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A boundary model for the thermal creep problem

Fluid Dynamics 1993年第6期28卷 876-878页

作者： Ivchenko, I.N. Loyalka, S.K. Tompson, R.V. Paniculate Systems Research Center and Nuclear Engineering Program University of Missouri-Columbia Columbia Missouri United States

A new integral boundary condition model for determining the particle velocity distribution function in a Knudsen layer, which makes it possible to improve the accuracy of the moment approximations, is proposed. The results for various models are compared with the exact numerical solution of the problem. © 1994 Plenum Publishing Corporation.

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Blood Compatibility of Amphiphilic Poly(N-α-acrylamide-L-lysine-<i>b</i>-dimethylsiloxane) Block Copolymers

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Journal of Biomaterials and Nanobiotechnology 2011年第4期2卷 337-346页

作者： Kazuo Sugiyama Nobuyuki Tanigawa Kohei Shiraishi Cluster of Biotechnology and Chemistry Systems Program in Systems Engineering Graduate School of Systems Engineering Kinki University

Amphiphilic block copolymers poly(LysAA-b-DMS) consisting of a hydrophilic poly(N-α-acrylamide-L-lysine) [poly(LysAA)] segment with different molecular weights and a hydrophobic polydimethylsiloxane (PDMS) segment were prepared as follows. The precursor copolymer poly(Boc-LysAA-OtBu-b-PDMS) was obtained from radical polymerization of N-α-acrylamide-N-ε-tert-butoxycarbonyl-L-lysine-tert-butylester (Boc-LysAA-OtBu) initiated with 4,4’-azobis(polydimethylsiloxane 4-cyanopentanoate) (azo-PDMS) with the molecular weight of PDMS Mw = 4.3 × 103 in the presence of 2-mercaptoethanol (2-ME) as a chain-transfer agent. Removal of the protecting groups of the precursor copolymer was carried out in 80% trifluoroacetic acid aqueous solution to give poly(LysAA-b-DMS)-1-3. The weight average molecular weight of poly(LysAA-b-DMS)-1-3 was Mw = 1.02 × 104 – 2.52 × 104. From the 1H-NMR and fluorescence spectra measurements, poly(LysAA-b-DMS)-1-3 was determined to self-organize and form core-shell micelles in water. The critical micelle concentration (CMC) increased to 1000 - 4000 mg·L–1 with increasing molar ratio of the poly(LysAA) segment from 0.42 to 0.65. From morphological analysis with a scanning probe microscope (SPM), poly(LysAA-b-DMS) has microphase-separated structures made up of hydrophilic and hydrophobic regions with the domain size ranging from several tens to several hundreds of nanometers. Inhibition of thrombin activity of poly(LysAA-b-DMS) was evaluated from the Michaelis constant (KM) and catalytic activity (kcat) for the enzymatic reaction of thrombin and synthetic substrate S-2238 in the presence of poly(LysAA-b-DMS). The KM and kcat were 0.10 - 0.11 mM and 4.04 × 105 – 4.26 × 105 min–1, respectively. Fibrinolytic activity was also verified from the transformation of plasminogen to plasmin by tissue plasminogen activator (t-PA) using synthetic substrate S-2251 in the presence of poly(LysAA-b-DMS). The KM and kcat were 0.07 mM and 5.73 × 106 –5.95 × 106 min–1, respec

关键词： Poly(N-α-acrylamide-L-lysine) Polydimethylsiloxane Block Copolymer Molecular Assembly Blood Compatibility S-2238/S-2251 Biomedical Polymer Material

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Modal analysis under jittering and kernel clock distribution: single-output identification

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Proceedings of the Institution of Civil Engineers: Smart Infrastructure and Construction 2023年第4期177卷 224-235页

作者： Ramadan, Wasim Ozer, Ekin Sustainable Environment and Energy Systems Program Middle East Technical University Northern Cyprus Campus Turkey School of Civil Engineering University College Dublin Dublin Ireland

