Geometric Design and Analysis of Novel Asymmetrical Rotors for Roots Vacuum Pumps

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Jun Wang ◽  
Shuran Yang ◽  
Rundong Sha ◽  
Hongxin Li ◽  
Chao Xu
Keyword(s):  
Geometric Design ◽  
Geometric Parameters ◽  
The Other ◽  
Design Flexibility ◽  
Circular Arcs ◽  
Study Results

Abstract Roots rotors dramatically determine the performance of Roots vacuum pumps. In order to develop new rotors with higher performance, a pair of novel asymmetrical rotors or eccentric involute rotors were proposed based on the conventional symmetrical involute rotors. Profiles of one rotor consist of four eccentric involutes and four circular arcs; profiles of the other rotor consist of four conjugate curves of eccentric involutes and four circular arcs. A model of the proposed asymmetrical rotors was established, and effects of geometric parameters on the area-utilizing ratio of rotors were analyzed. The study results show that the proposed asymmetrical rotors have more number of independent geometric parameters than the conventional rotors of Roots vacuum pumps, so that the asymmetrical rotors are superior to the conventional rotors in terms of design flexibility. The contents of this study can be applied in the design of Roots vacuum pumps.

Geometric design and analysis of scroll compressors with a novel circular involute modified wrap

2021 ◽  
pp. 095440892110530
Author(s):  
Jun Wang ◽  
Yi Han ◽  
Zhoujin Xi ◽  
Zengli Wang ◽  
Dong Cui
Keyword(s):  
Compression Ratio ◽  
Geometric Model ◽  
Geometric Parameters ◽  
Circular Arc ◽  
Design Flexibility ◽  
Study Results ◽  
Temperature Load ◽  
Central Regions ◽  
Working Performance ◽  
And Performance

The scroll geometry in the central region of the scroll wrap plays a crucial role in determining the working performance of scroll compressors. In order to improve the comprehensive performance of scroll wraps, in this study, a novel circular involute modified wrap was put forward, in which the central and peripheral wrap profiles were connected by a circular involute in the central regions, so that a pair of fully smooth and correct meshing scroll wraps were generated. A geometric model of the involute modified wrap were proposed, and then equations of the wrap profiles and relations between geometric parameters were derived. Effects of geometric parameters on the shape and performance of the involute modified wrap were discussed in detail. Furthermore, the compression ratio of the involute modified wrap was studied by numerical simulation, and the deformation of the involute modified wrap produced by temperature load and pressure load was calculated, compared with the conventional circular arc modified wrap under the same geometric shape of scroll compressors. Study results demonstrate that the proposed involute modified wrap may simultaneously improve the compression ratio and the strength of wrap head for scroll compressors; in addition, the involute modified wrap is good for design flexibility, and therefore is superior to the circular arc modified wrap.

An Elimination Procedure for Solving the Geometric Design of Spatial 3R Manipulators

2005 ◽  
Vol 128 (1) ◽  
pp. 142-145 ◽  
Author(s):  
Eric Lee ◽  
Constantinos Mavroidis
Keyword(s):  
Design Problem ◽  
Geometric Design ◽  
Geometric Parameters ◽  
The Other ◽  
Design Parameters ◽  
Single Variable ◽  
Serial Link ◽  
End Effector ◽  
Elimination Procedure ◽  
First Time

In this paper, the geometric design problem of serial-link robot manipulators with three revolute (R) joints when three precision points are specified is solved using an algebraic elimination method for the first time. Three spatial positions and orientations are defined and the dimensions of the geometric parameters of the 3R manipulator are computed so that the manipulator will be able to place its end-effector at these three prespecified locations. In this problem, six of the design parameters are set as free choices and their values are selected arbitrarily. For the specific case studied in this paper, a 12 deg single variable polynomial is calculated that has eight roots that are the design solutions and the other four roots are extraneous solutions.

