Computer-aided Design Tools Research Articles

Interactive Programming for Parametric CAD

AbstractParametric computer‐aided design (CAD) enables description of a family of objects, wherein each valid combination of parameter values results in a different final form. Although Graphical User Interface (GUI)‐based CAD tools are significantly more popular, GUI operations do not carry a semantic description, and are therefore brittle with respect to changes in parameter values. Programmatic interfaces, on the other hand, are more robust due to an exact specification of how the operations are applied. However, programming is unintuitive and has a steep learning curve. In this work, we link the interactivity of GUI with the robustness of programming. Inspired by programme synthesis by example, our technique synthesizes code representative of selections made by users in a GUI interface. Through experiments, we demonstrate that our technique can synthesize relevant and robust sub‐programmes in a reasonable amount of time. A user study reveals that our interface offers significant improvements over a programming‐only interface.

Homology modeling of human GABA-AT and devise some novel and potent inhibitors via computer-aided drug design techniques

γ-aminobutyric acid aminotransferase (GABA-AT) is a pyridoxal 5′-phosphate (PLP)-dependent enzyme which degrades γ-aminobutyric (GABA) in the brain. GABA is an important inhibitory neurotransmitter that plays important neurological roles in the brain. Therefore, GABA-AT is an important drug target which regulates the GABA level. Novel and potent drug development to inhibit GABA-AT is still very challenging task. In this study, we aimed to devise novel and potent inhibitors against GABA-AT using computer-aided drug design (CADD) tools. However, the human GABA-AT crystal structure is not available yet, and we built the 3D structure of human GABA-AT based on the crystal structure of pig’s liver (Sus Scrofa) enzyme as a template. The generated model was validated with numerous tools such as ProSA and PROCHECK. A set of selected well-known inhibitors have been tested against the modeled GABA-AT. Molecular docking studies have been accomplished via application of Genetic Optimization for Ligand Docking (GOLD), Vina and Autodock 4.2 software to search for potent inhibitors. The best two candidate inhibitors have been computationally examined for absorption, distribution, metabolism, elimination and toxicity descriptors (ADMET) and Lipinski’s rule of 5. Lastly, molecular dynamics (MD) simulations were carried out to inspect the ligands’ binding mode and stability of the active site of human GABA-AT over time. The top ranked ligands exhibited reliable stability throughout the MD simulation. The selected compounds are promising candidates and might be tested experimentally for the inhibition of human GABA-AT enzyme. Communicated by Ramaswamy H. Sarma

Finite element analysis of narrow dental implants

Narrow-diameter implants (NDIs) traditionally have been associated to higher rates of failure in comparison with regular-diameter implants (RDIs) and wide-diameter implants (WDIs), since they generate a more unfavorable stress distribution in peri-implant bone. However, it is well known that the load sharing effect associated with prostheses supported by multiple implants (also called splinted prostheses) affords mechanical benefits. The present study involves finite element analysis (FEA) to determine whether the risks linked to NDIs could be mitigated by the mechanical advantages afforded by the splinting concept. For this purpose, a three-dimensional (3D) model of a real maxilla was reconstructed from computed tomography (CT) images, and different implants (NDIs, RDIs and WDIs) and prostheses were created using computer-aided design (CAD) tools. Biting forces were simulated on the prostheses corresponding to three different rehabilitation solutions: single-implant restoration, three-unit bridge and all-on-four treatment. Stress distribution around the implants was calculated, and overloading in bone was quantified within peri-implant volumes enclosed by cylinders with a diameter 0.1mm greater than that of each implant. The mechanical benefits of the splinting concept were confirmed: the peri-implant overloaded volume around NDIs splinted by means of the three-unit bridge was significantly reduced in comparison with the nonsplinted condition and, most importantly, proved even smaller than that around nonsplinted implants with a larger diameter (RDIs). However, splinted NDIs supporting the all-on-four prosthesis led to the highest risk of overloading found in the study, due to the increase in compressive stress generated around the tilted implant when loading the cantilevered molar.

