Generative modeling, which learns joint probability distribution from data and generates samples according to it, is an important task in machine learning and artificial intelligence. Inspired by ...probabilistic interpretation of quantum physics, we propose a generative model using matrix product states, which is a tensor network originally proposed for describing (particularly one-dimensional) entangled quantum states. Our model enjoys efficient learning analogous to the density matrix renormalization group method, which allows dynamically adjusting dimensions of the tensors and offers an efficient direct sampling approach for generative tasks. We apply our method to generative modeling of several standard data sets including the Bars and Stripes random binary patterns and the MNIST handwritten digits to illustrate the abilities, features, and drawbacks of our model over popular generative models such as the Hopfield model, Boltzmann machines, and generative adversarial networks. Our work sheds light on many interesting directions of future exploration in the development of quantum-inspired algorithms for unsupervised machine learning, which are promisingly possible to realize on quantum devices.
Green building is one of measures been put forward to mitigate significant impacts of the building stock on the environment, society and economy. However, there is lack of a systematic review of this ...large number of studies that is critical for the future endeavor. The last decades have witnessed rapid growing number of studies on green building. This paper reports a critical review of the existing body of knowledge of researches related to green building. The common research themes and methodology were identified. These common themes are the definition and scope of green building; quantification of benefits of green buildings compared to conventional buildings; and various approaches to achieve green buildings. It is found that the existing studies played predominately focus on the environmental aspect of green building. Other dimensions of sustainability of green building, especially the social sustainability is largely overlooked. Future research opportunities were identified such as effects of climatic conditions on the effectiveness of green building assessment tools, validation of real performance of green buildings, unique demands of specific population, and future proofing.
The development of efficient and sustainable methods to access saturated N‐heterocycles is of great importance because of the prevalence of these structures in natural products and bioactive ...compounds. Pd‐catalyzed aza‐Wacker type cyclization is a powerful method and provides access to N‐heterocycles bearing an alkene moiety available for further synthetic manipulations from readily available materials. Herein we disclose a catalyst‐ and reagent‐free formal aza‐Wacker type cyclization reaction for the synthesis of functionalized saturated N‐heterocycles. Key to the success is to conduct the reactions in a continuous‐flow electrochemical reactor without adding supporting electrolyte or additives. The reactions are characterized by broad tolerance of di‐, tri‐ and tetrasubstituted alkenes.
A continuous‐flow electrochemical aza‐Wacker‐type cyclization reaction that is free of catalyst, oxidant, supporting electrolyte, and additives is presented. The method is scalable and compatible with di‐, tri‐, and tetrasubstituted alkenes.
Oil sorbents play a very important part in the remediation processes of oil spills. To enhance the oil‐sorption properties and simplify the oil‐recovery process, various advanced oil sorbents and ...oil‐collecting devices based on them have been proposed recently. Here, we firstly discuss the design considerations for the fabrication of oil sorbents and describe recently developed oil sorbents based on modification strategy. Then, recent advances regarding oil sorbents mainly based on carbon materials and swellable oleophilic polymers are also presented. Subsequently, some additional properties are emphasized, which are required by oil sorbents to cope with oil spills under extreme conditions or to facilitate the oil‐collection processes. Furthermore, some oil‐collection devices based on oil sorbents that have been developed recently are shown. Finally, an outlook and challenges for the next generation of oil‐spill‐remediation technology based on oil‐sorbents materials are given.
Hydrophobic and oleophilic sorbent materials are demonstrated as promising candidates for the cleanup of oil spills. An overview of the latest developments and advances in the fabrication of oil sorbents through modification strategy, carbon‐based oil sorbents, and polymer‐based oil sorbents, as well as some smart oil sorbents and oil‐collecting devices based on oil‐sorbent materials are presented.
