含能材料家族族长选拔记

含能材料自出现以来就在民生、国防领域发挥巨大作用。本文作为一篇科普文章,通过拟人的手法,简单介绍了含能材料的基本种类、基本性质,并着重介绍一些重要含能材料的性质和应用。希望能增强读者对含能材料的兴趣,引发读者对含能材料的思考,从而打破对含能材料认知的固有印象。

Bio-Based Waterborne Poly(Vanillin-Butyl Acrylate)/MXene Coatings for Leather with Desired Warmth Retention and Antibacterial Properties

This study presents a solvent-free,facile synthesis of a bio-based green antibacterial agent and aromatic monomer methacrylated vanillin(MV)using vanillin.The resulting MV not only imparted antibacterial properties to coatings layered on leather,but could also be employed as a green alternative to petroleum-based carcinogen styrene(St).Herein,MV was copolymerized with butyl acrylate(BA)to obtain waterborne bio-based P(MV-BA)miniemulsion via miniemulsion polymerization.Subsequently,MXene nanosheets with excellent photothermal conversion performance and antibacterial properties,were introduced into the P(MV-BA)miniemulsion by ultrasonic dispersion.During the gradual solidification of P(MV-BA)/MXene nanocomposite miniemulsion on the leather surface,MXene gradually migrated to the surface of leather coatings due to the cavitation effect of ultrasonication and amphiphilicity of MXene,which prompted its full exposure to light and bacteria,exerting the maximum photothermal conversion efficiency and significant antibacterial efficacy.In particular,when the dosage of MXene nanosheets was 1.4 wt%,the surface temperature of P(MV-BA)/MXene nanocomposite miniemulsioncoated leather(PML)increased by about 15℃ in an outdoor environment during winter,and the antibacterial rate against Escherichia coli and Staphylococcus aureus was nearly 100%under the simulated sunlight treatment for 30 min.Moreover,the introduction of MXene nanosheets increased the air permeability,water vapor permeability,and thermal stability of these coatings.This study provides a new insight into the preparation of novel,green,and waterborne bio-based nanocomposite coatings for leather,with desired warmth retention and antibacterial properties.It can not only realize zerocarbon heating based on sunlight in winter,reducing the use of fossil fuels and greenhouse gas emissions,but also improve ability to fight off invasion by harmful bacteria,viruses,and other microorganisms.

A Blockchain and CP-ABE Based Access Control Scheme with Fine-Grained Revocation of Attributes in Cloud Health

The Access control scheme is an effective method to protect user data privacy.The access control scheme based on blockchain and ciphertext policy attribute encryption(CP–ABE)can solve the problems of single—point of failure and lack of trust in the centralized system.However,it also brings new problems to the health information in the cloud storage environment,such as attribute leakage,low consensus efficiency,complex permission updates,and so on.This paper proposes an access control scheme with fine-grained attribute revocation,keyword search,and traceability of the attribute private key distribution process.Blockchain technology tracks the authorization of attribute private keys.The credit scoring method improves the Raft protocol in consensus efficiency.Besides,the interplanetary file system(IPFS)addresses the capacity deficit of blockchain.Under the premise of hiding policy,the research proposes a fine-grained access control method based on users,user attributes,and file structure.It optimizes the data-sharing mode.At the same time,Proxy Re-Encryption(PRE)technology is used to update the access rights.The proposed scheme proved to be secure.Comparative analysis and experimental results show that the proposed scheme has higher efficiency and more functions.It can meet the needs of medical institutions.

Molecular Dynamics Simulation of Shock Response of CL-20 Co-crystals Containing Void Defects

To investigate the effect of void defects on the shock response of hexanitrohexaazaisowurtzitane(CL-20)co-crystals,shock responses of CL-20 co-crystals with energetic materials ligands trinitrotoluene(TNT),1,3-dinitrobenzene(DNB),solvents ligands dimethyl carbonate(DMC) and gamma-butyrolactone(GBL)with void were simulated,using molecular dynamics method and reactive force field.It is found that the CL-20 co-crystals with void defects will form hot spots when impacted,significantly affecting the decomposition of molecules around the void.The degree of molecular fragmentation is relatively low under the reflection velocity of 2 km/s,and the main reactions are the formation of dimer and the shedding of nitro groups.The existence of voids reduces the safety of CL-20 co-crystals,which induced the sensitivity of energetic co-crystals CL-20/TNT and CL-20/DNB to increase more significantly.Detonation has occurred under the reflection velocity of 4 km/s,energetic co-crystals are easier to polymerize than solvent co-crystals,and are not obviously affected by voids.The results show that the energy of the wave decreases after sweeping over the void,which reduces the chemical reaction frequency downstream of the void and affects the detonation performance,especially the solvent co-crystals.

