Mixing Strength Research Articles

Sustainability and performance assessment of binary blended low-carbon concrete using supplementary cementitious materials

This study was carried out to apply low-carbon concrete at actual construction site. For this purpose, there was a necessity for the study that could be tested to adjust the water unit quantity to ensure the constructability as well as the sustainability and performance assessment of concrete according to the quality characteristics of local raw materials. For a designed compressive strength (fck) of 24 MPa, which is commonly applied to 29-story apartment structures, the compressive strength properties of binary blended low-carbon concrete were investigated for replacement with ground granulated blast-furnace slag (GGBS) and fly ash (FA). The results of the study were as follows: The compressive strength at 28 days for 5 and 20 °C was linearly reduced by approximately 1.7 and 0.9 MPa when the replacement ratio of GGBS increased by 10% and by 2.5 and 3.8 MPa when the FA replacement ratio increased by 10%, respectively. For a mixing strength of 32.5 MPa at 28 days under 20 °C, the GGBS and FA replacement ratios were below 39.7% and 16.6%, respectively. In terms of environmental effect, when the GGBS and FA replacement ratio increased by 10% each, the life cycle environmental impact of GGBS decreased by 0.6 US$, while FA decreased by 1.1 US$. Through this study, the compressive strength properties of binary blended low-carbon concrete were investigated according to the replacement ratios, and the applicable range of mixing proportions was derived. The results of this study are expected to be utilized as data for the commercialization of low-carbon concretes.

Design of multilayer microfluidic paper chip and its visual detection of pesticide residues

With the increase of China's grain production, the use of pesticides is gradually increasing. Traditional pesticide detection takes a long time and requires expensive experimental instruments, which is not conducive to the rapid and accurate detection of pesticide residues in the field. To solve this problem, this paper proposes a visual detection method of pesticide residues based on multi-layer microfluidic paper chips. The internal channel structure of paper chip is designed from the perspective of efficient mixing. Through the simulation of the mixed effect of three kinds of staggered channel structures, which are arc type, triangle type, and ladder type, the "ladder-type h-0.3, s-2.6" is selected as the best-staggered structure, and the mixing strength is 0.91534. The best simulation structure was tested by a colored reagent, and the image processing of 15 test results was carried out with MATLAB. The average mixing strength was 0.84, and the and the standard deviation was 0.022. The visual detection experiment of acetamiprid and profenofos in cabbage samples was carried out by using the device，The detection range of acetamiprid was 4~72 μg/kg, and the detection range of profenofos was 3~54 μg/kg . The recovery of acetamiprid was 75%~85%, and the recovery of profenofos was 80%~90%. The detection range and recovery rate indicate that the device has high repeatability and accuracy in the actual sample detection

Limits from the FUNK experiment on the mixing strength of hidden-photon dark matter in the visible and near-ultraviolet wavelength range

We present results from the FUNK experiment in the search for hidden-photon dark matter. Near the surface of a mirror, hidden photons may be converted into ordinary photons. These photons are emitted perpendicular to the surface and have an energy equal to the mass of the dark matter hidden photon. Our experimental setup consists of a large, spherical mirror with an area of more than 14 m$^2$, which concentrates the emitted photons into its central point. Using a detector sensitive to visible and near-UV photons, we can exclude a kinetic-mixing coupling of stronger than $\chi \approx 10^{-12}$ in the mass range of 2.5 to 7 eV, assuming hidden photons comprise all of the dark matter. The experimental setup and analysis used to obtain this limit are discussed in detail.

