Littérature scientifique sur le sujet « Kinematic source parameters »

SUMMARY The retrieval of earthquake finite-fault kinematic parameters after the occurrence of an earthquake is a crucial task in observational seismology. Routinely used source inversion techniques are challenged by limited data coverage and computational effort, and are subject to a variety of assumptions and constraints that restrict the range of possible solutions. Back-projection (BP) imaging techniques do not need prior knowledge of the rupture extent and propagation, and can track the high-frequency (HF) radiation emitted during the rupture process. While classic source inversion methods work at lower frequencies and return an image of the slip over the fault, the BP method highlights fault areas radiating HF seismic energy. Patterns in the HF radiation are attributable to the spatial and temporal complexity of the rupture process (e.g. slip heterogeneities, changes in rupture speed). However, the quantitative link between the BP image of an earthquake and its rupture kinematics remains unclear. Our work aims at reducing the gap between the theoretical studies on the generation of HF radiation due to earthquake complexity and the observation of HF emissions in BP images. To do so, we proceed in two stages, in each case analysing synthetic rupture scenarios where the rupture process is fully known. We first investigate the influence that spatial heterogeneities in slip and rupture velocity have on the rupture process and its radiated wave field using the BP technique. We simulate two different rupture processes using a 1-D line source model: a homogeneous process, where the kinematic parameters are constant along the line, and a heterogeneous process, where we introduce a central segment along the line that has a step change in kinematics. For each rupture model, we calculate synthetic seismograms at three teleseismic arrays and apply the BP technique to reveal how HF emissions are influenced by the three kinematic parameters controlling the synthetic model: the rise time, final slip and rupture velocity. Our results show that the HF peaks retrieved from BP analysis are better associated with space–time heterogeneities of slip acceleration. We then build on these findings by testing whether one can retrieve the kinematic rupture parameters along the fault using information from the BP image alone. We apply a machine learning, convolutional neural network (CNN) approach to the BP images of a large set of simulated 1-D rupture processes to assess the ability of the network to retrieve, from the progression of HF emissions in space and time, the kinematic parameters of the rupture. These rupture simulations include along-strike heterogeneities whose size is variable and within which the parameters of rise-time, final slip and rupture velocity change from the surrounding rupture. We show that the CNN trained on 40 000 pairs of BP images and kinematic parameters returns excellent predictions of the rise time and the rupture velocity along the fault, as well as good predictions of the central location and length of the heterogeneous segment. Our results also show that the network is insensitive towards the final slip value, as expected from theoretical results.

Since robots began to inter the medical fields, more research efforts and more attention have been given to this kind of robots. In this paper six degrees of freedom surgical robot was studied. The Denavit-Hartenberg parameters of the robot have been computed and 3D model has been built by using open source robotics toolbox. The paper also discussed a closed form solution for the inverse kinematics problem by using inverse kinematic decoupling method.

Maintaining minimal levels of geometric error in the finished workpiece is of increasing importance in the modern production environment; there is considerable research on the identification, verification and calibration of machine tool kinematic error, and the development of Postprocessor implementations to generate NC-code optimised for machining accuracy. The choice of multi-axis positioning function at the controller, however, is an often-overlooked potential source of kinematic error which can be responsible for costly mistakes in the production environment. This paper presents an investigation into how mis-management of the positional error parameters that define the rotary-axes’ pivot point can lead to unintended variations in multi-axis positioning. Four approaches for kinematic positioning on a Fanuc-based controller are considered, which reference two separate parameter locations to define the pivot point – managing the kinematics within the Postprocessor itself, full five-axis positioning with a fixture offset, full five-axis with rotation tool centre point control and 3+2-axis with a tilted workplane. Error vectors across four sets of rotary-axis indexations are simulated based on the theoretical kinematic model, to highlight the expected differences in geometric error attributable to mismatched pivot point parameters. Finally, the simulation results are verified experimentally, demonstrating the importance of maintaining a consistent approach in both programming and operation environments.

