Expansion Contraction Research Articles

Method for Predicting the Water Absorption of External Insulating Silicone Rubber

The intrusion of moisture may induce an abnormal increase in temperature or may even cause fractures in insulation equipment. Therefore, the hygroscopicity of rubber materials must be characterized. However, the existing methods for weighing organic polymer materials, such as silicone rubber, for moisture-absorption tests are time-consuming. In this article, a practical method for testing the moisture-absorption performance of silicone rubber materials for external insulation is proposed. The basic characteristics of the Langmuir diffusion equation for the water-absorption characteristics of silicone rubber are analyzed. A Langmuir curve fitting method based on the contraction–expansion (C–E) algorithm is developed, and its fitting effect is preliminarily verified by combining the experimental errors obtained from the experiment. Results show that the fitting effect has a strong relationship with the initial range of diffusion coefficient, bonding coefficient, and debonding coefficient. The time-consuming process of directly applying the fitting method is reduced from 70 to 50 days. The initial ranges of diffusion, bonding coefficient, and debonding coefficient are determined via the results of molecular simulations and experiments combined with an analysis of the literature. A prediction model is optimized and then validated against the experimental data from the recent literature on the water-absorption characteristics of silicone rubber at different temperatures. The experimental time required to reach saturated water absorption is remarkably reduced from 70 days to 1 day. Therefore, the method developed herein is feasible for engineering applications. Moreover, the entire water-absorption curve can be possibly plotted with an error of not greater than 5% via this prediction method.

Low temperature synthesis of NiO/CoO nanostructures to enhance their low temperature oxygen reduction catalysis

“Thermal expansion and cold contraction” are common occurrences in nature. Resulting from “thermal expansion and cold contraction” reaction, strain effect is created, which affects the oxygen reduction reaction (ORR) activities of fuel cell catalysts. Nevertheless, the “thermal expansion and cold contraction” effects of catalysts have rarely been investigated. Herein, the influence of “thermal expansion and cold contraction” strains upon ORR activities of NiO/CoO catalysts is investigated. Experimental and first-principles calculations reveal that, when NiO/CoO are synthesized and used as catalysts under low temperature ice/water environment, there is virtually no strain effect created, and abundant active sites contribute to the good low temperature ORR activities of NiO/CoO catalysts (onset potential: 0.736 V, halfwave potential: 0.659 V). When high temperature synthesized NiO/CoO catalysts are used at low temperature, however, small amounts of active sites are created. Moreover, the adsorption activity of NiO(222) and CoO(311) stepped active sites are weakened by compressive strain of lattice contraction, which reduces their ORR activities. The “low temperature synthesis and low temperature catalysis” route proposed by this paper paves a new road for the synthesis and design of low-temperature catalysts.

Propagating Superior-Quality Singleton Children as Anticipatory Modernization: Contextualizing Western Perspectives on Chinese Transnational Adoption

ABSTRACT We conducted a relational dialectics analysis of 259 Chinese birth planning policy propaganda. We identified a coalition of five discourses animating the texts. We found the coalition created conditions of monologic wholeness, characterized by simultaneous dialogic expansion and dialogic contraction. Dialogic expansion promised a utopic, future China in exchange for birth parents’ childbirth sacrifices and creation of a generation of superior-quality singleton Chinese children. Dialogic contraction reified superior-quality singletons as irrefutable antecedent for China’s modernization. This study holds both academic and practical significance. Academically, this study accelerates family communication’s critical theoretical turn, highlights complexities of studying monologue, expands the area’s dataset boundaries, and furthers diversity efforts. Practically, this study promises transformation of acontextual Western perspectives on China’s birth planning program. The study’s non-Western perspective is timely, given increasing momentum within the Chinese transnational adoption birth family search and reunion movement.

