分类： 力学 >> 固体力学 提交时间： 2025-06-25 合作期刊: 《应用力学学报》
摘要： 基于圆筒轴对称问题的简化及修正贝塞尔函数的良好性质，构造了含待定函数的位移调和函数。应用所构造的位移调和函数，推导出无限长圆筒在圆筒内壁受局部均布压力下含待定函数的应力表达式，将含待定函数的应力表达式代入对应的边界条件，再采用傅里叶逆变换，求解得到位移调和函数中的待定函数，最终得到满足边界条件的三维应力解析解。采用ANSYS有限元软件，建立了参数化的轴对称应力分析仿真模型，模拟仿真了典型情况应力分布特征。通过理论分析与数值模拟相结合的方法，分析了几何尺寸的变化对三轴应力状态的影响规律，并将理论计算与数值模拟相比较，得到了良好的结果，说明本研究建立的三维解析解及有限元模拟基本准确可靠。
摘要： 目标：本文通过分析不同文化群体对中国建筑感知差异，提出中国传统建筑文化跨文化理解与体验优化策略。方法：采集三类游客访谈与网络文本数据，采用混合方法分析其感知差异。发现：（1）文化记忆影响感知生成路径；（2）游客情感结构存在文化心理差异；（3）文化价值观左右感知深度与偏好。局限：群体划分维度仍可深化、数据采集尚不够多模态、游客行为机制有待深入建模。结论：（1）为C群体突出集体记忆与家国叙事，（2）为A群体突出空间与制度结构类比信息，（3）为UA群体强化视觉-感官导向的内容设计。
分类： 力学 >> 固体力学 提交时间： 2025-06-25 合作期刊: 《应用力学学报》
摘要： 为了改进位移有限元法与虚拟裂纹闭合技术相结合的模型求解应变能释放率精度不高的问题，将非协调广义混合法与虚拟裂纹闭合技术融合，提出计算含裂纹板结构应变能释放率的非协调广义混合元方法。非协调广义混合元方法与虚拟裂纹闭合技术的承接关系简洁直观。非协调广义混合元方法可同时引入有限元模型的位移边界条件和应力边界条件，有限元模型理论性客观，且避免了传统混合法对角线上存在零元素会导致求解不稳定的弊端。另一方面，该方法的线性方程组可与位移有限元法的线性方程组共享相同的求解器，数值结果稳定。从理论上讲，通过该方法求得的位移、应力和节点力的数值结果精确度会更高。数值算例分析表明，通过非协调广义混合元与虚拟裂纹闭合技术相融合的方法求解所得应变能释放率的数值结果收敛稳定可靠，在相同网格密度下，数值结果精度优于非协调位移有限元方法。
分类： 力学 >> 固体力学 提交时间： 2025-06-25 合作期刊: 《应用力学学报》
摘要： 为进一步研究超固结非饱和黏性土的力学特性以及对所提超固结非饱和黏性土三剪次加载面模型进行真三轴数值试验验证，以江西红黏土为研究对象，采用PFC3D软件并基于Hill接触模型建立了柔性膜条件下的超固结非饱和黏性土常规三轴以及真三轴试验模型。对不同基质吸力、超固结程度、应力幅值下的静、动循环三轴试验进行颗粒流数值模拟研究，得到超固结非饱和黏性土试样应力-应变关系等宏观力学特性的演化规律，并从细观角度分析剪切过程中接触力链以及位移场的变化。将PFC3D数值模拟结果与超固结非饱和黏性土常规静、动三轴固结排水试验结果进行对比验证。结果表明，颗粒流软件模拟值与试验结果变化规律一致，可以较好地反映超固结非饱和黏性土应变软化、剪胀性以及动荷载条件下的棘轮效应和曼辛效应等力学特性。验证了颗粒流模型计算程序在模拟超固结非饱和黏性土应力-应变等基本力学特性方面的适用性，达到了可以进行数值试验的程度，表明所建颗粒流模型可以代替各种复杂加载条件下的超固结非饱和黏性土的室内试验。将颗粒流模型作为数字试验机来代替室内真三轴试验，对超固结非饱和黏性土的三剪次加载面模型理论结果进行验证。结果表明，本构理论计算结果与PFC3D数值模拟结果所表现出的趋势基本一致。Fredlund应力变量法相对于Bishop应力变量法而言要更为接近PFC3D模拟结果，具有较小的误差。
分类： 力学 >> 固体力学 提交时间： 2025-06-25 合作期刊: 《应用力学学报》
