A New Method of Dimensional Synthesis for Planar 4-Bar Path Generation With Prescribed Timing

1998 ◽  
Author(s):  
Wu Xin ◽  
Chu Jinkui ◽  
Wu Chen ◽  
Cao Weiqing
Keyword(s):  
Rotation Angle ◽  
New Method ◽  
Path Generation ◽  
Dimensional Synthesis ◽  
Angle Function ◽  
Mathematical Equations ◽  
Harmonic Components ◽  
Set Up ◽  
Path Synthesis ◽  
First Time

Abstract Mathematical equations for 4-bar path generation on an arbitrarily arranged mechanism are set up by using complex number and Fourier series theory in this paper. The harmonic components of path generation on the coupler are carried out by systematic study. According to the conception of Coupler Rotation-Angle Operator (in short CRAO) about coupler’s rotation-angle function, a new method of determining the position for a coupler point, real dimensions and installing dimensions of the linkage is established for the first time. Based on this thinking, the concrete steps of dimension synthesis for path generation with prescribed timing are formed, and the method of path synthesis by using harmonic characteristic parameters is developed and further prefect is made.

Fourier series method for path generation of RCCC mechanism

2011 ◽  
Vol 226 (3) ◽  
pp. 816-827 ◽  
Author(s):  
J W Sun ◽  
D Q Mu ◽  
J K Chu
Keyword(s):  
Fourier Series ◽  
Frequency Domain ◽  
Synthesis Problem ◽  
Mathematical Representation ◽  
Path Generation ◽  
Series Method ◽  
Internal Relation ◽  
Fourier Series Method ◽  
Mathematical Equations ◽  
Path Synthesis

The mathematical representation of the coupler curves of RCCC mechanism is established. The coupler curve of RCCC mechanism is analysed using the Fourier series theory. The internal relation between the coupler curve and the dimensional type of the RCCC mechanism in the frequency domain is discovered. Subsequently, a database comprising millions of basic dimensional types, taking the crank–rocker linkages as an example, is established. Based on the information of prescribed coupler and the database, the best suitable basic dimensional type can be determined by identification. The mathematical equations for calculating actual dimensions of mechanism and positional dimensions of installation are deduced. Thus, the path synthesis problem of RCCC mechanism can be solved by the mathematic equations and the basic dimensional type. The calculation illustration is given later in this article.

Study on Dimension Synthesis of Planar 4-Bar Linkages for Rigid-Body Guidance With Prescribed Timing

1998 ◽  
Author(s):  
Wu Xin ◽  
Chu Jinkui ◽  
Cao Weiqing
Keyword(s):  
Rigid Body ◽  
Rotation Angle ◽  
Computer Method ◽  
Dimensional Synthesis ◽  
Fuzzy Identification ◽  
Real Dimension ◽  
The Real ◽  
Point Position ◽  
Angle Function ◽  
The Relationship

Abstract A computer method is firstly proposed, which is used to do the dimension synthesis of planar 4-bar linkages for rigid-body guidance with Prescribed Timing (in short PT) by harmonic component’s database of the coupler’s rotation-angle function. The relationship between position function of rigid-body guidance with PT and coupler’s rotation-angle function of 4-bar linkage is analyzed. The key of the method is to solve the real dimension of linkage, coupler’s point position and installing dimensions of the linkage. Considering solving the problem, a harmonic component’s database of the coupler’s rotation-angle function including 20350 dimensional types, taking the crank-rocker linkage as an example, is established. So, it is possible to choose some linkages from the database to realize rigid-body guidance with PT by using fuzzy identification method quickly, and to approximately achieve “infinite positions” of dimensional synthesis for rigid-body guidance. An example is given to illustrate the efficiency and advantage of this method.

Synthesis of a Spatial RRSS Mechanism for Path Generation Using the Numerical Atlas Method

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Wenrui Liu ◽  
Jianwei Sun ◽  
Jinkui Chu
Keyword(s):  
Rotation Angle ◽  
Synthesis Method ◽  
Path Generation ◽  
Feature Parameters ◽  
Atlas Method ◽  
Path Synthesis ◽  
The Mathematical Model ◽  
The Relationship ◽  
Generation Problem ◽  
Actual Size

Abstract An open path synthesis method for a spatial revolute-revolute-spherical-spherical (RRSS) mechanism is presented in this paper. The mathematical model for the trajectory curve is established. The characteristics of an RRSS mechanism in a standard installation position are revealed: the projection points of the coupler curve on the Oxy plane rotate by the corresponding input angles around the z-axis, and the generated points lie on an ellipse. Based on this finding, a 17-dimensional path generation problem can be translated into two lower-dimensional matching recognition problems and one actual size and installation position calculation problem. The path generation can be achieved by three steps. First, a database of four dimensional rotation angle parameters is established. By comparing the similarities between the mechanism feature curve of the prescribed open curve and its corresponding mechanism feature ellipse (MFE), the angles of installation, the initial angle of the input link, and the elliptic feature parameters of the desired RRSS mechanism can be approximately determined. Then, a 13-dimensional dynamic self-adapting numerical atlas database is established, which contains six basic dimensional types (BDTs) and seven wavelet feature parameters, and the BDTs of the desired RRSS mechanism are obtained. Finally, based on the relationship between the MFE of the prescribed curve and the BDTs of the desired RRSS mechanism, the calculation models for the actual link lengths and installation positions of the desired RRSS mechanism were established. Three examples are presented in this paper.

