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Realization
Kinds of Realization Selected AbstractsSystem identification applied to long-span cable-supported bridges using seismic recordsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2008Dionysius M. Siringoringo Abstract This paper presents the application of system identification (SI) to long-span cable-supported bridges using seismic records. The SI method is based on the System Realization using Information Matrix (SRIM) that utilizes correlations between base motions and bridge accelerations to identify coefficient matrices of a state-space model. Numerical simulations using a benchmark cable-stayed bridge demonstrate the advantages of this method in dealing with multiple-input multiple-output (MIMO) data from relatively short seismic records. Important issues related to the effects of sensor arrangement, measurement noise, input inclusion, and the types of input with respect to identification results are also investigated. The method is applied to identify modal parameters of the Yokohama Bay Bridge, Rainbow Bridge, and Tsurumi Fairway Bridge using the records from the 2004 Chuetsu-Niigata earthquake. Comparison of modal parameters with the results of ambient vibration tests, forced vibration tests, and analytical models are presented together with discussions regarding the effects of earthquake excitation amplitude on global and local structural modes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Light-Emitting Electrochemical Cells: The Design and Realization of Flexible, Long-Lived Light-Emitting Electrochemical Cells (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Mater. A highly functional flexible light-emitting electrochemical cell during operation is depicted in this cover image. By optimizing the composition of the active material and by employing an appropriate operation protocol, as described by Fang et al. on page 2671, more than one month of uninterrupted operation at significant brightness (>100 cd,2 ) and relatively high power conversion efficiency (2 lm W,1 for orange-red emission) is realized. [source] The Design and Realization of Flexible, Long-Lived Light-Emitting Electrochemical CellsADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Junfeng Fang Abstract Polymer light-emitting electrochemical cells (LECs) offer an attractive opportunity for low-cost production of functional devices in flexible and large-area configurations, but the critical drawback in comparison to competing light-emission technologies is a limited operational lifetime. Here, it is demonstrated that it is possible to improve the lifetime by straightforward and motivated means from a typical value of a few hours to more than one month of uninterrupted operation at significant brightness (>100,cd m,2) and relatively high power conversion efficiency (2 lm W,1 for orange-red emission). Specifically, by optimizing the composition of the active material and by employing an appropriate operational protocol, a desired doping structure is designed and detrimental chemical and electrochemical side reactions are identified and minimized. Moreover, the first functional flexible LEC with a similar promising device performance is demonstrated. [source] The Intermediate Band Solar Cell: Progress Toward the Realization of an Attractive ConceptADVANCED MATERIALS, Issue 2 2010Antonio Luque Abstract The intermediate band (IB) solar cell has been proposed to increase the current of solar cells while at the same time preserving the output voltage in order to produce an efficiency that ideally is above the limit established by Shockley and Queisser in 1961. The concept is described and the present realizations and acquired understanding are explained. Quantum dots are used to make the cells but the efficiencies that have been achieved so far are not yet satisfactory. Possible ways to overcome the issues involved are depicted. Alternatively, and against early predictions, IB alloys have been prepared and cells that undoubtedly display the IB behavior have been fabricated, although their efficiency is still low. Full development of this concept is not trivial but it is expected that once the development of IB solar cells is fully mastered, IB solar cells should be able to operate in tandem in concentrators with very high efficiencies or as thin cells at low cost with efficiencies above the present ones. [source] Realization of contact resolving approximate Riemann solvers for strong shock and expansion flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2010Sung Don Kim Abstract The Harten,Lax,van Leer contact (HLLC) and Roe schemes are good approximate Riemann solvers that have the ability to resolve shock, contact, and rarefaction waves. However, they can produce spurious solutions, called shock instabilities, in the vicinity of strong shock. In strong expansion flows, the Roe scheme can admit nonphysical solutions such as expansion shock, and it sometimes fails. We carefully examined both schemes and propose simple methods to prevent such problems. High-order accuracy is achieved using the weighted average flux (WAF) and MUSCL-Hancock schemes. Using the WAF scheme, the HLLC and Roe schemes can be expressed in similar form. The HLLC and Roe schemes are tested against Quirk's test problems, and shock instability appears in both schemes. To