Smartphones have attracted attention in the structural health monitoring community due to their embedded multisensory platforms suitable for crowdsourcing innovation. Despite their advantages, smartphone sensors are originally designed for user utility rather than technical engineering applications (e.g. vibration analysis and modal identification). Sampling jitter is among those problems adversely influencing smartphone performance as a scientific device that can be used for characterising civil infrastructure dynamic characteristics. With inconsistencies in the sampling period due to jitter effects, the identified modal frequencies of a structure can deviate from the actual value, which is artificially introduced by smartphone clock errors. In this study, the authors formulate the statistical characteristics of the smartphone sampling period through kernel distribution and apply a digital reconstruction remedy to the sampling jitter problem. Through introductory simulations of a sine wave and physical implementations through shaking table tests equipped with smartphones, the efficiency of kernel distribution diagnosis and the signal-reconstruction remedy is presented. Following the simulation and laboratory applications, the proposed techniques are applied to vibration monitoring of a steel pedestrian bridge in terms of the auto power spectral density and short-time Fourier transform of single-output signals. The results show successful rehabilitation of accelerometer data from smartphones, removing jitter-induced errors to a significant extent and accordingly improving the identification accuracy currently in a single-output setting. © 2023 Emerald Publishing Limited: All rights reserved.

关键词： Vibration analysis

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Influences of Shrinkage,Creep,and Temperature on the Load Distributions in Reinforced Concrete Buildings During Construction

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Tsinghua Science and Technology 2009年第6期14卷 756-764页

作者：方东平席海峰王晓明张传敏 School of Civil Engineering Tsinghua University Urban Systems Program CSIRO Sustainable EcosystemsCommonwealth Scientific and Industrial Research Organisation(CSIRO) Henan Development and Reform Commission

Site measurements have shown that slab loads re-distribute, between the slabs during the concrete curing, while the external Ioadings and structural geometry remain the same. Some have assumed that this is caused by concrete shrinkage and creep, but there have been no studies on how these factors exactly influence the load distributions and to what degree these influences exist. This paper analyzes the influences of concrete shrinkage, creep, and temperature on the load re-distributions among slabs. Although these factors may all lead to load re-distribution, the results show that the influence of concrete shrinkage can be neglected. Simulations indicate that shrinkage only reduces slab loads by a maximum of 1.1%. Creep, however, may reduce the maximum slab load by from 3% to 16% for common construction schemes. More importantly, temperature variations between day and night can cause load fluctuation as large as 31.6%. This analysis can, therefore, assist site engineers to more accurately estimate slab loads for construction planning.

关键词： reinforced concrete buildings construction load re-distribution structural characteristic parameter slab-shore interaction shrinkage creep and temperature

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Web-enabled system for managing student applications for a selective industry-sponsored multidisciplinary capstone design program

Web-enabled system for managing student applications for a s...

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2008 ASEE Annual Conference and Exposition

作者： Stanfill, R. Keith University of Florida Integrated Product and Process Design Program Industrial and Systems Engineering Department University of Florida

Integrated Product and Process Design (IPPD) is an institutionalized two-semester industry-sponsored multidisciplinary capstone design option for seniors in engineering, business, and packaging science at the University of Florida. Preparing for the launch of the IPPD program in the fall semester requires coordinating with dozens of project sponsors, faculty and staff from nine academic departments and students from more than 12 disciplines. Obtaining 25 suitable multidisciplinary industry projects each year is a time consuming activity. So too is the process of recruiting and selecting 150 students of the appropriate disciplines to complete these projects. Ideally, as projects are identified and committed, students with the right discipline background are approved and enrolled in the capstone program. If all goes as planned, there will enough students of the right disciplines to complete every project. This balance between project and student recruitment is a challenging systems issue-ignore either and risk program collapse. Further, after spending many hours recruiting a sponsored project, it is particularly disheartening to inform a sponsor that their project cannot be undertaken because too few students of the appropriate disciplines were available to complete the work. From 1995 to 2006, students at the University of Florida applied directly to their academic departments through a paper application for admission into the Integrated Product and Process Design. Academic advisors verified the applicant qualifications against discipline-specific prerequisites, and faculty coordinators approved or rejected applicants. The paper-based process worked, but left many information gaps in the project and student recruitment process. To address these gaps, an information system was developed to streamline the capture, processing, and disposition of student applications. Today, students apply over the web, advisors and coordinators review the applications online, and accept