An Algebraic Elimination Based Algorithm for Solving the Geometric Design Problem of Spatial 3R Manipulators

2004 ◽  
Author(s):  
Eric Lee ◽  
Constantinos Mavroidis
Keyword(s):  
Design Problem ◽  
Geometric Design ◽  
Geometric Parameters ◽  
The Other ◽  
Design Parameters ◽  
Single Variable ◽  
Serial Link ◽  
Elimination Method ◽  
End Effector ◽  
First Time

In this paper, the geometric design problem of serial-link robot manipulators with three revolute (R) joints when three precision points are specified is solved using an algebraic elimination method for the first time. Three spatial positions and orientations are defined and the dimensions of the geometric parameters of the 3-R manipulator are computed so that the manipulator will be able to place its end-effector at these three pre-specified locations. In this problem, six of the design parameters are set as free choices and their values are selected arbitrarily. For the specific case studied in this paper, a twelve-degree single variable polynomial is calculated that has eight roots that are the design solutions and the other four roots are extraneous solutions.

scholarly journals Conversion Between Cubic Bezier Curves and Catmull–Rom Splines

2021 ◽  
Vol 2 (5) ◽  
Author(s):  
Soroosh Tayebi Arasteh ◽  
Adam Kalisz
Keyword(s):  
Computer Graphics ◽  
Geometric Design ◽  
The Other ◽  
Control Points ◽  
Complex Surfaces ◽  
Linear Transformations ◽  
Computer Aided Geometric Design ◽  
Cubic Curves ◽  
Original Curve ◽  
Computer Aided

AbstractSplines are one of the main methods of mathematically representing complicated shapes, which have become the primary technique in the fields of Computer Graphics (CG) and Computer-Aided Geometric Design (CAGD) for modeling complex surfaces. Among all, Bézier and Catmull–Rom splines are the most common in the sub-fields of engineering. In this paper, we focus on conversion between cubic Bézier and Catmull–Rom curve segments, rather than going through their properties. By deriving the conversion equations, we aim at converting the original set of the control points of either of the Catmull–Rom or Bézier cubic curves to a new set of control points, which corresponds to approximately the same shape as the original curve, when considered as the set of the control points of the other curve. Due to providing simple linear transformations of control points, the method is very simple, efficient, and easy to implement, which is further validated in this paper using some numerical and visual examples.

scholarly journals Morphological Aspects of Ciliary Motility

1967 ◽  
Vol 50 (6) ◽  
pp. 241-258 ◽  
Author(s):  
Peter Satir
Keyword(s):  
The Other ◽  
Radius Of Curvature ◽  
Arc Length ◽  
Apparent Displacement ◽  
Shaft Length ◽  
Ciliary Motility ◽  
Morphological Aspects ◽  
Circular Arcs ◽  
The Relationship

In Elliptio complanatus lateral cilia, two distinct patterns of filament termination can be discerned. In one case, all nine filaments are present and all are single; in the second, at least one filament is missing but doublets are still present. These probably represent different configurations within one cilium in different stroke positions; to get from one to the other, some peripheral filaments must move with respect to others. The data are consistent with the hypothesis that the filaments themselves do not change length, but rather slide past one another to accommodate increasing curvature. The bent regions of the cilium are in the form of circular arcs. In a few cases, apparent displacement of filaments at the tip (Δl) can be shown to be accounted for if we assume that all differences are generated within these arcs. The displacement per degree of bend is 35 A. Regions of bent arc are initially confined to the base of the cilium but move up the shaft as straight regions appear below them. From the relationship between arc length and radius of curvature, a shaft length that is the unit that initially bends and slides may be defined. Quantal displacements of the length of one 14S dynein may perhaps occur at sites between filaments at opposite sides of such a unit as sliding occurs.

scholarly journals Management of accounting information resources security in Polish entities – study results

2018 ◽  
Vol 2018 (97 (153)) ◽  
pp. 115-139
Author(s):  
Elżbieta Szczepankiewicz
Keyword(s):  
Empirical Research ◽  
Accounting Information ◽  
Information Resources ◽  
The Other ◽  
Three Dimensions ◽  
Accounting System ◽  
External Threats ◽  
Study Results ◽  
Cyber Space ◽  
Business Entities

