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 re...
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 we...
详细信息
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
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 o...
详细信息
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 c...
详细信息
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.
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 Universi...
详细信息
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
Our goal is to disseminate the systemsengineering 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 fr...
详细信息
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 environm...
详细信息
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.
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 ma...
详细信息
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 occupa...
详细信息
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
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...
详细信息
暂无评论