Objective: In this article, we present the conceptual development of a robotics platform, called ALICE (Assistive Lower Limb Controlled Exoskeleton), for kinetic and kinematic gait characterization. The ALICE platform includes a robotics wearable exoskeleton and an on-board muscle driven simulator to estimate the user’s kinetic parameters. Background: Even when the kinematics patterns of the human gait are well studied and reported in the literature, there exists a considerable intra-subject variability in the kinetics of the movements. ALICE aims to be an advanced mechanical sensor that allows us to compute real-time information of both kinetic and kinematic data, opening up a new personalized rehabilitation concept. Methodology: We developed a full muscle driven simulator in an open source environment and validated it with real gait data obtained from patients diagnosed with multiple sclerosis. After that, we designed, modeled, and controlled a 6 DoF lower limb exoskeleton with inertial measurement units and a position/velocity sensor in each actuator. Significance: This novel concept aims to become a tool for improving the diagnosis of pathological gait and to design personalized robotics rehabilitation therapies. Conclusion: ALICE is the first robotics platform automatically adapted to the kinetic and kinematic gait parameters of each patient.

Slender-bodied organisms swimming with whole-body undulations exhibit what appears to be a high degree of kinematic parameter conservation, which is independent of body size. However, organisms of very different sizes swim in fundamentally different physical realms, owing to the relative scaling of viscous and inertial fluid stresses as a function of size and speed. In light of the size-dependent fluid forces, the kinematic constancy suggests three hypotheses: (1) swimming organisms adopt a single "ideal" swimming mode requiring the modification of muscle forces or motor patterns through ontogeny, (2) swimming kinematics are determined predominantly by the passive mechanical interaction of the body and the fluid, resulting in a single swimming mode independent of absolute body size, or (3) while undulatory swimming kinematics may be similar between organisms, there are important size-dependent kinematic differences. In this study, I address this issue by examining the swimming kinematics and dynamics of the medicinal leech Hirudo medicinalis L. as a function of body size. Over a 5-fold increase in body length, the relative amplitude of body undulations during swimming did not change; however, swimming speed, propulsive wave speed, and propulsive wave frequency all decreased, while propulsive wave number increased slightly, strongly supporting hypothesis 2. To determine the source of the observed size-dependent swimming kinematics, I manipulated the dynamic viscosity of the organism's fluid environment to alter the constraints placed on swimming behavior by the physical surroundings. In the elevated-viscosity treatment, all kinematic parameters changed in the opposite direction to that predicted by hypothesis 2, rejecting both the idea that swimming kinematics are simply determined by passive mechanical interactions and that leeches have a target swimming mode under active control.

The characteristics of the source zone of the debris flow watershed is one of the most significant factors governing debris flows initiation, at the same time it also plays a crucial role for disaster risk evaluation. With the aim of obtaining the basic characteristics of the source zone and computing the kinematic parameters, field investigations were conducted comprehensively, combining with the results of remote sensing interpretation, the origin and distribution regulations can be identified, and total amount of the loose solid materials can be determined, the corresponding value is 4.91×106 m3. Using the collected data of this watershed, and with the help of previous theoretical models, the kinematic parameters under different rainfall frequencies are calculated, which including debris flow discharge, total volume of one-time debris flow and the total volume of solid materials. Such parameters are helpful and essential for debris flow disasters evaluation, prevention and designing mitigation measures.

Ricostruzione del processo di rottura cosismico su faglia finita attraverso l’inversione congiunta di dati sismologici e geodetici. Implementazione e validazione di una nuova tecnica di inversione non lineare, di tipo global search, per l’inversione congiunta di dati GPS e dati strong motion. Analisi statistica dell’ensemble dei modelli di rottura esplorati dall’algoritmo di inversione. Analisi sulla consistenza dinamica dei modelli cinematici di rottura. Applicazioni: (1) Test Sintetici atti a validare la capacità di risoluzione e robustezza della tecnica sviluppata; (2) Analisi del terremoto di Tottori (2000); (3) Analisi del terremoto di Niigata (2007); (4) Determinazione di scenari di scuotimento in aree di interesse prioritario e strategico (terremoto dell’Irpinia, 1980).
Istituto Nazionale di Geofisica e Vulcanologia
Unpublished
3.1. Fisica dei terremoti
open