Energy-driven design space exploration of tiling-based accelerators for heterogeneous multiprocessor architectures

Programming heterogeneous multiprocessor architectures combining multiple processor cores and hardware accelerators is a real challenge. Computer-aided design and development tools try to reduce the large design space by simplifying hardware-software mapping mechanisms. However, energy consumption is not well supported in most of design space exploration methodologies due to the difficulty to estimate energy consumption fast and accurately. To this aim, this paper proposes and validates an exploration method for partitioning tilling-based parallel applications on software cores and hardware accelerators under energy-efficiency constraints. The methodology is based on energy and performance measurement of a tiny subset of the design space and an analytical formulation of the performance and energy of an application kernel mapped onto a heterogeneous architecture. This closed-form expression is captured and solved using Mixed Integer Linear Programming, which allows for very fast exploration and results in the best hardware and software partitioning under energy constraint. The approach is validated on two application kernels using a Zynq-based architecture showing more than 12% acceleration speed-up and energy saving compared to standard approaches. Results also show that the most energy-efficient solution is application- and platform-dependent and moreover hardly predictable, which highlights the need for fast exploration tools as in this paper.

Structural, daylighting, and energy performance of perforated concrete shell structures

In this work, a computational interdisciplinary design approach is used to integrate assessment of the structural and environmental performance of perforated concrete shell structures. Design parameters that co-exist in these disciplines and relevant performance criteria are identified. Questions result: how do these design parameters affect performance? What is the tradeoff between performance in each? Computer-aided design tools are used for form generation and performance assessment. Statistical analyses are used to study the sensitivity of performance to each parameter. Finally, the perforation ratio is found to be the most significant parameter affecting both disciplines; a value ≤ 10% to 20% is recommended for shell structures when translucent glazing is installed without shades in a Boston-type climate.

A proposal for a computational design and ecology based approach to architectural design studio

Using computational design methods, this study aims to analyze the effects of an integrated design process model on the ecological awareness of architectural students, and on their ability to incorporate ecological issues in their design work. To this end, two studies have been carried out. The first one involves a survey about how ecology-related and computational design courses complement the architectural design studio at different universities in Turkey. The second one, which is the main study of this paper, presents the results of an ecology-based computational design workshop. According to the results of the first study, computer-based design courses in Turkey usually lack the dimension of “computational thinking”, focusing only on computer-aided design tools. Moreover, we have also found out that ecology courses in Turkish architectural education are mostly elective, and hence, have only very indirect connection to the architectural design studio. In the second study, we have demonstrated how incorporating computational thinking into the design process increase students’ awareness of the ecological dimension and their ability to make this dimension an integral part of their projects. The paper concludes by elaborating on the importance of computational methods in architectural education.

Computational design synthesis of additive manufactured multi-flow nozzles

Additive manufacturing (AM) enables highly complex-shaped and functionally optimized parts. To leverage this potential the creation of part designs is necessary. However, as today’s computer-aided design (CAD) tools are still based on low-level, geometric primitives, the modeling of complex geometries requires many repetitive, manual steps. As a consequence, the need for an automated design approach is emphasized and regarded as a key enabler to quickly create different concepts, allow iterative design changes, and customize parts at reduced effort. Topology optimization exists as a computational design approach but usually demands a manual interpretation and redesign of a CAD model and may not be applicable to problems such as the design of parts with multiple integrated flows. This work presents a computational design synthesis framework to automate the design of complex-shaped multi-flow nozzles. The framework provides AM users a toolbox with design elements, which are used as building blocks to generate finished 3D part geometries. The elements are organized in a hierarchical architecture and implemented using object-oriented programming. As the layout of the elements is defined with a visual interface, the process is accessible to non-experts. As a proof of concept, the framework is applied to successfully generate a variety of customized AM nozzles that are tested using co-extrusion of clay. Finally, the work discusses the framework’s benefits and limitations, the impact on product development and novel AM applications, and the transferability to other domains.

COVID-19: CADD to the rescue

The recent outbreak of the deadly COVID-19 disease, being caused by the novel coronavirus (SARS-CoV-2), has put the world on red alert as it keeps spreading and recording more fatalities. Research efforts are being carried out to curtail the disease from spreading as it has been declared as of global health emergency. Hence, there is an exigent need to identify and design drugs that are capable of curing the infection and hinder its continual spread across the globe. Herein, a computer-aided drug design tool known as the virtual screening method was used to screen a database of 44 million compounds to find compounds that have the potential to inhibit the surface glycoprotein responsible for virus entry and binding. The consensus scoring approach selected three compounds with promising physicochemical properties and favorable molecular interactions with the target protein. These selected compounds can undergo lead optimization to be further developed as drugs that can be used in treating the COVID-19 disease.

Automatic Generation of Object Shapes With Desired Affordances Using Voxelgrid Representation.

