Chemical composition tuning in quaternary p-type Pb-chalcogenides – a promising strategy for enhanced thermoelectric performance

Recently a significant improvement in the thermoelectric performance of p-type ternary PbTe–PbSe and PbTe–PbS systems has been realized through alternating the electronic band structure and introducing nano-scale precipitates to bulk materials respectively. However, the quaternary system of PbTe–PbSe–PbS has received less attention. In the current work, we have excluded phase complexity by fabricating single phase sodium doped PbTe, alloyed with PbS up to its solubility limit which is extended to larger concentrations than in the ternary system of PbTe–PbS due to the presence of PbSe. We have presented a thermoelectric efficiency of approximately 1.6 which is superior to ternary PbTe–PbSe and PbTe–PbS at similar carrier concentrations and the binary PbTe, PbSe and PbS alloys. The quaternary system shows a larger Seebeck coefficient than the ternary PbTe–PbSe alloy, indicative of a wider band gap, valence band energy offset and heavier carriers effective mass. In addition, the existence of PbS in the alloy further reduces the lattice thermal conductivity originated from phonon scattering on solute atoms with high contrast atomic mass. Single phase quaternary PbTe–PbSe–PbS alloys are promising thermoelectric materials that provide high performance through adjusting the electronic band structure by regulating chemical composition

Investigation on the pressurized discharge performance from a liquid oxygen tank under different injected gas temperatures

Accurate prediction on the pressurized discharge performance is significant to the safety operation of cryogenic propellant system. In the present study, a two-dimensional numerical model is established to simulate the fuel outflow with high-temperature gas injection. Both the environmental heat invasion and interfacial phase change are detailedly considered. The volume of fluid method is used to predict the distribution of the liquid-vapor interface, and the low Re k-ε turbulent model is adopted to simulate the pressurized discharge of liquid oxygen. The liquid hydrogen discharge tests, under the gas hydrogen injection, are selected to validate the developed numerical model, and the fluid temperature of the symmetry axis of the liquid hydrogen tank is selected as the comparison parameter. It shows that the present numerical model has good prediction accuracy with calculation deviations being less than 20%. Based on the developed numerical model, the effect of the injected gas temperature on the pressurized discharge of liquid oxygen is investigated and analyzed. Some valuable conclusions are achieved. The present work could strengthen the researchers’ understanding on the thermodynamic behavior during pressurized discharge and might supply some technique supports for the design and optimization of cryogenic propellant systems

The Line-broken Analysis of the Aluminum Conductor Composite Core

Aluminum conductor composite core has many technical advantages such as high tensile strength, light weight, low sag, large current carrying capacity. In order to study the influence of the broken of aluminum conductor composite core on the transmission tower, tower-line model was built by using the finite element software ANSYS/LS-DYNA, and the deformation of joints and stress of bar were analyzed. The impact load and the impact coefficient of the representative bars of the transmission tower are calculated. The results show that the impact acting on the tower is the most serious in the place of the conductor suspension point, the connection of upper and lower crank arms, the tower neck

Optimization of the photovoltaic performance of ZnO-based organic-inorganic hybrid solar cells

Organic-inorganic hybrid solar cell is a new type of solar cell, with its organic polymers to provide electrons and inorganic semiconductors to accept electrons. The commonly used inorganic semiconductors are nano-sized zinc oxide (ZnO), titanium dioxide (TiO2), cadmium sulfide (CdS), etc. There are many problems needing to be solved in the research process of hybrid solar cells, such as the poor electron transport efficiency, low utilization of solar energy, chemical incompatibility between inorganic semiconductors and organic polymers, and the consequently caused low photoelectric conversion efficiency. Around the above issues, concerning the solar cell with the ZnO semiconductors as electron acceptor, the photovoltaic performance optimization methods are discussed from the aspects of electron acceptors, electron donor materials and the addition of modified layers for the ZnO-based solar cell, and the future development tendency of the hybrid solar cells is also prospected. The optimization of cell performance has brought hope to the low cost and high efficiency application of this hybrid solar cell

