A survey on maximal green sequences

Maximal green sequences appear in the study of Fomin-Zelevinsky's cluster algebras. They are useful for computing refined Donaldson-Thomas invariants, constructing twist automorphisms and proving the existence of theta bases and generic bases. We survey recent progress on their existence and properties and give a representation-theoretic proof of Greg Muller's theorem stating that full subquivers inherit maximal green sequences. In the appendix, Laurent Demonet describes maximal chains of torsion classes in terms of bricks generalizing a theorem by Igusa.Comment: 15 pages, submitted to the proceedings of the ICRA 18, Prague, comments welcome; v2: misquotation in section 6 corrected; v3: minor changes, final version; v4: reference to Jiarui Fei's work added, post-final version; v4: formulation of Remark 4.3 corrected; v5: misquotation of Hermes-Igusa's 2019 paper corrected; v5: reference to Kim-Yamazaki's paper adde

Material Cost Comparison for Masonry and Framed Partition Walls for Buildings in Uganda

In the building construction industry, decisions concerning specifications for the different building components may be made by the client, consultants, contractor, or a combination of these. Choices are usually governed by functionality (strength and safety integrity, durability), aesthetics, cost, material availability, technical know-how, etc. Most of these criteria are easy to quantify except for strength, safety, durability, and cost given that they require rigorous analysis or research. This study set out to determine the cost margin difference that exists between wall types (framed and masonry wall) from a material requirements perspective. This was meant to avail information that can provide decision support to practitioners or clients that need to make a choice between these wall types. Margins for cost differences were computed using a Monte-Carlo simulation-based approach that involved sampling deviates from probability distributions for costs for 1m2 of framed and masonry walls. These costs were built-up through another Monte-Carlo simulation process that utilized material quantities and unit prices as its inputs. There was transformation work done in this simulation experiment to reconcile material quantity conventions used by vendors and manufacturers with those quantities required to erect 1m2 of a physical wall. Keywords: Framed wall, Masonry wall, Cost margin, Probability distribution, Monte-Carlo simulation DOI: 10.7176/CER/12-5-05 Publication date:May 31st 202

Age determination and authentication of ceramics: advancements in the thermoluminescence dating laboratory in Torino (Italy)

13Classified as an absolute dating method, thermoluminescence (TL) is a well-established radiation-based technique for the age determination and authentication of ceramic materials. Specifically, this method allows the determination of the time elapsed since kiln firing (or later fire events) by evaluating the luminescent emission of ceramics under heating at high temperatures. This paper provides a comprehensive presentation of the TL laboratory developed over the last decade at the Physics Department of the University of Torino. The laboratory was set up in collaboration with TecnArt S.r.l. and is also currently operating within the cultural heritage network of the National Institute of Nuclear Physics (INFN-CHNet). More than 10 years of experience in the field has resulted in improvements in procedures, with the development of customised alpha- and beta-irradiation systems and the optimisation of sampling approaches and chemical pre-treatment. Thanks to TecnArt S.r.l., the laboratory has been employed for dating and authenticating hundreds of archaeological sites and artworks, some of which are discussed in this work and compared, when possible, with radiocarbon dating.openopenGuidorzi, Laura; Fantino, Fulvio; Durisi, Elisabetta; Ferrero, Marco; Re, Alessandro; Vigorelli, Luisa; Visca, Lorenzo; Gulmini, Monica; Dughera, Giovanni; Giraudo, Giuseppe; Angelici, Debora; Panero, Elisa; Lo Giudice, AlessandroGuidorzi, Laura; Fantino, Fulvio; Durisi, Elisabetta; Ferrero, Marco; Re, Alessandro; Vigorelli, Luisa; Visca, Lorenzo; Gulmini, Monica; Dughera, Giovanni; Giraudo, Giuseppe; Angelici, Debora; Panero, Elisa; Lo Giudice, Alessandr