3D objects (artifacts) are made to fulfill functions. Designing an object often starts with defining a list of functionalities or affordances (action possibilities) that it should provide, known as functional requirements. Today, designing 3D object models is still a slow and difficult activity, with few Computer-Aided Design (CAD) tools capable to explore the design solution space. The purpose of this study is to explore shape generation conditioned on desired affordances. We introduce an algorithm for generating voxelgrid object shapes which afford the desired functionalities. We follow the principle form follows function, and assume that object forms are related to affordances they provide (their functions). First, we use an artificial neural network to learn a function-to-form mapping from a dataset of affordance-labeled objects. Then, we combine forms providing one or more desired affordances, generating an object shape expected to provide all of them. Finally, we verify in simulation whether the generated object indeed possesses the desired affordances, by defining and executing affordance tests on it. Examples are provided using the affordances contain-ability, sit-ability, and support-ability.

SCRIPT

Power side-channel attacks (SCAs) have been proven to be effective at extracting secret keys from hardware implementations of cryptographic algorithms. Ideally, the power side-channel leakage (PSCL) of hardware designs of a cryptographic algorithm should be evaluated as early as the pre-silicon stage (e.g., gate level). However, there has been little effort in developing computer-aided design (CAD) tools to accomplish this. In this article, we propose an automated CAD framework called SCRIPT to evaluate information leakage through side-channel analysis. SCRIPT starts by defining the underlying properties of the hardware implementation that can be exploited by side-channel attacks. It then utilizes information flow tracking (IFT) to identify registers that exhibit those properties and, therefore, leak information through the side-channel. Here, we develop an IFT-based side-channel vulnerability metric ( SCV ) that is utilized by SCRIPT for PSCL assessment. SCV is conceptually similar to the traditionally used signal-to-noise ratio (SNR) metric. However, unlike SNR, which requires thousands of traces from silicon measurements, SCRIPT utilizes formal methods to generate SCV-guided patterns/plaintexts, allowing us to derive SCV using only a few patterns (ideally as low as two) at gate level. SCV estimates PSCL vulnerability at pre-silicon stage based on the number of plaintexts required to attain a specific SCA success rate. The integration of IFT and pattern generation makes SCRIPT efficient, accurate, and generic to be applied to any hardware design. We validate the efficacy of the SCRIPT framework by demonstrating that it can effectively and accurately determine SCA success rates for different AES designs at pre-silicon stage. SCRIPT is orders of magnitude more efficient than traditional pre-silicon PSCL assessment (SNR-based), with an average evaluation time of 15 minutes; whereas, traditional PSCL assessment at pre-silicon stage would require more than a month. We also analyze the PSCL characteristic of the multiplication unit of RISC processor using SCRIPT to demonstrate SCRIPT’s applicability.

Quantitative structure-activity relationship (QSAR) and design of novel ligands that demonstrate high potency and target selectivity as protein tyrosine phosphatase 1B (PTP 1B) inhibitors as an effective strategy used to model anti-diabetic agents

Diabetes and obesity have increased dramatically in recent decades worldwide. Diabetes mainly emerged as a major health care burden disease in both the US and other industrialized countries, among which type II diabetes is the most common. Discovering new and effective treatments for diabetes is currently a high international health priority. In the present study a computational technique was used to model 97 compounds with PTP-1B inhibitory activity, in order to demonstrate the Quantitative structure-activity relationship (QSAR) of these compounds a genetic function approximation (GFA) algorithm was applied to pick the best descriptors and multiple linear regression (MLR) was used to establish a relationship between the PTP-1B inhibitory activity of these compounds and the best molecular descriptors. This QSAR study allowed investigating the influence of very simple and easy-to-compute descriptors in determining biological activities, which shed light on the key factors that aid in the design of novel potent molecules using computer-aided drug design tools.

Three-Dimensional (3D) Model-Based Lower Limb Stump Automatic Orientation

Modern prosthetics largely relies upon visual data processing and implementation technologies such as 3D scanning, mathematical modeling, computer-aided design (CAD) tools, and 3D-printing during all stages from design to fabrication. Despite the intensive advancement of these technologies, once the prosthetic socket model is obtained by 3D scanning, its appropriate orientation and positioning remain largely the responsibility of an expert requiring substantial manual effort. In this paper, an automated orientation algorithm based on the adjustment of the 3D-model virtual anatomical axis of the tibia along with the vertical axis of the rectangular coordinates in three-dimensional space is proposed. The suggested algorithm is implemented, tested for performance and experimentally validated by explicit comparisons against an expert assessment.

