Numerical investigations on dynamic stall of low Reynolds number flow around oscillating airfoils

This paper presents a 2D computational investigation on the dynamic stall phenomenon associated with unsteady flow around the NACA0012 airfoil at low Reynolds number (Re_c ≈ 10⁵). Two sets of oscillating patterns with different frequencies, mean oscillating angles and amplitudes are numerically simulated using Computational Fluid Dynamics (CFD), and the results obtained are validated against the corresponding published experimental data. It is concluded that the CFD prediction captures well the vortex-shedding predominated flow structure which is experimentally obtained and the results quantitatively agree well with the experimental data, except when the blade is at a very high angle of attack.     

Partitioning large networks without breaking communities

The identification of cohesive communities is a key process in social network analysis. However, the algorithms that are effective for finding communities do not scale well to very large problems, as their time complexity is worse than linear in the number of edges in the graph. This is an important issue for those interested in applying social network analysis techniques to very large networks, such as networks of mobile phone subscribers. In this respect, the contributions of this paper are twofold. First, we demonstrate these scaling issues using a prominent community-finding algorithm as a case study. Then, we show that a two-stage process, whereby the network is first decomposed into manageable subnetworks using a multilevel graph partitioning procedure, is effective in finding communities in networks with more than 10⁶ nodes.     

Micropatterning of sulfonated polyaniline using a soft lithography based lift-off process

A combination of soft lithography and lift-off processing is presented for the fabrication of sulfonated polyaniline (SPAN) microstructures. A soft lithography based micromolding process was used to pattern sacrificial layers using a thermoplastic polymer. SPAN was then polymerized in situ to coat the patterned substrate. The sacrificial layer was removed by lift-off in an organic solvent, leaving the patterned SPAN on the substrate. This process was performed on several rigid and flexible substrates including glass, silicon, and polyimide. The film thickness and roughness were measured as a function of reaction time using atomic force microscopy. Patterns were also imaged using scanning electron microscopy. This process provides a cost effective and versatile method of patterning SPAN and has potential applications in a number of conducting polymer devices.     

Deterministic planning in the fifth international planning competition: PDDL3 and experimental evaluation of the planners

The international planning competition (IPC) is an important driver for planning research. The general goals of the IPC include pushing the state of the art in planning technology by posing new scientific challenges, encouraging direct comparison of planning systems and techniques, developing and improving a common planning domain definition language, and designing new planning domains and problems for the research community. This paper focuses on the deterministic part of the fifth international planning competition (IPC5), presenting the language and benchmark domains that we developed for the competition, as well as a detailed experimental evaluation of the deterministic planners that entered IPC5, which helps to understand the state of the art in the field.We present an extension of pddl, called pddl3, allowing the user to express strong and soft constraints about the structure of the desired plans, as well as strong and soft problem goals. We discuss the expressive power of the new language focusing on the restricted version that was used in IPC5, for which we give some basic results about its compilability into pddl2. Moreover, we study the relative performance of the IPC5 planners in terms of solved problems, CPU time, and plan quality; we analyse their behaviour with respect to the winners of the previous competition; and we evaluate them in terms of their capability of dealing with soft goals and constraints, and of finding good quality plans in general. Overall, the results indicate significant progress in the field, but they also reveal that some important issues remain open and require further research, such as dealing with strong constraints and computing high quality plans in metric-time domains and domains involving soft goals or constraints.     

Benchmarking stereo-derived DSMs to lidar by land cover and slope for resource development in northern Ontario,Canada

Topographic and elevation data are essential in the development of supporting infrastructure around mining sites. The de facto standard for acquiring elevation data is through light detection and ranging (lidar). The high labour and monetary cost of acquiring lidar has fostered more cost-effective approaches for creating elevation models that use stereo photogrammetry. To assess the accuracy of stereo-photogrammetry-derived elevation models and their potential application, we benchmark satellite (Worldview-2) and aircraft (South Central Ontario Orthoimagery Project; SCOOP) stereo-derived digital surface models (DSMs) against a lidar-derived DSM. Our results show that both stereo-derived DSMs have strong monotonic correlations with lidar across a range of land-cover types and slopes. The overall vertical accuracy of Worldview-2 and SCOOP DSMs are similar and do not meet the United States National Digital Elevation Program (NDEP) standards. However, accuracy assessment across land-cover types and slope categories show that specific land cover types (i.e. grass, row crops/pasture, sparse vegetation and marsh) on gently sloping terrain compare well to lidar data and meet NDEP accuracy standards. We situate the presented research in the context of northern resource development and discuss opportunities to improve the vertical accuracy of stereo-derived DSMs, for example, through unmanned aerial systems.     