Unified approach to characterize the strength of cement stabilized macadam subjected to different loading modes

Cement stabilized macadam base is the primary stress diffusion and bearing layer of semi-rigid asphalt pavement, therefore its mechanical behavior directly affects pavement performance. The indirect tensile strength, unconfined compressive strength, and bending strength are the essential parameters for evaluating the bearing capacity of cement stabilized macadam. In the design of a pavement structure, the conventional mixing strength values of a test sample are analyzed and calculated at a fixed loading rate. By using this procedure, the influence of the mixing method and the different loading rates on the strength values are ignored. Besides, the strength obtained by using the fixed loading rate with different loading modes has significant differences. As a result, the artificial randomness of the strength parameter in the design of a semi-rigid asphalt pavement structure increases. In an attempt, to improve the effectiveness and completeness of the strength parameters of cement stabilized macadam under different loading modes, mechanical tests were conducted on samples prepared with both vibration mixing and conventional mixing methods. This procedure included, indirect tensile strength test, unconfined compressive strength test, and four-point bending strength test under different loading rates. The results of these strength tests each group of samples (vibration and conventional mixing method) were compared. Besides, all samples were subjected to 6 different loading rates when conducting each loading mode. These experimental values were analyzed. The loading rate and the strength value have a power function relationship and the correlation of strength rates was revealed. The results demonstrated that the vibration mixing method increases the indirect tensile strength, unconfined compressive strength, and four-point bending strength by 13%, 14%, and 10%, respectively. A unified strength model (S/S0 = 0.9841 + 0.16856ln (0.01019 + v/v0) under two mixing methods and various loading modes were established by using the variation between loading rate ratio and strength ratio. In the unified model, the strength under vibration mixing and conventional mixing methods, and the strength among different loading rates can be converted, which improved the test efficiency. The established unified model solves the problem of uncertainty and uniqueness of strength parameters under different loading modes. The accuracy of the semi-rigid asphalt pavement structure resistance design was effectively improved, thereby providing theoretical guidance for the construction of semi-rigid base asphalt pavement engineering.

North Pacific Upper-Ocean Cold Temperature Biases in CMIP6 Simulations and the Role of Regional Vertical Mixing

AbstractSubstantial model biases are still prominent even in the latest CMIP6 simulations; attributing their causes is defined as one of the three main scientific questions addressed in CMIP6. In this paper, cold temperature biases in the North Pacific subtropics are investigated using simulations from the newly released CMIP6 models, together with other related modeling products. In addition, ocean-only sensitivity experiments are performed to characterize the biases, with a focus on the role of oceanic vertical mixing schemes. Based on the Argo-derived diffusivity, idealized vertical diffusivity fields are designed to mimic the seasonality of vertical mixing in this region, and are employed in ocean-only simulations to test the sensitivity of this cold bias to oceanic vertical mixing. It is demonstrated that the cold temperature biases can be reduced when the mixing strength is enhanced within and beneath the surface boundary layer. Additionally, the temperature simulations are rather sensitive to the parameterization of static instability, and the cold biases can be reduced when the vertical diffusivity for convection is increased. These indicate that the cold temperature biases in the North Pacific can be largely attributed to biases in oceanic vertical mixing within ocean-only simulations, which likely contribute to the even larger biases seen in coupled simulations. This study therefore highlights the need for improved oceanic vertical mixing in order to reduce these persistent cold temperature biases seen across several CMIP models.

Observations of Disequilibrium CO Chemistry in the Coldest Brown Dwarfs

Abstract Cold brown dwarfs are excellent analogs of widely separated, gas giant exoplanets, and provide insight into the potential atmospheric chemistry and physics we may encounter in objects to be discovered by future direct imaging surveys. We present a low-resolution, R ∼ 300, M-band spectroscopic sequence of seven brown dwarfs with effective temperatures between 750 and 250 K along with Jupiter. These spectra reveal disequilibrium abundances of carbon monoxide (CO) produced by atmospheric quenching. We use the eddy diffusion coefficient (K zz ) to estimate the strength of vertical mixing in each object. The K zz values of cooler gaseous objects are close to their theoretical maximum, and warmer objects show weaker mixing, likely due to less efficient convective mixing in primarily radiative layers. The CO-derived K zz values imply that disequilibrium phosphine (PH3) should be easily observable in all of the brown dwarfs, but none as yet show any evidence for PH3 absorption. We find that ammonia is relatively insensitive to atmospheric quenching at these effective temperatures. We are able to improve the fit to WISE 0855's M-band spectrum by including both CO and water clouds in the atmospheric model.