remedy shock instability, we propose a control method of flux difference across the contact and shear waves. To catch shock waves, an appropriate pressure sensing function is defined. Using the proposed method, shock instabilities are successfully controlled. For the Roe scheme, a modified Harten,Hyman entropy fix method using Harten,Lax,van Leer-type switching is suggested. A suitable criterion for switching is established, and the modified Roe scheme works successfully with the suggested method. Copyright © 2009 John Wiley & Sons, Ltd. [source] Realization of log-domain high-order transfer functions using first-order building blocks and complementary operatorsINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 1 2007Costas Psychalinos Abstract High-order log-domain filters could be easily designed by using the functional block diagram (FBD) representation of the corresponding linear prototype and a set of complementary operators. For this purpose, lossy and lossless integrator blocks have been already introduced in the literature. Novel first-order log-domain highpass and allpass filter configurations, which are fully compatible with the already published integrator blocks, are introduced in this paper. These are realized using integration and subtraction blocks or a novel differentiation configuration. As a result, a complete set of first-order building blocks would be available for synthesizing any arbitrary high-order transfer function. In order to verify the correct operation of the proposed structures, the performance of the introduced highpass filters was evaluated through simulation results. In addition, a fifth-order log-domain bandpass filter was designed and simulated using one of the introduced first-order highpass filter configurations. Copyright © 2006 John Wiley & Sons, Ltd. [source] Realization of complete polarization conversion using periodic structure composed of left-handed materialsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2007Weihai Fang Abstract The polarization conversion characteristics of dielectric periodic structure composed of left-handed materials for the case of plane wave oblique incidence are carefully investigated by a method which combines the multimode network theory with the rigorous mode matching method. It is indicated that complete polarization conversion between TE and TM modes can be realized using left-handed gratings. This can hardly achieve in the conventional right-handed gratings. This unique merit of left-handed periodic structure is an important significance for accurate design of new millimeter wave polarization converters. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2862,2864, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22826 [source] The (Multiple) Realization of Psychological and other Properties in the SciencesMIND & LANGUAGE, Issue 2 2009KENNETH AIZAWA To resolve these problems, we focus on concrete examples from the sciences to provide precise accounts of the scientific concepts of ,realization' and ,multiple realization' that have played key roles in recent debates in the philosophy of science and philosophy of psychology. We illustrate the advantages of our view over a prominent rival account (Shapiro, 2000 and 2004) and use our work to rebut recent objections to the long-standing claim that psychological properties are multiply realized. For we use scientific evidence, in combination with our more precise theoretical framework, to show that we have strong reason to believe that psychological properties are indeed multiply realized both at the biochemical and neuronal levels. [source] Realization of extreme light extraction efficiency for moth-eye LEDs on SiC substrate using high-reflection electrodePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010Ryosuke Kawai Abstract The effect of a high-reflection electrode on the opposite side of a moth-eye structure on the performance of a nitride-based blue LED is described. Because of the interference effect enhanced by multiple reflections with a high-reflectance Ag-Pd-Cu alloy (APC) p-contact, light extraction is markedly improved. For the 600-nm-pitch sample, both APC and conventional Ni/Au contacts were used. Although the light output powers of LEDs with APC and Ni/Au p-contacts without moth-eye structure are almost the same, those with a moth-eye structure are markedly increased and differ from each other. For the APC contact, the light output is improved by a factor of 3.4, whereas that with a Ni/Au contact is increased by a factor of 2.2. In addition, we fabricated moth-eye LEDs with pitches of 300 nm, 400 nm, 500 nm and 600 nm by low-energy electron-beam projection lithography. We found that the sample with a pitch of 500 nm has the highest output power, which is 3.7 times higher than that of the reference sample. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Realization of AlGaN/GaN HEMTs on 3C-SiC/Si(111) substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Y. Cordier Abstract Cubic SiC/Si (111) template is an interesting alternative for growing GaN on silicon. As compared with silicon, this substrate allows reducing the stress in GaN films due to both lower lattice and thermal expansion coefficient mismatch, and can provide better heat dissipation. In this work, we first developed the epitaxial growth of 3C-SiC films on 50 mm Si(111) substrates using chemical vapor deposition. AlGaN/GaN high electron mobility transistors were grown by molecular beam epitaxy on these films. Both the structural quality and the behavior of transistors realized on these structures show the feasibility of this approach. