Construction of core@double-shell structured energetic composites with simultaneously enhanced thermal stability and safety performance

The poor thermal stability and high sensitivity severely hinder the practical application of hexanitrohexaazaisowurtzitane(CL-20).Herein,a kind of novel core@double-shell CL-20 based energetic composites were fabricated to address the above issues.The coordination complexes which consist of natural polyphenol tannic acid(TA) and Fe~Ⅲ were chosen to construct the inner shell,while the graphene sheets were used to build the outer shell.The resulting CL-20/TA-Fe~Ⅲ/graphene composites exhibited simultaneously improved thermal stability and safety performance with only 1 wt% double-shell content,which should be ascribed to the intense physical encapsulation effect from inner shell combined with the desensitization effect of carbon nano-materials from outer shell.The phase transition(ε to γ) temperature increased from 173.70 ℃ of pure CL-20 to 191.87℃ of CL-20/TA-Fe~Ⅲ/graphene composites.Meanwhile,the characteristic drop height(H_(50)) dramatically increased from 14.7 cm of pure CL-20 to112.8 cm of CL-20/TA-Fe~Ⅲ/graphene composites,indicating much superior safety performance after the construction of the double-shell structure.In general,this work has provided an effective and versatile strategy to conquer the thermal stability and safety issues of CL-20 and contributes to the future application of high energy density energetic materials.

A review on the multi-scaled structures and mechanical/thermal properties of tool steels fabricated by laser powder bed fusion additive manufacturing

The laser powder bed fusion(LPBF) process can integrally form geometrically complex and high-performance metallic parts that have attracted much interest,especially in the molds industry.The appearance of the LPBF makes it possible to design and produce complex conformal cooling channel systems in molds.Thus,LPBF-processed tool steels have attracted more and more attention.The complex thermal history in the LPBF process makes the microstructural characteristics and properties different from those of conventional manufactured tool steels.This paper provides an overview of LPBF-processed tool steels by describing the physical phenomena,the microstructural characteristics,and the mechanical/thermal properties,including tensile properties,wear resistance,and thermal properties.The microstructural characteristics are presented through a multiscale perspective,ranging from densification,meso-structure,microstructure,substructure in grains,to nanoprecipitates.Finally,a summary of tool steels and their challenges and outlooks are introduced.

Performance evaluation of seven multi-label classification methods on real-world patent and publication datasets

Purpose:Many science,technology and innovation(STI)resources are attached with several different labels.To assign automatically the resulting labels to an interested instance,many approaches with good performance on the benchmark datasets have been proposed for multi-label classification task in the literature.Furthermore,several open-source tools implementing these approaches have also been developed.However,the characteristics of real-world multi-label patent and publication datasets are not completely in line with those of benchmark ones.Therefore,the main purpose of this paper is to evaluate comprehensively seven multi-label classification methods on real-world datasets.Research limitations:Three real-world datasets differ in the following aspects:statement,data quality,and purposes.Additionally,open-source tools designed for multi-label classification also have intrinsic differences in their approaches for data processing and feature selection,which in turn impacts the performance of a multi-label classification approach.In the near future,we will enhance experimental precision and reinforce the validity of conclusions by employing more rigorous control over variables through introducing expanded parameter settings.Practical implications:The observed Macro F1 and Micro F1 scores on real-world datasets typically fall short of those achieved on benchmark datasets,underscoring the complexity of real-world multi-label classification tasks.Approaches leveraging deep learning techniques offer promising solutions by accommodating the hierarchical relationships and interdependencies among labels.With ongoing enhancements in deep learning algorithms and large-scale models,it is expected that the efficacy of multi-label classification tasks will be significantly improved,reaching a level of practical utility in the foreseeable future.Originality/value:(1)Seven multi-label classification methods are comprehensively compared on three real-world datasets.(2)The TextCNN and TextRCNN models perform better on small-scale datasets with more complex hierarchical structure of labels and more balanced document-label distribution.(3)The MLkNN method works better on the larger-scale dataset with more unbalanced document-label distribution.

Highly Thermally Conductive and Structurally Ultra‑Stable Graphitic Films with Seamless Heterointerfaces for Extreme Thermal Management

Highly thermally conductive graphitic film(GF)materials have become a competitive solution for the thermal management of high-power electronic devices.However,their catastrophic structural failure under extreme alternating thermal/cold shock poses a significant challenge to reliability and safety.Here,we present the first investigation into the structural failure mechanism of GF during cyclic liquid nitrogen shocks(LNS),which reveals a bubbling process characterized by“permeation-diffusion-deformation”phenomenon.To overcome this long-standing structural weakness,a novel metal-nanoarmor strategy is proposed to construct a Cu-modified graphitic film(GF@Cu)with seamless heterointerface.This well-designed interface ensures superior structural stability for GF@Cu after hundreds of LNS cycles from 77 to 300 K.Moreover,GF@Cu maintains high thermal conductivity up to 1088 W m^(−1)K^(−1)with degradation of less than 5%even after 150 LNS cycles,superior to that of pure GF(50%degradation).Our work not only offers an opportunity to improve the robustness of graphitic films by the rational structural design but also facilitates the applications of thermally conductive carbon-based materials for future extreme thermal management in complex aerospace electronics.

