Colorless to black switching with high contrast ratio via the electrochemical process of a hybrid organic-inorganic perovskite

Colorless‐to‐black switching has attracted widespread attention for smart windows and multifunctional displays because they are more useful to control solar energy.However,it still remains a challenge owing to the tremendous difficulties in the design of completely reverse absorptions in transmissive and colored states.Herein,we report on an electrochemical device that can switch between colorless and black by using the electrochemical process of hybrid organic–inorganic perovskite MAPbBr_(3),which shows a high integrated contrast ratio of up to 73%from 400 to 800 nm.The perovskite solution can be used as the active layer to assemble the device,showing superior transmittance over the entire visible region in neutral states.By applying an appropriate voltage,the device undergoes reversible switching between colorless and black,which is attributed to the formation of lead and Br_(2)in the redox reaction induced by the electron transfer process in MAPbBr_(3).In addition,the contrast ratio can be modulated over the entire visible region by changing the concentration and the applied voltage.These results contribute toward gaining an insightful understanding of the electrochemical process of perovskites and greatly promoting the development of switchable devices.

Confirmation of the First Law of Thermodynamics in Theory and Extended Bernoulli Equation

The internal energy change of ideal gas does not depend on the volume and pressure. The internal energy change of real gas has not any relation with the volume and pressure, which had been proved. If the internal energy change had not any relation with the volume and pressure, we could confirm the first law of thermodynamics in theory. Simultaneously, the internal energy change is the state function that shall be able to be proved in theory. If the internal energy change depended on the volume and pressure, we could not prove that the internal energy change is the state function and the chemical thermodynamics theory is right. The extended or modified Bernoulli equation can be derived from the energy conservation law, and the internal energy change, heat, and friction are all considered in the derivation procedure. The extended Bernoulli equation could be applied to the flying aircraft and mechanical motion on the gravitational field, for instance, the rocket and airplane and so on. This paper also revises some wrong ideas, viewpoints, or concepts about the thermodynamics theory and Bernoulli equation.

Synthesis,Crystal Structure and Luminescence of a Novel One-dimensional Silver(Ⅰ)Sulfonate Complex with Pyrazine Ligand

The title complex,[Ag 2 （L1） 2 （Pyr）·2.5H 2 O] 1 （L1=6-amino-1-naphthalenesulfonate anion,Pyr=pyrazine）,has been synthesized and characterized by single-crystal X-ray diffraction analysis.It crystallizes in triclinic,space group P1,with a=7.339（5）,b=13.105（5）,c=14.097（5）,α=84.377（5）,β=76.921（5）,γ=79.628（5）°,V=1296.7（11） 3,C 48 H 50 Ag 4 N 8 O 17 S 4,M r=1570.68,Z=1,D c=2.011 g/cm 3,μ=1.732 mm-1,F（000）=782,S=1.148,the final R=0.0436 and wR=0.1181 for 4130 observer reflections （I 2σ（Ⅰ））.Compound 1 shows a rare one-dimensional （1D） double chain,and the chains are further connected through secondary bonding,hydrogen bonds,and π-π interactions to generate a three-dimensional （3D） supramolecular structure.The luminescent property of 1 was also studied in the solid state at room temperture.

Comparative Analysis of Higher Education Between China and the United States

It is well-known that the United States,a highly developed country whether in high-tech.or higher education,is in a leading position in the world.Based on the comparison and analysis of higher education between China and the U.S.,this article highly affirms the advantages of American higher education,offers an objective comment on China's higher education reform in recent years,and earnestly indicates that China's higher education needs to be improved in order to facilitate greater development.

Economic Research on Ecological Environment of Frigid Region with Black Earth

Suihua City in Heilongjiang Province is located in the heart of the frigid region with black earth and it has created abundant green property resources. However,the environmental issue of this place has caused wide attention,so the government should make full use of various means to solve the environment problem and protect the ecology in this region. Among the measures taken by the government,the tax means is the most effective economic device to solve the environmental problem. Economic means supplemented by lawful and administrative measures should be adopted to solve the ecological environmental problems in the frigid region with black earth.

