Bayesian latent variable models for spatially correlated tooth-level binary data in caries research

Analysis of dental caries is traditionally based on aggregated scores, which are summaries of caries experience for each individual. A well-known example of such scores is the decayed, missing and filled teeth or tooth surfaces index introduced in the 1930s. Although these scores have improved our understanding of the pattern of dental caries, there are still some fundamental questions that remain unanswered. As an example, it is well believed among dentists that there are spatial symmetries in the mouth with respect to caries, but this has never been evaluated in a statistical sense. An answer to this question requires the analysis to be performed at subunits within the mouth, which necessitates the use of methods for correlated data. We propose a Bayesian generalized latent variable model coupled with an undirected graphical model to investigate the unique spatial distribution of tooth-level caries outcomes in the mouth. Data from the Signal Tandmobiel(?) study in Flanders, a dental longitudinal survey, are used to illustrate the methodology.     

Managing the exchange of information in product development

In the present paper, we develop a dynamic programming (DP) model of the product development (PD) process. We conceptualize product development as a sequence of decisions: whether to incorporate a piece of information that just arrived (i.e. became available) or wait longer. We utilize this formulation to analyze different situations that depend on the type, and nature of information that is exchanged: stationary versus dynamic information. We derive optimal decision rules to determine whether (and when) to incorporate for each case. An analysis of the model results in several important findings. First, we must not necessarily incorporate all available information that is related to the design activity. Specifically, once the information collection exceeds certain value, the design team should stop collecting further information. Second, only when past design work accumulates to a certain threshold value should the team include the latest information and perform rework. Large uncertainty of the information and large sensitivity of the design activity makes the incorporation of new information less likely. Finally, managerial implications are discussed with several numerical examples.     

Prioritizing replenishments of the piece picking area

Having sufficient inventories in the forward or piece picking area of a warehouse is an essential condition for warehouse operations. As pickers consume the inventory in the piece racks, there is a risk of stockout. This can be reduced by the timely replenishment of products from the bulk reserve area to the forward area. We develop and compare three policies for prioritizing replenishments for the case where order picking and replenishments occur concurrently because of time restrictions. The first policy, based on the ratio of available inventory to wave demand, reduces the number of stockouts considerably. The other two more sophisticated policies reduce the number of stockouts even more but require much more computation time, and are more costly in terms of implementation, maintenance and software updates. We present the results of implementing one of these policies in the warehouse of a large cosmetics firm.     

Optimal design of the cooling plunger cavity

An axisymmetric system of mould, glass piece, plunger and plunger cavity is considered. The state problem is given as a stationary head conduction process. The system includes the glass piece representing the heat source and is cooled inside the plunger cavity by flowing water and outside by the environment of the mould. The design variable is taken to be the shape of the inner surface of the plunger cavity. The cost functional is the second power of the norm in the weighted space L _r ² of difference of trace of temperature from given constant, which is evaluated on the outward boundary of the plunger. Existence and uniqueness of the state problem solution and existence of a solution of the optimization problem are proved.     

ALE-based 3D FE simulation of electromagnetic forming

Electromagnetic forming is a contact-free high-speed forming process. The deformation of the work piece is driven by the Lorentz force which results from the interaction of a pulsed magnetic field with eddy currents induced in the work piece by the field itself. The purpose of this work is to present a fully-coupled three-dimensional simulation of this process. For the mechanical structure, a thermoelastic, viscoplastic, electromagnetic material model is relevant, which is incorporated in a large-deformation dynamic formulation. The electromagnetic fields are governed by Maxwell's equations under quasistatic conditions. To consider their reduced regularity at material interfaces Nédélec elements are applied. Coupling takes the form of the Lorentz force, the electromotive intensity and the current geometry of the work piece. A staggered solution scheme based on a Lagrangian mesh for the work piece and an ALE formulation for the electromagnetic field is employed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Prediction of the paper path in a laser printer by finite element analysis

A conventional problem of paper handling in a page-printing printer is to design a reliable paper path. Sometimes, this also affects the printing quality. The nonlinear theory of elastica has often been used to model paper deflection shape and to predict the paper path between some guiding rollers. The present paper proposes another method that can solve this problem more efficiently. Considering a piece of paper as a nonlinear beam, finite element analysis with geometric nonlinearity and manipulating the contact gap element between paper and guiding surfaces can be used to simulate the large-deflection behavior of paper. In this paper, the paper path in the vicinity of an OPC (organic photoconductive) drum is investigated with a general purpose finite element package. The effect of the electrostatic force between the OPC drum and the paper is considered, and the deformed shape of the paper for different forces lengths is obtained. According to those results an appropriate paper guide is added for an exact paper path.     

