Effect of Mechanical Alignment System on Assembly Accuracy

2003 ◽  
Vol 125 (3) ◽  
pp. 595-608 ◽  
Author(s):  
Neville K. S. Lee ◽  
Grace H. Yu ◽  
J. Y. Chen ◽  
Ajay Joneja
Keyword(s):  
Simulation Models ◽  
Mechanical Alignment ◽  
Mechanical Assembly ◽  
Surface Errors ◽  
Error Surface ◽  
Assembly Accuracy ◽  
Alignment System ◽  
Order Of Magnitude ◽  
Proper Design ◽  
Selection Of

Mechanical means of positioning are frequently used in mechanical assembly processes. However, very little attention has been paid to the proper design and selection of mechanical alignment systems (MAS) for assembly processes. In this paper, we study the performance of different MAS in terms of assembly accuracy in the presence of the form error, surface waviness and surface roughness of the references surfaces. In particular, simulation models are used to investigate how the datum pin configuration, datum pin location and datum geometry of the MAS would affect the assembly accuracy in the presence of surface errors of the workpieces. Our investigation can provide insight into how to design MAS for optimum performance for assembly accuracy. Our analysis shows that over an order of magnitude of difference in assembly accuracy can exist between using properly designed MAS and poorly design MAS.

Effect of Mechanical Alignment System on Assembly Accuracy

2000 ◽  
Author(s):  
Neville K. S. Lee ◽  
Grace H. Yu ◽  
Y. Zou ◽  
J. Y. Chen ◽  
Ajay Joneja
Keyword(s):  
Alignment Accuracy ◽  
Mechanical Alignment ◽  
Mechanical Assembly ◽  
Surface Waviness ◽  
Form Errors ◽  
Multi Stage ◽  
Assembly Accuracy ◽  
Alignment System ◽  
Simulation Based ◽  
Selection Of

Abstract Mechanical means of positioning are frequently used in mechanical assembly processes. However, very little attention has been paid to the selection of mechanical alignment systems (MAS) for assembly processes. Our analysis shows that if the MAS are not properly selected, the form errors as well surface waviness and roughness of the workpieces to be assembled can badly limit the level of accuracy achievable. A simulation-based methodology is described to study the alignment accuracy for multi-stage processes. Such cases are common, where fabrication operations are done on parts before they are assembled. The study shows that if the workpieces are aligned in the same orientation, using similar or identical MAS for the fabrication processes and assembly processes, then the effect of the form errors as well as surface waviness and roughness of the workpieces can be greatly suppressed.

Effect of Datum Securing Method on Precision of Mechanical Alignment System

1999 ◽  
Vol 122 (2) ◽  
pp. 350-359 ◽  
Author(s):  
Neville K. S. Lee ◽  
Keith K. C. Hon ◽  
Venus P. Y. Cheung ◽  
Ajay Joneja
Keyword(s):  
High Resolution ◽  
Monitoring System ◽  
Mechanical Alignment ◽  
Optical Position ◽  
Alignment System ◽  
Precision Level ◽  
Order Of Magnitude ◽  
Position Monitoring ◽  
Magnitude Improvement ◽  
The Way

In this research, the achievable precision level using mechanical datums for manufacturing has been studied. Specifically, the effect of how a datum is secured in a mechanical alignment system was studied with the aid of a high-resolution multidimensional optical position monitoring system developed for the purpose. The study shows that the way datum is secured can be a major factor affecting the alignment precision of a mechanical alignment system. For a datum prepared by randomly inserting dowel pins into precision bored holes, a common practice in industry, the precision level was found to be worse than 10 μm. The results also show that the precision level can be readily improved by addressing this major cause of inaccuracy. Different methods depending on manufacturing requirements and constraints have been proposed. Some of these simple procedures lead to more than an order of magnitude improvement in alignment precision. [S1087-1357(00)02001-3]

scholarly journals Topographical and Biomechanical Guidance of Electrospun Fibers for Biomedical Applications

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2896
Author(s):  
Sara Ferraris ◽  
Silvia Spriano ◽  
Alessandro Calogero Scalia ◽  
Andrea Cochis ◽  
Lia Rimondini ◽  
...  
Keyword(s):  
Surface Modification ◽  
Biomedical Applications ◽  
Biomedical Application ◽  
Electrospun Fibers ◽  
Natural Polymers ◽  
Polymeric Fibers ◽  
Biological Phenomena ◽  
Proper Design ◽  
Synthetic And Natural Polymers ◽  
Selection Of

Electrospinning is gaining increasing interest in the biomedical field as an eco-friendly and economic technique for production of random and oriented polymeric fibers. The aim of this review was to give an overview of electrospinning potentialities in the production of fibers for biomedical applications with a focus on the possibility to combine biomechanical and topographical stimuli. In fact, selection of the polymer and the eventual surface modification of the fibers allow selection of the proper chemical/biological signal to be administered to the cells. Moreover, a proper design of fiber orientation, dimension, and topography can give the opportunity to drive cell growth also from a spatial standpoint. At this purpose, the review contains a first introduction on potentialities of electrospinning for the obtainment of random and oriented fibers both with synthetic and natural polymers. The biological phenomena which can be guided and promoted by fibers composition and topography are in depth investigated and discussed in the second section of the paper. Finally, the recent strategies developed in the scientific community for the realization of electrospun fibers and for their surface modification for biomedical application are presented and discussed in the last section.