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Tube-in-Tube and Wire-in-Tube Nano Building Blocks: Towards the Realization of Multifunctional Nanoelectronic Devices,ANGEWANDTE CHEMIE, Issue 46 2009Ben Ishai, Moshit Die Einführung zusätzlicher Funktionalität in Nanoröhren durch kontrollierte Synthese kann neuartige Architekturen und verbesserte (opto)elektronische Bauelemente ermöglichen. Die Zusammensetzung jeder Wand in hohlen kristallinen Si-Nanoröhren (Röhre-in-Röhre- und Draht-in-Röhre-Strukturen) lässt sich unabhängig einstellen. Zudem lassen sich die Abstände zwischen den Wänden und die Wanddicken steuern (Bild: dreiwandige Nanoröhre und zugehörige TEM-Bilder). [source] Optimal availability and security for IMS-based VoIP networksBELL LABS TECHNICAL JOURNAL, Issue 3 2006Himanshu Pant Consumers are continuously looking for ways of improving their productivity, simplifying their tasks, and streamlining communications both domestically and globally. This has resulted in the need to support different applications and thus the ongoing process of migrating many network services from traditional circuit-switched networks to Internet Protocol (IP) to converged networks. The circuit-switched public switched telephone network (PSTN) was a closed network where cyber-security threats were not amajor issue. With the advent of converged networks and IP-based services, service providers, government, and enterprises are concerned about the growing security threat. The new networks and equipment will be subject to many types of threats and their vulnerabilities may expose mission critical applications and infrastructure to risk. Realization of these threats can lead to service outage. Today's communications service provider must decide how to treat the effects of security breaches so as to minimize service downtime. This paper highlights amethodology, with examples to identify the effect of security-related failures and the critical design factors to be considered when modeling service reliability. The ITU-T X.805 standard (now also ISO standard 18028-2), based on the Bell Labs security model, is used to evaluate potential high impact threats and vulnerabilities. The analysis uses the Bell Labs domain technique known as security domain evaluation. One of the critical outputs provides a prioritized understanding of the threats the network is exposed to and the vulnerabilities in the security architecture. The next step in themethodology includes incorporating the threats (vulnerabilities) identified in a reliability model and quantifying the corresponding service degradation. In this paper, these concepts are applied to IP Multimedia Subsystem (IMS)-based VoIP (Voice over IP) networks. Using reliability metrics, our analysis shows that reliability models are optimistic if we do not consider security. We demonstrate how reliability models can be enhanced to take security issues into account and that the X.805 standard can be used to identify the security threats. Finally, the model shows themitigation in downtime by including intrusion-tolerance features in the product and network design. Consideration of security-caused downtimewill lead to increased focus on preventing security vulnerabilities that can lead to service outages and also allow service providers to save on maintenance costs. © 2006 Lucent Technologies Inc. [source] Image-guided surgery of liver metastases by three-dimensional ultrasound-based optoelectronic navigationBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 7 2007S. Beller Background: Vessel-oriented surgery and tumour-free resection margins are essential for resection of liver metastases to preserve liver parenchyma and improve oncological outcome. Preoperative three-dimensional models reconstructed from imaging data could facilitate surgical planning with the use of navigation technology. Methods: Thirty-three patients with central and/or impalpable liver metastases were scheduled for navigated hepatic resection. Intraoperative three-dimensional ultrasonography and an infrared-based optical tracking system were used for data registration and image-guided surgery. Postoperative three-dimensional data were compared with the preoperative virtual surgical plan to assess the accuracy of navigation, and clinical results were compared with those of a matched control group of 32 patients. Results: Navigation was successful in 32 of 33 patients. Realization of the preoperative plan and R0 resection was achieved in 30 of these 32 patients. The median discrepancy between the planned and actual vascular dissection level was 6 (range 0,11) mm. There was a reduced rate of R1 resection in the navigated group compared with the control group (two versus four patients), and more parenchyma was preserved. Conclusion: Three-dimensional ultrasound-based optoelectronic navigation technology improves intraoperative orientation and enables parenchyma-preserving surgery with high precision. Copyright © 2007 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] Realization of the Synthesis of ,,,-Disubstituted Carbamylacetates