The presence of contemporary entities in the cyber-space shows that IT offers unlimited possibilities of running a business and developing an organisation. On the other hand, it involves a greater number of internal and external threats in the area of accounting information resources security. The objective of the paper is to diagnose the current level of accounting information resources security (AIRS) assurance in Polish business entities. The paper analyses two research hypotheses. In accordance with the first one, the AIRS assurance level in various entity groups may be different, even though all entities should have implemented the same requirements of the Accounting Act in the analyzed area. The identified differences may result from the effect of additional, industry-specific regulations. The other hypothesis claims that in the private business area, accounting and auditing companies adhere to AIRS regulations more strictly than other small and medium enterprises. The paper defines the fundamental factors affecting the functioning of corporate accounting systems in the three dimensions of the cyber-space. Subsequently, the author presents the results of empirical research on how corporate information security is ensured in the context of internal accounting control systems and the requirements of the Polish Accounting Act. The results of the empirical research show how the management of the analysed entities crafts the basic elements of their internal environment as well as internal communication and control processes connected with ensuring information resources security. The results also show the management’s approach to various aspects of risk management of accounting information resources security, as well as to adherence to organisational and administrative procedures, and to hardware and software safeguards in the IT environment of the accounting system. The issues analysed in the present paper open a scholarly discussion that should lead to the development of theoretical models, recommendation of efficient methods and tools, as well as indication of adequate legislative initiatives. Research methods used by the author include analysis of literature and legislation, analysis of survey results, deduction and inference.

scholarly journals Cost-Effectiveness Analysis of Biopharmaceuticals for Treating Rheumatoid Arthritis: Infliximab, Adalimumab, and Etanercept

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Ahmad Gholami ◽  
Jassem Azizpoor ◽  
Elham Aflaki ◽  
Mehdi Rezaee ◽  
Khosro Keshavarz
Keyword(s):  
Rheumatoid Arthritis ◽  
Sensitivity Analysis ◽  
Cost Effectiveness ◽  
Cost Effective ◽  
The Other ◽  
Cost Data ◽  
Fars Province ◽  
Study Results ◽  
The Mean ◽  
The Cost

Introduction. Rheumatoid arthritis (RA) is a chronic progressive inflammatory disease that causes joint destruction. The condition imposes a significant economic burden on patients and societies. The present study is aimed at evaluating the cost-effectiveness of Infliximab, Adalimumab, and Etanercept in treating rheumatoid arthritis in Iran. Methods. This is a cost-effectiveness study of economic evaluation in which the Markov model was used. The study was carried out on 154 patients with rheumatoid arthritis in Fars province taking Infliximab, Adalimumab, and Etanercept. The patients were selected through sampling. In this study, the cost data were collected from a community perspective, and the outcomes were the mean reductions in DAS-28 and QALY. The cost data collection form and the EQ-5D questionnaire were also used to collect the required data. The results were presented in the form of an incremental cost-effectiveness ratio, and the sensitivity analysis was used to measure the robustness of the study results. The TreeAge Pro and Excel softwares were used to analyze the collected data. Results. The results showed that the mean costs and the QALY rates in the Infliximab, Adalimumab, and Etanercept arms were $ 79,518.33 and 12.34, $ 91,695.59 and 13.25, and $ 87,440.92 and 11.79, respectively. The one-way sensitivity analysis confirmed the robustness of the results. In addition, the results of the probabilistic sensitivity analysis (PSA) indicated that on the cost-effectiveness acceptability curve, Infliximab was in the acceptance area and below the threshold in 77% of simulations. The scatter plot was in the mentioned area in 81% and 91% of simulations compared with Adalimumab and Etanercept, respectively, implying lower costs and higher effectiveness than the other two alternatives. Therefore, the strategy was more cost-effective. Conclusion. According to the results of this study, Infliximab was more cost-effective than the other two medications. Therefore, it is recommended that physicians use this medication as the priority in treating rheumatoid arthritis. It is also suggested that health policymakers consider the present study results in preparing treatment guidelines for RA.

scholarly journals Examining Distance Learners in Hybrid Synchronous Instruction: Successes and Challenges