The main milestones of the formation and development of astronomical science in Kharkiv during 1883–1945 are reconstructed on the example of the activities of the astronomical observatory of Kharkiv University. During this period, the outstanding worldview science in Kharkiv has achieved significant success: the works of Kharkiv astronomers have received world recognition; a well-known scientific planetary school has been established at the Observatory; the scientific community highly appreciated the research on the physics and chemistry of the Moon, the giant and small planets of the Solar System. The primary goal of the research is to inscribe the history of the university Observatory into the European and world context. Its purpose is to summarize the results of a comprehensive historical ad scientific study of the development of astronomical research in Kharkiv at the end of the 19th century – the first half of the 20th century and identification of ways of further scientific research. The completed research, which continues the problems of works devoted to the study of the history of astronomical science in Ukraine, focuses on expanding the well-known source base by attracting new retro-information resources. In particular, the monograph used a significant array of archival primary sources from almost twenty archival and library institutions of different countries. Most of them were introduced into scientific circulation for the first time, which allowed to determine and specify the sequence of stages of development of astronomical science in Kharkiv during the research period, to clarify and identify the little-known circumstances of the observatory life. The methodological basis of the study is the principles of historism, objectivity and a systematic approach to studying the problem. To solve specific problematic tasks in the monograph, general scientific and specially historical methods were used which allowed to study, analyze and summarize the presented factual material in a complex manner. The main sections of the monograph represent the dynamics of replenishment of the instrumental base of the university observatory, the chronology of the construction of the observatory complex of buildings at the location of the modern Scientific Research Institute of Astronomy of the V. N. Karazin Kharkiv National University. According to the author’s periodization, the stages of formation of subjects and directions of scientific work of university astronomers have been analyzed, including: seismic observations with the help of horizontal Rebeur-Paschwitz pendulums, research of the activity of the Sun, astrometric observations on the Repsold meridian circle of for the purpose of compiling a catalog of zodiac stars, studying lunar eclipses and meteor showers. The participation of university astronomers in the creation of the plan of the city of Kharkiv and its connection with the general network of precise geometric leveling of the Military Topographic Department of the General Staff; the organization of observations by an expedition of Kharkiv astronomers of the total Solar eclipse of 1914 in Henichesk; the creation of the School-workshop of precision mechanics at the Faculty of Physics and Mathematics of Kharkiv University were considered; information on the participation of Kharkiv astronomers in the events of the civil war during the Ukrainian Revolution was documented. The scientific research activity of Kharkiv astronomers during 1920-1930-s which was devoted to carrying out important astrometric works on meridian observations of star declinations by absolute methods and observations of Kopf-Rentz stars according to the programs of the International Astronomical Union; the initiation of the creation of the Catalog of faint stars; research in astrophysics aimed at studying the physical conditions on the Moon and the Sun, planets and the interstellar environment; performing long series of spectrophotometric observations of the Moon, Jupiter, Mars and Saturn under different conditions of observation; study of the kinematics of stellar systems of different order, the physical parameters and evolution of stars, the morphology of the Galaxy, the nature of the stellar subsurfaces and atmospheres, dust and gas nebulae, new stars and the variability of stars have been considered; the directions of solid works carried out in the field of celestial mechanics, devoted to the dynamics of the minor planets of the Jupiter group, the definition and improvement of the orbits of minor planets have been clarified. The development of amateur astronomy in Kharkiv, in particular, the functioning of circles and societies that directed their activities to the dissemination of astronomical knowledge, was highlighted; the participation of their representatives in astronomical observations at the Kharkiv Astronomical Observatory was emphasized. Reconstructed the development of historical events in the 1930s related to the involvement of Soviet and Western astronomers in the processes of political confrontation between the USSR and the Western world; investigated the course of circumstances that prevented the implementation of the project of creating a new modern astronomical center of national importance – the central Ukrainian observatory in Kharkiv; the participation of an expedition of Kharkiv astronomers in the observation of the «great Soviet eclipse» – the total solar eclipse of 1936 – in the North Caucasus is highlighted; established the facts of political «purges» and repressions by the People’s Commissariat for Internal Affairs ( the NKVD) in the Kharkiv Astronomical Observatory. The activity of the Kharkiv Astronomical Observatory has been documented and authentic biographical information about its representatives during the Nazi occupation of 1941–1943, the period of the German-Soviet war, has been presented; the unpopular facts of the forced collaboration of some scientists are highlighted; the process of recovery and reconstruction of the Kharkiv Astronomical Observatory after the liberation of the city is characterized. With the aim of researching the personal history of Kharkiv astronomy of the studied period, the monograph presents the results of a historical and biographical study of facts of life and scientific heritage of scientists who fully devoted themselves to Science, laid the foundations for the future development of many directions of modern astronomical research, made a significant contribution to the treasury of the national and European astronomical science, whose activities were connected with the Kharkiv Astronomical Observatory, in particular: Grigory Levytsky, Ludwig Struve, Mykola Evdokymov, Otto Struve, Mykola Barabashov, Boris Gerasimovich, Vasil Fesenkov, Oleksiy Razdolsky, Boris Ostashchenko-Kudryavtsev, Nicholas Bobrovnikov, Paraskovia Parkhomenko, Mstislav Savron, Boris Semeykin, Kostyantyn Savchenko and others (25 biographical essays are presented). A significant part of the mentioned factual material was also introduced into scientific circulation for the first time. A separate section of the monograph provides chronologically structured information that reflects the sequence of research work of the Kharkiv Astronomical Observatory employees during the period under study: from astrometric observations of stars and seismic research to spectrohelioscopic and spectroheliographic observations of the Sun and the initiation of the Kharkiv school of planetary science. It is assumed that the materials of the monograph will be used in research work devoted to the study of the process of institutionalization of astronomical research in Kharkiv at the end of the 19th century – the first half of the 20th century.

