Ultra-high-performance concrete (UHPC) is a type of cement-based composite for new construction and/or restoration of existing structures to increase service life. It is an innovative composite ...material that can be a suitable alternative to concrete structures exposed to aggressive conditions. After decades of research and development, a wide range of commercial UHPC compositions have been produced worldwide to cover a growing number of applications and a growing demand for high-quality construction materials. UHPC has significant advantages over regular concrete, but its use is limited due to limited design codes and prohibitive cost. Therefore, a comprehensive investigation of the durability characteristics of UHPC is essential to provide fundamental information for material testing requirements and procedures and expand its practical applications. Part I reviewed the developments, principles, and raw materials of the UHPFRC. Part II reviewed the hydration and microstructure of the UHPFRC. Part III reviewed the fresh and hardened properties of the UHPFRC. This Part IV covers the durability properties, cost assessment, applications, and challenges of the UHPFRC. Part V covers the mixture design, preparation, mixing, casting, and curing of the UHPFRC. This review is expected to advance the fundamental knowledge of UHPC and promote further research and applications of UHPC.
Recently, Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) has offered notable advantages over other types of concrete. Therefore, a comprehensive investigation of the latest developments in ...Ultra-High-Performance Concrete (UHPC) is necessary to provide essential information for materials testing requirements and procedures and to expand its practical applications. The present work is a comprehensive four-part review of the UHPFRC. The current first part of the review focuses attention on the developments, principles, and raw materials of the UHPFRC. Part II covers the hydration and microstructure of the UHPFRC. Part III reviewed the fresh and hardened properties of the UHPFRC. Part IV covers the durability properties, cost assessment, applications, and challenges of the UHPFRC. This review is expected to advance the fundamental knowledge of UHPC and promote further research and applications of UHPC.
Ultra-high-performance concrete (UHPC) refers to cement-based materials exhibiting a compressive strength higher than 150 MPa, high ductility, and excellent durability. Besides, over the last twenty ...years, remarkable advances have taken place in the research and application of Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC). Therefore, a comprehensive investigation of the durability characteristics of UHPC is essential to provide fundamental information for material testing requirements and procedures and expand its practical applications. Part I reviewed the developments, principles, and raw materials of the UHPFRC. This Part II covers the hydration and microstructure of the UHPFRC. Part III covers the fresh and hardened properties of the UHPFRC. Part IV covers the durability properties, cost assessment, applications, and challenges of the UHPFRC. This review is expected to advance the fundamental knowledge of UHPC and promote further research and applications of UHPC.
Ultra-high-performance concrete (UHPC) refers to cement-based materials exhibiting a compressive strength higher than 150 MPa, high ductility, and excellent durability. Besides, over the last twenty ...years, remarkable advances have taken place in the research and application of Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC). Therefore, a comprehensive investigation of the durability characteristics of UHPC is essential to provide fundamental information for material testing requirements and procedures and expand its practical applications. Part I reviewed the developments, principles, and raw materials of the UHPFRC. Part II reviewed the hydration and microstructure of the UHPFRC. This Part III covers the fresh and hardened properties of the UHPFRC. Part IV covers the durability properties, cost assessment, applications, and challenges of the UHPFRC. Part V covers the mixture design, preparation, mixing, casting, and curing of the UHPFRC. This review is expected to advance the fundamental knowledge of UHPC and promote further research and applications of UHPC.
Ultra-high-performance concrete (UHPC) is a cement-based composite used for new construction and/or the restoration of existing structures in order to extend their service life. It is a revolutionary ...composite material that can serve as a suitable substitute for concrete construction in hostile environments. After decades of research and development, a wide variety of commercial UHPC compositions have been created around the world to meet the expanding number of uses and demand for high-quality building materials. Although UHPC has significant advantages over conventional concrete, its application is limited due to restrictive design rules and high cost. Therefore, a careful review of the various properties of UHPC is necessary to offer key information for material testing criteria and methods and to broaden its practical uses. “Part I reviewed the developments, principles, and raw materials of the UHPFRC. Part II reviewed the hydration and microstructure of the UHPFRC. Part III reviewed the fresh and hardened properties of the UHPFRC. Part IV covers the durability properties, cost assessment, applications, and challenges of the UHPFRC. This Part V covers the mixture design, preparation, mixing, casting, and curing of the UHPFRC.” This review is anticipated to increase the fundamental understanding of UHPC and encourage additional study and applications of UHPC.
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•h-BP monolayer with vacancy, antisite and Stone–Wales defects were investigated.•Pristine and most defected h-BP are semiconductor, metallic and non-magnetic.•Boron vacancy induced ...ferromagnetic ordering in the host lattice.•Formation energy indicate that BP antisite is the most predominant defect type.
Using density functional theory (DFT), we systemically studied the impact of various point defects on the structural, magnetic and electronic properties of graphene-like boron phosphide (h-BP) monolayer. The results showed that the defect-free monolayer structure retained semiconductor-like the respective bulk compound, but the band gap modifies its character from indirect to direct. The band gaps of h-BP sheet varied from 0.142/0.46 to 0.75/1.26 eV using PBE/HSE06 schemes due to the existence of Stone-Wales (SW) and antisites defects. Also, it should be noted that the defect-free monolayer showed metallic behavior with a noticeable ferromagnetism, by hosting a boron vacancy, and becomes an indirect semiconductor through single (P) and double (P–B) vacancies. Additionally, the stability of the favorable point defects has been predicted based on the cohesive and formation energies. We have collected STM images of the SW defect structure for upcoming experimental observations. This study may be useful when designing novel optoelectronic and magnetic devices that employ defective h-BP monolayers.