Improved limits on a hypothetical X(16.7) boson and a dark photon decaying into e+e− pairs

The improved results on a direct search for a new X(16.7 MeV) boson which could explain the anomalous excess of $e^+e^-$ pairs observed in the excited 8Be nucleus decays ("Berillium anomaly") are reported. Due to its coupling to electrons, the X boson could be produced in the bremsstrahlung reaction e-Z -> e-ZX by a high-energy beam of electrons incident on active target in the NA64 experiment at the CERN SPS and observed through its subsequent decay into $e^+e^-$ pair. No evidence for such decays was found from the combined analysis of the data samples with total statistics corresponding to 8.4\times 10^{10} electrons on target collected in 2017 and 2018. This allows to set the new limits on the $X$--$e^-$ coupling in the range 1.2 \times 10^{-4} < \epsilon_e < 6.8 \times 10^{-4}, excluding part of the parameter space favored by the Berillium anomaly. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay $A' \to e^+e^-$ of the bremsstrahlung A' with a mass below 24 MeV.

New Bounds from Positronium Decays on Massless Mirror Dark Photons.

We present the results of a search for a hidden mirror sector in positronium decays with a sensitivity comparable with the bounds set by the prediction of the primordial He^{4} abundance from big bang nucleosynthesis. No excess of events compatible with decays into the dark sector is observed, resulting in an upper limit for the branching ratio of this process of 3.0×10^{-5} (90%C.L.). This is an order of magnitude more stringent than the current existing laboratory bounds and it constrains the mixing strength of ordinary photons to dark mirror photons at a level of ϵ<5.0×10^{-8}.

Development and optimization of complex coacervates based on zedo gum, cress seed gum and gelatin

The complexation mechanism of zedo gum and cress seed gum as nutraceutical polysaccharides with gelatin (type-A and type-B) was investigated as a function of pH, Protein to polysaccharide mixing ratio and ionic strength. Turbidity measurements were performed to achieve optimum reaction conditions. Furthermore, Zeta potential measurements along with measuring complex coacervation yield were carried out to support the turbidity results. The state diagrams representing complex coacervation formation limits were obtained for each system. FTIR analysis was performed on resulted complex coacervates which confirmed the molecular interactions between each gum and gelatin. Also, the coacervate phase of the suspensions showed shear-thinning behavior according to steady-state flows and represented higher values of storage moduli at lower frequencies in frequency sweep measurements. All systems which are assessed in this study have the potential to form particles, however, the one containing gelatin type-A had better performance in terms of pH stability.

Probing invisible decay of a dark photon at BESIII and a future Super Tau Charm Factory via monophoton searches

We propose to search the monophoton events at the BESIII detector and future Super Tau Charm Factory to probe the sub-GeV dark photon decay into lighter dark matter. We compute the cross section due to the dark photon associated a standard model photon production, and study the corresponding standard model irreducible/reducible backgrounds. By using the data about 17 fb$^{-1}$ collected at the BESIII detector since 2011, we derive new leading limits of the mixing strength $\varepsilon$, $\varepsilon\lesssim(1.1-1.6)\times 10^{-4}$, in the mass range of 0.04 GeV $\lesssim m_{A^\prime} \lesssim$ 3 GeV. With 30 ab$^{-1}$ data, STCF running at $\sqrt{s} = 2$ GeV, can probe $\varepsilon$ down to 5.1$\times 10^{-6}$ when $m_{A^\prime}=1$ GeV. For models of scalar and fermionic light thermal dark matter production via dark photon, we present the constrains on the dimensionless dark matter parameter $y=\varepsilon^2\alpha_D(m_\chi/m_{A^\prime})^4$ as function of the DM mass $m_{\chi}$ at BESIII and future STCF, conventionally assuming the dark coupling constant $\alpha_D=0.5$ and $m_{A^\prime}=3 m_{\chi}$. We find that BESIII can exclude model of scalar, Majorana, and pseudo-Dirac (with a small splitting) DM for the mass region 0.03$\sim$1 GeV, 0.04$\sim$1 GeV and 0.4$\sim$1 GeV respectively. For values $\alpha_D\lesssim 0.005$, combining the results from 2 GeV STCF with 30 ab$^{-1}$ data and BaBar, one can exclude the above three DM models in the mass region 0.001 GeV $\lesssim m_{\chi} \lesssim$ 1 GeV.

