Virtual flow paths for free-ranging automated guided vehicle systems

Recent technological development in vehicle design allow vehicles to operate without physical guide paths, i.e. free-ranging automated guided vehicles. This paper addresses the problem of defining flow paths for these vehicles. A model is presented whereby the number of allowable flow paths and the flow directions between nodes (representing pickup/delivery stations and aisle intersections) of the layout network are determined. Examples are presented to demonstrate the approach.     

Two-dimensional integration of a vertical-cavity surface-emitting laser and photodetectors for position sensing

Noncontact long-range position sensing is desirable for a number of applications. We have designed and fabricated a monolithically integrated vertical-cavity surface-emitting laser (VCSEL) and p-type/intrinsic/n-type (PIN) photodetectors for optical position sensing. Calculations using the reflection from a periodic metallic corrugation as a position gauge indicate resolution in the submicron regime. High device uniformity is obtained using novel fabrication techniques. We observe a threshold current of 0.52 mA for the VCSELs and a detector responsivity of 0.38 A/W at 840 nm. The optical cross talk between VCSELs and detectors is also quantified.     

Two-dimensional position sensing Si detectors: Current and charge pulse characteristics

The current and charge pulse characteristics of two-dimensional position sensing Si detectors (PSDs) employing resistive charge division have been measured by making use of pulsed photon systems. The detectors studied are discrete two-dimensional PSDs where individual gold and orthogonal aluminum strips are deposited on the front and back surfaces, respectively, of the silicon wafer. Resistive charge division is accomplished by two external resistor networks. Detector fabrication and the pulsed photon systems are described. The anomalous currents (i.e., polarity reversal with time) exhibited by these detectors, which we reported earlier, have been studied and their time characteristics determined. Calculations based on a simplified model of the detector predict these anomalous currents, and the results of the calculations are compared with measurements. The currents characteristic of two-dimensional detectors have measured time durations considerably longer than those measured for equivalent one-dimensional detectors. Further, the anomalous currents result in ballistic deficits which are greater than unity, an effect entirely absent for one-dimensional detectors. For detectors having fixed area and thickness, the requirement that these detectors exhibit near distortion-free position response for heavy ions in the presence of intense background fluxes (i.e., protons) imposes strong restrictions on the total resistance of the external resistor networks, which are discussed.     

航空充氮(氧)车充气回收方法研究

通过理论分析计算和实践验证,对现行航空充氮(氧)车充气导管放空损失进行了深入的分析研究,设计出回气操作法和加装回气瓶的方法,使充氮(氧)车的放空损失下降20%左右,保障能力明显提高。     

Cooperative federated filtering approach for enhanced position estimation and sensor fault tolerance in ad-hoc vehicle networks

The present study addresses a solution to the position and orientation estimation problem of vehicles in ad-hoc vehicle networks using decentralised filtering. Specifically, a distributed filter operating in a cooperative federated structure for enhancing the estimation accuracy of vehicles state over unreliable wireless communication networks subject to uncertain and limited measurements is proposed. The filter relies on a variety of position measurements obtained from the on-board vehicle positioning system, from other cooperating vehicles in the vicinity, as well as from the immediate roadside environment via communication. Direct distance measurements between vehicles, furthermore, between vehicles and the stationary elements of the infrastructure can be used, if available, as highly accurate reference measurements. The study demonstrates how successfully the novel idea of cooperative federated filtering in addressing the demands of both fault tolerance and enhanced estimation accuracy in ad-hoc vehicle networks can be used.     

