An analysis of flexibility and quality improvement in a quality-adjusted EOQ model with finite-range stochastic lead-time

Traditional Economic Order Quantity (EOQ) model operates under a series of highly restrictive assumptions, including, but not limited to, the assumptions of deterministic lead-time, perfect quality, and constant setup cost. Many variants of the traditional EOQ model have been developed as a result of relaxing one or more of these assumptions. These variants include a quality-adjusted EOQ model with finite-range stochastic lead-time which relaxed the deterministic lead-time and perfect quality assumptions. Utilizing the basic framework of the quality-adjusted model, the authors also considered the option of investment to improve the quality and obtained closed form relationships for the quality-adjusted and quality improvement models. This paper extends the previous work by investigating two additional models; one aimed at improving flexibility, through setup reduction, and the second considering the strategy of simultaneous investment in flexibility and quality improvement. Analytical and numerical results are presented for both models. These results indicate that significant savings over the quality-adjusted EOQ model with finite-range stochastic lead-time are realized for both the flexibility improvement and simultaneous models.     

Nonlinear behaviour of membrane type electromagnetic energy harvester under harmonic and random vibrations

In this paper, the fabrication and characterization of a vibration-based polydimethylsiloxane (PDMS) membrane type electromagnetic energy harvester (EMEH) is reported. The harvester is suitable for generating electric energy from low level sinusoidal and narrow band random vibrations. Under acceleration levels greater than 0.1 g the behaviour of the EMEH is nonlinear, exhibiting sharp jump and hysteresis phenomena during frequency sweeps. Under sinusoidal excitations (0.1–3 g), the device produces a maximum of 88.8 mV load voltage and 39.4 μW power. At a matching load impedance of 10.1 Ω and when excited at its resonant frequency of 108.4 Hz and 3 g base acceleration, it generates a power of 68.0 μW, which corresponds to a power density of 30.22 μW/cm³. The nonlinear behaviour of the EMEH is exploited to harvest energy under narrow band random excitations. At higher acceleration levels of narrow band (50–150 Hz) random excitations, the device exhibits a broadening of the load voltage spectrum in comparison to the response under relatively low acceleration levels of narrow band (5–150 Hz) random excitations. The results show that the nonlinear behaviour of the PDMS membrane can be utilized to enhance the bandwidth of the harvester under narrow band random excitations and provides a simple alternative to other bandwidth broadening methods such as beam prestress, resonance tuning, or stopper impacts.     

Performance of Tukey's and Individual/Moving Range Control Charts

This paper compares two control charts: Tukey (TCC) and individual/moving range (XmR) control charts. Both are designed to examine single observation per time period, but little is known about which one is more efficient and under what conditions. We simulated data from different distributions and examined the performance of the two control charts on these data. Performance was assessed using the of average run length, extra quadratic loss, median run length, standard deviation run length, performance comparison index, and relative average run length. Overall, TCC was more efficient than XmR, when observations had binomial, Rayleigh, logistic, lognormal, Maxwell, normal, Poisson, Weibull (with α = 10, β = 1), and Student's t (30 and 10 degrees of freedom) distributions. XmR was more efficient when observations had Student's t (with 4 degrees of freedom) and gamma (with α = 4, β = 1) distributions. These results suggest that improvement teams could reach faster conclusions if they use TCC in most common situations. Copyright © 2014 John Wiley & Sons, Ltd.     

Determination of the absolute molecular weight of a styrene–butyl acrylate emulsion copolymer by low-angle laser light scattering (LALLS) and GPC/LALLS

The application of low-angle laser light scattering (LALLS) and combined GPC/LALLS for the measurement of absolute molecular weight distribution of a styrene–butylacrylate (30/70) emulsion copolymer is discussed. From the static light scattering measurements in four different solvents, i.e., toluene, tetrahydrofuran (THF), methyl ethyl ketone (MEK), and dimethylformamide (DMF), the true weight average molecular weight (M _w) and heterogeneity parameters are determined. The apparent M _w obtained from the static measurement in THF was in good agreement with the M _w determined from the multiple solvent analysis, suggesting the validity of using THF as the mobile phase in the combined GPC/LALLS analysis.     

Active optical system for variable view imaging of micro objects with emphasis on kinematic analysis

Insufficient vision information, such as occlusion, low resolvability, and a small field of view, represent important issues in microassembly and micromanipulation. We propose an active optical system to solve problems related to insufficient vision information through the integration of robotics and optics technologies. The proposed system integrates a double-prism system and a scanning mirror system to supply a compact flexible view. The kinematics of the imaging system is analyzed based on a simplified model initially to investigate the workspace and identify the kinematic performance. A more rigorous analysis of kinematics of the system is then made based on the ray tracing method. The simulation results based on the preliminary design are provided for investigating the workspace and demonstrating the capability of the system in imaging with variable views.     

Platform Design for Customizable Products as a Problem of Access in a Geometric Space

A product platform is a set of common components, modules or parts from which a stream of derivative products can be created. Product platform design is typically performed as redesign and consolidation of existing products to create more competitive product families by reducing part variety and standardizing components. The main disadvantage of such an approach is that the benefits of product platform design are achieved only after a number of parts have been designed and manufactured, with all the associated expenditure. A number of approaches, referred to as “top-down approaches”, have been proposed recently to design the platforms since the original design of the product families. However, current top-own approaches have two major limitations: (1) they do not enable multiple levels of commonality for different components and features, and (2) they have been applied to products that are variegated in one specification, whereas products are typically variegated in multiple specifications. This paper describes a rigorous top-down approach for synthesizing product platforms that facilitates the realization of a stream of customized product variants, and which accommodates naturally multiple levels of commonality and multiple customizable specifications. The proposed approach is based on the formulation of the platform design as a problem of access in a geometric space. The proposed approach is illustrated with a case example, namely, the design of a product platform for a line of customizable pressure vessels.     

Assessment of target types and layouts in 3D laser scanning for registration accuracy

3D laser scanning technology is now widely and increasingly used in several construction tasks such as indoor mapping, project control, construction metrology and automation, development of as-built models, and resource management through scanning, data processing, and modeling stages. The accuracy of these stages affects the quality of the end product and can be improved by decreasing the errors caused by manual work processes. This paper focuses specifically on data acquisition errors caused by target setup, acquisition, and reorientation. The paper explores how different target types and target layouts affect registration accuracy. A total of twelve tests were conducted with phase-based and time-of-flight scanners in both exterior and interior scan scenes in order to assess registration errors and time inefficiencies associated with current scanning practices. The paper compares different target types (paper, paddle, and sphere) and presents the lessons learned to achieve optimal target layout design.     

Effect of machining on fracture toughness of corundum

Different machining processes such as ultrasonic machining and grinding by a diamond wheel produce varying degrees of surface damage. The amount of surface damage appeared to be related to the type of machining process. However, the degree of surface damage could not be related to the surface roughness for different machining processes. The surface damage created by the machining process can be fully or partially recovered by heat treatment subsequent to machining. The degree of recovery by heat treatment seems to be dependent on the severity of the surface damage during the machining process. Observation of the surface microcracks and determination of the fracture toughness of the material after machining or heat treatment indicated recovery of some of the microcracks during the heat treatment.