关键词： Students

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Getting design right: systems engineering for the non-engineer

Getting design right: Systems engineering for the non-engine...

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20th Annual International Symposium of the International Council on systems engineering, INCOSE 2010

作者： Jackson, Peter L. Cornell University Systems Engineering Program Rhodes Hall 206 Ithaca NY 14853 United States

ISBN: (纸本)9781617388873

Our goal is to disseminate the systems engineering process to as broad an audience as possible. This audience includes freshmen engineers, students from non-engineering majors, as well as working managers and staff from a host of different occupations. Reviewing the impediments to the dissemination effort and the success of the Six Sigma movement, we articulate the requirements that a curriculum for non-engineers should satisfy and we propose a particular blended curriculum that satisfies these requirements and highlight its features. We point to three implementations of the curriculum. Experience with this form of the curriculum is still in its infancy. © 2010 by Peter L. Jackson.

关键词： Curricula

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Implementation of revitalized parts, materials and processes standards and specifications

Implementation of revitalized parts, materials and processes...

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31st Annual AAS Rocky Mountain Guidance and Control Conference

作者： Meshel, David C. Encarnació, Pedro A. Systems Engineering Department Imagery Program Division Aerospace Corporation Chantilly VA 20151 United States

ISBN: (纸本)9780877035459

High-reliability (hi-rel) components for use in the space environment differ in requirements from their commercial counterparts, given the extreme temperatures, vacuum, radiation, weightless and atomic oxygen environments, and excessive stress to which they are subject. The performance of these components is highly emphasized, and as their name suggests, reliability is the underlying factor when it comes to adopting these components in all space electronics hardware applications. To properly address these hi-rel requirements, revitalized military standards and specifications and new technical industry standards are now being enforced in National Security Space (NSS) programs at United States Air Force (USAF) Space and Missile systems Center (SMC) and at the National Reconnaissance Office (NRO) and in some civil space National Aeronautics and Space Administration (NASA) programs. These revitalized standards are presented here in the context of their evolution out of an acquisition environment that was lacking in rigorous Parts, Materials, and Process (PM&P) specifications and standards implementation. A historical perspective is offered, establishing the present necessity for the renewal of scrupulous PM&P practices. Select military specifications are discussed, with an emphasis on important issues associated with particular electronic components such as hybrids, microelectronics, diodes, and passive devices.

关键词： NASA

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A diagnosis framework of hybrid dynamic systems based on time fuzzy petri nets

A diagnosis framework of hybrid dynamic systems based on tim...

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作者： Loures, E. Rocha Pascal, J.C. Laboratory for Analysis and Architecture of Systems Toulouse France Graduate Program in Production System Engineering Curitiba Brazil

ISBN: (纸本)008045108X

This paper presents a diagnosis framework based on a qualitative model of the process. Starting from a dynamic abstraction procedure under a defined operating mode a fuzzy partitioning of the variables evolution is made, defining for each measured or observable variable a number of qualitative states. Then time Fuzzy intervals representing the moment of state change are defined. The process behaviour of the operating mode is represented by Time Fuzzy Petri nets (TFPN) model and its evolution is the consequence of events detection due to the partitioning bounds crossing. According to the membership possibility of an event to the estimated time interval and to fuzzy influence knowledge, it is possible to reason about a fault occurrence. The fuzzy data issue from the TFPN components allows evaluating the causes of the fault or failure mode. A model-based diagnosis of a hybrid system is presented. Copyright © 2005 IFAC.