Rainfall interception by buildings for urban hydrology modeling

One of the results of elimate change is an increased amount of precipitation and a rise in rainfall intensity. This can lead to an overlaad on the sewer system or to the ground water level if no sewer system is present, and even to flooding. During rain events part of the rainwater can be intercepted by building surfaces (rainfall interception) . This amount of water is temporarily stared on these surfaces and eventually evaporates into the atmosphere. Since this intercepted water does nat reach the ground, it also does nat contribute to the laad on the sewer system. Especially porous materials on building roots but also in facades can intercept large quantities of water. Rainfall interception by buildings therefore becomes more and more important in hydrological modeling, particularly in urban areas. In this research rainfall interception by building facades is studied. In order to do this measurements as well as simulations are performed. Full-scale measurements are executed on a test facade at Eindhoven University of Technology, the Netherlands. The moisture response (mass change) to wind-driven rain of tour material samples is registered. Furthermore micro-meteorological data are gathered. The ditterenee in rainfall interception by two porous building materials is demonstrated. For the brick with high porosity the rainfall interception yields 100%, while the low porous brick accommodates for a minimum of 76.6% during the measurement period. Due to local saturation at the exterior boundary runaft occurred for the latter type of brick. Besides the tuli-scale experiments an extensive set of Iabaratory measurements is performed. Various moisture-related material properties are determined for the two porous building materials. For the numerical part of this study the finite element code HAMFEM is used. Toga in insight into the moisture response of porous building materials to wind-driven rain, one-dimensional heat and moisture transfer simulations are performed using differential balance equations for mass and energy. The micro-meteorological data gathered at the test facade are used as atmospheric boundary conditions and the results of the Iabaratory experiments are used to specity the material properties. The simulation results give the mass change of the materials in time and this is compared to the mass change obtained trom the tuli-scale measurements to verify the correct implementation of the model and the capability to reproduce the measurement results. lt is shown that for the brick with high porosity the model accurately prediets the rainfall interception during one rain event. Rainfall interception foranother rain event is described less precisely however. For the other type of brick the model fails to predict runoff because in the simulations the exterior boundary does nat reach the capillary moisture content, while in reality local saturation does occur because the wind-driven rain intensity on the facade exceeds the absorption rate of the brick. The largest deviations between experimental and numerical results are found in the evaporation process, where the model overestimates the mass decrease due to evaporation. This is to a large extent due to the uncertainty of the heat and moisture transfer coefficients. As a next step meteorological data of several elimate groups according to the Köppen elimate classification are used to specify the boundary conditions. With this the influence of different climates on rainfall interception is studied. lt is shown that for four of the six elimate groups used for the analysis no runoff occurred for the brick with high porosity for the period considered . This means that this type of brick accommodates for 100% rainfall interception in these climates. For the remaining two elimate groups the brick with high porosity yields a minimum RI of only 1.9% and 6% in periods of severe rain, increasing to 100% for moderate rain events. Comparison of the rainfall interception by the two bricks results in a rainfall interception of at least 40% by the brick with low porosity based on the rainfall interception by the other type of brick. lt is demonstrated however that the model nat always succeeds in accurately predicting the runoff. Therefore no hard conclusions can be drawn on the performance regarding rainfall interception by the two porous building materia Is in other climates. One of the results of elimate change is an increased amount of precipitation and a rise in rainfall intensity. This can lead to an overlaad on the sewer system or to the ground water level if no sewer system is present, and even to flooding. During rain events part of the rainwater can be intercepted by building surfaces (rainfall interception) . This amount of water is temporarily stared on these surfaces and eventually evaporates into the atmosphere. Since this intercepted water does nat reach the ground, it also does nat contribute to the laad on the sewer system. Especially porous materials on building roots but also in facades can intercept large quantities of water. Rainfall interception by buildings therefore becomes more and more important in hydrological modeling, particularly in urban areas. In this research rainfall interception by building facades is studied. In order to do this measurements as well as simulations are performed. Full-scale measurements are executed on a test facade at Eindhoven University of Technology, the Netherlands. The moisture response (mass change) to wind-driven rain of tour material samples is registered. Furthermore micro-meteorological data are gathered. The ditterenee in rainfall interception by two porous building materials is demonstrated. For the brick with high porosity the rainfall interception yields 100%, while the low porous brick accommodates for a minimum of 76.6% during the measurement period. Due to local saturation at the exterior boundary runaft occurred for the latter type of brick. Besides the tuli-scale experiments an extensive set of Iabaratory measurements is performed. Various moisture-related material properties are determined for the two porous building materials. For the numerical part of this study the finite element code HAMFEM is used. Toga in insight into the moisture response of porous building materials to wind-driven rain, one-dimensional heat and moisture transfer simulations are performed using differential balance equations for mass and energy. The micro-meteorological data gathered at the test facade are used as atmospheric boundary conditions and the results of the Iabaratory experiments are used to specity the material properties. The simulation results give the mass change of the materials in time and this is compared to the mass change obtained trom the tuli-scale measurements to verify the correct implementation of the model and the capability to reproduce the measurement results. lt is shown that for the brick with high porosity the model accurately prediets the rainfall interception during one rain event. Rainfall interception foranother rain event is described less precisely however. For the other type of brick the model fails to predict runoff because in the simulations the exterior boundary does nat reach the capillary moisture content, while in reality local saturation does occur because the wind-driven rain intensity on the facade exceeds the absorption rate of the brick. The largest deviations between experimental and numerical results are found in the evaporation process, where the model overestimates the mass decrease due to evaporation. This is to a large extent due to the uncertainty of the heat and moisture transfer coefficients. As a next step meteorological data of several elimate groups according to the Köppen elimate classification are used to specify the boundary conditions. With this the influence of different climates on rainfall interception is studied. lt is shown that for four of the six elimate groups used for the analysis no runoff occurred for the brick with high porosity for the period considered . This means that this type of brick accommodates for 100% rainfall interception in these climates. For the remaining two elimate groups the brick with high porosity yields a minimum RI of only 1.9% and 6% in periods of severe rain, increasing to 100% for moderate rain events. Comparison of the rainfall interception by the two bricks results in a rainfall interception of at least 40% by the brick with low porosity based on the rainfall interception by the other type of brick. lt is demonstrated however that the model nat always succeeds in accurately predicting the runoff. Therefore no hard conclusions can be drawn on the performance regarding rainfall interception by the two porous building materia Is in other climates