Determination of surface singularities of a cycloidal gear drive with inner meshing

The cycloidal gear drive is widely used in industrial applications, such as gerotor pump, speed reducer, transmission apparatus and so on. In this paper, the profile of inner rotor is with equidistance to an epitrochoidal (or extended epicycloid) curve, and the mathematical model of the internal cycloidal gear with tooth difference is created by the theory of gearing. The proposed mathematical model can simulate not only gerotor pump but also cycloidal speed reducer. The design of outer rotor depends on different applications. Being applied to the speed reducer, the outer rotor will be a pin wheel (outer rotor arc teeth). Besides, for a better design of the gerotor pump, the mathematical model of the generated shape between outer rotor arc teeth will also be proposed. Lastly, a simpler dimensionless equation of undercutting will be derived from the proposed mathematical model. And a more explicit procedure to determine the feasible design region without undercutting on the tooth profile or interference between the pins will be developed and demonstrated by some numerical examples.     

Dimensionado en compresión en acero: el peso del pandeo

The verification of the slender compressed members of a structure is a well formulated and codified problem. However, the non-linearity of the design process, combined with the no linearity of the physical problem requires an iterative process to define the piece that solves a given problem. This paper demonstrates an identity relationship between seemingly different problems, based on which we develop a theoretical approach and a simple procedure to determine, without iteration and with little margin for error, the piece needed for a given problem. The paper provides a statistical model to check that the provided procedure is safe and effective in the 98% of the problems in buildings —pillars and bars from trusses—. The presented approach therefore greatly facilitates decisions in this area.     

Aplicación de métodos computacionales en la evaluación de la respuesta aeroelástica de puentes soportados por cables

The possibilities of computational methods for assessing the response of cable supported bridges under wind action are considered in this work. The main objective is to study the possibilities of substituting wind tunnel campaigns by computer based analyses, particularly at the early design stage. The preliminary proposed design for a continuous cable-stayed bridge with two main spans of 650 m and a single box girder deck has been considered as a case study. The force coefficients of the deck cross-section have been computed and the unsteady response associated to vortex-shedding has been simulated using CFD commercial software. Furthermore, an in-house piece of software has been employed to obtain the response for flutter and buffeting phenomena adopting the hybrid approach; with that purpose the experimental flutter functions of a similar box girder deck were adopted. The computational results have been validated by comparison with similar experimental results published by other researchers. It has been verified that the set of adopted methods offers reliable results with moderate costs; therefore, the proposed approach is very suitable at the early design stage of long span bridges or at conceptual design works.     

On the relaxation of nonconvex superficial integral functionals

We present a new approach to the variational relaxation of functionals of the type:

where is a continuous function with growth conditions of order p≥1 but not necessarily convex. We essentially study the case when μ is the k-dimensional Hausdorff measure restricted to a suitable piece of a k-dimensional smooth submanifold of .     

Optimisation of multi-position machines and transfer lines

A new optimisation problem for design of multi-position machines and automatic transfer lines is considered. To reduce the number of pieces of equipment, machining operations are grouped into blocks. The operations of the same block are performed simultaneously by one piece of equipment (multi-spindle head). At the studied design stage, constraints related to the design of blocks and workstations, as well as precedence constraints for operations are known. The problem consists in an optimal grouping of the operations into blocks minimizing the total number of blocks and workstations while reaching a given cycle time (productivity). A constrained shortest path algorithm is developed and tested.     

Organizational Design of Post Corporation Structure Using Fuzzy Multicriteria Decision Making

A model for organizational design of post corporation structure is developed in this paper. Alternative organization solutions have been designed taking into account the post environment characterized by private operators' competition and development of new message transmission technologies. Criteria for organizational design have been considered as numerical and uncertain linguistic variables describes by fuzzy sets. The model has been tested on a numerical example.     

An Extended Examination of Preservice Elementary Teachers' Science Teaching Self‐Efficacy

The purpose of this study was to examine programmatic factors that positively impact changes in elementary preservice teachers' teaching self‐efficacy beliefs. Specifically, it examined the impact of science methods courses, student teaching, and science content courses on elementary preservice teachers' science teaching self‐efficacy. The Science Teaching Efficacy Belief Instrument Form B was administered, using a pre/post design, to undergraduate elementary education majors in specific education and science content courses. A total of 399 responses were collected, of which 172 had matching pre/post surveys suitable for analysis. Students in the science content courses and student teaching seminar showed no significant change in either the Personal Science Teaching Efficacy (PSTE) or the Science Teaching Outcome Expectancy scales during the time they were enrolled in the classes. Significant gains in PSTE were found for students enrolled in the science methods course. The specific design of the education program and methods course may be responsible for these changes.     

