scholarly journals Effect of Sodium Hexametaphosphate and Trisodium Phosphate on Dispersion of Polycarboxylate Superplasticizer

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4190
Author(s):  
Yan Zhang ◽  
Huaqing Liu ◽  
Jialong Liu ◽  
Ruiming Tong
Keyword(s):  
Adsorption Layer ◽  
Cement Hydration ◽  
Layer Structure ◽  
Free Water ◽  
Single Layer ◽  
Trisodium Phosphate ◽  
Sodium Hexametaphosphate ◽  
Polycarboxylate Superplasticizer ◽  
Dispersion Capacity ◽  
The Difference

Enhancement in dispersion of polycarboxylate superplasticizer (PCE) could be obtained by incorporating retarders in normal concrete. The generally believed reason was that the consumption of free water and polymer at the beginning was reduced by retarding cement hydration. This theory could not convincingly explain why sodium hexametaphosphate (SHMP) was able to promote the dispersion capacity of PCE, while trisodium phosphate (TSP) could not, despite that both TSP and SHMP could obviously retard the cement hydration. The adsorption behavior of PCE and phosphate was investigated and the mechanism was analyzed in order to gain deeper understanding. The results showed that TSP and SHMP delayed the cement hydration, impeded adsorption process of PCE, and increased thickness of adsorption layer. It was interesting that TSP reduced the dispersion, but SHMP enhanced. The reason for this contradiction was due to the difference in composition of adsorption layer. In the PCE-TSP system, this layer was composed of the precipitates (formed by TSP and Ca2+) and the invalided PCE (caused by these precipitates in the immediate vicinity of the cement grains); the invalided PCE was due to the decrease of PCE dispersion. In the PCE-SHMP system, “Inner-phosphate (multi-layers) + Outer-PCE (single layer)” structure was formed to make the PCE work more effective, hence enhancing the dispersion. These results were expected to be useful for the design of highly efficient dispersants.

scholarly journals A HfO2/SiTe Based Dual-Layer Selector Device with Minor Threshold Voltage Variation

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 408 ◽  
Author(s):  
Bing Song ◽  
Rongrong Cao ◽  
Hui Xu ◽  
Sen Liu ◽  
Haijun Liu ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Threshold Voltage ◽  
Layer Structure ◽  
Single Layer ◽  
Good Control ◽  
Filament Formation ◽  
Practical Application ◽  
Programmable Metallization Cell ◽  
Voltage Variation ◽  
The Difference

Volatile programmable metallization cell is a promising threshold switching selector with excellent characteristics and simple structures. However, the large variation of threshold voltage is a major problem for practical application. In this work, we propose a dual-layer structure to increase selectivity and improve the threshold voltage variation. Compared to single-layer devices, this dual-layer device exhibits higher selectivity (>107) and better threshold voltage uniformity with less than 5% fluctuation during 200 DC switching. The improvement is attributed to good control on the location of the filament formation and rupture after introducing a HfO2 layer. It is deduced that a major factor consists of the difference of Ag ions mobility between SiTe and HfO2 due to the grain boundary quantity.

Effects of Varying Geometrical Parameters on Boiling From Microfabricated Enhanced Structures

2003 ◽  
Vol 125 (1) ◽  
pp. 103-109 ◽  
Author(s):  
C. Ramaswamy ◽  
Y. Joshi ◽  
W. Nakayama ◽  
W. B. Johnson
Keyword(s):  
Heat Dissipation ◽  
Layer Structure ◽  
Single Layer ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Small Range ◽  
Two Phase ◽  
Wall Superheat

The current study involves two-phase cooling from enhanced structures whose dimensions have been changed systematically using microfabrication techniques. The aim is to optimize the dimensions to maximize the heat transfer. The enhanced structure used in this study consists of a stacked network of interconnecting channels making it highly porous. The effect of varying the pore size, pitch and height on the boiling performance was studied, with fluorocarbon FC-72 as the working fluid. While most of the previous studies on the mechanism of enhanced nucleate boiling have focused on a small range of wall superheats (0–4 K), the present study covers a wider range (as high as 30 K). A larger pore and smaller pitch resulted in higher heat dissipation at all heat fluxes. The effect of stacking multiple layers showed a proportional increase in heat dissipation (with additional layers) in a certain range of wall superheat values only. In the wall superheat range 8–13 K, no appreciable difference was observed between a single layer structure and a three layer structure. A fin effect combined with change in the boiling phenomenon within the sub-surface layers is proposed to explain this effect.

