Vision-force-fused curriculum learning for robotic contact-rich assembly tasks

Contact-rich robotic manipulation tasks such as assembly are widely studied due to their close relevance with social and manufacturing industries. Although the task is highly related to vision and force, current methods lack a unified mechanism to effectively fuse the two sensors. We consider coordinating multimodality from perception to control and propose a vision-force curriculum policy learning scheme to effectively fuse the features and generate policy. Experiments in simulations indicate the priorities of our method, which could insert pegs with 0.1 mm clearance. Furthermore, the system is generalizable to various initial configurations and unseen shapes, and it can be robustly transferred from simulation to reality without fine-tuning, showing the effectiveness and generalization of our proposed method. The experiment videos and code will be available at https://sites.google.com/view/vf-assembly

Evidence for Exciton Crystals in a 2D Semiconductor Heterotrilayer

Two-dimensional (2D) transition metal dichalcogenides (TMDC) and their moire interfaces have been demonstrated for correlated electron states, including Mott insulators and electron/hole crystals commensurate with moire superlattices. Here we present spectroscopic evidences for ordered bosons - interlayer exciton crystals in a WSe2/MoSe2/WSe2 trilayer, where the enhanced Coulomb interactions over those in heterobilayers have been predicted to result in exciton ordering. While the dipolar interlayer excitons in the heterobilayer may be ordered by the periodic moire traps, their mutual repulsion results in de-trapping at exciton density larger than 10^11 cm^-2 to form mobile exciton gases and further to electron-hole plasmas, both accompanied by broadening in photoluminescence (PL) peaks and large increases in mobility. In contrast, ordered interlayer excitons in the trilayer are characterized by negligible mobility and by sharper PL peaks persisting to nex larger than 10^12 cm^-2. We find that an optically dark state attributed to the predicted quadrupolar exciton crystal transitions to the bright dipolar excitons either with increasing nex or by an applied electric field. These ordered interlayer excitons may serve as models for the exploration of quantum phase transitions and quantum coherent phenomena.Comment: 16 pages, 4 figures, S

Secured green communication scheme for interference alignment based networks

In this paper, a new security and green communication scheme is proposed to the Interference-Alignment (IA) based networks. To achieve a secured communication, full-duplex receivers are utilized to transmit artificial noise (AN). Both the signals and the ANs are used to harvest energy to realize green communication. For these reasons, the feasible conditions of this scheme are analyzed first. Secondly, the average transmission rate, the secrecy performance and the harvested energy are investigated. Thirdly, an optimization scheme of simultaneous wireless information and power transfer (SWIPT) is given to optimize the information transmission and the energy harvesting efficiency. Meanwhile, an improved IA iteration algorithm is designed to eliminate both the AN and the interference. Furthermore, relay cooperation is considered and its system performance is analyzed. The simulations show that the target average transmission rate is not affected by AN, while the secrecy performance can be greatly improved. The energy harvesting efficiency is also better than the traditional schemes. As expected, the average transmission rate further is improved with the relay cooperation

Charge-transfer Contact to a High-Mobility Monolayer Semiconductor

Two-dimensional (2D) semiconductors, such as the transition metal dichalcogenides, have demonstrated tremendous promise for the development of highly tunable quantum devices. Realizing this potential requires low-resistance electrical contacts that perform well at low temperatures and low densities where quantum properties are relevant. Here we present a new device architecture for 2D semiconductors that utilizes a charge-transfer layer to achieve large hole doping in the contact region, and implement this technique to measure magneto-transport properties of high-purity monolayer WSe$_2$. We measure a record-high hole mobility of 80,000 cm$^2$/Vs and access channel carrier densities as low as $1.6\times10^{11}$ cm$^{-2}$, an order of magnitude lower than previously achievable. Our ability to realize transparent contact to high-mobility devices at low density enables transport measurement of correlation-driven quantum phases including observation of a low temperature metal-insulator transition in a density and temperature regime where Wigner crystal formation is expected, and observation of the fractional quantum Hall effect under large magnetic fields. The charge transfer contact scheme paves the way for discovery and manipulation of new quantum phenomena in 2D semiconductors and their heterostructures

Kinetics of ion exchange in binary and ternary systems using strongly acidic cation exchanger: Part 2-Kinetic behaviour and diffusion coefficients in ternary system

1068-1072The three necked flask technique has been empolyed to study the kinetics of ion exchange in ternary system of H+ _ Na+ ­ UO. The kinetic curves have been obtained with changing the fraction of counter ions in bulk solution, the rate of stirring, temperature and resin radius. The particle diffusion coefficients in ternary system has been calculated by fitting the polar-coordination equation, and it has been found that they are of same order as that of corresponding binary systems and the sequence of them is H > Na > uo2 . The selectivity coefficients are also reported, and the sequence of them is exactly opposite to that of particle diffusion coefficients