摘要： 多棱锥型钢管杆广泛应用于城市周边输电线路，管与管之间连接通常采用法兰连接，鉴于目前对于多棱锥型钢管杆挠度的理论计算方法研究相对较单一，本研究将根据梁的挠曲线微分方程理论，结合法兰节点螺栓滑移，推导出在常见荷载（弯矩M、水平力P和均布力q）作用下多棱锥型钢管杆挠度和附加弯矩的计算方法，建议按螺栓孔的间隙计算法兰盘的滑移量，并考虑相应的转角放大系数。最后，选取典型钢管杆进行对比分析，得出了一些重要结论，不考虑法兰螺栓滑移计算得到的位移值与有限元方法解约有7%的误差，附加弯矩引起的挠度占总挠度约为2%。
分类： 力学 >> 固体力学 提交时间： 2025-06-25 合作期刊: 《应用力学学报》
摘要： 为建立适合不同弹性边界的刚架屈曲问题的统一解法，对含弹性支撑刚架的屈曲载荷展开研究。首先基于改进傅里叶级数法建立刚架的容许位移函数表达式，然后利用最小势能原理得到屈曲的特征方程并通过求解矩阵特征值得到刚架的屈曲载荷。在支座处和梁、柱连接处设立线弹簧和旋转弹簧，通过调整弹簧的刚度值来模拟不同边界和不同连接方式。通过数值分析分别研究任意弹性边界下无侧移刚架和有侧移刚架的屈曲载荷，将屈曲载荷的结果与文献中的解析解进行对比，验证本研究方法的有效性及边界通用性，在此基础之上给出刚架的屈曲模态图。所提的改进傅里叶级数法能够为不同边界弹性约束的刚架屈曲提供有效的预测。
分类： 航空、航天科学技术 >> 航空、航天系统工程 提交时间： 2025-06-25 合作期刊: 《应用力学学报》
摘要： 为了研究气候实验室室内发动机开车时尾气小引射比降温排放的影响因素及影响规律，以一典型小涵道比发动机为研究对象，采用数值模拟的方法，在考虑发动机尾气组分及可变比热流体属性条件下，分析排气管道直径、管道入口距离及喷水降温对于发动机尾气小引射比排放特性的影响。结果表明：引射比与排气管道直径线性正相关，随管道直径的增大而增大；管道入口距离对引射比影响较小，但存在一个最佳管道入口距离；喷水降温会破坏引射流场激波结构，尾气射流速度亏损减少，引射比增大。
分类： 图书馆学、情报学 提交时间： 2025-06-24 合作期刊: 《文献与数据学报》
摘要： ［目的/意义］当下数字化浪潮席卷全球，人工智能作为科技领域最具颠覆性与变革性的力量，正以前所未有的迅猛态势全方位融入人类社会。哲学社会科学也无可阻挡地步入与人工智能深度融合的新纪元。展望未来，人工智能在哲学社会科学研究中的应用趋势将愈发显著。［方法/过程］在全面梳理人工智能在哲学社会科学研究中的发展历程、理论框架以及实现机制的基础上，选取中国社会科学院数量经济与技术经济研究所的“经济大数据与政策评估实验室”作为典型案例，深入剖析人工智能在该领域的应用趋势与发展前景，并针对性地提出政策建议。［结果/结论］提出人工智能在哲学社会科学研究中的融合前景和应用方式，拟为推动人工智能与哲学社会科学的深度融合提供切实可行的参考与借鉴。
分类： 航空、航天科学技术 >> 航空、航天系统工程 提交时间： 2025-06-25 合作期刊: 《应用力学学报》
摘要： 为了应用分布式光纤布拉格光栅（fiber Bragg grating，FBG）传感网络飞行实测直升机旋翼动载荷，综合分析旋翼桨叶的载荷与应变，以及FBG传感器的使用要求，设计了桨叶表面的FBG传感网络布设方案。在此基础上，提出基于FBG应变测量的工程建模方法和校准试验方法。以单项加载试验建立模型，复合加载试验验证模型，验证分析给出最大的载荷相对误差为3.83%，优于5%的飞行实测工程要求。使用FBG传感器和应变计等2种不同传感器，完成直升机旋翼动载荷对比试飞，测量结果在时域和频域都可以相互验证。试飞结果表明：FBG传感网络测量结果正确有效，基于分布式FBG传感测量的旋翼动载荷工程建模方法合理可行。
分类： 统计学 >> 经济统计学 提交时间： 2025-06-23