Research on Dimension Synthesis of Straight-Lines Mechanism for Rigid-Body Guidance by Using Numerical Atlas Method

2012 ◽  
Vol 271-272 ◽  
pp. 1397-1401
Author(s):  
Jian Wei Sun ◽  
He Lu ◽  
Xin Wu ◽  
Miao Guo
Keyword(s):  
Rigid Body ◽  
Rotation Angle ◽  
Angle Function ◽  
Atlas Method ◽  
Set Up ◽  
Straight Lines ◽  
Rotation Function ◽  
Angle Of Rotation

In this paper, the relation between angle of rotation function of the five-bar and similar four-bar mechanisms’ rigid-body and Coupler Rotation-Angle function is discussed. The principles of reduce the numerical atlas are proposed. A numerical atlas database comprising 240498 basic dimensional types is set up. Make the five-bar and similar four-bar mechanism for Rigid-Body Guidance with prescribed timing possible. Finally, an example is given to prove it.

Cobalt/Lewis Acid Catalysis for Hydrocarbofunctionalization of Alkynes via Cooperative C–H Activation

2020 ◽  
Author(s):  
Chang-Sheng Wang ◽  
Sabrina Monaco ◽  
Anh Ngoc Thai ◽  
Md. Shafiqur Rahman ◽  
Chen Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Lewis Acid ◽  
Hydrogen Transfer ◽  
Acid Catalysis ◽  
Rate Limiting Step ◽  
Site Selectivity ◽  
Set Up ◽  
Site Selective ◽  
First Time ◽  
Rate Limiting

A catalytic system comprised of a cobalt-diphosphine complex and a Lewis acid (LA) such as AlMe3 has been found to promote hydrocarbofunctionalization reactions of alkynes with Lewis basic and electron-deficient substrates such as formamides, pyridones, pyridines, and azole derivatives through site-selective C-H activation. Compared with known Ni/LA catalytic system for analogous transformations, the present catalytic system not only feature convenient set up using inexpensive and bench-stable precatalyst and ligand such as Co(acac)3 and 1,3-bis(diphenylphosphino)propane (dppp), but also display distinct site-selectivity toward C-H activation of pyridone and pyridine derivatives. In particular, a completely C4-selective alkenylation of pyridine has been achieved for the first time. Mechanistic stidies including DFT calculations on the Co/Al-catalyzed addition of formamide to alkyne have suggested that the reaction involves cleavage of the carbamoyl C-H bond as the rate-limiting step, which proceeds through a ligand-to-ligand hydrogen transfer (LLHT) mechanism leading to an alkyl(carbamoyl)cobalt intermediate.

scholarly journals Stay at Home! Governance Quality and Effectiveness of Lockdown

2021 ◽  
Author(s):  
Vincenzo Alfano ◽  
Salvatore Ercolano
Keyword(s):  
Rule Of Law ◽  
Global Scale ◽  
Considerable Time ◽  
Government Effectiveness ◽  
Governance Indicators ◽  
Regulatory Quality ◽  
Governance Quality ◽  
World Governance Indicators ◽  
Set Up ◽  
First Time

AbstractIn order to control the spread of the COVID-19 pandemic, during the first wave of the pandemic numerous countries decided to adopt lockdown policies. It had been a considerable time since such measures were last introduced, and the first time that they were implemented on such a global scale in a contemporary, information intensive society. The effectiveness of such measures may depend on how citizens perceive the capacity of government to set up and implement sound policies. Indeed, lockdown and confinement policies in general are binding measures that people are not used to, and which raise serious concerns among the population. For this reason governance quality could affect the perception of the benefits related to the government’s choice to impose lockdown, making citizens more inclined to accept it and restrict their movements. In the present paper we empirically investigate the relation between the efficacy of lockdown and governance quality (measured through World Governance Indicators). Our results suggest that countries with higher levels of government effectiveness, rule of law and regulatory quality reach better results in adopting lockdown measures.