Microearthquake reveals the lithospheric structure at midocean ridges and oceanic transform faults

Mid-ocean ridge and oceanic transforms are among the most prominent features on the seafloor surface and are crucial for understanding seafloor spreading and plate tectonic dynamics,but the deep structure of the oceanic lithosphere remains poorly understood.The large number of microearthquakes occurring along ridges and transforms provide valuable information for gaining an indepth view of the underlying detailed seismic structures,contributing to understanding geodynamic processes within the oceanic lithosphere.Previous studies have indicated that the maximum depth of microseismicity is controlled by the 600-℃isotherm.However,this perspective is being challenged due to increasing observations of deep earthquakes that far exceed this suggested isotherm along mid-ocean ridges and oceanic transform faults.Several mechanisms have been proposed to explain these deep events,and we suggest that local geodynamic processes(e.g.,magma supply,mylonite shear zone,longlived faults,hydrothermal vents,etc.)likely play a more important role than previously thought.

Functionally graded structure of a nitride-strengthened Mg_(2)Si-based hybrid composite

The ex-situ incorporation of the secondary SiC reinforcement,along with the in-situ incorporation of the tertiary and quaternary Mg_(3)N_(2) and Si_(3)N_(4) phases,in the primary matrix of Mg_(2)Si is employed in order to provide ultimate wear resistance based on the laser-irradiation-induced inclusion of N_(2) gas during laser powder bed fusion.This is substantialized based on both the thermal diffusion-and chemical reactionbased metallurgy of the Mg_(2)Si–SiC/nitride hybrid composite.This study also proposes a functional platform for systematically modulating a functionally graded structure and modeling build-direction-dependent architectonics during additive manufacturing.This strategy enables the development of a compositional gradient from the center to the edge of each melt pool of the Mg_(2)Si–SiC/nitride hybrid composite.Consequently,the coefficient of friction of the hybrid composite exhibits a 309.3%decrease to–1.67 compared to–0.54 for the conventional nonreinforced Mg_(2)Si structure,while the tensile strength exhibits a 171.3%increase to 831.5 MPa compared to 485.3 MPa for the conventional structure.This outstanding mechanical behavior is due to the(1)the complementary and synergistic reinforcement effects of the SiC and nitride compounds,each of which possesses an intrinsically high hardness,and(2)the strong adhesion of these compounds to the Mg_(2)Si matrix despite their small sizes and low concentrations.

Investigation on thermal characteristics and desensitization mechanism of improved step ladder-structured nitrocellulose

Nitrocellulose,or cellulose nitrate,has received considerable interest due to its various applications,such as propellants,coating agents and gas generators.However,its high mechanical sensitivity caused many accidents during its storage and usage in ammunition.In this work,two kinds of insensitive step ladderstructured nitrocellulose(LNC)with different nitrogen contents were synthesized.The products were characterized by FT-IR,Raman,XRD,SEM,elemental analysis,TGA,DSC,accelerating rate calorimeter analysis(ARC),and drop weight test to study their molecular structure,thermal characteristics and desensitization performance.Compared with raw nitrocellulose,LNC has a sharper exothermic peak in the DSC and ARC curves.The H50values of the two kinds of LNC increased from 25.76 to 30.01 cm for low nitrogen content and from 18.02 to 21.84 cm for high nitrogen content,respectively.The results show that the ladder-structure of LNC which provides regular molecular arrangement and a soft buffer made with polyethylene glycol could affect the energy releasing process of LNC and reduce the sensitivity of LNC.Insensitive LNC provides an alternative to be used as a binder in insensitive propellants formulation.