Case Report: Surgical Correction of Transposition of the Great Arteries with Aortopulmonary Window

Introduction:Transposition of the great arteries(TGA)with aortopulmonary window is a rare type of congenital heart disease with limited experience.We reported a neonate aged 25 days receiving the arterial switch operation and assisted with extracorporeal membrane oxygenation.Conclusion:TGA with aortopulmonary window can be safely correctly with the arterial switch operation.

氢家族的三胞胎

氢的同位素主要有氕、氘、氚,在科学研究和日常生活中有着重要的应用。在化学发展史上,氢元素的出现推翻了燃素说,极大促进了化学的发展。本文通过氕、氘、氚三兄弟的视角,主要介绍了其基本性质、分离方法和应用三个方面,希望能对读者深入了解氕氘氚起到一定的帮助。

Characteristics of photosynthesis and vertical canopy architecture of citrus trees under two labor-saving cultivation modes using unmanned aerial vehicle (UAV)-based LiDAR data in citrus orchards

Analyzing and comparing the effects of labor-saving cultivation modes on photosynthesis,as well as studying their vertical canopy architecture,can improve the tree structure of high-quality and high-yield citrus and selection of labor-saving cultivation modes.The photosynthesis of 1080 leaves of two labor-saving cultivation modes(wide-row and narrow-plant mode and fenced mode)comparing with the traditional mode were measured,and nitrogen content of all leaves and photosynthetic nitrogen use efficiency(PNUE)were determined.Unmanned aerial vehicle(UAV)-based light detection and ranging(LiDAR)data were used to assess the vertical architecture of three citrus cultivation modes.Results showed that for the wide-row and narrow-plant and traditional modes leaf photosynthetic CO_(2) assimilation rate,stomatal conductance,and transpiration rate of the upper layer were significantly higher than those of the middle layer,and values of the middle layer were markedly higher than those of the lower layer.In the fenced mode,a significant difference in photosynthetic factors between the upper and middle layers was not observed.A vertical canopy distribution had a more significant effect on PNUE in the traditional mode.Leaves in the fenced mode had distinct photosynthetic advantages and higher PNUE.UAV-based LiDAR data effectively revealed the differences in the vertical canopy architecture of citrus trees by enabling calculating the density and height percentile of the LiDAR point cloud.The point cloud densities of three cultivation modes were significantly different for all LiDAR density slices,especially at higher canopy heights.The labor-saving modes,particularly the fenced mode,had significantly higher height percentile data.

Effect of soaking time of dithionite-citrate-bicarbonate solution on strength and deformation characteristics of lateritic soil

This study aimed to reveal the influence of different free-iron-oxides contents on the strength and deformation characteristics of in situ lateritic soil.A test method that combined the selective chemical dissolution method and in situ Ménard pressuremeter test(PMT)was proposed.The soaking time in dithioniteecitrateebicarbonate(DCB)solution was used as a variable to control the free-iron-oxides content in lateritic soil.Then,the in situ lateritic soil boreholes with different soaking time were tested by PMT.The results showed that the in situ horizontal pressure p0,critical edge pressure pf,ultimate pressure prediction pl,pressuremeter modulus Em,shear modulus Gm,and foundation-bearing capacity f0k of lateritic soil decreased rapidly after immersing in DCB solution within 1e4 d.With increasing soaking time,the decrease rate reduced gradually.Moreover,the relationship curve between free-iron-oxides content and soaking time declined rapidly and then stabilized,and the free-iron-oxides content at the inflection point was 30.11 g/kg.When the free-iron-oxides content changed to the inflection point,the free-iron-oxides that played a cementing role was largely removed,indicating that the effective cementing iron-content of Miaoling lateritic soil was about 52.9%.This study demonstrated that the proposed test method can determine the influence of free-iron-oxides content on the strength and deformation characteristics of lateritic soil.

