Computer-aided vulnerability analysis of a digital-to-analog converter

Thirty discrete heterojunction bipolar transistors fabricated in IBM's SiGe 7HP process were irradiated at dose rates of 0.013 rad(Si)/s, 0.11 rad(Si)/s and 171 rad(Si)/s to determine their sensitivity to total-dose irradiation and dose-rate effects. All devices tested showed less than 4% change in beta 0.6% change in turn on voltage. In addition, there was no measurable enhancement of degradation due to low dose-rate irradiation.

The authors present an electrical characterization of discrete bipolar junction transistor (BJT) devices, with nonuniform doped emitter and base zones. The measurement of the I-V and C-V characteristics of the emitter-base and the collector-base junctions and the common emitter current gain allows to determine relevant parameters of the device. These are the built-in voltage of both junctions, the impurity gradient profiles, the electrical area of both junctions, the base and the emitter Gummel numbers and the collector doping. The whole experiment can be conducted in a laboratory session of 3-4 hour length and it is specifically addressed to students taking lectures in semiconductor device physics. The results obtained give a deep insight into both the physical structure and the physical processes involved in the transistor behavior.

In order to study the Single Event Transient (SET) sensitivity of discrete bipolar junction transistors, laser tests conducted at EADS Innovation Works in Sureness are presented and discussed. A number of different BJT samples have been tested in different operating conditions. The tests demonstrate that: discrete BJTs are indeed sensitive to collected charge; the most sensitive region is the collector/base junction and that the different internal structure gives different SET shapes. We present measurements, simulations and a comparison for the SETs modeled in PSPICE and tested with a laser.

The design of a digitally gain controlled high-voltage non-inverting bipolar linear amplifier is presented. This cost efficient and relatively simple circuit has stable operation range from dc to 90 kHz under the load of 10 kΩ and 39 pF. The amplifier can swing up to 360 V(pp) under these conditions and it has 2.5 μs rise time. The gain can be changed by the aid of JFETs. The amplifiers have been realized using a combination of operational amplifiers and high-voltage discrete bipolar junction transistors. The circuit details and performance characteristics are discussed.

Prognostics and health management integrated into complex systems and platforms such as the joint strike fighter (JSF) and future combat systems (FCS) will enable autonomic logistics and significant reductions in lifetime operating costs. VEXTEC has developed a system of physics of failure based modeling for electronics components which can predict component reliability without adding weight, sensors or complexity to the system. These models incorporate the already available environmental and usage data to evaluate the stresses on individual components within a system to provide an overall health indication for that system. Reliability modeling allows for timely and efficient planning of spares, maintenance and readiness to meeting operation needs and reduce cost for the armed forces. This paper shows the development and implementation of the process.

Multi-objective design approach of passive filters for single-phase distributed energy grid integration systems using particle swarm optimization

According to Szyperski, “a software component is a unit of composition with contractually specified interfaces and explicit context dependencies only”. But it is well known that these contractually specified interfaces should go well beyond mere syntactic aspects: they should also involve functional, synchronization and Quality of Service (QoS) aspects. In large, mission-critical component based systems, it is also particularly important to be able to explicitly relate the QoS contracts attached to provided interfaces with the QoS contracts obtained from required interfaces. In this paper we propose a language called QoSCL (defined as an add-on to the UML2.0 component model) to let the designer explicitly describe and manipulate these higher level contracts and their dependencies. We show how the very same QoSCL contracts can then be exploited for (1) validation of individual components, by automatically weaving contract monitoring code into the components; and (2) validation of a component assembly, including getting end-to-end QoS information inferred from individual component contracts, by automatic translation to a Constraint Logic Programming language. We illustrate our approach with the example of a GPS (Global Positioning System) software component, from its functional and contractual specifications to its implementation in a .Net framework.

