四川邛崃一批出土银元的分析与除锈保护

为了保护四川邛崃出土的一批银元,用SEM-EDS和XRD分析法对具有代表性的银元及锈蚀物成分进行了分析。结果显示,银元中除含主元素Ag之外,同时还含有一定量的Cu元素;表面锈蚀物大多数为铜的化合物——氧化亚铜和碱式碳酸铜,少量为角银。结合分析结果及试验,采用机械振动和5%EDTA二钠盐水溶液相结合的方法进行除锈,之后再缓蚀封护,并用有机玻璃制作的钱币专用盒封装存放。分析数据将为研究我国银元文物提供科学信息,保护方法将为银器类文物的保护提供应用实例。     

Performance-Based Vulnerability Assessment of Multi-Story Reinforced Concrete Structures Exposed to Pre- and Post-Earthquake Fire

Post-earthquake fire can potentially bring about much more damage than the earthquake itself. Performing a vulnerability assessment for a structure that has already sustained damage in an earthquake and is then exposed to fire is therefore of importance. This paper describes a performance-based investigation in which applied loads to a structure are appropriately quantified. To do so, a sequential structural analysis is performed on the Life Safety performance level of a three-story reinforced concrete frame selected from a building. For the analysis to be more realistic, the slab is also included in the frame analysis through the concept of effective length. The frame is first subjected to an earthquake load with the PGA of 0.30 g followed by a fire analysis, using the ISO834 fire curve and the iBMB fire curve. The time needed for the structure weakened by the earthquake to collapse under fire is then calculated. As a benchmark, fire-only analysis is also performed for the undamaged frame. Moreover, the effect of thermal spalling is considered in the slabs. The selected frame is evaluated under various failure criteria such as load capacity, displacement, and rate of displacement. The results show that no failure is observed when the frame is exposed to fire alone, either when using the ISO curve or the iBMB curve under various failure criteria. It is also shown that while the PEF resistance based on load capacity criteria under the ISO curve is around 120 minutes, it reduces to about 95 min under the iBMB curve. However, considering the rate of deflection failure criteria, the PEF resistance is around 103 min and 75 min under the ISO and the iBMB curves, respectively. It is then concluded that in the PEF analysis, the iBMB curve is more compatible with the concept of performance-based design than the ISO curve is.     

Seismic Fragility Evaluation of Lightly Reinforced Concrete Beam-Column Joints

Fragility functions play an essential role in evaluating the seismic vulnerability of structures. To establish the seismic fragility functions of lightly Reinforced Concrete (RC) beam-column joints, the Park-Ang Damage model has been amended to quantify the damage states and the modified Bouc-Wen-Baber-Noori model has been employed and implemented in ABAQUS to predict the structural hysteresis behavior. Following successful calibration of the numerical results of a RC test frame from literature, the proposed model has been utilized to assess the seismic fragility curves of low to mid-rise RC frames in Singapore for 30 scaled ground motions using incremental dynamic analysis approach.     

Assessment of Perforated Steel Beam-to-Column Connections Subjected to Cyclic Loading

This article presents a study of fully fixed (welded) perforated beam-to-column connections, used as strengthening techniques to seismic-resistant design. The effect of using non-standard novel web opening configurations of variable depths and positions is investigated. The improvements on the structural behavior foreshadow the enhancements gained using these perforated members. It is concluded that using large isolated perforations is an effective way of improving the behavior of connections enhancing their ductility, rotational capacity and their energy dissipation capacity. Moreover, the connections with novel openings outperform the conventional ones; therefore, they can be suitably used in the aseismic design of steel frames.     

The Effect of Accelerated Alteration on the Discrimination between Baltic and Romanian Amber

Ten geological samples (five from each source—Romanian amber and Baltic amber) in duplicate for five different media (air, water, saline, acid and basic) were subjected to thermal alteration at 80 ± 2°C for 12 weeks, in the dark. The samples were analysed before and after the accelerated alteration experiment by Fourier transform infrared spectroscopy, both in transmittance and reflectance mode, and the acquired spectra were statistically processed by multivariate data analysis, mainly using principal component analysis. The results of the experiment are useful in giving a better picture of how to discriminate between archaeological amber artefacts.     

The Use of Neutron Analysis Techniques for Detecting The Concentration And Distribution of Chloride Ions in Archaeological Iron

Chloride (Cl) ions diffuse into iron objects during burial and drive corrosion after excavation. Located under corrosion layers, Cl is inaccessible to many analytical techniques. Neutron analysis offers non‐destructive avenues for determining Cl content and distribution in objects. A pilot study used prompt gamma activation analysis (PGAA) and prompt gamma activation imaging (PGAI) to analyse the bulk concentration and longitudinal distribution of Cl in archaeological iron objects. This correlated with the object corrosion rate measured by oxygen consumption, and compared well with Cl measurement using a specific ion meter. High‐Cl areas were linked with visible damage to the corrosion layers and attack of the iron core. Neutron techniques have significant advantages in the analysis of archaeological metals, including penetration depth and low detection limits.     

贵州辛亥革命中“二·二”事变性质分析

1912年贵州“二·二”事变的发生,给辛亥革命后贵州政局的发展走向产生了重大影响。长期以来,无论是时人或后人,对“二·二”事变的认识和评价,都存在着分歧。在纪念辛亥革命发生100周年之际,分析贵州辛亥革命中“二·二”事变的性质,总结其经验教训,对于更加深入全面了解贵州辛亥革命史具有重要意义。     

多元统计分析方法在汉墓等级划分中的应用——以安徽南部西汉早期墓为例

一、前言在考古学研究中,墓葬研究占相当重要的地位。墓葬可以为研究者提供多角度的切入点,具有很多其他考古学资料所无法比拟的信息。有研究者指出,可以通过墓葬研究一个文化的面貌、特征、结构,文化的编年,建立一个文化的时空框架;可以通过墓葬研究一个文化的埋葬习俗,墓葬的埋葬规律以     

Numerical Simulation and Seismic Fragility Analysis of a Self-Centering Steel MRF with Web Friction Devices

This article presents the seismic fragility analysis of a self-centering steel moment-resisting frame (SC-MRF) with web friction devices. A detailed numerical model of the SC frame was developed using the Open System for Earthquake Engineering Simulation (OpenSees) and the elastoplastic responses of the SC-MRF were studied, including the strength degradation under cyclic loading, tendon rupture, beam buckling, bolt bearing and friction loss, etc. The proposed simulation approach is validated by comparing the simulated results with those in existing hybrid-simulation tests, quasi-static pushover test and low cyclic tests, where good agreement is observed. In addition to the well-established performance limit states (i.e., immediate occupancy, collapse prevention and global dynamic instability), two unique performance limit states (i.e., the recentering and repairable limit states) are defined for the SC-MRF. Finally, incremental dynamic analyses are conducted to evaluate the seismic fragilities regarding the five performance limit states.     

Nonlinear Structural Response to Low-Cut Filtered Ground Acceleration Records

Ground acceleration records obtained from instruments in the field are often filtered to reduce noise in both low and high frequency bands before being used for structural response analyses. The structural analysis using a filtered acceleration record may elongate the fundamental period of a structure which will potentially lead to an underestimation of the nonlinear response.

The nonlinear response of single-degree-of-freedom systems to low-cut filtered ground acceleration records is investigated. Based on the results of this study, a simple criterion for selecting ground acceleration records for seismic response analyses is proposed to avoid underestimating the nonlinear structural response.