Tool Setup Improvement for Package Scratch Mitigation at End-of-Line Process

With new and continuous semiconductor technology trends, challenges in assembly manufacturing are inevitable. This paper focused on the elimination of assembly defects particularly package chip-out and scratch at the singulation end-of-line (EOL) process of a semiconductor device. Simulation using computer-aided design (CAD) tools, actual process replication, and validations were done, eventually verifying and replicating the desired defect signatures. Singulation tool setup of the package was improved and a standardized tool setup was established based on the simulation and actual validations, resulting to at least 90% improvement in assembly EOL process parts per million (ppm) reduction.

Electron transport analysis of 4H-SiC with full-band Monte Carlo simulation including real-space Coulomb interactions

4H-SiC has been widely used in many applications. All of these benefit from its extremely high critical electric field with good electron mobility. 4H-SiC possesses a critical field ten times higher than that of Si, which allows high-voltage blocking layers composed of 4H-SiC to be approximately a tenth the thickness of a comparable Si device, thus reducing the device on-resistance and power losses, while maintaining the same high blocking capability. Unfortunately, commercial Technology for Computer-Aided Design tools like Sentaurus and Silvaco Atlas are based on effective mass approximation, while most 4H-SiC devices are not operated under a low electric field so the parabolic-like band approximation does not hold anymore. Hence, to get more accurate and reliable simulation results, full-band analysis is needed. The first step in the development of a full-band device simulator is the calculation of the band structure. In this work, the empirical pseudopotential method is adopted. The next task in the sequence is the calculation of the scattering rates. Acoustic, non-polar optical phonon, polar optical phonon, and Coulomb scattering are considered. Coulomb scattering is treated in real space using the particle–particle–particle–mesh approach. The third task is coupling the bulk full-band solver with a 3D Poisson equation solver to generate a full-band device simulator. For proof-of-concept of the methodology adopted here and for simplicity, a 3D resistor is simulated. From the resistor simulations, the low-field electron mobility dependence upon Coulomb scattering in 4H-SiC devices is extracted. The simulated low-field mobility results are in excellent agreement with available experimental data.

Impact of Interface Trap Charges on Analog/RF and Linearity Performances of Dual-Material Gate-Oxide-Stack Double-Gate TFET

This paper investigates the impact of different interface trap charges (ITCs) on dual-material gate-oxide-stack double-gate TFET (DMGOSDG-TFET) by introducing localized charges (donor/acceptor) at the interface of semiconductor/insulator. For this, we have observed the effects of different ITCs on both conventional dual material control gate tunnel field effect transistor (DMCG-TFET) and dual-material gate-oxidestack double-gate TFET with identical dimensions in terms of DC, analog/RF and linearity performance parameters. Both the devices with positive (donor) and negative (acceptor) ITCs, have been simulated using technology computer-aided design (TCAD) tool. To understand the impact of different ITCs on the DC and analog/RF performances, the parameters such as electric field, transfer characteristics, transconductance, parasitic capacitance, fT, GBP and TFP for DMGOSDG-TFET have been analyzed and compared with that of DMCG-TFET. Further, to analyze the effect of different ITCs on the linearity performances, the parameters VIP2, VIP3, IIP3 and IMD3 have been investigated and compared with that of the conventional DMCG-TFET. Simulation results demonstrate that DMGOSDG-TFET is more immune towards different types of ITCs as compared to the conventional DMCG-TFET. Hence, DMGOSDG-TFET is more reliable over the conventional device for ultra low power applications.

TCAD Simulation Study of Single-, Double-, and Triple-Material Gate Engineered Trigate FinFETs

A detailed comparative performance analysis of the Trigate Fin Field Effect Transistor (FinFET) device with different structures such as Single-Material Gate (SMG) FinFET, Double-Material Gate (DMG) FinFET, and Triple-Material Gate (TMG) FinFET has been done. Silvaco Atlas Technology Computer-Aided Design (TCAD) tool is used to model the Trigate FinFET device structures and to characterize all the electrical parameters of the device. The simulation results confirm that TMG FinFET device structure shows better performance than SMG and DMG FinFET device structures, in terms of device electrical parameters such as surface potential, electric field, and drain current. Moreover, TMG FinFET device structure exhibits an excellent transconductance of 0.28 μA/V when compared with SMG FinFET (0.21 μA/V) and DMG FinFET (0.24 μA/V).

