Feasibility of software-based assessment for automated evaluation of tooth preparation for dental crown by using a computational geometric algorithm.

The purpose of this study was to propose the concept of software-based automated evaluation (SAE) of tooth preparation quality using computational geometric algorithms, and evaluate the feasibility of SAE in the assessment of abutment tooth preparation for single-unit anatomic contour crowns by comparing it with a human-based digitally assisted evaluation (DAE) by trained human evaluators. Thirty-five mandibular first molars were prepared for anatomical contour crown restoration by graduate students. Each prepared tooth was digitized and evaluated in terms of occlusal reduction and total occlusal convergence using SAE and DAE. Intra-rater agreement for the scores graded by the SAE and DAE and inter-rater agreement between the SAE and DAE were analyzed with the significance level (α) of 0.05. The evaluation using the SAE protocol demonstrated perfect intra-rater agreement, whereas the evaluation using the DAE protocol showed moderate-to-good intra-rater agreement. The evaluation values of the SAE and DAE protocols showed almost perfect inter-rater agreement. The SAE developed for tooth preparation evaluation can be used for dental education and clinical skill feedback. SAE may minimize possible errors in the conventional rating and provide more reliable and precise assessments than the human-based DAE

Handbook of Traffic Control Practices for Low-Volume Roads in Indiana

The purpose of the Handbook on Traffic Control Practices for Low Volume Roads in Indiana is to provide a guide to supplement the existing Manuals on Uniform Traffic Control Devices (MUTCD ). Both the National and the Indiana MUTCDs provide general guidelines for the design, installation, and use of traffic control devices (signs, signals, and markings) on all roads and streets, but their main concern is with higher volume highways. Neither specifically addresses the operational and guidance problems associated with roads that carry fewer than 400 vehicles per day. This handbook\u27s intent is to make these low volume roads safer by fostering greater consistency in traffic control practices in Indiana. It also promotes the more economical use of the limited funds available to local government agencies that are responsible for providing traffic control, and should lead to reduced costs to users of these low volume roads. Use of this guide should help a traffic engineer determine the amount of signing that, based on available research and experience, will provide adequate safety without excessive costs. This hand book does not supercede any information contained in the two MUTCDs, but attempts to assist the traffic engineer in extending or supplementing their contents when applying them to low volume roads. This handbook should be used as a guide to the installation of traffic control devices, not as a legal basis for their use. No manual of this sort can foresee all possible situations that can occur. There is no substitute for the sound judgment of the traffic engineer. While it would be advantageous for users of this hand book to have access to a copy of the Indiana MUTCD (available from the Indiana Department of Highways), this handbook provides sufficient information and a uniform starting point on which to base that judgment. This handbook is a compilation of generally accepted practice. Chapters 3 through 9 are designed to provide the most direct, yet flexible, guidelines possible for the major topics in traffic control on low volume roads. Chapter 2 is included to aid the user in understanding his responsibility with respect to several terms mentioned in the guidelines chapters. These terms - engineering study , field investigation , and engineering judgment -- refer to the user\u27s need to verify that a specific situation is covered adequately by the guidelines and, if not, to modify those guidelines for the individual case. The National MUTCD [13] addresses this topic. Qualified engineers are needed to exercise the engineering judgment inherent in the selection of traffic control devices, just as they are needed to locate and design the roads and streets that the devices complement. Jurisdictions with responsibility for traffic control, that do not have qualified engineers on their staffs, should seek assistance from the State highway department, their county, a nearby large city, or a traffic consultant. Properly used, this hand book can form the basis for a systematic program of traffic control that protects the traveling public and government officials alike

Analysis of right-turn lane length in left-hand traffic countries at signalised intersections of urban roads

