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Dynamic Forces (dynamic + force)
Selected AbstractsUse of collision shear walls to minimize seismic separation and to protect adjacent buildings from collapse due to earthquake-induced poundingEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2008S. A. Anagnostopoulos Abstract The use of collision shear walls (bumper-type), acting transversely to the side subject to pounding, as a measure to minimize damage of reinforced concrete buildings in contact, is investigated using 5-story building models. The buildings were designed according to the Greek anti-seismic and reinforced concrete design codes. Owing to story height differences potential pounding in case of an earthquake will occur between floor slabs, a case specifically chosen because this is when pounding can turn out to be catastrophic. The investigation is carried out using nonlinear dynamic analyses for a real earthquake motion and also a simplified solution for a triangular dynamic force of short duration, comparable to the forces caused by pounding. For such analyses, nonlinear, prismatic beam,column elements are used and the effects of pounding are expressed in terms of changes in rotational ductility factors of the building elements. The local effects of pounding on the collision shear walls are investigated using a detailed nonlinear finite element model of the shear walls and results are expressed in terms of induced stresses. It is found that pounding will cause instantaneous acceleration pulses in the colliding buildings and will somewhat increase ductility demands in the members of the top floor, but all within tolerable limits. At the same time the collision walls will suffer repairable local damage at the points of contact, but will effectively protect both buildings from collapse, which could occur if columns were in the place of the walls. Copyright © 2008 John Wiley & Sons, Ltd. [source] Tendon-defect and muscle-unloaded models for relating a rotator cuff tear to glenohumeral stabilityJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2000Horng-Chaung Hsu Rotator cuff tear and glenohumeral instability are closely related. Any tear may disturb muscle force generation due to pain inhibition. In addition, a full-thickness tear may foster instability by removing a structural element constraining the joint. It was hypothesized that the loss of both dynamic force and static constraint with a rotator cuff tear will affect glenohumeral stability. In a tendon-defect model, dynamic and static elements of the joint were sacrificed. In a muscle-unloaded model, only the dynamic element was removed. The location and size of the defect were also investigated. The effect on instability of a small tendon defect was less than that of muscle unloading, implying that a patient with a small tear would have less instability than a patient with weak or nonfunctioning supraspinatus and infraspinatus muscles. On the other hand, with a larger tear the defect had a greater effect than muscle-unloading because sectioning of the glenohumeral and coracohumeral ligaments was included in the model. Clinically, such a defect in the front is critical for anterior stability because it might insult the important anterior capsule ligamentous complex. Orthopaedic surgeons should pay attention, therefore, to the effect of possible associated lesions of static constraints based on the size and location of the tear in addition to the dynamic stabilizer. [source] Advanced models for erosion corrosion and its mitigation,MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2008G. Schmitt Erosion corrosion, i.e., flow-induced localized corrosion (FILC) is initiated when flow dynamic forces surpass the fracture energy of protective layers or scales on metals. With a new model the maximum interaction energies between flowing media and solid walls can be quantified in terms of "freak" energy densities created during singular events (freak events) of perpendicular impacts by near-wall microturbulence elements. The freak energy densities are in the megaPascal range and match well in the order of magnitude with fracture energies of protective layers and can be estimated from Wavelet diagnostics of electrochemical current noise measured at microelectrodes under mass transport controlled conditions. This solves the problem that wall shear stresses, generally used to quantify critical flow intensities for FILC initiation, range several orders of magnitude (Pa range) below the fracture energies of protective layers. The new advanced model allows for the first time to quantify the maximum fluid dynamic forces exerted on solid walls under different turbulent and disturbed flow conditions (one-phase liquid flow on jet impinged surfaces and on coupons in rotated cages, surfaces impacted by slug flow and gas-pulsed impinging jets). Drag reducing additives were shown to reduce freak energy densities to values significantly below fracture energies of protective layers and hence inhibit initiation of FILC. The onset of FILC can be monitored online with the newly developed CoulCount method, an easy-to-use, non-invasive diagnostic tool which evaluates electrochemical current noise between jet