Risk and preventive factors for fatalities in All-terrain Vehicle Accidents in New Zealand

All-Terrain Vehicles (ATVs) have been used in agriculture for a few decades now. Yet despite their invaluable contribution to the productivity of the agricultural industry they are associated with a large number of accidents, many of which result in a severe or fatal outcome. The main objective of this study was to identify the risk factors for ATV-related fatal injuries in order to support the design of effective interventions. Using data held by the Department of Labour, the current study analysed 355 cases of serious harm accidents associated with ATVs including 45 fatalities. The findings suggest that injuries are more likely to occur when accidents involve any of the following: children under the age of 10; four-wheel drive ATVs; driving downhill; driving on a sealed road; driving backwards; or if the ATV rolls sideways. A fatal outcome is more likely to occur when ATV accidents end up with the vehicle rolling over and pinning the driver underneath. Fatalities were also associated with injuries to the head, neck and chest. Being employed; and/or having formal training; and/or having brakes and tyres well maintained on the ATV; and/or having no fluid load on the ATV reduced the risk for fatality. Since the likelihood of a fatal outcome was found to be related to human behaviour and ATV rollover, it is suggested that interventions should mainly address these two issues.     

Development of new models of performance correction factors of centrifugal pumps as a function of Reynolds number and specific speed

The performance characteristics of a small centrifugal pump having a specific speed of 20 min^?1 are measured when pumping two industrial Newtonian oils of viscosities 75 and 646 cSt, at value of Reynolds number near 10³. The diminishing of the performance in the case of these oils compared to water is about 50 to 80 %. It decreases with the reduction of Reynolds number. The correction factors of head, of flow rate and efficiency, are determined depending on Reynolds number, and they are compared with those obtained using the European KSB empirical method, the American method ANSI/HI and the semi-empirical method based on the analysis of power losses. For centrifugal pumps of a specific speed below 50 min^?1, the fall in performance increases with the decrease of Reynolds number and specific speed. The fall in efficiency is more important than the fall of the other performance parameters. A good agreement is obtained between experimental results and predicted results using the three above mentioned methods, with the exception of the efficiency correction factor obtained by the method of power losses analysis, in the range of Reynolds numbers between 10³ and 10⁵. The expression of correction performance factors based on the Reynolds number is universal. It allows to distinguish the ranges of correction factors falls, and to know the economic limitations of the use of centrifugal pumps. A fall of head and flow rate correction factors of over 10 % occurs at values of Reynolds number below 10⁴. But, the fall of efficiency correction factor of over 10 % occurs at values of Reynolds number below 10⁵. To facilitate to the professionals the calculation of the performance correction factors of centrifugal pumps, new models are proposed in this study according to Reynolds number and specific speed.     

On the stability of a hot layer of micropolar fluid

A critical study on the stability of a hot layer of micropolar fluid heated from below with free boundaries has been investigated. The analysis shows that the method by which the previous investigators (Datta and Sastry, and Pérez-García and Rubí) obtained the critical Rayleigh number is not justified and the final result obtained thereby is erroneous. The correct solution to the problem has been presented. Moreover, it is found that the possibility of having an overstable marginal state which was shown by one of the previous investigators (Pérez-García and Rubí) is not justified. The correct approach proves the validity of the principle of exchange of stabilities for this problem. The results show that the criteria of micropolar stability have some interesting features having no classical analogue.     