Unsymmetrical Bis-Alkynyl Complexes Based on Co(III)(cyclam): Synthesis, Ultrafast Charge Separation, and Analysis.

Donor-bridge-acceptor (D-B-A) systems with a polarizable bridge can afford rapid photoinduced electron transfer dynamics that may be susceptible to rate modulation by infrared excitation. We describe the synthesis, characterization, and electronic structure of a class of readily assembled D-B-A structures linked by a cobalt cyclam bridge. The reaction between [Co(cyclam)Cl2]Cl and 4-ethynyl-N-isopropyl-1,8-naphthalimide (HC2NAPiPr) yields [Co(cyclam)(C2NAPiPr)Cl]Cl (1), which reacts with LiC2Y at -78 °C to afford [Co(cyclam)(C2NAPiPr)(C2D)]Cl with D as C6H4-4-NMe2 (2a), NAPiPr (2b), Ph (2c), and C6H4-4-N(4-MeOPh)2 (2d). Molecular structures of 1 and 2a were established using single-crystal X-ray diffraction, while the redox properties and fluorescence profiles of compounds 1 and 2 were examined using voltammetric and steady-state emission techniques, respectively. The electronic structures and photophysical properties of these compounds were studied using density functional theory and time-dependent density functional theory methods. The excited-state dynamics of compounds 1, 2a, and 2d were explored using femtosecond transient absorption spectroscopy with 400 nm excitation and detection in both the visible and mid-IR spectral regions. Formation of a long-lived excited state was complete within 20 ps of excitation in all three compounds. Ultrafast spectral changes observed in 2a and 2d within the first 20 ps indicated the formation of a charge separated state (CS state, D+-B-A-) with characteristic times of less than 0.1 and 0.25 ps, respectively. The CS state undergoes rapid charge recombination (8 ps in 2a and 4 ps in 2d). The CS dynamics is facilitated by the Co center, which mixes the bright NAP-centered electronic state with a pure CS state. The mixing strength depends on the donor energetics and conformation, which significantly influences the charge transfer dynamics in 2a and 2d.

Dark Matter Search in Missing Energy Events with NA64.

A search for sub-GeV dark matter production mediated by a new vector boson A^{'}, called a dark photon, is performed by the NA64 experiment in missing energy events from 100GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with 2.84×10^{11} electrons on target no evidence of such a process has been found. The most stringent constraints on the A^{'} mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range ≲0.2 GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search.

Neutron oscillations for solving neutron lifetime and dark matter puzzles

A model of n−n′ (neutron-mirror neutron) oscillations is proposed under the framework of the mirror matter theory with slightly broken mirror symmetry. It resolves the neutron lifetime discrepancy, i.e., the 1% difference in neutron lifetime between measurements from “beam” and “bottle” experiments. In consideration of the early universe evolution, the n−n′ mass difference is determined to be about 2×10−6 eV/c2 with the n−n′ mixing strength of about 2×10−5. The picture of how the mirror-to-ordinary matter density ratio is evolved in the early universe into the observed dark-to-baryon matter density ratio of about 5.4 is presented. Reanalysis of previous data and new experiments that can be carried out under current technology are discussed and recommended to test this proposed model. Other consequences of the model on astrophysics and possible oscillations of other neutral particles are discussed as well.