and Cyanoacetates by Either Enzymatic or Chemical Functional Group Transformation, Depending upon the Substrate Specificity of Rhodococcus Amidase.CHEMINFORM, Issue 9 2005Masahiro Yokoyama Abstract For Abstract see ChemInform Abstract in Full Text. [source] On the Existence of Finite-Dimensional Realizations for Nonlinear Forward Rate ModelsMATHEMATICAL FINANCE, Issue 2 2001Tomas Björk We consider interest rate models of the Heath,Jarrow,Morton type, where the forward rates are driven by a multidimensional Wiener process, and where the volatility is allowed to be an arbitrary smooth functional of the present forward rate curve. Using ideas from differential geometry as well as from systems and control theory, we investigate when the forward rate process can be realized by a finite-dimensional Markovian state space model, and we give general necessary and sufficient conditions, in terms of the volatility structure, for the existence of a finite-dimensional realization. A number of concrete applications are given, and all previously known realization results (as far as existence is concerned) for Wiener driven models are included and extended. As a special case we give a general and easily applicable necessary and sufficient condition for when the induced short rate is a Markov process. In particular we give a short proof of a result by Jeffrey showing that the only forward rate models with short rate dependent volatility structures which generically possess a short rate realization are the affine ones. These models are thus the only generic short rate models from a forward rate point of view. [source] Design and realization of the cooperative work system based on equipments sharingCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 4 2009Bo Yan Abstract With analysis on the necessity and functions of the equipments sharing platform and the cooperative work system for colleges and universities, this paper designs the cooperative work system to provide cooperative support for resource query and reservation. The system classifies users' resource application roles, divides users' application information into different cooperative grades, and provides a basis for users' cooperative work. Functions, authorization, page flow, operating methods, and relevant database table of cooperative roles are shown in detail. At the same time, the ASP system will be introduced into the system, and a special fee management system will be established for effective management of the system. Functions and page flow of the fee management system are also designed. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 17: 372,378, 2009; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20195 [source] An Ultrasonic Profiling Method for the Inspection of Tubular StructuresCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2007Francisco Gomez These graphs not only show the inner contour of the pipe but also integrate the intensity of the echoes employed to create the profile. The enhanced profile is generated by superimposing the peak intensity from the returning echoes at the calculated x, y, and z coordinates where it reflected from the pipe wall. The proposed method is capable of showing anomalous conditions, inside pipes filled with liquid, with dimensions smaller than the theoretical lateral and axial resolution of the transducer, in contrast to traditional methods where these kinds of defects are not disclosed. The proposed inspection method and its capabilities were validated through the realization of simulations and experiments. The presented approach was particularly developed with the aim of scanning internal sections of pipes filled with liquid using rotary ultrasonic sonars, but it is expected that this research could be expanded to the inspection of other submerged structures, such as water tanks, or pressurized vessels. [source] A quality-of-service-based framework for creating distributed heterogeneous software componentsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 12 2002Rajeev R. Raje Abstract Component-based software development offers a promising solution for taming the complexity found in today's distributed applications. Today's and future distributed software systems will certainly require combining heterogeneous software components that are geographically dispersed. For the successful deployment of such a software system, it is necessary that its realization, based on assembling heterogeneous components, not only meets the functional requirements, but also satisfies the non-functional criteria such as the desired quality of service (QoS). In this paper, a framework based on the notions of a meta-component model, a generative domain model and QoS parameters is described. A formal specification based on two-level grammar is used to represent these notions in a tightly integrated way so that QoS becomes a part of the generative domain model. A simple case study is described in the context of this framework. Copyright © 2002 John Wiley & Sons, Ltd. [source] TRIGGER-POINT MECHANISM AND CONDITIONAL COMMITMENT: IMPLICATIONS FOR ENTRY, COLLUSION, AND WELFARECONTEMPORARY ECONOMIC POLICY, Issue 2 2007LARRY D. QIU When fixed, sunk investment costs are high, firms may not have sufficient incentive to enter the market unless future entry is constrained. In this case, the government faces a dilemma