Selection and modification of ground motion records using Newmark-Hall spectrum as target spectrum for long-period structures

Input ground motions have significant impacts on the uncertainty of structural responses in time-history analysis.In this study,records were selected and scaled for the evaluation of mean structural responses according to the target spectrum.The Newmark-Hall spectrum is closely related to seismic response of short,medium and long-period structures,so it was taken as the target spectrum here.The nonlinear time-history analyses of 9-story and 20-story steel moment-resisting frame structures were carried out as examples.They represent medium and long-period buildings,respectively.Three target spectra with risk of 50%,10%and 2%probabilities for exceedance in 50 years were calculated by the average Newmark-Hall spectrum method for three ground motion sets developed in the SAC Steel Project.The predicted structural mean responses of these Newmark-Hall spectra were compared with those calculated by the average spectral acceleration method for the same record set.It is found that both methods have similar accuracy for estimating the structural mean response.However,the method proposed herein is more effective in reducing the variability of the structural responses.Also,the proposed method is more advantageous for the time-history analysis of long-period structures or structures with more severe nonlinear responses under strong seismic excitations.

Microstructure,Properties,and Grain Growth Kinetics of Mo-5Ta Refractory Sputtering Targets Prepared by SPS

Mo-5Ta targets were prepared by the spark plasma sintering(SPS)technology under the sintering temperatures of 1400-1600℃,the holding times of 0-20 min,and the axial pressure of 30 MPa.The microstructure,performance,and grain growth kinetics of Mo-5Ta sputtering targets were studied.With the increase of sintering temperatures and times,Ta can more dissolve in Mo and form a Mo(Ta)solid solution.The grain sizes of Mo-5Ta targets remain unchanged at low temperatures(1400-1500℃)while increasing significantly at high temperature(1600℃)with the extension of the holding time.In addition,the densities and Vickers hardness(HV_(0.5))first ascend and then decrease with sintering proceeding.The thermal conductivity is positively correlated with the grain size and density,as a result of their joint action.Based on the comprehensive analysis,the grain growth is dominated by the combination of boundary diffusion and volume diffusion.When n=2,the activation energies of grain growth under holding times of 5,10,20 min are calculated as 762.70,617.86,and 616.52 kJ/mol,respectively.

Variable structure guidance law for attacking surface maneuver targets

The characteristics of surface maneuver targets are analyzed and a 3-D relative motion model for missiles and targets is established. A variable structure guidance law is designed considering the characteristics of targets. In the guidance law, the distance between missiles and targets as well as the missile-target relative velocity are all substituted by estimation values. The estimation errors, the target＇s velocity, and the maneuver acceleration are all treated as bounded disturbance. The guidance law proposed can be implemented conveniently in engineering with little target information. The performance of the guidance system is analyzed theoretically and the numerical simulation result shows the effectiveness of the guidance law.

Impacts of species depletion on the food web structure of a marine ecosystem based on topological network analysis

Single-species management ignores the interactions between species,and ecosystem-based fisheries management(EBFM)has become a main method to fisheries management.Understanding food web structures and species interactions is essential for the implementation of EBFM and maintenance of ecosystem functions.Overfishing is one of the main reasons behind the depletion,which could even lead to the depletion of some target species in local areas.So understanding the impacts of species depletion on food web structures is important for the implementation of EBFM.The impacts of species depletion can be transmitted through the food web and cause the local extinction of both target and non-target species.In this study,topological network analysis was applied to examine the impacts of species depletion on the food web structure of Haizhou Bay.Results showed that fine crayfish Leptochela gracilis,squid Loligo sp.,and Japanese snapping shrimp Alpheus japonicus have the highest numbers of outgoing links(48,32 and 31 respectively);thus,these species may be considered key prey species.Whitespotted conger Conger myriaster,fat greenling Hexagrammos otakii,and bluefin gurnard Chelidonichthys kumu were key predators with the highest number of incoming links(37,36 and 35 respectively).The competition graphs derived from the Haizhou Bay food web were highly connected(more than 40%predators sharing over 10 common prey species),and showed close trophic interaction between high trophic level fishes.Simulation analysis showed that the food web structure has small changes to the depletion of species in a highly complex food web.The most-connected target species did not necessarily indicate high structural importance;however,some species with low connectivity may demonstrate stronger trophic interactions and play important ecological roles in the food web.But most species were more sensitive to the depletion of the most-connected target species than other target species(for instance,for zooplankton,closeness centrality 13.876 in D6,but closeness centrality 82.143 in original food web).Therefore,EBFM should focus on the most-connected target species,but also on those species with few but strong links and feeding relationships in the food web.

