The article discusses a study which examined how an efficient population protocol exhibits similar dynamic features to a well-characterized biological switch. Topics include the various computing algorithms that have ...
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The article discusses a study which examined how an efficient population protocol exhibits similar dynamic features to a well-characterized biological switch. Topics include the various computing algorithms that have been designed to perform similar all-or-none decisions with high efficiency, what biologists can learn by looking at specific features of computational algorithms, and how and why complex signalling networks have evolved.
Purpose: Lung cancer screening with low-dose CT has recently been approved for reimbursement, heralding the arrival of such screening services worldwide. computer-aided detection (CAD) tools offer the potential to ass...
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Purpose: Lung cancer screening with low-dose CT has recently been approved for reimbursement, heralding the arrival of such screening services worldwide. computer-aided detection (CAD) tools offer the potential to assist radiologists in detecting nodules in these screening exams. In lung screening, as in all CT exams, there is interest in further reducing radiation dose. However, the effects of continued dose reduction on CAD performance are not fully understood. In this work, we investigated the effect of reducing radiation dose on CAD lung nodule detection performance in a screening population. Methods: The raw projection data files were collected from 481 patients who underwent low-dose screening CT exams at our institution as part of the National Lung Screening Trial (NLST). All scans were performed on a multidetector scanner (Sensation 64, Siemens Healthcare, Forchheim Germany) according to the NLST protocol, which called for a fixed tube current scan of 25 effective mAs for standard-sized patients and 40 effective mAs for larger patients. The raw projection data were input to a reduced-dose simulation software to create simulated reduced-dose scans corresponding to 50% and 25% of the original protocols. All raw data files were reconstructed at the scanner with 1 mm slice thickness and B50 kernel. The lungs were segmented semi-automatically, and all images and segmentations were input to an in-house CAD algorithm trained on higher dose scans (75-300 mAs). CAD findings were compared to a reference standard generated by an experienced reader. Nodule- and patient-level sensitivities were calculated along with false positives per scan, all of which were evaluated in terms of the relative change with respect to dose. Nodules were subdivided based on size and solidity into categories analogous to the LungRADS assessment categories, and sub-analyses were performed. Results: From the 481 patients in this study, 82 had at least one nodule (prevalence of 17%) and 399 did
The development of two computer algorithms to assess the performance of IDMT over-current protection for interconnected power systems is described. The first algorithm considers the case of three-phase short-circuit f...
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The development of two computer algorithms to assess the performance of IDMT over-current protection for interconnected power systems is described. The first algorithm considers the case of three-phase short-circuit faults, and the second considers single-phase to earth shortcircuit faults. Both can include multiple bulk supply points, parallel lines and transformers, directional and nondirectional relays, including both on the same circuit, teed points, and instantaneous high-set elements. The algorithms currently incorporate relays with a standard inverse characteristic but any relay with a current/time characteristic can easily be included. Results are presented of the application of these algorithms to the assessment of the relay performance for several actual power distribution systems. For each selected fault position, the operating time of each relay is calculated and the sequence of relay operation shown until the fault is completely isolated. The results also illustrate, in particular, the ways in which the performance of the relay systems can be tabulated to greatest effect.
The article presents a speech by computer scientist Leslie Lamport, a computer scientist and the 2013 recipient of the Association for Computing Machinery's (ACM's) A.M. Turing Award, entitled 'The Compute...
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The article presents a speech by computer scientist Leslie Lamport, a computer scientist and the 2013 recipient of the Association for Computing Machinery's (ACM's) A.M. Turing Award, entitled 'The computer Science of Concurrency: The Early Years'. It discusses the history of concurrent algorithms in the 1960s and 1970s. Topics discussed include mutual exclusion, producer-consumer synchronization, and distributed algorithms.
The present work is dedicated to explain the development of a computational model for simulating the grain structure formed in a squared billet produced by continuous casting. During steel solidification, three differ...