Functionalization of liquid metal nanoparticles via the RAFT process

2021 ◽  
Author(s):  
Bo Fan ◽  
Jing Wan ◽  
Yiyi Liu ◽  
Wendy Wenjun Tian ◽  
San H. Thang
Keyword(s):  
Liquid Metal ◽  
Metal Nanoparticles ◽  
Grafted Polymers ◽  
Proper Design ◽  
Selection Of

The proper design and selection of RAFT agents allow the preparation of eutectic gallium–indium (EGaIn) based liquid metal nanoparticles with grafted polymers.

Selection of Representative Scenarios Using Multiple Simulation Outputs for Robust Well Placement Optimization in Greenfields

2021 ◽  
Author(s):  
Seyed Kourosh Mahjour ◽  
Antonio Alberto Souza Santos ◽  
Susana Margarida da Graca Santos ◽  
Denis Jose Schiozer
Keyword(s):  
Reference Model ◽  
Simulation Models ◽  
Cumulative Distribution ◽  
Small Subset ◽  
Fine Grid ◽  
Well Placement ◽  
Placement Optimization ◽  
Well Placement Optimization ◽  
Selection Of ◽  
Dynamic Uncertainties

Abstract In greenfield projects, robust well placement optimization under different scenarios of uncertainty technically requires hundreds to thousands of evaluations to be processed by a flow simulator. However, the simulation process for so many evaluations can be computationally expensive. Hence, simulation runs are generally applied over a small subset of scenarios called representative scenarios (RS) approximately showing the statistical features of the full ensemble. In this work, we evaluated two workflows for robust well placement optimization using the selection of (1) representative geostatistical realizations (RGR) under geological uncertainties (Workflow A), and (2) representative (simulation) models (RM) under the combination of geological and reservoir (dynamic) uncertainties (Workflow B). In both workflows, an existing RS selection technique was used by measuring the mismatches between the cumulative distribution of multiple simulation outputs from the subset and the full ensemble. We applied the Iterative Discretized Latin Hypercube (IDLHC) to optimize the well placements using the RS sets selected from each workflow and maximizing the expected monetary value (EMV) as the objective function. We evaluated the workflows in terms of (1) representativeness of the RS in different production strategies, (2) quality of the defined robust strategies, and (3) computational costs. To obtain and validate the results, we employed the synthetic UNISIM-II-D-BO benchmark case with uncertain variables and the reference fine- grid model, UNISIM-II-R, which works as a real case. This work investigated the overall impacts of the robust well placement optimization workflows considering uncertain scenarios and application on the reference model. Additionally, we highlighted and evaluated the importance of geological and dynamic uncertainties in the RS selection for efficient robust well placement optimization.

scholarly journals A numerical simulation of realistic top coal caving intervals under different top coal thicknesses in longwall top coal caving working face

2021 ◽  
Author(s):  
Chuang Liu ◽  
Huamin Li
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Distinct Element ◽  
Simulation Models ◽  
Simulation Software ◽  
Thick Coal Seam ◽  
Coal Recovery ◽  
Working Face ◽  
Longwall Top Coal Caving ◽  
Selection Of

Abstract In the process of longwall top coal caving, the selection of the top coal caving interval along the advancing direction of the working face has an important effect on the top coal recovery. To explore a realistic top coal caving interval of the longwall top coal caving working face, longwall top coal caving panel 8202 in the Tongxin Coal Mine is used as an example, and 30 numerical simulation models are established by using Continuum-based Distinct Element Method (CDEM) simulation software to study the top coal recovery with 4.0 m, 8.0 m, 12.0 m, 16.0 m, 20.0 m and 24.0 m top coal thicknesses and 0.8 m, 1.0 m, 1.2 m, 1.6 m and 2.4 m top coal caving intervals. The results show that with an increase in the top coal caving interval, the single top coal caving amount increases. The top coal recovery is the highest with a 0.8 m top coal caving interval when the thickness of the top coal is less than 4.0 m, and it is the highest with a 1.2 m top coal caving interval when the coal seam thickness is greater than 4.0 m. These results provide a reference for the selection of a realistic top coal caving interval in thick coal seam caving mining.

How effective is KRM-1648 in treatment of disseminated Mycobacterium avium complex infections in beige mice?

