A greedy gradient-simulated annealing selection hyper-heuristic

Educational timetabling problem is a challenging real world problem which has been of interest to many researchers and practitioners. There are many variants of this problem which mainly require scheduling of events and resources under various constraints. In this study, a curriculum based course timetabling problem at Yeditepe University is described and an iterative selection hyper-heuristic is presented as a solution method. A selection hyper-heuristic as a high level methodology operates on the space formed by a fixed set of low level heuristics which operate directly on the space of solutions. The move acceptance and heuristic selection methods are the main components of a selection hyper-heuristic. The proposed hyper-heuristic in this study combines a simulated annealing move acceptance method with a learning heuristic selection method and manages a set of low level constraint oriented heuristics. A key goal in hyper-heuristic research is to build low cost methods which are general and can be reused on unseen problem instances as well as other problem domains desirably with no additional human expert intervention. Hence, the proposed method is additionally applied to a high school timetabling problem, as well as six other problem domains from a hyper-heuristic benchmark to test its level of generality. The empirical results show that our easy-to-implement hyper-heuristic is effective in solving the Yeditepe course timetabling problem. Moreover, being sufficiently general, it delivers a reasonable performance across different problem domains.     

Learning market prices in real-time supply chain management

This paper proposes a model for dynamic pricing that combines knowledge of production capacity and existing commitments, reasoning about uncertainty and learning of market conditions in an attempt to optimise expected profits. In particular, the market conditions are represented as a set of probabilities over the success rate of product prices, and those prices are learned online as the market develops. The dynamic pricing model is integrated into a real-time supply chain management agent using the Trading Agent Competition Supply Chain Management game as a test framework. We evaluate the agent experimentally in competition with other supply chain agents, and demonstrate the benefits of incorporating more market data into the dynamic pricing mechanism.     

A survey of platinum hydrous oxide electrochemistry at elevated temperature: evidence for a new component in the β-deposit

Hydrous (or ) oxide. films produced on platinum in acid at room temperature usually give rise to two reduction peaks, in addition to the monolayer oxide response, on a negative sweep extending to about 0V. This has been attributed to the presence of two hydrous oxide components (designated as HO1 and HO2) in the film. It was confirmed in the present work that under more severe conditions, 3.0 m H₂SO₄ at 60°C, an additional, quite significant, peak — apparently due to the presence of a further hydrous oxide component (HO3) — may be observed. The approximate peak maximum potential values (RHE scale) were 0.4 V (HO1), 0.2 V (HO2) and 0.0 V (HO3); the E _p values are given here only as a guide: the processes involved occur under very irreversible conditions and the values vary with factors such as sweep rate, film thickness, temperature, etc. The differences in behaviour between these components is assumed to be due to factors such as the degree of aggregation and compactness in different regions of the gel-type, amorphous deposit. A brief account is given of the increasing evidence from different laboratories of unusual responses for platinum electrodes in aqueous acid solution.     

Analysis of error-correction constraints in an optical disk

The compact disk read-only memory (CD-ROM) is a mature storage medium with complex error control. It comprises four levels of Reed Solomon codes allied to a sequence of sophisticated interleaving strategies and 8:14 modulation coding. New storage media are being developed and introduced that place still further demands on signal processing for error correction. It is therefore appropriate to explore thoroughly the limit of existing strategies to assess future requirements. We describe a simulation of all stages of the CD-ROM coding, modulation, and decoding. The results of decoding the burst error of a prescribed number of modulation bits are discussed in detail. Measures of residual uncorrected error within a sector are displayed by C1, C2, P, and Q error counts and by the status of the final cyclic redundancy check (CRC). Where each data sector is encoded separately, it is shown that error-correction performance against burst errors depends critically on the position of the burst within a sector. The C1 error measures the burst length, whereas C2 errors reflect the burst position. The performance of Reed Solomon product codes is shown by the P and Q statistics. It is shown that synchronization loss is critical near the limits of error correction. An example is given of miscorrection that is identified by the CRC check.     

Accurate expressions for the LP modes in a uniform circular-core curved fiber

Accurate forms for the LP(nm) modes (n = 0 and n ≧ 2) in a uniform circular-core curved fiber are given. We show that the LP(nm) modes (n ≧ 2) are composed of two spatially orthogonal components and that, to the zeroth order, there is no special polarization axis for the LP modes in a uniform circular-core curved fiber.     

