Empty Vehicle Research Articles

Experimental Model for Ophthalmopathy in BALB/c and Outbred (CD-1) Mice Genetically Immunized with G2s and the Thyrotropin Receptor

In an attempt to develop an animal model for thyroid-associated ophthalmopathy (TAO) we have genetically immunized BALB/c and outbred (CD-1) mice with cDNAs encoding the thyroid and eye muscle shared protein G2s and full length human thyrotropin receptor (TSHr). Firstly, BALB/c mice were immunized with cDNAs for G2s and the TSHr, alone or in tandem with cDNAs for interleukin (IL) 4 or IL12. Control mice were immunized with empty vehicle only. Sera from the great majority of experimental mice contained antibodies against a G2s fusion protein and the flavoprotein (Fp) subunit of mitochondrial succinate dehydrogenase, the "64 kDa protein", with the greatest levels being found at sacrifice (17 wk). Antibody levels in mice immunized with G2s+TSHr or G2s+IL12 were generally higher than those in mice immunized with G2s only. TSHr antibodies (TRAb), measured as TSH binding inhibition, were detected in only two mice. On histological examination of the orbits, mild edema, eye muscle fiber separation and mast cell infiltration in and around the eye muscles were found in the majority of experimental mice, but not in control mice. Splenocytes were transferred from selected G2s-immunized mice to normal syngeneic litter mates. None of the transfer mice had serum antibodies against G2s, Fp or TSHr but their orbital tissue showed the same degree of mast cell infiltration as primary mice. No major histological changes were observed in the thyroid or other skeletal muscle in either primary or transfer mice. Similar results were observed in CD-1 mice although, overall, the model was better expressed than in BALB/c mice. In these mice, serum anti-G2s antibody levels were not significantly different between the various experimental groups except at 16 wk, when they were slightly greater than in control animals. Anti-Fp antibodies were detected at 12, 14 and 16 wk, in all experimental groups, including those immunized with G2s only, and were greatest in mice immunized with TSHr alone. TRAb levels were greatest in mice immunized with both G2s and the TSHr in the presence of IL4, but not IL12. The finding of negative anti-G2s but positive anti-Fp antibodies in some CD-1 mice suggests that eye muscle damage and Fp release must have been mediated by T lymphocytes, rather than antibodies, targeting G2s or some other as yet unidentified cell membrane antigen. Histological changes in the orbit were similar to those observed in BALB/c mice although mast cell numbers were greater, in both primary and transfer mice. Overall, the greatest histological changes were observed in CD-1 mice immunized with both G2s+TSHr+IL4. None of the animals became overtly hyperthyroid or hypothyroid during the course of the study although several of the CD-1 mice had abnormal TSH or T4 levels. These results indicate that we have established a valid model for human ophthalmopathy using the novel thyroid and eye muscle expressed protein G2s, now recognized as a fragment of the winged-helix transcription factor Foxp1, and TSHr, and that G2s and the TSHr are both primary antigens in TAO. Reactivity against a TSHr-like protein may be the first event leading to ophthalmopathy in humans with TAO and experimental mice and eye muscle damage may result from autoimmunity against G2s and Fp as a result of "antigen spreading".

Optimal solution for the flow path design problem of a balanced unidirectional AGV system

An optimal flow path layout (FPL) design method is introduced as a handy tool for an automated guided vehicle (AGV) system planing stage. The problem is analysed and formulated by linear mixed-integer programming. A procedure based on the branch-and-bound depth-first search technique is proposed to solve the FPL problem. The procedure is implemented as an efficient computer program and yields an optimal solution in a small number of iterations. Using the transportation model for calculating the required and optimal flow of empty vehicles, system balance is achieved. Finally, two examples are given. A simple illustrative example is discussed to demonstrate the procedure, and a realistic FPL problem with 23 nodes, 66 arcs and nine pick-up/delivery stations is solved.

Modeling commercial vehicle empty trips with a first order trip chain model

In this paper, new mathematical formulations that depict the flow of empty commercial vehicles as a function of a given matrix of commodity flows were developed. These formulations are based on probability principles and spatial interaction concepts. The models are based on the concept of order of a trip chain, defined as the number of additional stops with respect to the primary trip, and provide a statistical link between the first order and higher order trip chains. Three different destination choice probability functions were hypothesized based on different assumptions about the destination choice process. One of these formulations included a memory component, that takes into account the amount of travel already done in the destination choice process. An example, based on data from an origin–destination study in Guatemala City, is included to show the practicality of the proposed models. The numerical results indicated a slight superiority of the formulation that takes into account the length of the previous trip. In all cases, this model outperformed the previous models which seems to be an indication of the reasonableness of its fundamental assumptions and specifically of the benefits of including a memory function. The paper also provides empirical evidence of the importance of modeling empty trips. The root mean squared error of the estimation increased between 57% and 83%, with respect to the best empty trip model, if empty trips are not explicitly modeled.

