Profit Maximization Auction and Data Management in Big Data Markets

A big data service is any data-originated resource that is offered over the Internet. The performance of a big data service depends on the data bought from the data collectors. However, the problem of optimal pricing and data allocation in big data services is not well-studied. In this paper, we propose an auction-based big data market model. We first define the data cost and utility based on the impact of data size on the performance of big data analytics, e.g., machine learning algorithms. The big data services are considered as digital goods and uniquely characterized with "unlimited supply" compared to conventional goods which are limited. We therefore propose a Bayesian profit maximization auction which is truthful, rational, and computationally efficient. The optimal service price and data size are obtained by solving the profit maximization auction. Finally, experimental results on a real-world taxi trip dataset show that our big data market model and auction mechanism effectively solve the profit maximization problem of the service provider.Comment: 6 pages, 9 figures. This paper was accepted by IEEE WCNC conference in Dec. 201

Prediction of thermal stresses and shape deviation of selective laser melted overhanging region with a coupled CFD-FEM model

Selective laser melting (SLM), also known as powder bed fusion (PBF), is a flexible approach to fabricate complex-shaped metal parts layer-by-layer, especially for parts with complex interior shapes that are difficult to be machined conventionally. One of its typical applications is to fabricate molds consisting of conformal cooling system in which cooling channels may have to be printed horizontally without any supports [1]. Moreover, the internal channel surface cannot be further finished after SLM due to structural limitations. Thermal stress-induced deformation and surface roughness of the overhanging region are two major contributors to shape deviation and are thus concerns that must be addressed. The simulation work presented in this abstract investigates the mechanisms of deformation and surface roughness on overhanging region induced by thermo-mechanical behavior of SLM process under different overhanging angles, laser power, and scan velocity. A 3D coupled CFD-FEM model is developed by considering the heat conduction, melting and solidification with latent heat, surface tension, as well as Marangoni convection. A quasi-randomly distributed powder bed is employed. The simulation results are validated with SLM printing experiments. The overhanging region is nonrigid and essentially a cantilever due to the unmelted powder below. The simulation result shows that the stresses in the SLMed overhanging region are much lower than the stresses in the solid region. The stresses in the overhanging region are released, however, leading to unwanted upward deflection. The surface roughness on the overhanging region is largely determined by the shape and size of the molten pool. It increases with increasing overhanging angle and energy input per volume (i.e. increase of laser power or decrease of scan velocity). This simulation work can thus be directly used to compensate for the shape deviation in the design stage, namely design-for-AM guidelines for the additive manufacturing of internal channels. It will also be helpful for process parameter optimization in the overhanging region to minimize surface roughness.<br/

Prediction of thermal stresses and shape deviation of selective laser melted overhanging region with a coupled CFD-FEM model

Selective laser melting (SLM), also known as powder bed fusion (PBF), is a flexible approach to fabricate complex-shaped metal parts layer-by-layer, especially for parts with complex interior shapes that are difficult to be machined conventionally. One of its typical applications is to fabricate molds consisting of conformal cooling system in which cooling channels may have to be printed horizontally without any supports [1]. Moreover, the internal channel surface cannot be further finished after SLM due to structural limitations. Thermal stress-induced deformation and surface roughness of the overhanging region are two major contributors to shape deviation and are thus concerns that must be addressed. The simulation work presented in this abstract investigates the mechanisms of deformation and surface roughness on overhanging region induced by thermo-mechanical behavior of SLM process under different overhanging angles, laser power, and scan velocity. A 3D coupled CFD-FEM model is developed by considering the heat conduction, melting and solidification with latent heat, surface tension, as well as Marangoni convection. A quasi-randomly distributed powder bed is employed. The simulation results are validated with SLM printing experiments. The overhanging region is nonrigid and essentially a cantilever due to the unmelted powder below. The simulation result shows that the stresses in the SLMed overhanging region are much lower than the stresses in the solid region. The stresses in the overhanging region are released, however, leading to unwanted upward deflection. The surface roughness on the overhanging region is largely determined by the shape and size of the molten pool. It increases with increasing overhanging angle and energy input per volume (i.e. increase of laser power or decrease of scan velocity). This simulation work can thus be directly used to compensate for the shape deviation in the design stage, namely design-for-AM guidelines for the additive manufacturing of internal channels. It will also be helpful for process parameter optimization in the overhanging region to minimize surface roughness.<br/