Hydrothermal Synthesis and Crystal Structure of a New Supramolecular Channel Framework Based on Cu Complexes and Polyoxovanadate:[Cu(I)(phen)_2]_5[HV_(15)O_(36)(Cl)]_(0.65)[H_3V_(16)O_(38)(Cl)]_(0.35)·2H_2O

A new compound [Cu（I）（phen）2]5[HV15O36（Cl）]0.65[H3V16O38（Cl）]0.35·2H2O 1 （phen = 1,10′-phenanthroline） has been prepared from the hydrothermal reaction of V2O5, CuCl, phen, H2C2O4·2H2O, THMAM （tris（hydroxymethyl）aminomethane） and H2O in the molar ratio of 3：1：1：0.5：2.5：1400. Compound 1 crystallizes in the space group P42212 of the tetragonal system with a = b = 21.5009（8）, c = 28.401（2） A, V= 13129.5（12） A^3 Z = 4, Dc = 1.800 g/cm^3, μ（MoKa） = 1.932 mm^-1, λ（MoKa） = 0.71073 A, F（000） = 7063.4, C120H81.20ClCu5N20O38.7V15.35, Mr = 3557.58, the final R = 0.0594 and wR= 0.1320 for 7761 observed reflections （I 〉 2σ（I））. Structure analysis shows that 1 exhibits a 3D channel framework formed by the supramolecular assembly of Cu complexes and polyoxovanadate clusters via intermolecular hydrogen bonding, and the channels contain Cu complexes. Other characterizations by elemental analysis, XPS, IR, XRD and thermal analysis are also described.

A Research on the Behavior of a Polyurethane Polymer Waterproof Material Used in Bridge Geotechnical Applications

Polyurethane is enjoying a widespread use as a polymer-based waterproof material in civil engineering In the present study we consider a temperature-sensitive waterproof and moisture-permeable polyurethane material(PTPE-PU)characterized by one or more phase transition temperatures(critical temperatures).Near the critical temperature,the waterproof and moisture permeability of polyurethane undergo abrupt changes.The related stability,thermal performance,water resistance,hydrostatic pressure,and moisture permeability are investigated here considering a PTPE-PU traditionally used in bridge geotechnical engineering.The results show that the moisture permeability of the coated bridge rock and soil undergo sudden variations near the crystallization and melting temperature of the soft segment.The moisture permeability is 3000 g/(m^(2)d).The hydrostatic pressure of the coated bridge rock and soil is 3.5 kPa.

Current Situations and Future Development Trend of Farmland Pre-warning Researches in China

This paper summarized theory discussion,main research methods,contents,empirical and engineering researches of farmland prewarning in China.It stated that future researches of farmland pre-warning in China will focus on deepening application of farmland security prewarning models,revealing mechanism of changes in different farmland resources,establishing pre-warning models suitable for research areas,accurate evaluation and prediction of farmland security,and exploring establishing and improving farmland security monitoring system and operating mechanism of all levels.

Disinfection Technology for Auricularia auricula in Bag Cultivation:Problems and Countermeasures

This article analyzes the problems existing in disinfection technology for Auricularia auricular in bag cultivation,introduces the concept of disinfection and sterilization technology and the technical status of humidification for disinfection of A.auricular in bag cultivation,analyzes the related problems caused by this type of technology and the reasons for the problems,and puts forward solutions to the technical problems.

Innovative Ideas for the Teaching of Guzheng in Colleges and Universities based on the New Curriculum Reform

As a traditional musical instrument,the guzheng holds a very important status in the Chinese traditional culture.In recent years,with the increase of opportunities for exchanges and cooperation between the West and China,guzheng is rapidly favored in the foreign music circle.As the main institute for cultivating high-level talents in the society,the academic discipline of music in various universities should actively promote the education reform of gxizheng based on the new curriculum reform combined with innovations and modifications of the national instrumental music teaching model to efficiently teach guzheng.

Benign Strategy for Recommended Location Service Based on Trajectory Data

A new collaborative filtered recommendation strategy oriented to trajectory data is proposed for communication bottlenecks and vulnerability in centralized system structure location services. In the strategy based on distributed system architecture, individual user information profiles were established using daily trajectory information and neighboring user groups were established using density measure. Then the trajectory similarity and profile similarity were calculated to recommend appropriate location services using collaborative filtering recommendation method. The strategy was verified on real position data set. The proposed strategy provides higher quality location services to ensure the privacy of user position information.

The Construction and Implementation of a Compound Foreign Language Talent Training Model

With increasing global exchanges and cooperation,there is an increasing demand for foreign language interdisciplinary talents.The cultivation of interdisciplinary foreign language talents is a long-term,complicated methodical endeavor,which requires constant exploration by experts in foreign language circles.In order to cultivate compound foreign language talents in colleges and universities,it is important to change the educational concept,enhance the teaching staff,and innovate the talent training mode.In the training of compound foreign language talents in colleges and universities,a compound talent training model of“foreign language+major or direction”should be established,and beginning from the actual situation of the major,the bold exploration and implementation of the transformation of the concept of compound foreign language talent training should be followed through,while strengthening the construction of teaching staff,optimizing the professional curriculum,updating the teaching content,as well as enriching the methods and measures of teaching.