Analysis of dispatching rules of AGV systems with multiple vehicles

We study automated guided vehicle systems that contain multiple vehicles. Each vehicle transports an item from a certain point to its destination. The inter-arrival time of items to each node is assumed to be independently and geometrically distributed. Each node has an infinite buffer capacity, and thus no item is lost. The deadhead time of the empty vehicle and the transportation time of the loaded vehicle are assumed to be arbitrarily distributed. We propose two empty vehicle dispatching policies, and numerically calculate the waiting time distributions of the items for each policy using a state-space reduction technique for Markov chains. Several examples are given to demonstrate the advantages and disadvantages of each policy.

Modelling empty vehicle traffic in AGVS design

Empty vehicle traffic plays a critical role in the operating performance of automated guided vehicle systems (AGVSs). While significant research has been conducted on intelligent AGVS dispatching-which, in essence, is the management of empty vehicle traffic-research in AGVS design has sometimes ignored or simplified the role of empty vehicle traffic. In this paper, we show how empty vehicle traffic strongly influences several important AGVS design problems, such as flowpath design and vehicle requirements. We present analytical models to predict empty vehicle travel under two popular vehicle dispatching rules for systems facing stochastic trip demand. We show that using our models' estimates of empty vehicle traffic in the AGVS design process can dramatically improve the resulting system performance. We also analyse shop-floor transfer patters and find that empty traffic has a larger impact on systems with discernible trends in job movement.

Simulation Of The Operation Of Personal Rapid Transit Systems

This paper describes a computer simulation program developed by the author to study the operation of personal rapid transit (PRT) systems of any size and configuration. The control scheme is asynchronous with maneuvers commanded by wayside zone controllers. The simulation runs on a PC, is accurate in every detail, and can be used to run an operational system, which would have dualredundant computers on the vehicles, at wayside to manage specific zones, and in a central location to manage the flow of empty vehicles and to perform other system-wide functions. Some results are given.

Determination of optimal AGV fleet size for an FMS

The required number of AGVs necessary to perform a given level of material handling task in an FMS environment is determined using analytical and simulation modelling. The analytical method involves consideration of load handling time, empty travel time, and waiting and blocking time. Load handling time is computed from given system parameters. Determination of empty vehicle travel is difficult due to the inherent randomness of an FMS. Several research studies for this purpose are discussed and a new model is proposed. It entails formulation of a mixed integer programme with an objective of minimizing empty trips. The constraints are in the form of upper and lower bounds placed on the total number of empty trips starting from or ending at a load transfer station. The phenomena of vehicle waiting and blocking are also discussed. The cumulative impact of these three time estimates are then translated into an initial estimate of AGV fleet size as predicted by individual models. The method is applied to an illustrative example. Finally, simulation methodology is used to validate the initial estimates of fleet size. The results indicate that the different models either under-estimate or over-estimate the actual number of vehicles required in the system. The proposed model, though under-estimates the minimum AGV requirement, yet provides results which are close to the simulation results. Hence, it can be used as an analytical tool prior to the simulation phase of AGVS design.

Preclinical evaluation of a sterically stabilized liposome-encapsulated cisplatin in clinically normal cats

Abstract Objective To evaluate the effects of administration of a sterically stabilized liposome-encapsulated cisplatin (SSL-CDDP) to cats. Animals 4 clinically normal cats. Procedure 2 of the cats were given multiple IV injections of SSL-CDDP at a dosage of 70 mg of free CDDP equivalent/m2 of body surface area at 3-week intervals. The other 2 cats received single IV injections of identical liposome preparations not containing CDDP. Vital signs; appetite; attitude; hematologic, serum biochemical, and urinalysis findings; and thoracic radiographic views were evaluated at predetermined intervals. Results Sterically stabilized liposome-encapsulated cisplatin was well tolerated by all cats. The only significant alterations in measured variables were an increase in serum cholesterol concentration 2 days after injection, and repeatable pyrexia in the cats receiving SSL-CDDP that began 10 to 12 hours after injection and continued for 18 hours, peaking at 40.5 to 41 C. Alterations in rectal temperature were not significant in cats receiving empty liposome vehicle. Conclusions SSL-CDDP appears to be safe to administer to cats at a dosage of 70 mg of free CDDP equivalent/m2, a CDDP dose known to be therapeutic in dogs. Pyrexia, although marked, appears to be a short-term and well tolerated side effect. Clinical Relevance SSL-CDDP appears to abrogate the uniformly fatal side effects associated with administration of tumoricidal quantities of free CDDP to cats. This new formulation should allow investigation of the antitumor properties of CDDP against spontaneously arising neoplasms in cats. (Am J Vet Res 1998;59:286–289)