医药物流中心人工拣选作业流程优化及仿真

费用高、利润低已经成为制约我国医药物流行业发展的主要瓶颈。因此,研究降低医药物流中心人工拣选占有成本的方法对企业赢利具有重要价值。在对物流中心拣选作业流程及其影响因素分析的基础上,建立了基础模型,分别对巷道数不同拣选条目数相同及巷道数不同拣选条目数不同两种情形采用MATLAB进行了仿真,探讨了分区数与拣选条数之间的关系,并对拣选路径进行了分析,发现：1) 分区优于不分区,一般情况下,分区以2个为宜;2) 当分区超过2个后,拣选时间会逐渐增加;3) 在巷道数和拣选条目一定的情况下,分区越多越好;4) 在巷道超过96时,可以考虑分成3个拆零区。     

21st century screening experiments: What,why, and how

ABSTRACT

The primary aim of screening experiments is to identify the active factors; that is, those having the largest effects on the response of interest. Large factor effects can be either main effects, two-factor interactions (2FIs), or even strong curvature effects. Because the number of runs in a screening experiment is generally on the order of the number of factors, the designs rely heavily on the factor or effect sparsity assumption. That is, practitioners performing such experiments must be willing to assume that only a small fraction of the factors or effects are active.

Traditional screening designs such as regular fractional factorial and Plackett-Burman designs employ factors at two levels only. Though they have orthogonal linear main effects, such designs cannot uniquely identify factors with strong curvature effects.

Definitive screening designs (DSDs) have many desirable properties that make them appealing alternatives to other screening design methods. They are orthogonal for the main effects. In addition, main effects are orthogonal to all second-order effects and second-order effects are not confounded with each other. In addition, quadratic effects of every factor are estimable. For more than five factors, a DSD projects onto any three factors so that a full quadratic model in those three factors is estimable with reasonable efficiency. As a result, when three or fewer factors turn out to be important, follow-up optimization experiments may not be necessary.

All this begs the question, “Are DSDs really as good as they are advertised to be?” This article addresses this question with an even-handed comparison of the various screening approaches. It also considers the sparsity assumption common to all screening designs and provides some guidance for quantifying what effect sparsity means for both traditional screening designs and DSDs.     

Necking and radial cracking around perforations in thin sheets at normal incidence

The formation of multiple necks and cracks around perforations in ductile materials is investigated. Expressions are obtained for the number of plane-strain radial necks formed by conical penetrators (with or without starter holes in the flat target), and also by round-ended projectiles into flat targets having starter holes or, in plain targets with no starter holes, after fracture of the initial circumferential neck has detached a circular cap of material (“discing”). Likewise, expressions are derived for the number of radial cracks which form subsequently in both cases and lead to “petalling”. The number of cracks is smaller than the number of necks. Experiments seem to agree with the analyses, although accurate counting of necks in thin sheets is illusory.     

Analysis of injury severity and vehicle occupancy in truck- and non-truck-involved accidents.

The impact that large trucks have on accident severity has long been a concern in the accident analysis literature. One important measure of accident severity is the most severely injured occupant in the vehicle. Such data are routinely collected in state accident data files in the U.S. Among the many risk factors that determine the most severe level of injury sustained by vehicle occupants, the number of occupants in the vehicle is an important factor. These effects can be significant because vehicles with higher occupancies have an increased likelihood of having someone seriously injured. This paper studies the occupancy/injury severity relationship using Washington State accident data. The effects of large trucks, which are shown to have a significant impact on the most severely injured vehicle occupant, are accounted for by separately estimating nested logit models for truck-involved accidents and for non-truck-involved accidents. The estimation results uncover important relationships between various risk factors and occupant injury. In addition, by comparing the accident characteristics between truck-involved accidents and non-truck-involved accidents, the risk factors unique to large trucks are identified along with the relative importance of such factors. The findings of this study demonstrate that nested logit modeling, which is able to take into account vehicle occupancy effects and identify a broad range of factors that influence occupant injury, is a promising methodological approach.     

