Reference Vehicle Research Articles

International Standards Organization-Compatible Index for Pavement Roughness

The development of a new pavement roughness index, which is compatible to the current International Standards Organization (ISO) standard on “exposure to whole-body vibration” is described. The index was intended to be the independent variable in the future development of relationships between user cost (i.e., vehicle depreciation, repairs, discomfort and so on) and pavement roughness; hence it was named RIDE (Roughness Index for Driving Expenditure). RIDE is based on the sprung mass acceleration response of a reference vehicle to the pavement profile. It is calculated in the frequency domain by multiplying the power spectral density (PSD) of the pavement profile by the square of the transfer function of the sprung mass acceleration of the reference vehicle. The resulting sprung mass acceleration PSD is integrated over frequency to yield the root-mean-square of the sprung mass acceleration per unit length of pavement traveled. The sprung mass acceleration is shown to be the main contributor of dynamic axle loads in heavy trucks, which relate to vehicle and cargo damage and also to pavement damage.

Effect of cyclosporine A formulations on bovine corneal absorption: ex-vivo study

The purpose of this study was to evaluate, in an ex-vivo study, the absorption of cyclosporine A on bovine cornea after 24 h contact with various drug delivery systems containing 1% cyclosporine A and in comparison with an olive oil formulation as the reference vehicle for cyclosporine A. The different formulations studied were poly(acrylic acid) polymeric gels in aqueous/non-aqueous solvents, polyisobutylcyanoacrylate nanocapsules, and a combination of both formulations. The histological effects of these formulations on corneal cells after 24 h of contact were also studied. The lowest absorption rate of cyclosporine A was found using olive oil with a percent absorption of 2.52 ± 1.52% (259 ± 171 μg/g cornea). The three formulations developed for this study, nanocapsules, poly(acrylic acid) polymeric gel and nanocapsules gel showed significantly better absorption of CsA than olive oil, with a mean percent absorption of 5.81 ± 204% (621 ± 218 μg/g cornea), 609 ± 293% (651 ± 313 μg cornea) and 7.92 ± 255% (847 ± 273 μg/g cornea) respectively. As we studied the penetration of cyclosporine A into the different layers of the cornea, we observed that for all formulations, CsA remained at the corneal surface and did not penetrate the whole cornea. The histological study showed that olive oil, nanocapsules and poly(acrylic acid) gel in aqueous/non-aqueous solvents show some modifications on the cornea, contrary to the nanocapsules gel which did not indicate any toxic effect. The nanocapsule gel, with the highest percent absorption along with its margin of safety on the cornea, seems to present a new promising drug delivery system for ocular administration.

Robust control laws for wheeled mobile robots

The paper deals with feedback control of wheeled mobile robots. The proposed controller is based on a tracking scheme where the real robot tracks a fictitious reference one with equivalent kinematical properties. A solution to the parking problem is derived from the basic tracking scheme by considering a reference vehicle which converges to the desired configuration. The goal achievement is analysed by the stability of the zero equilibrium point of the tracking state error. Simulation as well as experimental results illustrate these controllers' designs. Robustness with respect to errors in the state estimation is investigated. It is defined by the existence of a compact attractive domain around the zero error. A practical computation of such a domain is a result of this paper.

An Effective Means for Implementing Wheelslip Control without a Ground Speed Sensor

SUMMARY This paper describes a method for estimating wheel slip that has proven to be effective. The method requires a longitudinal accelerometer and wheel speed sensors, although it can be enhanced by other measurements such as yaw rate and lateral acceleration. The method determines a reference speed which is closely associated with the vehicle speed, but may different. This reference speed is then used to calculate reference wheel slips which are closely associated with the actual wheel slips, but may be different. The use of reference vehicle speed and reference wheel slips allows for compensation of errors due to inaccurate estimates of tire traction properties. The actual tire forces that are generated by the controller using the reference quantities are very close to the forces the controller expects, hence, the vehicle responds as the controller expects Further, if the assumed tire traction properties are close to correct, then the reference vehicle speed and reference wheel slips become close to ...