Reduced Aggregate Scattering Operators for Path Tracing

Aggregate scattering operators (ASOs) describe the overall scattering behavior of an asset (i.e., an object or volume, or collection thereof) accounting for all orders of its internal scattering. We propose a practical way to precompute and compactly store ASOs and demonstrate their ability to accelerate path tracing. Our approach is modular avoiding costly and inflexible scene‐dependent precomputation. This is achieved by decoupling light transport within and outside of each asset, and precomputing on a per‐asset level. We store the internal transport in a reduced‐dimensional subspace tailored to the structure of the asset geometry, its scattering behavior, and typical illumination conditions, allowing the ASOs to maintain good accuracy with modest memory requirements. The precomputed ASO can be reused across all instances of the asset and across multiple scenes. We augment ASOs with functionality enabling multi‐bounce importance sampling, fast short‐circuiting of complex light paths, and compact caching, while retaining rapid progressive preview rendering. We demonstrate the benefits of our ASOs by efficiently path tracing scenes containing many instances of objects with complex inter‐reflections or multiple scattering.     

Moblin.org开源项目

市场上出现了一种新的设备,它能够访问Internet上丰富的内容,同时没有与PC相关的复杂性。这些设备以各种形式出现,从移动互联网设备（Mobile Internet Devices,MID）、便携式媒体播放器（PMP）到个人导航设备（PND）、数码机顶盒（STB）到笔记本电脑。Moblin.org项目由Intel于2007年7月正式启动,它的目的是推动此类设备所需的最新技术的发展。     

A Model-Based Method for an Online Diagnostic Knowledge-Based System

Fault diagnosis is very important for modern production technology and has received increasing theoretical and practical attention during the last few years. This paper presents a model-based diagnostic method for industrial systems. An online, real-time, deep knowledge based fault detection system has been developed by combining different development environments and tools. The system diagnoses, predicts and compensates faults by coupling symbolic and numerical data in a new environment suitable for the interaction of different sources of knowledge and has been successfully implemented and tested on a real hydraulic system.     

Internal and contextual factors, knowledge processes and performance: From the Chinese provider’s perspective

This paper explores the influences of two internal factors, i.e. supplier team’s IT-based skills and communication with client’s team, and two contextual factors, i.e. supplier team’s understanding of client’s culture and collaboration with client’s team, on knowledge processes and performance in global sourcing of IT services from the Chinese provider’s perspective. Knowledge processes are characterized by knowledge sharing, knowledge-based coordination and expertise management, and performance is measured by product success and personal satisfaction. Data have been collected in 13 companies in Xi’an Software Park, with 26 in-depth, semi-structured interviews held with top and middle managers, and 200 structured questionnaires distributed to knowledge workers who are involved in global sourcing projects. The results indicate that supplier team’s IT-based skills, communication with client’s team, cultural understanding of client’s culture and collaboration with client’s team are positively associated with knowledge process and performance. Also, knowledge sharing, knowledge-based coordination and expertise management are found to be crucial for those influential factors to function positively and contribute to the performance. The findings of this study suggest that the effects of key factors on knowledge processes and performance in global sourcing of IT services appear to transcend the social and cultural differences; however, contextual factors seem to have more significant influences on knowledge processes and performance in global sourcing of IT services.     

Sputter deposition of bcc tantalum films with TaN underlayers for protection of steel

Deposition of tantalum films for protective coatings on steel has been investigated. The desired tough and ductile bcc phase of tantalum, rather than the normally deposited hard and brittle tetragonal phase, has been grown by DC magnetron sputtering on unheated substrates first covered with thin layers of tantalum nitride. The nitride was formed by reactive sputtering with nitrogen gas, with the same DC magnetron source and target as used for deposition of tantalum. The crystal structure and composition of the nitride promoting the growth of bcc Ta, previously undefined, has been identified as the metastable fcc (NaCl like) TaN. Alignment of the (111) crystallographic planes of fcc TaN with (110) planes of bcc Ta is discussed as a possible mechanism for this effect. The minimum thickness of TaN underlayer on steel, required to promote the growth of bcc Ta, has been established and found to be dependent on the substrate surface preparation. Scratch tests with a diamond tip showed that the nitride underlayer does not compromise the film adhesion. Stable and well-adhering coatings of bcc Ta with thickness ranging from tens of nanometers to tens of micrometers on steel with a thin TaN underlayer were obtained. The process of deposition of bcc Ta films, including the formation of TaN underlayers is described in detail.