Biodiesel mainly comes from edible oil, and there is little research on its yield from non-edible sources with low-cost oil. It is paramount to investigate the non-edible oil resources which may lead to advance the commercial feasibility of biodiesel and cost effectiveness as well as resolve the food issues. This chapter describes four novel non-edible seed oil sources comprising Koelreuteria paniculata, Rhus typhina, Acacia farnesiana and Albizzia julibrissin for biodiesel production. We aimed to optimize different reaction parameters for oil extraction, alkali-catalyzed transesterification process for maximal biodiesel production and finally evaluate its compatibility with mineral diesel. The optimization factors in transesterification included the molar ratio of methanol to oil, reaction time, stirring intensity, catalyst concentration and temperature. Two methods have been described including Soxhlet and mechanical for extraction of seed oil. The synthesized esters were evaluated and characterized through the nuclear magnetic resonance (NMR; 1H and 13C), Fourier transform infrared (FT-IR) and gas chromatography–mass spectrometry (GC–MS) and the total conversion of crude oil to fatty acid methyl esters (FAMEs) were established. The inductively coupled plasma-optical emission spectrometry (ICP-OES) and Elemental Analyzer (EA) were used for evaluation of elemental concentration. The physico-chemical characterizations of the biodiesel, i.e., flash point, pour point, cloud point, and density were within the American Society for Testing and Materials (ASTM; D6751) and European Standards ((EN14214). Koelreuteria paniculata produced highest biodiesel oil content by Soxhlet extraction (28–30%) followed by the Albizzia julibrissin (19–24%), Acacia farnesiana (23%), Rhus typhina (20–22%). The density ranged from 0.83–0.87 @ 15°C (g/cm3) and the kinematic viscosity ranged from 3.75–6.3 (mm2/s) among all the plant sources. Koelreuteria paniculata had highest Na (5456.2), Cr (1246.8), Ni (658.36), and Al (346.87) elemental concentrations (μg/g) than other plant sources. The elemental percent of C, H, N, and O of biodiesel ranged from 72.54–76.86, 11.25–13.34, 1.97–2.73, and 9.86–12, respectively. In conclusion, these non-edible plant seeds offer a cheap source of renewable energy and can be easily grown on barren and wastelands and contribute to efficient biodiesel production to mitigate the energy crisis.