Deep learning based classification of rock structure of tunnel face

The automated interpretation of rock structure can improve the efficiency,accuracy,and consistency of the geological risk assessment of tunnel face.Because of the high uncertainties in the geological images as a result of different regional rock types,as well as in-situ conditions(e.g.,temperature,humidity,and construction procedure),previous automated methods have limited performance in classification of rock structure of tunnel face during construction.This paper presents a framework for classifying multiple rock structures based on the geological images of tunnel face using convolutional neural networks(CNN),namely Inception-ResNet-V2(IRV2).A prototype recognition system is implemented to classify 5 types of rock structures including mosaic,granular,layered,block,and fragmentation structures.The proposed IRV2 network is trained by over 35,000 out of 42,400 images extracted from over 150 sections of tunnel faces and tested by the remaining 7400 images.Furthermore,different hyperparameters of the CNN model are introduced to optimize the most efficient algorithm parameter.Among all the discussed models,i.e.,ResNet-50,ResNet-101,and Inception-v4,Inception-ResNet-V2 exhibits the best performance in terms of various indicators,such as precision,recall,F-score,and testing time per image.Meanwhile,the model trained by a large database can obtain the object features more comprehensively,leading to higher accuracy.Compared with the original image classification method,the sub-image method is closer to the reality considering both the accuracy and the perspective of error divergence.The experimental results reveal that the proposed method is optimal and efficient for automated classification of rock structure using the geological images of the tunnel face.

Classification Criteria of Narrow/Wide Ice-ResistantConical Structures Based on Direct Measurements

Ice-induced structural vibration generally decreases with an increase in structural width at the waterline. Definitions of wide/narrow ice-resistant conical structures, according to ice-induced vibration, are directly related to structure width, sea ice parameters, and clearing modes of broken ice. This paper proposes three clearing modes for broken ice acting on conical structures: complete clearing, temporary ice pile up, and ice pile up. In this paper, sea ice clearing modes and the formation requirements of dynamic ice force are analyzed to explore criteria determining wide/narrow ice-resistant conical structures. According to the direct measurement data of typical prototype structures, quantitative criteria of the ratio of a cone width at waterline(D) to sea ice thickness(h) is proposed. If the ratio is less than 30(narrow conical structure), broken ice is completely cleared and a dynamic ice force is produced; however, if the ratio is larger than 50(wide conical structure), the front stacking of broken ice or dynamic ice force will not occur.

Structure and Classification of Haemocytes in the Bivalve Mollusc Meretrix meretrix

光和电子显微镜的研究被执行以便在瓣鳃类软体动物 Meretrix meretrix 描绘 haemocytes。根据原子核和细胞质人物， haemocytes 的四种类型被认出：小粒的 haemocytes，淋巴的 haemocyte，大小粒、小的小粒的 haemocytes。Agranular hamocyte 是主要房间类型，为 75% 的财务。它是一与在细胞质的富有的细胞器小粒包括线粒体， golgi 身体 andendoplasmic 蜂窝胃。肝糖存款通常在这种房间类型被发现。淋巴的 haemocyte 的数字说明 1%-2% 。这种房间类型是一小粒并且显示出原子核的高比率到细胞质。一些细胞器被发现。有直径 of0.2 的高电子稠密的小粒 - 0.5 μ m 和富有的细胞器在小小粒的 haemocyte 被发现。这种房间类型的比例是大约 15% 。与 0.8 的直径电子稠密的高度的富有的小粒 - 2.4 μ m 在大小粒的 haemocyte 被发现。这种房间类型的比例是大约 10% ，并且细胞器的数量是最少。

A classification method of building structures based on multi-feature fusion of UAV remote sensing images

In order to improve the accuracy of building structure identification using remote sensing images,a building structure classification method based on multi-feature fusion of UAV remote sensing image is proposed in this paper.Three identification approaches of remote sensing images are integrated in this method:object-oriented,texture feature,and digital elevation based on DSM and DEM.So RGB threshold classification method is used to classify the identification results.The accuracy of building structure classification based on each feature and the multi-feature fusion are compared and analyzed.The results show that the building structure classification method is feasible and can accurately identify the structures in large-area remote sensing images.

Tertiary structure-based protein classification by virtual-bond-angles series

Structure-based protein classification can be based on the similarities in primary, second or tertiary structures of proteins. A method using virtual-bond-angles series that transformed the protein space configuration into a sequence was used for the classification of three-dimensional structures of proteins. By transforming the main chains formed by Cα atoms of proteins into sequences, the series of virtual-bond-angles corresponding to the tertiary structure of the proteins were constructed. Then a distance-based hierarchical clustering method similar to Ward method was introduced to classify these virtual-bond-angles series of proteins. 200 files of protein structures were selected from Brookheaven protein data bank, and 11 clusters were classified.