Prediction of thermal stresses and shape deviation of selective laser melted overhanging region with a coupled CFD-FEM model

Selective laser melting (SLM), also known as powder bed fusion (PBF), is a flexible approach to fabricate complex-shaped metal parts layer-by-layer, especially for parts with complex interior shapes that are difficult to be machined conventionally. One of its typical applications is to fabricate molds consisting of conformal cooling system in which cooling channels may have to be printed horizontally without any supports [1]. Moreover, the internal channel surface cannot be further finished after SLM due to structural limitations. Thermal stress-induced deformation and surface roughness of the overhanging region are two major contributors to shape deviation and are thus concerns that must be addressed. The simulation work presented in this abstract investigates the mechanisms of deformation and surface roughness on overhanging region induced by thermo-mechanical behavior of SLM process under different overhanging angles, laser power, and scan velocity. A 3D coupled CFD-FEM model is developed by considering the heat conduction, melting and solidification with latent heat, surface tension, as well as Marangoni convection. A quasi-randomly distributed powder bed is employed. The simulation results are validated with SLM printing experiments. The overhanging region is nonrigid and essentially a cantilever due to the unmelted powder below. The simulation result shows that the stresses in the SLMed overhanging region are much lower than the stresses in the solid region. The stresses in the overhanging region are released, however, leading to unwanted upward deflection. The surface roughness on the overhanging region is largely determined by the shape and size of the molten pool. It increases with increasing overhanging angle and energy input per volume (i.e. increase of laser power or decrease of scan velocity). This simulation work can thus be directly used to compensate for the shape deviation in the design stage, namely design-for-AM guidelines for the additive manufacturing of internal channels. It will also be helpful for process parameter optimization in the overhanging region to minimize surface roughness.<br/

Prediction of thermal stresses and shape deviation of selective laser melted overhanging region with a coupled CFD-FEM model

Selective laser melting (SLM), also known as powder bed fusion (PBF), is a flexible approach to fabricate complex-shaped metal parts layer-by-layer, especially for parts with complex interior shapes that are difficult to be machined conventionally. One of its typical applications is to fabricate molds consisting of conformal cooling system in which cooling channels may have to be printed horizontally without any supports [1]. Moreover, the internal channel surface cannot be further finished after SLM due to structural limitations. Thermal stress-induced deformation and surface roughness of the overhanging region are two major contributors to shape deviation and are thus concerns that must be addressed. The simulation work presented in this abstract investigates the mechanisms of deformation and surface roughness on overhanging region induced by thermo-mechanical behavior of SLM process under different overhanging angles, laser power, and scan velocity. A 3D coupled CFD-FEM model is developed by considering the heat conduction, melting and solidification with latent heat, surface tension, as well as Marangoni convection. A quasi-randomly distributed powder bed is employed. The simulation results are validated with SLM printing experiments. The overhanging region is nonrigid and essentially a cantilever due to the unmelted powder below. The simulation result shows that the stresses in the SLMed overhanging region are much lower than the stresses in the solid region. The stresses in the overhanging region are released, however, leading to unwanted upward deflection. The surface roughness on the overhanging region is largely determined by the shape and size of the molten pool. It increases with increasing overhanging angle and energy input per volume (i.e. increase of laser power or decrease of scan velocity). This simulation work can thus be directly used to compensate for the shape deviation in the design stage, namely design-for-AM guidelines for the additive manufacturing of internal channels. It will also be helpful for process parameter optimization in the overhanging region to minimize surface roughness.<br/

