Recollements from Cotorsion Pairs

Given a complete hereditary cotorsion pair $(\mathcal{A},\mathcal{B})$ in a Grothendieck category $\mathcal{G}$, the derived category $\mathcal{D}(\mathcal{B})$ of the exact category $\mathcal{B}$ is defined as the quotient of the category $\mathrm{Ch}(\mathcal{B})$, of unbounded complexes with terms in $\mathcal{B}$, modulo the subcategory $\widetilde{\mathcal{B}}$ consisting of the acyclic complexes with terms in $\mathcal{B}$ and cycles in $\mathcal{B}$. We restrict our attention to the cotorsion pairs such that $\widetilde{\mathcal{B}}$ coincides with the class $ex\mathcal{B}$ of the acyclic complexes of $\mathrm{Ch}(\mathcal{G})$ with terms in $\mathcal{B}$. In this case the derived category $\mathcal{D}(\mathcal{B})$ fits into a recollement $\dfrac{ex\mathcal{B}}{\sim} \mathrel{\substack{\textstyle\leftarrow\textstyle\rightarrow\textstyle\leftarrow}} {K(\mathcal{B})} \mathrel{\substack{\textstyle\leftarrow\textstyle\rightarrow\textstyle\leftarrow}} {\dfrac{\mathrm{Ch}(\mathcal{B})}{ex\mathcal{B} }}$. We will explore the conditions under which $\mathrm{ex}\,\mathcal{B}=\widetilde{\mathcal{B}}$ and provide many examples. Symmetrically, we prove analogous results for the exact category $\mathcal{A}$.Comment: Added Lemma 1.2 and fixed statement of Proposition 2.

Recollements from exact model structures and heart constructions in triangulated categories

We consider a complete hereditary cotorsion pair (A,B) in a Grothendieck category G such that A contains a generator of finite projective dimension. The derived category D(B) of the exact category B is defined as the quotient category of the category Ch(B), of unbounded cochain complexes with terms in B, modulo the subcategory tilde(B) consisting of acyclic complexes with terms and cycles in B. We prove that there are two recollements anologous to the classical one, with middle term being respectively D(B) and K(B). We study also some cases where there is a recollement involving both K(B) and D(B). Simmetrically, we prove analogous results for the exact category A. We also introduce the notion of Nakaoka contexts in additive categories as couples of torsion pairs t_1=(T_1,F_1) and t_2=(T_2,F_2) such that T_2 is included in T_1. We give a set of axioms for a Nakaoka context in order to ensure that the heart, i.e. the intersection between T_1 and F_2, is Abelian. Then, we inspect the properties of Nakaoka contexts in Abelian and triangulated categories. In particular, given a t-structure t_1 in a triangulated category, we are able to find a bijection between the Nakaoka contexts (t_1,t_2) with Abelian heart and the cohereditary torsion pairs in the heart of t_1

GEN-IV LFR development: Status & perspectives

Since Lead-cooled Fast Reactors (LFR) have been conceptualized in the frame of Generation IV International Forum (GIF), great interest has focused on the development and testing of new technologies related to Heavy Liquid Metal (HLM) nuclear reactors. In this frame, ENEA developed one of the larger European experimental fleet of experimental facilities aiming at investigating HLM thermal-hydraulics, coolant chemistry control, corrosion behavior for structural materials, and at developing components, instrumentations and innovative systems, supported by experiments and numerical tools. The present work aims at highlighting the capabilities and competencies developed by ENEA so far in the frame of the liquid metal technologies for GEN-IV LFR. In particular, an overview on the ongoing R&D experimental program will be depicted considering the actual fleet of facilities: CIRCE, NACIE-UP, LIFUS5, LECOR and HELENA. CIRCE (CIRColazione Eutettico) is the largest HLM pool facility presently in operation worldwide. Full scale component tests, thermal stratification studies, operational and accidental transients and integral tests for the nuclear safety and SGTR (Steam Generator Tube Rupture) events in a large pool system can be studied. NACIE-UP (NAtural CIrculation Experiment-UPgraded) is a loop with a HLM primary and pressurized water secondary side and a 250 kW power Fuel Pin Simulator working in natural and mixed convection. LIFUS5 (lithium for fusion) is a separated effect facility devoted to the HLM/Water interaction. HELENA (HEavy Liquid metal Experimental loop for advanced Nuclear applications) is a pure lead loop with a mechanical pump for high flow rates experiments. LECOR (LEad CORrosion) is a corrosion loop facility with oxygen control system installed. All the experiment actually ongoing on these facilities are described in the paper, depicting their role in the context of GEN-IV LFR development

A cohesive model to predict the loading bond capacity of concrete structures repaired/reinforced with HPFRC/UHPFRC and stressed to mixed mode

The risk of cracking/debonding of a cement overlay used to repair or strengthen an existing structure is still a key issue. Current bond test methods are not designed to measure the combined effect of peeling (mode I) and shear (mode.II) on the interface. A few existing models propose theoretical approaches to predict that, but they were fitted on specific cases and lack in generality. In addition, controversial opinions about the influence of both the moisture level of the substrate surface prior to the application of the overlay and properties of the latter on the loading bond capacity call for further investigations. In this work, a cohesive model is developed to predict the loading bond capacity of an existing concrete structure overlaid by a layer of HPFRC/UHPFRC. Different bond tests were specifically designed for calibrating the cohesive pa-rameters employed into the model, which also takes into account the type of the overlay used and the moisture conditioning level. An experimental cam-paign confirmed the reliability of the predictions of the proposed theoretical model

