scholarly journals Towards the suppression of blend chains using Euler operators and open geometric modeling kernel

2019 ◽  
Author(s):  
Сергей Сляднев ◽  
Sergey Slyadnev ◽  
Вадим Турлапов ◽  
Vadim Turlapov
Keyword(s):  
Geometric Modeling ◽  
Boundary Representation ◽  
Batch Mode ◽  
Topology Analysis ◽  
Adjacency Graph ◽  
Essential Properties ◽  
A Chain ◽  
Euler Operators ◽  
Two Stages ◽  
Local Topology

This paper presents a CAD model simplification procedure which consists of recognition and suppression of certain types of blend chains. The proposed method involves Euler operators KEV, KEF, and KFMV, which are developed on top of open-sourced geometric modeling kernel. The simplification process employs two stages: recognition and suppression. The suppression stage ensures the geometric and topological validity of the simplification result. The present approach is targeted for use in a batch mode, which poses strict requirements to the robustness of the suppression algorithm. The essential properties of the presented approach are its sustainability, the predictability of the result and the extensible architecture, which allows for adding new topological cases without affecting the algorithm’s core. At the recognition stage, the algorithm constructs an attributed adjacency graph, which is then enriched with such information as edges’ types, their properties, and the assumed kinds of blend faces. At the suppression stage, the algorithm iterates the adjacency graph and composes the blend candidate faces into the chains. For each face in a chain, a local topology analysis is performed to determine the corresponding sequence of Euler operators which are supposed to eliminate that face. The algorithm allows for extensions through adding descriptors of the new topology situations into the processing. After the Euler operators are done, the affected edges are reconstructed to obtain a watertight boundary representation of the model.

Design for Assembly Evaluation of Orientation Difficulty Features

1992 ◽  
Author(s):  
Robert H. Sturges ◽  
Jui-Te Yang
Keyword(s):  
Geometric Modeling ◽  
Boundary Representation ◽  
Design For Assembly ◽  
Assembly Process ◽  
Assembly Evaluation ◽  
Index Of Difficulty ◽  
Analysis System ◽  
Time Required ◽  
High Level ◽  
Geometric Modeling System

Abstract In support of the effort to bring downstream issues to the attention of the designer as parts take shape, an analysis system is being built to extract certain features relevant to the assembly process, such as the dimension, shape, and symmetry of an object. These features can be applied to a model during the downstream process to evaluate handling and assemblability. In this paper, we will focus on the acquisition phase of the assembly process and employ a Design for Assembly (DFA) evaluation to quantify factors in this process. The capabilities of a non-homogeneous, non-manifold boundary representation geometric modeling system are used with an Index of Difficulty (ID) that represents the dexterity and time required to assemble a product. A series of algorithms based on the high-level abstractions of loop and link are developed to extract features that are difficult to orient, which is one of the DFA criteria. Examples for testing the robustness of the algorithms are given. Problems related to nearly symmetric outlines are also discussed.

Geometrical and Topological Issues in NMT-Based Modeling

1992 ◽  
Author(s):  
Mukul Saxena ◽  
Rajan Srivatsan ◽  
Jonathan E. Davis
Keyword(s):  
Data Structure ◽  
Geometric Modeling ◽  
Modeling Environment ◽  
Insertion Algorithm ◽  
The Face ◽  
Euler Operators ◽  
Application Specific ◽  
Model Topology

Abstract The Non-Manifold Topology (NMT) Radial Edge data structure, along with the supporting set of Euler operators, provides a versatile environment for modeling non-manifold domains. The operators provide the basic tools to construct and manipulate model topology. However, an implementation of the base functionality in a geometric modeling environment raises some geometry-related issues that need to be addressed to ensure the topological validity of the underlying model. This paper focuses on those issues and emphasizes the use of geometry in the implementation of topological operators. Enhancements to the topology manipulation operations are also discussed. Specifically, this paper describes (i) a geometry-based algorithm for face insertion within the Radial Edge data structure, (ii) a manifestation of the face-insertion algorithm to resolve topological ambiguities that arise in the design of topological glue operators, and (iii) enhancements to the topology deletion operators to meet application-specific requirements.