scholarly journals The Simulation Design of Microwave Absorption Performance for the Multi-Layered Carbon-Based Nanocomposites Using Intelligent Optimization Algorithm

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1951
Author(s):  
Danfeng Zhang ◽  
Congai Han ◽  
Haiyan Zhang ◽  
Bi Zeng ◽  
Yun Zheng ◽  
...  
Keyword(s):  
Layer Structure ◽  
Optimal Solution ◽  
Single Layer ◽  
Simulation Design ◽  
Wide Bandwidth ◽  
Abc Algorithm ◽  
Bee Colony ◽  
Absorbing Material ◽  
Important Means ◽  
Carbon Based

The optimal design objectives of the microwave absorbing (MA) materials are high absorption, wide bandwidth, light weight and thin thickness. However, it is difficult for single-layer MA materials to meet all of these requirements. Constructing multi-layer structure absorbing coating is an important means to improve performance of MA materials. The carbon-based nanocomposites are excellent MA materials. In this paper, genetic algorithm (GA) and artificial bee colony algorithm (ABC) are used to optimize the design of multi-layer materials. We selected ten kinds of materials to construct the multi-layer absorbing material and optimize the performance. Two algorithms were applied to optimize the two-layer MA material with a total thickness of 3 mm, and it was found that the optimal bandwidth was 8.12 GHz and reflectivity was −53.4 dB. When three layers of MA material with the same thickness are optimized, the ultra-wide bandwidth was 10.6 GHz and ultra-high reflectivity was −84.86 dB. The bandwidth and reflectivity of the optimized material are better than the single-layer material without optimization. Comparing the GA and the ABC algorithm, the ABC algorithm can obtain the optimal solution in the shortest time and highest efficiency. At present, no such results have been reported.

Free Water Influence on the Dynamic Tensile Behaviour of Concrete

2011 ◽  
Vol 82 ◽  
pp. 45-50 ◽  
Author(s):  
Benjamin Erzar ◽  
Pascal Forquin
Keyword(s):  
Dynamic Behaviour ◽  
Free Water ◽  
Dynamic Strength ◽  
Fragmentation Process ◽  
Tensile Behaviour ◽  
Water Influence ◽  
Micro Cracks ◽  
The World ◽  
The Difference ◽  
Impact Experiments

Concrete is a material used all over the world for civil engineering but the mechanisms governing its dynamic behaviour are still not well understood. In this work, spalling tests and edge-on impact experiments have been used to determine the influence of the free-water contained in pores and micro-cracks on the dynamic strength and on the fragmentation process. Moreover, spalling tests have been also used to identify the main mechanisms leading to the difference of behaviour observed between wet and dry concrete.

Characterization of multi- and single-layer structure SAW sensor

2006 ◽  
Author(s):  
S. Ahmadi ◽  
F. Hassani ◽  
C. Korman ◽  
M. Rahaman ◽  
M. Zaghloul
Keyword(s):  
Layer Structure ◽  
Single Layer ◽  
Saw Sensor

Shape-driven control of layer height in robotic wire and arc additive manufacturing

2019 ◽  
Vol 25 (10) ◽  
pp. 1637-1646 ◽  
Author(s):  
Bohao Xu ◽  
Xiaodong Tan ◽  
Xizhi Gu ◽  
Donghong Ding ◽  
Yuelin Deng ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Deposition Rate ◽  
Control Method ◽  
Single Layer ◽  
Optimization Method ◽  
Content Type ◽  
Layer Height ◽  
Layer Deposition ◽  
Complex Shapes ◽  
The Difference