Non-communicable diseases sustained high call: China's health care model should be transformed as soon as possible

Background: There is sufficient evidence that the prevalence of non-communicable diseases (NCDs) in China is increasing rapidly. Results from the Fourth China National Health Services Survey (2008) show that compared to 2003, the prevalence of chronic diseases in China increased by 5%, while results from the Fifth National Health Services Survey (2013) showed an increase of 9% since 2008. As the world's most populous country and in the face of the rapid rise of non-communicable diseases, China lacks effective measures to achieve significant results on aspects of tobacco use, unhealthy diet, lack of exercise, harmful alcohol use and other risk factors. Of more concern is that the Chinese health care model is still stuck in the "medical services" stage. The "therapy" of health care models not only cause China to experience high health costs - there is also a steady increase in adverse health outcomes, with a failure to timely and effectively respond to the challenges of NCDs. Purpose: This article aims to analyze health care inputs and outputs since Chinese health care reform, and to provide a useful reference to improve Chinese future health care policies

Design and fabrication of conformal cooling channels in molds:Review and progress updates

Conformal cooling (CC) channels are a series of cooling channels that are equidistant from the mold cavity surfaces. CC systems show great promise to substitute conventional straight-drilled cooling systems as the former can provide more uniform and efficient cooling effects and thus improve the production quality and efficiency significantly. Although the design and manufacturing of CC systems are getting increasing attention, a comprehensive and systematic classification, comparison, and evaluation are still missing. The design, manufacturing, and applications of CC channels are reviewed and evaluated systematically and comprehensively in this review paper. To achieve a uniform and rapid cooling, some key design parameters of CC channels related to shape, size, and location of the channel have to be calculated and chosen carefully taking into account the cooling performance, mechanical strength, and coolant pressure drop. CC layouts are classified into eight types. The basic type, more complex types, and hybrid straight-drilled-CC molds are suitable for simply-shaped parts, complex-shaped parts, and locally complex parts, respectively. By using CC channels, the cycle time can be reduced up to 70%, and the shape deviations can be improved significantly. Epoxy casting and L-PBF show the best applicability to Al-epoxy molds and metal molds, respectively, because of the high forming flexibility and fidelity. Meanwhile, LPD has an exclusive advantage to fabricate multi-materials molds although it cannot print overhang regions directly. Hybrid L-PBF/CNC milling pointed out the future direction for the fabrication of high dimensional-accuracy CC molds, although there is still a long way to reduce the cost and raise efficiency. CC molds are expected to substitute straight-drilled cooling molds in the future, as it can significantly improve part quality, raise production rate and reduce production cost. In addition to this, the use of CC channels can be expanded to some advanced products that require high-performance self-cooling, such as gas turbine engines, photoinjectors and gears, improving working conditions and extending lifetime

New reaching law control for permanent magnet synchronous motor with extended disturbance observer

In order to improve the anti-disturbance performance of permanent magnet synchronous motor (PMSM) servo system, a sliding-mode control strategy using a new reaching law (NRL) is proposed. The NRL incorporates power term and switching gain term of the system state variables into the conventional exponential reaching law (CERL), which can effectively suppress the sliding-mode chattering and increase the convergence rate of system state reaching sliding-mode surface. Based on this new reaching law, a sliding-mode speed controller (SMSC) of PMSM is designed. At the same time, to solve the chattering problem caused by the large sliding-mode switching gain, an anti-disturbance sliding-mode speed controller method with an extended sliding-mode disturbance observer (ESMDO), called SMSC+ESMDO method, is developed. The sliding-mode disturbance observer is designed to accurately estimate the motor speed and external load disturbances, and the disturbance estimator is used as a feed-forward to compensate the sliding-mode speed controller (SMSC) to improve the system robustness and reduce the system chattering. Simulation and experimental results show that the proposed compound sliding-mode control strategy can effectively improve the dynamic performance and robustness of the system compared with the PI controller