1996 ◽  
Vol 40 (2) ◽  
pp. 437-442 ◽  
Author(s):  
B Ji ◽  
N Lounis ◽  
C Truffot-Pernot ◽  
J Grosset
Keyword(s):  
Mycobacterium Avium ◽  
Mycobacterium Avium Complex ◽  
Antimicrobial Effect ◽  
Bacteriostatic Effect ◽  
Dose Selection ◽  
Order Of Magnitude ◽  
The Mean ◽  
Resistant Mutants ◽  
Selection Of

Although the MICs of 3'-hydroxy-5'-(4-isobutyl-1-piperazinyl)benzoxazinorifamycin, or KRM-1648 (KRM), for Mycobacterium avium complex (MAC) were significantly lower than those of other drugs, its in vivo activity was very weak. Beginning 28 days after inoculation, beige mice that had been infected intravenously with 1.87 x 10(7) CFU of MAC 101 were administered KRM alone, clarithromycin (CLARI) alone, or CLARI plus KRM six times weekly for 16 weeks. In contrast to the mice treated with CLARI-containing regimens, the mortality and the mean spleen weights of mice treated with KRM alone (either 10 or 20 mg/kg of body weight per dose) did not differ significantly from those of untreated mice, their numbers of CFU were very much greater than pretreatment values, and multiplication of MAC was only slightly inhibited. Although monotherapy by KRM selected KRM-resistant mutants, the selection was very weak; the mean number of CFU and the frequency of KRM-resistant mutants increased by no more than 1 order of magnitude after 16 weeks of treatment with KRM at 20 mg/kg per dose. Selection of CLARI-resistant mutants was inhibited but not completely prevented by treatment of the mice with CLARI plus KRM. These results indicate that KRM displayed only a weak bacteriostatic effect against the isolate tested in the beige mouse model; its ability to enhance the antimicrobial effect of CLARI or to prevent emergence of CLARI-resistant mutants was very limited.

Locally Available Aggregate and Sediment Production

2003 ◽  
Vol 1819 (1) ◽  
pp. 185-193 ◽  
Author(s):  
Randy B. Foltz ◽  
Mark Truebe
Keyword(s):  
Road Construction ◽  
Forest Road ◽  
Sediment Production ◽  
Magnitude Range ◽  
Long Duration ◽  
Order Of Magnitude ◽  
Equivalent Test ◽  
Basic Characteristics ◽  
Material Tests ◽  
Selection Of

Selection of suitable locally available materials to build strong and durable roads with aggregate surfaces is desired to minimize road construction and maintenance costs and to minimize the detrimental effects of sedimentation. Eighteen aggregates were selected from local sources in Idaho, Oregon, South Dakota, and Washington State. Aggregate was placed in shallow metal frames and compacted to simulate a forest road. The levels of runoff and sediment from a highintensity, long-duration simulated rainstorm were measured. The material tests selected for use in the study included ones that define the basic characteristics of the aggregate, along with a number of tests intended to predict susceptibility to erosion. Each of the tests was statistically evaluated to identify those that best predicted the perceived aggregate quality. The two best indicators of aggregate quality were the results of the sand equivalent test and the P20 portion of the Oregon air degradation test. The best indicator of either runoff or sediment production was the fraction passing the 0.6-mm sieve. Acceptable aggregates, both those of good quality and those of marginal quality, exhibited a 2-order-of-magnitude range in both runoff and sediment production.

scholarly journals Significant factors affecting the selection of rational options for power supply in an off-grid zone

2019 ◽  
Vol 77 ◽  
pp. 02006
Author(s):  
Ivanova Irina
Keyword(s):  
Power Supply ◽  
Methodological Approach ◽  
Simulation Models ◽  
Economic Indicators ◽  
Factors Affecting ◽  
Fuel Delivery ◽  
Generating Equipment ◽  
Selection Of ◽  
Significant Factors

The paper presents a short characteristic of an off-grid zone in the eastern regions of the Russian Federation. The main problems of power supply to consumers in this zone are described, and possible options for solving them are provided. A methodological approach and model tools to estimate the efficiency of alternative options of power supply to off-grid consumers are described. The factors affecting the selection of a rational option of power supply in the off-grid zone are classified. We show the interconnection between the main significant factors (availability of grid infrastructure, local fuel resources, complexity of fuel delivery logistics, characteristics of accessible power-generating equipment, and environmental constraints) and their impact on economic indicators of alternative options. Based on the systematized results of long-term studies, we present a scheme designed to select a rational option of power supply to a particular off-grid consumer according to characteristics of the described factors. Keywords: Off-grid consumers, alternative options, impact of factors, economic indicators, methodological approach, simulation models, economic efficiency.

Spiral Wound Gasket Compressibility and Pressure Ratings

2013 ◽  
Author(s):  
John McCarthy ◽  
A. Fitzgerald (Jerry) Waterland ◽  
Dan Reid
Keyword(s):  
Low Pressure ◽  
Pressure Application ◽  
Industry Practice ◽  
Proper Design ◽  
Design Characteristics ◽  
Selection Of ◽  
Spiral Wound

The industry practice of using pressure rating nomenclature to describe spiral wound gasket compressibility can contribute to some level of confusion regarding the proper design and selection of these gaskets. This situation can result in a misconception that a more easily compressed “soft” gasket (for example, “0–999 psi” rating) cannot be used in a higher pressure application. This is not necessarily true, and in many cases a softer (less dense) gasket construction can actually be beneficial in both high and low pressure applications. This article addresses both the terminology used to describe spiral wound gasket compressibility and the design characteristics of these gaskets in an effort to improve the understanding of this subject.

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