Dynamic characteristics of hydraulic power steering system with accumulator in load-haul-dump vehicle

Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and discussed with SIMULINK software and hydraulic control theory. The results show that the dynamic characteristics of hydraulic power steering system are improved obviously by using bladder accumulator, the hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle generates vibration at the initial stage under the normal steering condition of pulse input, and its static response time is 0.25 s shorter than that without bladder accumulator. Under the normal steering working condition, the capacity of steering accumulator for absorbing pulse is directly proportional to the cross section area of connecting pipeline, and inversely proportional to the length of connecting pipeline. At the same time, the precharge pressure of nitrogen in steering accumulator should be 60%80% of the rated minimum working pressure of hydraulic power steering system. Under the abnormal steering working condition, the steering cylinder piston may obtain higher motion velocity, and the dynamic response velocity of hydraulic power steering system can be increased by reducing the pressure drop of hydraulic pipelines between the accumulator and steering cylinder and by increasing the rated pressure of hydraulic power steering system, but the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle have nothing to do with the precharge pressure of nitrogen in steering accumulator.

Dynamic effect of heavy-haul train on seismic response of railway cable-stayed bridge

This paper focuses on understanding and evaluating the dynamic effect of the heavy-haul train system on the seismic performance of a long-span railway bridge. A systematic study on the effect of heavy-haul trains on bridge seismic response has been conducted, considering the influence of vehicle modeling strategies and dynamic characteristics of the seismic waves. For this purpose, the performance of a long-span cable-stayed railway bridge is assessed with stationary trains atop it, where the heavy-haul vehicles are modeled in two different ways: the multi-rigid body model with suspension system and additional mass model. Comparison of the bridge response in the presence or absence of the train system has been conducted, and the vehicle loading situation, which includes full-load and no-load, is also discussed. The result shows that during the earthquake, the peak moment of the main girder and peak stress of stay cables increase by 80% and by 40% in the presence of fully loaded heavy-haul trains, respectively. At the same time, a considerable decrease appears in the peak acceleration of the main girder. This proves the existence of the damping effect of the heavy-haul train system, and this effect is more obvious for the fully loaded vehicles. Finally, this paper proposes an efficient vehicle modeling method with 2 degrees of freedom(DOF) for simplifying the treatment of the train system in bridge seismic checking.

Description of nonstationary non-Gaussian processes using finite atomic functions

The possibility of using finite atomic functions of Kravchenko-Rvachev for description of the laws of distribution of the refractive index of the troposphere,the intensity of the scattering from the sea,seasonal behavior unit radar cross section(RCS)of land areas with vegetation covering,as well as the spectrum of electromagnetic spikes of lithospheric origin is considered.

Recouping Braking Energy from Diesel-Hauled Commuter Trains

Research was undertaken to define the concept of a coach-based braking energy recoupment, storage and regeneration system to augment the acceleration of regional commuter trains hauled by diesel locomotives. Functional specifications were developed having the goal of increasing by 25% the acceleration rate of a train consisting of 10 bi-level coaches hauled by a 3,000 hp diesel locomotive, typical of the rolling stock now in commuter services in Canada and the USA. Examining three alternate hybrid system technologies for train retardation based, respectively, on hydrostatic, battery and ultracapacitor energy storage. The ultracapacitor hybrid system appeared the most promising due to the capability ofultracapacitors to repeatedly and rapidly accept large energy charges without degradation, temperature insensitive and flexible in the placement of modules in the limited space available. Analyses of train operation simulations showed that in addition to augmenting acceleration and reducing trip time, braking energy recoupment reduced fuel consumption and concomitant diesel emissions.

Vehicle Detection Method with Sub-stretching Based on Light Contrast in Fog Road Image

In this paper, detection of a vehicle from a road image with fog is focused to detect an vehicle from a foggy image. Because of the fog in the image, a shape of an object is vague. Therefore an obstacle may occur on the vehicle detection. Thus, features from a foggy road image are surveyed through experinmlts, and a histogram is caloalated with the bright value. The stretching method is then applied with the specific weight as the centre to detect a vehicle smoothly. If the high density area, from the view point of histogram, is applied with the stretching method, the definition of the image can be increased. On this fact, this paper proposed a method to divide the histogram and to determine applicable range of the stretching method. The improved results by the proposed methods are proved with the camparison tests between the proposed and previous methods.