Electroviscous effects in charge-dependent slip flow of liquid electrolytes through a charged microfluidic device

This work investigates electroviscous effects in the presence of charge-dependent slip in steady pressure-driven laminar flow of a symmetric (1:1) electrolyte liquid through a uniformly charged slit contraction–expansion (4:1:4) microfluidic device. The mathematical model comprising the Poisson’s, the Nernst–Planck, the Navier–Stokes, and the current continuity equations are solved numerically using the finite element method (FEM). The flow fields (electrical potential, charge, induced electric field strength, pressure drop, and electroviscous correction factor) have been obtained and presented for the wide range of the governing parameters like inverse Debye length (2≤K≤20), surface charge density (4≤S≤16) and the slip length (0≤B0≤0.20) at fixed Schmidt number (Sc=1000) and low Reynolds number (Re=0.01). The flow fields have shown complex dependence on the governing parameters. The charge-dependent slip has further enhanced the complexity of the dependency in comparison to the no-slip condition. In presence of charge-dependent slip, the total electrical potential (|ΔU|) maximally increases by 78.68% and pressure drop (|ΔP|) maximally decreases by 63.42%, relative to no-slip flow, over the ranges of conditions. The electroviscous correction factor (Y= ratio of apparent to physical viscosity) increases by 33.58% under the no-slip (B0=0) condition. In contrast, the electroviscous correction factor (Y) increases maximally by 72.10% for charge-dependent slip than that in the no-slip flow for the considered ranges of the conditions. A simple analytical model to estimate the pressure drop in the electroviscous flow has been developed based on the Poiseuille flow in the individual uniform sections and pressure loss due to thin orifice. The model overpredicts the pressure drop by 2%–4% from the numerical values. Finally, the predictive relations, depicting the functional dependence of the numerical results on the governing parameters, are presented for their practical use in the design and engineering of microfluidic devices.

Enhanced iris presentation attack detection via contraction-expansion CNN

• Proposed a novel contraction-expansion CNN architecture for iris presentation attack detection. • Experiments in a generalized setting are performed to replicate real-world scenarios. • Extensive comparisons showcase the excellence of the proposed algorithm. The vulnerability of iris recognition algorithms against presentation attacks including textured contact lens is a serious concern. Several presentation attack detection (PAD) algorithms are developed; however, most of them suffer from low generalization capability. In this research, we propose a two head ‘contraction expansion’ convolutional neural network (CNN) architecture for robust presentation attack detection. The architecture’s input consists of raw image and edge enhanced image to learn the discriminating features for binary classification . The experiments using multiple iris presentation attack databases, including the LivDet-2017 and IIITD contact lens database (CLI), showcase the efficacy of the proposed algorithm. For example, the proposed iris presentation attack detection (IPAD) network yields 11.1% lower average classification error rate than recent state-of-the-art algorithm namely MVANet on the UnMIPA database when the system is trained on an unseen IIITD CLI database.

A Numerical Study of Mechanical Degradation of Carbon-Coated Graphite Active Particles in Li-ion Battery Anodes

During operation, different diffusive and mechanical phenomena take place inside LIBs that result in a loss of performance and, eventually, threaten battery life. One of the main drawbacks affecting anode materials is the significant volumetric expansion (contraction) experienced by active material particles during lithiation (delithiation) processes, which may cause fracture. In this work, we present a novel numerical model to analyze coupled diffusion-mechanical problems accounting for material inhomogeneities. We are able to describe the nucleation of cracks and their propagation during particle cycling, depending on charging and discharging rates. Moreover, our model is able to reproduce complex fracture processes such as branching and change of directions. This description relies on combined use of a randomness parameter and a stochastic characterization of material properties within a lattice model approach. The model is used to analyze the effect of particle coating as a strategy to diminish the effect of transient cracking (that leads to early capacity fade). This is studied in detail at the coating-substrate interface and novel material designs are tested within our simulation framework.

Effects of Boiling Processing on Texture of Scallop Adductor Muscle and Its Mechanism.