Developing controllers for powered prostheses is a daunting task that requires involvement from clinicians, patients and robotics experts. Difficulties arise for tuning prosthetic devices that perform in multiple conditions and provide more functionality to the user. For this reason, we propose the implementation of a simulation framework based on the open-source 3D simulation environment Gazebo, to reduce the burden of experimentation and aid in the early stages of development. In this study, we present a minimalist plugin for the simulator that allows the interfacing of a virtual model with the native prosthesis controller and renders the finding of impedance parameters as a pattern search problem. To demonstrate the functionality of this approach, we used the framework to obtain the parameters that offer the most similar joint trajectory to the respective biological counterpart during swing phase for ground level walking. The optimization results are compared against the response of a physical 2DOF knee-ankle prosthesis operating under the optimized parameters, showing congruence to our model-based results. We found that a simulation-based solution is capable of finding parameters that create an emerging behavior that approximates to the kinematic trajectory goals within a tolerance (mean absolute error ∼10%). This provides an appropriate method for development and evaluation of impedance-based controllers before deployment to the physical device.

British Energy (BE) has funded a large work programme to assess the possible impact of primary water stress corrosion cracking on dissimilar metal welds in the primary circuit of the Sizewell ‘B’ pressurised water reactor. This effort has included the design and manufacture of representative pressuriser safety/relief valve nozzle welds both with and without a full structural weld overlay, multiple residual stress measurements on both mock-ups using the deep hole and incremental deep hole methods, and a number of finite element weld residual stress simulations of both the mock-ups and equivalent plant welds. Three organisations have performed simulations of the safety/relief valve nozzle configuration: Westinghouse, Engineering Mechanics Corporation of Columbus (EMC2) and the Australian Nuclear Science and Technology Organisation (ANSTO). The simulations employ different welding heat input idealisations, make different assumptions about manufacturing history, and use a variety of different material constitutive models, ranging from simple bilinear kinematic hardening to a full mixed isotropic-kinematic formulation. The availability of both high quality measurements from well characterised mock-ups, and a large matrix of simulations, offers the opportunity for a “mini-round-robin” examining both the accuracy and key solution variables of dissimilar metal weld finite element simulations. This paper is one of a series at this conference that examine various aspects of the BE work programme. It describes the detailed finite element simulation of the mock-ups performed by BE and ANSTO. This makes use of the extensive mock-up manufacturing records to perform a detailed pass-bypass simulation of the entire manufacturing process from initial nozzle buttering through to completion of the safe end to pipe weld. The thermal simulation makes use of a dedicated welding heat source modelling tool to derive Gaussian volumetric heat source parameters from the welding records, and the mechanical simulation employs isotropic, kinematic and mixed isotropic-kinematic material constitutive models. Additional sensitivity studies examine sensitivity to manufacturing history and physical properties such as expansion coefficient mismatch.

A single weld bead deposited on a flat plate is a deceptively simple problem that is in practice a challenge for both measurement and prediction of weld residual stresses. Task Group 1 of the NeT collaborative network has examined this problem in a two-phase programme extending from 2002 to 2008. Ten independent sets of residual stress measurements have been reported using diverse techniques, and over forty finite element simulations have been performed. This paper reviews Phase 2 of the Task Group 1 round robin. Here, the finite element simulations all made use of optimised thermal solutions, in which the global welding parameters, including efficiency, were fixed, and only the detailed heat source geometry was varied. These resulted in accurate far field welding temperature distributions, with significant variability only close to the weld bead itself. The subsequent mechanical analyses made use of kinematic, isotropic, and mixed isotropic-kinematic material constitutive models, and made a variety of assumptions about the introduction of weld filler material to the structure and the handling of high temperature inelastic strains. The large database of measurements allowed the derivation of statistical best estimates using a Bayesian “duff data” approach, and these best estimates were compared with the predictions to establish the most accurate material constitutive models. The most accurate predictions of residual stress were made using non-linear kinematic or mixed isotropic-kinematic constitutive models. The methods used to handle high-temperature inelastic strains influenced the predicted stresses only in regions where very high temperatures were predicted during welding. The results emphasise the importance and value of both well-characterised benchmark problems and international collaboration in the development of technologies to both measure and predict weld residual stresses.