impinged electrode pairs made from the metals to be tested. [source] Model of inelastic impact of unit loadsPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2009Tomasz Piatkowski Abstract In this study, the authors present a model of the inelastic impact of bodies that takes place during handling of unit loads (cubiform parcels). A modified non-linear Kelvin model is proposed, in which the relationships between object strains and elastic and damping forces of the impact are represented by power functions. The results of analytical investigations on the proposed model were confirmed by experiments consisting in tests of free fall of the load on rigid ground and on elastic beam. The developed model allows the assessment of the influence of mechanical properties of loads and conveyor-line deflection mechanisms as well as impact velocity, on the dynamic forces exerted on the manipulated objects during the impact. Copyright © 2008 John Wiley & Sons, Ltd. [source] UPSTREAM VOLATILITY IN THE SUPPLY CHAIN: THE MACHINE TOOL INDUSTRY AS A CASE STUDYPRODUCTION AND OPERATIONS MANAGEMENT, Issue 3 2000EDWARD G. ANDERSON JR. Cyclicality is a well-known and accepted fact of life in market-driven economies. Less well known or understood, however, is the phenomenon of amplification as one looks "upstream" in the industrial supply chain. We examine the amplification phenomenon and its implications through the lens of one upstream industry that is notorious for the intensity of the business cycles it faces: the machine tool industry. Amplification of demand volatility in capital equipment supply chains, e. g., machine tools, is particularly large relative to that seen in distribution and component parts supply chains. We present a system dynamics simulation model to capture demand volatility amplification in capital supply chains. We explore the lead-time, inventory, production, productivity, and staffing implications of these dynamic forces. Several results stand out. First, volatility hurts productivity and lowers average worker experience. Second, even though machine tool builders can do little to reduce the volatility in their order streams through choice of forecast rule, a smoother forecasting policy will lead companies to retain more of their skilled work force. This retention of skilled employees is often cited as one of the advantages that European and Japanese companies have had relative to their U. S. competitors. Our results suggest some insights for supply chain design and management: downstream customers can do a great deal to reduce the volatility for upstream suppliers through their choice of order forecast rule. In particular, companies that use smoother forecasting policies tend to impose less of their own volatility upon their supply base and may consequently enjoy system-wide cost reduction. [source] Evolution-Motion of Crustobodies and Geotectonic MetallogenyACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2000CHEN Guoda Abstract, Following the paper entitled A Preliminary Proposal on Crustobody Geotectonics presented by the first author to the 30th IGC in 1996, this paper further extends and elucidates the concept of crustobody in order to make a unifying study of the evolution and motion of crustal structures and to understand the law governing the formation and development of the earth' crust. In this paper the characteristics of crustobody evolution-motion are given. The authors lay emphasis on the relationship between crustobody evolution-motion and tectonic metallogeny. In the end, a multiple dynamic system of the crustobody evolution-motion is discussed from internal and external dynamic forces, and the mantle creep in internal dynamic factors is paid special attention to. [source] Matching resources to treatment decisions for patients with acute coronary syndromesCLINICAL CARDIOLOGY, Issue S1 2002Robert M. Califf M.D. Abstract Multiple dynamic forces are having an impact on the way cardiovascular disease is treated today and will be in the future. These forces include extended life expectancy, decreased disability, and accelerated improvement in the effectiveness of medical technology. All of these forces will lead to a predictable increase in health care costs. Cardiologists must also be cognizant of the rise in health care consumerism; patients are assuming a larger role in decisions about their medical care and treatment. All of these factors are driving the climate of evidence-based medicine, particularly in the cardiovascular field. Payers and the government are beginning to require the clinical community to define quality. In turn, these third parties are beginning to measure quality as defined by the profession and to hold providers accountable for the quality of what they do. Although the frontier of genetic prediction in therapeutics will serve as an intellectual focus for bringing these issues closer to the forefront in cardiovascular medicine, the fundamental provision of value in health care (high quality at reasonable cost) cannot wait on genomics. Because the amount of evidence in acute coronary syndromes (ACS) exceeds other areas of medicine, therapies for ACS will undergo increasingly intense scrutiny. [source] | ||||||||||