Effect of Traffic Speed on Stresses and Strains in Asphalt Perpetual Pavement

Increasing traffic volumes and loads as well as public expectation for a long-lasting transportation infrastructure have necessitated designing perpetual pavements. The KDOT （Kansas Department of Transportation） conducted a field trial to investigate the suitability of perpetual pavement concept for Kansas highway pavements. The experiment involved construction of four thick pavement structures. To verify the approach of designing perpetual pavements on the basis of an endurance strain limit, the pavements were instrumented with gauges for measuring tensile strains at the bottom of asphalt base layers at various speeds. Pavements were also instrumented with pressure cells to measure stress on the top of subgrade. Pavement response measurements under known vehicle load were performed in August 2006. FWD （Falling-weight deflectometer） was also used to collect deflection data at 15 m intervals on the same date. FWD first-sensor （center） deflections were normalized and corrected to 20 ℃ temperature based on measured mid-depth pavement temperature. The result shows that strain and stress measurements show significant amount of variations. Measurements in the thickest section are the most consistent. The higher the traffic speed, the lower the strains and stresses. The difference between strains and stresses at 30 kmhar and 65 km/hr is higher than the difference between 65 km/hr and 95 kin/hr. This shows the effect of speed on stresses and strains decreases as the speed increases. Softer binder in the asphalt base layer results in lower strains, which confirms that softer binder results in higher fatigue life.

Spatial gust impact analysis on safety and comfort of a train crossing cable-stayed bridge combining statistical method

In order to study the safety and the comfort of high-speed trains running on a single-tower cable-stayed bridge under spatial gust,a dynamic model of wind-train-bridge analysis model is built based on the autoregressive method,the multi-body dynamics method and the finite element method.On this basis,the influence of spatial gust model loading,the suspension parameters change,wind attack angle and speed on the train-bridge system are analyzed by combining the time/frequency domain analysis and statistical methods.The results show that the spatial gust environment is one of the most important factors affecting safety and comfort and can make the calculation result tend to be conservative and more conducive.The response changes caused by K_(py),K_(px) and K_(sx) changes are nearly linear,while Ksy shows nonlinear characteristics and the most sensitivity.Wind attack angle at 75°and 90°has the greatest influence on the vehicle-bridge system.For ride comfort index,when pre-set wind speed(α=75°)reaches 20 m/s,the vertical acceleration firstly exceeds the limit value;when wind speed(α=90°)reaches 21.5 m/s,the lateral acceleration firstly exceeds the limit value,and the ride comfort of the vehicle cannot be guaranteed.For running safety index,when pre-set wind speed(α=75°)reaches 24.6 m/s,the wheel unloading coefficient firstly exceeds the limit;when pre-set wind speed(α=90°)reaches 24.5 m/s,the derailment coefficient firstly exceeds the limit,and the running safety cannot be guaranteed.The results can provide a suitable reference for the safe and stable operation of trains on the bridge.

Effects of fundamental factors on coupled vibration of wind-rail vehicle-bridge system for long-span cable-stayed bridge

In a wind-vehicle-bridge(WVB) system,there are various interactions among wind,vehicle and bridge.The mechanism for coupling vibration of wind-vehicle-bridge systems is explored to demonstrate the effects of fundamental factors,such as mean wind,fluctuating wind,buffeting,rail irregularities,light rail vehicle vibration and bridge stiffness.A long cable-stayed bridge which carries light rail traffic is regarded as a numerical example.Firstly,a finite element model is built for the long cable-stayed bridge.The deck can generally be idealized as three-dimensional spine beam while cables are modeled as truss elements.Vehicles are modeled as mass-spring-damper systems.Rail irregularities and wind fluctuation are simulated in time domain by spectrum representation method.Then,aerodynamic loads on vehicle and bridge deck are measured by section model wind tunnel tests.Eight vertical and torsional flutter derivatives of bridge deck are identified by weighting ensemble least-square method.Finally,dynamic responses of the WVB system are analyzed in a series of cases.The results show that the accelerations of the vehicle are excited by the fluctuating wind and the track irregularity to a great extent.The transverse forces of wheel axles mainly depend on the track irregularity.The displacements of the bridge are predominantly determined by the mean wind and restricted by its stiffness.And the accelerations of the bridge are enlarged after adding the fluctuating wind.

Assessment of occupational noise pollution for metal industries in Kingdom of Saudi Arabia

The main objectives of this study was measuring levels of noise generated by machinery that workers at metal industrial facilities in the Kingdom of Saudi Arabia （KSA） are exposed to as well as to determine if these levels were in conformity with adopted standards. To achieve the objectives of this study the following six metal industrial facilities were selected： a foundry plant, a building-metal production factory, a cold processing steel manufacturing plant, a hollow-metal door and doorframe manufacturer, a car-exhaust-system factory and a metal-can producer. The study found that workers operating machinery without any kind of protection were exposed to unacceptably high levels of noise that exceeded the internationally acceptable values as per occupational noise exposure-1910.95 regulations adopted standard. It was founded that 73% of work site investigated have noise level over 85 dB. A level of 116 dB was recorded at steel plant fiat section product with continuous occupation and 115.2 dB in metal product factory with labor continuous occupation. Based on the results obtained in this study, it is evident that a competent environmental and health agency needs to be established and that stricter noise-level standards ought to be enforced in order to protect employee health.

