Crowd-ML: A Privacy-Preserving Learning Framework for a Crowd of Smart Devices

Smart devices with built-in sensors, computational capabilities, and network connectivity have become increasingly pervasive. The crowds of smart devices offer opportunities to collectively sense and perform computing tasks in an unprecedented scale. This paper presents Crowd-ML, a privacy-preserving machine learning framework for a crowd of smart devices, which can solve a wide range of learning problems for crowdsensing data with differential privacy guarantees. Crowd-ML endows a crowdsensing system with an ability to learn classifiers or predictors online from crowdsensing data privately with minimal computational overheads on devices and servers, suitable for a practical and large-scale employment of the framework. We analyze the performance and the scalability of Crowd-ML, and implement the system with off-the-shelf smartphones as a proof of concept. We demonstrate the advantages of Crowd-ML with real and simulated experiments under various conditions

Coulomb-coupled quantum-dot thermal transistors

A quantum-dot thermal transistor consisting of three Coulomb-coupled quantum dots coupled to respective electronic reservoirs by tunnel contacts is established. The heat flows through the collector and emitter can be controlled by the temperature of the base. It is found that a small change in the base heat flow can induce a large heat flow change in the collector and emitter. The huge amplification factor can be obtained by optimizing the Coulomb interaction between the collector and the emitter or by decreasing the energy-dependent tunneling rate at the base. The proposed quantum-dot thermal transistor may open up potential applications in low-temperature solid-state thermal circuits at the nanoscale.Comment: 14 pages, 6 figure

Numerical modeling on the seismic responses of a large underground structure in soft ground

To estimate the earthquake damages of a large subway station built in soft ground, a soil-underground structure static and dynamic coupling interaction model is advanced with the strong nonlinear properties of soil modeled by a developed viscous-plastic constitutive model. The numerical modeling results show that the large underground structure in soft site has a large vertical relative deformation during the horizontal earthquake, which could be larger than its horizontal relative deformation. The dynamic deformation responses of the components near to the middle span of the underground structure are obviously larger those of the other components at the side spans, which means that these components near to the middle span are more apt to be damaged in horizontal earthquake. According to the horizontal relative deformation and the seismic damage process of the large underground structure, which limited elastic working state and the limited elastic-plastic working state are determined, and the maximal interlayer displacement angles are suggested to be 1/430 for the limited elastic working state and 1/185 for the limited elastic-plastic working state. In addition, the seismic soil pressure coefficients on the upper side wall have significant changes. To the large underground structure shown in this paper, the seismic soil pressure coefficients on the top half of the upper side wall should be defined alone in its seismic design

Pseudo-static calculation method of the seismic residual deformation of a geogrid reinforced soil retaining wall with a liquefied backfill

The geogrid reinforced soil retaining wall is a flexible retaining wall. It will produce large deformations during earthquakes, especially on liquefied backfill soils. An index of liquefaction extent is applied to express the effect of excess pore water pressure in reinforced backfill sand during earthquakes. A geogrid reinforced soil retaining wall is represented by an isotropic vertical elastic beam. The calculation method of the seismic residual deformation of the geogrid reinforced soil retaining wall is based on the Rayleigh-Ritz method and the the Mononobe-Okabe pseudo-static method. The effect of liquefaction extent in the backfill sand is studied for seismic active earth pressures acting on a reinforced wall back and seismic residual deformations of a reinforced wall. Some influence parameters on seismic residual deformations of geogrid reinforced soil retaining walls are investigated in detail, such as the internal friction angles in the backfill sand, friction angles of the wall, horizontal seismic intensities, reinforcement length of the geogrid and soil properties. Finally, the calculated results are compared with test results of a model on large-scale shaking table. The conclusions about the parameters will be helpful for seismic designs of geo-grid reinforced soil retaining walls on liquefied foundations. The proposed pseudo-static calculation method can be used to predict safe seismic deformations of geogrid reinforced soil retaining walls

Progress in Plasma-Assisted Catalysis for Carbon Dioxide Reduction

Production of chemicals and fuels based on CO2 conversion is attracting a special attention nowadays, especially regarding the fast depletion of fossil resources and increase of CO2 emissions into the Earth’s atmosphere. Recently, plasma technology has gained increasing interest as a non-equilibrium medium suitable for CO2 conversion, which provides a promising alternative to the conventional pathway for greenhouse gas conversion. The combination of plasma and catalysis is of great interest for turning plasma chemistry in applications related to pollution and energy issues. In this chapter a short review of the current progress in plasma-assisted catalytic processes for CO2 reduction is given. The most widely used discharges for CO2 conversion are presented and briefly discussed, illustrating how to achieve a better energy and conversion efficiency. The chapter includes the recent status and advances of the most promising candidates (plasma catalysis) to obtain efficient CO2 conversion, along with the future outlook of this plasma-assisted catalytic process for further improvement

Vision-based displacement test method for high-rise building shaking table test

The vision-based displacement measurement system was developed, which using digital video camcorder to test the deformation of high-rise structures. It is more economical than contact and contact-less displacement sensors. A series of tests were conducted to investigate the precision, serviceability, and stability of the vision-based displacement method. The results show that, the proposed method can effectively test the dynamic displacement, moreover, the method can be effectively applied to test the displacement caused by vibration which contains various frequency components. Based on the system, the deformation of high-rise building structure was tested. The results show that, the displacement obtained by vision-based can illustrate the free-vibration characteristics of structure well, meanwhile, this method can test bidirectional displacement in shaking table test and practical engineering