Manufacturing of Surface Relief Structures in Moving Substrates Using Photoembossing and Pulsed‐Interference Holography

Photoembossing is a cost‐effective technique for the production of complex surface relief structures in a photopolymer film, achieved via contact‐mask exposure to UV‐light. Here, photoembossing is explored using interference holography with a CW laser and a nanosecond pulsed laser. It is shown that identical surface relief structures are produced if the photopolymer film is kept in a fixed position. In the case of a moving substrate, relief structures are only obtained with the pulsed laser and the heights of the relief structures and their shape are the same as in the static experiments. This illustrates that photoembossing in combination with pulsed laser interference holography is potentially useful in the production of large area structured films using roll‐to‐roll processes.

     

An explicit analysis of the lead time syndrome: stability condition and performance evaluation

Updating planned lead times in response to changing workload levels leads to erratic ordering behaviour, resulting in even larger variability in the workload levels and flow times. This phenomenon is called lead time syndrome, and describes the cyclic interaction between adaptive planned lead times and order sizes. Although it has been conceptually defined and intuitively accepted, formal analysis with analytical evaluation of the phenomenon has not been conducted. The objective of this paper is to provide a stronger understanding of the lead time syndrome, and to give new insights into the effects of frequently updating planned lead times. We develop a two-dimensional Markov process to model a single-item production process with orders released sensitive to the planned lead time. Using matrix-geometric methods, analytical results on the utilization level and the variability in the system are presented in relation to the frequency of updating the planned lead time. Although the average utilization level is always retained, the lead time syndrome causes an increase in the average workload level and the actual flow times of the completed orders. The variability of the planned lead time increases with the update frequency except at the utilization boundaries, where the relative effect of the update frequency diminishes.     

A trade off between emergency repair and inventory investment

In this paper we present an emergency repair model. We model a situation where failed parts arrive at a repair shop according to a Poisson process. If the stock on hand of serviceable spare parts exceeds a given emergency trigger level, the failed part is sent into normal repair. Otherwise the failed part is sent into an alternative emergency repair channel. Upon arrival failed parts are exchanged for serviceable spare parts, if available. Otherwise the demand is backordered. A backorder is filled with the first part that becomes available from either one of the repair processes. The repair times (including transportation time) are assumed to be exponentially distributed. We analyze the impact of using emergency repair on two service measures: the fraction of demand that is satisfied from stock on hand and the expected duration of a backorder. We calculate the initial stock level and the emergency trigger level that minimize the total cost for a given emergency repair rate. The proposed policy is compared with two other policies: (1) emergency repair is not used and (2) emergency trigger level is zero. We find that significant service improvements and cost reductions can be obtained by using our emergency repair policy. We also present simulation results showing that the distribution of the repair times has a negligible effect on the relevant service measures. Finally, we compare our results with the results of an emergency supply model by Muckstadt and Thomas [1] Again we observe significant cost reductions when using our policy.     

Joint effect of dopaminergic genes on likelihood of smoking following treatment with bupropion SR.

Objective: To determine the relationship between joint variation in 2 dopaminergic genes and the likelihood of nonsmoking following treatment with bupropion sustained release (SR). Design: Three hundred twenty-three participants in a bupropion SR smoking cessation effectiveness trial with 12-month follow-up were genotyped for variants of dopamine receptor gene DRD2 and dopamine transporter SLC6A3. Main Outcome Measures: Self-reported 7-day point prevalence of nonsmoking. Results: Neither genotype alone was associated with 7-day point-prevalent nonsmoking at the 12-month follow-up. However, in the presence of the DRD2 A1 allele, SLC6A3 status was significantly associated with the likelihood of nonsmoking at the 12-month follow-up (individuals with DRD2 A1+ and SLC6A3 9- were more likely to be smoking). In the absence of the DRD2 A1 allele, the association between SLC6A3 status and nonsmoking was nonsignificant. Conclusion: Although these results are suggestive, a more compelling test is needed of the hypothesis that dopaminergic gene interaction underlies, in part, the likelihood of smoking following treatment with bupropion SR. Most likely this will come from larger studies involving prospective randomization to treatment based on genotype. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modified resistivity–strain behavior through the incorporation of metallic particles in conductive polymer composite fibers containing carbon nanotubes

Eutectic metal particles and carbon nanotubes are incorporated into a thermoplastic polyurethane matrix through a simple but efficient method, melt compounding, to tune the resistivity–strain behavior of conductive polymer composite (CPC) fibers. Such a combination of conductive fillers is rarely used for CPCs in the literature. To characterize the strain‐sensing properties of these fibers, both linear and dynamic strain loadings are carried out. It is noted that a higher metal content in the fibers results in higher strain sensitivity. These strain‐sensing results are discussed through a morphological study combined with a model based on the classic tunneling model of Simmons. It is suggested that a high tunneling barrier height is preferred in order to achieve higher strain sensitivity. Copyright © 2012 Society of Chemical Industry     

Electrically conductive alumina–carbon nanocomposites prepared by Spark Plasma Sintering

Carbon nanotubes (CNTs) and carbon black were added to alumina to convert it into a good electrical conductor. Alumina–CNT and alumina–carbon black nanocomposites were fabricated by Spark Plasma Sintering (SPS). The electrical conductivity of alumina–CNT nanocomposites was found to be four times higher as compared to alumina–carbon black nanocomposites due to the fibrous nature and high aspect ratio of CNTs. The electrical conductivity of alumina–CNT nanocomposite increased with increasing grain size due to increasing density of CNTs at the grain boundaries. This effect was not observed for alumina–carbon black nanocomposite due to the particulate geometry of the carbon black.     

The sintering and grain growth behaviour of ceramic–carbon nanotube nanocomposites

The sintering and grain growth behaviour of alumina + 2, 3.5 and 5 wt.% carbon nanotubes (CNTs) and alumina + 2 wt.% carbon black nanocomposites prepared by Spark Plasma Sintering (SPS) were studied. The addition of CNTs to ceramics produces a large reduction in the sintering temperature required for their complete densification and a significant grain size refinement by a previously unreported mechanism. The CNTs form a strong entangled network around the grains, which constrains the normal and abnormal grain growth. An alumina/alumina + 2 wt.% CNT/alumina laminate structure was prepared to demonstrate directly the large grain-growth retardation effect of CNTs. These effects open up the possibility of using CNTs as a sintering aid to control the sintering behaviour and microstructures of ceramics in bulk, laminate and functionally gradient (FGM) form.