proc. London Math. So

Advanced Communication Technology Satellite (ACTS) multibeam antenna analysis and experiment

One of the most important aspects of a satellite communication system design is the accurate estimation of antenna performance degradation. Pointing error, end coverage gain, peak gain degradation, etc. are the main concerns. The thermal or dynamic distortions of a reflector antenna structural system can affect the far-field antenna power distribution in a least four ways. (1) The antenna gain is reduced; (2) the main lobe of the antenna can be mispointed thus shifting the destination of the delivered power away from the desired locations; (3) the main lobe of the antenna pattern can be broadened, thus spreading the RF power over a larger area than desired; and (4) the antenna pattern sidelobes can increase, thus increasing the chances of interference among adjacent beams of multiple beam antenna system or with antenna beams of other satellites. The in-house developed NASA Lewis Research Center thermal/structural/RF analysis program was designed to accurately simulate the ACTS in-orbit thermal environment and predict the RF antenna performance. The program combines well establish computer programs (TRASYS, SINDA and NASTAN) with a dual reflector-physical optics RF analysis program. The ACTS multibeam antenna configuration is analyzed and several thermal cases are presented and compared with measurements (pre-flight)

Electronic excitations and the tunneling spectra of metallic nanograins

Tunneling-induced electronic excitations in a metallic nanograin are classified in terms of {\em generations}: subspaces of excitations containing a specific number of electron-hole pairs. This yields a hierarchy of populated excited states of the nanograin that strongly depends on (a) the available electronic energy levels; and (b) the ratio between the electronic relaxation rate within the nano-grain and the bottleneck rate for tunneling transitions. To study the response of the electronic energy level structure of the nanograin to the excitations, and its signature in the tunneling spectrum, we propose a microscopic mean-field theory. Two main features emerge when considering an Al nanograin coated with Al oxide: (i) The electronic energy response fluctuates strongly in the presence of disorder, from level to level and excitation to excitation. Such fluctuations produce a dramatic sample dependence of the tunneling spectra. On the other hand, for excitations that are energetically accessible at low applied bias voltages, the magnitude of the response, reflected in the renormalization of the single-electron energy levels, is smaller than the average spacing between energy levels. (ii) If the tunneling and electronic relaxation time scales are such as to admit a significant non-equilibrium population of the excited nanoparticle states, it should be possible to realize much higher spectral densities of resonances than have been observed to date in such devices. These resonances arise from tunneling into ground-state and excited electronic energy levels, as well as from charge fluctuations present during tunneling.Comment: Submitted to the Physical Review

Printed circuit board coil design with reduced series resistance for high power inductive wireless power transmission systems

Due to the growing use of the popular wireless power transmission (WPT) technology, an innovative method of coil design and optimization is presented in this paper. This method has been applied to develop spiral printed circuit board (PCB) coils with litz-wire structure. From the geometry definition, the design process is carried out by means of finite element analysis (FEA). In addition, as a complement to the design process, some prototypes of spiral PCB coils were built to contrast the simulation results and experimental measurements by means of the small-signal characterization, which reflects the success of the applied method

Printed circuit board coils of multi-track litz structure for 3.3 kW inductive power transfer system

This paper presents the optimization procedure of an inductive power transmission (IPT) system which utilizes large size spiral printed circuit board (PCB) coils for high- power transfer. Printed circuit boards for coil assembly provides advantages in the manufacturing process through the use of cost- effective flexible fabrication techniques. Furthermore, this kind of construction offers a low profile device, which is of great interest for applications with space constraints. PCB-based IPT system coils can achieve high energy efficiency by applying litz-structure braiding techniques, as investigated in this work, where the objective was to obtain an optimized balance between the conduc- tion losses and proximity losses associated with the number and dimensions of the traces. Considering the geometrical dimensions and manufacturing constraints, we will proceed to obtain the characteristics of the coil to achieve optimal performance. The estimation of coil losses were in part based on finite element simulations, and the results were conveniently processed with the appropriate mathematical methods. Numerical simulation and experimental results were conducted for validation on a prototype suitable to transfer up to 3.3 kW for a transmitter- receiver distance of 10 cm. In the experimental arrangement, a maximum efficiency in the coils of 93% has been measured, and the overall efficiency of 88% has been reached for the entire IPT system