车载LNG绝热气瓶的BOG吸附回收装置设计与性能测试

液化天然气(Liquefied Natural Gas,LNG)燃料汽车的应用范围主要是大型公交和重卡,其闪蒸气(Boiling Off Gas,BOG)的排放限制了LNG在小型家用汽车上的应用。设计了一套闪蒸气(BOG)吸附储存装置,该装置容积15 L,内装翅片管。在车辆停止时,LNG不断蒸发,并被吸附罐吸附,使得LNG杜瓦内压力维持在较低值;车辆启动时,将天然气脱附并燃烧。在常温,低压的吸附条件(1.5 MPa,30℃)下,测试了吸附储罐的吸附性能。针对高表面积吸附剂(比表面积1 500 m2/g以上),吸附能力最大可达43.5 V/V。同时,测试了不同脱附温度,脱附速度下,吸附储罐的脱附性能。     

Dose rate calculations for a reconnaissance vehicle

A Chemical Nuclear Reconnaissance System (CNRS) has been developed by the British Ministry of Defence to make chemical and radiation measurements on contaminated terrain using appropriate sensors and recording equipment installed in a land rover. A research programme is under way to develop and validate a predictive capability to calculate the build-up of contamination on the vehicle, radiation detector performance and dose rates to the occupants of the vehicle. This paper describes the geometric model of the vehicle and the methodology used for calculations of detector response. Calculated dose rates obtained using the MCBEND Monte Carlo radiation transport computer code in adjoint mode are presented. These address the transient response of the detectors as the vehicle passes through a contaminated area. Calculated dose rates were found to agree with the measured data to be within the experimental uncertainties, thus giving confidence in the shielding model of the vehicle and its application to other scenarios.     

超级电容器中的二维材料

以石墨烯为代表的具有层状结构的二维材料因具有大比表面积等特性成为超级电容器电极材料的热门候选.文章着眼于针对诸如石墨烯、过渡金属二硫族化合物、过渡金属碳/氮化物、层状过渡金属氧化物/氢氧化物等二维材料在超级电容器领域应用的研究,尝试总结了其制备方法、产物形貌特征以及作为电极的性能等,并对这一领域的未来发展和面临的挑战提出了看法与预测.     

超级电容器中的二维材料

以石墨烯为代表的具有层状结构的二维材料因具有大比表面积等特性成为超级电容器电极材料的热门候选。文章着眼于针对诸如石墨烯、过渡金属二硫族化合物、过渡金属碳/氮化物、层状过渡金属氧化物/氢氧化物等二维材料在超级电容器领域应用的研究,尝试总结了其制备方法、产物形貌特征以及作为电极的性能等,并对这一领域的未来发展和面临的挑战提出了看法与预测。     

Loading constraints for a multi-compartment vehicle routing problem

OR Spectrum - Multi-compartment vehicles (MCVs) can deliver several product segments jointly. Separate compartments are necessary as each product segment has its own specific characteristics and...     

Two-dimensional correlation analysis for a kinetic model of consecutive reactions

We have systematically studied a kinetic scheme of consecutive reactions by using generalized two-dimensional (2D) correlation analysis as reported by Noda. The correlations between reactant-intermediate, intermediate-product, and reactant-product pairs are analyzed with the related rate constants and absorption coefficients. When the reference spectrum is set at zero, the synchronous and asynchronous correlation spectra for the kinetic model are almost free from the influence of poor quality signals. If an appropriate reference spectrum is selected, the intermediate can be feasibly distinguished from other species involved in the reaction. A ratio of asynchronous to synchronous correlation intensity yields a coherence spectrum, which is characterized by different plateau-type peak intensities. When a steady-state condition fits the kinetic model, the peak summation of reactant-intermediate and intermediate-product correlation will approach the intensity of the reactant-product correlation. The coherence spectrum is useful for pattern recognition of the reaction scheme and also provides an effective way to identify the location and the extent of spectral overlap between two peaks.     

4WID-4WIS智能车阿克曼转向轨迹规划及位置估算

针对四轮独立驱动与四轮独立转向(four-wheel independent drive and four-wheel independent steering,4WID-4WIS)智能车的转向行驶工况,基于阿克曼转向原理,提出一种利用三阶贝塞尔曲线进行轨迹规划的新方法.首先,采用最优函数获取一条满足智能车初始状态约束...     