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The present work is dedicated to explain the development of a computational model for simulating the grain structure formed in a squared billet produced by continuous casting. During steel solidification, three different grain structures are formed as a function of the heat removal conditions. The solidification times previously calculated using a finite difference method were used as input data in order to simulate dynamically the evolution of the grain formation. Computational routines for grouping, counting and classifying have been programmed to evidence the influence of the solidification speed on the grain morphology resulted. Criterions based on solidification speed and time on mushy are used to establish the transitions zones between chill, columnar and equiaxed grains. Routines to simulate grain nucleation and growth based on chaos theory have been included to create a graphical cellular automaton on the computer screen to animate the grain structure formation.
The computer aided collimation gamma camera is aimed at breaking down the resolution sensitivity trade-off of the conventional parallel hole collimator. It uses larger and longer holes, having an added linear movement...
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The computer aided collimation gamma camera is aimed at breaking down the resolution sensitivity trade-off of the conventional parallel hole collimator. It uses larger and longer holes, having an added linear movement at the acquisition sequence. A dedicated algolithm including shift and sum, deconvolution. parabolic filtering and rotation is described. Examples of reconstruction are given. This work shows that a simple and fast algorithm, based on a diagonal dominant approximation of the problem carl be derived. Its gives a practical solution to the CACAO reconstruction problem.
A new computer algorithm for the reliable calculation of an ill-conditioned van der Mend matrix (VDMM) is presented where the determinant of the VDMM is found by calculation of its miners. Two numerical examples illus...
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A new computer algorithm for the reliable calculation of an ill-conditioned van der Mend matrix (VDMM) is presented where the determinant of the VDMM is found by calculation of its miners. Two numerical examples illustrate the method's application. One, where the determinant of a third-order equation is analyzed, gives a simple illustration of the technique. The second, where the order of the equation analyzed is raised to 40, shows the advantages of the proposed method compared to the standard one. (C) 1997 Elsevier Science Limited.
This paper presents a prototype Stereolithography (STL) file format slicing and tool-path generation algorithm, which serves as a data front-end for a Rapid Prototyping (RP) entry-level three-dimensional (3-D) printer...
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This paper presents a prototype Stereolithography (STL) file format slicing and tool-path generation algorithm, which serves as a data front-end for a Rapid Prototyping (RP) entry-level three-dimensional (3-D) printer. Used mainly in Additive Manufacturing (AM), 3-D printers are devices that apply plastic, ceramic, and metal, layer by layer, in all three dimensions on a flat surface (X, Y, and Z axis). 3-D printers, unfortunately, cannot print an object without a special algorithm that is required to create the computer Numerical Control (CNC) instructions for printing. An STL algorithm therefore forms a critical component for Layered Manufacturing (LM), also referred to as RP. The purpose of this study was to develop an algorithm that is capable of processing and slicing an STL file or multiple files, resulting in a tool-path, and finally compiling a CNC file for an entry-level 3D printer. The prototype algorithm was implemented for an entry-level 3-D printer that utilises the Fused Deposition Modelling (FDM) process or Solid Freeform Fabrication (SFF) process;an AM technology. Following an experimental method, the full data flow path for the prototype algorithm was developed, starting with STL data files, and then processing the STL data file into a G-code file format by slicing the model and creating a tool-path. This layering method is used by most 3-D printers to turn a 2-D object into a 3-D object. The STL algorithm developed in this study presents innovative opportunities for LM, since it allows engineers and architects to transform their ideas easily into a solid model in a fast, simple, and cheap way. This is accomplished by allowing STL models to be sliced rapidly, effectively, and without error, and finally to be processed and prepared into a G-code print file.
An efficient computer implementation of an originally developed spectral representation of multiple-valued input binary functions is presented. In such a representation, the spectrum for each multiple-valued input bin...
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An efficient computer implementation of an originally developed spectral representation of multiple-valued input binary functions is presented. In such a representation, the spectrum for each multiple-valued input binary function is composed of a vector of Walsh transforms, each of them defined for one pair of input variables of the function. By that approach, the number of spectral coefficients describing a given multiple-valued input binary function is a minimal one. The implementation of the algorithm allows for the calculation of the spectra of binary functions having an arbitrary number of literals;each of them can have up to 32 different logical values. The algorithm is interactive so users can manually determine the generation of a partial or whole spectrum.
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