关键词： Hybrid systems

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Different approaches on how to improve braking performance in M3 vehicles to meet secondary brake requirements from ECE R13 regulation through low cost solutions 14

Different approaches on how to improve braking performance i...

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14th SAE Brasil International Brake and Motion Control Colloquium and Exhibit, BRASILBRAKE 2019

作者： Da Cruz, Luciano Ferreira Rudek, Claudemir Freire, Roberto Zanetti Volvo Bus Corporation Volvo Trucks Technology Industrial and Systems Engineering Graduate Program PUCPR Brazil

The braking system of any road vehicle is subject to extensive legislative standards and requirements in many regions around the world. In buses, which belong to M3 category, one of the most critical demands is occupancy rate of passengers that leads to affect Gross Vehicle Weight (GVW). More and more, customers are pushing the manufactures to increase the GVW of buses to allow more passengers inside and consequently increase profitability of the operation. By increasing GVW braking system has to present better performance to fulfill requirements. ECE R13 regulation establishes 2.5m/s2 as minimum Mean Fully Developed Deceleration (MFDD) and 64,4meters as maximum Stopping Distance (SD) acceptable to secondary brake performance. In a 4x2 vehicle with GVW of 19.5 tons fitted with disc brakes these requirements are actually fulfilled, but by adding 600 kg it became out of requirements. Based on the parameters which might affect braking performance, three different approaches were studied, tested and disposed in a decision matrix to choose most feasible in terms of performance, costs, manufacturing and time to implementation: a new protecting valve setup, increasing residual pressure at port 21 and 22;a new pneumatic scheme using a Double Check Valve (DCV) to share residual pressure from non- failed circuit to failed circuit;and finally an exchange of 24" service brake chambers by a 27" in both axles, being those solutions preselected as feasible solutions in terms of less impacts to brake system. Tests were performed considering failure at front (FA) and rear (RA) axles. By taking baseline results with MFDD 5.49% and 1.63%, and SD 3.09% and 4.72% out of requirements for FA and RA failures respectively, test results for proposed solutions showed in a ranking: DCV solution as the best performance, which had improved MFDD by 50.56% and 51.92%, and SD had decreased by 67.51% and 59.44%;27" service chambers as second best solution, which had improved MFDD by 17.80% and 16.23

关键词： Braking performance

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Improving the government purchase card approval process at the u.s. military academy: A lean six sigma application

Improving the government purchase card approval process at t...

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2017 International Annual Conference of the American Society for engineering Management, ASEM 2017

作者： Klein, Micah J. Enos, James R. United States Military Academy Stevens Institute of Technology in the Systems Engineering Program NY United States

The U.S. Army adopted the Lean Six Sigma (LSS) methodology for process improvement in 2004 and has been training LSS practitioners ever since. As part of this training, the Army requires green-belt level candidates to successfully complete a project using the Define, Measure, Analyze, Improve, and Control (DMAIC) process. This paper presents the results of a six-month effort that applied this methodology to government purchase card (GPC) approval process within the Dean's staff at the U.S. Military Academy. Although many associate the LSS process with manufacturing or supply chain processes, this application is an example of how the same methodology will result in the improvement of administrative processes. Through the DMAIC process, the team conducted detailed analysis of the available data, identified several areas for improvement, and implemented controls and procedures to get the process in control and reduce the number of defects in turn-in documentation. The results of the effort were profound and reduced the processing time by over 50% and improved the sigma quality level from 0.5 to 2.4. Additionally, the teams recommended changes to the GPC process are being adopted across the Academy to decrease processing time and improve quality associated with this administrative process. This paper provides an overview of the process and its application to the excessive time and effort required to approve simple purchases with a government credit card as a case study for a successful implementation of the Army's LSS process. © 2017 American Society for engineering Management.

关键词： Six sigma

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