arXiv subjects

Jiangbin Su

Publications and source records attributed to Jiangbin Su.

9 recordsLinked to original sources

arXiv2019

CrowdOS: A Ubiquitous Operating System for Crowdsourcing and Mobile Crowd Sensing

With the rise of crowdsourcing and mobile crowdsensing techniques, a large number of crowdsourcing applications or platforms (CAP) have appeared. In the mean time, CAP-related models and frameworks based on different research hypotheses are rapidly emerging, and they usually address specific issues from a certain perspective. Due to different settings and conditions, different models are not compatible with each other. However, CAP urgently needs to combine these techniques to form a unified framework. In addition, these models needs to be learned and updated online with the extension of crowdsourced data and task types, thus requiring a unified architecture that integrates lifelong learning concepts and breaks down the barriers between different modules. This paper draws on the idea of ubiquitous operating systems and proposes a novel OS (CrowdOS), which is an abstract software layer running between native OS and application layer. In particular, based on an in-depth analysis of the complex crowd environment and diverse characteristics of heterogeneous tasks, we construct the OS kernel and three core frameworks including Task Resolution and Assignment Framework (TRAF), Integrated Resource Management (IRM), and Task Result quality Optimization (TRO). In addition, we validate the usability of CrowdOS, module correctness and development efficiency. Our evaluation further reveals TRO brings enormous improvement in efficiency and a reduction in energy consumption.

cs.CY↗

arXiv2018

Nanoinstabilities of Cu2O porous nanostructured films as driven by nanocurvature effect and thermal activation effect

In this work, the instabilities at the nanoscale (i.e. nanoinstabilities) of triangular pyramids-like Cu2O porous nanostructured films (PNFs) are studied by heating treatments under different atmosphere and temperature. It is found that the nanoscale building triangular-pyramids turn round preferentially at the sharp angles and/or coalesce with their contacting ones by directional diffusion and plastic flow of atoms, which are driven by the nonuniformly-distributed surface nanocurvature. As a result, the triangular pyramids become quasi-sphere shape and the PNF evolves into a big, dense particles film. It is also observed that the heating or thermal activation effect efficiently promotes the reduction or oxidation of Cu2O pyramids and the crystallization or growth of the as-achieved Cu or CuO grains. The above physical and chemical instabilities or changes at the nanoscale of Cu2O PNFs can be well accounted for by the combined mechanism of nanocurvature effect and thermal activation effect. The nanocurvature effect can lower the energy barrier for the atom diffusion or plastic flow and lower the activation energy for the chemical reactions, while the thermal activation effect can supply the required kinetic energy or activation energy and make the atomic transportations and reactions kinetically possible. The findings reveal the evolution laws of morphology, crystal structure and composition of triangular pyramids-like Cu2O PNF during heating treatments, which can further be extended to other types of Cu2O PNFs. Also, the findings have important implications for the nanoinstabilities of Cu2O PNFs-based devices, especially those working at a high temperature.

cond-mat.mtrl-sci↗

arXiv2018

Cu2O porous nanostructured films fabricated by positive bias sputtering deposition

In this work, the authors fabricated Cu2O porous nanostructured films (PNFs) on glass slide substrates by the newly developed positive bias deposition approach in a balanced magnetron sputtering (MS) system. It was found that the surface morphology, crystal structure and optical property of the as-deposited products were greatly dependent on the applied positive substrate bias. In particular, when the substrate was biased at +50 V and +150 V, both of the as-prepared Cu2O PNFs exhibited a unique triangular pyramids-like structure with obvious edges and corners and little gluing, a preferred orientation of (111) and a blue shift of energy band gap at 2.35 eV. Quantitative calculation results indicated that the traditional bombardment effects of electrons and sputtering argon ions were both negligible during the bias deposition in the balanced MS system. Instead, a new model of tip charging effect was further proposed to account for the controllable formation of PNFs by the balanced bias sputtering deposition.

cond-mat.mtrl-sci↗

arXiv2017

In-situ TEM observation of preferential amorphization in single crystal Si nanowire

The nanoinstability of single crystal Si nanowire under focused electron beam irradiation was in-situ investigated at room temperature by transmission electron microscopy technique. It was observed that the Si nanowire amorphized preferentially from the surface towards the center with the increasing of electron dose. In contrast, in the center of the Si nanowire the amorphization seemed non-uniform and much more difficult accompanying with rotation of crystal grains and compression of d-spacing. Such a selectively preferential amorphization as athermally induced by the electron beam irradiation can be well accounted for by our proposed concepts of nanocurvature effect and energetic beam-induced athermal activation effect, while the classical knock-on mechanism and the electron beam heating effect seem inadequate to explain these processes. Furthermore, the findings revealed the difference of amorphization between Si nanowire and Si film under focused electron beam irradiation. Also, the findings have important implications for nanostability and nanoprocessing of future Si nanowire-based devices.

cond-mat.mes-hall↗

arXiv2017

Metal passivation effect on focused beam-induced nonuniform structure changes of amorphous SiOx nanowire