Meshless and wavelets based complex quadrature of highly oscillatory integrals and the integrals with stationary points

In this paper, we formulate and employ efficient and accurate methods for numerical evaluation of highly oscillatory integrals and integrals having stationary points. Two new approaches using radial basis function (RBF) and wavelets are discussed. The first approach is related to meshless method (MM) which is based on multiquadric (MQ) RBF, and is specially designed for integrands having oscillatory character. This approach stems from the Levin's method. In this procedure, the solution is obtained by solving the corresponding ODE or PDE instead of finding a numerical solution of the integration problem. In situations when the integrand has stationary points, MM fails to deliver. We opt for quadrature rules based on Haar wavelets and hybrid functions. The proposed methods are tested on a number of benchmark tests considered in available literature. The performance of the new methods is compared with the existing methods. Better accuracy of the proposed methods is reported for a variety of problems.     

A framework for collaborative planning and state-of-the-art

Inter-organizational supply chain management incurs the challenge to align the activities of all members which contribute to the value creation of a product or service offered to customers. In general, a supply chain faces the “problem” of information asymmetry, members having their own objectives and constraints which may be in conflict with those of the other members. Still, activities have to be aligned in such a way that the supply chain as a whole stays or becomes competitive while each member wins by cooperating. A number of collaborative planning schemes have been put forward in the last two decades with different assumptions and different areas of application. This paper intends to provide a framework and an overview on the state-of-the-art of collaborative planning. The criteria of the framework will allow us to position existing concepts and to identify areas where more research is needed. The focus of the literature reviewed here will be on model-based decision support at the operational planning level.     

Resonant frequencies of a fluid in containers with internal bodies

A number of problems are solved for the resonant frequencies of oscillation of a fluid in rectangular or circular containers having internal bodies such as surface or bottom-mounted vertical blocks or circular apertures in the top surface. The variation of these frequencies with the dimensions of the bodies is obtained. The method uses matched eigenfunction expansions and Galerkin expansions to derive explicit forms for the elementsS _ijof a 2×2 matrix required in the course of the solution. An approximate formula for an arbitrary-shaped body in a container which gives good agreement with the more accurate Galerkin approach is used to solve the resonant frequencies when the internal body is a submerged cylinder.     

Parallel factor analysis (PARAFAC) of target analytes in GC x GC-TOFMS data: automated selection of a model with an appropriate number of factors

PARAFAC (parallel factor analysis) is a powerful chemometric method that has been demonstrated as a useful deconvolution technique in dealing with data obtained using comprehensive two-dimensional gas chromatography combined with time-of-flight mass spectrometry (GC x GC-TOFMS). However, selection of a PARAFAC model having an appropriate number of factors can be challenging, especially at low S/N or for analytes in the presence of chromatographic and spectral overlapping compounds (interferences). Herein, we present a method for the automated selection of a PARAFAC model with an appropriate number of factors in GC x GC-TOFMS data, demonstrated for a target analyte of interest. The approach taken in the methodology is as follows. PARAFAC models are automatically generated having an incrementally higher number of factors until mass spectral matching of the corresponding loadings in the model against a target analyte mass spectrum indicates overfitting has occurred. Then, the model selected simply has one less factor than the overfit model. Results indicate this model selection approach is viable across the detection range of the instrument from overloaded analyte signal down to low S/N analyte signal (total ion current signal intensity at analyte peak maximum S/N < 1). While the methodology is generally applicable to comprehensive two-dimensional separations using multichannel spectral detection, we evaluated it with several target analytes using GC x GC-TOFMS. For brevity in this report, only results for bromobenzene as target analyte are presented. Alternatively, instead of using the model with one less factor than the overfit model, one can select the model with the highest mass spectral match for the target analyte from among all the models generated (excluding the overfit model). Both model selection approaches gave essentially identical results.     