Oxidative sulphitolysis of the disulphide groups in insulin and cystine

1962 ◽  
Vol 15 (2) ◽  
pp. 365 ◽  
Author(s):  
SJ Leach ◽  
JM Swan
Keyword(s):  
Metal Ions ◽  
Room Temperature ◽  
Air Oxidation ◽  
Large Excess ◽  
Reaction Proceeding ◽  
Disulphide Bonds ◽  
Combined Action ◽  
A Chain ◽  
Oxidative Sulphitolysis ◽  
Two Stages

All three disulphide bonds in insulin are broken by the combined action of sulphite and oxygen, the reaction proceeding at a reasonable rate at room temperature, pH 8-10. This " oxidative sulphitolysis " (RSSR'+RSSO< +RISSO<) is strongly catalysed by metal ions, particularly Cu(11). For a 1% solution of insulin at pH 10 containing 2x 10-4iu CU(II), reaction is complete in about 24 hr at 20 OC, and acidification then gives a precipitate of the S-sulpho B-chain, the S-sulpho A-chain remaining in solution. Catalysis of the air-oxidative sulphitolysis of cystine to S-sulphocysteine (Clarke 1932 ; Kolthoff and Stricks 1951a, 1951b) is confirmed, CU(II), M~(II), CO(IIL), and F~(III) being most effective in that order. In these reactions the binding of metal ions by intermediate thiols prevents or retards the usual metal-catalysed air oxidation of sulphite to sulphate, so that a large excess of sulphite is not required. When a mixture of insulin and sulphite is oxidized with CU(II) with exclusion of oxygen, two end-points are readily detected (cf. cystine ; Kolthoff and Stricks 1951a, 1951b), corresponding to the reactions In addition there is evidence for the formation, in the early stages, of cupric mercaptide according to the equation Cupric sulphitolysis can also be carried out in two stages by &st titrating the insulin with CU(I) to the end-point of the reaction and then with CU(II) to complete the reaction according to RSCU+SO;- +2Cu2++RSS0c +3Cu+.

Geometric Dimension and Tolerance Modeling and Validation System Based on Object Oriented Paradigm for 3D Solid Model

2004 ◽  
Author(s):  
Monir M. Koura ◽  
Ibrahiem M. Elewa ◽  
Rajit Gadh ◽  
Shiv Prabhu ◽  
Khaled A. Mohamed
Keyword(s):  
Geometric Dimension ◽  
Boundary Representation ◽  
Solid Model ◽  
Prototype System ◽  
Tolerance Modeling ◽  
3D Geometry ◽  
Engineering Models ◽  
Model Geometry ◽  
Two Stages ◽  
3D Solid

This paper introduces an approach for modeling and representation of geometric tolerances on any 3D solid model using the Objected Oriented Programming (OOP) paradigm. The modeling scheme is supported by a comprehensive validation engine, which certifies the tolerance type against the 3D geometry context both syntactically and semantically. The major objective of this work is to develop a methodology for interfacing tolerance modeling with boundary representation (B-Rep) based 3D solid model geometry. We will demonstrate that the OOP paradigm is very efficient and flexible for tolerance model representation, which is required within the interactive design process. Six categories of tolerance classes have been developed for size, form, orientation, position, runout and profile, which extend a general tolerance class through inheritance. An instance of the general tolerance class will be initialized when picking a feature or a group of features to tolerance, depending upon feature(s’) characteristics and attributes. To apply a tolerance object the system obtains the 3D geometric data from the solid model using the feature extraction paradigm. When the required tolerance type is selected for modeling, an instance from the specified tolerance type class will be initialized through inheritance from the general feature tolerance class and gathers the necessary information / tolerance data. An intelligent validation engine that supports the modeler is introduced. The engine validates any selected tolerancing activity in two stages. First, it ensures that the selected feature or group of features is suitable for the selected tolerance type. Second, it ensures that the data specified does not lead to over/under-dimensioning. The paper also discusses a prototype system implemented to test the modeler and the validation engine. The results have been very encouraging while testing the system on a number of engineering models.

