Stable Fluid Research Articles

Polyphase hydrothermal sulfide mineralization in the minami–ensei hydrothermal field, middle okinawa trough: Implications from sulfide mineralogy and in situ geochemical composition of pyrite

The mineralogical and geochemical zonation of hydrothermal chimneys preserve important information on mineralization process and hydrothermal evolution. In this study, the sulfide mineralogy and in situ geochemical compositions of pyrite from a hydrothermal chimney in the Minami–Ensei (ME) hydrothermal field were analyzed systematically to determine the mineralization characteristics. Seven layers with different mineral compositions were observed in an individual chimney from ME, including four pyrite-dominant layers and three barite-rich layers. The barite-rich layers occur mainly as intercalations in the hydrothermal chimney, i.e., barite-rich layers and pyrite-dominant layers precipitate alternately, suggesting the occurrence of a polyphase mineralization process, which is highlighted by the in situ trace elements and sulfur isotope compositions of pyrite. The extremely low Co, Ni, Cu, and Se contents (<1 ppm) and high Pb, As, Tl, Mn, and Zn contents (up to several thousands of ppm) in pyrite indicate that the mineralization fluid temperature is unlikely to be higher than 200 °C, which allows the bacterial reduction of seawater sulfate, causing negative shifts in the δ34S values of ME pyrite (−5.00 ‰ to 4.01 ‰). The stable fluid pathway and aperiodic variations in magmatic intensity cause polyphase sulfide mineralization in an individual hydrothermal chimney in the ME hydrothermal field.

Insightful study on the effect of zinc oxide nanoparticle diameter on the rheology of water base mud at elevated temperature

In deep water reservoir and more complex formation, the usage of special and advanced methods of drilling and production operation is considered vital to complete the drilling/production operation. However, they are considered costly and may not be environmentally friendly. Recently, nanoparticles have been introduced to drilling fluids to form a greater nanofluid with better rheological property, filtration rates and hydrogen concentration. This study is, therefore, aimed at investigating the effects of zinc oxide (ZnO) nanoparticles sizes on the rheological properties of water base mud (WBM) from surface to downhole conditions. Surface morphology and elemental composition of ZnO nanoparticles were also analyzed. The experiment was designed into three phases. In the first phase, the rheological properties of conventional WBM were tested, and in the second phase 0.5 wt% (3 g) of 10–30 nm of ZnO nanoparticles was added into WBM to test the rheological properties. The last phase included a bigger size of ZnO nanoparticles, which was 30–45 nm. A Consistometer was used to heat the fluid sample to different temperatures reaching up to downhole condition (90 °C). Viscosity, gel strength and yield point were measured using a rotational viscometer. Field emission scanning electron microscopy (JEOL JSM-7800F, Japan) attached with energy dispersive X-ray spectroscopy (EDXS, Oxford instrument, UK) were used to investigate surface morphology and elemental composition of ZnO nanoparticles. It was observed that the rheological properties of water base mud with zinc oxide nanoparticles were improved significantly by 40%–65%. The bigger size of zinc oxide nanoparticle, 30–45 nm, formed a more stable fluid at all conditions.

A carbon nanosphere nanofluid for improving the toughness and thermal properties of epoxy composites

A carbon nanosphere nanofluid (CNS-nanofluid) was successfully prepared through the non-covalent modification of carbon nanosphere (CNS) with the specific ionic liquid (i.e. [M2070][VBS]) at first. The resulting CNS-nanofluid is a homogeneous and stable fluid with liquid-like behaviour at room temperature, and which shows better dispersion stability in its good solvents and improved processability than the pristine CNS. Subsequently, this CNS-nanofluid was used as a kind of novel functional filler and incorporated into epoxy matrix to prepare the CNS-nanofluid filled epoxy composites (CNS-nanofluid/EP composites). The toughness and thermal properties of those CNS-nanofluid/EP composites were carefully characterized and analysed. And it was found that this CNS-nanofluid could respectively improve the impact toughness and glass transition temperature of the CNS-nanofluid/EP composites to 19.8 kJ m−2 and 122.5 °C at the optimum amount, demonstrating that this CNS-nanofluid is a kind of promising functional filler to achieve robust epoxy composites, and thus opening up new possibilities with great significance for epoxy composites in high-performance applications.