Abstract
By combining the Large Sky Area Multi-object Fiber Spectroscopic Telescope and Gaia data, we investigate the vertical phase mixing across the Galactic disk. Our results confirm the existence ...of phase space snail shells (or phase spirals) from 6–12 kpc. We find that grouping stars by the guiding radius (
R
g
), instead of the present radius (
R
), further enhances the snail shell signal in the following aspects: (1) clarity of the snail shell shape is increased; (2) more wraps of the snail shell can be seen; (3) the phase spaces are less affected by the lack of stars closer to the disk midplane due to extinction; and (4) the phase space snail shell is amplified in greater radial ranges. Compared to the
R
-based snail shell, the quantitatively measured shapes are similar, except that the
R
g
-based snail shells show more wraps with a better contrast. These lines of evidence lead to the conclusion that the guiding radius (angular momentum) is a fundamental parameter tracing the phase space snail shell across the Galactic disk. Results of our test particle simulations with impulse approximation verify that particles grouped according to
R
g
reveal well-defined and sharper snail shell features. By comparing the radial profiles of the snail shell pitch angle between the observation and simulation, the external perturbation can be constrained to ∼500−700 Myr ago. For future vertical phase mixing study, it is recommended to use the guiding radius with additional constraints on orbital hotness (ellipticity) to improve the clarity of the phase snail.
Conductive polymers combine the attractive properties associated with conventional polymers and unique electronic properties of metals or semiconductors. Recently, nanostructured conductive polymers ...have aroused considerable research interest owing to their unique properties over their bulk counterparts, such as large surface areas and shortened pathways for charge/mass transport, which make them promising candidates for broad applications in energy conversion and storage, sensors, actuators, and biomedical devices. Numerous synthetic strategies have been developed to obtain various conductive polymer nanostructures, and high-performance devices based on these nanostructured conductive polymers have been realized. This Tutorial review describes the synthesis and characteristics of different conductive polymer nanostructures; presents the representative applications of nanostructured conductive polymers as active electrode materials for electrochemical capacitors and lithium-ion batteries and new perspectives of functional materials for next-generation high-energy batteries, meanwhile discusses the general design rules, advantages, and limitations of nanostructured conductive polymers in the energy storage field; and provides new insights into future directions.
Nanostructured conductive polymers (nCPs) have aroused considerable research interest owing to their unique properties over their bulk counterparts, such as high electrical conductivity, large surface areas, and shortened pathways for charge/mass transport. These advantageous features make them promising candidates for applications in energy storage devices.
Novel 3D Ni1−xCoxSe2 mesoporous nanosheet networks with tunable stoichiometry are successfully synthesized on Ni foam (Ni1−xCoxSe2 MNSN/NF with x ranging from 0 to 0.35). The collective effects of ...special morphological design and electronic structure engineering enable the integrated electrocatalyst to have very high activity for hydrogen evolution reaction (HER) and excellent stability in a wide pH range. Ni0.89Co0.11Se2 MNSN/NF is revealed to exhibit an overpotential (η10) of 85 mV at −10 mA cm−2 in alkaline medium (pH 14) and η10 of 52 mV in acidic solution (pH 0), which are the best among all selenide‐based electrocatalysts reported thus far. In particular, it is shown for the first time that the catalyst can work efficiently in neutral solution (pH 7) with a record η10 of 82 mV for all noble metal‐free electrocatalysts ever reported. Based on theoretical calculations, it is further verified that the advanced all‐pH HER activity of Ni0.89Co0.11Se2 is originated from the enhanced adsorption of both H+ and H2O induced by the substitutional doping of cobalt at an optimal level. It is believed that the present work provides a valuable route for the design and synthesis of inexpensive and efficient all‐pH HER electrocatalysts.
An integrated electrocatalyst comprising 3D mesoporous Ni0.89Co0.11Se2 nanosheet networks on Ni foam is synthesized, and it demonstrates very high activities and excellent stabilities for hydrogen evolution reaction (HER) in all‐pH conditions. Theoretical calculations verify that electronic structure engineering by optimal Co doping enhances the adsorption of H+ and H2O, leading to the advanced all‐pH HER activity of the catalyst.