Study on liquid-filled structure target with shaped charge vertical penetration

Based on the characteristic expanded hole of a shaped charge jet(SCJ) for target penetration and the reflow characteristics of liquids,the liquid-filled structure of a target disturbs the stability of the SCJ acquired in two independent parts.The interference jet speed interval,the escape jet speed interval,and the surplus depth are calculated on the basis of the virtual origin theory.The experimental results,including the velocity of the escaped jet tip and the surplus depth of penetration,are consistent with the theoretical results.Experiments show that the theory can describe the interaction process of the target with a shaped charge jet.

Identification of the sensitive area for targeted observation to improve vertical thermal structure prediction in summer in the Yellow Sea

The sensitive area of targeted observations for short-term(7 d)prediction of vertical thermal structure(VTS)in summer in the Yellow Sea was investigated.We applied the Conditional Nonlinear Optimal Perturbation(CNOP)method and an adjoint-free algorithm with the Regional Ocean Modeling System(ROMS).We used vertical integration of CNOP-type temperature errors to locate the sensitive areas,where reduction of initial errors is expected to yield the greatest improvement in VTS prediction for the selected verification area.The identified sensitive areas were northeast−southwest orientated northeast to the verification area,which were possibly related to the southwestward background currents.Then,we performed a series of sensitivity experiments to evaluate the effectiveness of the identified sensitive areas.Results show that initial errors in the identified sensitive areas had the greatest negative effect on VTS prediction in the verification area compared to errors in other areas(e.g.,the verification area and areas to its east and northeast).Moreover,removal of initial errors through deploying simulated observations in the identified sensitive areas led to more refined prediction than correction of initial conditions in the verification area itself.Our results suggest that implementation of targeted observation in the CNOP-based sensitive areas is an effective method to improve short-term prediction of VTS in summer in the Yellow Sea.

Persymmetric adaptive polarimetric detection of subspace range-spread targets in compound Gaussian sea clutter

This paper focuses on the adaptive detection of range and Doppler dual-spread targets in non-homogeneous and nonGaussian sea clutter.The sea clutter from two polarimetric channels is modeled as a compound-Gaussian model with different parameters,and the target is modeled as a subspace rangespread target model.The persymmetric structure is used to model the clutter covariance matrix,in order to reduce the reliance on secondary data of the designed detectors.Three adaptive polarimetric persymmetric detectors are designed based on the generalized likelihood ratio test(GLRT),Rao test,and Wald test.All the proposed detectors have constant falsealarm rate property with respect to the clutter texture,the speckle covariance matrix.Experimental results on simulated and measured data show that three adaptive detectors outperform the competitors in different clutter environments,and the proposed GLRT detector has the best detection performance under different parameters.

Resolving impact volatilization and condensation from target rock mixing and hydrothermal overprinting within the Chicxulub impact structure

This work presents isotopic data for the non-traditional isotope systems Fe,Cu,and Zn on a set of Chicxulub impactites and target lithologies with the aim of better documenting the dynamic processes taking place during hypervelocity impact events,as well as those affecting impact structures during the post-impact phase.The focus lies on material from the recent IODP-ICDP Expedition 364 Hole M0077A drill core obtained from the offshore Chicxulub peak ring.Two ejecta blanket samples from the UNAM 5 and 7 cores were used to compare the crater lithologies with those outside of the impact structure.The datasets of bulk Fe,Cu,and Zn isotope ratios are coupled with petrographic observations and bulk major and trace element compositions to disentangle equilibrium isotope fractionation effects from kinetic processes.The observed Fe and Cu isotopic signatures,with δ^(56/54)Fe ranging from0.95‰to 0.58‰and δ^(65/63)Cu from0.73‰to 0.14‰,mostly reflect felsic,mafic,and carbonate target lithology mixing and secondary sulfide mineral formation,the latter associated to the extensive and long-lived(>105 years)hydrothermal system within Chicxulub structure.On the other hand,the stable Zn isotope ratios provide evidence for volatility-governed isotopic fractionation.The heavier Zn isotopic compositions observed for the uppermost part of the impactite sequence and a metamorphic clast(δ^(66/64)Zn of up to 0.80‰and 0.87‰,respectively)relative to most basement lithologies and impact melt rock units indicate partial vaporization of Zn,comparable to what has been observed for Cretaceous-Paleogene boundary layer sediments around the world,as well as for tektites from various strewn fields.In contrast to previous work,our data indicate that an isotopically light Zn reservoir(δ^(66/64)Zn down to0.49‰),of which the existence has previously been suggested based on mass balance considerations,may reside within the upper impact melt rock(UIM)unit.This observation is restricted to a few UIM samples only and cannot be extended to other target or impact melt rock units.Light isotopic signatures of moderately volatile elements in tektites and microtektites have previously been linked to(back-)condensation under distinct kinetic regimes.Although some of the signatures observed may have been partially overprinted during post-impact processes,our bulk data confirm impact volatilization and condensation of Zn,which may be even more pronounced at the microscale,with variable degrees of mixing between isotopically distinct reservoirs,not only at proximal to distal ejecta sites,but also within the lithologies associated with the Chicxulub impact crater.