2017 ◽  
Vol 21 (4) ◽  
Author(s):  
Enilda Romero-Hall ◽  
Cristiane Rocha Vicentini
Keyword(s):  
Data Analysis ◽  
Focus Group ◽  
The Other ◽  
Distance Learners ◽  
Electronic Journals ◽  
Face To Face ◽  
Individual Interviews ◽  
Study Results ◽  
Successes And Challenges

This paper reports on a case study investigating distance learners participating in graduate-level hybrid synchronous instruction. This research helps inform the design of hybrid synchronous instruction in which face-to-face and distance learners engage in class sessions. Data were collected using electronic journals, individual interviews, and a focus group. The results of the data analysis provide evidence that in this case, hybrid synchronous instruction improved the study habits of distance learners. On the other hand, the case study results also revealed that there are challenging pedogogical aspects which the distance learners had to overcome during hybrid synchronous instruction. Among such challenges were the interactions, relationships, and communication exchanges between distance learners, their face-to-face counterparts, and the instructor.

scholarly journals ROLE OF EARLY LAPAROSCOPIC CHOLECYSTECTOMY IN PREVENTING COMPLICATIONS OF ACUTE CHOLECYSTITIS

2020 ◽  
pp. 1-3
Author(s):  
Mukesh Kumar ◽  
Sanjay Kumar Suman ◽  
Pawan Kumar Jha ◽  
Debarshi Jana
Keyword(s):  
Laparoscopic Cholecystectomy ◽  
Bile Duct ◽  
Conservative Treatment ◽  
Common Bile Duct ◽  
Acute Cholecystitis ◽  
Common Bile Duct Stone ◽  
Bile Duct Stone ◽  
The Other ◽  
Study Results ◽  
Delayed Group

Background: Cholecystectomy is the standard and the only curative treatment for acutecholecystitis. The complications of acute cholecystitis are disastrous to the patients; on the other hand, conservative treatment is associated with recurrence of symptoms and other complications as common bile duct stone. The aim of this study is to weight out the complication of emergency surgery against the complications of conservative treatment in patients with acute cholecystitis. Materials andmethods: A total of 80 patients were included in the study. All Patients underwent early laparoscopiccholecystectomy or interval laparoscopic cholecystectomies for acute calcularcholecystitis from October 2017 to September 2019 were included in the study. Results: The overall complication rate was 15% (6 of 40 in early group and 10% (4 of 40) in the delayed group. One case of delayed group suffering recurrent acute attack and the other one suffering common bile duct stone, there was no major bile duct injury in the delayed group. Conclusion: Laparoscopic cholecystectomy is a safe and cost-effective approach for the treatment of acute cholecystitis within 72 h after the onset of attack.

scholarly journals Development of gypsy moth (Lymantria dispar L) on the foliage of Quercus cerris L., Q. Petraea (matt) Liebl. and Q. Robur L. in the controlled conditions

2007 ◽  
pp. 55-67 ◽  
Author(s):  
Slobodan Milanovic
Keyword(s):  
Relative Humidity ◽  
Host Plant ◽  
Gypsy Moth ◽  
Lymantria Dispar ◽  
Environmental Conditions ◽  
Quercus Robur ◽  
Quercus Petraea ◽  
The Other ◽  
Study Results ◽  
Quercus Cerris

The development of Gypsy moth (Lymantria dispar L) was monitored in laboratory conditions, on the foliage of the species Quercus cerris L. Quercus petraea (Matt) Liebl. and Quercus robur L. The experiment was established in the controlled environmental conditions, at the temperature of 25?C, photoperiod 14:10 (day: night) and relative humidity 70%. The objective of the research was to determine the suitability of the study host plant species for gypsy moth development. The study results show that Gypsy moth caterpillars cultivated on Q. petraea foliage had a lower survival, higher number of moultings, longer preadult development and lower fecundity, which makes this species less suitable compared to the other two. Gypsy moth caterpillars cultivated on Q. cerris foliage had the highest survival degree the lowest number of moultings, the shortest preadult development and the highest fecundity, which makes this species the most favourable for gypsy moth development. Q. robur was between the former two species in this respect.

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