The objective of this study was to reveal the effects of boiling processing on the texture of scallop adductor muscle (SAM) and its mechanism. Compared to the fresh sample, all the texture indicators, including the hardness, chewiness, springiness, resilience, cohesiveness, and shear force of 30-s- and 3-min-boiled SAMs increased time-dependently (p < 0.05). As the boiling time increased further to 15 min, the shear force and cohesiveness still increased significantly (p < 0.05), and the resilience and hardness were maintained (p > 0.05), but the springiness and chewiness decreased significantly (p < 0.05). The overall increase in the texture indicators of the boiled SAMs was due to the boiling-induced protein denaturation, aggregation, and increased hydrophobicity, resulting in the longitudinal contraction and lateral expansion of myofibrils, the longitudinal contraction and lateral cross-linked aggregation of muscle fibers, and the loss of free water. However, the decreasing springiness and chewiness of the 15-min-boiled SAMs was due to the significant degradation of proteins (especially collagen), resulting in the destruction of the connective tissue between the muscle fiber clusters. Both from a subjective sensory point of view and from the objective point of view of protein denaturation and degradation, 3-min-boiled SAMs are recommended. The quality improvement of thermally processed products by controlled, moderate cooking is of practical value from the perspective of food consumption.

Sheathless inertial microfluidic cell separation via a serpentine–contraction–expansion device coupled with a combinatorial extraction regulator

Sheathless inertial microfluidic cell separation via a serpentine–contraction–expansion device coupled with a combinatorial extraction regulator

Hypoxia-inducedoxidative stress and apoptosisin gills of scaleless carp (Gymnocypris przewalskii).

Scaleless carp (Gymnocypris przewalskii) are well adaptedtolow oxygen environment, but their specific adaptation mechanism to hypoxic condition remains unclear. The gill is an important respiratory organ that plays a crucial role in regulating hypoxic stress. Here, we established fish hypoxic stress model, as well as investigated oxidative stress, apoptotic responses, and relative enzyme activities in the gills of scaleless carp after exposure to various levels of hypoxic stress. The results demonstrated that gill lamellar height and basal length increased significantly under severe hypoxic stress, and interval lengths between lamellae increased significantly under hypoxic stress. Furthermore, lamellar epithelial cells underwent apoptosis, cytoplasmic contraction, and mitochondrial expansion, and the number of apoptotic cells increased significantly after exposure to severe hypoxic stress for 24h. Subsequently, Bcl-2 and Caspase 3 mRNA levels, as well as Bcl-2/Bax expression ratio were significantly increased after exposure to severe hypoxic stress for 24h, indicating upregulation of anti-apoptotic processes. Moreover, malondialdehyde and hydrogen peroxide levels were significantly increased after exposure to hypoxic stress for 24h. Superoxide dismutase activity increased significantly after exposure to severe hypoxia for 8h and then decreased, while glutathione peroxidase activity and total antioxidant capacity increased significantly under hypoxic stress. Taken together, the results indicated that scaleless carp gills respond to acute hypoxic conditions by undergoing lamellar morphology remodeling, enhanced apoptosis, and increased antioxidant enzymatic activity. The study findings provided new insight into the adaptation mechanisms of scaleless carp in response to hypoxic challenge.

Nozzle Design for Rotating Detonation Engine

This work proposes a nozzle design procedure that uses an area-variational source term in the two-dimensional numerical simulations for rotating detonation engines. The derivation of this source term is carried out in detail, and the influences of area ratios, total lengths, and curve transitions on the aerodynamic performance are discussed. For a nozzle with no curve transition at critical cross-sections, the combination of contraction ratio and expansion ratio corresponds to the maximum axial thrust and maximum specific impulse at and , which exceed those of the diverging and converging nozzles by 11.3 and 27.6%, respectively. The extension of the total length is not recommended to attenuate fluctuations due to the thrust performance penalties. Concerning the curve transitions of the diverging part, the parabolic profile subp2 shows a 2.22% increase in thrust and specific impulse compared with four other types. The positive influence of a geometrical throat on the thermodynamic efficiency is demonstrated by the fluid particle tracing technique and the pressure gain analysis. Moreover, the feasibility of adding the area-variational source term is validated by three-dimensional simulations.

