Processing eutectics in space

The investigations of directional solidification have indicated the necessity of establishing a secure foundation in earth-based laboratory processing in order to properly assess low-gravity processing. Emphasis was placed on evaluating the regularity of microstructure of the rod-like eutectic Al-Al3Ni obtained under different conditions of growth involving the parameters of thermal gradient, solidification rate, and interfacial curvature. In the case of Al-Al3Ni, where the Al3Ni phase appears as facets rods, solidification rate was determined to be a controlling parameter. Zone melting of thin eutectic films showed that for films of the order of 10 to 20 micrometers thick, the extra surface energy appears to act to stabilize a regular microstructure. The results suggest that the role of low-gravity as provided in space-laboratory processing of materials is to be sought in the possibility of generating a higher thermal gradient in the solidifying ingot for a given power input-output arrangement than can be obtained under normal one-g processes

Processing eutectics in space

Experimental work is reported which was directed toward obtaining interface shape control while a numerical thermal analysis program was being made operational. An experimental system was developed in which the solid-liquid interface in a directionally solidified aluminum-nickel eutectic could be made either concave to the melt or convex to the melt. This experimental system provides control over the solid-liquid interface shape and can be used to study the effect of such control on the microstructure. The SINDA thermal analysis program, obtained from Marshall Space Flight Center, was used to evaluate experimental directional solidification systems for the aluminum-nickel and the aluminum-copper eutectics. This program was applied to a three-dimensional ingot, and was used to calculate the thermal profiles in axisymmetric heat flow. The results show that solid-liquid interface shape control can be attained with physically realizable thermal configurations and the magnitudes of the required thermal inputs were indicated

Processing eutectics in space

Studies which have been done in an earth-based laboratory environment have generally not yielded specimens with the degree of perfection required of the eutectic microstructure to provide test data to evaluate their nonstructural applications. It has been recognized that the low-g environment of an orbiting space laboratory provides a unique environment to re-examine the process of solidification with the goal of producing better microstructures. The objective of this program is to evaluate the feasibility of using the space environment for producing eutectics with microstructures which can be of value on earth. In carrying out this objective, evaluative investigations were carried out on the technology of solidification in a 1-g environment to provide sound baseline data for planning space laboratory experiments

Designing hybridization: alternative education strategies for fostering innovation in communication design for the territory

Within the broad context of design studies, Communication Design for the Territory stands as a hybrid discipline constantly interfacing with other fields of knowledge. It assumes the territorial theme as its specific dimension, aiming to generate communication systems capable of reading the stratifications of places. From an educational perspective, teaching activities are closely linked to research and can take on different levels of complexity: from the various forms of cartographic translation to the design of sophisticated transmedia digital systems. In the wake of COVID-19, this discipline has come to terms with a profoundly changed scenario in terms of limited access to the physical space and the emergence of new technologies for remote access. In this unique context, we propose a pedagogical strategy that focuses on the hybridization of communication artifacts with the aim of fostering design experimentation. As a creative tool, hybridization leads to the design of innovative systems by strategically combining the characteristics of different artifacts to achieve specific communication goals. By experimenting with these creative strategies, students are led to critically reflect on existing communication artifacts’ features and explore original designs that deliberately combine different media, contents, and communication languages in innovative ways. Through hybridization, the methods for territorial knowledge production appear more effective, effectively combining the skills and knowledge embodied in multiple subject areas. The paper presents the experience developed in the teaching laboratories of the DCxT (Communication Design for the Territory) research group of the Design Department of Politecnico di Milano. The teaching experience highlights how hybridization strategies can increase the effectiveness in learning about territorial specificities, in acquiring critical knowledge about communication systems, and in developing innovation strategies that allow to influence the evolution of traditional communication models

Advancements in multi-rupture time-dependent seismic hazard modeling, including fault interaction

Several recent earthquake events (e.g., 2008 moment-magnitude (M_{W}) 8.0 Wenchuan, China; 2016 M_{W} 7.8 Kaikōura earthquake, New Zealand; 2019 M_{W} 6.4–7.1 Ridgecrest sequence, USA) have emphasized the need to explicitly account for fault sources in probabilistic seismic hazard analysis (PSHA). Fault-based PSHA currently involves a number of significant but necessary modeling assumptions that mainly relate to fault segmentation, multi-segment event occurrence, long-term fault interaction, and time-dependent/independent earthquake recurrence. Each of these issues is typically investigated in isolation, neglecting the implications of their dependencies. This study offers a review of the current literature on fault-based PSHA, unifying state-of-the-art advances in the field within a single harmonized framework. The framework specifically incorporates some underlying methodologies of the latest Uniform California Earthquake Rupture Forecast (UCERF3; Field et al., 2014), providing a comprehensive means of relaxing fault segmentation, accounting for multi-segment ruptures in a standardized way, interpreting available fault data (e.g., slip rates and paleoseismic data) consistently, and inferring time-dependent probabilities of mainshock occurrence. The proposed framework also explicitly accounts for fault-interaction triggering between major known faults, using the approach outlined by Mignan et al. (2016) and Toda et al. (1998). A simple case study is established to demonstrate the framework's capabilities and limitations, involving a holistic investigation of the aforementioned modeling assumptions' effect on the seismic hazard estimates. The main findings of this study are (1) the ground-motion amplitude estimates can change significantly (for certain return periods) depending on the segmentation assumptions used (e.g., strict segmentation or relaxed segmentation, excluding multi-segment ruptures); (2) considering an ensemble of faults with a time-dependent occurrence model changes the shape of the hazard curve with respect to the time-independent assumption; (3) faults with the largest contribution to the hazard can differ between the time-dependent and time-independent cases; and (4) accounting for fault interaction may change the hazard estimates with respect to those obtained using classic time-dependent analysis (for which fault interaction is neglected). The framework provides a clear means of leveraging paleoseismic campaigns and slip rate data collections to potentially better constrain hazard estimates