Robust Tracking and Parking Control Laws for Wheeled Autonomous Vehicles

This paper deals with feedback control of wheeled mobile robots. The proposed results are based on a tracking sheme where the real robot tracks a fictitious reference one with equivalent kinematical properties. A solution to the parking problem is derived from the basic tracking scheme by considering a reference vehicle which converges to the desired configuration. The goal achivement is analysed by the stability of zero equilibrium point of the tracking state error.Robustness with respect to errors in the state estimation is investigated. It is defined by the existence of a compact attractive domain around the zero error.

Dynamics of aerospace vehicles at very high altitudes

Some basic questions of the flight mechanics of aerospace vehicles at very high altitudes are investigated and in some cases reviewed. In particular those of the spacecraft trajectories are considered along which the aerodynamic actions take place in a range of the Knudsen number between transition and free molecular flow. A recent physico-mathematical model is adopted in the evaluation of the aerodynamic and heat transfer coefficients. The stability characteristics are discussed of two reference vehicle configurations for which the time histories are also calculated relative to significant equilibrium conditions. In the final section of the paper the initial step of an aeroassisted orbit transfer is considered in order to evaluate the constraints due to the aerodynamic heating on this manoeuvre.

Vehicle effects on in vitro skin permeation of and stratum corneum affinity for model drugs caffeine and testosterone

The effects of Labrasol (LBS) (glycolysed ethoxylated C 8/C 10 glycerides), Labrafil (LBF) (glycolysed ethoxylated glycerides), Transcutol (TSC) (diethylene glycol monoethyl ether) and DPPG (propylene glycol dipelargonate) on the flux across excised human skin of the lipophilic testosterone (TST) and the hydrophilic caffeine (CAF) and on the affinity of the human stratum corneum for these drugs are compared taking propylene glycol (PG) and liquid petrolatum (LP) as reference vehicles. DPPG and LBF enhance CAF flux relative to PG while LBS and TSC increase the stratum corneum affinity for TST relative to LP. However, the materials tested enhance neither the flux of nor the stratum corneum affinity for both drugs with respect to either reference. On the other hand, a saturated solution of DPPG in PG enhances both properties for both drugs relative to PG. Such effects are ascribed to the ability of DPPG to interact with the lipid bilayers and to that of PG to promote DPPG penetration into stratum corneum and to create interaction sites in such a tissue.

Phase change and biodhesive systems in ocular drug delivery

The effects of chitosan hydrochloride (Ch-HCl) and of N-carboxymethylchitosan (CMCh), formulated in ophthalmic solutions, on the ocular pharmacokinetics of ofloxacin were studied in rabbits. The carboxymethylation of a chitosan of high molecular mass (1460 kDa) and deacetylation degree (89.9%) introduced 0.84 N-carboxymethyl groups per repeating unit. Aqueous solutions containing 1% (w/v) of either polymer showed a pseudoplastic rheologic behaviour, and, when instilled in rabbit eyes, produced no irritation. The kinetics of drug disappearance from tear fluid and the profiles of drug concentration in the aqueous humour versus time were determined and interpreted in the light of a pharmacokinetic model and of drug–polymer binding. Ch-HCl significantly enhanced intraocular drug penetration with respect to an isoviscous drug solution containing poly(vinyl alcohol) and to commercial ofloxacin eyedrops. This effect, which resulted in about 190% increase of the peak concentration in the aqueous, was ascribed to an increased corneal permeability. The polyanionic CMCh failed to enhance intraocular drug penetration. It nevertheless increased precorneal drug retention in virtue of its viscosity and of ofloxacin binding. Consequently, the residence time at concentrations higher than the MIC90 and the bioavailability of the antibiotic in the aqueous were increased by about 150 and 240%, respectively, with respect to the reference vehicle.