摘要： 根据国家统计局的数据，截至 2023 年，中国 60 岁及以上老年人口已超过 2.96 亿，占总人口的 21.1%。这一数据凸显了我国人口老龄化问题的严重性。在这种宏观背景下，传统的养老服务模式已经显示出明显的局限性。随着老年人口的持续增加，传统的养老方式正面临前所未有的压力和挑战。这不仅考验着社会福利体系，也迫使我们寻求创新的技术手段和服务模式来填补这一供给缺口。因此，智慧养老产业政策应运而生，它依靠先进的技术手段为老年人提供更高品质的生活。基于此，本文将探讨智慧养老产业政策干预下的“银发经济”，并全面分析这些外部和内部因素对经济增长的影响。本文基于 2008—2023 年中国省级面板数据，通过多维实证方法探讨智能养老政策对中国经济的影响机制，并重点关注资本投资、劳动效率和消费结构带来的中介效应。首先，采用双差法（DID）评价智慧养老试点政策的经济效果，结果表明，该政策的实施使试点地区的GDP增长率平均提高了约1.8个百分点，智慧养老政策对经济增长产生了显著的积极影响。其次，本研究在省级层面检验其机制，并采用中介效应模型发现，智能养老政策通过资本投入、劳动力供给和消费结构 3 条路径促进国内经济发展。当城市老龄化程度较低时，这种效果可能会减弱。最后，采用阈值模型分析智慧养老产业政策的异质性。当该地区人口老龄化，经济快速发展时，政策对经济发展的积极影响更加显著。研究表明，智慧养老产业政策通过促进产业结构升级、倒逼技术创新和需求侧激活的三重机制，有效促进了国民经济增长。建议构建“需求识别—技术赋能—政策协同”的立体化发展体系，针对区域老龄化和区域经济差异实施梯度产业政策。
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Measuring the Cosmic X-ray Background (CXB) is a key to understand the Active Galactic Nuclei population, their absorption distribution and their average spectra. However, hard X-ray instruments suffer from time-dependent backgrounds and cross-calibration issues. The uncertainty of the CXB normalization remain of the order of 20%. To obtain a more accurate measurement, the Monitor Vsego Neba (MVN) instrument was built in Russia but not yet launched to the ISS (arXiv:1410.3284). We follow the same ideas to develop a CXB detector made of four collimated spectrometers with a rotating obturator on top. The collimators block off-axis photons below 100 keV and the obturator modulates on-axis photons allowing to separate the CXB from the instrumental background. Our spectrometers are made of 20 mm thick CeBr$_{3}$ crystals on top of a SiPM array. One tube features a $\sim$20 cm$^2$ effective area and more energy coverage than MVN, leading to a CXB count rate improved by a factor of $\sim$10 and a statistical uncertainty $\sim$0.5% on the CXB flux. A prototype is being built and we are seeking for a launch opportunity.
