Computational complexity of the landscape I

We study the computational complexity of the physical problem of finding vacua of string theory which agree with data, such as the cosmological constant, and show that such problems are typically NP hard. In particular, we prove that in the Bousso-Polchinski model, the problem is NP complete. We discuss the issues this raises and the possibility that, even if we were to find compelling evidence that some vacuum of string theory describes our universe, we might never be able to find that vacuum explicitly. In a companion paper, we apply this point of view to the question of how early cosmology might select a vacuum.Comment: JHEP3 Latex, 53 pp, 2 .eps figure

Researching the development of problem-solving skills in undergraduate students and the effect of cognitive factors on performance

Solving problems is the motivating force behind many scientific endeavours. A student’s ability to solve problems is a key to their academic success. Problem-solving skills developed during a degree course are of significant value to graduate employers and therefore need to be valued significantly by educators and learners. This thesis describes the investigation into the factors that influence undergraduate chemistry students’ abilities to develop the problem-solving skills they require for success in their undergraduate studies and beyond.Quantitative data was gathered from chemistry undergraduates for three cognitive variables thought to influence academic performance. Context-rich open-ended problems were developed in order to assess students’ ability to solve more complex problems. Performance data was gathered from open-ended problem-solving sessions alongside performance data from assessments within a chemistry degree course, including final degree scores. The quantitative data was used to identify any relationships between the students’ cognitive abilities and academic performance.Qualitative research investigated the variety of approaches students take towards solving open-ended problems and also gathered data on students’ attitudes towards and experiences of the use of context-rich open-ended problems.The results show that chemistry students’ mental capacities and disembedding abilities have an impact upon their ability to solve complex open-ended problems. The skills required to solve complex open-ended problems were identified as being different skills to those required to solve the algorithmic problems found to be common elements of assessments used within undergraduate chemistry degrees.The qualitative research revealed details of students’ approaches to open-ended problem-solving and a shift in attitudes towards a more positive view of such activities. Approaches to problem-solving were identified as novice, transitional and expert. Students were also found to be able to reflect upon their learning experiences. They enjoyed the experiences and saw the value of them despite finding them challenging.The implications of the findings are discussed and recommendations for further work are made

Statistical process control for high precision deep drawn sheet metal parts

In today\u27s world, industrial expertise has come to be judged in terms of the quality of the product. Good quality has become the ultimate aim in a manufacturing environment, which leads to many innovations for ease in the inspection of parts. In considering a metal working company like Hudson Tool & Die Company, a study of the various operations and the application of Statistical Process Control to the forming operations is performed using STORM software. Important characteristics have been carefully studied with regards to metal forming like uniform metal thickness, radius of the bend, depth of the drawing operation. In-depth analysis was performed on the pattern, and the cause of the variations. Various control charts such as average chart, range chart and p chart were obtained and different processes were studied. Computer aided quality control is fast becoming a standard in the manufacturing world. Non-contact gaging, coordinate measuring machines, and automatic conversion of the data into useful information are noteworthy and hence have been mentioned

Modeling and Optimization of Micro-EDM Operation for Fabrication of Micro Holes

Based on the experimental results, an analysis was made to identify the performance of various electrodes during fabrication of micro holes considering Inconel 718 as well as titanium as workpiece materials. It was found that that platinum followed by graphite and copper as electrode material exhibited higher MRR for both the workpiece materials but on the other hand platinum showed higher values of OC, RCL and TA respectively when compared to graphite and copper. The variation of temperature distribution in radial and depth direction with different process parameters has been determined for Inconel 718 and Titanium 5. Theoretical cavity volume was calculated for different process parameter settings for both workpiece materials and it was found that Titanium 5 exhibited higher cavity volume then Inconel 718. This research work offers new insights into the performance of micro-µ-EDM of Inconel 718 and Titanium5 using different electrodes. The optimum process parameters have been identified to determine multi-objective machinability criteria such as MRR, angle of taper of micro-hole, the thickness of recast-layer and overcut for fabrication of micro-holes

An analysis of Grade 9 learners' performance in the 2004 Natural Science common tasks for assessment with special reference to science process skills, learning outcomes and assessment standards

Includes bibliographical references (p. 227-239).In 2004 an educational evaluation strategy consisting of Common Tasks for Assessment (CTAs) was introduced nationally into South African high schools as an external examination, marked internally by individual teachers. It took the form of a systemic assessment for Grade 9 learners with the main intentions of promoting a common standard and serving as a validating tool for school-based assessment. This analytical descriptive investigation in 12 schools (in the Western Cape is a contribution to the research fields of academic performance testing, achievement and response. CTAs use the framework of the curriculum, broadly defined as the organising principle in how educational opportunities are provided to learners. Hence, the basis of the CT A model has three aspects: the intended curriculum, the implemented curriculum, and the attained and experienced curriculum. The CTA testing took place in 2004 with many schools participating. The CTA assessment in the area of Natural Science was framed by two organising dimensions: a content domain and a cognitive domain. The content domains that framed the science curriculum were presented as themes: life and living; energy and change and matter and materials. The cognitive domains were: factual knowledge, conceptual knowledge, and reasoning and analysis

Effects of strain rate, friction and temperature distribution in high speed axisymmetric upsetting

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The reliability of simple progressive dies

The stamping process, of which the punching process is a major division, is one of the most important metal parts production methods in industry. Punching dies are the heart of the punching process. Die performance, as measured by the number of strokes between sharpenings and/or repairs, determines the important per part costs of die depletion and maintenance. Existing quantitative studies are principally on tool wear and punchability

Big Explosions and Strong Gravity

This guide has been developed to assist people who would like to run the Big Explosions and Strong Gravity event with their local Girl Scout Council. The event is a one-day event in which a group of Girl Scouts spends their time doing a series of hands-on activities on spectroscopy, cosmic abundances, supernovae, and black holes. Professional scientists, engineers, and graduate students assist with these activities, giving the scouts a chance to interact with professionals in science and technology fields. Educational levels: Informal education

A Review of Methodological Approaches for the Design and Optimization of Wind Farms

This article presents a review of the state of the art of the Wind Farm Design and Optimization (WFDO) problem. The WFDO problem refers to a set of advanced planning actions needed to extremize the performance of wind farms, which may be composed of a few individual Wind Turbines (WTs) up to thousands of WTs. The WFDO problem has been investigated in different scenarios, with substantial differences in main objectives, modelling assumptions, constraints, and numerical solution methods. The aim of this paper is: (1) to present an exhaustive survey of the literature covering the full span of the subject, an analysis of the state-of-the-art models describing the performance of wind farms as well as its extensions, and the numerical approaches used to solve the problem; (2) to provide an overview of the available knowledge and recent progress in the application of such strategies to real onshore and offshore wind farms; and (3) to propose a comprehensive agenda for future research