元素王国的“竹林七贤”——稀有气体元素

稀有气体,又称惰性气体,是一类化学性质极不活泼的元素群体。它们性质相似,在人类生活生产的各个方面都有广泛的应用。本文以拟人的手法,通过构建虚拟世界故事的方式,介绍了目前为止发现的七种稀有气体元素(竹林七贤)的含量、密度、沸点及化学反应性等物理化学性质,并穿插了一则稀有气体化合物的历史故事。与此同时以故事情节的发展为主线,讲述了稀有气体在航天离子推进器、地震预测、医学诊疗等领域的应用。

Time Domain Synchronous OFDM System for Optical Fiber Communications

A spectrum efficient OFDM scheme named Time Domain Synchronous-OFDM(TDS-OFDM)is introduced into coherent optical transmission system,in which the pseudo noise(PN)sequence is exploited as guard interval to realize frame synchronization,compensate the carrier frequency offset(CFO),and estimate and equalize channel simultaneously.Since there is no pilot signals or training symbols in TDS-OFDM,the proposed scheme can achieve higher spectral efficiency(SE)above 10%improvement comparing with CPOFDM.The proposed method is implemented and verified in a 28GBaud QPSK OFDM system and a 28GBaud 16QAM OFDM system.It is demonstrated that the proposed scheme shows high CFO estimation accuracy and synchronous accuracy.Under CFO and linewidth of laser source set as 100MHz and 100kHz respectively,BER of QPSK OFDM system is below 3.8e-3 at the optical signal-to-noise ratio(OSNR)of 13dB,and BER of 16QAM OFDM system is below 3.8e-3 at the OSNR of 20dB.

Genome sequence and evolution of Betula platyphylla

Betula L.(birch)is a pioneer hardwood tree species with ecological,economic,and evolutionary importance in the Northern Hemisphere.We sequenced the Betula platyphylla genome and assembled the sequences into 14 chromosomes.The Betula genome lacks evidence of recent whole-genome duplication and has the same paleoploidy level as Vitis vinifera and Prunus mume.Phylogenetic analysis of lignin pathway genes coupled with tissue-specific expression patterns provided clues for understanding the formation of higher ratios of syringyl to guaiacyl lignin observed in Betula species.Our transcriptome analysis of leaf tissues under a time-series cold stress experiment revealed the presence of the MEKK1–MKK2–MPK4 cascade and six additional mitogen-activated protein kinases that can be linked to a gene regulatory network involving many transcription factors and cold tolerance genes.Our genomic and transcriptome analyses provide insight into the structures,features,and evolution of the B.platyphylla genome.The chromosome-level genome and gene resources of B.platyphylla obtained in this study will facilitate the identification of important and essential genes governing important traits of trees and genetic improvement of B.platyphylla.

Short-term exposure to fine particulate matter and hospital admission for stroke:a meta-analysis

Objective Air pollution is an important risk factor for cardiovascular diseases throughout the world.Fine particulate matter(PM)air pollution alone is responsible for over three million deaths each year.Large and growing literature has explored whether short-term exposure to fine particulate matter is associated with stroke,but results from prior studies have been inconsistent.To fill this gap,we assessed the evidence quantitatively from epidemiological time-series studies published worldwide and determined whether short-term exposure to fine particulate matter(<2.5μm or<10μm)diameter[PM2.5 and PM10]was associated with increased risk of hospital admission for stroke(including ischemic and hemorrhagic stroke).

Boundary integral equations for dynamic rupture propagation on vertical complex fault system in half-space:Theory

The boundary integral equation method （BIEM） is now widely used in numerical studies on earthquake rupture dynamics, and is proved to be a powerful tool to deal with problems on complex fault system. However, since this method heavily lies on the specific forms of Green＇s function and only the Green＇s function in full-space has a closed analytic expression, it is usually limited to a full-space medium. In this study, as a first step to extend this method to an arbitrary complex fault system in half-space, the boundary integral equations （BIEs） for dynamic strike-slip on vertical complex fault system in half-space are derived based on exact Green＇s function for isotropic and homogeneous half-space. Effect of the geometry of the complex fault system are dealt with carefully. Final BIEs is composed of two parts： contribution from full-space, which has been thoroughly investigated by Aochi and his co-workers by using the Green＇s function for full-space, and that from free surface, which is studied in detail in this study.

