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A judicious approach to induce large size growth of hydroxyapatite via applying graphene modified silicon nitride nanowires

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Journal of Materiomics 2024年第2期10卷 490-498页

作者： Lina Sun Leilei Zhang Ruonan Zhang Hejun Li state key laboratory of Solidification Processing Shanxi Key Laboratory of Fiber Reinforced Light Composite MaterialsNorthwestern Polytechnical UniversityXi'an710072China

Mimicking the structure of natural bone collagen fibers/hydroxyapatite(HA)to synthesize large size of HA for accelerated bone repair remains a ***,silicon nitride nanowires(SN)-graphene(GE)was designed by the chemical vapor deposition,forming SN-GE(SG)similar to collagen ***,the large size HA was assembled onto SG by pulsed electrochemical deposition,the SG/HA(SGH)mimics the collagen fibers/HA structure of *** introduction of SG induces HA to large size grow in the form of *** can be grown on a large size inextricably with the existence of GE modified *** the one hand,the upright GE sheets effectively increases the surface roughness which enhances the nucleation site of *** the other hand,the C■O provides chemical bonding and induces HA *** with SN/HA(SH),the porosity of SGH decreased by 71%.The average diameter of the SGH is(9.76±0.25)*** with SH,the diameter of SGH is 22 times larger than the diameter of *** that SG induces large size growth of *** work can provide a general strategy for the efficient preparation of biological scaffolds with large size HA that can be used in bone tissue engineering.

关键词： Hydroxyapatite Graphene Large size Silicon nitride nanowires Bone tissue engineering

Highly selective photocatalytic reduction of CO_(2) to CH_(4) on electron-rich Fe species cocatalyst under visible light irradiation

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Carbon Energy 2024年第1期6卷 255-266页

作者： Qianying Lin Jiwu Zhao Pu Zhang Shuo Wang Ying Wang Zizhong Zhang Na Wen Zhengxin Ding Rusheng Yuan Xuxu Wang Jinlin Long state key laboratory of Photocatalysis on Energy and Environment College of ChemistryFuzhou UniversityFuzhouChina

Efficient photocatalytic reduction of CO_(2) to high-calorific-value CH4,an ideal target product,is a blueprint for C_(1)industry relevance and carbon neutrality,but it also faces great ***,we demonstrate unprecedented hybrid SiC photocatalysts modified by Fe-based cocatalyst,which are prepared via a facile impregnation-reduction method,featuring an optimized local electronic *** exhibits a superior photocatalytic carbon-based products yield of 30.0μmol g^(−1) h^(−1) and achieves a record CH_(4) selectivity of up to 94.3%,which highlights the effectiveness of electron-rich Fe cocatalyst for boosting photocatalytic performance and ***,the synergistic effects of directional migration of photogenerated electrons and strongπ-back bonding on low-valence Fe effectively strengthen the adsorption and activation of reactants and intermediates in the CO_(2)→CH_(4) *** study inspires an effective strategy for enhancing the multielectron reduction capacity of semiconductor photocatalysts with low-cost Fe instead of noble metals as cocatalysts.

关键词： artificial synthesis of CH_(4) electronic structure optimization Fe species cocatalyst photocatalytic CO_(2) reduction SiC

Mesoscale Mechanical Properties and Influencing Factors of Concrete under Uniaxial Tension

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Journal of Wuhan University of Technology(Materials Science) 2024年第5期39卷 1156-1168页

作者： CHEN Tao LI Kungang XIAO Shiyun state key laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian 116024China

Monte Carlo simulations were carried out to generate a mesoscale model of concrete with randomly packed aggregates with different shapes and *** mechanical properties of concrete specimens under uniaxial tensile loads were studied using statistical *** results indicated that the entire process of damage and failure of specimens exhibited mainly two failure types:fracture patternsⅠandⅡ.Furthermore,the influences of the aggregate content ratio,aggregate shape,aggregate size,interfacial transition zone(ITZ)strength,and porosity ratio on the concrete specimens were *** numerical simulation results showed that the elastic modulus of the concrete specimens increased approximately linearly with the aggregate volume ratio but decreased linearly with the porosity and was not affected by the ITZ *** tensile strength decreased with the increases in the aggregate content and porosity of the sample,but increased linearly with the ITZ *** addition,the aggregate shape led to a difference in the tensile strength of the concrete.

