484 research outputs found
Functionalization of molecules in confined space
Light-driven molecular motors are unique photoresponsive molecules which can undergo continuous 360 degree unidirectional rotation. However, most of the studies on molecular motors thus far have been conducted in solution and focused on their multi-stage switching behavior. On the other hand, existing reports on photoswitches have revealed that cooperative effects may arise via incorporation into host architectures, which differentiate the assembled systems from simple photoswitching molecules. Aiming to obtain specific functions of motor-based systems, this thesis predominantly focuses on the functionalization of molecular motors into confined space, in aggregates and on particle surfaces. While studying the rotary behavior of motors, we also focus on the cooperative effects that these assembled systems generate. In addition, in these systems, we have made initial attempts to utilize the dynamic rotary motion of molecular motors to perform work
Effect of interaction with neutrons in matter on flavor conversion of super-light sterile neutrino with active neutrino
A super-light sterile neutrino was proposed to explain the absence of the
expected upturn of the survival probability of low energy solar boron
neutrinos. This is because this super-light sterile neutrino can oscillate
efficiently with electron neutrino through a MSW resonance happened in Sun. One
may naturally expect that a similar resonance should happen for neutrinos
propagating in Earth matter. We study the flavor conversion of this super-light
sterile neutrino with active neutrinos in Earth matter. We find that the
scenario of the super-light sterile neutrino can easily pass through possible
constraints from experiments which can test the Earth matter effect in
oscillation of neutrinos. Interestinlgy, we find that this is because the
naively expected resonant conversion disappears or is significantly suppressed
due to the presence of a potential which arises from neutral current
interaction of neutrino with neutrons in matter. In contrast, the neutron
number density in the Sun is negligible and the effect of is effectively
switched off. This enables the MSW resonance in Sun needed in oscillation of
the super-light sterile neutrino with solar electron neutrinos. It's
interesting to note that it is the different situation in the Sun and in the
Earth that makes effectively turned off and turned on respectively. This
observation makes the scenario of the super-light sterile neutrino quite
interesting.Comment: 22 pages, 10 figure
Phenomenological model for coupled multi-axial piezoelectricity
A quantitative calibration of an existing phenomenological model for polycrystalline ferroelectric ceramics is presented. The model relies on remnant strain and polarization as independent variables. Innovative experimental and numerical model identification procedures are developed for the characterization of the coupled electro-mechanical, multi-axial nonlinear constitutive law. Experiments were conducted on thin PZT-5A4E plates subjected to cross-thickness electric field. Unimorph structures with different thickness ratios between PZT-5A4E plate and substrate were tested, to subject the piezo plates to coupled electro-mechanical fields. Material state histories in electric field-strain-polarization space and stress-strain-polarization space were recorded. An optimization procedure is employed for the determination of the model parameters, and the calibrated constitutive law predicts both the uncoupled and coupled experimental observations accurately
Supramolecular control over self-assembly and double thermoresponsive behavior of an amphiphilic block copolymer
A poly(ethylene glycol)-b-poly[N, N-dimethylacrylamide-ran-2-acrylamidoethyl nonanoate] (PEG-b-P(DMA-AAEN)) block copolymer has been demonstrated to show double thermoresponsive behavior in aqueous solution in the presence of hydroxypropylated cyclodextrin (HPCD). The polymer itself is insoluble in water due to the presence of hydrophobic alkyl chain, however, with the presence of HPCD, fully dissolution of the polymer could be obtained indicating the formation of host-guest interaction between HPCD and the alkyl chain. The clear solution of HPCD/polymer complex showing a first thermoresponsiveness during heating and led to the formation of small micelles stabilized by PEG chains and DMA segments. Upon further heating of the aqueous solution, the small micelles aggregated and formed multimicellar aggregates. The reported double thermoresponsive behavior may provide a new strategy of designing smart polymeric systems, which can find broad applications in the fabrication of smart materials
Few-shot Multi-domain Knowledge Rearming for Context-aware Defence against Advanced Persistent Threats
Advanced persistent threats (APTs) have novel features such as multi-stage
penetration, highly-tailored intention, and evasive tactics. APTs defense
requires fusing multi-dimensional Cyber threat intelligence data to identify
attack intentions and conducts efficient knowledge discovery strategies by
data-driven machine learning to recognize entity relationships. However,
data-driven machine learning lacks generalization ability on fresh or unknown
samples, reducing the accuracy and practicality of the defense model. Besides,
the private deployment of these APT defense models on heterogeneous
environments and various network devices requires significant investment in
context awareness (such as known attack entities, continuous network states,
and current security strategies). In this paper, we propose a few-shot
multi-domain knowledge rearming (FMKR) scheme for context-aware defense against
APTs. By completing multiple small tasks that are generated from different
network domains with meta-learning, the FMKR firstly trains a model with good
discrimination and generalization ability for fresh and unknown APT attacks. In
each FMKR task, both threat intelligence and local entities are fused into the
support/query sets in meta-learning to identify possible attack stages.
Secondly, to rearm current security strategies, an finetuning-based deployment
mechanism is proposed to transfer learned knowledge into the student model,
while minimizing the defense cost. Compared to multiple model replacement
strategies, the FMKR provides a faster response to attack behaviors while
consuming less scheduling cost. Based on the feedback from multiple real users
of the Industrial Internet of Things (IIoT) over 2 months, we demonstrate that
the proposed scheme can improve the defense satisfaction rate.Comment: It has been accepted by IEEE SmartNet
Phenomenological model for coupled multi-axial piezoelectricity
A quantitative calibration of an existing phenomenological model for polycrystalline ferroelectric ceramics is presented. The model relies on remnant strain and polarization as independent variables. Innovative experimental and numerical model identification procedures are developed for the characterization of the coupled electro-mechanical, multi-axial nonlinear constitutive law. Experiments were conducted on thin PZT-5A4E plates subjected to cross-thickness electric field. Unimorph structures with different thickness ratios between PZT-5A4E plate and substrate were tested, to subject the piezo plates to coupled electro-mechanical fields. Material state histories in electric field-strain-polarization space and stress-strain-polarization space were recorded. An optimization procedure is employed for the determination of the model parameters, and the calibrated constitutive law predicts both the uncoupled and coupled experimental observations accurately
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