Geological activity shapes the microbiome in deep-subsurface aquifers by advection

Subsurface environments host diverse microorganisms in fluid-filled fractures; however, little is known about how geological and hydrological processes shape the subterranean biosphere. Here, we sampled three flowing boreholes weekly for 10 mo in a 1478-m-deep fractured rock aquifer to study the role of fracture activity (defined as seismically or aseismically induced fracture aperture change) and advection on fluid-associated microbial community composition. We found that despite a largely stable deep-subsurface fluid microbiome, drastic community-level shifts occurred after events signifying physical changes in the permeable fracture network. The community-level shifts include the emergence of microbial families from undetected to over 50% relative abundance, as well as the replacement of the community in one borehole by the earlier community from a different borehole. Null-model analysis indicates that the observed spatial and temporal community turnover was primarily driven by stochastic processes (as opposed to deterministic processes). We, therefore, conclude that the observed community-level shifts resulted from the physical transport of distinct microbial communities from other fracture(s) that outpaced environmental selection. Given that geological activity is a major cause of fracture activity and that geological activity is ubiquitous across space and time on Earth, our findings suggest that advection induced by geological activity is a general mechanism shaping the microbial biogeography and diversity in deep-subsurface habitats across the globe.

Analysis on thermal conductivity of green processed alumina nanofluid for thermal industries

The dual mechanism played by curry leaf extract on synthesis of alumina nanoparticles contributes a significant enhancement in thermal conductivity of alumina nanofluid with appreciably small volume fraction from 0.01%–0.05%. The most probable particle size of alumina nanoparticle dispersed in water of 3.12 nm observed from particle size analyser along with a strong absorption peak at λ max around 238 nm confirms the alumina nanoparticles in the fluid. The increase of energy band gap from 4.8 to 5.12 eV indicates the decrease in size of the nanoparticle solely attributed to contribution of curry leaf extraction method of preparation of nanoparticles. The spherical shaped alumina nanoparticle has got high thermal conductivity with enhancement from 1.8% to 21.44% which is attributed to the significant contribution of H-atom as energy storage unit in water. With increase of sonication time, thermal conductivity varies appreciably from 0.531 W mK−1 to 0.736 W mK−1 with volume fraction of nanofluid. Therefore, the novel combinations of characterised properties of Al2O3 nanofluid have proved to be the best thermally stable heat transfer fluid compared to conventional cooling fluids.

On the issue concerning improvement of a mud preparation technology at the expense of hydrodynamic cavitation

Purpose is to improve the technology of drilling mud by applying hydrodynamic cavitation. Research methodology is represented by the theoretical and experimental studies of hydrodynamic cavitation, performed with the help of modern methods of analytical analysis and experimental studies, i.e. by using general principles of mathematical and physical modeling, methods of processing research results in EXCEL, SolidWorks for further analysis. Research results. Frequency of cavitation oscillations according to the parameters of a device for creating hydrodynamic cavitation has been calculated. The formula for determining the dispersion time of the washing liquid material by the frequency of cavitation oscillations has been theoretically substantiated and obtained. A process of moving drilling fluid in the device using the appropriate software in the SolidWorks package has been studied. The results of theoretical research have been confirmed by practical research and chosen as a basis for substantiation and development of the methods for preparing drilling fluids. Originality is represented by modeling and research of the process of hydrodynamic cavitation in a cavitation device using flow visualization using SolidWorks software. This approach helped substantiate and predict the pressure and flow velocity at each point of transition of the diameters of a cavitation dispersant. This, in turn, has made it possible to reduce hydraulic resistance and improve the device design to implement a technology of preparation of drilling fluids due to hydrodynamic cavitation. This approach has allowed substantiating and performing virtual experiments on the technology of preparation of drilling fluids; that has helped select rational design parameters of the cavitation disperser and save a lot of money and time on the production of bench samples of the device, including various design features. Practical implications. Basing on the results of both theoretical and experimental studies, the development of advanced technology for the preparation of stable drilling fluids be applying rational indicators of hydrodynamic cavitation has been substantiated and proposed.

