Current CAD Tools Research Articles

Generating DNA Origami Nanostructures through Shape Annealing

Structural DNA nanotechnology involves the design and self-assembly of DNA-based nanostructures. As a field, it has progressed at an exponential rate over recent years. The demand for unique DNA origami nanostructures has driven the development of design tools, but current CAD tools for structural DNA nanotechnology are limited by requiring users to fully conceptualize a design for implementation. This article introduces a novel formal approach for routing the single-stranded scaffold DNA that defines the shape of DNA origami nanostructures. This approach for automated scaffold routing broadens the design space and generates complex multilayer DNA origami designs in an optimally driven way, based on a set of constraints and desired features. This technique computes unique designs of DNA origami assemblies by utilizing shape annealing, which is an integration of shape grammars and the simulated annealing algorithm. The results presented in this article illustrate the potential of the technique to code desired features into DNA nanostructures.

A comprehensive comparison between LE and LM-based methodologies for optimisation of digital circuits

This paper presents a comprehensive comparison between Levenberg-Marquardt (LM) and logical effort (LE) theory-based optimisation techniques. While LM is a classical approach for optimisation and is embedded in SPICE, logical effort-based approach is contemporary, design specific and needs simple back of the envelope calculations for optimisation of digital circuits. Both the approaches have been used by digital circuit designers in the literature for comparing a proposed digital circuit with the existing designs while optimising any given design for timing, power and area parameters. The goal of writing this paper is to make digital system designers gain an insight into the procedures used for optimising digital circuits while at the same time a well-defined approach using LM algorithm is provided that can be easily automated with the current generation CAD tools. For the purpose of comparison some standard circuits were chosen and optimised for minimum PDP and PDAP. SPICE simulations have been extensively used for comparing the two methodologies in a 180 nm\1.8 V CMOS technology.

Shape-It-Up: Hand gesture based creative expression of 3D shapes using intelligent generalized cylinders

We present a novel interaction system, “Shape-It-Up”, for creative expression of 3D shapes through the naturalistic integration of human hand gestures with a modeling scheme dubbed intelligent generalized cylinders (IGC). To achieve this naturalistic integration, we propose a novel paradigm of shape–gesture–context interplay (SGCI) wherein the interpretation of gestures in the spatial context of a 3D shape directly deduces the designer’s intent and the subsequent modeling operations. Our key contributions towards SGCI are threefold. Firstly, we introduce a novel representation (IGC) of generalized cylinders as a function of the spatial hand gestures (postures and motion) during the creation process. This representation allows for fast creation of shapes while retaining their aesthetic features like symmetry and smoothness. Secondly, we define the spatial contexts of IGCs as proximity functions of their representational components, namely cross-sections and the skeleton with respect to the hands. Finally, we define a natural association of modification and manipulation of the IGCs by combining the hand gestures with the spatial context. Using SGCI, we implement intuitive hand-driven shape modifications through skeletal bending, sectional deformation and sectional scaling schemes. The implemented prototype involves human skeletal tracking and hand posture classification using the depth data provided by a low-cost depth sensing camera (Kinect™). With Shape-It-Up, our goal is to make the designer an integral part of the shape modeling process during early design, in contrast to the case for current CAD tools which segregate 3D sweep geometries into procedural 2D inputs in a non-intuitive and onerous process requiring extensive training. We conclusively demonstrate the modeling of a wide variety of 3D shapes within a few seconds.