Passivation effect of heterogeneous Au nanoparticles (AuNPs) on the nonuniform structure changes of amorphous SiOx nanowire (a-SiOx NW) as athermally induced by focused electron beam (e-beam) irradiation is investigated in an in-situ transmission electron microscope. It is found that at room temperature the straight and uniform a-SiOx NW demonstrates an accelerated necking at the nanoscale along with a fast, plastic elongation and a local S-type deformation in the axial direction. However, once being modified with uniform AuNPs, the nanocurved sidewall surface of a-SiOx NW becomes intriguingly passivated and the processing transfers from a diffusion (or plastic flow)-dominated status to an evaporation (or ablation)-dominated status. As a result, the necking of the AuNPs-modified a-SiOx NW is greatly retarded without visible elongation and bending deformation. Two combined effects of nanocurvature and beam-induced soft mode and instability of atomic vibration are further proposed to elucidate the observed new phenomena.

physics.app-ph↗

arXiv2017

Uniform e-beam irradiation-induced athermal straightening of axially curved amorphous SiOx nanowire

The reshaping of amorphous SiOx nanowires (a-SiOx NWs) as purely induced by uniform electron beam (e-beam) irradiation was in-situ studied at room temperature in transmission electron microscope. It was observed that the axially straight NW kept its perfect straight cylinder-like wire shape and demonstrated a sequential uniform radial shrinkage with the increase of irradiation time. In contrast, the axially curved NW turned straight quickly accompanied with a uniform axial shrinkage and a uniform radial expansion intriguingly. It is expected that such a study especially on the straightening of axially curved NW has important implications for the nanoscale processing and stability of future NW-based structures or devices. More importantly, the findings demonstrate that the traditional knock-on mechanism and electron beam heating effect are inadequate to explain these processes while our proposed nanocurvature effect and energetic beam-induced athermal activation effect obviously dominate the processes.

cond-mat.mes-hall↗

arXiv2017

Intriguing uniform elongation and accelerated radial shrinkage in amorphous SiOx nanowire as purely induced by uniform electron beam irradiation

An intriguing athermal uniform elongation and accelerated radial shrinkage in amorphous SiOx nanowire (a-SiOx NW) as purely induced by uniform electron beam (e-beam) irradiation were in-situ investigated in transmission electron microscope. It was observed that at room temperature the straight and uniform a-SiOx NW demonstrated a uniform plastic elongation (without any external tensile pulling) and a corresponding uniform radial shrinkage. According to a new model taking into account the NW nanocurvature over its surface as well as the beam-induced athermal activation, a kinetic relationship between the shrinking radius and the irradiation time was established. The fitting results demonstrated that a curvature-dependent surface energy at the nanoscale (so-called nanocurvature effect) much higher than that predicted from the existing theories is exerted on the elongation and shrinkage of the NW. At the same time, the so-induced plastic flow of massive atom and surface diffusion of atom presented as well a further direct experimental evidence for our predicted soft mode and instability of atomic vibration as induced under energetic beam (including e-beam) irradiation in amorphous materials The study has important implications for the nanoprocessing or nanostability of future NW-based structures or devices. More importantly, it further demonstrates that the nanocurvature effect and the beam-induced atomic vibration soft mode and instability effect, which have been normally neglected or inadequately taken into account in the current literature, are universal concepts and applicable to explanation of energetic beam-induced nanoinstability or nanoprocessing of low dimensional nanostructure in general.

cond-mat.mes-hall↗

arXiv2014

Microstructure-dependent oxidation-assisted dealloying of Cu0.7Al0.3 thin films

In this paper, the oxidation-assisted dealloying (OAD) of Cu0.7Al0.3 films with different microstructures which were obtained by high vacuum annealing at different temperatures were studied using powder X-ray diffraction, field-emission scanning electron microscopy and energy dispersive X-ray analysis. It was observed that different microstructures such as eutectic mixture or solid solution, the grain size of Cu or Al component in eutectic-mixture Cu0.7Al0.3 films affected the corrosion morphology greatly. It thus provided a practical route to fabricate flexible CuO porous nanostructure-films (PNFs) with controllable pore size, porosity, block size and shape. Further, the underlying OAD mechanisms for the structure-resultant different corrosion morphologies of Cu0.7Al0.3 films were also explored. In these senses, the study is suggestive and crucial to both the mechanism understanding of OAD process and the technical controlling of PNF fabrication.

cond-mat.mtrl-sci↗

arXiv2014

Oxidation of copper during physical sputtering deposition: mechanism, avoidance and utilization

In this paper, oxidation of Cu during physical sputtering deposition in a high purity and low pressure Ar atmosphere without introducing O2 gas flow was studied systemically. It was found that various flexible Cu-based films could be obtained by simply adjusting deposition parameters. Electrical and optical testing results showed that the achieved pure Cu films and Cu+Cu2O composite films both presented an intriguing combination of metal and semiconductor characteristics. It is expected that such Cu-based films with a superior conductivity and a solar-window bandgap may have fascinating potential applications such as in high electron mobility transistors, electrodes and solar cells. Further, the oxidation mechanisms of Cu under different deposition parameters and the main O2 source during physical sputtering deposition were also explored.

cond-mat.mtrl-sci↗