Studies in polymerization - XXI. On free-radical formation by oxidation of molybdenum carbonyl with carbon tetrahalides: carbon tetrabromide

1972 ◽  
Vol 326 (1567) ◽  
pp. 453-468 ◽  
Keyword(s):  
Free Radical ◽  
Methyl Methacrylate ◽  
High Reactivity ◽  
High Rate ◽  
Free Radical Scavengers ◽  
Chain Process ◽  
Acetate Solution ◽  
Molybdenum Carbonyl ◽  
A Chain ◽  
Two Stages

Determination of the conversion as a function of reaction time in the polymerization of methyl methacrylate initiated by Mo(CO) 6 + CBr 4 a t 80 °C indicates that the rate constant for carbonyl consumption is the same as in the CCI 4 system and corresponds to displacement of a CO ligand by monomer; further, each Mo(CO) 6 consumed gives rise to three free radicals. The limiting initial rate of polymerization at high [CBr 4 ] is consistent with the rapid formation of three radicals per Mo(CO) 6 . It is concluded that primary and secondary oxidation steps occur as with CCI 4 , but that on account of the relatively high reactivity of CBr 4 the two stages occur effectively simultaneously and cannot readily be separated. Tracer investigations with 14 CBr 4 reveal that both stages yield CBr 3 radicals. The electron spin resonance (e. s. r.) spectra of the paramagnetic products formed in ethyl acetate solution at 80 °C are shown to arise from Mo v species. The signal intensity grows at a remarkably high rate, corresponding to a half-life of 0.25 h; the rate is markedly reduced by the presence of free radical scavengers such as methyl methacrylate or cyclohexane. These observations are thought to indicate the occurrence of a chain process involving CBr 3 and Mo I , which react with Mo(CO) 6 and CBr 4 , respectively. Experiments in which CBr 3 radicals were produced photochemically from Mn 2 (CO) 10 + CBr 4 in the presence of Mo(CO) 6 support the proposed mechanism. Although the carbonyls of chromium and tungsten, in association with halides, initiate polymerization, the products do not give observable e. s. r. spectra. It is suggested that these reactions lead to oxidation states III and VI respectively, rather than V, which is particularly stable in the case of molybdenum.

Thermal decomposition of barium perchlorate

1969 ◽  
Vol 47 (16) ◽  
pp. 3031-3039 ◽  
Author(s):  
R. J. Acheson ◽  
P. W. M. Jacobs
Keyword(s):  
Thermal Decomposition ◽  
Ambient Pressure ◽  
Barium Chloride ◽  
Reaction Sequence ◽  
Chain Reaction ◽  
Gaseous Products ◽  
A Chain ◽  
Two Stages ◽  
Linear Period ◽  
Barium Perchlorate

The thermal decomposition of anhydrous barium perchlorate to barium chloride and oxygen has been studied by pressure measurements, or by weight loss, in vacuo, under the accumulated gaseous products (0–3 Torr oxygen), under dry air or nitrogen, and mixed with added barium chloride. The plots of fractional decomposition (α) against time (t) are complex, as would be expected for a reaction proceeding via unstable intermediates. The most pronounced features of the α(t) curves are an initial acceleratory period, which is succeeded by an approximately linear period and then, after a sharp break (reduction in rate), by a deceleratory period which conforms to the contracting-volume kinetic law. The latter stage is associated with the decomposition of barium chlorate and has an activation energy of 59 kcal/mole. The first two stages comprise the decomposition of perchlorate to chlorate with the approximate stoichiometry 3ClO4− = 2ClO3− + Cl− + 3O2. A chain reaction sequence, which involves O atoms as chain carriers, is proposed for these stages. The effect of the removal of products, of increasing the ambient pressure of inert gas, and of the addition of barium chloride, can all be explained on this model.

Feature Recognition for Virtual Environments

2014 ◽  
Vol 610 ◽  
pp. 642-646
Author(s):  
Mong Heng Ear ◽  
Cheng Cheng ◽  
Salem Mostafa Hamdy ◽  
Alhazmi Marwah
Keyword(s):  
Virtual Environments ◽  
Data Exchange ◽  
Feature Recognition ◽  
Virtual Assembly ◽  
Recognition Algorithm ◽  
Boundary Representation ◽  
Adjacency Graph ◽  
Levels Of Detail ◽  
Data Source ◽  
Design Systems