between a full commitment and noncommitment of restricted future entry. A way out is to consider a commitment conditional on the realization of the uncertain parameters, such as the trigger-point mechanism (TPM) that sets conditions on current production level, excess capacity, and demand growth under which future entry will be allowed. This article shows that the TPM facilitates the incumbents' collusion but may improve social welfare under certain circumstances. (JEL L13, L43, L50, H10, H54) [source] Extensions of the 3-Dimensional Plasma Transport Code E3DCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1-3 2004A. Runov Abstract One important aspect of modern fusion research is plasma edge physics. Fluid transport codes extending beyond the standard 2-D code packages like B2-Eirene or UEDGE are under development. A 3-dimensional plasma fluid code, E3D, based upon the Multiple Coordinate System Approach and a Monte Carlo integration procedure has been developed for general magnetic configurations including ergodic regions. These local magnetic coordinates lead to a full metric tensor which accurately accounts for all transport terms in the equations. Here, we discuss new computational aspects of the realization of the algorithm. The main limitation to the Monte Carlo code efficiency comes from the restriction on the parallel jump of advancing test particles which must be small compared to the gradient length of the diffusion coefficient. In our problems, the parallel diffusion coefficient depends on both plasma and magnetic field parameters. Usually, the second dependence is much more critical. In order to allow long parallel jumps, this dependence can be eliminated in two steps: first, the longitudinal coordinate x3 of local magnetic coordinates is modified in such a way that in the new coordinate system the metric determinant and contra-variant components of the magnetic field scale along the magnetic field with powers of the magnetic field module (like in Boozer flux coordinates). Second, specific weights of the test particles are introduced. As a result of increased parallel jump length, the efficiency of the code is about two orders of magnitude better. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effective radial Liapunov exponent for the radial diffusion of test electronsCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3-4 2003A. Maluckov Abstract The radial diffusion of test electrons in the bounded magnetic field region with irregularities is a realization of the magnetic (deterministic) and collisional (statistical) stochasticities. To clarify the development of stochasticities the effective radial Liapunov exponent Ler, the number of the electron trajectories (magnetic field lines) with positive radial Liapunov exponent Np, the distribution of the radial Liapunov exponent, Kolmogorov entropy and 3D Liapunov exponent are calculated numerically. In the absence of collisions the overlapping among magnetic islands (generation of the global stochasticity) is indicated by the qualitative change from negative to positive Ler in the long time limit. The fact that Np < N, where N is the number of test electrons, is the sign of sticking to the magnetic field structures. From the viewpoint of the radial Liapunov exponents both stochasticities manifest similarly. It is shown that the distribution of the radial Liapunov exponents is not the elementary one, except in the region of the extremely frequent collisions and partially destroyed magnetic field. Transition of the radial diffusion from the strange to the standard diffusion [1] is related with neglecting sticking of the electrons to the magnetic field structures by enough frequent collisions. [source] The stratum corneum: structure and function in health and diseaseDERMATOLOGIC THERAPY, Issue 2004Clive R. Harding ABSTRACT:, Our understanding of the formation, structure, composition, and maturation of the stratum corneum (SC) has progressed enormously over the past 30 years. Today, there is a growing realization that this structure, while faithfully providing a truly magnificent barrier to water loss, is a unique, intricate biosensor that responds to environmental challenges and surface trauma by initiating a series of biologic processes which rapidly seek to repair the damage and restore barrier homeostasis. The detailed ultrastructural, biochemical, and molecular dissection of the classic "bricks and mortar" model of the SC has provided insights into the basis of dry, scaly skin disorders that range from the cosmetic problems of winter xerosis to severe conditions such as psoriasis. With this knowledge comes the promise of increasingly functional topical therapies. [source] Dorothy Hodgkin Lecture 2008 Gastric inhibitory polypeptide (GIP) revisited: a new therapeutic target for obesity,diabetes?DIABETIC MEDICINE, Issue 7 2008P. R. Flatt Abstract There is increasing realization that gastric inhibitory polypeptide (GIP) has actions outside of the pancreas and gastrointestinal tract. Most significant is the presence of functional GIP receptors on adipocytes and the appreciation that GIP, secreted strongly in response to fat ingestion, plays a role in the translation of excessive amounts of dietary fat into adipocyte tissue stores. Such effects open up the possibility of exploiting GIP receptor antagonism for the treatment