An Detailed Study on Nano Fluids and Its Applications in Energy Sector

Nano liquids are primarily used as coolants for their advanced heat properties in heat exchangers such as Electronic cooling systems (Like flat plates) and radiators. Heat transfer on a flat plate has been analyzed by several researchers. The nanofluid is prepared by suspending small nanoparticles in basic Water and ethylene glycol Such as fluids with or without stabilization techniques. The average size of nanoparticles is less than 100 nm, and The nanoparticles used in nano liquids are usually. The base fluid is a Well stimulant treatment fluid used in cosmetics Continuous phase fluid. Continuous phase fluid may be added, But it is not defined as water, and whether it is liquid or hydrocarbon May be without hydrocarbon gas. Well-induced therapy More than one base fluid can be used. The atomic number can Derived from the dimensional analysis of the Fourier law, because it is equal to the dimensionless temperature gradient at the surface: q Heat transfer rate, k is the constant heat. Conductivity and T is the temperature of the liquid. Sodium benzoic sulfate (SDBS) Water is used as a surfactant in the preparation of nano liquids. Cu nanoparticles with demonized water Nano-liquid samples of three-volume fractions are prepared; the average diameter of the nanoparticles is 25 nm. Many researchers have called the validity stability of nanofluids. The scattering behavior of various non-substances in the solvent varies and depends on many factors. A complete understanding of particle-particle-particle interaction to create a stable fluid. Electronics heat management and increasing the efficiency of fluids for transfer from air to liquid cooling systems. Improving the energy efficiency of electronic systems. Improving rack density for computer systems by reducing computers to sub-1U operating systems. Improvement in Power Module Life (MTPF). A nanofluid is a liquid containing particles the size of nanometers. The Nano liquids are obtained by scattering. Non-aqueous fluid (NAF) is a water-based permeable fluid. Commonly used NAF systems are reverse emulsions based on diesel oil, mineral oil or synthetic fluid. In NAF systems, the water level is emulsified in a continuous oil phase, also known as water-in-oil emulsion or reverse emulsion. Nusselt A is the number Is the dimensionless number closest to the pocket number. Both numbers are held inside the fluid Will be converted to a liquid with thermal energy Used to describe the ratio of thermal energy.

Shape-driven, emergent behavior in active particle mixtures

Active particle systems can vary greatly from one-component systems of spheres to mixtures of particle shapes at different composition ratios. We investigate computationally the combined effect of anisotropy and stoichiometry on the collective behavior of two-dimensional active colloidal mixtures of polygons. We uncover three emergent phenomena not yet reported in active Brownian particle systems. First, we find that mixtures containing hexagons exhibit micro-phase separation with large grains of hexagonal symmetry. We quantify a measurable, implicit ‘steric attraction’ between the active particles as a result of shape anisotropy and activity. This calculation provides further evidence that implicit interactions in active systems, even without explicit attraction, can lead to an effective preferential attraction between particles. Next, we report stable fluid clusters in mixtures containing one triangle or square component. We attribute the fluidization of the dense cluster to the interplay of cluster destabilizing particles, which introduce grain boundaries and slip planes into the system, causing solid-like clusters to break up into fluid clusters. Third, we show that fluid clusters can coexist with solid clusters within a sparse gas of particles in a steady state of three coexisting phases. Our results highlight the potential for a wide variety of behavior to be accessible to active matter systems and establish a route to control active colloidal systems through simple parameter designs.

Synthesis and thermal properties of n-tetradecane phase change microcapsules for cold storage

Due to the high heat carrier density, latent heat functional fluid may be used as the secondary refrigerant in air conditioning system. In this study, two-step in-situ polymerization method is used to synthesis microcapsules of ploy (urea-formaldehyde) (UF), where n-tetradecane is used as core material and SDS as emulsifier. Microcapsules with excellent morphology and performance are obtained by adjusting the emulsifier mass fraction, stirring rate, polymerization PH value and core-shell mass ratio. The experimental results show that when the mass fraction of SDS is 1.2 wt%, the initial PH value is 3.5 and the core-shell mass ratio is 2: 1, phase change microcapsules have good dispersibility. The phase change enthalpy of the microcapsules reach to 178.1 J·g−1, whose encapsulation rate is up to 85.6%. A latent heat functional fluid is prepared using the synthesized microcapsules and the base liquid of water and absolute ethanol. When the ethanol mass fraction in the base fluid is about 74 wt%, the stable latent heat functional fluid is obtained. The thermal conductivity of the latent heat functional fluid increases with the increase of temperature, and decreases with the increase of the mass fraction of microcapsules. Its viscosity rises with the increase of temperature or the mass fraction of microcapsules.