Simulation of underground freight transport systems

Underground logistics distribution systems seem to be a sustainable solution for environmental, congestion and space problems. In Holland many underground projects spring up like mushrooms, starting a definition phase to test the feasibility of the first underground designs. In order to gain a structured insight into the logistic dependencies, this paper defines three modelling levels of control: at vehicle level (micro), in order to control the traffic movements of the vehicles at handling areas and tubes; at transport order level (meso), in order to control the transport orders, the assignment of shipments and vehicles, and the empty vehicle stock management; and at interconnection level (macro), in order to achieve good connectivity with the schedules of the external transportation modalities.

Heavy Truck Handling Performance Analysis in Vehicle Test and Computer Simulation

Abstract The dynamic stability of heavy trucks, as spinout, jackknifing, and rollover, is highly dependent on vehicle configuration, driving maneuver, and the force and moment characteristics of tires. Increasing safety requirements on the handling performance of heavy trucks demand tools that allow a tire design engineer to predict tire influences on the tire/vehicle system dynamic behavior. The computer simulation of handling performance of vehicles offers possibilities of evaluating influences of tire design changes on handling properties in any developing stage of new tire lines. Thus, modern simulation techniques may contribute to the building and testing of tires in an early design stage. This paper presents results from a recent program of tire/vehicle system research, applying tire/vehicle testing and simulation techniques to a 40 ton truck-semitrailer combination. The goal of this work is to visualize the possibilities of state-of-the-art simulation technologies on the tire design process. Tire force and moment characteristics can be calculated from the tire layout by an advanced tire model. The tire model for this type of calculation is a multibody system. Calculated and measured dynamic tire characteristics are used for the full vehicle handling simulation in ADAMS. Extensive tire characteristic testing on the road and test stand was done to improve and validate the tire model. Vehicle handling tests as steady state circular and lateral transient response tests were done for the empty and laden vehicle with different tires to prove the vehicle model. With the use of the simulation of the tire and vehicle behavior, the tire design engineer will be able to judge tire characteristics of different variants in an early design stage. Vehicle dynamic simulation studies up to instability as spinout, jackknifing, and rollover can be performed using modern CAE methods without harming man and environment, but subjective and objective tire evaluation still remains necessary for approving and validating the predicted results.

Mexican Field Study To Obtain Basic Information on Truck Transport

A field study begun in Mexico in 1991 is described. This study has become an annual task without a deadline. The fieldwork seeks knowledge about truck traffic on Mexican roads, type of vehicles used, vehicle size and weight, tonnage transported, routes followed, type of freight moved in each case, origin and destination of movements, the packaging system for the transported freight, and whether the movement is related to domestic or to international trade. From these data, which are the core of the information gathered, other data can be obtained, such as each vehicle’s degree of compliance with current size and weight regulations, the economic value of the freight transported, age of the fleet examined, empty vehicles detected, occupancy rate of each truck (cargo tonnage/maximum payload), and fuel type used. This study is described, and some examples of the information it provides based on the collected data are provided. Also, some of the most important applications for the acquired information are enumerated.

Impact of empty vehicle flow on optimal flow path design for unidirectional AGV systems

This paper addresses the flow path design issue of automated material handling systems. We concentrate on the design of unidirectional guide path for automated guided vehicle systems. We present a modelling approach to determine the optimal flow path, which takes into account the impact of empty and loaded vehicle flows on the objective function to be minimized. We suggest a branch and bound algorithm, based on a depth-first search, which gives the excellent results in a very reduced time. The presented modelling approach exploits the structure of the problem to reduce the number of constraints by contraction and subtraction. Computational performance of this algorithm is compared with a procedure developed by Kaspi and Tanchoco and Kim and Tanchoco.

Flexible guidepath design for automated guided vehicle systems

Abstract We address the problem of unidirectional guidepath layout design for automated guided vehicle systems- A two-step layout design method to consider both loaded and empty vehicle movements is developed to guarantee a complete layout design. First, the flow path selection (FPS) problem is formulated to design guidepath layout with the objective of minimizing loaded vehicle movements. Both a mathematical model and a heuristic algorithm for FPS are presented. Since AGV guidepath layouts are used by both loaded and empty vehicles, the FPS does not guarantee a closed or complete layout design. For the case when an incomplete or unclosed layout is produced from the first step, a complementary layout design (CLD) approach to convert the incomplete layout into complete one with the consideration of empty vehicle movements is considered in the second step. A heuristic for the CLD problem is developed. An example problem is used to illustrate the whole design approach.