This paper demonstrates methods to recognize 3D designed features for virtual environments and apply them to Virtual assembly. STEP is a standard of Product data Exchange for interfacing different design systems, but it cannot be used as input for virtual environments. In order to use feature data in virtual assembly environments, main data source from a STEP file should be recognized and features should be re-built. First, Attributed Adjacency Graph (AAG) is used to analyze and express the boundary representation; second, a feature-tree of a part is constructed; third, using the AAG and feature-tree as inputs, we analyze and extract of features with a feature recognition algorithm; finally, various levels of detail of object geometric shapes is built and expressed in XML for virtual assembly applications.

scholarly journals Performance characteristics of single-stage biohythane production by immobilized anaerobic bacteria

Energetika ◽  
2018 ◽  
Vol 64 (2) ◽  
Author(s):  
Doan Thanh Ta ◽  
Chiu Yue Lin ◽  
Chen Yeon Chu ◽  
Thi Minh Ngoc Ta
Keyword(s):  
Anaerobic Bacteria ◽  
Methanogenic Bacteria ◽  
Dark Fermentation ◽  
Single Stage ◽  
Economic Viability ◽  
Energy Yield ◽  
Batch Mode ◽  
Innovative Method ◽  
Stage System ◽  
Two Stages

Biohythane produced via dark fermentation is much greener than hythane that is generated using natural gas. Biohythane production using a single-stage system has potential to increase the economic viability since it requires fewer controls than a two-stage system that has individual acidogenic and methanogenic reactors. This single-stage system is an innovative method in producing biohythane. The present work investigated the performance of a mesophilic single-stage system with a batch mode operation to generate biohythane. The reactor was seeded with hydrogenic and methanogenic bacteria (HB and MB), which were entrapped in κ-carrageenan/ gelatin beads (2%/2% w/w) using the dripping method. The energy yield of 0.41 to 1.48 kJ g–1 glucose and the hydrogen content in biohythane (H2/(H2 + CH4)) of 0.35 to 0.69 were obtained. These results indicate that different biohythane compositions would be obtained by regulating the HB/MB bacteria concentration ratio, substrate concentration and cultivation pH. Moreover, a comparison of two-stages and single-stage systems as well as the challenges were also elucidated.

Body Modeling

1993 ◽  
Author(s):  
Norman I. Badler ◽  
Cary B. Phillips ◽  
Bonnie Lynn Webber
Keyword(s):  
Computer Graphics ◽  
Geometric Modeling ◽  
Boundary Representation ◽  
Skeletal Structure ◽  
Surface Model ◽  
Surface Patches ◽  
Volumetric Representation ◽  
Moving Points ◽  
Human Figure ◽  
3D Volume

In order to manipulate and animate a human figure with computer graphics, a suitable figure must be modeled. This entails constructing a satisfactory surface skin for the overall human body shape, defining a skeletal structure which admits proper joint motions, adding clothing to improve the verisimilitude of analyses (as well as providing an appropriate measure of modesty), sizing body dimensions according to some target individual or population, and providing visualization tools to show physically-relevant body attributes such as torque loads and strength. In computer graphics, the designer gets a wide choice of representations for the surfaces or volumes of objects. We will briefly review current geometric modeling schemes with an emphasis on their relevance to human figures. We classify geometric models into two broad categories: boundary schemes and volumetric schemes. In a boundary representation the surface of the object is approximated by or partitioned into (non-overlapping) 0-, 1-, or 2- dimensional primitives. We will examine in turn those representations relevant to human modeling: points and lines, polygons, and curved surface patches. In a volumetric representation the 3D volume of the object is decomposed into (possibly overlapping) primitive volumes. Under volumetric schemes we discuss voxels, constructive solid geometry, ellipsoids, cylinders, spheres, and potential functions. The simplest surface model is just a collection of 3D points or lines. Surfaces represented by points require a fairly dense distribution of points for accurate modeling. Clouds of points with depth shading were used until the early 1980’s for human models on vector graphics displays. They took advantage of the display’s speed and hierarchical transformations to produce the perceptual depth effect triggered by moving points [Joh76] (for example, [GM86]). A related technique to retain display speed while offering more shape information is to use parallel rings or strips of points. This technique is used in LifeForms™ [Lif91, Cal91]. Artistically positioned “sketch lines” were used in one of the earliest human figure models [Fet82] and subsequently in a Mick Jagger music video, “Hard Woman” from Digital Productions. Polygonal (polyhedral) models are one of the most commonly encountered representations in computer graphics.

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