Seat position and the risk of serious thoracoabdominal injury in lateral motor vehicle crashes

CONTEXT: Previous studies have suggested that motor vehicle occupants seated on the near-side of a lateral impact have a higher proportion of thoracoabdominal injuries. However, due to limitations in previous studies, the true association between seat position, side of lateral impact, and thoracoabdominal injury is unclear. OBJECTIVE: To assess the relationship between seat position (i.e., near-side, middle-seat, and far-side, regardless of row), side of lateral motor vehicle crash (MVC), and serious thoracoabdominal injury after adjusting for important crash factors. DESIGN: National population-based cohort of adult subjects involved in MVCs and included in the National Automotive Sampling System Crashworthiness Data System database (NASS CDS) from 1995 to 2003. PATIENTS: Occupants aged > or =16 years involved in MVCs where the highest external deformation of the vehicle was located on the right or left side (i.e., lateral). MAIN OUTCOME MEASURE: Serious thoracic or abdominal injury, defined as an Abbreviated Injury Scale (AIS) > or =3 in the thoracic or abdominal body region. RESULTS: Fifteen thousand, one hundred and sixty persons involved in primary lateral MVCs were represented in the NASS CDS database during the 9-year period. There were 1867 (2%) persons with serious thoracic injuries and 507 persons (0.5%) with serious abdominal injuries. In multivariable logistic regression models that adjusted for important crash factors and the NASS CDS sampling design, seat position was a strong effect modifier of the association between side of lateral impact and serious thoracic (p<0.0001) and abdominal (p=0.0009) injury, with the risk of serious thoracic and abdominal injury highest for occupants seated on the near-side of the crash. The mean probability of injury was higher for near-side and middle-seat occupants compared to far-side occupants, and the probability of thoracic injury was approximately four times higher than that of abdominal injury for all seat positions. CONCLUSIONS: There is a strong, synergistic relationship between seat position and side of lateral MVC in assessing risk of serious thoracic and abdominal injury among adult occupants. The probability of serious thoracoabdominal injury increases with increasing proximity of seat position to side of the crash and the risk of thoracic injury is higher than abdominal injury for all seat positions.     

Two-dimensional metamaterials for epitaxial heterostructures

We review the use of two-dimensional psuedomorphic materials to accommodate an extraordinary range of misfit and allow novel new phases to be grown epitaxially. These materials assume the structure of the substrate and can thus be regarded as metamaterials. We illustrate these principles through a number of systems, including a detailed structural and spectroscopic study of epitaxial VO₂/NiO heterostructures. In this case the metamaterial is VO_1+x which is structurally and electronically distinct from the bulk of the VO₂ film. In the transition region the crystal structure adopts that of the NiO layer, while the oxidation state of vanadium increases from ∼3+ to ∼4+ with thickness, accompanied by increasing lattice disorder. The formation and evolution of this interfacial phase, VO_1+x, accommodates the change in crystal symmetry across the interface from the rock-salt structure of NiO to the rutile structure of VO₂. The use of two-dimensional metamaterials opens a wealth of new opportunities for the growth of new materials with novel properties.     