Mediating cognitive transformation with VR 3D sketching during conceptual architectural design process

Communications for information synchronization during the conceptual design phase require designers to employ more intuitive digital design tools. This paper presents findings of a feasibility study for using VR 3D sketching interface in order to replace current non-intuitive CAD tools. We used a sequential mixed method research methodology including a qualitative case study and a cognitive-based quantitative protocol analysis experiment. Foremost, the case study research was conducted in order to understand how novice designers make intuitive decisions. The case study documented the failure of conventional sketching methods in articulating complicated design ideas and shortcomings of current CAD tools in intuitive ideation. The case study’s findings then became the theoretical foundations for testing the feasibility of using VR 3D sketching interface during design. The latter phase of study evaluated the designers’ spatial cognition and collaboration at six different levels: physical-actions, perceptualactions, functional-actions, conceptual-actions, synchronizations, and gestures. The results and confirmed hypotheses showed that the utilized tangible 3D sketching interface improved novice designers’ cognitive and collaborative design activities. In summary this paper presents the influences of current external representation tools on designers’ cognition and collaboration as well as providing the necessary theoretical foundations for implementing VR 3D sketching interface. It contributes towards transforming conceptual architectural design phase from analogue to digital by proposing a new VR design interface. The paper proposes this transformation to fill in the existing gap between analogue conceptual architectural design process and remaining digital engineering parts of building design process hence expediting digital design process.

Comparison of CAD and manual sketching tools for teaching architectural design

Communications for information synchronisation during the conceptual design phase usually require designers to employ more flexible and intuitive digital design tools. In developing such support tools, a case study research was initiated to first understand the current state of communication among novice design team members. The main purpose of the study is to understand the novice designers' collaboration culture when working on conceptual architectural design projects. The overall case study research involves 1) ethnography for data collection and 2) artefact and protocol analyses for data analysis. This paper presents the latter data analyses based on the earlier ethnography results about novice designers' conceptual design and technology design synthesis strategies. Data analyses on the characteristics of utilised external representation tools indicate that although conventional manual sketching is beneficial for providing rich intuitive design concepts, they have limitations when novice designers need to oversee complicated design problems. The study also found that although current conventional CAD tools are advantageous for detailed engineering design articulation, they do hinder novice designers' creativity due to their intuitive ideation limitation. Based on these results, this paper discusses the identified advantages and challenges of current design media and then proposes an alternative VR-based design interface for enhancing cognition and communication among designers during the conceptual design phase.

Visual knowledge specification for conceptual design: Definition and tool support

Current CAD tools are not able to support the conceptual design phase, and none of them provides a consistency analysis for sketches produced by architects. This phase is fundamental and crucial for the whole design and construction process of a building. To give architects a better support, we developed a CAD tool for conceptual design and a knowledge specification tool. The knowledge is specific to one class of buildings and it can be reused. Based on a dynamic and domain-specific knowledge ontology, different types of design rules formalize this knowledge in a graph-based form. An expressive visual language provides a user-friendly, human readable representation. Finally, a consistency analysis tool enables conceptual designs to be checked against this formal conceptual knowledge. In this article, we concentrate on the knowledge specification part. For that, we introduce the concepts and usage of a novel visual language and describe its semantics. To demonstrate the usability of our approach, two graph-based visual tools for knowledge specification and conceptual design are explained.

Triangle mesh compression and simplification

Triangular meshes are widely used in computer graphics fields, such as GIS, CAD and VR. Very complex models, with hundreds of thousands of faces, are easily produced by current CAD tools, automatic...

Phased logic: supporting the synchronous design paradigm with delay-insensitive circuitry

Phased logic is proposed as a solution to the increasing problem of timing complexity in digital design. It is a delay-insensitive design methodology that seeks to restore the separation between logical and physical design by eliminating the need to distribute low-skew clock signals and carefully balance propagation delays. However, unlike other methodologies that avoid clocks, phased logic supports the cyclic, deterministic behavior of the synchronous design paradigm. This permits the designer to rely chiefly on current experience and CAD tools to create phased logic systems. Marked graph theory is used as a framework for governing the interaction of phased logic gates that operate directly on Level-Encoded two-phase Dual-Rail (LEDR) signals. A synthesis algorithm is developed for converting clocked systems to phased logic systems and is applied to benchmark examples. Performance results indicate that phased logic tends to be tolerant of logic delay imbalances and has predictable worst-case timing behavior. Although phased logic requires additional circuitry, it has the potential to shorten the design cycle by reducing timing complexities.