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271.
Development and Evaluation of a High Voltage Supply Unit for Electrorheological Fluid Dampers 总被引:1,自引:0,他引:1
Murray Sturk Graduate Research Assistant X.M. Wu Postdoctoral Fellow J.Y. Wong Professor Director respectively 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1995,24(2):101-121
Controllable dampers using electrorheological (ER) fluids have attracted considerable interest in recent years. They are proposed for use in semi-active suspensions for ground vehicles. The main advantages of ER fluid dampers are their fast response, ease of control, simple construction and low power requirements. This paper describes the development and testing of a high-voltage supply unit for modulating the damping force of an ER fluid damper. Experimental results on the vibration isolation characteristics of an ER fluid damper with different control strategies, obtained using a quarter-car model test rig, are also presented. 相似文献
272.
The influence of food quality on the nutritional metabolism of Acartia clausi was studied experimentally using four different diets: (1) diatom cells of Thalassiosira weissflogii, (2) detritus prepared from the same culture, (3) 50 : 50 mix on a protein basis of the two previous diets, and 4) dinoflagellate cells of Prorocentrum micans. For each trophic, ingestion, gut transit time, trypsin activity and Km (half saturation constant) were measured at limiting and saturating concentration. Assimilation rates were also estimated for both pure diatoms and mixed live–detrital cell diets. Ingestion followed a Holling type 2 response for diets 1 and 4, a linear one for detritus and an intermediate response for diet 3. Gut transit time displayed different adaptive changes with food regime depending on protein concentration. Trypsin activity was lower for detrital food and trypsin Km significantly decreased with increasing concentration of live diatoms. Assimilation rates were higher for live food than for mixed live–detrital food. Results illustrated that Acartia-type copepods optimize nitrogen or protein uptake. They suggest that besides chemoreception-mediated selectivity, internal controls by digestion and assimilation also regulate ingestion (feed-back). 相似文献
273.
274.
P. Bridges J. B. Russell 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1987,16(5):345-354
Hot wire anenometry measurements have been made in the wake of a model motorcycle and rider mounted in a windtunnel. Only in tests with a topbox present is there clear evidence of eddy shedding. Calculations have been performed on the corresponding full-scale motorcycle to determine the frequencies of the weave and wobble modes. Comparison with the wake frequencies extrapolated to full size show that at speeds of 31-34 m/s they coincide with those of the wobble mode which is found to be efficiently coupled to the aerodynamic excitation. 相似文献
275.
Peter B. Marlow 《Maritime Policy and Management》1991,18(4):283-311
This paper concentrates on the determinants of investment and examines both theoretical and empirical work on the investment function. The major determinants are considered and a case study of the United Kingdom shipping industry in the period 1963-1987 is undertaken. The analysis is unable to find any real link between the value of the investment incentives packages available to the UK shipping industry and the size of the UK fleet during this period. The conclusion follows that while financial factors (e.g. favourable credit arrangements) or individual components (e.g. investment grants) of fiscal packages may influence the decision to invest, the total package has not affected the level of shipping investment in the manner expected. 相似文献
276.
Y. H. Rim J. H. Moon G. Y. Kim S. D. Noh 《International Journal of Automotive Technology》2008,9(6):719-728
Automotive general assembly requires many manual assembly operations to be carried out by human workers. Ergonomic analysis
is an important part of the design and evaluation of products, jobs, tools, machines and environments for safe, comfortable
and effective human functioning. Most recent researches have involved the evaluation of working conditions to prevent work-related
musculoskeletal disorders. The majority of previous research on automotive companies has mainly considered the results of
ergonomic analyses such as RULA (Rapid Upper Limb Assessment), REBA (Rapid Entire Body Assessment) and OWAS (Ovako Working
Posture Analysis System). Analysis of static posture including reachability, clearances for arm, hand and tool has also been
used to evaluate working conditions. However, in addition to static posture analysis, a biomechanical analysis in dynamic
conditions should also be conducted. There are no integrated frameworks or standard schema for ergonomic analysis using digital
human models in digital environments. The purpose of this paper is to propose a new framework for the evaluation of working
conditions by ergonomic and biomechanical analysis using digital models based on XML standard schema, including: products,
processes, manufacturing resources and human workers. This paper presents the analysis results using the proposed framework
for automotive general assembly operations. We propose a new framework for the evaluation of the assembly operations and their
environments. Then we apply a digital human model to the dynamic simulation of general automotive assembly operations based
on standard schemas in XML and PPRH (Product, Process, Resource and Human). Using PPRH information based on a standard XML
schema to analyze the ergonomic and biomechanical results, the engineer can visualize, analyze and improve assembly operations
and working environments in automotive general assembly shops using digital models. 相似文献
277.