Low-trauma hip fracture, usually caused by fall from standing height, has become a main source of morbidity and mortality among the elderly. However, the hip fracture risk is subject-dependent as it is related to the subject’s anthropometric parameters, the kinematic/kinetic variables in fall, and the hip anatomy. A compound fracture risk indicator is proposed in this study to define the correlation between the hip fracture risk and subject’s parameters such as anthropometric parameters, bone mineral density (BMD), height of body mass center (HMC), and hip soft tissue thickness (STT). In this study, a two-level, subject-specific biomechanical model composed of a whole-body dynamics model and a proximal femur finite element model was used to predict the hip fracture risk for 80 subjects. The required information was obtained from the subject’s whole body and hip DXA (dual energy X-ray absorptiometry) images. Then, multivariate nonlinear least-square fits of power functions were used to investigate the effect of parameters on hip fracture risk. Results indicated that although BMD is the dominant parameter affecting the hip fracture risk, other parameters such as hip soft tissue thickness and anthropometric parameters also have considerable effects. This finding suggests that the hip fracture risk cannot be accurately predicted by the currently available single factor predictors as they do not consider all multifactorial parameters. However, the proposed function can properly predict the risk of hip fracture in the absence of any computational simulation and biomechanical model. It also quantifies the effect of musculoskeletal-, and organ-level parameters on hip fracture risk and demonstrates which individual is more likely to experience hip fracture.

Full two and three-dimensional single or multi-pass weld simulations are now feasible and practical given the development of improved analysis tools (e.g. ABAQUS), and significantly greater computer power. This paper describes a finite element analysis undertaken to predict the as-welded residual stress field following the welding of a tube attachment weld inside a thick pressure vessel (PV) forging. The coupled thermal-mechanical analysis was performed using the finite element (FE) code ABAQUS, A heat source modelling tool was employed to calculate welding fluxes, which were read into ABAQUS via a user subroutine. The ‘block’ dumped approach was utilised in the 2D thermal analysis such that complete weld rings are deposited instantaneously. Heat inputs were based on the actual weld parameters and bead sizes. The predicted fusion depths matched well with those found in sectioned weld test pieces. 2D FE sensitivity studies were performed examining the effect of variations in a number of parameters (bead sequence, hardening law, inter-pass temperature and annealing temperature). The hardening law was changed from isotropic to kinematic to investigate the effect of material behaviour. Large weld residual tensile stresses were calculated with significant compressive stresses in the adjacent vessel wall. Stress results were generally insensitive in the tube and forging, indicating that the vessel constraint dominates over local welding conditions. Weld hoop stresses were overestimated partly due to the ‘tourniquet’ effect of depositing rings of weld metal and the isotropic hardening law assumed.

Cloth has always been the most worldwide of all imported and exported commodities. It is an enlightening example of the movement of knowledge, skills, goods and investment across wide geographic seats. South Asia has been dominant for making of these worldwide interactions over period. This capacity grants advanced research that discovers the dynamic ways in which various textile production and trade regions generated the ‘first globalization’. A series of specialists connect this worldwide commodity with the dramatic political and economic alterations that characterised the India in the recent centuries. Together, the papers transform our understanding of the contribution of South Asian cloth, specifically Indian cloth to make the modern world economy. India is the largest share of its exports being textiles and apparels to the world. Also weaving is second only to agriculture sector in terms of providing employment in India. This paper a simple spreadsheet program method of calculations for the complete kinematics and dynamic analysis of the shedding mechanism of the classical powerloom is presented. Shedding is one of the important processes used in weaving technology of textile machineries. Most of the powerlooms of India uses staubli’s M5 module for shedding. These modules are activated through the traditional slider-crank mechanism. The source energy for these modules is through electric motor coupled with clutch and resulting output is shedding action of warp threads of cloth. Objective of this work is to address the kinematics and Dynamics simulation of linkage assembly of shedding mechanism of textile machinery considering all the links of the model as rigid one. Also this paper examines the effect of dynamic forces on various joints of conventional kinematic model. Subsequently the optimisation of mechanism is carried out by varying the design factor ratio of the slider crank mechanism. Length of connecting rod to radius of the crank shaft has been taken into account for defining design factor ratio for the analysis. Altered varieties of models having various design factors are modeled using 3D modeling package Solidworks. Simulation test results and force analysis of these models were carried out using ADAMS. Being a single degree of freedom mechanism as defined by its crank angle, the spreadsheet program can be used to answer what - if? situation queries through tables and graphical plots to evaluate variations of key motion and loading parameters with changes in the design factor. Thus, it allows for the conduct of parameter studies in selecting optimum crank-and-connecting-rod linkage dimensions and speeds. Thus, this work provides an alternative solution and scope for further research in shedding mechanism’s simulation analysis.