Design of foundation structures of sea-crossing bridges on serviceability limit state

The target reliability indices of the foundation structures of sea-crossing bridges on the serviceability limit state （SLS） are different from those of common bridges due to their different surroundings. Consequently, three levels of the target reliability indices, which are 1.5, 2. 0 and 2. 3, respectively, for those structures on the SLS are suggested based on the Joint Committee on Structural Safety （JCSS） model code, and a new method of calibrating factors of live loads, which is based on the contribution ratio of tensile stresses of reinforcing bars produced by various loads to the maximum crack width of concrete, is proposed. Finally, the calibration of the reliability-based factors of the frequent value and the quasi-permanent value of live loads is conducted by the Joint Committee （JC） method through an actual design, and the indices are proved to be reasonable and the new method is proved to be feasible.

Data-Driven Design for Targeted Regulation of Heat Transfer in Carbon/Carbon Composite Structure

Targeted regulation of heat transfer in carbon/carbon composite structure is built for cooling electronic device.A three-dimensional data-driven design model coupling genetic algorithm(GA) with self-adaption deep learning for targeted regulation of heat transfer in built structure is proposed.The self-adaption deep learning model predicts the temperature of built structure closer to optimal value in GA model.The distributions of pore and carbon fiber bundles in built structure are optimized by the proposed model.The surface temperature of electronic device in the optimized structures is 19.1%-27.5% lower than that in the initial configurations when the porosity of built structure varies from 3% to 11%.The surface temperature of electronic device increases with an increase in porosity.The built structure with carbon fiber bundles near the surface of electronic device and pore distribution in the middle of structure has a higher heat dissipation capacity compared with that in the initial configuration.Besides,the computation time of the proposed model is less than one tenth compared with that of the traditional genetic algorithm.

Effect of the structure of ginsenosides on the in vivo fate of their liposomes

To utilize themultiple functions and give full play of ginsenosides,a variety of ginsenosides with different structures were prepared into liposomes and evaluated for their effect on the stability,pharmacokinetics and tumor targeting capability of liposomes.The results showed that the position and number of glycosyl groups of ginsenosides have significant effect on the in vitro and in vivo properties of their liposomes.The pharmacokinetics of ginsenosides liposomes indicated that the C-3 sugar group of ginsenosides is beneficial to their liposomes for longer circulation in vivo.The C-3 and C-6 glycosyls can enhance the uptake of their liposomes by 4T1 cells,and the glycosyls at C-3 position can enhance the tumor active targeting ability significantly,based on the specific binding capacity to Glut 1 expressed on the surface of 4T1 cells.According to the results in the study,ginsenoside Rg3 and ginsenoside Rh2 are potential for exploiting novel liposomes because of their cholesterol substitution,long blood circulation and tumor targeting capabilities.The results provide a theoretical basis for further development of ginsenoside based liposome delivery systems.