Quality and homogeneity monitoring of radiologists in the Turin mammographic screening. Comparison of the pilot phase results

The Turin mammographic screening program was designed to be carried out in several independent screening centers because of the large proportion of population involved (76,000 women aged 50 to 59 years). The first center began working in 1992 and the second center was opened in 1995. The latter center carried out an early pilot study in which 1024 women were examined to assess the homogeneity and the quality of the results. The results were then compared with European quality standards and with the results of both the pilot and the active screening periods in the first center. The results from the second center were very good as far as detection rate is concerned (7.8/1000-2.9/1000 in carcinoma < or = 1 cm). This rate is higher than the so-called "desirable" European standard. Recall rate and benign/malignant biopsy ratio were higher than the so-called "fair" European standard (recall rate: 7.1%; B/M biopsy ratio: 0.62). These results are slightly superior to those of the pilot period in the first center and slightly inferior to the results of active screening in the same center. The improvement relative to the pilot period in the first center (1991) is probably related to technical progress, such as the introduction of the double mammographic projection. The difference relative to the results from the active screening period in the first center (1992-1994) reflects different specific experience. Even though pilot periods have no statistical significance, they can be used for comparison, and in our experience they have proved, with positive results, the quality of the mammographic screening program provided to the Turin population.     

Biomechanical comparison of the dewar and interspinous cervical spine fixation techniques

STUDY DESIGN: This study evaluates and compares the stiffness of two cervical spine fixation techniques. OBJECTIVES: This biomechanical study was carried out to compare the interspinous and Dewar cervical spine fixation techniques. SUMMARY OF BACKGROUND DATA: Interspinous wiring is a commonly used method of fixation in the cervical spine. The Dewar technique is less commonly known and practiced, and clinical experience has suggested that it may be a more stable technique. METHODS: Cervical spine specimens stabilized with the interspinous and "Dewar" techniques were biomechanically tested in flexion and in torsion. Stiffness and energy absorption under moderate loads were compared. The Dewar technique uses contoured double corticocancellous iliac grafts as internal grafts/splints fixed to the spine with threaded pins and wire. The interspinous technique is a single interspinous wire loop. Eleven fresh human cervical spines were harvested from cadavers. The spines were destabilized at C4-C5 by sectioning all tissue except the anterior longitudinal ligament. Each fixation technique was applied alternatively and tested on each spine. RESULTS: In torsion testing (n = 5), the Dewar fusion was 61% stiffer than the interspinous technique (P < 0.02). Dewar: 11.3 N/mm (s.d. 4.9 N/mm) and interspinous: 8.4 N/mm (SD 3.3 N/mm). In flexion testing (n = 6), the Dewar technique was 35% stiffer than the interspinous technique (P < 0.10). Dewar: 655.4 Nmm/degree (SD 293 Nmm/degree) and interspinous: 406.8 Nmm/degree (SD 113.0 Nmm/degree). Energy absorption with the interspinous technique was greater in flexion (P < 0.10) and in torsion (P < 0.005), indicating more deformation with the interspinous technique. There was no statistically significant difference between the means of specimens tested first and those tested second independently of the fixation technique. CONCLUSIONS: These tests indicate that the Dewar cervical spine fixation is stiffer than the single interspinous wire in both flexion and particularly torsion. This project is the only biomechanical study of the Dewar technique that we are aware of, and the results support the clinical findings regarding the effectiveness of this technique.     

Intelligent planning and the design of a new risk-based,intelligent flight plan

A safe flight starts with effective performance of the pre-flight flight planning and briefing task. However, several problems related to the execution of this task can be identified. Potentially, the introduction of an improved flight plan provides an opportunity to improve the quality and availability of information provided to Flight Crew, thereby enhancing the quality of crew briefings. The proposed risk-based, intelligent flight plan is designed from the perspective of the current operational concept (e.g. fixed routes and ATC managerial role for separation), and associated airline Flight Planning and Dispatch functions. In this case, the focus is sharing information across specific airline stakeholders (e.g. Flight Operations Management and Safety functions) and Maintenance, to support a safe and efficient flight operation. Overall, the introduction of this new flight plan will result in the definition of new operational and organisational processes, along with a new way of performing the pre-flight, planning and briefing task. It is anticipated that this will impact positively on the operational and safety outcome of the flight.