The nonstationary problem of the evolution of perturbation and its transformation into nonlinear wave structure in dusty plasmas is considered. For this purpose two one-dimensional models based on a set of fluid equations, Poisson’s equation, and a charging equation for dust are developed. The first (simplified) model corresponds to the case [Popel et al., Phys. Plasmas 3, 4313 (1996)] when exact steady-state shock wave solutions can exist. This simplified model includes variable-charged dust grains, Boltzmann electrons, and inertial ions. The second (ionization source) model takes into account the variation of the ion density and the ion momentum dissipation due to dust particle charging as well as the source of plasma particles due to ionization process. The computational method for solving the set of equations which describe the evolution in time of a nonlinear structure in a charge-varying dusty plasma is developed. The case of the evolution of an intensive initial nonmoving region with a constant enhanced ion density is investigated on the basis of these two models. The consideration within the ionization source model is performed for the data of the laboratory experiment [Luo et al., Phys. Plasmas 6, 3455 (1999)]. It is shown that the ionization source model allows one to obtain shock structures as a result of evolution of an initial perturbation and to explain the experimental value of the width of the shock wave front. Comparison of the numerical data obtained on the basis of the ionization source model and the simplified model shows that the main characteristic features of the shock structure are the same for both models. Nevertheless, the ionization source model is much more sensitive to the form of the initial perturbation than the simplified model. The solution of the problem of the evolution of perturbation and its transformation into shock wave in charge-varying dusty plasmas opens up possibilities for description of the real phenomena like supernova explosions as well as of the laboratory and active space and geophysical experiments.

Engineers are faced with two major challenges when carrying out the thermal-fluid design of a complex system consisting of many interacting components such as the PBMR power plant. The first challenge is to predict the performance of all the individual thermal-fluid components. The second challenge is to predict the performance of the integrated plant consisting of all its sub-systems. The complexity associated with the thermal-fluid design of complex systems requires the use of a variety of analysis techniques and simulation tools. These range from simple one-dimensional models that do not capture all the significant physical phenomena, to large-scale three-dimensional CFD codes that, for practical reasons, can not simulate the entire plant as a single integrated model. In the systems CFD approach a network code serves as the framework to link the models of the various components together and to control the solution. The models of the components can be of varying degrees of complexity. These can range from simple lumped models to complex fully three-dimensional CFD models. This paper gives a brief overview of the systems CFD (SCFD) approach and an overview of the SCFD model of the pebble bed nuclear reactor that was developed.

The collapse performance of steel frames generally depends on their ability to resist local damage. However, this ability is decided by the connection behavior, which has not been determined methodically and reliably. Thus, developing a simplified connection model for predicting the structural collapse resistance is critical for preventing progressive collapse. In this study, component models were constructed with different stiffness connections, including the double web angle (DWA), top-seat with double web angle (TSDWA), and welded flange-bolted web (WUF) connections, according to the component method by simplifying its geometry and dividing it into several basic springs. The proposed component-based connection models with detailed components were implemented within the finite element program, ANSYS. The models were validated against previous experimental tests. The analysis results indicate that the component models can accurately reflect the load response and post-fracture path of the assemblies with a cost-effective solution. This indicates that the component method is significant for progressive collapse analysis, providing a simple and effective tool for designers and engineers to evaluate the load-resisting capacities of steel frame structures.

Very good agreement is shown for diurnal and semidiurnal temperature variations calculated from lidar measurements in southern France and from data of the microwave limb sounder of the Upper Atmosphere Research Satellite (UARS). Tides induce temperature deviations observed in southern France to be as large as ±3 K, with a maximum at the stratopause. The amplitudes and phases of the semidiurnal variation change significantly with season and location. Seasonal changes up to 2 K have been clearly identified for the diurnal component. An analytic model of the diurnal component, based on sinusoidal functions, fits the data well, but is less successful for the semidiurnal component. Substantial agreement is also reported for the diurnal component between the results of our analytical model and the published results of a two‐dimensional global‐scale wave model. In contrast, the semidiurnal component is in total disagreement with numerical simulations that report very small amplitudes, as compared with the observations reported here. The confidence in detecting bias in data comparisons is improved if data used are limited to periods from April to September and if time‐of‐day adjustments are applied. Comparison between lidar and nearly coincident UARS temperature measurements have revealed, systematically, for the 4 experiments aboard UARS, a significant residual mean difference of up to 3 K around 35–43 km. A comparison using simultaneous measurements suggests that the bias is associated with the variability of migrating tides and/or the presence of nonmigrating tides rather than instrumental characteristics.