关键词： concrete mechanical behavior aggregate interfacial transition zone pore

Mitigate noisy data for smart IoT via GAN based machine unlearning

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Science China(Information Sciences) 2024年第3期67卷 62-78页

作者： Zhuo MA Yilong YANG Yang LIU Xinjing LIU Jianfeng MA School of Cyber Engineering Xidian University state key laboratory of Integrated Services Networks (ISN)

With the development of IoT applications, machine learning dramatically improves the utility of variable IoT systems such as autonomous driving. Although the pretrain-finetune framework can cope well with data heterogeneity in complex IoT scenarios, the data collected by sensors often contain unexpected noisy data, e.g., out-of-distribution(OOD) data, which leads to the reduced performance of fine-tuned models. To resolve the problem, this paper proposes Mu GAN, a method that can mitigate the side-effect of OOD data via the generative adversarial network(GAN)-based machine unlearning. Mu GAN follows a straightforward but effective idea to mitigate the performance loss caused by OOD data, i.e., “flashbacking” the model to the condition where OOD data are excluded from model training. To achieve the goal, we design an adversarial game, where a discriminator is trained to identify whether a sample belongs to the training set by observing the confidence score. Meanwhile, a generator(i.e., the target model) is updated to fool the discriminator into believing that the OOD data are not included in the training set but others do. The experimental results show that benefiting from the high unlearning rate(more than 90%) and retention rate(99%), Mu GAN succeeds in lowering the model performance degradation caused by OOD data from 5.88% to 0.8%.

关键词： machine unlearning generative adversarial network out of distribution data Internet of Thing neural network

Tiered clustering-based management architecture in mega-satellite networks

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Science China(Information Sciences) 2024年第5期67卷 215-227页

作者： Qi HAO Di ZHOU Min SHENG Yan SHI Jiandong LI state key laboratory of Integrated Service Networks Xidian University

Hybrid orbital networking and the proliferation of satellites raise explosive management complexity in mega-satellite networks(MSNs) and prompt the management architecture to the hierarchy. In this regard, we propose a tiered clustering-based management architecture(TCMA) to realize the high-efficient and low-cost management performance. Specifically, based on the constrained satellite coverage, we derive an expression of the mapping relationship between the required control overhead of the controller interaction,the average path length of the proposed TCMA, and the corresponding number of management tiers and cluster size. The expression can determine the optimal number of tiers of the TCMA by minimizing the required flow table size between controllers, while ensuring high transmission efficiency. We then exhibit the elasticity of the hierarchical TCMA by adding the peer connections at the second-highest management tier to reduce maximum redundant paths. Simulation results verify the effectiveness of the proposed TCMA and illustrate that a 3-tier TCMA is sufficient for thousands of satellites.

关键词： mega-satellite networks hierarchical architecture average hop tiered structure clustering

Low-noise compact fiber laser based on nonlinear polarization evolution in an all-polarization-maintaining figure-8 cavity

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Chinese Optics Letters 2024年第7期22卷 47-52页

作者： Lian Zhou Daping Luo Gehui Xie Shiping Xiong Haipeng Lou Zilin Zhao Yuanfeng Di Chenglin Gu Wenxue Li state key laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200062China

We demonstrate an all-polarization-maintaining(APM)fiber mode-locked laser based on nonlinear polarization evolution(NPE).A well-designed Sagnac fiber loop is employed to establish the nonlinear polarization evolution process in a polarization beam splitter(PBS)figure-8 fiber *** loss curves are calculated to verify the saturable absorption characteristic of this NPE-based APM ***,we simulate the pulse propagation process in the cavity to demonstrate the pulse mode-locked ***,we also design a realizable compact scheme to further reduce noise disturbances,achieving a 101-fs mode-locked pulse train with a 0.3-mrad integrated phase noise and a 0.006%integrated relative intensity noise(RIN).This figure-8 fiber laser provides a new scheme for compacting low-noise compact APM fiber lasers based on the NPE mode-locked mechanism.

