Direct numerical simulation of compressible turbulence accelerated by graphics processing unit. Part 1: An open-source high accuracy accelerated computational fluid dynamic software

This paper introduces open-source computational fluid dynamics software named open computational fluid dynamic code for scientific computation with graphics processing unit (GPU) system (OpenCFD-SCU), developed by the authors for direct numerical simulation (DNS) of compressible wall-bounded turbulence. This software is based on the finite difference method and is accelerated by the use of a GPU, which provides an acceleration by a factor of more than 200 compared with central processing unit (CPU) software based on the same algorithm and number of message passing interface (MPI) processes, and the running speed of OpenCFD-SCU with just 512 GPUs exceed that of CPU software with 130\,000 CPUs. GPU-Stream technology is used to implement overlap of computing and communication, achieving 98.7\% parallel weak scalability with 24\,576 GPUs. The software includes a variety of high-precision finite difference schemes, and supports a hybrid finite difference scheme, enabling it to provide both robustness and high precision when simulating complex supersonic and hypersonic flows. When used with the wide range of supercomputers currently available, the software should able to improve the performance of large-scale simulations by up to two orders on the computational scale. Then, OpenCFD-SCU is applied to a validation and verification case of a Mach 2.9 compression ramp with mesh numbers up to 31.2 billion. More challenging cases using hybrid finite schemes are shown in Part 2(Dang, Li et al. 2022). The code is available and supported at \url{http://developer.hpccube.com/codes/danggl/opencfd-scu.git}.Comment: 23 pages, 25 figure

A Stealthy and Robust Fingerprinting Scheme for Generative Models

This paper presents a novel fingerprinting methodology for the Intellectual Property protection of generative models. Prior solutions for discriminative models usually adopt adversarial examples as the fingerprints, which give anomalous inference behaviors and prediction results. Hence, these methods are not stealthy and can be easily recognized by the adversary. Our approach leverages the invisible backdoor technique to overcome the above limitation. Specifically, we design verification samples, whose model outputs look normal but can trigger a backdoor classifier to make abnormal predictions. We propose a new backdoor embedding approach with Unique-Triplet Loss and fine-grained categorization to enhance the effectiveness of our fingerprints. Extensive evaluations show that this solution can outperform other strategies with higher robustness, uniqueness and stealthiness for various GAN models

Soil contamination in China:Current priorities, defining background levels and standards for heavy metals

The Chinese Government is working to establish an effective framework in managing soil contamination. Heavy metal contamination is key to the discussion about soil quality, health and remediation in China. Soil heavy metal contamination in China is briefly reviewed and the concepts of background values and standards discussed. The importance of contaminated land and its management for China food security and urbanization are discussed. Priorities for China's next steps in developing an effective research and management regime are presented. We propose that critically important to the science-based risk assessment of contaminants in soils is the incorporation of speciation and bioavailability into the measurement and evaluation criteria. Consideration of soil biology/ecological endpoints will be necessary to protect ecosystem health. National and regional/local scenarios of land use type/usage will address residential/urban re-use of industrial land as well as varying agricultural scenarios

Redefining coherence : interaction and experience in new music, 1985-1995

This thesis presents an analytical exploration of a number of works from 1985 to 1995, many of which have not previously received detailed attention. Although they stem from quite varied stylistic and aesthetic backgrounds, all these pieces are situated in a particular position within the tradition of Western art music: they show an approach which is neither ‘avant-garde’ in its commitment to continual formal and technical novelty, nor clearly associated with any other existing compositional school. Instead, they engage with a diverse range of models, both musical and external; intra-musical connections range from the legacy of the broader Classical and Romantic common-practice tradition to the varied timbral and formal developments of the twentieth-century avant-garde, whilst extra-musical connections seem almost endless, encompassing fields from art to astronomy, literature to horticulture. Alongside this stylistic and referential plurality, they display an often seemingly intuitive approach towards structure and system, with their most striking musical effects often arising out of layered, non-hierarchical interactions between different materials and processes. As such, they present clear challenges to traditional conceptions of analysis, which are often based around the systematic generation of clear (albeit often very complex) organisational structures. It is argued that this music, in spite of these challenges, displays a striking level of expressive and aural coherence; conventional ways of understanding this term – whether they be based around unity of material or form or process – need to be redefined to take this into account. Chosen works are approached by way of a ‘patchwork’ of different perspectives and techniques: the core of the thesis is a series of four case studies which connect narratives of listener experience with analytical and contextual detail, making particular use of the clarifying potential of metaphor. These close readings are interleaved with chapters which consider the wider challenges and implications for the study of this repertoire, drawing upon a number of strands in contemporary musicological and philosophical thought.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A survey and classification of storage deduplication systems

The automatic elimination of duplicate data in a storage system commonly known as deduplication is increasingly accepted as an effective technique to reduce storage costs. Thus, it has been applied to different storage types, including archives and backups, primary storage, within solid state disks, and even to random access memory. Although the general approach to deduplication is shared by all storage types, each poses specific challenges and leads to different trade-offs and solutions. This diversity is often misunderstood, thus underestimating the relevance of new research and development. The first contribution of this paper is a classification of deduplication systems according to six criteria that correspond to key design decisions: granularity, locality, timing, indexing, technique, and scope. This classification identifies and describes the different approaches used for each of them. As a second contribution, we describe which combinations of these design decisions have been proposed and found more useful for challenges in each storage type. Finally, outstanding research challenges and unexplored design points are identified and discussed.This work is funded by the European Regional Development Fund (EDRF) through the COMPETE Programme (operational programme for competitiveness) and by National Funds through the Fundacao para a Ciencia e a Tecnologia (FCT; Portuguese Foundation for Science and Technology) within project RED FCOMP-01-0124-FEDER-010156 and the FCT by PhD scholarship SFRH-BD-71372-2010