Wood property relationships and survival models in reliability

We study the relationship between lumber strength properties and their visual grading characteristics. This topic is central to the analysis of the reliability of lumber products in that it underlies the calculation of structural design values. The approaches described in the paper are adaptations of survival analysis methods commonly used in medical studies. Because each piece of lumber can only be tested to destruction with one method (i.e., each piece cannot be broken twice), modeling these strengths distributions simultaneously can be challenging. In the past, this kind of problem has been solved by subjectively matching pieces of lumber, but the quality of this approach is then an issue. The objective of our analysis is to build a predictive model that relates the strength properties to the recorded characteristics. The paper concludes that type of wood defect (knot), a lumber grade status (off‐grade: yes/no), and a lumber's module of elasticity have statistically significant effects on wood strength. We find that the Weibull accelerated failure time model provides a better fit than the Cox proportional hazards model in our dataset. Copyright © 2016 John Wiley & Sons, Ltd.     

钛合金插铣过程温度场的数学建模与有限元分析

从金属切削理论出发分析了钛合金插铣过程的切削热产生机理,推导出工件的热传导方程式,并在此基础上建立钛合金插铣的数学模型,应用Galerkin有限元方法对工件的热传导方程进行推导计算,随后利用Matlab进行数值模拟,最终得到工件稳定后温度分布图.通过数值计算结果与实验结果对比,验证了有限元模型具有可靠和高精度优点.对钛合金插铣过程加工参数的优化和刀具的设计提供了重要参考依据.     

Clinical decision support system for dental treatment

BackgroundIn this research, a decision making system, based on fuzzy inference mechanism as proposed by Mamdani, is presented. Literature suggests that there is a lack of consistency among dentists in choosing treatment plan(s). So, this research work aims to facilitate the dentist decide the treatment plan(s) of the broken tooth.MethodsAn expert system based on fuzzy logic has been designed to accept inaccurate and vague values of dental signs and symptoms associated with the broken tooth. We designed a knowledge base with 60 rules and used Mamdani inference algorithm to decide the possible one or more treatment(s) and suggest the same to the dentist.ResultsThe results proposed by the system are compared with the dentists’ suggestions. The Chi-square test of homogeneity is conducted on 100 randomly generated sample cases with the help of three professional dentists. It is found that the results produced by the system are consistent with the treatment plan(s) proposed by the dentists. Chi-square value of the test is 3.843565 which is less than the critical value which is 12.592. Hence, we are unable to reject the null hypothesis that assumes the two populations are homogeneous with respect to treatments.ConclusionsThe accuracy of the proposed decision support system for the treatment of broken tooth enhances the confidence level of the dentists while making decision regarding the treatment plan(s). Simple and interactive GUI makes it easy to use.     

Effects of bearing clearance on the chatter stability of milling process

In the present study, the influences of the bearing clearance, which is a common fault for machines, to the chatter stability of milling process are examined by using numerical simulation method. The results reveal that the presence of bearing clearance could make the milling process easier to enter the status of chatter instability and can shift the chatter frequency. In addition, the spectra analysis to vibration signals obtained under the instable milling processes show that the presence of bearing clearance could introduce more frequency components to the vibration responses but, however, under both the stable and instable milling processes, the generated frequency components will not violate the ideal spectra structures of the vibration responses of the milling process, which are usually characterized by the tooth passing frequency and its associated higher harmonics for the stable milling process and by the complex coupling of the tooth passing frequency and the chatter frequency for the instable milling process. This implies that, even under the case with bearing clearance fault, the stability of the milling process can still be determined by viewing the frequency spectra of the vibration responses. Moreover, the phenomena of the chatter frequency shift and the generation of more components provide potential ways to detect the bearing clearance in machines.     

Numerical solution of the pressing devices shape optimization problem in the glass industry

In this contribution, we present the problem of shape optimization of the plunger cooling which comes from the forming process in the glass industry. We look for a shape of the inner surface of the insulation barrier located in the plunger cavity so as to achieve a constant predetermined temperature on the outward surface of the plunger. A rotationally symmetric system, composed of the mould, the glass piece, the plunger, the insulation barrier and the plunger cavity, is considered. The state problem is given as a multiphysics problem where solidifying molten glass is cooled from the inside by water flowing through the plunger cavity and from the outside by the environment surrounding the mould.The cost functional is defined as the squared \(L^2_r\) norm of the difference between a prescribed constant and the temperature on the outward boundary of the plunger. The temperature distribution is controlled by changing the insulation barrier wall thickness.The numerical results of the optimization to the required target temperature 800 ?C of the outward plunger surface together with the distribution of temperatures along the interface between the plunger and the glass piece before, during and after the optimization process are presented.     

Simple block patterns for the two-dimensional cutting problem

This paper presents an algorithm for the unconstrained two-dimensional cutting problem of rectangular pieces. It proposes the simple block (SB) pattern consisting of simple blocks. The SB pattern is defined recursively. Each cut on the stock plate produces just one simple block. A horizontal cut produces a horizontal block with width equal to that of the leftmost piece in the block. A vertical cut produces a vertical block with length equal to that of the bottommost piece in the block. The algorithm generates the optimal SB pattern recursively, and selects optimally the first piece in each block. It uses upper bound to prune some unpromising branches during the searching process. The computational results indicate that the algorithm is highly efficient in improving material utilization, and the computation time is reasonable.