A theoretical and numerical analysis of the measured equation ofinvariance

The measured equation of invariance (MEI) has been previously introduced to efficiently and accurately handle the boundary truncation for finite methods. The present authors give a theoretical analysis that provides several important insights into the capabilities of the MEI. From the numerical study, they can explain why the MEI works better than one would expect. Both the theoretical and the numerical analyses demonstrate that the accuracy of the solution is dependent on the electrical size of the geometry as well as the distance between the mesh boundary and the geometry. From the analysis, the authors propose a new set of metrons that is less sensitive to the excitation than the previously proposed sinusoidal metrons     

Scattering by spherically stratified microwave lens antennas

A comprehensive treatment of scattering by sources in the region of a spherically stratified object composed of discrete shells is presented and compared with measured results. The work encompasses the developments necessary for a thorough understanding of the focusing mechanism of a spherical lens. The method used is a modal technique that employs separation of variables in order to determine an eigenfunction representation of the incident and scattered fields. This formulation provides the Green's function required for the calculation of the scattering from a multiple layered sphere excited by an infinitesimal current element. The algorithm allows both near- and far-field predictions. The scattering by more complicated source field distributions is modeled by applying superposition with the appropriate coordinate transformations. From a practical standpoint, the present analysis allows the limitations of spherical lenses to be determined while providing the information required to optimize the lens design. A system was built based on the new design data, and its measured radiation characteristics are compared to the theoretical predictions. Excellent agreement is observed in most cases     

A partitioning technique for the finite element solution ofelectromagnetic scattering from electrically large dielectric cylinders

A finite element partitioning scheme has been developed to reduce the computational costs of modeling electrically large geometries. In the partitioning scheme, the cylinder is divided into many sections. The finite element method is applied to each section independent of the other sections, and then the solutions in each section are coupled through the use of the tangential field continuity conditions between adjacent sections. Since the coupling matrix is significantly smaller than the original finite element matrix, it is expected that both the CPU time and memory costs can be significantly reduced. The partitioning scheme is coupled to the bymoment method to account for the boundary truncation. Numerical results are presented to demonstrate the efficiency and accuracy of the method     

Coupled electrothermal modeling of microheaters using SPICE

In this paper,,we report a novel simulation approach that computes both the transient and steady state electrothermal behavior in integrated circuit (IC) compatible thermally isolated microheaters. The resulting distribution of heat, current density and temperature, as well as the electrical terminal behavior have been obtained for realistic device structures. The results are based on a two-dimensional solution of the coupled system of partial differential equations that govern both electrical and heat transport in the device. Unlike standard numerical approaches for coupled systems, our technique is based on the behavioural models, available in most commercial circuit simulators (e.g., HSPICE), that allow synthesis of complex, nonlinear, and coupled circuit elements. The simulation results are in excellent agreement with measurement data of steady state and transient terminal characteristics, obtained under conditions of vacuum. We note that this modeling approach allows concurrent simulation (and subsequent optimization) of the performance of both the control electronics as well as the thermal element(s), within the same IC design environment     

On the hot-carrier-induced post-stress interface trap generation inn-channel MOS transistors

A continued fast interface trap generation is observed in n-channel MOS transistors after termination of the hot-carrier stress. The magnitude of this post-stress effect is strongly dependent on the conditions of the preceding stress, on the post-stress conditions and on the process parameters. For measurements at 293 K, a simple model is proposed which is based on the release of hydrogen by the thermal detrapping of holes, and which can explain the observed dependencies. The importance of the post-stress D_it-generation is illustrated for the case of dynamic stress conditions where it can lead to an apparently deviating degradation behavior     

Drain structure optimization for highly reliable deep submicrometern-channel MOSFET

A guideline for n^- fully gate overlapped (FOLD) structure design optimization has been studied. From the viewpoint of reliability, the greatest reduction in substrate current directly leads to the most reliable n^- design for the FOLD structure. The current path modulation phenomenon due to the trapped charge at the n ^- extension region dominates the hot-carrier induced characteristics change for conventional lightly doped drain (LDD) structure with side-wall spacer. This phenomenon is minimized in the FOLD structure due to its higher controllability of the gate electrode than the LDD structure at the n^- extension region. Furthermore, it was also confirmed that the 0.3 μm optimized FOLD structure can achieve high circuit performance at 3.3 V operation, maintaining hot-carrier resistance     

Distribution of total uptime during a given time interval

The distribution of total uptime during a given time interval for a repairable system is obtained. The total uptime is the total amount of time the system is up (in operation) during the interval. It is assumed that: (1) the system starts to operate at the beginning of the interval and alternately takes only the two states, up and down (under repair); (2) repair restores the system to “like-new”. A simple approximation to the distribution function of total uptime for a shorter interval is presented     

Describing collaborative forms: a profile of the team-writingprocess

The paper examines collaborative writing practices students in the Air Force Institute of Technology's Graduate School of Logistics and Acquisition Management use to produce team-authored theses. In analyzing how student writing teams plan, execute, and assess writing activities, the researchers identify and describe some of the forms that collaboration takes, thereby successfully connecting their work within a broader research continuum concerning collaborative writing, particularly when applied in academic settings     

The evolution of communication vehicles: linear progress andcyclical progress

Examines several aspects of communication methods (`vehicles') and the various types of progress that have been made over the years. Much of the progress we have made in communicating is rooted strongly in our past. Much of the future of our communication vehicles will be rooted in our present and our understanding of our present. In this paper, we focus our discussion on six aspects of communication: (1) communication vehicles for teaching and learning; (2) forums for communication-wide interchange of ideas; (3) vehicles for search-and-retrieval of information; (4) the richness of the communication media set; (5) venues of communication-where we communicate and the tools we use; and (6) the idea of linearity in communication