Passive Control of Steel Storage Racks for Parmigiano Reggiano Cheese under Seismic Accelerations

Recent earthquakes in Italy resulted in the collapse of steel storage racks for aging Parmigiano Reggiano cheese, damaging a huge number of cheese wheels. In order to improve the seismic performance of surviving racks with low-budget solutions, when replacement cannot be considered, we investigate the possibility of using viscous dampers that connect the racks to a surrounding structure. Time-history analyses with natural and spectrum-compatible artificial accelerograms allow one to determine the optimal damping factor that reduces both the stress in the rack and the actions transmitted to the constraining structure. Results confirm the noteworthy benefits of the proposed retrofitting system.     

On Classic Maya political economies

Lowland Maya political economies are cosmopolitical economies, with “authoritative resources”—knowledge (“symbolic capital”), especially astro-calendrical knowledge, and ostensible control of time—evolving as the basis for Classic wealth, power, and dynastic legitimacy. Within a system of rotating geopolitical capitals, elite economic activities of production, consumption, and distribution were directed toward control of luxury goods and ritual performances emphasizing privileged interactions with the cosmos and ancestors. Examples include a “ritual mode of production” focused in a palace economy, consumption manifest in lavish public rituals and feasting, and goods circulating through tribute and periodic markets. In the dispersed lowland Maya settlement system, this decentralized economy retained some features more characteristic of stateless societies.     

Process, perception, and practice: Time perspectivism in Yosemite native demography

Multiple concepts of time apply to archaeology—from analytical time used to organize and interpret the archaeological record to the time of lived experience of those individuals responsible for creation of the archaeological record. This paper demonstrates how these disparate concepts of time can be reconciled through a perception-based approach to time perspectivism, which invokes multiple analytical scales working from the minimum scale of the average human lifespan. This approach is demonstrated through a case study of hunter–gatherer demographic change in Yosemite Valley in the central Sierra Nevada of California.     

故宫灵沼轩风振响应分析

故宫灵沼轩是一座砌体结构与钢结构组合而成的文物建筑。为有效对其保护,采用数值模拟方法,研究了风振作用下结构的动力响应。基于灵沼轩结构现状,建立了有限元模型。通过模态分析,获得了灵沼轩的基频和主振型;通过对结构施加y向脉动风荷载,研究了重现期为50年时结构的风振特性,评价了结构在风荷载作用下的安全现状。结果表明:灵沼轩结构基频为f=5.75Hz,在x及y向的主振型以局部振动为主;脉动风压作用下,结构保持稳定振动状态,但顶部位置加速度峰值偏大。另风压作用下,砌体结构部分位置的抗拉强度不足,应在日常维护中予以重视;钢结构部分由于材料强度大,因而不会出现强度破坏。     

Influence of Time Step of Ground Motions on Site Effect and Structural Response Analyses for Long-Duration Earthquakes

Long-duration ground motions may be down-sampled to speed up the computational process. However, using ground motions with large time step (Δt) would inevitably bring in numerical errors. The influence of Δt on the site effect and structural response analyses was quantitatively examined in this study. The results show that the nonlinear site response method is more sensitive to a change of Δt than the equivalent-linear method. For the structural analysis, the impact of Δt is highly dependent on the magnitude of damage parameters. Thus, using input motions with Δt as 0.005 s is recommended for structures subjected to strong shakings.     

试析历史地理学在人地关系研究中的时间特征

人地关系是历史地理学研究的核心。本文以系统方法论为指导,对人地关系发展过程中所体现出来的宏观、中观和微观的时间特征进行了初步分析,认为历史地理学在探讨人地关系中,其所揭示的过程是完整性和阶段性、连续性与差异性的统一过程,因而是最富有揭示人地关系动态过程及其规律的学科之一。     

Stochastic Non-Stationary Model for Ground Motion Simulation Based on Higher-Order Crossing of Linear Time Variant Systems

This article introduces a new time-varying model to generate synthetic non-stationary acceleration records using the modified Kanaii-Tajimi model with time-variant parameters. The proposed method can capture two different dominant frequencies per time which makes it suitable for synthesizing the near-field no-pulse earthquake records. A number of closed-form relationships are developed to describe the frequency dependent time-domain level crossings of the simulated records under white noise excitation. The model parameters are optimized using the crossing and Arias intensity properties of the synthetic and target records. The efficiency of the proposed model is demonstrated using a data base of 106 near-field records.     

《鄂城六朝墓》读后

时间与空间是解读考古材料的基本概念,在魏晋南北朝考古研究中更有其特殊的内涵,如在墓葬的断代与分期、区域文化因素的分析、遗存属性探讨等方面,时空背景是对材料进行深入研究的基础,也是历史考古学研究方法论的基本内容。新近出版的《鄂城六朝墓》报告不仅充实了魏晋南北朝考古材料,而且对于魏晋南北朝考古研究中的时间与空间两个基本概念,也带来了新认识。     

Disciplining Memory: Heritage Tourism and the Temporalisation of the Built Environment in Rural France

This article presents an ethnographic case study of the relationship between the development of heritage tourism, and the role of material culture in memory practices in rural Southern France. Drawing on anthropological fieldwork in the village of Monadières, it provides an analysis of how artefacts in the locality's built environment have been renovated and revalued in a climate of historical change. This was the consequence of varied acts of commemoration by both independent individuals and the local council in which heritage tourism development was not necessarily the end‐goal. Nevertheless, these acts were implicated in the council's ‘disciplinary programme’ to produce a local infrastructure for heritage tourism. The article therefore explores how this industry co‐habits with and colonises modern memory practices at a micro‐level. To this end it adapts analytical tools from the anthropology of time, which enable an integrative analysis of these differing ‘temporalisations’ of the past.     

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.