Application of an Improved Colored Petri Net Modeling Method in Certain Missile Training System

2015 ◽  
Vol 742 ◽  
pp. 330-334
Author(s):  
Chun Jian Wang ◽  
Wei Yue ◽  
Hai Yan Ji
Keyword(s):  
Complex System ◽  
Petri Net ◽  
Time Use ◽  
Training System ◽  
New Method ◽  
Mathematics Model ◽  
Research Approach ◽  
Complex Environments ◽  
Training Simulator ◽  
First Time

In allusion to the need of analyzing complex system, we have proposed a method named multi-grade color Petri net. We for the first time use this new method to analyze a missile training simulator system. This model can accurately reflect the complex environments of the system and avoid the difficulty occurring often in developing accurate mathematics model by using classical research approach.

Synthesis of Parallel Manipulator with Single DOF

2013 ◽  
Vol 330 ◽  
pp. 639-643 ◽  
Author(s):  
Chung Huang Yu ◽  
Wen Yeuan Chung
Keyword(s):  
Parallel Manipulator ◽  
Design Concept ◽  
Path Generation ◽  
Dimensional Synthesis ◽  
Type Synthesis ◽  
Numerical Example ◽  
Geometrical Constraints ◽  
Moving Platform ◽  
Manipulator Design

This paper proposed a new manipulator design concept which leads to a single DOF system. The system composed of a moving platform and several supporting legs. It can execute the tasks of 3D body guidance or path generation and thus replace expensive manipulators with high DOF in some conditions. There are mainly two steps in designing this manipulator. The first step is type synthesis to determine the number and types of legs. Dimensional synthesis is then executed based on the movement requirements and geometrical constraints. In this study the reduction of the DOF is also analyzed for various legs added between the moving platform and the ground. A numerical example of executing 3D body guidance is given to verify the proposed new concept.

Field Determination of Fracture Propagation Mode Using Downhole Pressure Data

2015 ◽  
Author(s):  
Ali Daneshy ◽  
Chad Touchet ◽  
Fred Hoffman ◽  
Mike McKown
Keyword(s):  
Propagation Mode ◽  
Fluid Migration ◽  
Pressure Data ◽  
Isolation System ◽  
Fracture Orientation ◽  
Coiled Tubing ◽  
Treatment Data ◽  
Set Up ◽  
Adjacent Fractures ◽  
First Time

Abstract This paper presents the analysis results of 60 single stage fracturing treatments performed in a horizontal well using cemented casing sleeves and a coiled tubing deployed frac isolation system as the completion method. In this carefully set-up and executed treatment, separation between the toe stages was 97 feet, and near the heel it was 55 feet. Pressure data was collected above and below the retrievable plug used for stage isolation. This data was used for analysis of fracturing treatment data which included mode of propagation, completion efficiency, and a rough estimate of fracture orientation. The analysis showed that; There was no interaction between adjacent fractures during five of the sixty fracturing stages. None of these was in the well interval with shorter fracture spacingFracture shadowing occurred during six fracture stages, again none in the shorter spacing intervalMinor cement defects (micro-annuli) caused some fluid migration into the passive segment of the well. This happened in 27 stages. Of these; In eleven cases the cement defects were plugged after a while, causing the migration of fracturing fluid into the passive interval to stop.In sixteen other cases the fluid migration through cement micro-annuli continued during fracturing.During ten stages, defective zone isolation and fluid migration caused a pressure increase of several hundred psi in the passive segment of the well. But this did not result in extension of passive fractures.The volume of migrated slurry due to inadequate zone isolation was mostly a very small fraction of the injected volume.During five stages poor cement quality hampered stage isolation and caused immediate link between adjacent active and passive intervals and extension of passive fractures.The data indicate possible connection between the active and one passive fracture in four stages.Shorter spacing between stages increased the incidents of fluid migration due to poor cement qualityThe fracturing pressure variations during the treatments did not indicate presence of large stress shadowingA rough estimation of fracture orientation indicates that they were likely to be vertical and nearly perpendicular to the wellbore.The fracture growth pattern can best be described as off-balance. To our knowledge, this is the first time existence of direct communication between adjacent fractures has been observed through actual pressure interference data.

Excavations in the City of London: First Interim Report, 1974–1975

1977 ◽  
Vol 57 (1) ◽  
pp. 31-66 ◽  
Author(s):  
Brian Hobley ◽  
John Schofield ◽  
Tony Dyson ◽  
Peter R. V. Marsden ◽  
Charles Hill ◽  
...  
Keyword(s):  
Urban Archaeology ◽  
Interim Report ◽  
Set Up ◽  
City Of London ◽  
First Time ◽  
The City ◽  
Important Evidence

SummaryThe Department of Urban Archaeology, City of London, was set up in December 1973 as part of Guildhall Museum, now the Museum of London. Since then it has excavated sixteen sites and carried out numerous watching briefs. Most of the formal excavations have been conducted on the vital waterfront sites, made available for the first time, and on the Roman and medieval defences of the City. Important evidence of the elusive Saxon occupation is gradually coming to light, and the work is accompanied by specialist research, particularly finds, environmental and documentary.

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