Two-dimensional buoyant jet in a current

Summary When an effluent is discharged into a current at or near the bed, it may be advantageous to have the effluent flowing along the bed for some distance, thickening en route, so that it will have become diluted sufficiently before it reaches the surface. This can be achieved provided the effluent is discharged from a narrow long slot into the ambient current; the effluent plume then flows near the bed due to the pressure drop on the lee side of the emerging effluent.To confirm that this type of effluent flow could exist, laboratory experiments were conducted in which warm water at about 76° C was discharged vertically upwards from a slot 1 cm wide into an ambient current at a temperature of about 12° C. It was observed that the discharged effluent rose a short distance above the slot, due to its initial momentum, and then re-attached itself to the rigid floor, continuing along the floor as it slowly thickened. The temperature and its fluctuation, the velocity and the thickness of the layer, were measured for various ratio of the ambient velocity to the jet velocity and densimetric Froude numbers at the slot. It was found that flow in the layer at a certain distance from the slot is dynamically similar, and that the measured data can be described by non-dimensional similarity functions in the density and velocity field. It was also shown, both theoretically and experimentally, that the depth and the dilution factor, based on the maximum temperature of the under-flowing layer, increases linearly with down-stream distance from the slot.It was further found that the coefficient of skin friction depends on Richardson number and that the coefficient remains constant for a given flow condition.Notation C ₁,C ₂ constant coefficients equation (2.12) - C _f coefficient of skin friction - F ₀ densimetric Froude number equation (4.9) - F _x,F _y components of the buoyancy force inx andy direction - f ₁(),f ₂(),g ₁()g ₂(),g ₁₂() universal functions equation (2.4) - g– acceleration due to gravity - I ₁,I ₂ integrals of functionf ₁() andf ₂() equation (2.15) - h– characteristic thickness of the underflowing layer - h ₀ depth of the warm layer at section A-A (Fig. 1) - H depth of the ambient current - n index associated with raw data - N total number of digitized data - p pressure - R ratio of the ambient velocity to the jet velocity - R _e Reynolds number based at the slot - R _i Richardson number equation (2.12) - T local arithmetic mean value of temperature - T ₀ temperature of the jet at slot exit - T _a temperature of the ambient current - T _m maximum temperature at each section - t _n instantaneous point temperature - t time - root-mean-square of temperature - U local mean velocity in the mean flow direction - U _a average mean velocity of the ambient current (see Fig. 1) - U ₀ jet velocity at the slot exit - U _* shear velocity - V local mean velocity in the vertical direction - velocity fluctuation ofU andV component respectively - w slot width - X ₀ non-dimensional distance from the virtual origin - x, y system of co-ordinates (Fig. 1) - relevant length scale at which the temperature excess is half of its maximum value - non-dimensional transverse distance - angle of inclination of the rigid boundary - ratio between the length scale and the characteristic thicknessh - kinematic viscosity - local mass density - ₀ mass density at slot exit - _a mass density of the ambient current - ₀ mass density excess at the slot exit - _m maximum of mass density excess at each section - ₀ shear stress at rigid boundary - ₁, ₂, ₁, ₂ universal functions equations (4.5, 4.6, 4.7, 4.8)     

Two-dimensional motion in a Bell-constrained plate

The so-called Bell constraint has been used for several years in plasticity theory and has additionally been the subject to several investigations within an elastic context. In this paper the effects of the Bell constraint on the propagation of harmonic waves in a finitely deformed elastic plate are considered. Strong ellipticity conditions are first derived for the unbounded case, and are shown to be dependent on the scalar multiplier associated with the Bell constraint. The dispersion relation, associated with harmonic wave propagation in a plate composed of such a material with zero incremental surface traction, is derived in respect of an arbitrary strain energy function. Asymptotic expansions are then obtained for high and low wave number. These expansions, which give phase speed as a function of wave number, harmonic number and pre-stress, are shown to give excellent agreement with numerical solutions.     

Two-dimensional solitons in a Kerr cavity

Abstract

We study the existence and nature of soliton-like localized states in a passive cavity containing a Kerr medium driven by a plane-wave input field. As the background intensity is increased, these structures are always created in pairs, for topological reasons. The smaller ‘soliton’ is always unstable, while in two transverse dimensions the larger ‘soliton’ usually collapses to a singularity or decays.     

Microprocessor-based controller for plasma position in a tokamak

A high-speed microprocessor-based controller and its application to the plasma position in the STOR-M (Saskatchewan torus-medium) tokamak is described. An adaptive control procedure based on a high-speed digital signal processor has been used to improve the controller performance. The fundamental functions of this system are the plasma dynamics modeling, the controller adjustment based on parameter optimization, and real-time feedback control. The performance of this high-speed digital controller is described, and a simulation study is discussed. Plasma position measurement using magnetic probes is described