Circuit Reliability Simulation

1995 ◽  
Vol 391 ◽  
Author(s):  
Chenming Hu

AbstractIn designing a complex circuit, designers make a large number of circuit simulations, design changes and optimizations and can predict the circuit's performance reasonably accurately before committing it to silicon. It would be unthinkable to bypass detailed circuit simulation and optimization and rely on simple design rules and the testing of finished IC's to discover errors or to find out if the performance of the circuit meet specifications. Yet, this is basically the way IC reliability is treated today. A logical alternative is to predict circuit reliability at the circuit design stage through reliability simulation.Reliability simulator BERT is used to illustrate the physical models and approaches used to simulate the hot electron effect, oxide time-dependent breakdown, electromigration, bipolar transistor gain degradation, and radiation effects. The goal is to make circuit reliability simulation a part of the IC design process.

Actuators ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 64
Author(s):  
Liankang Wei ◽  
Hongzhan Lv ◽  
Kehang Yang ◽  
Weiguang Ma ◽  
Junzheng Wang ◽  
...  

Purpose: We aim to provide a systematic methodology for the optimal design of MRD for improved damping capacity and dynamical adjustability in performing its damping function. Methods: A modified Bingham model is employed to model and simulate the MRD considering the MR fluid’s compressibility. The parameters that describe the structure of MRD and the property of the fluid are systematically examined for their contributions to the damping capacity and dynamically adjustability. A response surface method is employed to optimize the damping force and dynamically adjustable coefficient for a more practical setting related to the parameters. Results: The simulation system effectively shows the hysteretic characteristics of MRDs and shows our common sense understanding that the damping gap width and yoke diameter have significant effects on the damping characteristics of MRD. By taking a typical MRD device setup, optimal design shows an increase of the damping force by 33% and an increase of the dynamically adjustable coefficient by 17%. It is also shown that the methodology is applicable to other types of MDR devices. Conclusion: The compressibility of MR fluid is one of the main reasons for the hysteretic characteristics of MRD. The proposed simulation and optimization methods can effectively improve the MRD’s damping performance in the design stage.


2021 ◽  
pp. 2002053
Author(s):  
Yuhui Dong ◽  
Leimeng Xu ◽  
Yongli Zhao ◽  
Shalong Wang ◽  
Jizhong Song ◽  
...  

1962 ◽  
Vol 17 (6) ◽  
pp. 970-974 ◽  
Author(s):  
Hajimu Kawamura ◽  
Masakazu Fukai ◽  
Yoshikazu Hayashi

1972 ◽  
Vol 186 (1) ◽  
pp. 391-399
Author(s):  
M. A. Salter ◽  
B. Downs ◽  
G. R. Wray

A case study is made on the tack driving assembly of a boot and shoe lasting machine, and relates to the impact noise occurring during part of the machine cycle. Much of the noise is radiated due to vibrations at several frequencies of the tack driver lifting lever, which is excited by the direct application of impacts during the tack driving process. An experimental approach in applying noise reduction principles to various components of the assembly has been preferred to a more complex theoretical treatment, since the identification of the mechanism of impact noise generation and its subsequent abatement is directly relevant to most machine designers faced with the possibility of impact noise problems in other types of machinery. Small design changes, based on the knowledge gained from the experimental investigations, have resulted in noise reductions from 10 to 14 dB being achieved.


Author(s):  
Jin Wang ◽  
Donghui Zhang ◽  
Wenjun Hu ◽  
Lixia Ren

A fast reactor is one of recommended candidates of Generation IV nuclear energy systems, which would meet wide requirements such as sustainability, safety and economics for nuclear energy development. To be the China’s first fast reactor, China Experimental Fast Reactor (CEFR) typical technical options are following: 65 MW thermal power and 20 MW electric power, three circuits of sodium-sodium-water, integrated pool type structure for the primary circuit. To establish modular simulation system for sodium fast reactor, the code which simulated the thermal-hydraulic behavior of primary circuit was developed. The physical models include reactor core, reactor vessel cooling channel, pumps, protection vessel, intermediate heat exchangers, ionization chamber cooling channel, cold sodium pool, hot sodium pool, inlet plenum, and pipes, etc. The code could compute coolant pressures, flow rates, and temperatures in the primary circuit. This module was designed for analysis of a wide range of transients. Although based on CEFR, it can treat an arbitrary arrangement of components.