Spatial Repeatability of Dynamic Tyre Forces Generated by Heavy Vehicles

Road damage due to heavy vehicles is thought to be dependent on the extent to which lorries in normal traffic apply peak forces to the same locations along the road. A validated vehicle simulation is used to simulate 37 leaf-sprung articulated vehicles with parametric variations typical of vehicles in one weight class in the highway vehicle fleet. The spatial distribution of tyre forces generated by each vehicle is compared with the distribution generated by a reference vehicle, and the conditions are established for which repeated heavy loading occurs at specific points along the road. It is estimated that approximately two-thirds of vehicles in this class (a large proportion of all heavy vehicles) may contribute to a repeated pattern of road loading. It is concluded that dynamic tyre forces are a significant factor influencing road damage, compared to other factors such as tyre configuration and axle spacing.

Evaluation of high- and low-molecular-weight fractions of sodium hyaluronate and an ionic complex as adjuvants for topical ophthalmic vehicles containing pilocarpine

Ophthalmic vehicle; Hyaluronic acid; Pilocarpine; Miotic test; Ocular permanence test; Rabbit; Bioadhesion Summary Two low-molecular-weight fractions of sodium hyaluronate (Na-HA), denominated Hyalastin® and Hyalectin®, were investigated as potential adjuvants for ophthalmic vehicles containing pilocarpine nitrate (PiN). Tests were also performed on an ionic complex (HA/PiB) prepared from hyaluronic acid (derived from Hyalastin®) and pilocarpine base. The performance of the vehicles under study was verified by miosis and ocular retention tests carried out on albino rabbits, against a series of reference vehicles, three of which contained a high-molecular-weight fraction of Na-HA (Healon®). The group of 14 reference and test preparations exhibited Newtonian or pseudoplastic flow characteristics and encompassed a wide range of apparent viscosities (1 to 1054 mPa s). The results indicate that the HA/PiB salt and the high-MW Na-HA can significantly increase the bioavailability of pilocarpine with respect to reference vehicles of comparable viscosity: an effect that can be reasonably attributed to muco-adhesive effects. Conversely, in the present rabbit tests, the low-MW fractions of Na-HA performed poorly as adjuvants for the PiN solutions.

A system of hydrogen-powered vehicles with liquid organic hydrides

A complete system for storing and using energy in the form of liquid organic hydride is discussed. The recyclable liquid carrier is ⇄ The system is called MTH for M ethylcyclohexane, T oluene, H ydrogen.) All the technical processes proposed for this system are well established. The dehydrogenation reaction occurs in a catalytic reactor (>400°C, approx. 20 bar) on the vehicle. The hydrogenation occurs in a regional plant, servicing approx. 195 vehicles in which the hydrogen is produced by the electrolysis of water [22 MW (el)] and catalytically reacted with toluene, transforming it into methylcyclohexane. As a reference vehicle a 17 ton lorry having a 150 kW (mec) engine and an operating range of approx. 250 km per day for 250 days per year is taken. The catalytic reactor for the dehydrogenation on the vehicle has a volume of approx. 501. The tank for methylcyclohexane, the carrier of hydrogen, is approx. 7101. (equivalent: 100 kg gasoline). The cold start is based on the direct burning of toluene. The overall energy consumption is split up as 90% from hydrogen (electrical energy) and 10% from the direct burning of toluene (fossil fuel). The complete MTH system after 30 years with approx. 15,000 lorries consumes 5.4 TWh (el) per year during the night and at weekends during 235 days of ‘summer’. A seasonal storage for the rest of the year (‘winter’ approx. 115 days) is included here. The calculated economic parameters for the proposed MTH-system are as follows (prices 1981): • the cost of an equivalent 11. gasoline 0.70 SFr/1, assuming the electricity price, during summer night 0.04 SFr/(kWh); • the cost of an equivalent 11. heating oil 0.31 SFr/l (low price because of difficulties of selling during summer); • the capital cost for the system (excluding annual storage), calculated for an equivalent barrel of oil 75 000 SFr per barrel daily; • corresponding capital cost of MTH-system equals (prices 1981): ◦ approx. 26 SFr per barrel-equivalent, that is ◦ approx. 12.5 US $ per barrel-equivalent over a period of 10 years.