Investigation of system structure and information processing mechanism for cognitive skywave over-the-horizon radar

Based on the cognitive radar concept and the basic connotation of cognitive skywave over-the-horizon radar（SWOTHR）, the system structure and information processingmechanism about cognitive SWOTHR are researched. Amongthem, the hybrid network system architecture which is thedistributed configuration combining with the centralized cognition and its soft/hardware framework with the sense-detectionintegration are proposed, and the information processing framebased on the lens principle and its information processing flowwith receive-transmit joint adaption are designed, which buildand parse the work law for cognition and its self feedback adjustment with the lens focus model and five stages informationprocessing sequence. After that, the system simulation andthe performance analysis and comparison are provided, whichinitially proves the rationality and advantages of the proposedideas. Finally, four important development ideas of futureSWOTHR toward ＂high frequency intelligence information processing system＂ are discussed, which are scene information fusion, dynamic reconfigurable system, hierarchical and modulardesign, and sustainable development. Then the conclusion thatthe cognitive SWOTHR can cause the performance improvement is gotten.

Calibration of line structured light vision system based on camera’s projective center

Based on the characteristics of line structured light sensor, a speedy method for the calibration was established. With the coplanar reference target, the spacial pose between camera and optical plane can be calibrated by using of the camera’s projective center and the light’s information in the camera’s image surface. Without striction to the movement of the coplanar reference target and assistant adjustment equipment, this calibration method can be implemented. This method has been used and decreased the cost of calibration equipment, simplified the calibration procedure, improved calibration efficiency. Using experiment, the sensor can attain relative accuracy about 0.5%, which indicates the rationality and effectivity of this method.

Effect of Ti layer thickness on microstructure and magnetic properties of Ti/Co/Ti films

TiCoTi granular films were prepared by DC facing-target magnetron sputtering system onto glass substrates and subsequently in situ annealing in vacuum. Structural of Ti (t nm)/Co (40 nm)/Ti (t nm) films were investigated in detail, which shows that the majority Co nanograins are formed as the hexagonal-close-packed (HCP) structure. Vibrating sample magnetometer (VSM) and scanning probe microscope (SPM) were applied to study the magnetic properties, morphologies and domain structures of these samples. It has been found that the structure and magnetic properties of the Ti/Co/Ti films depend strongly on the Ti layer thickness. The out-of-plane coercivities (Hc) of the film is maximum about 78.8 kA·m-1 when t=5 nm with annealing at 300 ℃; the distributing of grains of the sample is uniformity; and the average size of particles is about 13 nm. The obtained results suggest that this system is perpendicular anisotropy and might be applicable to perpendicular magnetic recording media.

Efficient tracker based on sparse coding with Euclidean local structure-based constraint

Abstract:Sparse coding(SC)based visual tracking(l1-tracker)is gaining increasing attention,and many related algorithms are developed.In these algorithms,each candidate region is sparsely represented as a set of target templates.However,the structure connecting these candidate regions is usually ignored.Lu proposed an NLSSC-tracker with non-local self-similarity sparse coding to address this issue,which has a high computational cost.In this study,we propose an Euclidean local-structure constraint based sparse coding tracker with a smoothed Euclidean local structure.With this tracker,the optimization procedure is transformed to a small-scale l1-optimization problem,significantly reducing the computational cost.Extensive experimental results on visual tracking demonstrate the eectiveness and efficiency of the proposed algorithm.

科技服务业试点对城市绿色全要素生产率的影响研究

科技服务业试点对于推动绿色全要素生产率的提高具有重要作用。通过利用2005—2021年292个地级市的面板数据,使用双重差分法、中介模型研究科技服务业试点对中国绿色全要素生产率的影响。研究发现,科技服务业试点能提升中国绿色全要素生产率;人均消费支出在科技服务业试点与绿色全要素生产率之间发挥中介作用;科技服务业试点可以通过促进产业结构高级化间接提升绿色全要素生产率。因此,应进一步发挥人均消费支出对绿色全要素生产率的促进作用,促进企业加快技术创新,科技服务业试点政策要支持新兴产业快速发展。

油松人工林土壤微生物对结构调整的响应研究

[目的]为评估结构调整对油松人工林生态系统的影响,探索土壤微生物群落结构动态对结构调整干扰的响应机制。[方法]利用高通量测序技术,对结构调整后山西省中条山油松人工林林下土壤微生物的类群组成及多样性进行探究,分析土壤微生物群落的组成结构、多样性及其与环境因素的相互关系。[结果]油松人工林结构调整能够降低土壤的pH值,土壤养分含量显著低于对照样地。土壤微生物的优势菌群未发生较大的变化,土壤的优势细菌类群是变形菌门、放线菌门、酸杆菌门,而优势真菌类群为子囊菌门、担子菌门和被孢菌门。结构调整后油松人工林土壤微生物的丰富度显著增加,多样性较对照样地略有增加,但差异不显著。对结构调整前后的油松人工林微生物类群与土壤理化性质进行RDA分析,pH、总氮、土壤有机质和速效氮是驱动土壤微生物类群变化的主要因子。[结论]结构调整后的油松人工林样地仍处于恢复期,微生物类群结构与未调整样地相比具有相似性,但调整后的土壤微生物类群更为丰富,变形菌门和担子菌门的增加使得土壤中固氮菌的比例提高,土壤微生物类群向有助于有机质分解的方向转换。