Author(s):  
Stefan Goetz ◽  
Benjamin Schleich ◽  
Sandro Wartzack

Associated with manufacturing and assembly processes, inevitable geometric deviations have a decisive influence on the function and quality of products. Therefore, their consideration and management are important tasks in product development. Moreover, to meet the demand for short development times, the front-loading of design processes is indispensable. This requires early tolerance analyses evaluating the effect of deviations in a design stage, where the product’s geometry has not yet been finally defined. Since such an early tolerance consideration allows quick and economic design changes seeking for robust designs, it is advisable that the design engineer, who is entirely familiar with the design, should take this step. For this purpose, this paper presents an easy-to-use CAD-based tolerance analysis method for skeleton models. The relevant part deviations are represented by varying geometric dimensions with externally driven family tables. The approach comprises the strength of vector-based methods but does not require an expensive set-up of tolerance analysis models. Particularly, the novelty of this method lies in the CAD-internal sampling-based tolerance analysis of simple geometries without the use of expensive CAT software. This enables designers to evaluate the effect of tolerances already at the preliminary design stage. Using a case study, the presented approach is compared with the conventional vector-based tolerance analysis.


2020 ◽  
Vol 24 (5) ◽  
pp. 2483-2503
Author(s):  
Onno Bokhove ◽  
Tiffany Hicks ◽  
Wout Zweers ◽  
Thomas Kent

Abstract. Government and consulting experts on flood mitigation generally face difficulties when trying to explain the science of extreme flooding to the general public, in particular the concept of a return period. Too often, for example, people perceive they are safe for the next 100 years after a 1:100-year return-period flood has hit their town. UK flood practitioners therefore gave us the challenge to design an outreach tool that conceptualises the science of flooding in a way that is accessible to and directly engages the public, and in particular demonstrates what a return period is. Furthermore, we were tasked with designing a live 3-D physical model rather than a graphical or animated 2-D game on a screen. We show here how we tackled that challenge by designing, constructing, and showcasing the Wetropolis Flood Demonstrator. Wetropolis is a transportable and conceptual physical model with random rainfall, river flow, a flood plain, an upland reservoir, a porous moor, representing the upper catchment and visualising groundwater flow, and a city which can flood following extreme and random rainfall. A key novelty is the supply of rainfall every Wetropolis day. Several aspects of Wetropolis are considered. i. We present the modular mathematical and numerical design on which Wetropolis is based. It guided the choice of parameter values of Wetropolis, which was loosely inspired by the Leeds Boxing Day floods of the River Aire in 2015. The design model further serves as the building block and inspiration for adaptations suited to particular local demands. Moreover, the model is purposely lean and therefore quick to compute, serving flexibility in the outreach-tool design, but is less suitable for any detailed scientific validation.ii. The constructed Wetropolis is described here in broad terms, but we include a link to a GitHub site with details to inspire other bespoke designs. The goal, again, is to facilitate new adaptations of Wetropolis for particular catchments different to the Leeds River Aire case.iii. Our experience in showcasing Wetropolis is summarised and discussed, with the purpose of giving an overview as well as inspiring improved and bespoke adaptations. While Wetropolis should be experienced live, with videos found on the GitHub site, here we provide a photographic overview. To date, Wetropolis has been showcased to 500 to 1000 people at public workshops and exhibitions on recent UK floods, as well as to flood practitioners and scientists at various research and stakeholder workshops.iv. We conclude with some ongoing design changes, including how people can experience natural flood management in a revised Wetropolis design. Finally, we also discuss how Wetropolis, although originally focussed solely on outreach, led to a new cost-effectiveness analysis and protocol for assessing flood-mitigation plans and inspired other physical models for use in education and water management.


1999 ◽  
Vol 103 (1026) ◽  
pp. 383-388 ◽  
Author(s):  
K. Gantois ◽  
A. J. Morris

Abstract The Paper describes a metal and composite recurrent cost model of a large civil aircraft wing structure for a multidisciplinary design, analysis and optimisation (MDO) environment. The work was part of a recent European MDO project (BE95-2056) which investigated methods for the integration of structures, aerodynamics, dynamics and manufacturing cost at the preliminary design stage. The paper discusses the cost modelling approach, which is based on parametric and process cost model methods, and the integration of the cost models into an MDO process. Results for the cost models are shown. A framework has been successfully developed which allows the incorporation of manufacturing cost models into an MDO environment. It allows a designer to evaluate cost changes with respect to specific design changes such as rib pitch, stringer pitch, wing area and wing sweep.


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