Direct numerical simulation of shock wave/turbulent boundary layer interaction in a swept compression ramp at Mach 6

Swept compression ramps widely exist in supersonic/hypersonic vehicles and have become a typical standard model for studying three-dimensional (3D) shock wave/turbulent boundary layer interactions (STBLIs). In this paper, we conduct a direct numerical simulation of swept compression ramp STBLI with a 34 degrees compression angle and a 45 degrees sweep angle at Mach 6 using a heterogeneous parallel finite difference solver. Benefitting from the powerful computing performance of the graphics processing unit, the computational grid number exceeds 5 x 10(6) with the spatiotemporal evolution data of hypersonic 3D STBLI obtained. The results show that the flow of the hypersonic swept compression ramp follows the quasi-conical symmetry. A supersonic crossflow with helical motion appears in the interaction region, and its velocity increases along the spanwise direction. Fluids from the high-energy-density region pass through the bow shock at the head of the main shock and crash into the wall downstream of the reattachment, resulting in the peaks in skin friction and heat flux. The peak friction and heating increase along the spanwise direction because of the spanwise variation in the shock wave inclination. In the interaction region, the unsteadiness is dominated by the mid-frequency motion, whereas the low-frequency large-scale motion is nearly absent. Two reasons for the lack of low-frequency unsteadiness are given: (1) The separation shock is significantly weaker than the reattachment shock and main shock; and (2) because of the supersonic crossflow, the perturbations propagating at the sound speed are not self-sustaining but flow along the r-direction and toward the spanwise boundary. Published under an exclusive license by AIP Publishing

Design, Analysis and Experiments of Hexapod Robot with Six-Link Legs for High Dynamic Locomotion

An important feature of a legged robot is its dynamic motion performance. Traditional methods often improve the dynamic motion performance by reducing the moment of inertia of robot legs or by adopting quasi-direct drive actuators. This paper proposes a method to enhance the dynamic performance of a legged robot by transmission mechanism. Specifically, we present a unique six-link leg mechanism that can implement a large output motion using a small drive motion. This unique feature can enhance the robots’ dynamic motion capability. Experiments with a hexapod robot verified the effectiveness of the mechanism. The experimental results showed that, when the steering gear of the robot rotates 1°, the toe can lift 7 mm (5% of body height), and the maximum running speed of the robot can reach 390 mm/s (130% of the moveable body length per second)

Big Data Analytics in the Fight against Major Public Health Incidents (Including COVID-19):A Conceptual Framework

Major public health incidents such as COVID-19 typically have characteristics of being sudden, uncertain, and hazardous. If a government can effectively accumulate big data from various sources and use appropriate analytical methods, it may quickly respond to achieve optimal public health decisions, thereby ameliorating negative impacts from a public health incident and more quickly restoring normality. Although there are many reports and studies examining how to use big data for epidemic prevention, there is still a lack of an effective review and framework of the application of big data in the fight against major public health incidents such as COVID-19, which would be a helpful reference for governments. This paper provides clear information on the characteristics of COVID-19, as well as key big data resources, big data for the visualization of pandemic prevention and control, close contact screening, online public opinion monitoring, virus host analysis, and pandemic forecast evaluation. A framework is provided as a multidimensional reference for the effective use of big data analytics technology to prevent and control epidemics (or pandemics). The challenges and suggestions with respect to applying big data for fighting COVID-19 are also discussed

Direct numerical simulation of compressible turbulence accelerated by graphics processing unit: An open-access database of high-resolution direct numerical simulation

In the author's previous work, we introduced an open-source accelerated computational fluid dynamics code for scientific computations using a graphics processing unit system (OpenCFD-SCU). This code offers significantly improved computation speed and can be applied to challenging direct numerical simulation (DNS) problems. This paper presents several high-resolution cases using OpenCFD-SCU: (1) a 24? compression ramp at Mach 2.9, where the length of the ramp is 200 mm and the mesh number is 7.68 x 109; (2) a 34? compression ramp at Mach 6 with a mesh number of 9.3 x 109; (3) a cold-wall flat plate at Mach 10 with a friction Reynolds number of 1550 and mesh number of 4.5 x 109; (4) a blunt cone with a 1 mm head radius and 0? attack angle at Mach 10, where the mesh number is 24 x 109; and (5) a lifting-body model at Mach 6 with a mesh number of 11.1 x 109. Compared with DNS studies of compressible wall-bound turbulent flow under similar conditions, these cases have larger computational domains, finer resolutions, or higher Reynolds numbers, demonstrating the simulation capability of OpenCFD-SCU and broadening the scope of DNS applications. We have conducted preliminary analyses of these cases and have established an open-access database to store these data. The source code of OpenCFD-SCU can be accessed at http://developer.hpccube.com/codes/danggl/opencfd-scu.git; this website also contains detailed database descriptions and data acquisition methods. (C) 2022 Author(s)

Soil environmental management systems for contaminated sites in China and the EU. Common challenges and perspectives for lesson drawing

This paper aims at appraising the current progress of China's contaminated sites environmental management system, identifying its bottlenecks and individuating areas for lesson drawing based on the relevant EU experience. The paper provides an overview of policies, laws, standards, administrative functions, and management processes relevant to China's contaminated sites environmental management. Based on its current development status, the following shortcomings can be individuated in the Chinese case: (a) inadequate monitoring system; (b) incomplete legislation; (c) overlapping of competencies in sites administration; (d) lack of a dedicated funding scheme. Similar challenges have been characterising also the development of the management system for contaminated sites in EU Member States. Based on the experience matured in the EU in tackling such challenges, the final section of the paper puts forward recommendations targeted on the Chinese case. Proposed recommendations are discussed against the broader background of China's institutional and policy environment