36 research outputs found
Firing circuit for converters used in drives applications
No full textThe purpose of this paper is designing, simulating and fabricating a triggering circuit for converters used in DC drives applications. The working of the proposed triggering circuit is discussed. Detailed description and functioning of various stages in the design is highlighted along with the output waveforms. The proposed design is first simulated using Multisim and the simulation results are presented. The objectives of this design incorporate the precise control of firing angle, provision for feed-back control for motor control applications and achieving pulse of designed nature. The designed system is then fabricated and the hardware results are summarized.</p
“Cellular-Cut”-Interactive n-Dimensional Image Segmentation Using Cellular Automata
No full text Interactive segmentation of images has become an integral part of image processing applications. Several graph based segmentation techniques have been developed, which depend upon global minimization of the energy cost function. An adequate scheme of interactive segmentation still needs a skilled initialization of regions with user-defined seeds pixels distributed over the entire image. We propose an iterative segmentation technique based on Cellular Automaton which focuses to reduce the user efforts required to provide initialization. The existing algorithms based on Cellular Automaton only use local smoothness term in label propagation making them highly sensitive to user-defined seeds pixels. To reduce the sensitivity towards initial user definition of regions, global constraints are introduced along with local information to propagate labels. The results obtained are comparable to the state-of-the-art interactive segmentation techniques on a standard dataset. </jats:p
The Brick Screen : parametric approach to traditional Pakistani jali within the digital divide
No full textWith concerns regarding climate and need for more sustainable practices, practitioners try to appropriate advance design tools for their efficient problem-solving capabilities. In regions like Pakistan, architects are met with challenges of the digital divide due to which they must improvise and develop hybrid methodologies, bridging the gaps between digital tools and analogue construction techniques. While it imposes a limit on the selection of tools, it leads to new opportunities to embed performative qualities and novel tectonics in region specific material systems.
In this paper, authors explain the process and challenges behind a recent large scale parametric brick façade titled the Brick Screen in Karachi, Pakistan designed and fabricated for the ACPKHI (Arts Council of Pakistan Karachi) in 2022. Challenges consisted of local perceptions of risk, cost, skeptical attitudes regarding technology, and lack of existing examples of parametric design within the region. By using parametric design tools in a contextually grounded manner and optimization for manual fabrication, the architects were able to reintroduce the idea of the traditional jali (hence the name Brick Screen based on the Urdu word jali - جالی ) which existed as an ornamental, climatically efficient device in the region interfacing with sunlight, natural ventilation, and privacy. Parametric design tools such as Grasshopper (a parametric design plugin for Rhino3D) helped develop not only brick patterns based on sunlight, spatial functions, and ornamentation, but a secondary script helped translate and optimize the generated patterns into human-readable fabrication drawings. This allowed linking of digital design process with existing construction practices that architects and stakeholders were familiar with. Constraints of manual brick masonry led to abstraction of thousands of bricks into simple sequences (or chal - چال as understood in colloquial construction terms), resulting in an efficient, economically feasible assembly process on site.
The project sets a precedent in the region for working at extremes of the digital divide and digital tools as means to transform existing practices. By using materials and building systems which are already accessible, digital tools can embed additional performative qualities in brick in a contemporary and regionally sensitive manner without the cost barriers of advanced materials or fabrication systems. Without access to advanced fabrication platforms ideal for transforming local practices at a fundamental level, architects can still work within limitations of technology, practice, and industry to achieve solutions that are more appropriate for the future
A Global Sampling Based Image Matting Using Non-Negative Matrix Factorization
No full textImage matting is a technique in which a foreground is separated from the background of a given image
along with the pixel wise opacity. This foreground can then be seamlessly composited in a different
background to obtain a novel scene. This paper presents a global non-parametric sampling algorithm
over image patches and utilizes a dimension reduction technique known as NMF (Non-Negative Matrix
Factorization). Although some existing non-parametric approaches use large nearby foreground and
background regions to sample patches but these approaches fail to take the whole image to sample
patches. It is because of the high memory and computational requirements. The use of NMF in the
proposed algorithm allows the dimension reduction which reduces the computational cost and memory
requirement. The use of NMF also allow the proposed approach to use the whole foreground and
background region in the image and reduces the patch complexity and help in efficient patch sampling.
The use of patches not only allows the incorporation of the pixel colour but also the local image structure.
The use of local structures in the image is important to estimate a high-quality alpha matte especially
in the images which have regions containing high texture. The proposed algorithm is evaluated on the
standard data set and obtained results are comparable to the state-of-the-art matting technique
Tuning COCOMO-II for Software Process Improvement: A Tool Based Approach
No full textIn order to compete in the international software development market the software organizations have
to adopt internationally accepted software practices i.e. standard like ISO (International Standard
Organization) or CMMI (Capability Maturity Model Integration) in spite of having scarce resources
and tools. The aim of this study is to develop a tool which could be used to present an actual picture of
Software Process Improvement benefits in front of the software development companies. However,
there are few tools available to assist in making predictions, they are too expensive and could not cover
dataset that reflect the cultural behavior of organizations for software development in developing
countries. In extension to our previously done research reported elsewhere for Pakistani software
development organizations which has quantified benefits of SDPI (Software Development Process
Improvement), this research has used sixty-two datasets from three different software development
organizations against the set of metrics used in COCOMO-II (Constructive Cost Model 2000). It
derived a verifiable equation for calculating ISF (Ideal Scale Factor) and tuned the COCOMO-II model
to bring prediction capability for SDPI (benefit measurement classes) such as ESCP (Effort, Schedule,
Cost, and Productivity). This research has contributed towards software industry by giving a reliable and low-cost mechanism for generating prediction models with high prediction accuracy. Hopefully,
this study will help software organizations to use this tool not only to predict ESCP but also to predict an exact impact of SDPI