System integration and innovation of operating 20 kt combined heavy-haul train on Datong-Qinhuangdao line

Datong-Qinhuangdao line, as the first electrified double-track heavy-haul line dedicated to coal transport in China, extends from Datong in the west, and reaches Qinhuangdao in the east, opened to traffic in December, 1992, totaling 653 km with the designed annual traffic volume of 1×108 t. In order to meet the demands of national economic development, the transport capacity of the line must be enhanced greatly. Depending on independent innovation, MOR, for the first time in the world,realizes the integration between GSM-R and Locotrol, the integration between 800 MHz digital radio and Locotrol, and the integration between a single set of Locotrol and SS4 locomotive. Meanwhile, CR develops equipment portfolio for heavy-haul through combining 2 high power locomotives of HXD series (means harmony) with controllable EOT. Relying on integration and innovation, it succeeds in operating 20 kt-level combined heavy-haul train on Datong-Qinhuangdao line, which tripled the annual traffic volume of the line from 1×108 t in 2002 to 3×108 t in 2007.

Electromechanical Aspects of an Experimental Hybrid Vehicle

The design and construction of an experimental solar hybrid vehicle based on the combination of photovoltaic solar energy as the main source of electricity and electric power supplied by a generator activated by the driver＇s pedaling is introduced. The vehicle has a battery to store the energy provided by both systems. The development was motivated by a Latin American solar car race through the Atacama Desert in Chile and the initiative to promote the use of clean energy for transport. A general description of the vehicle, its energetic aspects and experimental results are presented.

Simulation of vehicle braking behavior on wet asphalt pavement based on tire hydroplaning and frictional energy dissipation

To investigate the influence of wet conditions on vehicle braking behavior,a numerical-analytical method was proposed for the simulation of tire hydroplaning and frictional energy dissipation. First, a finite element model of tire hydroplaning was established using the coupled EulerianLagrangian method,including a pneumatic tire model and a textured asphalt pavement model. Then,the frictional force on the tire-pavement interface at different speeds was calculated by the model. Based on vehicle braking mechanism and frictional energy dissipation,a calculation method for braking distance was proposed based on a three-stage braking process. The proposed method was verified by comparing the calculated hydroplaning speed and braking distance with field test results.Then,vehicle braking distances and wet friction coefficients were calculated under different conditions. The results show that thinner water film,a more complex tread pattern and higher tire inflation pressure all contribute to the vehicle braking performance; moreover, the pavement texture has obvious influence on vehicle braking behavior,especially at a high speed. The proposed method shows great effectiveness in predicting vehicle braking behavior on wet asphalt pavements.

Investigating Mercury Existence in Some Stations in Tigris River in Iraq

Mercury concentration in water, sediments and two aquatic plants were measured in the Tigris River for the period in 2013 Hg concentrations in water between 0.18-0.74 μg/g, however, in sediments ranged between 0.66-0.73 lag/g. The concentrations of accumulated mercury in aquatic plants ranged in Ceratophyllum demersum and Phragmitus australis were 0.035-0.022, 0.028-0.023 μg/g, respectively. The concentration bioconcentration factor B.C.F range between 0.331-0.209 μg/g and B.S.F 0.043-0.011 μg/g. These results indicate the ability of the aquatic plants of Tigris River to accumulate elements in their tissues more than water consequently, mercury concentrations in the food chain path way could cause health problems on public health by transfer through aquatic organisms to human. The studied plants could be considered as bioindicator for elements flow to the river from natural and anthropogenic sources. The study showed there is an increase in the concentration of this element in the Tigris River and due to the low rate of discharge of river water, which leads to high concentrations of ions dissolved and effect divorced industrial waste and sewage and irrigation water, especially in the area of Zafaraniyah a result of the large number of events industrialized as well as the impact of the Diyala River on the River Tigris.

拉车

今年暑假的一天，爸爸到东岭送粪，要我帮他拉车。 拉车可不是好活儿走快了，推车的跟不上；走慢了，车容易压绳翻跟头。所以。只能像老牛那样，不紧不慢地向前走才行。刚开始拉，爸爸就提醒我：“注意点，不要把绳子拉弯了。”我稍一使劲，他又叫了起来：“慢一些!慢一些!”