A belief-based model for characterizing the spread of awareness and its impacts on individuals' vaccination decisions

During an epidemic, individuals'' decisions on whether or not to take vaccine may affect the dynamics of disease spread and, therefore, the effectiveness of disease control. Empirical studies have shown that such decisions can be subjected to individuals'' awareness about disease and vaccine, such as their perceived disease severity and vaccine safety. The aim of this paper is to gain a better understanding of individuals'' vaccination behaviour by modelling the spread of awareness in a group of socially connected individuals and examining the associated impacts on their vaccination decision-making. In our model, we examine whether or not individuals will get vaccinated as well as when they would. In doing so, we consider three possible decisions from an individual, i.e. to accept, to reject, and yet to decide, and further associate them with a set of belief values. Next, we extend the Dempster–Shafer theory to characterize individuals'' belief value updates and their decision-making, having incorporated the awareness obtained from their connected neighbours. Furthermore, we examine two factors that will affect individuals'' vaccination decisions: (i) reporting rates of disease- and vaccine-related events, and (ii) fading coefficient of awareness spread. By doing so, we can assess the impacts of awareness spread by evaluating the vaccination dynamics in terms of the number of vaccinated individuals. The results have demonstrated that the former influences the ratio of vaccinated individuals, whereas the latter affects the time when individuals decide to take vaccine.     

Sequential Application of Simplex Designs in Optimisation and Evolutionary Operation

A technique for empirical optimisation is presented in which a sequence of experimental designs each in the form of a regular or irregular simplex is used, each simplex having all vertices but one in common with the preceding simplex, and being completed by one new point. Reasons for the choice of design are outlined, and a formal procedure given. The performance of the technique in the presence and absence of error is studied and it is shown (a) that in the presence of error the rate of advance is inversely proportional to the error standard deviation, so that replication of observations is not beneficial, and (b) that the “efficiency” of the technique appears to increase in direct proportion to the number of factors investigated. It is also noted that, since the direction of movement from each simplex is dependent solely on the ranking of the observations, the technique may be used even in circumstances when a response cannot be quantitatively assessed. Attention is drawn to the ease with which second-order designs having the minimum number of experimental points may be derived from a regular simplex, and a fitting procedure which avoids a direct matrix inversion is suggested. In a brief appendix one or two new rotatable designs derivable from a simplex are noted.     

The evaluation of stress intensity factors in plate bending problems using the dual boundary element method

This paper discusses the application of the boundary element method for the determination of stress intensity factors in plate bending problems. A number of case studies having a range of plan forms, with different combinations of boundary conditions, crack configurations and loading conditions are presented to illustrate the effectiveness of the boundary element method for the fracture analysis of plates. Results of K_I, K_II and K_III stress intensity factors for linear elastic fracture mechanics are presented for the case studies considered. The J-integral method, the displacement extrapolation method, the quarter point approach and the stress extrapolation method have been used to determine the stress intensity factors. The boundary element results for the case studies considered in the paper have been compared with either analytical or finite element results and in all cases good agreement has been achieved.     

The Coordinate-Exchange Algorithm for Constructing Exact Optimal Experimental Designs

We describe the cyclic coordinate-exchange algorithm for constructing D-optimal and linear-optimal experimental designs. The algorithm uses a variant of the Gauss-Southwell cyclic coordinate-descent algorithm within the k-exchange algorithm to achieve substantive reductions in required computing. Among its advantages are the following: Candidate sets, which grow exponentially in the number of factors, need not be explicitly constructed or enumerated. Convex design spaces (or mixed convex by discrete design spaces) are handled directly, without the need for sophisticated nonlinear programming routines or candidate-set adjustment. For design problems having 10 or more factors, the reductions in execution time are typically two or more orders of magnitude when compared to standard candidateset- based procedures such as k exchange, yet the designs produced exhibit no loss of efficiency.     

Simulation of an integrated age replacement and spare provisioning policy using SLAM

This paper presents a SLAM simulation model for determining a jointly optimal age replacement and spare part provisioning policy. The policy, referred to as a stocking policy, is formulated by combining age replacement policy with a continuous review (s, S) type inventory policy, where s is the stock reorder level and S is the maximum stock level. The optimal values of the decision variables are obtained by minimizing the total cost of replacement and inventory. The simulation procedure outlined in the paper can be used to model any operating situation having either a single item or a number of identical items. Results from a number of case problems specifically constructed by 5-factor second order rotatory design have been presented and the effects of different cost elements, item failure characteristics and lead time characteristics have been highlighted. For all case problems, optimal (s, S) policies to support the Barlow-Proschan age policy have also been determined. Simulation results clearly indicate the separate optimizations of replacement and spare provisioning policies do not ensure global optimality when total system cost has to be minimized.     