Beam-column joints play a critical role in the overall safety and load transfer mechanism of reinforced concrete frame structures, particularly under lateral and seismic loading conditions. Accurate assessment of joint behavior is essential for predicting structural performance and preventing progressive damage or collapse. Conventional experimental investigations provide reliable insights but are often limited by cost, time, and scalability constraints. In this context, simplified finite element modeling offers an efficient analytical alternative for evaluating joint response while retaining essential behavioral characteristics. This research presents an analytical investigation of beam-column joint behavior using a simplified finite element modeling approach aimed at balancing computational efficiency and predictive accuracy. The modeling framework incorporates key material nonlinearities, geometric compatibility, and boundary conditions relevant to typical reinforced concrete joints. Stress distribution, strain localization, stiffness degradation, and load-deformation response is examined under monotonic loading scenarios. The analytical results are compared with established theoretical expectations and trends reported in previous experimental and numerical studies to validate the modeling strategy. The findings indicate that simplified finite element models can effectively capture critical joint behaviors such as shear stress concentration, cracking initiation zones, and progressive stiffness reduction without resorting to highly complex constitutive formulations. The research highlights the sensitivity of joint response to mesh discretization, material idealization, and joint geometry representation. By demonstrating the feasibility of simplified modeling techniques, this work contributes to the development of practical analytical tools suitable for preliminary design evaluation, parametric studies, and academic research. The outcomes support the hypothesis that simplified finite element models, when appropriately calibrated, can serve as reliable indicators of beam-column joint performance, thereby reducing dependence on resource-intensive experimental programs while enhancing understanding of joint mechanics in reinforced concrete frame systems.

Experimental and theoretical results are given for studies of optical limiters designed to increase the functional range without incurring optical damage. In particular, we investigate a tandem geometry with two passive nonlinear elements, one placed in the focal plane of a lens and the second placed `upstream' of the focal position to protect the material at focus from damage. To provide a proof-of-principle demonstration of this geometry, simple limiters consisting of combinations of reverse saturable absorber dyes and a carbon black suspension in thin cells were tested. Our results show that a substantial increase in device performance can be achieved by use of a tandem limiter geometry. Simple modelling predicts that the dynamic range of a separate- element tandem limiter is given by the product of the dynamic ranges of the individual component limiting elements, in agreement with our experimental results. We also describe our numerical beam propagation code, which must be applied for thick limiting elements and in other cases where simple modelling is invalid.

Main goal of this paper is to propose a compact library of polymorphic gates based on suitable type of reconfigurable transistors. In fact, their exploitation brings a significant advantage for space-efficient synthesis of complex polymorphic circuits. Actual behaviour of those transistors closely depends on so called ambipolar property. That particular aspect simply allows the selection of n- or p- channel operating mode of the transistor structures which is controlled by means of switching the voltage level at a dedicated control electrode. The gates were developed by an evolution approach using Cartesian genetic programming. Various discrete switch-level ambipolar transistor models extended by taking into account the threshold voltage drop degradation effect were used. A diverse range of polymorphic gates were designed, which clearly shows significant transistor savings compared to the conventional approaches. Finally, the individual components that belong to the library also suggest the opportunity how to considerably reduce the target size of complex polymorphic circuits.

A recently developed parameter estimation-based steady state simulation model of water-to-water reciprocating vapor compression heat pumps (Jin H, Spitler JD, ASHRAE Trans. 2002; 108(1)) is built up from models of individual components. Various unspecified parameters for individual components are estimated from catalogue data for the overall unit performance. This approach has been shown to give better accuracy and extrapolation capability than polynomial fit models. It has also been shown to give accuracy similar to more detailed deterministic models that require additional information not typically available to an engineer performing energy analysis. This paper covers two important extensions to the model — scroll compressors and glycol/water mixtures. A five-parameter (including intake volumetric flow rate, built-in compression ratio, leakage coefficient and two efficiency-related parameters) scroll compressor model replaces the reciprocating compressor model previously used. While necessary in some applications for providing protection from freezing, water/glycol solutions adversely impact heat transfer performance. A procedure for adjusting the model parameters to account for the change in working fluids is presented. In addition, a preliminary field validation of the modified water-to-water heat pump model is presented. The heat pump utilized both a scroll compressor and a propylene glycol/water mixture as the working fluid.