QUANTIFYING THE EFFECT OF CONSTRUCTION SITE FACTORS ON CONCRETE QUALITY, COSTS AND PRODUCTION RATES

Factors affecting concrete can be categorized as structured factors or unstructured factors. The first group of factors consists of those related to the production process of concrete including water-cement ratio, properties of raw materials and mix proportions. Unstructured factors or construction site factors are related to labor skills and local conditions during the construction process of a project. Concrete compressive strength as a quality metric, costs and production rates may be affected significantly by such factors while performing concrete operations at the jobsite. Several prior studies have investigated the effect of structured factors on concrete. However literature is limited regarding the effects of unstructured factors during the construction phase of a facility. This study proposes a systematic methodology to identify and quantify the effects of construction site factors including crew experience, compaction method, mixing time, curing humidity and curing temperature on concrete quality, costs and production rates using fuzzy inference systems. First, the perceived importance of construction-related factors is identified and evaluated through literature review and a survey deployed to construction experts. Then, the theory of design of experiments (DOE) is used to conduct a full 25 factorial experiment consisting of 32 runs and 192 compressive strength tests to identify statistically significant unstructured factors. Fuzzy inference systems (FISs) are proposed for predicting concrete compressive strength, costs and production rate effects through the use of adapted network-based fuzzy inference system (ANFIS). Finally, an optimization model is formulated and tested for managing concrete during the construction process of a facility. Literature review and survey results showed that curing humidity, crew experience, and compaction method are the top three factors perceived by construction experts to affect concrete compressive strength, whereas crew experience, mixing time and compaction method are the top three factors affecting concrete costs and production rates. Additionally, crew experience, compaction and mixing time were found to dominate global ranking of perceived affecting factors through the application of the relative importance index (RII). When conducting designed experiments and analysis of variance (ANOVA), compaction method, mixing time, curing humidity and curing temperature were identified to be statistically significant construction site factors for concrete compressive strength whereas crew experience, compaction method and mixing time were statistically significant factors for cost and production rates. A Sugeno type fuzzy inference system (FIS) for quantifying compressive strength, cost and production rate effects was created by using ANFIS, having correlation coefficients (R-squared values) greater than 93%, indicating that resulting models predict new observations well. Curing temperature (i.e., on-site curing temperature) was identified to be the most affecting condition for concrete compressive strength while mixing time had the biggest impact on concrete cost and production rates. The developed FISs can be used as a decision–support tool that allows for determining desired operating conditions, that ensures specified compressive strength, saves resources and maximizes profits when fabricating, placing and curing concrete

Generalized hydrodynamics of a dilute finite-sized particles suspension: Dynamic viscosity

We present a mesoscopic hydrodynamic description of the dynamics of colloidal suspensions. We consider the system as a gas of Brownian particles suspended in a Newtonian heat bath subjected to stationary non-equilibrium conditions imposed by a velocity field. Using results already obtained in previous studies in the field by means of a generalized Fokker-Planck equation, we obtain a set of coupled differential equations for the local diffusion current and the evolution of the total stress tensor. We find that the dynamic shear viscosity of the system contains contributions arising from the finite size of the particles.Comment: To appear in Physical Review

Physiological effects of different oxygen flow rates and ambient temperatures on pressure-suited subjects performing work at altitude

Physiological effects of oxygen flow rates and ambient temperatures on pressure-suited subjects performing work in altitude chambe

Searching for numerically-simulated signals of black hole binaries with a phenomenological template family

Recent progress in numerical relativity now allows computation of the binary black hole merger, whereas post-Newtonian and perturbative techniques can be used to model the inspiral and ringdown phases. So far, most gravitational-wave searches have made use of various post-Newtonian-inspired templates to search for signals arising from the coalescence of compact binary objects. Ajith et al have produced hybrid waveforms for non-spinning binary black-hole systems which include the three stages of the coalescence process, and constructed from them phenomenological templates which capture the features of these waveforms in a parametrized form. As a first step towards extending the present inspiral searches to higher-mass binary black-hole systems, we have used these phenomenological waveforms in a search for numerically-simulated signals injected into synthetic LIGO data as part of the NINJA project