Purpose Once an uneven substrate is aligned, traditional control theories and methods can be used on it, so aligning is of great significance for the development of wire and arc additive manufacturing (WAAM). This paper aims to propose a shape-driven control method for aligning a substrate with slopes to expand the application of WAAM. Design/methodology/approach A substrate with slopes must be aligned by depositing weld beads with slopes. First, considering the large height differences of slopes, multi-layer deposition is needed, and the number of layer of weld beads must be ascertained. Second, the change in the deposition rate is controlled as a ramp function to generate weld beads with slopes. Third, the variation of the deposition rate must be fine-tuned to compensate for the deviation between the actual and theoretical layer heights at the deposition of each layer. Finally, the parameters of the ramp functions at the deposition of each layer are determined through an optimization method. Findings First, to model the response function of layer height to deposition rate, the experiments are conducted with the deposition rate jumping from 4 to 8 mm/s and from 8 to 4 mm/s. When the deposition rate jumps from 4 to 8 mm/s and from 8 to 4 mm/s, the difference in the height of each layer decreases as the number of layer increases. Second, the variation of the deposition rate can be fine-tuned based on the deviation between the measured and theoretical layer heights because the variation of the deposition rate is proportional to the layer height when the initial and end deposition rates are near 4 or 8 mm/s, respectively. Third, the experimental results demonstrate that the proposed method is effective for single-layer aligning and aligning a substrate with one or more slopes. Originality/value The proposed method can expand the application of WAAM to an uneven substrate with slopes and lays the foundation for aligning tasks focused on uneven substrates with more complex shapes.

scholarly journals Sources and mechanisms of seawater freshening at the Tsivol’ki and Sedov’ bays (Novaya Zemlya): isotope (δD, δ18О) data

2019 ◽  
Vol 59 (6) ◽  
pp. 928-938
Author(s):  
E. O. Dubinina ◽  
S. A. Kossova ◽  
A. Yu. Miroshnikov
Keyword(s):  
Surface Waters ◽  
Water Exchange ◽  
Free Water ◽  
Kara Sea ◽  
River Waters ◽  
Fresh Waters ◽  
Novaya Zemlya ◽  
Deep Waters ◽  
Continental Runoff ◽  
The Difference

Three-year monitoring of isotope (D, 18О) parameters in the waters of the Sedov and Tsivolki bays (Novaya Zemlya) was carried out. The fresh waters of the bays are originated from several sources (continental runoff, precipitations, and waters going from the archipelago). The freshening extent and sources of fresh waters are different at the different depth. The D and 18О values varies only in the surface waters which contains more than 30% of fresh component. In 2015 the surface waters of Sedov bay were represented by Ob river waters, and the surface waters of Tsivolki bay were enriched by the runoff from Novaya Zemlya. Deep waters in both bays show signs of desalination by high latitude atmospheric precipitations. These waters can be transferred to the southeast coast of Novaya Zemlya through the trenches of St. Anne and Voronin. The difference in the freshening mechanisms of the waters of Sedov and Tsivolka bays is determined by different bottom morphologies and different degrees of free water exchange with the Kara Sea.

scholarly journals A Simple Method for the Detection of Biofilms Using a Heatable Capacitive Sensor Structure (CSS): Description, Proof of Concept, and Some Technical Improvements

Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 445
Author(s):  
Kai-Uwe Zirk ◽  
Manuel Olze ◽  
Harald Pötzschke
Keyword(s):  
Printed Circuit Boards ◽  
Free Water ◽  
Spray Coating ◽  
Internal Surface ◽  
Capacitive Sensor ◽  
Simple Method ◽  
Realistic Condition ◽  
Main Challenge ◽  
Sensor Structure ◽  
The Difference

This article presents a novel method for the detection of biofilms based on a heatable, capacitive sensor structure (CSS). Biofilms are capable of strongly binding large amounts of water to their extracellular biopolymer matrix, which is detectable via its dielectric properties. A main challenge is to determine the difference between the inherent occurring presence of moisture in the ecosystem, which is necessary to form a biofilm and an actual formed biofilm. Therefore, the CSS is carefully heated to evaporate unbound surface moisture and determine whether there is a remaining residual alternation of the capacitance in comparison to the dry state. As a reproduceable substitute for complex, real biofilms, a hygroscopic, medical hydrogel-based on polysaccharides was used and applied by spray coating. Printed circuit boards (PCB) in different geometries and materials were used as CSS and compared in terms of their performance. A layer-thickness of 20 µm for the hydrogel coating to be sufficiently detected was defined as a realistic condition based on known values for real biofilms cited in literature. For this thickness a double-meander structure proves to be preferable over interdigitating and spiral geometries. It does offer a 30% lower, yet sufficient sensitivity, but shows advantages in manufacturing (one layer instead of two) and conductive heating capability. In the experiments, free water showed virtually no residual change, while the hydrogel-coated CSS still shows an approx. 300% higher value compared to a dry capacity. Yet, the overall small capacities of about 6–30 pF in dry state are difficult to measure and therefore sensitive to interferences and noise, which results in a high deviation. The principle of measurement can be evaluated as proofed by the carried out experiments, though offering room for improvement in the design of the study. The new method might be especially useful for pipes (e.g., hydrodynamically ineffective sensors installed in a pipe wall) if they at least are not permanently flooded with an aqueous medium, but can occasionally dry. If the internal surface is still only moist, it can be dried by initial heating.