摘要： Objective:This study analyzes the cultural perception differences of Chinese architecture among various cultural groups and proposes strategies for enhancing cross-cultural understanding and optimizing experiences of traditional Chinese architectural culture.Methods: Interviews and online textual data from three tourist groups were collected, and a mixed-method approach was used to analyze their perceptual differences.Findings: (1) Cultural memory influences the perceptual pathways; (2) There are cultural and psychological differences in the emotional structures of tourists; (3) Cultural values influence the depth and preferences of perception.Limitations: The dimension of group division could be further developed, the data collection is not multimodal enough, and the modeling of tourist behavior mechanisms requires deeper investigation.Conclusion: (1) For Group C, emphasize collective memory and national narratives; (2) For Group A, emphasize spatial and institutional structure analogies; (3) For Group UA, strengthen visual-sensory oriented content design.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We develop a framework for using clustering-based redshift inference (cluster-$z$) to measure the evolving galaxy luminosity function (GLF) and galaxy stellar mass function (GSMF) using WISE W1 ($3.4\mu m$) mid-infrared photometry and positions. We use multiple reference sets from the Galaxy And Mass Assembly (GAMA) survey, Sloan Digital Sky Survey (SDSS) and Baryon Oscillation Spectroscopic Survey (BOSS). Combining the resulting cluster-$z$s allows us to enlarge the study area, and by accounting for the specific properties of each reference set, making best use of each reference set to produce the best overall result. Thus we are able to measure the GLF and GSMF over $\sim 7500\, \mathrm{deg}^2 $ of the Northern Galactic Cap (NGC) up to $z<0.6$. Our method can easily be adapted for new studies with fainter magnitudes, which pose difficulties for the derivation of photo-$z$s. The measurement of the GSMF is currently limited by the models for k-corrections and mass-to-light ratios, rather than more complicated effects tied to the evolution of the differential galaxy bias. With better statistics in future surveys this technique is a strong candidate for studies with new emerging data from, e.g. the Vera C. Rubin Observatory, the Euclid mission or the Nancy Grace Roman Space Telescope.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The extragalactic background light (EBL) consists of integrated light from all sources of emission throughout the history of the universe. At near-infrared wavelengths, the EBL is dominated by stellar emission across cosmic time; however, the spectral and redshift information of the emitting sources is entangled and cannot be directly measured by absolute photometry or fluctuation measurements. Cross-correlating near-infrared maps with tracers of known redshift enables EBL redshift tomography, as EBL emission will only correlate with external tracers from the same redshift. Here, we forecast the sensitivity of probing the EBL spectral energy distribution as a function of redshift by cross-correlating the upcoming near-infrared spectro-imaging survey, SPHEREx, with several current and future galaxy redshift surveys. Using a model galaxy luminosity function, we estimate the cross power spectrum clustering amplitude on large scales, and forecast that the near-infrared EBL spectrum can be detected tomographically out to $z\sim 6$. We also predict a high-significance measurement ($\sim 10^2$-$10^4\sigma$) of the small-scale cross-power spectrum out to $z\sim 10$. The amplitudes of the large-scale cross power spectra can constrain the cosmic evolution of the stellar synthesis process through both continuum and the line emission, while on the nonlinear and Poisson noise scales, the high-sensitivity measurements can probe the mean spectra associated with the tracer population across redshift.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： With the development of modern radio interferometers, wide-field continuum surveys have been planned and undertaken, for which accurate wide-field imaging methods are essential. Based on the widely-used W-stacking method, we propose a new wide-field imaging algorithm that can synthesize visibility data from a model of the sky brightness via degridding, able to construct dirty maps from measured visibility data via gridding. Results carry the smallest approximation error yet achieved relative to the exact calculation involving the direct Fourier transform. In contrast to the original W-stacking method, the new algorithm performs least-misfit optimal gridding (and degridding) in all three directions, and is capable of achieving much higher accuracy than is feasible with the original algorithm. In particular, accuracy at the level of single precision arithmetic is readily achieved by choosing a least-misfit convolution function of width W=7 and an image cropping parameter of x0=0.25. If the accuracy required is only that attained by the original W-stacking method, the computational cost for both the gridding and FFT steps can be substantially reduced using the proposed method by making an appropriate choice of the width and image cropping parameters.