Experimental study on steam plume shape characteristics for bevelled spray nozzles exhausting into quiescent water

Steam-water direct contact condensation phenomenon is being widely used in many industries including chemical, thermal and especially in nuclear industry due to its efficient heat and mass exchange capabilities. The present experimental study explores the underlying physics of the steam cavity/plume shapes by condensing supersonic steam exhausting from five different bevelled nozzles into quiescent water tank. Based on the high speed image capturing methodology, the effects of steam pressure, water temperature and nozzle exit inclination angle on the cavity shape characteristics have been studied. Existence of six different plume shapes (oscillatory, conical, expansion–contraction, double expansion contraction, cylindrical and divergent) have been identified. The results show that for a fixed nozzle geometry, with the increase in water temperature and steam pressure, the steam jet becomes lengthy. However, under the same steam pressure and water temperature conditions, the plume shortens with the increase in nozzle exit inclination angle. The dimensionless jet length has been found in the range of 1.26–5.64. Furthermore, it has been observed that steam plume exhausting from bevelled nozzle undergoes deflection from its nozzle symmetry axis possibly due to the pressure difference between upper and lower lip of nozzle. This deflection may either be upward oriented at high steam pressure or downward deflected at lower steam pressure. Additionally, on the basis of findings from 175 No’s of experiments, condensation regime maps have also been developed for bevelled spray nozzle.

Hidden Akhmediev breathers and vector modulation instability in the defocusing regime

We study the dynamics of modulation instability (MI) of the vector nonlinear Schrödinger equations (the Manakov system) in the defocusing regime. A general family of exact Akhmediev breather (AB) solutions of intricate structures is presented. The physical spectra with infinite number of sidebands that describe the asymmetric expansion–contraction cycle are calculated analytically. In contrast to the MI dynamics in the focusing regime, an unusual phenomenon in the defocusing regime—hidden ABs with initial modulation frequency is revealed during nonlinear evolution of higher-order MI. Such a phenomenon is universal when the MI starts from simple periodic modulation with equal phase in the low-frequency region. We present the existence diagram of such excitations. A simple way to restore the hidden ABs is to consider the initial modulation with π phase difference. We substantiate all these findings by constructing exact multi-AB solutions with free parameters. It is shown that the hidden dark ABs appear as a result of nonlinear supposition between multi-dark-ABs.

Numerical Investigation on Spray Characteristics With Upstream Flow Pulsation of a Pintle Injector

The volume of fluid (VOF) model and the adaptive mesh refinement (AMR) method are used to study the spray characteristics of a gas–liquid pintle injector and the effects of mass flow pulsation of liquid on it. A pintle injector is a thrust adjusting device that changes the injection area using movable parts. Pressure pulsation in the supply pipeline is simulated by periodically changing the mass flow rate of the inlet. Spray characteristics with constant and pulsating upstream flows are compared with each other. The effect of frequency and amplitude of upstream liquid flow pulsation on the spray performance was studied. The results reveal that holding the mass flow rate of the upstream liquid flow constant, under the impact of gas flow, the liquid block, the liquid filament, and a large number of small droplets are peeled off from the liquid film. The film breakup position stays relatively fixed, and the spray has a conical shape. However, when the upstream liquid flow is pulsating, the film breakup position changes periodically, and the spray has a “Christmas tree”-shape. The pulsation frequency has little effect on the spray angle. But it strongly determines the droplet size and the spatial distribution of the spray. In addition, the pulsation amplitude can enhance the phenomenon of “Christmas tree.” With the increase in pulsation amplitude, the liquid film at the outlet of the pintle injector appears with a periodic phenomenon of “contraction–expansion.”

Inertial focusing and filtration of microparticles with expansion–contraction structures in microchannel

Inertial focusing and filtration of microparticles with expansion–contraction structures in microchannel

Data-based variable universe adaptive fuzzy controller with self-tuning parameters

Data-based variable universe adaptive fuzzy controllers (VUAFCs) with self-tuning parameters are developed for complex systems with unknown universes in this paper. The main feature of the proposed VUAFC is the new defined contraction–expansion (C-E) factor on an infinite universe, which is more flexible and practical in real applications. Moreover, the data-based methods to tune the parameters including the peak points of output fuzzy subsets and the C-E factor parameters are proposed. The peak points of the output fuzzy subsets are mined by an improved Wang–Mendel method based on conflicting rules. The parameters of the VUAFC are optimized by solving an offline optimization problem using the chaotic particle swarm optimization (CPSO) algorithm. The simulation results on the strip temperature control of the radiant-tube indirect-fired furnace of annealing furnace show that our proposed method has strong practicability and good control performance.