Preparation and Analysis of Cement Bricks Based on Rice Straw

In Egypt, rice straw is burnt as an easy and the cheap method to get rid of it leads to making a giant black cloud covers Cairo and southern delta governorates. Main purpose of this research is to produce green brick of cement and in-expensive agriculture waste (rice straw) with law price and good characteristics of thermal insulation and acoustic resistance. Different samples of cement brick based on rice straw of many percentages were prepared. First, select best mixture of concrete brick before adding rice straw after preparing and leave for curing time. Then, rice straw is added with various percentage based on total mass of dry mixture to selected concert brick mixture. The selection of best mixture of green bricks criteria is first depending on achieving minimum compression strength according to Egyptian specification then maximizing the percentage of rice straw added. The two mixtures of cement bricks that have maximum compression strength are 1:2:2 and 1:4:5 of 6.2 and 3.1 MPa. The highest percentage of rice straw can be added to later cement mixture is 3% additional quantities based on total mass of mixture dry base of 2.9 MPa. The impact of 3% addition of rice straw on cement bricks enhances thermal by 21.05% by comparing with cement brick of ratio 1:2:2. It decreases sound pressure level inside room from 62 dB to 45 dB. Although, cement bricks reduce sound pressure level to 55 dB. Thousands of cement bricks with 3% rice straw cost are less 8.3% the cost of thousands of cement brick with market ratio 1:4:5. Cement brick of ratio 1:4:5 that used by OPAKI company in Egypt for cement brick manufacturing is used with adding 3% of rice straw. Whatever, it gives very low resistance against compression lower than Egyptian specifications. This mixture of 3% rice straw base is enhanced by nano-silicon addition percentage of sand portion of 2.1 MPa compression test, although cost of thousand bricks is almost equal to the cost of thousands of commercial market bricks. Eventually, life cycle assessment of rice straw is better than normal cement brick mixture materials that helps in reducing greenhouse emissions and energy consumed

EFFECT OF ADDITION OF NANO SILICON DIOXIDE TO CEMENT BRICKS: PREPARATION AND CHARACTERICTICS

The aim of the research is to design and produce a durable, and high load, bearing build constructing bricks based on cement, sand, and aggregates with the addition of Nano silica, studying the effect of the added materials to get a background about the impact of the Nano silica on the ability of using such a product. The cement used is 52.5 grade which represent the strength of the cement, sand with particle size 300-600 micrometer, aggregates with diameter lays between 0.5-1 cm better to use smaller size, water, and finally Nano-silica with particle size 17 nm with purity higher than 99.9%. the final size of the produced brick is a cubic shape with 4*4*4 cm in dimension. The research results have been achieved and stated that as the percentage of the Nano silica increase the strength increase and the bricks withstood for more loads and nominated the 10% Nano-silica of the total weight or of the cement weight as the best percentage among the prepared samples percentages and gives a strength of 6.4 MPa

Lucretius or the philosophy of chemistry

A world view deriving from the objective knowledge acquired by the physical sciences is contrasted with the fashionable subjective philosophical view that all systems of thought are equally valid ways of structuring the universe. As Lucretius guessed, atoms are real and are not simply arbitrary constructs to explain the observations. Mathematics and computing have an important role in permitting long and sophisticated arguments to be carried through