Source Rock Classification and the Basic Structure of Coal and Kerogen

In accordance with the confusion on classification of source rocks, the authors raised a source rock classification for its enriched and dispersed organic matter types based on both Alpern’s idea and maceral genesis/composition. The determined rock type is roughly similar to palynofacies of Combaz , whereas it is "rock maceral facies (for coal viz. coal facies)" in strictly speaking. Therefore, it is necessary to use the organic ingredients classification proposed by the authors so that it can be used for both maceral analysis and environment research . This source rock classification not only shows sedimentology and diagenetic changes but also acquires organic matter type even if hydrocarbon potential derived from maceral’s geochemical parameters. So, it is considered as genetic classification. The "rock maceral facies" may be transformed to sedimentary organic facies , which is used as quantitative evaluation means if research being perfect.Now, there are many models in terms of structure either for coal or for kerogen. In our opinion, whatever coal or kerogen ought be polymer, then we follow Combaz’s thought and study structure of amorphous kerogens which are accordance with genetic mechanism showing biochemical and geochemical process perfectly. Here, we use the time of flight secondary ion mass spectrometry (TOFSIMS) to expand Combaz’s models from three to five. They are also models for coal.

Classification of regional agricultural structure:method and its application to China

Regional agriculture is the basis of regional sustainable development,so sustainable regional agricul-tural development is essential to the sustainable development of the whole society and becomes the focus of global research.The classifi cation of regional agricultural structure is the basic work of regional agriculture study.This paper constructs index system(27 indices) of regional agricultural structure types with the three big indices:natural resources,developmental level of the agro-economy,and agro-ecological conditions.This paper also endows weight to every sub-classif ication index by means of AHP and obtains the comprehensive evaluation value of the three types of indices with arithmetic average weight approach.The regional agricultural structure can be classif ied into eight types in accordance with this evaluation results.The empirical study of China shows that the 31 provinces(munici-palities and autonomous regions) are of different agriculture structural types.Finally,countermeasures of sustain-able agricultural development are put forward for the different agriculture structure features.

Meso-Cenozoic lithospheric thermal structure in the Bohai Bay Basin,eastern North China Craton

The Bohai Bay Basin is a region where part of the North China Craton has been thinned and destroyed. It has experienced two periods of crustal thinning that occurred during the Cretaceous and Paleogene, but investigations of its Mesozoic and Cenozoic lithospheric thermal structure are limited. Therefore, in this study,the distributions of mantle heat flow, crustal heat flow, and Moho temperatures during the Meso-Cenozoic are calculated based on analyses of the thermal history of the Bohai Bay Basin. The results indicate that the ratio of mantle heat flow to surface heat flow peaked during the late stages of the early Cretaceous and during the middle to late Paleogene. The corresponding mantle heat flow was more than 65% of the surface heat flow. Moho temperatures reached three peaks: 900-1100℃ in the late stages of the early Cretaceous;820-900℃ in the middle to late Paleogene; and(in the Linqing Depression, Cangxian Uplift, and Jizhong Depression) 770-810℃ during the early Neogene. These results reveal that the Bohai Bay Basin experienced significant geological change during the Cretaceous, including the transformation of lithospheric thermal structure from "cold mantle and hot crust" before the Cretaceous to "hot mantle and cold crust" after the Cretaceous. The results also indicate that the basin experienced two large-scale rifting events.Therefore, this work may provide the thermal parameters for further investigations of the geodynamic evolution of eastern China.

Syntheses,Crystal Structures and Kinetic Mechanisms of Thermal Decomposition of Rare Earth Complexes with Schiff Base Derived from o-Vanillin and p-Toluidine

Three complexes, [Pr（NO3）3（HL）2] （1）, [Nd（NO3）3（HL）2] （2） and [Er（NO3）3（HL）2] ·0.5H2O （3）, were synthesized from the reaction of a Schiff base ligand 2-[ （4-methylphenylimino）methyl ]-6-methoxyphenol （C15 H15 NO2, HL） with Ln（NO3）3·6H2O （Ln = Pr, Nd, Er）. Characterization by single-crystal X-ray diffraction technique, elemental analysis, molar conductance, FT-IR, UV-Vis, ^1H NMR and thermal analysis shows the title complexes are neutral molecules where the central Ln（ Ⅲ） ion is ten-coordinated in biapical anti-hexahedron prism geometry, with four oxygen atoms of the phenolic hydroxy and methoxy groups in the two bidentate Schiff base ligands and six oxygen atoms provided by the three bidentate NO3 - anions. Additionally, the kinetic mechanism of thermal decomposition of complex 3 was determined with a TG-DTG curves by both integral and differential methods. The functions of thermal decomposition reaction mechanism and the equation of kinetic compensation effect were obtained.