Influence of Milling Tool and Prosthetic Materials on Roughness of the Dental CAD CAM Prostheses in End Milling Mode

Dental prostheses are machined by computer-aided design and manufacturing (CAD/CAM) tools. The integrity of the surface obtained, which must be suitable to meet expected clinical requirements is influenced by the milling parameters programmed. The integrity of the occlusal prosthesis surface obtained by the end milling mode, that is milling with a diamond rotary cutting tip, plays a major role in the clinical requirements desired. This study aims to investigate the impact of the tool-biomaterial couple in the CAD/CAM end milling mode on surface integrity (through roughness). Two CAD/CAM tools and four CAD/CAM biomaterials, both combined to four feed rates are tested. The surface roughness (Ra, Rt, Rz, Sa, Sq, and Sz) is observed for each couple. Finally, pairwise comparisons (Kruskal-Wallis test) of tool-biomaterial couples are performed. The results indicate that all the machined surfaces reveal isotropic surface topology. The roughness depends on the hardness of the biomaterial and not on the feed rate. The statistical tests reveal a significant difference in roughness depending on the tool used. To conclude, when milling the functional occlusal shape, biomaterial hardness and the tool used are key factors for achieving a given roughness consistent with clinical requirements.

Cloud-Based CAD Parametrization for Design Space Exploration and Design Optimization in Numerical Simulations

In this manuscript, an automated framework dedicated to design space exploration and design optimization studies is presented. The framework integrates a set of numerical simulation, computer-aided design, numerical optimization, and data analytics tools using scripting capabilities. The tools used are open-source and freeware, and can be deployed on any platform. The main feature of the proposed methodology is the use of a cloud-based parametrical computer-aided design application, which allows the user to change any parametric variable defined in the solid model. We demonstrate the capabilities and flexibility of the framework using computational fluid dynamics applications; however, the same workflow can be used with any numerical simulation tool (e.g., a structural solver or a spread-sheet) that is able to interact via a command-line interface or using scripting languages. We conduct design space exploration and design optimization studies using quantitative and qualitative metrics, and, to reduce the high computing times and computational resources intrinsic to these kinds of studies, concurrent simulations and surrogate-based optimization are used.

Remote Control of a Robotic Unit: A Case Study for Control Engineering Formation

Hands-on experimentation has widely demonstrated its efficacy in engineering training, especially in control formation, since experimentation using computer-aided control system design (CACSD) tools is essential for future engineers. In this context, this article describes a case study for Control Engineering formation, based on a new lab practice for the linear and angular velocity control for a commercial P3-DX robot platform, to teach industrial control. This lab proposal includes all the stages involved in the design of a real control system, from plant identification from an open-loop test to real experimentation of the designed control system. The lab practices proposed have a twofold objective: First, it is an interdisciplinary approach that allows students to put into practice the skills from other subjects in the curriculum, facilitating the integration of knowledge. In addition, it allows increasing the motivation of the students by working with a complex and realistic plant. The proposal has been evaluated through the grades of the students, as well as the perception of both students and instructors, and the results obtained allow to confirm the benefits of the proposal.

Techno-Economic and Environmental Evaluations of Decarbonized Fossil-Intensive Industrial Processes by Reactive Absorption & Adsorption CO2 Capture Systems

Decarbonization of energy-intensive systems (e.g., heat and power generation, iron, and steel production, petrochemical processes, cement production, etc.) is an important task for the development of a low carbon economy. In this respect, carbon capture technologies will play an important role in the decarbonization of fossil-based industrial processes. The most significant techno-economic and environmental performance indicators of various fossil-based industrial applications decarbonized by two reactive gas-liquid (chemical scrubbing) and gas-solid CO2 capture systems are calculated, compared, and discussed in the present work. As decarbonization technologies, the gas-liquid chemical absorption and more innovative calcium looping systems were employed. The integrated assessment uses various elements, e.g., conceptual design of decarbonized plants, computer-aided tools for process design and integration, evaluation of main plant performance indexes based on industrial and simulation results, etc. The overall decarbonization rate for various assessed applications (e.g., power generation, steel, and cement production, chemicals) was set to 90% in line with the current state of the art in the field. Similar non-carbon capture plants are also assessed to quantify the various penalties imposed by decarbonization (e.g., increasing energy consumption, reducing efficiency, economic impact, etc.). The integrated evaluations exhibit that the integration of decarbonization technologies (especially chemical looping systems) into key energy-intensive industrial processes have significant advantages for cutting the carbon footprint (60–90% specific CO2 emission reduction), improving the energy conversion yields and reducing CO2 capture penalties.