of obesity and insulin resistance. This is borne out by studies in high-fat-fed mice or ob/ob mice with either genetic knockout of GIP receptor or chemical ablation of GIP action using the GIP receptor antagonist, (Pro3)GIP. By causing preferential oxidation of fat, blockade of GIP signalling clears triglyceride deposits from liver and muscle, thereby respectively restoring mechanisms for suppression of hepatic glucose output and cellular glucose uptake. Further studies are needed to determine the applicability of this research to human obesity,diabetes. However, proof of concept is provided by emerging evidence that rapid cure of diabetes in grossly obese subjects undergoing Roux-en-Y bypass surgery is mediated in part by surgical bypass of GIP-secreting K-cells in the upper small intestine. [source] Neuronal plasticity: implications in epilepsy progression and managementDRUG DEVELOPMENT RESEARCH, Issue 8 2007Sherifa A. HamedArticle first published online: 12 FEB 200 Abstract Epilepsy is a common neurological disease. A growing number of research studies provide evidence regarding the progressive neuronal damage induced by prolonged seizures or status epilepticus (SE), as well as recurrent brief seizures. Importantly, seizure is only one aspect of epilepsy. However, cognitive and behavioral deficits induced by progressive seizures or antiepileptic treatment can be detrimental to individual function. The neurobiology of epilepsy is poorly understood involving complex cellular and molecular mechanisms. The brain undergoes changes in its basic structure and function, e.g., neural plasticity with an increased susceptibility in neuronal synchronization and network circuit alterations. Some of these changes are transient, while others are permanent with an involvement of both glutamatergic and ,-aminobutyric acid (GABA)ergic systems. Recent data suggest that impaired neuronal plasticity may underlie the cognitive impairment and behavioral changes associated with epilepsy. Many neurologists recognize that the prevention or suppression of seizures by the use of antiepileptic drugs (AEDs) alone is insufficient without clear predictions of disease outcome. Hence, it is important to understand the molecular mechanisms underlying epileptogenesis because this may allow the development of innovative strategies to prevent or cure this condition. In addition, this realization would have significant impact in reducing the long-term adverse consequences of the disease, including neurocognitive and behavioral adverse effects. Drug Dev Res 68:498,511, 2007. © 2008 Wiley-Liss, Inc. [source] Dimensional analysis of the earthquake-induced pounding between adjacent structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2009Elias Dimitrakopoulos Abstract In this paper the dynamic response of two and three pounding oscillators subjected to pulse-type excitations is revisited with dimensional analysis. Using Buckingham's ,-theorem the number of variables that govern the response of the system is reduced by three. When the response is presented in the dimensionless ,-terms remarkable order emerges. It is shown that regardless of the acceleration level and duration of the pulse all response spectra become self-similar and follow a single master curve. This is true despite the realization of finite duration contacts with increasing durations as the excitation level increases. All physically realizable contacts (impacts, continuous contacts, and detachments) are captured via a linear complementarity approach. The study confirms the existence of three spectral regions. The response of the most flexible among the two oscillators amplifies in the low range of the frequency spectrum (flexible structures); whereas, the response of the most stiff among the two oscillators amplifies at the upper range of the frequency spectrum (stiff structures). Most importantly, the study shows that pounding structures such as colliding buildings or interacting bridge segments may be most vulnerable for excitations with frequencies very different from their natural eigenfrequencies. Finally, by applying the concept of intermediate asymptotics, the study unveils that the dimensionless response of two pounding oscillators follows a scaling law with respect to the mass ratio, or in mathematical terms, that the response exhibits an incomplete self-similarity or self-similarity of the second kind with respect to the mass ratio. Copyright © 2008 John Wiley & Sons, Ltd. [source] Oxidative stress as a mediator of life history trade-offs: mechanisms, measurements and interpretationECOLOGY LETTERS, Issue 1 2009Pat Monaghan Abstract The concept of trade-offs is central to our understanding of life-history evolution. The underlying mechanisms, however, have been little studied. Oxidative stress results from a mismatch between the production of damaging reactive oxygen species (ROS) and the organism's capacity to mitigate their damaging effects. Managing oxidative stress is likely to be a major determinant of life histories, as virtually all activities generate ROS. There is a recent burgeoning of interest in how oxidative stress is related to different components of animal performance. The emphasis to date has been on immediate or short-term effects, but there is an increasing realization that oxidative stress will influence life histories over longer