Kinetics of ion exchange in binary and ternary systems using strongly acidic cation exchanger: Part 1-The mechanisms of ion exchange processes and diffusion coefficients in binary systems

964-968The three-necked flask technique has been employed to study the kinetics of ion exchange in the binary systems of H+ - Na+, H+ - UO and Na+ - UO. The kinetic curves are obtained with changing concentration of bulk solution, rate of stirring, temperature and resin radius. The mechanisms of ion exchange in binary systems have been reported, and the diffusion coefficients for all counter ions in the systems are obtained

Multifunction adsorption materials: Part 1-Interaction of uranium and crystalline TiO₂.mH₂O modified by amorphous SiO₂.nH₂O

677-682The crystalline hydrous titanium dioxide modified by amorphous hydrous silicon dioxide (CTDASD), 2SiO2.3Ti O2.6H2O has been synthesized by ageing the amorphous mixed silicon-titanium hydroxide at 80°C for 36 hours. The prepared material possesses adjustable selectivity and apparent ion exchange capacity for a certain element or even for a group of elements. XRD, TGA and pH titration have been employed to characterize the prepared material. The uptake of uranyl ions on CTDASD is independent of concentration of sodium ions under the experimental conditions investigated, suggesting the material synthesized is reliable to remove uranyl ions from the media of high salt concentration. The uptake of uranium on the CTDASD is remarkably sensitive to the solution pH and reaches the maximum at pH 4.5. Plot of log KD of uranium versus equilibrium pH generates a series of lines with the mean slope of 0.63 at pH 1,→ 4, indicating the sophisticated loading mechanisms in H / UO2+2 reaction

Synthesis of a Novel Spirocyclic Inflatable Flame Retardant and Its Application in Epoxy Composites

Derivatives of 3,9-dichloro-2,4,8,10-tetraoxa-3,9-diphosphaspiro-[5,5]undecane-3,9-dioxide (SPDPC) are of increasing interest as flame retardants for polymeric materials. In addition, SPDPC is also an important intermediate for the preparation of intumescent flame retardants (IFRs). However, low efficiency and undesirable dispersion are two major problems that seriously restrain the application of IFRs as appropriate flame retardants for polymer materials. Usually, the functionalization or modification of SPDPC is crucial to acquiring high-performance polymer composites. Here, a small molecule spirocyclic flame retardant diphenylimidazole spirocyclic pentaerythritol bisphosphonate (PIPC) was successfully prepared through the substitution reaction between previously synthesized intermediate SPDPC and 2-phenylimidazole (PIM). Phenyl group and imidazole group were uniformly anchored on the molecular structure of SPDPC. This kind of more uniform distribution of flame retardant groups within the epoxy matrix resulted in a synergistic flame retardant effect and enhanced the strength of char layers to the epoxy composites, when compared to the unmodified epoxy. The sample reached a limiting oxygen index (LOI) of 29.7% and passed with a V-0 rating in the UL 94 test with the incorporation of only 5 wt% of as-prepared flame retardant PIPC. Moreover, its peak of heat release rate (pHRR) and total heat release (THR) decreased by 41.15% and 21.64% in a cone calorimeter test, respectively. Furthermore, the addition of PIPC has only slightly impacted the mechanical properties of epoxy composites with a low loading

CmWRKY1 Enhances the Dehydration Tolerance of Chrysanthemum through the Regulation of ABA-Associated Genes.

WRKY transcription factors serve as antagonistic or synergistic regulators in a variety of abiotic stress responses in plants. Here, we show that CmWRKY1, a member of the group IIb WRKY family isolated from Chrysanthemum morifolium, exhibits no transcriptional activation in yeast cells. The subcellular localization examination showed that CmWRKY1 localizes to the nucleus in vivo. Furthermore, CmWRKY1-overexpressing transgenic lines exhibit enhanced dehydration tolerance in response to polyethylene glycol (PEG) treatment compared with wild-type plants. We further confirmed that the transgenic plants exhibit suppressed expression levels of genes negatively regulated by ABA, such as PP2C, ABI1 and ABI2, and activated expression levels of genes positively regulated by ABA, such as PYL2, SnRK2.2, ABF4, MYB2, RAB18, and DREB1A. Taken together, our results indicate that CmWRKY1 plays an important role in the response to drought in chrysanthemum through an ABA-mediated pathway