Protective Effect of <i>Lycium ruthenicum</i> Polyphenols on Oxidative Stress against Acrylamide Induced Liver Injury in Rats

Acrylamide (ACR) is formed during tobacco and carbohydrate-rich food heating and is widely applied in many industries, with a range of toxic effects. The antioxidant properties of Lycium ruthenicum polyphenols (LRP) have been established before. This study aimed to research the protective effect of LRP against ACR-induced liver injury in SD rats. Rats were divided into six groups: Control, ACR (40 mg/kg/day, i.g.), LRP (50, 100, and 200 mg/kg/day, i.g.) plus ACR, and LRP groups. After 19 days, we evaluated oxidative status and mitochondrial functions in the rat’s liver. The results showed that glutathione (GSH) and superoxide dismutase (SOD) levels increased after LRP pretreatment. In contrast, each intervention group reduced reactive oxygen species (ROS) and malondialdehyde (MDA) levels compared to the ACR group. Meanwhile, alanine aminotransferase (ALT), aspartate aminotransferase (AST), liver mitochondrial ATPase activity, mRNA expression of mitochondrial complex I, III, and expression of nuclear factor-erythroid 2-related factor 2 (Nrf2) and its downstream proteins were all increased. This study suggested that LRP could reduce ACR-induced liver injury through potent antioxidant activity. LRP is recommended as oxidative stress reliever against hepatotoxicity

Public Health Emergency Command System of China

China has formed a national emergency management system consisting of “one contingency plan and three sets of institutions” since the outbreak of the severe acute respiratory syndrome (SARS) in 2003. This system is further improved after the establishment of the Ministry of Emergency Management in 2018 and the great achievements made in the fight against the coronavirus disease 2019 (COVID-19). This study aims to improve China’s public health emergency command system via investigating the history, current status, and challenges of the system. In this article, we summarize the emergency command systems responding to the SARS outbreak, the H1N1 2009 pandemic, and the COVID-19 pandemic using literature research, theoretical analysis, and case comparison. China’s public health emergency command system played a significant role in dealing with these public health emergencies and has been increasingly improved; however, it still faces various challenges. Therefore, we propose several policy suggestions to address these challenges, which involve the aspects of joint prevention and control mechanism, law system for public health emergencies, advisory board, and central–local relations

Quick and Automatic Generation Method for the Evaluation Report of the Small Hydropower Substitute Fuel Project

International audienceThe small hydropower substitute fuel (SHSF) project is a commonweal project, give prominence to the ecology benefit. The manager of SHSF need a full and specification report for the evaluation results, rather than a database or a simple data of the result. So, based on the characteristics of the management and evaluation system of SHSF project, this paper presents a multi-indicator comprehensive evaluation module and report template, which includes environmental impacts on climate change, conversion of cropland to forest and natural forest protection project, greenhouse gas emission and the role of social and poverty alleviation. In order to achieve automated building of the comprehensive evaluation report of the small hydropower replacing firewood project, a quick and automatic generation method is constructed for the evaluation report based on C# .Net development environment. It produces evaluation report by reading, traversing and replacing the corresponding position data placeholder of customized multi-indicator evaluation report template. The results showed that the quick and automatic generation method meets the requirements of the management and evaluation system of the small hydropower replacing firewood project successfully, and can be referenced in study and practical application

Double Sandwich Polyoxometalate and Its Fe(III) Substituted Derivative, [As₂Fe₅Mo₂₁O₈₂]^17– and [As₂Fe₆Mo₂₀O₈₀(H₂O)₂]^16–