time scales. The concept of oxidative stress is currently used somewhat loosely by many ecologists, and the erroneous assumption often made that dietary antioxidants are necessarily the major line of defence against ROS-induced damage. We summarize current knowledge on how oxidative stress occurs and the different methods for measuring it, and highlight where ecologists can be too simplistic in their approach. We critically review the potential role of oxidative stress in mediating life-history trade-offs, and present a framework for formulating appropriate hypotheses and guiding experimental design. We indicate throughout potentially fruitful areas for further research. [source] The Limits of ex post ImplementationECONOMETRICA, Issue 3 2006Philippe Jehiel The sensitivity of Bayesian implementation to agents' beliefs about others suggests the use of more robust notions of implementation such as ex post implementation, which requires that each agent's strategy be optimal for every possible realization of the types of other agents. We show that the only deterministic social choice functions that are ex post implementable in generic mechanism design frameworks with multidimensional signals, interdependent valuations, and transferable utilities are constant functions. In other words, deterministic ex post implementation requires that the same alternative must be chosen irrespective of agents' signals. The proof shows that ex post implementability of a nontrivial deterministic social choice function implies that certain rates of information substitution coincide for all agents. This condition amounts to a system of differential equations that are not satisfied by generic valuation functions. [source] The Effects of a Baby Boom on Stock Prices and Capital Accumulation in the Presence of Social SecurityECONOMETRICA, Issue 2 2003Andrew B. Abel Is the stock market boom a result of the baby boom? This paper develops an overlapping generations model in which a baby boom is modeled as a high realization of a random birth rate, and the price of capital is determined endogenously by a convex cost of adjustment. A baby boom increases national saving and investment and thus causes an increase in the price of capital. The price of capital is mean,reverting so the initial increase in the price of capital is followed by a decrease. Social Security can potentially affect national saving and investment, though in the long run, it does not affect the price of capital. [source] A Parametric Approach to Flexible Nonlinear InferenceECONOMETRICA, Issue 3 2001James D. Hamilton This paper proposes a new framework for determining whether a given relationship is nonlinear, what the nonlinearity looks like, and whether it is adequately described by a particular parametric model. The paper studies a regression or forecasting model of the form yt=,(xt)+,t where the functional form of ,(,) is unknown. We propose viewing ,(,) itself as the outcome of a random process. The paper introduces a new stationary random field m(,) that generalizes finite-differenced Brownian motion to a vector field and whose realizations could represent a broad class of possible forms for ,(,). We view the parameters that characterize the relation between a given realization of m(,) and the particular value of ,(,) for a given sample as population parameters to be estimated by maximum likelihood or Bayesian methods. We show that the resulting inference about the functional relation also yields consistent estimates for a broad class of deterministic functions ,(,). The paper further develops a new test of the null hypothesis of linearity based on the Lagrange multiplier principle and small-sample confidence intervals based on numerical Bayesian methods. An empirical application suggests that properly accounting for the nonlinearity of the inflation-unemployment trade-off may explain the previously reported uneven empirical success of the Phillips Curve. [source] Diagnostic Implications of Uric Acid in Electroanalytical MeasurementsELECTROANALYSIS, Issue 14 2005Abstract Urate has a long history in clinical analysis and has served as an important diagnostic in a number of contexts. The increasing interest in metabolic syndrome has led to urate being used in combination with a number of other biomarkers in the assessment of cardiovascular risk. The traditional view of urate as principally an interferent in electrochemical measurement is now gradually being replaced with the realization that its measurement could serve as an invaluable secondary (if not primary) marker when monitoring conditions such as diabetes and heart disease. Rather than attempting to wholly exclude urate electrochemistry, many strategies are being developed that can integrate the urate signal within the device architecture such that a range of biomarkers can be sequentially assessed. The present review has sought to rationalize the clinical importance that urate measurements could hold in future diagnostic applications , particularly within near patient testing contexts. The technologies harnessed for its detection and also those previously employed for its removal are reviewed with the aim of highlighting how the seemingly contrasting approaches are evolving to aid the development of new sensing devices for clinical analysis. 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