ICE: incremental 3-dimensional capacitance and resistance extraction for an iterative design environment

We present a divide-and-conquer algorithm to improve the three-dimensional (3-D) boundary element method (BEM) for capacitance extraction. We divide large interconnect structures into small sections, set new boundary conditions using the border for each section, solve each section, and then combine the results to derive the capacitance. The target application is critical nets, clock trees, or packages where 3-D accuracy is required. Our algorithm is a significant improvement over the traditional BEMs and their enhancements, such as the "window" method, where conductors far away are dropped, and the "shield" method where conductors hidden behind other conductors are dropped. Experimental results show that our algorithm is a magnitude faster than the traditional BEM and the window+shield method, for medium to large structures. The error of the capacitance computed by the new algorithm is within 2% for self capacitance and 7% for coupling capacitance, compared with the results obtained by solving the entire system using BEM. Furthermore, our algorithms gives accurate distributed RC, where none of the previous 3-D BEM algorithms and their enhancements can.

Very fast and accurate 3-D capacitance extraction is essential for ultra deep sub-micron design (UDSM) of integrated circuits. Parallel processing provides an approach to reducing the simulation turn-around time. In this paper, we present two parallel formulations for 3-D capacitance extraction, based on the fast multipole method (FMM) and the direct boundary element method (BEM), respectively. We report detailed comparison results on parallel efficiency and memory scalability, on three different distributed memory platforms, including a 16 processor IBM SP2, and ATM network of 16 HP workstations, and an Ethernet network of 16 HP workstations.

BEM for wave interaction with structures and low storage accelerated methods for large scale computation

This paper describes an efficient improvement of the multipole accelerated boundary element method for 3-D capacitance extraction. The overall relations between the positions of 2-D boundary elements are considered instead of only the relations between the center-points of the elements, and a new method of cube partitioning is introduced. Numerical results are presented to demonstrate that the method is accurate and has nearly linear computational growth as O(n), where n is the number of panels/boundary elements. The proposed method is more accurate and much faster than Fastcap.

The three‐dimensional simulation of fatigue crack growth under the consideration of 3D effects is presented to follow complex crack paths as realistic as possible from the macroscopic point of view. This aim is mainly based on two aspects. Firstly, an accurate stress analysis is performed by the boundary element method in terms of the 3D Dual BEM. Secondly, a suitable 3D crack growth criterion based on experimental observations is utilized. Due to the non‐linearity of crack growth the whole procedure is embedded in an advanced incremental crack growth algorithm. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The most expensive operation in explicit state model checking is the hash computation required to store the explored states in a hash table. One way to reduce this computation is to compute the hash incrementally by only processing those portions of the state that are modified in a transition. This paper presents an incremental heap canonicalization algorithm that aids in such an incremental hash computation. Like existing heap canonicalization algorithms, the incremental algorithm reduces the state space explored by detecting heap symmetries. On the other hand, the algorithm ensures that for small changes in the heap the resulting canonical representations differ only by relatively small amounts. This reduces the amount of hash computation a model checker has to perform after every transition, resulting in significant speedup of state space exploration. This paper describes the algorithm and its implementation in two explicit state model checkers, CMC and Zing.

A method using successive iteration of analysis and design for large-scale topology optimization considering eigenfrequencies

New Product Positioning in an Evolving Technology Environment

This report summarizes the final product developed for the US DOE Small Business Innovation Research (SBIR) Phase II grant made to Engineering Mechanics Corporation of Columbus (Emc2) between April 16, 2014 and August 31, 2016 titled ‘Adoption of High Performance Computational (HPC) Modeling Software for Widespread Use in the Manufacture of Welded Structures’. Many US companies have moved fabrication and production facilities off shore because of cheaper labor costs. A key aspect in bringing these jobs back to the US is the use of technology to render US-made fabrications more cost-efficient overall with higher quality. One significant advantage that has emerged in the US over the last two decades is the use of virtual design for fabrication of small and large structures in weld fabrication industries. Industries that use virtual design and analysis tools have reduced material part size, developed environmentally-friendly fabrication processes, improved product quality and performance, and reduced manufacturing costs. Indeed, Caterpillar Inc. (CAT), one of the partners in this effort, continues to have a large fabrication presence in the US because of the use of weld fabrication modeling to optimize fabrications by controlling weld residual stresses and distortions and improving fatigue, corrosion, and fracture performance. This report describes Emc2’s DOE SBIR Phase II final results to extend an existing, state-of-the-art software code, Virtual Fabrication Technology (VFT®), currently used to design and model large welded structures prior to fabrication - to a broader range of products with widespread applications for small and medium-sized enterprises (SMEs). VFT® helps control distortion, can minimize and/or control residual stresses, control welding microstructure, and pre-determine welding parameters such as weld-sequencing, pre-bending, thermal-tensioning, etc. VFT® uses material properties, consumable properties, etc. as inputs. Through VFT®, manufacturing companies can avoid costly design changes after fabrication. This leads to the concept of joint design/fabrication where these important disciplines are intimately linked to minimize fabrication costs. Finally service performance (such as fatigue, corrosion, and fracture/damage) can be improved using this product. Emc2’s DOE SBIR Phase II effort successfully adapted VFT® to perform efficiently in an HPC environment independent of commercial software on a platform to permit easy and cost effective access to the code. This provides the key for SMEs to access this sophisticated and proven methodology that is quick, accurate, cost effective and available “on-demand” to address weld-simulation and fabrication problems prior to manufacture. In addition, other organizations, such as Government agencies and large companies, may have a need for spot use of such a tool. The open source code, WARP3D, a high performance finite element code used in fracture and damage assessment of structures, was significantly modified so computational weld problems can be solved efficiently on multiple processors and threads with VFT®. The thermal solver for VFT®, based on a series of closed form solution approximations, was extensively enhanced for solution on multiple processors greatly increasing overall speed. In addition, the graphical user interface (GUI) was re-written to permit SMEs access to an HPC environment at the Ohio Super Computer Center (OSC) to integrate these solutions with WARP3D. The GUI is used to define all weld pass descriptions, number of passes, material properties, consumable properties, weld speed, etc. for the structure to be modeled. The GUI was enhanced to make it more user-friendly so that non-experts can perform weld modeling. Finally, an extensive outreach program to market this capability to fabrication companies was performed. This access will permit SMEs to perform weld modeling to improve their competitiveness at a reasonable cost.

