Integrated component scheduling models for chip shooter machines

This paper focuses on minimizing printed circuit board (PCB) assembly time for a chipshootermachine, which has a movable feeder carrier holding components, a movable X–Y table carrying a PCB, and a rotary turret with multiple assembly heads. The assembly time of the machine depends on two inter-related optimization problems: the component sequencing problem and the feeder arrangement problem. Nevertheless, they were often regarded as two individual problems and solved separately. This paper proposes two complete mathematical models for the integrated problem of the machine. The models are verified by two commercial packages. Finally, a hybrid genetic algorithm previously developed by the authors is presented to solve the model. The algorithm not only generates the optimal solutions quickly for small-sized problems, but also outperforms the genetic algorithms developed by other researchers in terms of total assembly time.

Component scheduling for chip shooter machines: a hybrid genetic algorithm approach

A chip shooter machine for electronic component assembly has a movable feeder carrier, a movable X–Y table carrying a printed circuit board (PCB), and a rotary turret with multiple assembly heads. This paper presents a hybrid genetic algorithm (HGA) to optimize the sequence of component placements and the arrangement of component types to feeders simultaneously for a chip shooter machine, that is, the component scheduling problem. The objective of the problem is to minimize the total assembly time. The GA developed in the paper hybridizes different search heuristics including the nearest-neighbor heuristic, the 2-opt heuristic, and an iterated swap procedure, which is a new improved heuristic. Compared with the results obtained by other researchers, the performance of the HGA is superior in terms of the assembly time. Scope and purpose When assembling the surface mount components on a PCB, it is necessary to obtain the optimal sequence of component placements and the best arrangement of component types to feeders simultaneously in order to minimize the total assembly time. Since it is very difficult to obtain the optimality, a GA hybridized with several search heuristics is developed. The type of machines being studied is the chip shooter machine. This paper compares the algorithm with a simple GA. It shows that the performance of the algorithm is superior to that of the simple GA in terms of the total assembly time.

A genetic algorithm approach to optimising component placement and retrieval sequence for chip shooter machines

A chip shooter machine in printed circuit board (PCB) assembly has three movable mechanisms: an X-Y table carrying a PCB, a feeder carrier with several feeders holding components and a rotary turret with multiple assembly heads to pick up and place components. In order to get the minimal placement or assembly time for a PCB on the machine, all the components on the board should be placed in a perfect sequence, and the components should be set up on a right feeder, or feeders since two feeders can hold the same type of components, and additionally, the assembly head should retrieve or pick up a component from a right feeder. The entire problem is very complicated, and this paper presents a genetic algorithm approach to tackle it.

On-chip immunoprecipitation for protein purification

Immunoprecipitation (IP) is one of the most widely used and selective techniques for protein purification. Here, a miniaturised, polymer-supported immunoprecipitation (µIP) method for the on-chip purification of proteins from complex mixtures is described. A 4 µl PDMS column functionalised with covalently bound antibodies was created and all critical aspects of the µIP protocol (antibody immobilisation, blocking of potential non-specific adsorption sites, sample incubation and washing conditions) were assessed and optimised. The optimised µIP method was used to obtain purified fractions of affinity-tagged protein from a bacterial lysate.

DNA chip designed antisense oligodeoxynucleotides targeting EGFR MRNA for brain tumour therapy