Superelastic carbon aerogels have been widely explored by graphitic carbons and soft carbons. These soft aerogels usually have delicate microstructures with good fatigue resistance but ultralow ...strength. Hard carbon aerogels show great advantages in mechanical strength and structural stability due to the sp3‐C‐induced turbostratic “house‐of‐cards” structure. However, it is still a challenge to fabricate superelastic hard carbon‐based aerogels. Through rational nanofibrous structural design, the traditional rigid phenolic resin can be converted into superelastic hard carbon aerogels. The hard carbon nanofibers and abundant welded junctions endow the hard carbon aerogels with robust and stable mechanical performance, including superelasticity, high strength, extremely fast recovery speed (860 mm s−1), low energy‐loss coefficient (<0.16), long cycle lifespan, and heat/cold‐endurance. These emerging hard carbon nanofiber aerogels hold a great promise in the application of piezoresistive stress sensors with high stability and wide detection range (50 kPa), as well as stretchable or bendable conductors.
A family of hard carbon aerogels with nanofibrous structure templated by various nanofibers is fabricated, displaying robust and stable mechanical performances, including high strength, extremely fast recovery speed (860 mm s−1), and ultralow energy loss coefficient (<0.16). After being compressed for 104 cycles (50% strain), they show only ≈2% plastic deformation and retain ≈93% stress.
Widely used disposable plastic tableware is usually buried or directly discharged into the natural environment after using, which poses potential threats to the natural environment and human health. ...To solve this problem, nondegradable plastic tableware needs to be replaced by tableware composed of biodegradable structural materials with both food safety and the excellent mechanical and thermal properties. Here, a food‐safe sargassum cellulose nanofiber (SCNF) is extracted from common seaweed in an efficient and low energy consuming way under mild reaction conditions. Then, by assembling the SCNF into a dense bulk material, a strong sargassum cellulose nanofiber structural material (SCNSM) with high strength (283 MPa) and high thermal stability (>160 °C) can be prepared. The SCNSM also possesses good machinability, which can be processed into tableware with different shapes, e.g., knives and forks. The overall performance of the SCNSM‐based tableware is better than commercial plastic, wood‐based, and poly(lactic acid) tableware, which shows great application potential in the tableware field.
A food‐safe sargassum cellulose nanofiber (SCNF) is extracted through an efficient and low energy consuming way. Then, by assembling the SCNF into a dense bulk material, a strong structural material can be prepared. It possesses good machinability, which can be processed into tableware with better overall performance than that of commercial tableware, showing great application potential in the tableware field.
An All‐Natural Wood‐Inspired Aerogel Han, Zi‐Meng; Sun, Wen‐Bin; Yang, Kun‐Peng ...
Angewandte Chemie International Edition,
February 1, 2023, 2023-Feb-01, 2023-02-00, 20230201, Letnik:
62, Številka:
6
Journal Article
Recenzirano
The oriented pore structure of wood endows it with a variety of outstanding properties, among which the low thermal conductivity has attracted researchers to develop wood‐like aerogels as excellent ...thermal insulation materials. However, the increasing demands of environmental protection have put forward new and strict requirements for the sustainability of aerogels. Here, we report an all‐natural wood‐inspired aerogel consisting of all‐natural ingredients and develop a method to activate the surface‐inert wood particles to construct the aerogel. The obtained wood‐inspired aerogel has channel structure similar to that of natural wood, endowing it with superior thermal insulation properties to most existing commercial sponges. In addition, remarkable fire retardancy and complete biodegradability are integrated. With the above outstanding performances, this sustainable wood‐inspired aerogel will be an ideal substitute for the existing commercial thermal insulation materials.
An interesting surface nanocrystallization method was developed to make the surface‐inert and weakly interacting wood particles better assemble to construct the aerogel. This bottom‐up method allows the preparation of large‐size composite aerogels. The wood‐inspired oriented channel structure endows the obtained aerogel with superior thermal insulation properties to natural wood and most existing commercial sponges.
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