A double sandwich polyoxometalate and its Fe­(III) substituted derivative, [As₂Fe₅Mo₂₁O₈₂]^17– (<b>1</b>) and [As₂Fe₆Mo₂₀O₈₀(H₂O)₂]^16– (<b>2</b>), were synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy, fluorescent spectroscopy, UV spectra, thermogravimetry-differential scanning calorimetry analyses, electrospray ionization mass spectrometry, and magnetism measurements. The polyoxoanion is composed of a central fragment FeMo₇O₂₈ for <b>1</b> (Fe₂Mo₆O₂₆(H₂O)₂ for <b>2</b>) and two external AsMo₇O₂₇ fragments linked together by two distinct edge-sharing dimeric clusters Fe₂O₁₀ to lead to a <i>C</i>_2<i>v</i> molecular symmetry. The central FeMo₇O₂₈ fragment and external AsMo₇O₂₇ fragment have a similar structure, and both of them can be viewed as a monocapped hexavacant α-Keggin subunit with a central FeO₄ group or a central AsO₃ group. Both of the polyoxoanions contain a oxo-bridged Fe^III₅ magnetic core with the angles of Fe–O–Fe in the range of 96.4(4)–125.7(5)°, and magnetism measurements show an overall ferromagnetic interactions among the five-nuclearity cluster Fe₅ with the spin ground state <i>S</i> = 15/2

Double Sandwich Polyoxometalate and Its Fe(III) Substituted Derivative, [As₂Fe₅Mo₂₁O₈₂]^17– and [As₂Fe₆Mo₂₀O₈₀(H₂O)₂]^16–

A double sandwich polyoxometalate and its Fe­(III) substituted derivative, [As₂Fe₅Mo₂₁O₈₂]^17– (<b>1</b>) and [As₂Fe₆Mo₂₀O₈₀(H₂O)₂]^16– (<b>2</b>), were synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy, fluorescent spectroscopy, UV spectra, thermogravimetry-differential scanning calorimetry analyses, electrospray ionization mass spectrometry, and magnetism measurements. The polyoxoanion is composed of a central fragment FeMo₇O₂₈ for <b>1</b> (Fe₂Mo₆O₂₆(H₂O)₂ for <b>2</b>) and two external AsMo₇O₂₇ fragments linked together by two distinct edge-sharing dimeric clusters Fe₂O₁₀ to lead to a <i>C</i>_2<i>v</i> molecular symmetry. The central FeMo₇O₂₈ fragment and external AsMo₇O₂₇ fragment have a similar structure, and both of them can be viewed as a monocapped hexavacant α-Keggin subunit with a central FeO₄ group or a central AsO₃ group. Both of the polyoxoanions contain a oxo-bridged Fe^III₅ magnetic core with the angles of Fe–O–Fe in the range of 96.4(4)–125.7(5)°, and magnetism measurements show an overall ferromagnetic interactions among the five-nuclearity cluster Fe₅ with the spin ground state <i>S</i> = 15/2

Double Sandwich Polyoxometalate and Its Fe(III) Substituted Derivative, [As₂Fe₅Mo₂₁O₈₂]^17– and [As₂Fe₆Mo₂₀O₈₀(H₂O)₂]^16–

A double sandwich polyoxometalate and its Fe­(III) substituted derivative, [As₂Fe₅Mo₂₁O₈₂]^17– (<b>1</b>) and [As₂Fe₆Mo₂₀O₈₀(H₂O)₂]^16– (<b>2</b>), were synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy, fluorescent spectroscopy, UV spectra, thermogravimetry-differential scanning calorimetry analyses, electrospray ionization mass spectrometry, and magnetism measurements. The polyoxoanion is composed of a central fragment FeMo₇O₂₈ for <b>1</b> (Fe₂Mo₆O₂₆(H₂O)₂ for <b>2</b>) and two external AsMo₇O₂₇ fragments linked together by two distinct edge-sharing dimeric clusters Fe₂O₁₀ to lead to a <i>C</i>_2<i>v</i> molecular symmetry. The central FeMo₇O₂₈ fragment and external AsMo₇O₂₇ fragment have a similar structure, and both of them can be viewed as a monocapped hexavacant α-Keggin subunit with a central FeO₄ group or a central AsO₃ group. Both of the polyoxoanions contain a oxo-bridged Fe^III₅ magnetic core with the angles of Fe–O–Fe in the range of 96.4(4)–125.7(5)°, and magnetism measurements show an overall ferromagnetic interactions among the five-nuclearity cluster Fe₅ with the spin ground state <i>S</i> = 15/2