A computational framework for selecting the optimal combination of seismic retrofit and insurance coverage

Economic earthquake losses can be mitigated through either building retrofit strategies and/or, to some extent, risk-transfer to the (re)insurance market. This paper proposes a computational framework to select the optimal combination of seismic retrofit and insurance policy parameters for buildings. First, a designer selects a suitable retrofit strategy. This is implemented incrementally to define interventions with increasing retrofit performance levels. The cost of each intervention is calculated, along with the cost of property rental while the retrofit is implemented. Alternative insurance options are considered. For each retrofit-insurance combination, the insured and uninsured economic losses within a given time horizon are estimated. The optimal retrofit and insurance combination minimizes the tail value at risk of the life cycle cost. The selected confidence level for this metric depends on the homeowner's risk aversion. The proposed framework is illustrated for a case-study archetype Italian reinforced concrete frame building retrofitted with concrete jacketing, also considering the Italian retrofit tax incentives/rebates called “Sismabonus.

Modeling damage accumulation during ground-motion sequences for portfolio seismic loss assessments

Conventional earthquake risk assessments use fragility and vulnerability models that are based on seismic demands from individual (mainshock) ground motions, and implicitly assume that a structure is intact before an earthquake hits. This study develops a suite of more realistic state-dependent seismic fragility and vulnerability models for a wide range of building taxonomies, leveraging state-of-the-art methods to account for dynamic damage accumulation in structures due to multiple earthquake events (i.e., ground-motion sequences). Models are developed for 561 building classes (i.e., structural types) from the Global Earthquake Model's global database of fragility and vulnerability models. Four 2010–2012 Canterbury sequence earthquakes are then used to demonstrate an application of the developed models within a portfolio loss assessment, capturing the time-dependent nature of damage and loss in the vulnerability calculations. The results of this application indicate that accounting for damage accumulation across a series of events can significantly increase expected loss ratios compared to a conventional mainshock-only portfolio risk analysis. This work can help analysts to develop and apply state-dependent fragility and vulnerability models for quantifying the potential impact of damage accumulation in portfolio-scale seismic loss assessments

Material Property Uncertainties versus Joint Structural Detailing: Relative Effect on the Seismic Fragility of Reinforced Concrete Frames

This paper investigates the relative effect of material properties and structural details in the joint panels on the seismic fragility of existing reinforced concrete (RC) frames. Five building classes with different structural details (particularly in the joint panels) and material characteristics are defined according to different past design codes, for a three-story and a six-story archetype geometry. Based on nonlinear static or nonlinear dynamic analysis procedures, results from the study show that the effect of structural details on seismic fragility of the considered structures is negligible for damage states involving an essentially elastic behavior. Conversely, it is much higher for life-safety and near-collapse damage states, and it is considerably higher than the effect due to materials. Therefore, in the diagnosis phase, higher emphasis should be given to on-site investigations of actual reinforcement content/layout rather than to invasive material testing. The uncertainty related to the structural details described here is practically related to exterior, rather than interior, joint panels. Cover removal for one of those joints may potentially eliminate this specific uncertainty. As a practical action, in situ testing of RC frames should involve the cover removal of at least one exterior joint panel regardless of the required target “level of knowledge” of the existing structure

Market Power and Patent Strategies: Evidence from Renaissance Venice

This paper exploits the introduction of the first regularized patent system, which appeared in the Venetian Republic in 1474, to examine the factors shaping inventors\u2019 propensity to use a new form of intellectual property. We combine detailed information on craft guilds and patents in Renaissance Venice and show a negative association between patenting activity and guild statutory norms that strongly restricted entry and price competition. Our analysis shows that the heterogeneity in patenting activity documented by the industrial organization literature is not a special feature of modern technologies, but is rather a persistent phenomenon affected by market power

Impact of time-dependent earthquake recurrence modelling on probabilistic seismic hazard analysis

The (re)insurance industry has traditionally used a memoryless, time-independent (i.e., Poissonian) model for representing earthquake recurrence in seismic loss (risk) calculations. However, time-dependent renewal models, which account for the time elapsed since the last event, are more appropriate for modelling the longterm characteristics of cyclical mainshock occurrences in fault-based seismic hazard assessments. This study first reviews the main features and advantages of some of the most used time-dependent models for mainshock recurrence, and provides a critical discussion on their calibration and possible combination. A simple casestudy fault is used to quantify the changes in seismic hazard estimates resulting from the use of time-dependent Brownian Passage-Time (BPT) models instead of the conventional Poisson process. The considered fault is the Ohariu Fault in New Zealand, which is one of the major sources of earthquake hazard for the city of Wellington. BPT model parameters are calibrated using the maximum likelihood estimation (MLE) method together with paleoseismic data published in the literature. Results from this study show that the use of a timedependent BPT model can lead to a significant over- or under-estimation of the seismic hazard compared to the time-independent Poisson model, depending on the ratio between the time elapsed since the last event and the mean recurrence time of the fault. The simple single-fault case study also highlights the potential need for a combination of time-dependent models in actual earthquake risk models, since the single BPT model produces unrealistically low seismic hazard estimates for time periods in the immediate aftermath of an earthquake occurrence