A cohesive FE model for simulating the cracking/debonding pattern of composite NSC-HPFRC/UHPFRC members

The aim of this work is to propose to practitioners a simple cohesive Finite-Element model able to simulate the cracking/debonding pattern of retrofitted concrete elements, in particular Normal-Strength-Concrete members (slabs, bridge decks, pavements) rehabilitated by applying a layer of High-Performance or Ultra-High-Performance Fiber-Reinforced-Concrete as overlay. The interface was modeled with a proper nonlinear cohesive law which couples mode I (tension-crack) with mode II (shear-slip) behaviors. The input parameters of the FE simulation were provided by a new bond test which reproduces a realistic condition of cracking/debonding pattern. The FE simulations were accomplished by varying the overlay materials and the moisture levels of the substrate surface prior to overlay, since findings about their influence on the bond performances are still controversial. The proposed FE model proved to effectively predict the bond failure of composite NSC-HPFRC/UHPFRC members

spatial temporal conditional auto regressive model a new autoregressive matrix

In the study of geographical patterns of disease, multivariate areal data models proposed so far in the literature (Ma and Carlin, 2007; Carlin and Banerjee, 2003; Knorr-Held and Best, 2001) have allowed to handle several features of a phenomenon at the same time. In this paper, we propose a new model for areal data, the Spatial Temporal Conditional Auto-Regressive (STCAR) model, that allows to handle the spatial dependence between sites as well as the temporal dependence among the realizations, in the presence ofmeasurements recorded at each spatial location in a time interval. Inspired by the Generalized Multivariate Conditional Auto-Regressive (GMCAR) model published by Jin, Carlin, and Banerjee (2005), the STCAR model reduces the unknown parameters to the single parameter of spatial association estimated at every period considered. Unlike the Vector Auto-Regressive (VAR) model proposed by Sims (1980), in addition, its space-time autoregressive matrix takes into account the spatial localization of the realizations sampled. Moreover, we already know that the main areas of application of these modelsrelate to disease mapping, disease clustering, ecological analysis (Lawson, Browne, and Vidal Rodeiro, 2003). In this work, however, the STCAR model is applied in business, exploiting the analogy between the danger of contracting a particular disease and the risk of falling into bankruptcy, in order to "reconstruct" the spatial temporal distribution of expected bankruptcies of small and medium enterprises of the province of Lecce (Italy)

Transient analysis of SIRIO using RELAP5/MOD3.3 system code

The main outcome of the present paper is the feasibility analysis of SIRIO (Sistema di rimozione della Potenza di decadimento per Reattori InnOvativi) facility with conditions based on those of its reference facility. The aim of SIRIO project is to study an innovative Decay Heat Removal System (DHRS) for liquid metal reactor and advanced Light Water Reactor (LWR). Such system must ensure passive control of the power removed from the primary system in abnormal condition, and must ensure reactor cooling in both short and long term. This study present numerical simulations developed with RELAP5/MOD3.3, of two operational procedures: the first one is a steady-state and the second one is a transient phase with decay heat generation. The thermal-hydraulic model, developed with RELAP5/MOD3.3, simulates the whole facility including lines, valves, water and gas tanks, and the Molten Salts (MS) gap. Since there is not experimental data, the present paper is a pre-test study based on SIRO facility design

Experimental investigation of catalan vault structures based on earthen materials

The Catalan vaulting have succeeded in reducing reliance on support centers, resulting in lowered costs and expedited construction processes. This research advances the study of Catalan vaulting by exploring innovative, environmentally friendly earth-based materials. The study conducts a comprehensive comparative analysis of load-bearing behaviors across distinct vault elements: those fabricated from terracotta, raw-earth tiles, and shot-earth. Constructed and tested at a 4-meter span, full-scale vault specimens are subjected to varying distributed load configuration, followed by rupture testing employing a linear load at a quarter of the span. Experimental evidence, corroborated by FE results, indicates that both terracotta and raw earth tile vaults offer commendable performance, yet their failure loads are surpassed by vaults constructed using shot-earth. Therefore, shot-earth emerges as a sustainable alternative for constructing vault elements. Furthermore, the study demonstrates that incorporating reinforcement within shot-earth vaults increases their strength and ductility

Structural design of reinforced earthcrete (ReC) beams

This paper presents the results of an extensive experimental campaign aimed at evaluating the feasibility of using steel-reinforced earthen materials for load-bearing structural applications, with a focus on a new category termed "shot-earth". Addressing excavated soil, a major source of construction waste, shot-earth demonstrates remarkable properties, such as notable green strength and reduced water sensitivity. The experimental program includes four-point bending tests on steel-reinforced shot-earth beams, along with pull-out tests to assess the adherence between ribbed steel bars and shot-earth. A flexural design approach, traditionally suited for reinforced concrete, is presented and validated to establish a reliable model for reinforced shot-earth elements in bending state. These findings suggest that leveraging existing models for reinforced concrete can overcome some traditional challenges associated with earth-based constructions, promoting them as a viable and ecological alternative to conventional construction materials