Influence of initial conditions on absolute and relative dispersion in semi-enclosed basins.

Absolute and relative dispersion are fundamental quantities employed in order to assess the mixing strength of a basin. There exists a time scale called Lagrangian Integral Scale associated to absolute dispersion that highlights the occurrence of the transition from a quadratic dependence on time to a linear dependence on time. Such a time scale is commonly adopted as an indicator of the duration needed to lose the influence of the initial conditions. This work aims to show that in a semi-enclosed basin the choice of the formulation in order to calculate the absolute dispersion can lead to different results. Moreover, the influence of initial conditions can persist beyond the Lagrangian Integral Scale. Such an influence can be appreciated by evaluating absolute and relative dispersion recursively by changing the initial conditions. Furthermore, finite-size Lyapunov exponents characterize the different regimes of the basin.

PetitRADTRANS

We present the easy-to-use, publicly available, Python package petitRADTRANS, built for the spectral characterization of exoplanet atmospheres. The code is fast, accurate, and versatile; it can calculate both transmission and emission spectra within a few seconds at low resolution (λ/Δλ = 1000; correlated-k method) and high resolution (λ/Δλ = 106; line-by-line method), using only a few lines of input instruction. The somewhat slower, correlated-k method is used at low resolution because it is more accurate than methods such as opacity sampling. Clouds can be included and treated using wavelength-dependent power law opacities, or by using optical constants of real condensates, specifying either the cloud particle size, or the atmospheric mixing and particle settling strength. Opacities of amorphous or crystalline, spherical or irregularly-shaped cloud particles are available. The line opacity database spans temperatures between 80 and 3000 K, allowing to model fluxes of objects such as terrestrial planets, super-Earths, Neptunes, or hot Jupiters, if their atmospheres are hydrogen-dominated. Higher temperature points and species will be added in the future, allowing to also model the class of ultra hot-Jupiters, with equilibrium temperatures Teq ≳ 2000 K. Radiative transfer results were tested by cross-verifying the low- and high-resolution implementation of petitRADTRANS, and benchmarked with the petitCODE, which itself is also benchmarked to the ATMO and Exo-REM codes. We successfully carried out test retrievals of synthetic JWST emission and transmission spectra (for the hot Jupiter TrES-4b, which has a Teq of ∼1800 K).

Bounds on ultralight hidden-photon dark matter from observation of the 21 cm signal at cosmic dawn

Ultra-light hidden-photon dark matter produces an oscillating electric field in the early Universe plasma, which in turn induces an electric current in its ionized component whose dissipation results in heat transfer from the dark matter to the plasma. This will affect the global 21cm signal from the Dark Ages and Cosmic Dawn. In this work we focus on the latter, in light of the reported detection by the EDGES collaboration of an absorption signal at frequencies corresponding to redshift z~17. By measuring the 21cm global signal, a limit can be placed on the amount of gas heating, and thus the kinetic mixing strength $\varepsilon$ between the hidden and ordinary photons can be constrained. Our inferred 21cm bounds on $\varepsilon$ in the mass range $10^{-23}\,{\rm eV}\lesssim m_\chi\lesssim10^{-13}\,{\rm eV}$ are the strongest to date.

Finite Element Analysis and Influence Factors of Flexural Behavior of HFRP Reinforced Concrete Beams

HFRP (Hybrid Fiber Reinforced Plastics) ribs are a new type of composite rib made of a mixture of two or more continuous reinforcing fibers. Since the HFRP ribs have a "pseudo-yield" phase similar to that of steel bars, the mechanical properties of HFRP reinforced concrete structures are quite different from those of single FRP reinforced concrete, and should be studied in depth. In this paper, the finite element analysis of the hybrid effect of HFRP bars and the flexural behaviour of HFRP reinforced concrete beams is carried out. The ANSYS finite element analysis software is used to simulate the bending test of carbon/glass HFRP reinforced concrete beams with three different hybrid ratios. The calculation results are compared with the experimental results, and the rationality of the finite element model is verified. On this basis, the influence of mixing ratio, reinforcement ratio and concrete strength on the deflection of concrete beams is further analysed.