Gas-solid contactors and catalytic reactors with direct microwave heating: current status and perspectives

Microwave heating (MWH) transforms energy from an electromagnetic wave to heat. In contrast to conventional heating (CH) mechanisms that use slower heat transfer processes via conduction, convection or radiation, microwaves (MW) directly interact with MW susceptor materials and induce a rapid conversion of the electromagnetic energy into heat. This rapid heating provides MWH with distinct features that can be leveraged to increase conversion, selectivity and/or energy efficiency of chemical processes. Here we discuss recent significant advances reported in MWH processes involving gas-solid interactions. Special attention is devoted to key aspects such as the methodologies to accurately determine local temperatures under the influence of electromagnetic (EM). Other relevant aspects such as the consideration of the solid catalyst dielectric properties or the design of novel gas-solid contactor configurations will be discussed. Emerging aspects such as the potential of MWH to minimize secondary by-products in high temperature reactions or to efficiently perform in transient processes, e.g. adsorption-desorption cycles, are highlighted. Finally, current challenges and perspectives towards a wide application of MWH in gas solid contactors will be critically discussed

UAS pilot support for departure, approach and airfield operations

Unmanned Aerial Systems (UAS) have great potential to be used in a wide variety of civil applications such as environmental applications, emergency situations, surveillance tasks and more. The development of Flight Control Systems (FCS) coupled with the availability of other Commercial Off-The Shelf (COTS) components is enabling the introduction of UAS into the civil market. The sophistication of existing FCS is also making these systems accessible to end users with little aeronautics expertise. However, much work remains to be done to deliver systems that can be properly integrated in standard aeronautical procedures used by manned aviation

Single phase microreactor for the continuous, high-temperature synthesis of <4¿nm superparamagnetic iron oxide nanoparticles

The reproducibility of key nanomaterial features is essential in nanomedicine applications where small changes of physical characteristics often lead to a very different behavior. In this regard, continuous microreactors are often advocated as a means to achieve highly precise synthesis of nanomaterials. However, when the synthesis must take place at high temperatures the use of these devices becomes restricted in terms of materials and practical problems (e.g. plugging of microchannels). Here we present the continuous synthesis of ultrasmall superparamagnetic iron oxide nanoparticles (SPIONs) through a polyol-based process at high temperatures (>200 °C). The microfluidic reactor designed allows SPION production at residence times under 1 min, was able to work continuously for 8 h without channel blockage and reached high production yields by coupling microreactors using stacked plates. The effect of operating conditions was optimized to produce homogeneous particles with a narrow particle size distribution. In summary, the microreactor developed in this work enables easy-to scale up, reproducible continuous production of SPIONs

Laser induced fluorescence for axion dark matter detection: a feasibility study in YLiF4_4:Er3+^{3+}

We present a detection scheme to search for QCD axion dark matter, that is based on a direct interaction between axions and electrons explicitly predicted by DFSZ axion models. The local axion dark matter field shall drive transitions between Zeeman-split atomic levels separated by the axion rest mass energy $m_a c^2$. Axion-related excitations are then detected with an upconversion scheme involving a pump laser that converts the absorbed axion energy ($\sim$ hundreds of $\mu$eV) to visible or infrared photons, where single photon detection is an established technique. The proposed scheme involves rare-earth ions doped into solid-state crystalline materials, and the optical transitions take place between energy levels of $4f^N$ electron configuration. Beyond discussing theoretical aspects and requirements to achieve a cosmologically relevant sensitivity, especially in terms of spectroscopic material properties, we experimentally investigate backgrounds due to the pump laser at temperatures in the range $1.9-4.2$ K. Our results rule out excitation of the upper Zeeman component of the ground state by laser-related heating effects, and are of some help in optimizing activated material parameters to suppress the multiphonon-assisted Stokes fluorescence.Comment: 8 pages, 5 figure