A Network Flow Based Heuristic for Bulk Pickup and Delivery Routing

We consider a problem in which a fleet of vehicles must be scheduled to pickup and deliver a set of orders in truckload quantities. We describe a new algorithm based on a network flow relaxation which imposes necessary conditions on the flow of empty vehicles from order delivery points to order pickup points. The network flow model provides a lower bound and a nearly feasible solution that can be made feasible with some simple heuristics. Our algorithm is fast and has performed well on a set of more than 430 test problems which include a number of real problems obtained from the Shanghai Truck Transportation Corporation. On real problems and on random problems generated using real pickup and delivery points, the algorithm consistently produces solutions within 1% of optimality.

A Self-tipping Wood-chip Dumper

Current wood-chip dumping systems consist of a platform, pivoted at one end, that is raised by expensive telescopic hydraulic cylinders with high energy requirements. A new concept for a self-tipping dumper is described that, theoretically, requires no energy to tip and empty a loaded B-Train Chip Van having a total mass exceeding 60 ts. The platform is pivoted near its centre and advantage is taken of the shift in centre of gravity between the loaded and empty vehicle to tip the platform to 60 degrees and then return it to the horizontal.

VEGETABLE DAMAGE REDUCTION WITH DECELERATORS

The handling of mechanically harvested vegetables typically results in significant impact damage (bruises, broken or splits) when falling 1.8 to 2.8 m into empty field transport vehicles. To reduce this damage, reinforced vinyl hammock designs were suspended 0.7 m above the bottom of the container on rubber elastic springs. As the vegetables filled the hammock it settled to the floor. The hammock and spring system provided cushioning and significant damage reduction compared to when vegetables directly impacted the bare floor. Field studies with the hammock showed a 65 to 80% damage reduction to the first 15 to 20 cm depth of carrots and onions and 50% reduction in pickling cucumbers and potatoes. Compared to active systems such as an air bag, passive decelerators are simple, relatively inexpensive and significantly reduce impact damage. The cost effectiveness depends on the number of fills per season. Typical frequency of use of high-lifts in carrots (30 to 35 times/day) will pay for the hammock system in 1 season. To maintain field quality for the consumer, the impact damage encountered in field harvesting and handling operations can and must be reduced.

Impact of empty vehicle flow on performance of single-loop AGV systems

With the increasing trend in the use of automated guided vehicles systems (AGVS) in manufacturing, the need for design tools becomes greater. The problem is that optimized static design models do not ensure expected performance due to the difficulty in capturing the dynamic operational characteristics of the vehicle system. This study shows that by using the single-loop guide path configuration some of the dynamic features of the system, like the impact the empty vehicle flow has on the system's performance, is reduced. Thus, a more reliable prediction of system performance is achieved

Tightened analytical bounds on the impact of dispatching rules in automated guided vehicle systems

Rule-specific formulations of the expected volume of empty travel for vehicle recirculation are developed for random and distance-minimizing/maximizing dispatching rules used in automated guided vehicle systems. These formulations are also used in developing upper and lower bounds on the volume of empty vehicle travel associated with other types of dispatching rules. It is shown that these bounds are significantly tighter than those reported in previous literature. Example problems are used to illustrate the bounding procedures.

A Model for Fleet Sizing and Vehicle Allocation

There are important interactions between decisions on sizing a vehicle fleet and decisions on utilizing that fleet. A model is formulated to optimize both sets of decisions simultaneously under dynamic and uncertain conditions. A network approximation to this model is presented and a solution procedure proposed. The convergence behavior of the solution procedure and the potential consequences of using simpler models to solve the fleet sizing and vehicle allocation problem are illustrated using several hypothetical problems. We conclude that this model is useful in identifying good strategies for the sizing of vehicle fleets and for the allocation of empty vehicles.

Models for multimode multicommodity location problems with interdepot balancing requirements

We present the problem of locating vehicle depots in an intercity freight transportation system with the objective of satisfying client demand for empty vehicles, while minimizing depot opening and operating costs, bidirectional client-depot transportation costs, as well as the costs of the interdepot movements necessary to counter the unbalancing of demand. We propose a class of models which has the form of a two-echelon multimode multicommodity location formulation with interdepot balancing requirements. We analyse the models and their properties to determine their underlying structure and characteristics to be used in subsequent algorithmic developments.