In conventional internal combustion engines, valves are opened and closed using a cam surface. The cam is kinematically related to the piston positions through the crankshaft and timing belt. In contrast, there is no crankshaft or kinematic cam surface in a free-piston engine to physically realize this mechanism. As a consequence, a free-piston engine has variable stroke lengths, which presents a challenge for active piston motion and precise stroke length control. This paper presents a virtual-cam based approach to relate free-piston motion to actuated engine valve control within a clear and familiar intuitive physical context. The primary functionality of the virtual cam control framework is to create a variable index, which is adjustable from cycle to cycle, for the exhaust/injection valves and spark timing similar to the function of physical cams in conventional engines. Since the cam is virtually created, it can be dynamically rebuilt to comply with cycle-to-cycle variations such as amount of the air/fuel supply, engine load and stroke length. This index rebuilding process is based on a cycle-to-cycle adaptive control method that uses the knowledge obtained from previous cycles to adjust the cam parameters. Preliminary experimental results are presented for a novel liquid-piston free-piston engine intended as a compact and efficient energy source for untethered power dense pneumatic systems such as untethered robots.

To help investigate the July 26, 2006, Crown Princess heeling casualty, the National Transportation Safety Board (NTSB) has developed a method to extract forces and moments acting on a ship from voyage data recorder (VDR) and other sources of recorded motion parameters. Other parameters can also be extracted with this simulation technique.

Abstract The present study focuses the attention on the correlation between the cam ring design and the kinematic flow ripple in balanced vane pumps. In particular, the work addresses the influence of the main pump design parameters on the oscillations of the flow rate produced by the volume variation of both undervane pockets and displaced chambers, which is considered as one of the main sources of excessive noise and vibration. The pump operating principle is firstly defined and the design philosophy is presented, together with the theoretical approach used to determine both then vane motion and resulting flow ripple. The proposed methodology is evaluated by means of a parametric study involving design parameters such as vane thickness and tip radius. The analysis suggests that these geometrical parameters, together with the cam ring shape, affect the pump dynamic behavior due to their correlation with the fluid-dynamics of the machine.

Full structural weld overlays (FSWOLs) have been used extensively as a repair/mitigation technique for primary water stress corrosion cracking (PWSCC) in pressurizer nozzle dissimilar metal (DM) welds. To support an approved FSWOL design and safety submission for British Energy pressurized water reactor (PWR) nozzles, an in-depth evaluation was performed to assess the effects of a FSWOL on the through-wall residual stress distribution in safety/relief pressurizer nozzles. Two safety/relief pressurizer nozzle mockups were fabricated based on British Energy’s PWR nozzle design. One mockup included the nozzle to safe-end DM weld and the safe-end to stainless steel weld while the second mockup included the DM weld, the stainless steel weld and a Westinghouse-designed structural weld overlay. The mockups were fabricated utilizing materials and techniques that represented the plant-specific nozzles as closely as possible and detailed welding parameters were recorded during fabrication. All welds were subsequently nondestructively evaluated (NDE). A thorough review of the detailed fabrication records and the NDE results was performed and several circumferential positions were selected on each mockup for subsequent residual stress measurement. The through-wall residual stress profiles were experimentally measured through the DM weld centerline at the selected circumferential positions using both the deep hole drilling (DHD) and incremental deep hole drilling (iDHD) measurement techniques. In addition to experimental residual stress measurements, the through-wall residual stress profiles were simulated using a 2-D axisymmetric ANSYS™ finite element (FE) model. The model utilized kinematic strain hardening and the temperature constraint method which greatly simplified the simulation as compared to detailed heat source modeling methods. A range of residual weld stress profiles was calculated by varying the time at which the temperature constraints were applied to the model. The simulation results were compared to the measurement results. It was found that the effects of the FSWOL were principally three fold. Specifically, the FSWOL causes a much deeper compressive stress field, i.e., the overlay shifts tension out towards the outside diameter surface. Further, the FSWOL reduces tension in the underlying dissimilar metal weld, and finally, the FSWOL causes higher peak compressive and tensile residual stresses, both of which move deeper into the nozzle wall after the overlay is applied. Relatively good agreement was observed between the FE results and the measurements results.