A GPU-accelerated package for simulation of flow in nanoporous source rocks with many-body dissipative particle dynamics

Mesoscopic simulations of hydrocarbon flow in source shales are challenging, in part due to the heterogeneous shale pores with sizes ranging from a few nanometers to a few micrometers. Additionally, the sub-continuum fluid-fluid and fluid-solid interactions in nano- to micro-scale shale pores, which are physically and chemically sophisticated, must be captured. To address those challenges, we present a GPU-accelerated package for simulation of flow in nano- to micro-pore networks with a many-body dissipative particle dynamics (mDPD) mesoscale model. Based on a fully distributed parallel paradigm, the code offloads all intensive workloads on GPUs. Other advancements, such as smart particle packing and no-slip boundary condition in complex pore geometries, are also implemented for the construction and the simulation of the realistic shale pores from 3D nanometer-resolution stack images. Our code is validated for accuracy and compared against the CPU counterpart for speedup. In our benchmark tests, the code delivers nearly perfect strong scaling and weak scaling (with up to 512 million particles) on up to 512 K20X GPUs on Oak Ridge National Laboratory's (ORNL) Titan supercomputer. Moreover, a single-GPU benchmark on ORNL's SummitDev and IBM's AC922 suggests that the host-to-device NVLink can boost performance over PCIe by a remarkable 40\%. Lastly, we demonstrate, through a flow simulation in realistic shale pores, that the CPU counterpart requires 840 Power9 cores to rival the performance delivered by our package with four V100 GPUs on ORNL's Summit architecture. This simulation package enables quick-turnaround and high-throughput mesoscopic numerical simulations for investigating complex flow phenomena in nano- to micro-porous rocks with realistic pore geometries

Symmetric and asymmetric action integration during cooperative object manipulation in virtual environments

Cooperation between multiple users in a virtual environment (VE) can take place at one of three levels. These are defined as where users can perceive each other (Level 1), individually change the scene (Level 2), or simultaneously act on and manipulate the same object (Level 3). Despite representing the highest level of cooperation, multi-user object manipulation has rarely been studied. This paper describes a behavioral experiment in which the piano movers' problem (maneuvering a large object through a restricted space) was used to investigate object manipulation by pairs of participants in a VE. Participants' interactions with the object were integrated together either symmetrically or asymmetrically. The former only allowed the common component of participants' actions to take place, but the latter used the mean. Symmetric action integration was superior for sections of the task when both participants had to perform similar actions, but if participants had to move in different ways (e.g., one maneuvering themselves through a narrow opening while the other traveled down a wide corridor) then asymmetric integration was superior. With both forms of integration, the extent to which participants coordinated their actions was poor and this led to a substantial cooperation overhead (the reduction in performance caused by having to cooperate with another person)

Suppressing Protest: Human Rights Violations in the U.S. Response to Occupy Wall Street

In September 2011, waves of protests against mounting socioeconomic injustice broke out across the United States, capturing the attention of the country. The Occupy Wall Street movement, inspired by similar protests around the globe, used the occupation of public space and mass demonstrations to call attention to a wide array of shared concerns. The movement also used public assemblies to debate concerns and promote direct democratic participation. Within weeks of their emergence, the protests dramatically expanded and deepened U.S. political discourse around the widening gap between rich and poor, bank bailouts and impunity for financial crimes, and the role of money in politics. The response of U.S. authorities to the protests also received significant attention. Images of police using pepper spray on seated students, the arrests of thousands of peaceful protesters across the country, midnight raids on encampments, baton-swinging officers, marches accompanied by phalanxes of riot police, and officers obstructing and arresting journalists were beamed around the world. This is the first in a series of reports examining the responses of U.S. authorities to the Occupy protests. Through an eight-month-long study of the response in New York City, together with comparative data collected from cities across the United States, this report highlights major policy concerns and serious violations of the rights of protesters. Further detailed studies will be published in the coming months on the response of authorities in Boston, Charlotte, Oakland, and San Francisco. Government responses to Occupy Wall Street in the United States have varied significantly, both within and across cities. Indeed, there have been examples of good practice, including through welcoming assemblies, using modern democratic policing styles that promote negotiation to facilitate protests, and enforcing strict controls on any use of police force. But across the United States, abusive and unlawful protest regulation and policing practices have been and continue to be alarmingly evident. This report follows a review of thousands of news reports and hundreds of hours of video, extensive firsthand observation, and detailed witness interviews