One-Dimensional Modulational Instability of Broad Optical Beams In Photorefractive Crystals with Both Linear and Quadratic Electro-Optic Effects

We present a theoretical study of the one-dimensional modulational instability of a broad optical beam propagating in a biased photorefractive crystal with both linear and quadratic electro-optic effects(Kerr effect)under steadystate conditions.One-dimensional modulational instability growth rates are obtained by treating the space-charge field equation globally and locally.Both theoretical reasoning and numerical simulation show that both the global and local modulational instability gains are governed simultaneously by the strength and the polarity of external bias field and by the ratio of the intensity of the broad beam to that of the dark irradiance.Under a strong bias field,the results obtained using these two methods are in good agreement in the low spatial frequency regime.Moreover,the instability growth rate increases with the bias field,and the maximum instability growth occurs when ratio of light intensity to dark irradiance is 0.88.

Superhydrophilic nickel hydroxide ultrathin nanosheets enable high-performance asymmetric supercapacitors

Superhydrophilic surfaces have been applied for supercapacitor;however,during energy storage reaction,how the wettability affects the process of electrochemical reaction specifically is still unclear.Herein,we demonstrate superhydrophilic surface for promotion of electrochemical reactions by liquid affinity and further explain the mechanism,where the transition of the wettability state caused by the change in surface free energy is the main reason for the obvious increase in specific capacitance.Through citric acid assistance strategy,an intrinsically hydrophobic Ni(OH)_(2)thick nanosheets(HNHTNs,16 nm)can be transitioned into superhydrophilic Ni(OH)_(2)ultrathin nanosheets(SNHUNs,6.8 nm),where the water contact angle was 0°and the surface free energy increased from 8.6to 65.8 mN·m^(-1),implying superhydrophilicity.Compared with HNHTNs,the specific capacitance of SNHUNs is doubled:from 1230 F·g^(-1)(HNHTNs)to 2350 F·g^(-1)(2A·g^(-1))and,even at 20 A·g^(-1),from 833 F·g^(-1)(HNHTNs)to 1670 F·g^(-1).The asymmetric capacitors assembled by SNHUNs and activated carbon show 52.44 Wh·kg^(-1)at 160W·kg^(-1)and excellent stability with~90%retention after5000 cycles(~80%retention after 9500 cycles).The promotion of electrochemical performances is ascribed to the change of surface wettability caused by surface free energy,which greatly increase affinity of electrode to the surrounding liquid environment to reduce the interface resistance and optimize the electron transport path.

Oxygen Electroreduction on CoSe2 Nanoparticles Prepared via Hydrothermal Method in Acidic Medium

CoSe2 nanoparticles were synthesized via a facile hydrothermal method, and characterized by means of X-ray diffraction（XRD）, scanning electron microscopy（SEM） and transmission electron microscopy（TEM）. The syn- thesized CoSe2 was composed of crystalline orthorhombic phase and displayed a morphology of short and thin nano- belts. The results of the catalyst experiment demonstrate that the CoSe2 nanocrystals show high catalytic activity and methanol tolerance in oxygen reduction reaction（OR_K） with an open circuit potential（OCP） of 0.80 V（vs. NHE） in 0.5 mol/L HzSO4 at 25 ℃. The transfer process of about 3.7 electrons per oxygen molecule was determined during the reduction process and the transfer coefficient and Tafel slope were 0.50 and 118 mV, respectively, in the potential region of 0.64-0.75 V（vs. NHE）. The high catalytic activity might be related to the high crystallization of the CoSe2 powder and the modification of selenium on the cobalt element.

Learning distributed representations for community search using node embedding

1 Introduction and main contributions Community search is a query-dependent variant of community detection problem in social network analysis. Algorithms of this type usually start with a query node preknown to be in the target community, and uncover the remaining nodes in the community. The key challenge in this problem is how to find a proper way to represent network structure as a representation that can be easily exploited by downstream data mining models.

Sensing mechanism of Ag/α-MoO_(3) nanobelts for H_(2)S gas sensor

Sensing mechanism is still a big problem in the field of gas sensor.In-depth study of the sensing mechanism can provide better ideas for the design of sensing materials,and it is also more conducive to the improvement in gas-sensing performance.In this work,Ag/α-MoO_(3) material was obtained by loading Ag in α-MoO_(3) nanobelts prepared by hydrothermal method.The material was characterized by field electron scanning electron microscopy(SEM),high-resolution transmission electron microscopy(HRTEM),X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS).Comparing the gas sensing properties of α-MoO_(3) and Ag/α-MoO_(3),it is found that Ag effectively improves the selectivity of the material to H_(2)S at 133℃.The response of the 5 wt% Ag/α-MoO_(3) sensor to 100 × 10-6 hydrogen sulfide(H_(2)S) is 225 and the detection limit is 100 ×10^(-9).The sensing mechanism was verified by gas chromatography and mass spectrometer(GC-MS),XPS and Fourier transform infrared spectroscopy(FTIR).