Topographic Complexity Facilitates Persistence Compared to Signals of Contraction and Expansion in the Adjacent Subdued Landscape

Topographically heterogeneous areas are likely to act as refugia for species because they facilitate survival during regional climatic stress due to availability of a range of microenvironments. The Stirling Ranges are a topographically complex area in the generally subdued and ancient landscape of south-western Australia. We investigated the influence of these landscape features on the evolutionary history of the rare woody shrub, Banksia brownii through a combined approach using phylogeographic analysis of sequence data from three chloroplast sequences, the trnV–ndhC, trnQ–rps16, and rpl32–ndhF intergenic spacer regions, and species distribution modeling. The Stirling Ranges showed high genetic diversity and differentiation among populations consistent with localized persistence and maintenance of large populations in an area that species distribution modeling identified as providing habitat stability at the Last Glacial Maximum as well as under warmer conditions. In contrast, populations in the adjacent subdued lowlands showed signals of low diversity, suggesting contraction, and subsequent expansion from localized refugia in the west. Cool summers are an important climatic variable for the species and species distribution modeling showed suitable habitat identified at the LGM suggesting expansion at this time following likely contraction during earlier warmer climatic oscillations. The isolated, coastal population at Vancouver Peninsula showed low diversity but no differentiation and it may have been established in more recent historical times, possibly through Aboriginal movement of seed. Our analysis of B. brownii highlights the complex evolutionary history of the species and the influence of topographic complexity and habitat heterogeneity in this global biodiversity hotspot.

Transcriptome and chromatin changes as regulatory T cells expand and contract to IL-2R signaling in vivo

Abstract Regulatory T cells are essential to maintain peripheral T cell tolerance and require IL-2R signaling for their development and homeostasis. Here, we used mouse IL-2 (mIL-2) and a fusion protein of mouse IL-2 linked to mouse CD25 (mIL-2/CD25) to induce acute, periodic, and persistent IL-2R-dependent signaling in peripheral Tregs in vivo. RNA- and ATAC-seq assessed longitudinal shifts in the transcriptome and chromatin landscape to define the molecular steps associated with IL-2R-dependent Treg activation, expansion, and subsequent contraction in vivo. Analysis of the RNA-seq data revealed that STAT5 and MYC were two critical drivers of IL-2R-dependent signaling in Tregs. Other signaling pathways were also identified that facilitate cell transcription, integration of TCR signaling, cell cycle progression, and growth. Sustained IL-2R signaling by mIL-2/CD25, but not periodic signaling by mIL-2, more effectively supported Treg expansion, oxidative phosphorylation, and development into eTregs. With respect to chromatin remodeling, IL-2R signaling initially preferentially increased accessibility to binding sites and activity of STAT5, whereas more persistent IL-2R signaling favored accessibility and activity of other transcription factors, dominantly CTCF, followed by a genome-wide less accessible chromatin. Our data favor a model whereby persistent IL-2R signaling initially supports more accessible chromatin and active transcription leading to a metabolic shift toward a more energetic type required for Treg proliferation. Subsequently, as IL-2R signaling diminishes, a shift toward less accessible chromatin occurs that facilitates contraction of the expanded Tregs to restore homeostasis. This research was supported by funding from Bristol Myers Squibb and the NIH (R01AI148675).

