Stress and Deformation Analysis of Cylinder-Crown Integrated Hydraulic Press with Large Capacity

Cylinder-crown integrated hydraulic press( CCIHP) is a new press structure. The hemispherical hydraulic cylinder also functions as a main portion of crown,which has lower weight and higher section modulus compared with the conventional hydraulic cylinder and press crown. In order to design cylinder-crown integrated hydraulic press with large capacity, the theoretical design of hemispherical hydraulic cylinder was first proposed,and the structural parameters of 150 MN CCIHP were listed. Then the simulation was carried out to analyze the stress and deformation of CCIHP,and weight comparison was conducted between CCIHP and conventional press. It is shown that the weight reduction for hydraulic cylinder and press crown is about 20% compared with that for conventional press,and the stress and deformation are both within the range of constraints including strength and stiffness conditions. It is possible to manufacture cylinder-crown integrated hydraulic press with large capacity.

Numerical Simulation of Failure during Cylindrical Cup Hydrodynamic Deep Drawing

In this paper, a method to combine the mathematical analytic equation and general FEM software has been applied in the simulation of hydrodynamic deep drawing (HDD) cylindrical cup, also the failure types such as fracture and wrinkling are studied and solved. The simulated results are coincided with experimental results.

A Comparison of Floating Car vs.Loop Detector Estimated Freeway Travel Time Delay

Floating car-and loop detector-based methods are two different types of methods frequently used to collect travel time delay information across a freeway network.Sometimes,it is necessary to use them jointly to achieve the necessary freeway network coverage,due to the high labor costs for the floating car-based method and the indispensability of sufficient network instrumentation for the loop detector-based method.For example,both floating car-and loop detector-based methods were once used in the Highway Congestion Monitoring Program in the California Department of Transportation.It is therefore necessary to evaluate whether these two types of methods estimate similarly in terms of total travel time delay.To this end,corresponding delay information estimated using both types of methods from 37 freeway segments in the Greater Sacramento Area were collected and compared.It was found that these two types of methods do not estimate similarly in terms of total segment travel time delay.The mean absolute relative difference(MARD)can be as high as 78%,especially when delay is defined using a lower reference speed,such as 56 km/h.However,in terms of total segment travel time,the loop detector and the modified floating car method estimated similarly.The MARD is 19%.It was also found that the estimation from the different methods did correlate fairly well,which provides a means of conversion when different methods are used to monitor the total delay across a freeway network.As a spin-off,it was also found that a 1.5 km spacing of loop detectors is sufficient to achieve the 19%MARD as compared with the modified floating car method in terms of total travel time estimation.

A Discussion on the Current MUTCD Standards on Traffic Control Signals for Freeway Entrance Ramps

In Section 4I.02 of the newly published Manual on Uniform Traffic Control Devices(MUTCD),standards were specified for the placement of signal heads for traffic control signals at freeway entrance ramps,or ramp meters.For simultaneous operations,i.e.when ramp control signals are operated such that green signal indications are always displayed simultaneously to all of the lanes on the ramp,a minimum of two signal faces per ramp shall face entering traffic.For staggered operations,i.e.the ramp control signal are operated such that green signal indications are not always displayed simultaneously to all of the lanes on the ramp,one signal face shall be provided over the approximate center of each separately-controlled lane.Based on a nation-wide survey,it was realized that the two standards did not fully reflect the state-of-the-practice with respect to ramp metering operations.Due to the lack of significant conflicting movements at ramp meters,for any on-ramp lane,a minimum of one overhead mounted,or one upper and one lower roadside-mounted signal face is sufficient to control the metering operations.The minimum necessary number of signal faces changes according to the total number of lanes,how the signal faces are mounted(overhead or roadside mounting),and how the meters are operated(simultaneous or staggered).Suggestions are made to revise the two standards to better reflect the current nation-wide practices,and better consider the specific operational needs for ramp meters.

Determination of Sight Distance on a Combined Crest and Circular Curve in a Three Dimensional Space

The sight distance(SD)on a two-dimensional(2-d)curve,namely,a vertical curve or a horizontal curve,has been well understood and documented for roadway geometric design in literature.In reality,three-dimensional(3-d)curves can be found along ramps,connectors,and often mountain roads.The sight distance on these 3-d curves,which may vary with driver’s location,has not been tackled in literature on an exact analytic setting.By integrating human-vehicle-roadway interaction,the formulas for computing the SD on a 3-d curve are derived the first time on an analytic framework.The crest curve SD that has been used in various literatures,can be deduced from these derived formulas as special limiting cases.Practitioners can easily apply theses userfriendly formulas or equations on a Microsoft Excel spread sheet to calculate 3-d SD on a roadway with sufficient roadside clearance.In addition,this framework can be extended easily to cope with various scenarios in which obstacles partially blocking driver’s sight are present in a roadway environment.