Tensile properties and fracture behaviour of carbon fibre filament materials

Monotonic tensile properties and fracture behaviour of carbon fibre filament materials, namely single/mono- and multi-filaments (two and four filaments) as well as virgin carbon tows have been evaluated and discussed. Micro composite or single fibre approach is used in this study, which facilitated the evaluation of tensile properties and nature of fracture of carbon filament materials in a relatively short time with a large number of inexpensive trials. Tensile tests have been conducted on these filament materials at ambient temperature and laboratory air atmosphere. Load–elongation and the corresponding stress–strain plots thus obtained have been analysed to understand the tensile behaviour. The peak tensile strength of single carbon filament is found to be 3.8 GPa, and the value of the resilience obtained is 19 MJ/m³. The peak tensile strength was found to increase moderately with further increase in number of filaments. However, the value of resilience was found to increase with increase in the number of fibres, which is attributed to the controlled failure of multi-filaments. On the other hand, the tensile strength of virgin carbon tow without matrix was found to be 1.13 GPa, and the value of the fracture energy was determined to be 9.9 MJ/m³, which is nearly one fourth or even less than the corresponding values of the mono- and multi-filaments. The data obtained in the case of the virgin carbon tows were further analysed to evaluate the Weibull statistical parameters.     

Diffraction of anti-plane shear waves by two moving griffith cracks

The problem of diffraction of anti-plane shear waves by two running Griffith cracks of finite length is investigated by using the Fourier transform method. The mixed boundary value problem is reduced to a pair of triple integral equations having trigonometrical kernels. Using the finite Hilbert transform technique, a solution of the pair of triple integral equations is obtained for the small wave number. Approximate formulae are derived for the stress intensity factors. Numerical results for the stress intensity factors are displayed vs wave number for different crack lengths, velocities and angles of incidence.     

Probability Density Functions of Speckle Intensity Produced by Weak Diffusers

By using the discrete cell model for the rough surface of objects, a general expression is derived which gives the probability density function of speckle intensity produced by weak diffusers having an arbitrary phase distribution and an arbitrary cell number, N, of contributions for the formation of speckles. In some special cases, it gives the probability density functions which have been previously derived and are well known in the statistics of speckles. In the case of the small number N = 2, an analytical solution of the probability density function is obtained from that general expression. Some features on the probability density functions of speckles are discussed for the case of small roughness and small number N.     

Analysis of traffic accidents on rural highways using Latent Class Clustering and Bayesian Networks

One of the principal objectives of traffic accident analyses is to identify key factors that affect the severity of an accident. However, with the presence of heterogeneity in the raw data used, the analysis of traffic accidents becomes difficult. In this paper, Latent Class Cluster (LCC) is used as a preliminary tool for segmentation of 3229 accidents on rural highways in Granada (Spain) between 2005 and 2008. Next, Bayesian Networks (BNs) are used to identify the main factors involved in accident severity for both, the entire database (EDB) and the clusters previously obtained by LCC. The results of these cluster-based analyses are compared with the results of a full-data analysis. The results show that the combined use of both techniques is very interesting as it reveals further information that would not have been obtained without prior segmentation of the data. BN inference is used to obtain the variables that best identify accidents with killed or seriously injured. Accident type and sight distance have been identify in all the cases analysed; other variables such as time, occupant involved or age are identified in EDB and only in one cluster; whereas variables vehicles involved, number of injuries, atmospheric factors, pavement markings and pavement width are identified only in one cluster.