辽东硼成矿带研究进展

辽东地区是我国重要的硼矿资源产地,赋存硼矿的胶-辽-吉带古元古时期处于活动陆缘环境。辽东硼矿成因为沉积变质再造矿床,硼物质源于蚀变洋壳、俯冲沉积物、蛇纹石化地幔楔等俯冲洋壳系统的富硼地体,在洋壳向克拉通俯冲过程中,硼质在弧前释放进入岛弧火山系统参与热液循环,通过海底热泉等热液方式汇集于火山盆地形成含水硼酸盐初始矿层并被随后的火山沉积覆盖保存。在区域变质变形过程中,含水硼酸盐脱水重结晶并就位于变形构造形成的有利部位富集成矿。辽东硼同位素组成特征反应了对源区储库重硼的继承性,因此,用于探讨矿床成矿地质环境更具意义,而非用于海相和非海相沉积简单的对比。同产于含硼岩系中的含铜硫铁矿矿床沉积时间稍晚于硼矿床,两者空间上呈错位产出,据此可辅助找矿预测工作。区域上虎皮峪-红石砬子-清河复式背斜是辽河旋回多幕变形作用叠加形成的,宏观上控制含硼岩系硼矿床的空间分布。通过总结以往工作,建立了辽东硼矿床成矿模式和找矿模型,分析了找矿方向,特别指出的是,部分盖县岩组地层出露地区,深部具有寻找隐伏硼矿的探索空间,未来找矿前景可期。

基于性能的通航桥梁抗船撞评估方法及应用研究

为合理有效地开展通航桥梁抗船撞性能评估,提出基于性能的桥梁抗船撞标准化评估方法。基于现行《公路桥梁抗撞设计规范》(JTG/T 3360-02-2020),从抗撞性能等级确定、设防代表船型确定、船撞力计算、船撞效应计算以及抗撞性能验算等方面,采用结构性能目标作为评估准则,建立桥梁抗撞性能评估各环节流程的标准化评估方法。以江苏扬中三桥为应用实例,运用该方法进行该桥20号墩抗撞性能评估,结果表明:20号墩桩基顺桥向抗弯性能不满足JX1级要求,其余验算结果满足要求,桥墩抗撞性能综合评估结果为不满足要求。参照评估结果该桥加装了浮动式防撞设施。桥梁抗撞性能评估标准化,可准确高效实现桥梁抗撞性能等级确定、船撞效应计算、抗撞性能验算等预期的评估功能要求。

基于自注意力机制与卷积神经网络的隧道衬砌裂缝智能检测

卷积操作固有的局部性,导致难以捕获裂缝的全局特征表示。针对这一问题,以YOLOv5网络框架为基础,通过融合自注意力机制和卷积神经网络提出一种高精度隧道衬砌裂缝智能检测算法ST-YOLO。构建一种双分支特征提取模块,分支一采用基于自注意力机制的Swin Transformer网络提取裂缝的全局特征,分支二采用基于卷积神经网络的CSPDarkent提取裂缝的局部细节特征;采用卷积注意力增强的特征融合模块对两个分支所提取的裂缝特征进行多尺度融合,以实现裂缝全局特征和局部细节特征互补;借助YOLOv5的解耦头模块输出得到裂缝的分类置信度和位置结果。为验证本文提出算法的有效性,选用SSD、YOLOv4、YOLOv5、EfficientDet、Faster-RCNN五种基于卷积神经网络的目标检测算法进行对比分析。结果表明:在本文构建的隧道衬砌裂缝数据集上,ST-YOLO模型的F1分数和AP分别为8395%和8526%,相较于五种对比算法具有更高的识别精度及更好的环境适应性,适用于实际隧道工程裂缝病害检测任务。