Coordinated Ramp Metering and Intersection Signal Control

The operations of freeway ramp metering and urban traffic network signal control are independent in most areas.Such situation may cause some conflict between traffic streams of the two subsystems,or,at least,their dynamic interactions have not been taken into account from an overall system viewpoint.Traffic performance can be improved if the controls of these two sub-networks are integrated.This paper proposes a novel signal control strategy for the feeding intersection and a coordination strategy for integrating it with the corresponding freeway onramp metering.UP ALINEA with queue-overwrite is used for the ramp metering.A signal optimization,which takes into account the available ramp space and traffic demand,is developed for intersection signal control.A calibrated micro-simulation is used to compare the proposed control/coordination strategies and current control plans in the field.Simulation result shows that,even though the overall system performance only gets a marginal improvement,intersection delay reduces significantly.

An Evaluation of Ramp Control Signal Head Placement Based on Motorist’s Cone of Visions

Roadside mounted ramp control signals have one upper head,and one lower head in California.The upper head is intended for use by the approaching motorists,while the lower one for use by the stopped motorists.Complaints have been received regarding the visibility of these signal heads.The evaluation presented in this paper is to mathematically analyze the visibility of these signal heads on a tangent roadway alignment based on satisfactory motorists’cones of vision.Roadway design,signal placement,and driver characteristics are integrated into one analytic framework.The results indicated that the horizontal satisfactory cone of vision controls the placement design.To meet the 20 degree satisfactory horizontal cone of vision as specified by the Manual on Uniform Traffic Control Devices(MUTCD),a ramp control signal head has to be placed a minimum of 13.3 m downstream of the limit line.

Determination of Onramp Weaving Length for Resolving Merging Dilemma

It is physically known that onramp merging may turn out to be difficult if the onramp(weaving/merging)length is too short because a driver under certain driving circumstances may find that either merging ahead or merging behind a neighboring vehicle on the adjacent highway lane cannot be completed.Various existing guidelines or design manuals provide no clear physical understanding and explanations to the design onramp weaving length but often based on evolved empirical experiences.By integrating human factors,vehicle dynamic characteristics,roadway surface condition,and the onramp weaving design into a single unified analytic framework,the onramp length required for a driver to merge into the highway traffic successfully is determined exactly with formulas and physical solutions to avoid the merging dilemma and enhance driving safety at highway interchanges.The design onramp weaving length is examined and evaluated with various foreseeable merging scenarios and physical examples.This analytic framework sheds light on the understanding of the onramp weaving the first time strictly on a physical human-vehicle-roadway interaction setting.Practitioners can easily apply these user friendly formulae and equations derived from the unified framework to calculate the onramp weaving length to resolve the merging dilemma and enhance driving safety for any highway interchanges.

Ramp Metering Status in California

The purpose of this paper is to provide an update of the major improvement in terms of ramp metering design and operations in California.These updates include ramp metering policies,ramp metering development plans,ramp metering design manual,and ramp metering and system management initiatives.

Integrating Visibility,Parking Restriction,and Driver’s Field View for Enhancing Pedestrian Crossing Safety

Pedestrians at a marked but unsignalized pedestrian crossing(Ped-Xing)must be made visible to drivers in the approaching traffic at a sufficient distance away from the crossing,and this distance is needed for stopping a vehicle before the leading Ped-Xing edge to avoid a potential traffic collision.In this paper,an exact analytic framework is established to integrate driver’s field view,driver’s perception-reaction,lighting condition,and parking restriction at a Ped-Xing for enhancing traffic operational safety.The size of the no parking zone by the Ped-Xing is determined exactly using equations derived from this framework.Additionally,this study sheds the light on mid-block Ped-Xing installation,which should be discouraged if parking is permitted alongside a street.Furthermore,additional visibility improvement measures at the unsignalized Ped-Xings may be needed for enhancing safe traffic operations at the crossings.

Deriving Sight Distance on a Compound Sag and Circular Curve in a Three Dimensional Space

Insufficient roadway sight distance(SD)may become a contribution factor to traffic collisions or other unsafe traffic maneuvers.The sight distance(SD)for a two-dimensional(2-d)sag or circular curve has been addressed in detail in various traffic engineering literatures.Although three-dimensional(3-d)compound sag and circular curves are often found along ramps,connectors,and mountain roads,the sight distances for these compound curves are yet to be analyzed on an exact analytic setting.By considering human-vehicle-roadway interaction,the formulas for computing the SD on a 3-d curve are derived the first time on a unified analytic framework.The 2-d sag curve SD can also be deduced from these derived formulas as special limiting cases.Practitioners can easily program these formulas or equations on a user-friendly Microsoft Excel spread sheet to calculate 3-d SD on most roadways with roadside clearance.This framework can be extended to estimate SD on roadways with obstacles partially blocking vehicle headlight beams.