<div class="section abstract"><div class="htmlview paragraph">The aim of this paper is to optimize flow distribution on various ports of the ventilation unit. To improve the passenger comfort, ventilation unit need to be redesigned to get the uniform distribution in all ducts. There were challenges for the design modification on the unit to meet the distribution. The major challenge was to meet the distribution on the duct outlet without doing any design changes on the ducts. Hence the adapter which is the intermediate part between the blower and duct assembly is modified and simulation is done on the various design changes by changing the design of the adaptor part. CFD analysis is carried out on the ventilation unit with iterative design changes and achieved the target airflow and distribution. The analysis has been carried out on STAR CCM+ software.</div></div>

Due to the advantages on scalability and reliability, the floating random walk (FRW) algorithm has been widely adopted for calculating the capacitances among three-dimensional (3-D) conductors. This is evidenced by the industrial practice of interconnect capacitance extraction during the design of high-performance very large-scale integrated (VLSI) circuits. In this work, the FRW algorithm is enhanced through the distributed parallel computing. With an efficient and adaptive task allocation scheme, the communication among different computer nodes is largely reduced. A distributed algorithm for accelerating the space management is also proposed. They have been implemented with Message Passing Interface (MPI) and applied to the high-precision capacitance simulation for touchscreen design and the interconnect capacitance extraction of VLSI circuits. Experiments on a computer cluster show that the proposed techniques achieve up to 114X speedup while using 120 cores, and build up the space management structure for a VLSI case including two million conductor blocks in just 22 seconds (37X parallel speedup on 60 cores).

Acceleration of the capacitance extraction of planar structures on a single‐layered medium is reported in this article, using the forward‐backward (FB) method with a spectral acceleration (SA) algorithm. The conventional spectral‐layered medium Green's function is modified appropriately so that it can be effectively incorporated into this method. The SA algorithm substantially speeds up the computational time involving in performing matrix‐vector multiplications in the iterative method of moments (MM). However, the memory requirement for the SA algorithm is comparable to that of the FB method. The computational complexity and the memory requirement are shown to be O(N) for large capacitance extraction problems, where N is the total number of unknowns in the MM for increasing one of the surface dimensions of planar structures and fixed neighborhood distance. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:694–700, 2014

Wave Energy Converters (WECs) are expected to significantly contribute to the energy transition; however, this depends on their interactions with the resource. Calculating the power generated by WECs depends heavily on the accurate modelling of wave-structure interactions. The Boundary Element Method (BEM) based on the potential flow theory has yielded accurate results at low computational costs when compared to complex Computational Fluid Dynamics (CFD) methods. Hydrodynamic Analysis of Marine Structures (HAMS), a recently developed open-source BEM frequency domain solver, originally was created for large marine structures. To date it has only been applied to single WECs with spherical/cylindrical geometries. HAMS offers unique advantages through its efficient removal of irregular frequencies and lower computational costs. This paper aims to compare hydrodynamic coefficients, exciting forces, Response Amplitude Operators (RAOs) and computational costs between HAMS, WAMIT, and NEMOH for a cylindrical point absorber and an oscillating surge WEC, extending the currently limited WECs application in HAMS.

The boundary element method is established as a powerful technique for the stress analysis needed in shape design optimization. Two alternative algorithms for determining the optimum are available, using either sensitivity derivatives or normal movement of the boundary on the basis of local stresses. These algorithms are investigated in relation to the problem of shape optimization of fillets in plates under tension. The results are compared with others published previously, and it is concluded that, particularly for problems such as fillets, where the feasible region for design changes is restricted by practical considerations, the normal movement approach is preferable, and avoids the need to calculate large numbers of sensitivity derivatives.

This paper presents a procedure for estimating small changes in maximum-likelihood estimates of gravitv model parameters in response to small changes in base period data. The procedure can be used to derive covariance matrices for such parameter estimates from which confidence intervals may be obtained and which may be used for tests of hypotheses. Also the procedure extends a similar procedure for estimating sensitivities, etc., of gravity model forecasts. While this type of problem has been addressed by others, our approach is the only one that is applicable for the large numbers of origin and destination zones one typically encounters.