Analysis of the right turn lane length of urban roads in left-hand traffic countries, such as Australia, UK and India (left-turn lane length in right-hand traffic countries such as USA), at signalised intersections encounters two main geometric features namely, deceleration length and storage length. The literature shows that in routine practice, the deceleration length is generally estimated by using constant deceleration rate. Many researchers consider this assumption for all design speeds unrealistic as it does not reflect the influence of the pavement condition. Hence, it may be desirable to consider the pavement’s condition in terms of its longitudinal coefficient of friction in the design analysis. In regard to the storage length, a large number of the current guidelines and models estimate the storage length of right-turn lane at signalised intersections under split phase. Hence, there is a need to examine other phase types and timings and integrate the signal timing as a part of the geometric design In this thesis, two analytical expressions have been analysed for the design of deceleration length. The first expression assumes a constant deceleration rate, and the second expression employs the concept of forces on a rotating wheel in which the coefficient of longitudinal friction between a vehicle’s tyres and the road surface is considered. The calculated deceleration lengths by these two expressions were compared with the recommended values in American and Australian standards as well as with the deceleration lengths that were obtained by a recent simulation study presented in the literature. It has been found that applying a constant deceleration rate of 2.74 m/s2 in the first expression provides the values of deceleration length comparable to most guidelines and studies. The second expression highlights the importance of using the pavement design in terms of the coefficient of friction to reduce the deceleration length in the case of limited space. A MATLAB based simulation programme has been developed to provide an estimate of the right-turn lane storage length for different traffic volumes in order to avoid the problems associated with blocking and overflow of right turn vehicles in 95% of cycles. In established intersections that cannot be modified due to physical constraints, the model is flexible enough to examine different signal phase types and timings and provides other solutions to reduce overflow and/or blockage situations. The simulation model also takes into consideration the leftover queue. The model results have been compared against an available analytical method in which similar signal phases and timings were investigated. The outcomes are similar to those of the analytical model in most of the signal phase types. The simulation model provides the flexibility to estimate the right-turn lane length for different combinations of through lane and right-turn lane traffic volumes. The developed simulation model has also been validated against the field data using three parameters, namely 95th percentile of maximum queue, overflow cycle percentage, and blockage cycle percentage. Comparing with the field observations yields a level of accuracy in the range of 78%-85%. Finally this simulation model has been used to optimise the green time in the case of split phase that demonstrates a large difference in traffic volumes of two opposite approaches; this could reduce the mean wait time by up to 28%

Solid state extrusion of polymers through convergent-divergent dies

Compared with metals, polymer materials have Iow strength and stiffness. However, molecular orientation can enhance many mechanical properties of polymer materials in the direction of orientation. Studies on solid state polymer extrusion (Le. extrusion carried out at temperatures below the melting point of the polymer) through convergent dies show that it is possible to produce extrudates exhibiting a high degree of monoaxial orientation in the extrusion direction. Although the strength of these extrudates has been greatly enhanced in the orientation direction, the strength decreases in the transverse direction to the axial orientation. Biaxially oriented polymer materials, on the other hand, show increased mechanical properties in more than one direction. But so far, extrusion processes that confer orientation in more than one direction have not received much attention. The present work is concerned with the development of biaxial orientation in thick thermoplastics extrudates by extrusion through dies exhibiting simultaneously converging and diverging walls perpendicular to each other and with a cross-section area at the die entry being the same as at the exit. Four die designs are examined, known respectively as the dual-taper die, the expansion fish-tail die, the constant fish-tail die and the cross die, using polytetrafluoroethylene and ultra-high molecular weight polyethylene. Measurements of birefringence and tensile strength on sections of the extrudates have shown that a preferential orientation along the transverse direction is normally achieved with the fish-tail dies and the dual-taper die, while the extrudates obtained with the cross die were found to exhibit a cross-ply orientation pattern with a bias in the extrusion direction for outerlayers and a preferential orientation in the transverse direction for the middle layers. The mechanics of the processes has been analysed by a plasticity approach for solid state extrusion, and by using variable wall boundaries for the melt extrusion analysis. The extrusion pressure predicted by the analysis compares very well with the values measured experimentally