Ramp Metering Influence on Freeway Operational Safety near On-ramp Exits

Ramp metering has been widely installed in urban areas where congestion on a freeway or an expressway may occur recurrently during weekday peak periods to enhance mainline throughput and reduce system-wide delay.These operational benefits may also help reduce vehicular emissions and improve air quality in urban areas.However,the impact on traffic safety due to ramp metering hasn’t been explored in details before.Supported by physical understanding and arguments,we characterize the ramp metering influence on freeway safety by examining vehicular collisions near on-ramp exits within the ramp meter operating hours before and after the activation of the ramp metering.Collisions for a sample of 19 operating ramp meters along several freeways in northern California were collected and organized to show that ramp metering can help reduce freeway collisions at the vicinity of on-ramp exits.It was found that the average reductions on freeway collisions in the vicinity of an on-ramp exit are around 36%.Although most of the reduced collisions belong to the property damage only category,a 36%reduction shows the significant safety benefit of ramp metering.The traffic congestion induced by each collision,especially during peak hours when ramp metering is in operation,could last for an hour or two.Consequently,ramp metering must be contributing to the reduction of non-recurrent congestion in addition to mitigating recurrent congestion,which is better documented.This study strongly supports the implementation of ramp metering in California.

Queue Storage Design for Metered On-Ramps

Queue storage at a metered freeway on-ramp is an essential design element for metered on-ramps to prevent on-ramp queue from extending beyond on-ramps.In this paper,various existing methodologies that are used to size the queue storage at metered on-ramps were first reviewed.It was found that queue storage sized using 7%of peak hour on-ramp demand is widely accepted in practice.A limited dataset collected in California helps provide some reality check for this method.It is recommended that queue storage be recognized as an indispensable design element at metered on-ramps,and detailed sizing guidance be developed in the highway geometric design policy of the American Association of State Highway and Transportation Officials(AASHTO).

The Weaving Length Limit for Short Free Onramps

Onramp merging may be difficult if the onramp weaving/merging length is too short because a driver may find that even merging behind a neighboring large truck on the adjacent outside lane may not be completed safely.Because of insufficient weaving length for onramp acceleration,a slow merged vehicle may be rear-ended by a following vehicle on the outside lane when speed differential between the onramp vehicle and the following vehicle is relatively high.Nevertheless,short onramps at occasions are designed and built when right of way is constrained possibly by a variety of issues.The design onramp weaving length hasn’t been well explained physically in various existing guidelines or design manuals.Recently,a design paradigm,where human factors,vehicle dynamics,tire-road friction,and the onramp merging scenarios are integrated into a single framework,has been developed to resolve this merging difficulty.In this paper,the lower limit recommended for onramp weaving length needed for a driver to merge into the freeway traffic successfully is determined based on the physical solutions derived from the paradigm and a physical constraint for avoiding potential rear-end collisions between the slow merged vehicle and the following vehicle on freeway.This weaving length limit sets the minimal weaving length for safer free onramp merging and guides the practitioners/designers who encounter design situations where freeway right of way at onramp is limited.

Estimate Freeway Exit Sign Locations

Considering that a driver decides to exit a highway upon seeing the guide sign upstream of an exit,subsequently the driver in an inside lane or the middle lanes must move onto the outside lane prior to exiting.The concern is whether the driver can accomplish this task safely and smoothly.It is apparent that an upstream exit sign cannot be placed too close to an exit or too far beyond several exits upstream.The MUTCD recommends that the sign should be placed 1 mile and 2 miles upstream of an exit without explaining the reasons for selecting the 1 mile distance.By integrating driver decisions,vehicle acceleration characteristics,tire-road traction into a single analytic framework,the location upstream of an exit where an exit sign should be installed is determined for a driver to get off at the right exit successfully.Practitioners can easily apply these user friendly formulae and equations derived from the framework to compute the required distance‘D’between a highway exit and an upstream exit sign for guiding drivers to exit the highway safely.Additionally,parameters for these formulae can be adjusted to resemble various exiting scenarios.

The Sight Distance Issues with Retrofitted Single-Lane HOV Facilities

It is well-known that obstruction inside a highway horizontal curve will lead to impaired sight distance.Highway alignment design standards in terms of the minimum horizontal curve radius are specified to allow for adequate stopping sight distance at given design speeds.For a singlelane HOV facility,inside curve obstruction may occur no matter when the facility curves to the left(per travel direction)or right.A unique situation that calls for special attention is that the adjacent mixed-flow lane traffic,once queued,may become sight obstruction.Calculations indicated that such obstruction may govern the minimum curve radius design as long as the left shoulder is not less than 0.92 m,when the HOV lane is contiguous to the mixed-flow lanes.Such governance may necessitate design speed reduction,horizontal and cross-section design adjustment,or both.

Facile fabrication of core-shell Ni3Se2/Ni nanofoams composites for lithium ion battery anodes

Due to the highly porous structure,large specific surface area,and 3 D interconnected metal conductive network,nanoporous metal foams have attracted a lot of attention in the field of energy conversion and storage,especially lithium-ion batteries,which are ideal for current collectors.In this work,we develop a facile approach to fabricate core-shell Ni3Se2/Ni nanofoams composites.The Ni3Se2/Ni composites make full use of both the advantages of metal conductive network and core-shell structure,resulting in a high capacity and superior rate performance.In addition,the composites can be directly converted into electrode by a simple mechanical compression,which is more convenient than traditional casting method.What’s more,this material and its structure can be extended to other devices in the field of energy conversion and storage.