拉车

由于在一次施工中双臂受伤，这些日子我只得在家休养。咋天，我独自到郊外散步，走到一个土坡前，看见一个小伙子正拉着一辆装满红砖的人力车上坡，拉到一半就拉不动了，可他又不敢停下来休息，仿佛一松劲儿，车子就会退回坡底。恰在此时，那个小伙子看见了我，便喊了一声：“帮帮忙好吗？”

Simulation software for CRH2 and CRH3 traction driver systems based on SIMULINK and VC

Simulation models of traction driver systems were established using SIMULINK,according to the actual structure and parameters of China Railway High-Speed 2 (CRH2) and China Railway High-Speed 3 (CRH3) trains.In these models,the traction motor adopts transient current control and an indirect rotor magnetic field orientation vector control strategy,and the traction converter uses sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) methods.After these models are transformed in VC++ program,and a friendly interface and data processing system are constructed,simulation software is obtained for CRH2 and CRH3 traction driver systems.On this basis,the operational performance of a traction converter was simulated and analyzed at different train speeds and in different conditions.The simulation results can provide a reference for the actual design and production of a traction converter.

Evolutionary ecology of chemosensation and its role in sensory drive

All behaviors of an organism are rooted in sensory processing of signals from its environment, and nat ural selection shapes sensory adaptations to ensure successful detection of cues that maximize fitness. Sensory drive, or divergent selection for efficient signal transmission among heterogeneous environ ments, has been a useful hypothesis for describing sensory adaptations, but its current scope has pri marily focused on visual and acoustic sensory modalities. Chemosensation, the most widespread sensory modality in animals that includes the senses of smell and taste, is characterized by rapid evolu tion and has been linked to sensory adaptations to new environments in numerous lineages. Yet, olfac tion and gustation have been largely underappreciated in light of the sensory drive hypothesis. Here, we examine why chemosensory systems have been overlooked and discuss the potential of chemo sensation to shed new insight on the sensory drive hypothesis and vice versa. We provide suggestions for developing a framework to better incorporate studies of chemosensory adaptation that have the po tential to shape a more complete, coherent, and holistic interpretation of the sensory drive.

Novel approach to and implementation of design and analysis of armored face conveyor power train

An armored face conveyor(AFC) is a key piece of equipment for a fully mechanized long-wall mining system and is currently the only means for transporting bulk material in hard coal mines. To date, the AFC power train design has mainly been based on heuristics obtained via experience, coupled with simple calculations, which cannot take the dynamic behaviors and coupling effects of the components into consideration. Therefore, model-based and simulation-driven design is preferred. In this paper, a new design and analysis methodology for an AFC power train is presented to achieve the optimal dynamic characteristics and transmission performance. A preliminary design procedure for a power train is first introduced. Then, a system-level hydro-mechatronic model of the power train is built to evaluate and optimize the preliminary scheme. Sub-models, including those for the motors, fluid couplers, gearboxes, and chain, are obtained according to their individual disciplines and assembled to form the system-level model. The chain sub-system is discretized into multiple finite elements. Governing equations are established for each element based on the Newton Euler approach and assembled according to the topological structure of the chain system. In order to make the new approach applicable for engineers, a design and analysis software is developed, with a graphical user interface that involves the whole design process. MATLAB/SIMULINK is used as the computational engine, and Visual C++ is adopted to develop the interactive software framework. Simulations for the SGZ1000/2000 type AFC are provided as an illustrative case study to validate the effectiveness and practicality of the model and software package.

Genetic basis for body size variation between an anadromous and two derived lacustrine populations of threespine stickleback Gasterosteus aculeatus in southwest Alaska

Body size is a highly variable trait among geographically separated populations. Size-assortative reproductive isolation has been linked to recent adaptive radiations of threespine stickleback （Gasterosteus aculeatus） into freshwater, but the genetic basis of the commonly found size differ- ence between anadromous and derived lacustrine sticklebacks has not been tested. We studied the genetic basis of size differences between recently diverging stickleback lineages in southwest Alaska using a common environment experiment. We crossed stickleback within one anadromous （Naknek River） and one lake （Pringle Lake） population and between the anadromous and two lake populations （Pringle and JoJo Lakes）, and raised them in a salinity of 4-6 ppt. The F1 anadromous and freshwater forms differed significantly in size, whereas hybrids were intermediate or exhibited dominance toward the anadromous form. Additionally, the size of freshwater Fls differed from their wild counterparts, with within-population Fls from Pringle Lake growing larger than their wild counterparts, while there was no size difference between lab-raised and wild anadromous fish. Sexual dimorphism was always present in anadromous fish, but not in freshwater, and not always in the hybrid crosses. These results, along with parallel changes among anadromous and fresh- water forms in other regions, suggest that this heritable trait is both plastic and may be under di- vergent and/or sexual selection.