Application of response surface methodology for a feasibility study of producing stable semi-aphron fluids using natural materials

ABSTRACT Due to the drilling problems in fractured reservoirs, multiphase lightweight fluids are essential. To produce lightweight fluids and to achieve the desired stability, a variety of chemical and natural surfactants are used. However, natural surfactants are more in demand due to environmental issues and challenges. The goal of this research is to produce a lightweight fluid using a combination of natural materials. Moreover, colloidal gas aphron (CGA) based drilling fluids are prepared at 5,000 to 10,000 rpm stirring speed; therefore in this research, the production feasibility of stable multiphase fluid (called semi-aphron) was investigated at a lower stirring speed (1,500 rpm) without Xanthan Gum polymer. The applied natural raw materials, were Acanthophyllum bracteatum root (ABR), Glycyrrhiza glabra root (GGR), and Tetraclinis articulata fruit (TAF) powders that were mixed with Persian Gulf seawater. Three models of response surface methodology (RSM) were utilized to assess the effects of natural materials concentration (0 to 0.2%wt.) on the stability and drained volume (DV) of the liquid phase at 25°C and 70°C. The utilized models were central composite design (CCD), typical custom design (TCD), and modified custom design (MCD). Based on the results, the optimum concentration for ABR, GGR, and TAF were 0.2%, 0.1%, and 0.1% wt., respectively. The produced fluids, using the combination of natural materials, had better stability than the base fluid (using SDS). The optimum concentration of natural material delayed the drainage of the liquid by about 70% at ambient temperature (25°C), and by about 50% at 70°C. The MCD model showed better-predicted R2 at ambient temperatures and 70°C (0.91 and 0.88, respectively) than the other two models, and would estimate the amount of DV better. The results showed that ABR and TAF had an inverse effect on DV at 25°C; thus, ABR and TAF increased semi-aphron stability, whereas GGR increased DV and semi-aphron instability. The results of this study can be considered for the application of native natural materials (ABR, GGR, and TAF) in the production of light drilling fluids, which reduces the environmental challenges of drilling fluids.

Effect of an excess of surfactant on thermophoresis, mass diffusion and viscosity in an oily surfactant-stabilized ferrofluid.

The effect of an excess of surfactant on the thermophoresis of a sterically stabilized ferrofluid is investigated experimentally by forced Rayleigh scattering (FRS). The experiments are performed with a stable magnetic fluid sample to which controlled amounts of surfactant are added. A decrease in the thermally induced transport of magnetic nanoparticles is observed while increasing the temperature T. The positive Soret coefficient [Formula: see text] decreases by adding 2vol% of surfactant at room temperature. As shown by FRS relaxation, this decreasing is mainly associated with a reduction of the interaction between the carrier fluid and individual nanoparticles. No significant effect of extra surfactant on the sign of [Formula: see text] is observed at higher T's (up to [Formula: see text]C). Dynamic light scattering at room temperature reveals the presence of a small amount of clusters/aggregates in the samples, which are hardly detectable by FRS relaxation. The presence of these small clusters/aggregates is confirmed by a rheological probing of the fluid properties. Whatever T, a small amount of added surfactant first causes a decrease of the ferrofluid viscosity, associated with a 10% decreasing of the flow activation energy. Further on, viscosity and activation energy both recover at higher excess surfactant concentrations. These results are analyzed in terms of saturation of the surfactant layer, concentration of free surfactant chains and heat of transport of the nanoparticles.

Porous Liquids: Computational Design for Targeted Gas Adsorption.