Wheel/Rail Vertical Forces in High-Speed Railway Operation

The nature and magnitude of the vertical forces between a railway vehicle wheel and the rail at a dipped rail joint is investigated using methods developed by British Rail. The dependence of these forces on the unsprung weight is determined and a procedure is given for the specification of new equipment to insure that the principal wheel/rail forces at higher speeds will not exceed those of a reference vehicle at conventional speeds.

Highway congestion and congestion tolls

Highway congestion is ubiquitous. We model the speed-flow relationship, identifying private and social costs, and the implied congestion toll for a number of proposed formulations. Using data for a limited access highway, we estimate these speed-flow relationships and find that flow as a quadratic function of speed fits best. The unit of observation is the individual vehicle and flow is measured in terms of the vehicles which passed a point shortly before or after the reference vehicle. Maximum possible flow occurs at 30–35 mph and the congestion toll is infinite for slower speeds. Rush-hour drivers have greater speeds for a given volume of traffic and thus congestion tolls must vary by time of day.

Extrapolation Techniques for Predicting Structural Responses to Aeroacoustic Loads

Preliminary estimates for flight-vehicle vibration environments are usually desired early in the design cycle before structural details have been formulated. Such estimates are often based upon statistical extrapolations from data measured on previous vehicles. These extrapolations are commonly performed in one of two ways; the predictions are based upon data from a single vehicle of similar design (scaling procedures), or they are based upon an average frequency response function (FRF) computed from data for one or more general vehicles. A number of specific techniques for predicting flight-vehicle vibration environments by both scaling and FRF procedures have been proposed over the years. In general, scaling techniques predict vibration levels based upon differences in excitation pressure levels and structural weight densities between the new and reference vehicle. FRF techniques vary from those that use only airborne noise level as an input parameter to more complicated functions involving structural weight density, vehicle diameter, and/or dynamic pressure. All extrapolation techniques, however, have the common advantage of requiring only gross information concerning the excitation sound pressures and structural properties for the flight vehicle of interest. The disadvantage of such procedures is accuracy. It is generally agreed that extrapolation techniques should be employed only to make preliminary vibration predictions for future vehicles. Such predictions should be refined and updated by more accurate analytical procedures and/or direct measurements as soon as sufficient information is available.

Corrugation On Railway Rails - A Linear Model For Prediction

A model is presented to predict the initial phase of the formation of corrugation. The basic idea of the model is a feedback loop between high-frequency dynamics of wheelset and track coupled by the contact mechanics and a damaging process (wear). The model allows for the prediction of local corrugation growth rates, corrugation patterns along the rail with corresponding amplitude spectra and global corrugation growth rates. Parameter studies are presented to show the influence of track and wheelset on the formation of corrugation. 1 The corrugation model Fig 1 shows the basic idea of the corrugation model following ideas of Valdivia [1] and Frederick [2]. The vehicle system dynamics are introduced into the model by a reference state which is quasi static for a linear highfrequency dynamics model. This reference state supplies reference normal and tangential forces as well as reference creepages, contact geometry and vehicle speed. These values are taken to be the point of linearization of the model. The structural dynamics are excited by the initial profile irregularities. They cause fluctuating forces and contact parameters. These fluctuating forces and contact parameters produce fluctuating wear assuming the proportionality between frictional power and wear (frictional power hypothesis). The fluctuating wear will change the profile irregularity filtering certain wavelengths to become what is known as corrugation. The initial profile irregularities are represented by Fourier series and each of the Fourier wavelengths Lk is treated separately. Regarding only the vertical and Transactions on the Built Environment vol 6, © 1994 WIT Press, www.witpress.com, ISSN 1743-3509