Structure and Thermal Properties of Transition Metal Imidazole Chloride

The X-ray single-crystal structure analyses have been determined for two metal imidazole chlorides: [Fe(Im)6]Cl24H2O 1 and [CuCl(Im)4]Cl 2 (Im = imidazole). The red crystal of compound 1 is of triclinic, space group Pi with Mr = 607.31 (C18H32Cl2FeN12O4), a = 8.797(2), b = 9.068(2), c = 10.581(2) ? a = 75.35(3), ?= 83.20(3), ? = 61.85(3)o, V = 720.0(2) 3, Z = 1, Dc = 1.401 g/cm3, F(000) = 316, = 0.755 mm-1, R = 0.0353 and wR = 0.1227. The blue crystal of compound 2 belongs to monoclinic, space group P21/c with Mr = 406.77 (C12H16Cl2CuN8), a = 13.909(3), b = 8.8933(18), c = 15.086(7) ? ?= 118.32(2), V = 1642.7(9) 3, Z = 4, Dc = 1.645 g/cm3, F(000) = 828, = 1.666 mm-1, R = 0.0609 and wR = 0.1726. In solid state, both 1 and 2 form three-dimensional hydrogen bond networks to stabilize the structures which were also characterized by TG and elemental analyses. The thermal gravity (TG) data indicate that the residues are Fe and Cu for 1 and 2, respectively.

Hydrothermal Synthesis and Crystal Structure of a New Three-dimensional Heterometallic Coordination Polymer

A new 3d-4fheterometallic polymer {[Sm2Cu（PDC）2（SO4）2（H20）6]·2H2O}n 1 has been synthesized by Sm2O3, Cu（SO4）2·5H2O and pyridine-3,5-dicarboxylic acid under hydrothermal conditions. The compound crystallizes in triclinic system, space group Pi, with a = 6.352（7）, b = 10.040（10）, c = 10.315（11） A, α = 94.958（14）, β = 95.556（7）, γ = 99.747（14）°, V = 641.7（12）A3, Z = 1, M, = 1030.63, Dc= 2.651 Mg/m3,μ = 5.615 mm-1, F（000） = 491, the final R = 0.0491 and wR = 0.1345 for 2098 observed reflections with I 〉 2σ（I）. The compound is a three-dimensional network structure in which infinite lanthanide-carboxylate chains are linked by [Cu（$04）2]2- metalloligands to form a mixed-metal coordination network.

Hydrothermal Synthesis,Crystal Structure and Thermal Stability of a Binuclear Copper(Ⅱ) Complex with 3-(Pyridin-2-yl)-1,2,4-triazole

One novel binuclear copper（Ⅱ） complex [Cu 2 （Hpt） 2 （CO 3） 2 （H 2 O） 2 ]·H 2 O with copper carbonate and 3-（pyridin-2-yl）-1,2,4-triazole （Hpt） was hydrothermally synthesized and characterized by IR and X-ray diffraction analysis.The complex crystallizes in triclinic,space group P2 1 /n with a=0.6862（1）,b=0.7805（1）,c=1.1983（2） nm,α=72.03（2）,β=107.72（3）,γ=75.28（2）o,V=0.5884 nm 3,D c=2.105 g/cm 3,Z=1,F（000）=357,GOOF=1.041,the final R=0.01859 and wR=0.04348.The whole molecule is composed of two cooper ions,two Hpt molecules,two carbonate and three water molecules,forming a binuclear structure.The crystal structure shows that the cooper ion is coordinated with three nitrogen atoms from two Hpt molecules,two oxygen atoms from one carbonic acid and one water molecule,forming a distorted square pyramidal geometry.The TG analysis result shows that the title complex is stable under 131.0 ℃.

Synthesis,Crystal Structure and Thermal Decomposition of a New Energetic Potassium Salt of Bis(dinitromethyl)difurazanyl Ether

A new energetic organic potassium salt bis（dinitromethyl）difurazanyl ether potas- sium salt [K2（BDFE）] was synthesized, and structurally characterized by elemental analysis, IR spectra, t3C NMR and single-crystal X-ray diffraction. K2（BDFE） crystallizes in monoclinic system, space group C2/c with a = 17.342（3）, b = 12.6943（17）, c = 8.0972（11） A, β = 110.630（2）°, V = 1668.3（4） A3, Z = 4, Dc = 2.000 g/cm3, F（000） = 1000,μ= 0.675 mm-1, S = 1.058, the final R = 0.0499 and wR = 0.1452. The K ion is eight-coordinated with eight O atoms from one water molecule and four bis（dinitromethyl）difurazanyl ethers （BDFE）, forming a distorted dodecahedral structure. Thermal decomposition of the title complex was studied by using DSC and TG-DTG. There are primarily two exothermic decomposition processes between 200 and 370 ℃.