The Interaction Between Boundary Layer and Convection Schemes in a WRF Simulation of Post Cold Frontal Clouds Over the ARM East North Atlantic Site

AbstractThe correct representation of low‐level midlatitude clouds found in the wake of cold fronts strongly relies on the representation of planetary boundary layer (PBL) and convection processes, which are typically parameterized separately in numerical models. Using the Weather Research and Forecasting Model (WRF), this study investigates how distinct pairs of PBL and convection parameterization schemes represent cloud fraction in the post cold frontal region. The simulations focus on the region of the Department of Energy Atmospheric Radiation Measurement (ARM) Eastern North Atlantic observation site in the Azores Islands in the wake of a cold front that passed on 25 December 2015. Different PBL and convection schemes are combined to create 12 distinct configurations. The main differences between the selected physical parameterizations are the strength of vertical mixing and the entrainment. The simulations produce a wide range of cloud fractions, where some configurations significantly underestimate while others clearly overestimate satellite and surface‐based estimates of cloud fraction. A skill score is used to quantitatively assess the performance of each configuration with respect to ground‐based radar data. The key processes that are found to significantly impact the cloud fraction distribution are the strength of the PBL decoupling, the vertical wind shear, entrainment and detrainment rates in shallow convection, and the occurrence of drizzle. This indicates that to successfully simulate post cold frontal clouds, modeled physics must balance strong internal vertical mixing and weak exchange with the free troposphere. For this case study, cloud fraction was more sensitive to the choice of convection scheme than PBL scheme.

Dependence of convective boundary mixing on boundary properties and turbulence strength

Convective boundary mixing is one of the major uncertainties in stellar evolution. In order to study its dependence on boundary properties and turbulence strength in a controlled way, we computed a series of 3D hydrodynamical simulations of stellar convection during carbon burning with a varying boosting factor of the driving luminosity. Our 3D implicit large eddy simulations were computed with the PROMPI code. We performed a mean field analysis of the simulations within the Reynolds-averaged Navier-Stokes framework. Both the vertical RMS velocity within the convective region and the bulk Richardson number of the boundaries are found to scale with the driving luminosity as expected from theory. The positions of the convective boundaries were estimated through the composition profiles across them, and the strength of convective boundary mixing was determined by analysing the boundaries within the framework of the entrainment law. We find that the entrainment is approximately inversely proportional to the bulk Richardson number. Although the entrainment law does not encompass all the processes occurring at boundaries, our results support the use of the entrainment law to describe convective boundary mixing in 1D models, at least for the advanced phases. The next steps and challenges ahead are also discussed.

Optimization of Temperatures of Hashing Asphaltic Concrete Mixes Taking into Account the Structural Type of Bitumen

Researches by definition of optimum temperatures at hashing asphaltic concrete mixes on bitumens of different structural types with application of a method of mathematical designing of experiments are presented. Varied factors at manufacturing asphaltic concrete mixes were an index of a penetration of bitumen as the characteristic of a structural type of bitumen, the maintenance of bitumen and temperature of hashing of mixes. Processing of results of experiment is executed with application of computer technologies by means of a package of applied programs Maple. Mathematical models of physicomechanical properties of asphaltic concretes in the form of the equations the regressions reflective link between investigated properties of asphaltic concretes and varied factors are received. It is determined that at reduction of an index of a penetration and a rise of temperature of mixing strength of an asphaltic concrete increases. At a rise of temperature of hashing and increas asphalt content in mixes the water-resistance of an asphaltic concrete increases. On extreme dependences of indicators of durability at a tensioning and a tension in bending from hashing temperature optimum temperatures of hashing asphaltic concrete mixes are defined. It is established that optimum temperatures of hashing depends on an index of a penetration of bitumen and raise at its reduction.