Optimization of Extraction and Characterization of Pectin from Grapefruit Peels

In this study, pectin was extracted from grapefruit peels with hydrochloric acid and precipitated with 95% ethanol solution and 5% tartaric acid. The physical and chemical properties of pectin obtained were analyzed, including color, texture, degree of esterification, and water solubility. The effects of peel to sol- vent ratio, pH of the solvent, extraction temperature and extraction duration on pectin extraction rate were investigated. On the basis of single-factor experiments, an L9 （34） orthogonal experiment was performed to screen the optimal extraction conditions. According to the results, the optimal combination of technical parame- ters was A1B3 C1 D3, i. e. , solid to liquid ratio 1：40 （g： ml）, pH 2.0, extraction duration 70 rain, extraction temperature 90 ℃. The average pectin extraction rate was 68.60% ; the color of pectin extracted under the optimal conditions varied from milky white to light yellow; the degree of esterification of pectin extracts was 65. 71% ; the extracted pectin exhibited good water solubility. Key words Pomelo peel; Pectin extraction; Optimum conditions; Esterification degree; Water solubility

Status of Vitamin B12 Deficiency in the Elderly Chinese Community People

This study was aimed to investigate the vitamin B12 deficiency prevalence and symptoms in elderly people lived in a community of Shanghai, China. A total number of 962 elderly people resided in Shanghai community were recruited in the present study. They were 60 years and older, and the average age was 76.38 ± 13.68 years old. Information on previous and present diseases, currently prescribed and over-the-counter medication, and the presence or absence of symptoms relating to vitamin B12 deficiency were obtained by questionnaire. The levels of serum vitamin B12, folate and homocysteine (Hcy) were estimated. The patients with vitamin B12 deficiency were screened. The results of symptoms and positive signs of neurological examination were compared between subjects with or without vitamin B12 deficiency. The results showed that vitamin B12 deficiency was found in 130 persons (13.53% of the total subjects), with an increase in incidence with aging, only 10% of the vitamin B12 deficient subjects had megaloblastic anemia. The reported symptoms of vitamin B12 deficient subjects included fatigue, memory decline, dizziness, unsteadily walking in the darkness and hypopallesthesia. In conclusion, vitamin B12 deficiency was remarkably common in Chinese elderly people, with various and atypical clinical manifestations, and the neurological symptoms were more common than those of megaloblastic anemia.

An Implementation and Improvement of Convolutional Neural Networks on HSA Platform

Nowadays,the most heterogeneous architectures were made up by the various IP modules of different hardware vendors,but this model is less efficiently.In order to solve this problem,AMD joint other hardware vendors proposed heterogeneous system architecture(HSA)specification.On the one hand,the HSA could help developers to accelerate the design process and programming.On the other hand,it improved the system performance and reduced the power.In this paper we presented the implementation of a framework for accelerating training and classification of arbitrary Convolutional Neural Networks(CNNs)on the HSA,on the basis of implementation,we presented tow accelerated methods that are Online update weights and letting CPU to participate in calculation.Experimental results showed that the implementation of CNNs on HSA 4 to 10 times faster than on the CPU.

A Strategy for Small Files Processing in HDFS

Hadoop distributed file system (HDFS) as a popular cloud storage platform, benefiting from its scalable, reliable and low-cost storage capability.However it is mainly designed for batch processing of large files, it’s mean that small files cannot be efficiently handled by HDFS. In this paper, we propose a mechanism to store small files in HDFS. In our approach, file size need to be judged before uploading to HDFS. If the file size is less than the size of the block, all correlated small files will be merged into one single file and we will build index for each small file. Furthermore, prefetching and caching mechanism are used to improve the reading efficiency of small files. Meanwhile, for the new small files, we can execute appending operation on the basis of merged file. Contrasting to original HDFS, experimental results show that the storage efficiency of small files is improved.

Multi-grained Pruning Method of Convolutional Neural Network

Although the deep learning technology has shown great power in solving the complex tasks, these neural network models are large and redundant as a matter of fact, which makes these networks difficult to be placed in embedded devices with limited memory and computing resources. In order to compress the neural network to a slimmer and smaller one, the multi-grained network pruning framework is proposed in this paper. In our framework, the pruning process was divided into the filter-level pruning and the weight-level pruning. In the process of the filter-level pruning, the importance of the filter was measured by the entropy of the activation tensor of the filter. In the other process, the dynamic recoverable pruning method was adopted to prune the weights deeply. Different from these popular pruning methods, the weight-level pruning is also taken into account based on the employment of the filter-level pruning to achieve more effectively pruning. The proposed approach is validated on two representative CNN models - AlexNet and VGG16, pre-trained on ILSVRC12. Experimental results show that AlexNet and VGG16 network models are compressed 19.75- and 22.53- respectively by this approach, which are 2.05 and 5.89 higher than the classical approaches of dynamic Network Surgery and ThiNet.