scholarly journals Study of Stacked High Tc Superconducting Circular Disk Microstrip Antenna in Multilayered Substrate Containing Isotropic and/or Uniaxial Anisotropic Materials

2019 ◽  
Vol 8 (3) ◽  
pp. 1-5 ◽  
Author(s):  
A. S. Boughrara ◽  
S. Benkouda ◽  
A. Bouraiou ◽  
T. Fortaki
Keyword(s):  
Microstrip Antenna ◽  
Layer Structure ◽  
Fluid Model ◽  
Single Layer ◽  
Circular Disk ◽  
Complex Surface ◽  
Anisotropic Materials ◽  
High Tc ◽  
Two Fluid Model ◽  
Circular Disks

In this paper, we present a rigorous full-wave analysis able to estimate exactly the resonant characteristics of stacked high Tc superconducting circular disk microstrip antenna. The superconducting patches are assumed to be embedded in a multilayered substrate containing isotropic and/or uniaxial anisotropic materials (the analysis is valid for an arbitrary number of layers). London’s equations and the two-fluid model of Gorter and Casimir are used in the calculation of the complex surface impedance of the superconducting circular disks. Numerical results are presented for a single layer structure as well as for two stacked circular disks fabricated on a double-layered substrate.

scholarly journals Synthesis of heterovalently substituted slab perovskites Sr2–xLnxBIV1–xBxIIIO4 (BIV= Sn, Ti, BIII= Sc, In)

2021 ◽  
pp. 77-83
Author(s):  
Y.A. Titov ◽  
◽  
M.S. Slobodyanik ◽  
V.V. Chumak ◽  
M.V. Tymoshenko ◽  
...  
Keyword(s):  
Layer Structure ◽  
Single Layer ◽  
Continuous Phase ◽  
Phase Region ◽  
Heterovalent Substitution ◽  
Linear Type ◽  
X Ray ◽  
Unit Cells ◽  
Pseudobinary Systems ◽  
New Compounds

The possibility of the heterovalent substitution of A- and B-positions atoms in a single-layer slab perovskite-like structure of strontium titanate and stannate Sr2BIVO4 (BIV= Ti, Sn) by type Sr2–xLnxBIV1–xBxIIIO4 (Ln == La – Tb, BIV= Ti, Sn, BIII= Sc, In) has been established by X-ray powder diffraction methods. The bounda-ries of the heterovalent substitution of A- and B-positions atoms and the crystallographic parameters of the synthesized Sr2–xLnxBIV1–xBxIIIO4 phases with a single-layer structure are determined. The continuous phase area formation with a single-layer structure has been observed in 10 systems: Sr2–xLnxTi1–xScxO4 (Ln = La, Pr, Nd, Sm, Eu), Sr2–xLnxTi1–xInxO4 (Ln = La, Pr), Sr2–xLaxSn1–xScxO4, Sr2–xLnxSn1–xInxO4 (Ln = La, Pr). In-creasing the degree of heterovalent substitution of atoms in these systems leads to a reduction of the sym metry of the crystal lattice of phases from the tetragonal (space group I4/mmm) to the interconnected rhombic one. In the rest of the studied Sr2–xLnxBIV1–xBxIIIO4 systems, the existence of a narrow (x value significantly less than 1) phase region with a single-layer structure based on Sr3BIVO7 is observed. The character of the phase relations in the Sr2–xLnxBIV1–xBxIIIO4 systems (Ln = La – Tb, BIII= Sc, In) (BIV= Sn, Ti) and the linear type of concentra-tion dependences of the parameters of the reduced tetragonal unit cells of Sr2–xLnxBIV1–xBxIIIO4 phases with a single-layer structure indicate that, by their nature, these phases are series of solid solutions in the pseudobinary systems Sr2BIVO4 – SrLnBIIIO4 (BIV= Ti, Sn, BIII = Sc, In). The obtained data can be used to regulate the functional properties of titanates and stannates Sr2BIVO4 and materials based on them, as well as to solve the problem of a purposeful search for new compounds of the type An+1BnO3n+1 with a slab perovskite-like structure.

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