Glioblastoma multiforme (GBM) is a malignant brain tumour for which there is currently no effective treatment regime. It is thought to develop due to the overexpression of a number of genes, including the epidermal growth factor receptor (EGFR), which is found in over 40% of GBM. Novel forms of treatment such as antisense therapy may allow for the specific inhibition of aberrant genes and thus they are optimistic therapies for future treatment of GBM. Oligodeoxynucleotides (ODNs) are small pieces of DNA that are often modified to increase their stability to nucleases and can be targeted to the aberrant gene in order to inhibit it and thus prevent its transcription into protein. By specifically binding to mRNA in an antisense manner, they can bring about its degradation by a variety of mechanisms including the activation of RNase H and thus have great potential as therapeutic agents. One of the main drawbacks to the utilisation of this therapy so far is the lack of techniques that can successfully predict accessible regions on the target mRNA that the ODNs can bind to. DNA chip technology has been utilised here to predict target sequences on the EGFR mRNA and these ODNs (AS 1 and AS2) have been tested in vitro for their stability, uptake into cells and their efficacy on cellular growth, EGFR protein and mRNA. Studies showed that phosphorothioate and 2'O-methyl ODNs were significantly more stable than phosphodiester ODNs both in serum and serum-free conditions and that the mechanism of uptake into A431 cells was temperature dependent and more efficient with the use of optimised lipofectin. Efficacy results show that AS 1 and AS2 phosphorothioate antisense ODNs were capable of inhibiting cell proliferation by 69% ±4% and 65% ±4.5% respectively at 500nM in conjunction with a non-toxic dose of lipofectinTM used to enhance cellular delivery. Furthermore, control ODN sequences, 2' O-methyl derivatives and a third ODN sequence, that was found not to be capable of binding efficiently to the EGFR mRNA by DNA chip technology, showed no significant effect on cell proliferation. AS 1 almost completely inhibited EGFR protein levels within 48 hours with two doses of 500nM AS 1 with no effect on other EGFR family member proteins or by control sequences. RNA analysis showed a decrease in mRNA levels of 32.4% ±0.8% but techniques require further optimisation to confirm this. As there are variations found between human glioblastoma in situ and those developed as xenografts, analysis of effect of AS 1 and AS2 was performed on primary tumour cell lines derived from glioma patients. ODN treatment showed a specific knockdown of cell growth compared to any of the controls used. Furthermore, combination therapies were tested on A431 cell growth to determine the advantage of combining different antisense approaches and that of conventional drugs. Results varied between the combination treatments but indicated that with optimisation of treatment regimes and delivery techniques that combination therapies utilising antisense therapies would be plausible.

The influence of cutting tool geometry upon aspects of chip flow and tool wear:a theoretical, three dimensional examination of the cutting geometry and the shape of the twist drill

This work is undertaken in the attempt to understand the processes at work at the cutting edge of the twist drill. Extensive drill life testing performed by the University has reinforced a survey of previously published information. This work demonstrated that there are two specific aspects of drilling which have not previously been explained comprehensively. The first concerns the interrelating of process data between differing drilling situations, There is no method currently available which allows the cutting geometry of drilling to be defined numerically so that such comparisons, where made, are purely subjective. Section one examines this problem by taking as an example a 4.5mm drill suitable for use with aluminium. This drill is examined using a prototype solid modelling program to explore how the required numerical information may be generated. The second aspect is the analysis of drill stiffness. What aspects of drill stiffness provide the very great difference in performance between short flute length, medium flute length and long flute length drills? These differences exist between drills of identical point geometry and the practical superiority of short drills has been known to shop floor drilling operatives since drilling was first introduced. This problem has been dismissed repeatedly as over complicated but section two provides a first approximation and shows that at least for smaller drills of 4. 5mm the effects are highly significant. Once the cutting action of the twist drill is defined geometrically there is a huge body of machinability data that becomes applicable to the drilling process. Work remains to interpret the very high inclination angles of the drill cutting process in terms of cutting forces and tool wear but aspects of drill design may already be looked at in new ways with the prospect of a more analytical approach rather than the present mix of experience and trial and error. Other problems are specific to the twist drill, such as the behaviour of the chips in the flute. It is now possible to predict the initial direction of chip flow leaving the drill cutting edge. For the future the parameters of further chip behaviour may also be explored within this geometric model.

Knowledge integration for analyzing ChIP-seq

To capture the genomic profiles for histone modification, chromatin immunoprecipitation (ChIP) is combined with next generation sequencing, which is called ChIP-seq. However, enriched regions generated from the ChIP-seq data are only evaluated on the limited knowledge acquired from manually examining the relevant biological literature. This paper proposes a novel framework, which integrates multiple knowledge sources such as biological literature, Gene Ontology, and microarray data. In order to precisely analyze ChIP-seq data for histone modification, knowledge integration is based on a unified probabilistic model. The model is employed to re-rank the enriched regions generated from peak finding algorithms. Through filtering the reranked enriched regions using some predefined threshold, more reliable and precise results could be generated. The combination of the multiple knowledge sources with the peaking finding algorithm produces a new paradigm for ChIP-seq data analysis. © (2012) Trans Tech Publications, Switzerland.

The influence of twist drill design on rigidity and chip disposal

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