Fretting wear and fatigue in taper junctions of modular orthopaedic implants

Multi-component, or modular, implants have a number of advantages over monoblock implants, but also a number of disadvantages related to micromotion and fretting at the taper interface. Depending on the fretting regime, either fatigue or wear damage may occur, resulting in greatly reduced fatigue lives and the production of metallic wear debris. Current revision rates of hip implants with replaceable necks are double those with fixed necks. To improve the understanding of taper performance and identify factors that can reduce wear and fatigue damage, 3-D finite element modelling of a taper connection representing the neck-stem junction of a dual modular hip prosthesis was performed. This included evaluations of short- and long-term taper strength, wear simulations and fatigue life predictions. Wear simulations included material removal due to wear. Fatigue damage calculations were performed using the critical plane Smith-Watson-Topper and Fatemi-Socie parameters together with an isotropic, linear damage accumulation model. To facilitate fatigue calculations, a unique method of tracking a consistent set of material points was presented. Taper geometry, assembly force and the magnitude of the cyclic load were all found to affect taper performance. Increasing the assembly load reduced micromotion, but reductions in wear were offset by an increase in contact pressure. Increased loads resulted in significant increases in fatigue damage. Clinically relevant wear rates were predicted, suggesting that wear volumes produced by neck-stem tapers are similar to rates of head-neck and bearing surfaces of large head metal-on-metal total hips. Fatigue crack initiation sites were predicted to be within the taper junction, located at the edges of the wear patches in regions of partial slip. Due to the evolution of the contact and sub-surface stress/strains, the inclusion of material removal was found to be critical in the prediction of both crack initiation site and fatigue damage

A Model of Knot Shape and Volume in Loblolly Pine Trees

The shape and structure of branches attached internally to the stem (knots) for loblolly pine (Pinus taeda L.) trees were modeled. Data on knot shape were obtained from the dissection of branches taken from 34 22-yr-old sample trees growing under ten different initial spacings. A total of 341 branches located below the live crown were dissected in the radial/tangential plane. Afterward, a procedure was implemented to reconstruct the branch diameter perpendicular to the branch pith. This information was used to develop a model for representing knot shape, which assumed that the live portion of a knot can be modeled with a one-parameter equation and the dead portion by assuming a cylindrical shape. To study the variability in shape of individual knots (live portion), the model was fitted to 218 branch profiles using nonlinear mixed-effects modeling techniques. A graphical analysis indicated that the random-effects parameter was related to branch diameter. Thus, branch diameter was included as a predictor variable to reduce between-individual variability in knot shape. Reconstructed knots with smaller diameters were more cylindrical; those with larger diameters were more parabolic or conical in shape. Analytical expressions were derived for estimating the volume of knots (live/dead portions) for three types of branch conditions on simulated trees: 1) live branches; 2) nonoccluded dead branches; and 3) occluded dead branches. The knot model assumes a substantial simplification of branch morphology, but should be useful for representing knots as 3-D entities in the stems of loblolly pine trees

A hybrid prognostics approach for motorized spindle-tool holder remaining useful life prediction

The quality and efficiency of high-speed machining are restricted by the matching performance of the motorized spindle-tool holder. In high speed cutting process, the mating surface is subjected to alternating torque, repeated clamping wear and centrifugal force, which results in serious degradation of mating performance. Therefore, for the purpose of the optimum maintenance time, periodic evaluation and prediction of remaining useful life (RUL) should be carried out. Firstly, the mapping model between the current of the motorized spindle and matching performance was extracted, and the degradation characteristics of spindle-tool holder were emphatically analyzed. After the original current is de-noised by an adaptive threshold function, the extent of degradation was identified by the amplitudes of wavelet packet entropy. A hybrid prognostics combining Relevance Vector Machine (RVM) i.e. AI-model with power regression i.e. statistical model was proposed to predict the RUL. Finally, the proposed scheme was verified based on a motorized spindle reliability test platform. The experimental results show that the current signal processing method based on wavelet packet and entropy can reflect the change of the degradation characteristics sensitively. Compared with other two similar models, the hybrid model proposed can accurately predict the RUL. This model is suitable for complex and high reliability equipment when Condition Monitoring (CM) data is scarcer