Undesired lateral force inevitably exists in a MacPherson suspension system, which is liable to damper rod’s side wear and
promotes the damper’s inner friction decreasing the ride performance from the suspension system. Substituting a new side load
spring with curved centerline for the conventional coil spring has been proven able to solve these problems and Multi-body
Dynamics combining with Finite Elements Analysis may be an efficient method in optimizing its design. Therefore, taking a
passenger car as example, a detailed multi-body dynamics model for the suspension system is built to simulate forces exerted
on the damper and the minimization of its lateral component is selected as the design target for the spring. When the structure
optimization of the side load spring is performed using FEA software ANSYS, its vertical and lateral elastic characteristics,
supported by test data, are analyzed. After importing FEA results back to the suspension system, the dynamics simulation can
be performed to validate the optimization result. 相似文献
278.
This paper is the second invstigation on the effect of fuel stratification on flame propagation. In the previous work, the
characteristics under the no port-generated swirl condition, i.e., the conventional case was studied. In this work, the flame
development under the low swirl condition was considered. For this purpose, the initial flame development and propagation
were visualized under different axially stratified states in a modified optical single cylinder SI engine. The images were
captured by an intensified CCD camera through the quartz window mounted in the piston. Stratification was controlled by the
combination of the port swirl ratio and injection timing. These were averaged and processed to characterize the flame propagation.
The flame stability was estimated by the weighted average of flame area and luminosity. The stability was also evaluated through
the standard deviation of flame area and propagation distance and through the mean absolute deviation of the propagating direction.
The results show that the flame-flow interaction determines the direction of flame propagation and that the governing roles
of the two factors vary according to the stratified state and the location in the cylinder. In addition, the flame development
and the initial flame stability are strongly dependent on the stratified conditions, and the initial flame stability is closely
related to the engine stability and lean misfire limit. Lastly, there is no essential difference in gasoline and CNG flame
propagation characteristics. 相似文献
279.
The impact of high-speed technology on railway demand 总被引:1,自引:0,他引:1
This paper estimates a passenger railway demand function to analyse effects arising from the introduction and use of high-speed
technologies. The paper reports estimates of demand elasticities with respect to price, income, quality of service and a range
of exogenous characteristics. The results show that travel time savings from conventional high-speed technology have a larger
impact on passenger demand than tilting train technology. The introduction of conventional high-speed technology is associated
with an 8% increase in passenger railway demand. Increasing the use of either type of high-speed technology appears to induce
small positive effects on demand beyond those obtained from usual traffic density increases on non-high-speed existing technology.
Antonio Couto is an assistant professor in the Faculty of Engineering (FEUP) at the University of Porto. He received his PhD from FEUP in 2005 having completed a thesis in railway transport economics. His research focuses on issues related to transport economics and infrastructures. Daniel J. Graham is a Reader in the Centre for Transport Studies at Imperial College London. He specialises in the economics of transport, focusing in particular on modelling the implications of transport provision and accessibility for productivity and economic growth. 相似文献
Daniel J. Graham (Corresponding author)Email: |
Antonio Couto is an assistant professor in the Faculty of Engineering (FEUP) at the University of Porto. He received his PhD from FEUP in 2005 having completed a thesis in railway transport economics. His research focuses on issues related to transport economics and infrastructures. Daniel J. Graham is a Reader in the Centre for Transport Studies at Imperial College London. He specialises in the economics of transport, focusing in particular on modelling the implications of transport provision and accessibility for productivity and economic growth. 相似文献
280.
Exploring spatial variety in patterns of activity-travel behaviour: initial results from the Toronto Travel-Activity Panel Survey (TTAPS) 总被引:1,自引:0,他引:1
Studies of urban travel behaviour typically focus on weekday activities and commuting. This is surprising given the rising
contribution of discretionary activities to daily travel that has occurred during the last few decades. Moreover, current
understanding of the relationship between travel behaviour and land use remains incomplete, with little research carried out
to explore spatial properties of activity-travel behaviour during the off-peak and weekend time periods. Weekend behaviours,
for example, influenced by the availability of time and the spatiotemporal distribution of “weekend” destinations, likely
produce spatially and temporally distinct activity-travel patterns. Using data from the first wave of the Toronto Travel-Activity
Panel Survey (TTAPS), this paper examines an area of research that has received little attention; namely, the presence of
spatial variety in activity-travel behaviour. The paper begins by looking at the extent to which individuals engage in spatially
repetitive location choices during the course of a single week. Area-based measures of geographical extent and activity dispersion
are then used to expose differences in weekday-to-weekend and day-to-day activity-travel patterns. Examination of unclassified
activities carried out over a 1 week period reveals a level of spatial repetition that does not materialise across activities
classified by type, travel mode, and planning strategy. Despite the inherent spatial flexibility offered by the personal automobile,
spatial repetition is also found to be surprisingly similar across travel modes. The results also indicate weekday-to-weekend,
and day-to-day fluctuations in spatial properties of individual activity-travel behaviour. These findings challenge the utility
of the short-run survey as an instrument for capturing archetypal patterns of spatial behaviour. In addition, the presence
of a weekday-to-weekend differential in spatial behaviour suggests that policies targeting weekday travel reduction could
have little impact on travel associated with weekend activities.
相似文献
Tarmo K. RemmelEmail: |