Comparative Analyses of Chloroplast Genomes Provide Comprehensive Insights into the Adaptive Evolution of Paphiopedilum (Orchidaceae)

An elucidation of how the selection pressures caused by habitat environments affect plant plastid genomes and lead to the adaptive evolution of plants, is a very intense area of research in evolutionary biology. The genus Paphiopedilum is a predominant group of orchids that includes over 66 species with high horticultural and ornamental value. However, owing to the destructive exploitation and habitat deterioration of wild germplasm resources of Paphiopedilum, it needs more molecular genetic resources and studies on this genus. The chloroplast is cytoplasmically inherited and often used in evolutionary studies. Thus, for this study, we newly sequenced, assembled and annotated five chloroplast genomes of the Paphiopedilum species. The size of these genomes ranged from 155,886 bp (P. henryanum) to 160,503 bp (P. ‘GZSLKY’ Youyou) and they contained 121–122 genes, which consisted of 76 protein coding genes, eight ribosomal RNAs, and 37–38 transfer RNAs. Combined with the other 14 Paphiopedilum species, the characteristics of the repeat sequences, divergent hotspot regions, and the condo usage bias were evaluated and identified, respectively. The gene transfer analysis showed that some fragments of the ndh and ycf gene families were shared by both the chloroplast and nucleus. Although the genomic structure and gene content was conserved, there was a significant boundary shift caused by the inverted repeat (IR) expansion and small single copy (SSC) contraction. The lower GC content and loss of ndh genes could be the result of adaptive evolutionary responses to its unique habitats. The genes under positive selection, including accD, matK, psbM, rpl20, rps12, ycf1, and ycf2 might be regarded as potential candidate genes for further study, which significantly contribute to the adaptive evolution of Paphiopedilum.

Regulation of energy band and luminescence properties in blue quasi-2D lead bromide perovskite via lattice strain

Development of blue quasi-2D lead halide perovskite LEDs is key to the perovskite based full-color displays and white-light illumination. It is still quite challenging to accurately enlarge the bandgap to achieve high performance and stable blue Quasi-2D perovskite LEDs. The lattice strain due to the deformation of lead-bromide octahedra is a critical factor leading to the energy band adjustment and stability optimization. In this Letter, the lattice strain is adjusted via three cations with different sizes, Cs+, CH3CH2NH2+ (EA+), and Rb+, for sophisticatedly micro-tuning of the lattice strain to achieve overall lattice expansion and lattice contraction. A ternary quasi-2D blue bromide perovskite material PEA2(CsxEAyRb1-x-yPbBr3)2PbBr4 is specially designed. The crystal structure and energy band are studied by the first principles calculations using the Density Functional Theory method. The luminescence properties of blue quasi-2D lead bromide perovskite materials are analyzed with spectra regulation from 508 to 464 nm for photoluminescence and from 510 to 470 nm for electroluminescence. The thermal treatment is used to accelerate the release of residual strain due to mismatch and disorder in the lattice, leading to defects and degradation. The lattice strain is strongly correlated with the energy band, luminescence performance, and thermal stability of blue quasi-2D lead bromide perovskite. The study of lattice strain relaxation in blue quasi-2D lead bromide perovskite could open avenues for high-performance and stable blue quasi-2D perovskite LEDs.

Two-Dimensional Negative Thermal Expansion in a Crystal of LiBO2

Negative thermal expansion (NTE), violating the common sense of “thermal expansion and cold contraction” effects, is a novel temperature-responding behavior of great scientific and technical significance. Herein, we report a two-dimensional (2D) NTE behavior in a crystal of LiBO2, which is constructed by graphite-like [LiBO2]∞ layers. This intriguing thermal property originates from the synergistic effect of the distortion of in-plane [LiO3] bases in [LiO4] tetrahedra and the rotation of [BO3] triangles in the [LiBO2]∞ layer, driven by the force perpendicular to the layer owing to the large interlayer separation as temperature increases. Remarkably, the in-plane and out-of-plane Li–O bonds within the [LiO4] tetrahedra have nearly the same bond strength and exhibit the similar variation with respect to temperature, and this is quite different from the common sense on the 2D NTE behavior in layered structures that the intralayer atomic interaction must be much stronger than the interlayer ones. Our study deepens the understanding of the 2D NTE mechanism and would promote the exploration for NTE materials.