关键词： ultrafast laser fiber laser polarization-maintaining.

Effect of Sodium Tripolyphosphate and Silica Fume on Hydration of High Alumina Cement

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Journal of Wuhan University of Technology(Materials Science) 2024年第5期39卷 1246-1252页

作者： WANG Jingran YANG Zongyuan ZHANG Shuai ZHANG Jinhua HAN Bingqiang KE Changming The state key laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081China

It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the conversion of CAH_(10)to C_(3)AH_(6).Sodium tripolyphosphate can retard the early hydration of cement,have a slight effect on 1 d hydration products of cement and inhibit the generation hydration *** tripolyphosphate and silica fume can promote the early hydration of cement,advance the formation of C_(2)ASH_(8)or the conversion from CAH_(10)to C_(3)AH_(6)at 1 d.

关键词： high aluminum cement silica fume dispersing agent hydration

Propagation Properties of Shock Waves in Polyurethane Foam based on Atomistic Simulations

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Defence Technology（防务技术） 2024年第1期31卷 117-129页

作者： Zhiqiang Hu Jianli Shao Shiyu Jia Weidong Song Cheng Wang state key laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

Porous materials are widely used in the field of protection because of their excellent energy absorption *** this work,a series of polyurethane microscopic models are established and the effect of porosity on the shock waves is studied with classical molecular dynamics ***,shock Hugoniot relations for different porosities are obtained,which compare well with the experimental *** pores collapse and form local stress wave,which results in the complex multi-wave structure of the shock *** microstructure analysis shows that the local stress increases and the local velocity decreases gradually during the process of pore collapse to complete ***,it leads to stress relaxation and velocity *** shock stress peaks can be fitted with two exponential functions,and the amplitude of attenuation coefficient decreases with the increase of ***,the pore collapse under shock or non-shock are discussed by the entropy increase rate of the *** energy is dissipated mainly through the multiple interactions of the waves under *** energy is dissipated mainly by the friction between atoms under non-shock.

关键词： Polyurethane foam Shock wave Attenuation Atomistic simulation

Shock-induced chemical reaction characteristics of PTFE-Al-Bi_(2)O_(3)reactive materials

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Defence Technology（防务技术） 2024年第6期36卷 1-12页

作者： Chunlan Jiang Rong Hu Jingbo Zhang Zaicheng Wang Liang Mao state key laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China

A ternary system of PTFE/Al/Bi_(2)O_(3)is constructed by incorporating PTFE-based reactive material and thermite for enhancing the energy release of the PTFE-based reactive *** effects of Bi_(2)O_(3)in the PTFE/Al/Bi_(2)O_(3)on both mechanical properties and the energy release were investigated through various tests such as thermogravimetry-differential scanning calorimetry,adiabatic oxygen bomb test and split Hopkinson pressure bar *** microstructure observed through scanning electron microscope and Xray diffraction results are used to analyze the ignition and reaction mechanism of PTFE/Al/Bi_(2)O_(3).The results indicate that the PTFE/Al/Bi_(2)O_(3)are capable of triggering the exothermic reaction of molten PTFE/Bi_(2)O_(3)and Al/Bi_(2)O_(3)over the PTFE/Al reactive materials,thereby promoting *** excessive aluminum in the ternary system is beneficial for increasing energy *** ignition of shock-induced chemical reactions in PTFE/Al/Bi_(2)O_(3)is closely related to the material *** dominant mechanism for hot-spot generation under Split Hopkinson Pressure Bar test is the frictional temperature rise at the microcrack after failure.

关键词： PTFE/Al/Bi_(2)O_(3) Shock-induced chemical reaction Energy release