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The recent NANOGrav finding of a common-spectrum process has invited interpretations as possible evidence of a primordial stochastic gravitational-wave background (SGWB) stronger than predicted by standard inflation+LCDM. Such an SGWB would contribute an extra radiation component to the background Universe which may affect its expansion history. As such, it may help alleviate the current Hubble tension, a novel connection between gravitational waves and cosmology. We demonstrate this by considering a cosmological model, the "standard inflation + stiff amplification" scenario, with two components added to the LCDM model: a stiff component (w=1) and the primordial SGWB. Previously, we showed that even for standard inflation, the SGWB may be detectable at the high frequencies probed by laser interferometers, if it is amplified by a possible early stiff era after reheating. Models that boost the SGWB enough to cause significant backreaction, however, must still preserve the well-measured radiation-matter equality, as precision cosmology demands. For that, we calculate the fully-coupled evolution of the SGWB and expansion history, sampling parameter space (tensor-to-scalar ratio, reheating temperature and temperature at stiff-to-radiation equality). We then perform a joint analysis of the NANOGrav results and latest upper bounds from Planck, big bang nucleosynthesis and Advanced LIGO-Virgo, to constrain the model. The resulting blue-tilted, stiff-amplified SGWB is still too small to explain the NANOGrav results. However, if someday, Advanced LIGO-Virgo detects the SGWB, our model can explain it within standard inflation (without requiring an initial blue tilt). Meanwhile, this model may bring current high-z measurements of the Hubble constant within 3.4 sigma of the low-z measurements by SH0ES (from 4.4 sigma) and within 2.6 sigma of those by H0LiCOW (from 3.1 sigma), reducing the tension.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Russell D. Marroquin
Viacheslav Sadykov
Alexander Kosovichev
Irina N. Kitiashvili
Vincent Oria
Gelu M. Nita
Egor Illarionov
Patrick M. O'Keefe
Fraila Francis
Chun-Jie Chong
Paul Kosovich
摘要： The flux of energetic particles originating from the Sun fluctuates during the solar cycles. It depends on the number and properties of Active Regions (ARs) present in a single day and associated solar activities, such as solar flares and coronal mass ejections (CMEs). Observational records of the Space Weather Prediction Center (SWPC NOAA) enable the creation of time-indexed databases containing information about ARs and particle flux enhancements, most widely known as Solar Energetic Particle events (SEPs). In this work, we utilize the data available for Solar Cycles 21-24, and the initial phase of Cycle 25 to perform a statistical analysis of the correlation between SEPs and properties of ARs inferred from the McIntosh and Hale classifications. We find that the complexity of the magnetic field, longitudinal location, area, and penumbra type of the largest sunspot of ARs are most correlated with the production of SEPs. It is found that most SEPs ($\approx$60\%, or 108 out of 181 considered events) were generated from an AR classified with the 'k' McIntosh subclass as the second component, and some of these ARs are more likely to produce SEPs if they fall in a Hale class with $\delta$ component. It is confirmed that ARs located in the western hemisphere produced the most SEPs recorded on the Earth's orbit. The resulting database containing information about SEP events and ARs is publicly available and can be used for the development of Machine Learning (ML) models to predict the occurrence of SEPs.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： We developed a fast and modular deep learning algorithm to search for lookalike signals of interest in radio spectrogram data. First, we trained an autoencoder on filtered data returned by an energy detection algorithm. We then adapted a positional embedding layer from classical Transformer architecture to a frequency-based embedding. Next we used the encoder component of the autoencoder to extract features from small (~ 715,Hz with a resolution of 2.79Hz per frequency bin) windows in the radio spectrogram. We used our algorithm to conduct a search for a given query (encoded signal of interest) on a set of signals (encoded features of searched items) to produce the top candidates with similar features. We successfully demonstrate that the algorithm retrieves signals with similar appearance, given only the original radio spectrogram data.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The determination of supermassive black hole (SMBH) masses is the key to understanding the host galaxy build-up and the SMBH mass assembly histories. The SMBH masses of non-local quasars are frequently estimated via the single-epoch virial black-hole mass estimators, which may suffer from significant biases. Here we demonstrate a new approach to infer the mass distribution of SMBHs in quasars by modelling quasar UV/optical variability. Our inferred black hole masses are systematically smaller than the virial ones by $0.3\sim 0.6$ dex; the $\sim 0.3$ dex offsets are roughly consistent with the expected biases of the virial black-hole mass estimators. In the upcoming time-domain astronomy era, our methodology can be used to constrain the cosmic evolution of quasar mass distributions.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： A general covariant local field theory of the holographic dark energy model is presented. It turns out the low energy effective theory of the holographic dark energy is the massive gravity theory whose graviton has 3 polarisations, including one scalar mode and two tensor modes. The Compton wavelength is the size of the future event horizon of the universe. The UV-IR correspondence in the holographic dark energy model stems from the scalar graviton's strong coupling at the energy scale that marks the breaking down of the effective field theory.
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