Background
Surgical mortality data are collected routinely in high‐income countries, yet virtually no low‐ or middle‐income countries have outcome surveillance in place. The aim was prospectively to ...collect worldwide mortality data following emergency abdominal surgery, comparing findings across countries with a low, middle or high Human Development Index (HDI).
Methods
This was a prospective, multicentre, cohort study. Self‐selected hospitals performing emergency surgery submitted prespecified data for consecutive patients from at least one 2‐week interval during July to December 2014. Postoperative mortality was analysed by hierarchical multivariable logistic regression.
Results
Data were obtained for 10 745 patients from 357 centres in 58 countries; 6538 were from high‐, 2889 from middle‐ and 1318 from low‐HDI settings. The overall mortality rate was 1·6 per cent at 24 h (high 1·1 per cent, middle 1·9 per cent, low 3·4 per cent; P < 0·001), increasing to 5·4 per cent by 30 days (high 4·5 per cent, middle 6·0 per cent, low 8·6 per cent; P < 0·001). Of the 578 patients who died, 404 (69·9 per cent) did so between 24 h and 30 days following surgery (high 74·2 per cent, middle 68·8 per cent, low 60·5 per cent). After adjustment, 30‐day mortality remained higher in middle‐income (odds ratio (OR) 2·78, 95 per cent c.i. 1·84 to 4·20) and low‐income (OR 2·97, 1·84 to 4·81) countries. Surgical safety checklist use was less frequent in low‐ and middle‐income countries, but when used was associated with reduced mortality at 30 days.
Conclusion
Mortality is three times higher in low‐ compared with high‐HDI countries even when adjusted for prognostic factors. Patient safety factors may have an important role. Registration number: NCT02179112 (http://www.clinicaltrials.gov).
Higher in low‐income countries
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•Some Physical properties for BeO1−xAx alloys are investigated.•The calculated ground states properties for BeA compounds compare well with the available data.•Alloying BeO and BeX ...change the nature of band gap compared to the parent compounds.•The optical and the thermodynamic properties for are investigated for the first time.
Special quasi-random structure (SQS) was used to investigate the structural, electronic, and optical characteristics of the binary and ternary beryllium chalcogenide alloys. The computations were performed using the pseudopotential technique. The GGA-WC scheme was applied to study the structural and optical features of these present alloys, while the HSE06 hybrid functional was used to correct the underestimation of the electronic band structure. The optimized lattice constants and bulk modulus demonstrate a non-linear tendency with increasing x concentration. The phase transition may occur for all ternary alloys at x = 0.5 with the orthorhombic assumed crystal system. The ternary alloys of BeO1−xAx (A = S, Se) at 0.5 ⩽ x ⩽1 have an indirect band gap, while BeO1−xTex0.5 ⩽ x ⩽ 1 manifest a metallic demeanor using HSE06 formalism. The optical spectra were computed and discussed in detail. Furthermore, the thermodynamic stability of the studied compounds was examined using the miscibility critical temperature.
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•The observed reaction rate was modeled through separable kinetics.•Intrinsic heterogeneous Fenton-like reactions followed Langmuir-Hinshelwood kinetics.•Activity (a) and fouling ...species concentration (CF) described the catalyst decay.•Catalyst decay rate was 2nd order in a and 1st order in CF.•Model included rate constants, activation energies and adsorption constant and enthalpy.
One of the most crucial problems in catalysis is the loss of catalytic activity. When analyzing or designing a reactive system involving a decaying catalyst, a rate law adjusted for the catalyst deactivation should be utilized. An example of deactivating catalysts is supported-iron catalysts used in the heterogeneous Fenton-like oxidations of organic compounds. In this study, the observed reaction rate of such reactive systems was modeled – through separable kinetics – with a general rate expression that was written in terms of a rate law, describing the reaction kinetics on the fresh catalyst, and an activity term, accounting for the catalyst deactivation. The model was developed and verified for the catalytic wet peroxide oxidation of selected dyes (Reactive Yellow and Red) over Fe-Y zeolite and drugs (Diclofenac and Naproxen) over magnetite/multi-walled carbon nanotubes, which experienced notable deactivation during the reaction. It was found that the reaction rate followed Langmuir-Hinshelwood kinetics while the catalyst decay rate was second order in the present activity and first order in the concentration of the fouling species, which presumably resulted from the degradation of the organic compounds. The effect of the temperature on the rate expression parameters was also studied. The model included parameters such as the reaction and decaying rate constants, reaction and decaying activation energies, adsorption constant, and enthalpy of adsorption. The rate expression proved to satisfactorily describe the concentration–time trajectories in all the studied reactions despite their differences in the utilized catalysts, reacting organic compounds, and/or conditions, which verified the robustness of the model
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