In this Perspective, we present the unique gas adsorption capabilities of porous liquids (PLs) and the value of complex computational methods in the design of PL compositions. Traditionally, liquids only contain transient pore space between molecules that limit long-term gas capture. However, PLs are stable fluids that that contain permanent porosity due to the combination of a rigid porous host structure and a solvent. PLs exhibit remarkable adsorption and separation properties, including increased solubility and selectivity. The unique gas adsorption properties of PLs are based on their structure, which exhibits multiple gas binding sites in the pore and on the cage surface, varying binding mechanisms including hydrogen-bonding and π-π interactions, and selective diffusion in the solvent. Tunable PL compositions will require fundamental investigations of competitive gas binding mechanisms, thermal effects on binding site stability, and the role of nanoconfinement on gas and solvent diffusion that can be accelerated through molecular modeling. With these new insights PLs promise to be an exceptional material class with tunable properties for targeted gas adsorption.

Subthreshold Exudative Choroidal Neovascularization (CNV): Presentation of This Uncommon Subtype and Other CNVs in Age-Related Macular Degeneration (AMD).

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss in people over the age of 50 worldwide. Exudative or neovascular AMD is a more severe subset of AMD which is characterized by the presence of choroidal neovascularization (CNV). Recent advancements in multimodal ophthalmic imaging, including optical coherence tomography (OCT) and OCT-angiography (OCT-A), have facilitated the detection and characterization of previously undetectable neovascular lesions and have enabled a more refined classification of CNV in exudative as well as nonexudative AMD patients. Subthreshold exudative CNV is a novel subtype of exudative AMD that typically presents asymptomatically with good visual acuity and is characterized by stable persistent or intermittent subretinal fluid (SRF). This review aims to provide an overview of the clinical as well as multimodal imaging characteristics of CNV in AMD, including this new clinical phenotype, and propose effective approaches for management.

Non-Classical Canon in ANT/STS: How a Ship Turns Into a Pump?

The article examines the canon as a principle of the formation of the actor-network writing technique and its influence on the formation of the Lancaster School, which exists at the intersection of Actor-Network Theory (ANT) and Science and Technology Studies (STS). The discussion of the canon is built around the idea of canonical experiments by Robert Boyle, which served as a model for modern experimental science. As an experimental technique, the canon is contrasted with the principle of distinguishing classics of Sociology and classical texts that are part of the university canon. The (un)classical forms of organizing the mobile canon are described in the case studies by John Law and Annemarie Mol of the mobile/movable technologies. Two cases are highlighted for analysis, which are described in John Law's article “Objects and Spaces”: “Portuguese vessel” as “immutable mobile”, which maintains its shape due to movement, and “Zimbabwe pump” as “fluid technology” with a stable core and fluid border of the periphery. The analysis of each of the cases, highlighting their trajectories of movement between different texts, strategies for simplifying the analyzed situations and working with the organization of a research article, allows to describe the mobile ANT/STS canon as a result of overlapping two axes: an empirical/theoretical description and the core of control/controlled periphery. Thus, it is shown how the movable canon acquires a stable core in Law's article “Objects and Spaces” and becomes the basis for the further development of the Lancaster School.

Geology and genesis of the North Narbaghi Cu-Ag deposit in the Urumieh-Dokhtar magmatic arc, Iran: Fluid inclusion and stable isotope constraints

The North Narbaghi Cu-Ag deposit in the central part of the Urumieh-Dokhtar magmatic arc (UDMA) of Iran is hosted by Eocene volcanic sequences and Oligo-Miocene intrusions of arc affiliation. The mineralization can be divided into five stages that are represented by barren hydrothermal breccias, Cu-Fe sulfides cementing in the breccias, sulfosalt and sulfide hydrothermal breccias, barren post-ore quartz veinlets, and barren post-ore calcite veinlets, respectively. The metallic minerals consist of pyrite, chalcopyrite, bornite, sphalerite, and tennantite-tetrahedrite, which are variably associated with gangue minerals including quartz, calcite, and sericite. The upper parts of the ores have been oxidized to form supergene minerals including malachite, azurite, chrysocolla, chalcocite, covellite, hematite, and goethite. The ore-related hydrothermal alteration includes silicification, pyritization, carbonatization, intermediate argillitization, and propylitic alteration. Primary fluid inclusion assemblages in quartz associated with main-stage sulfides and sulfosalts have homogenization temperatures ranging from 184° to 385 °C and calculated salinities between 12.0 and 29.7 wt% NaCl equiv. (avg. 21.4 wt% NaCl equiv.). The coexistence of fluid inclusion assemblages with highly variable volume percentages of vapor phase indicates that boiling commonly occurred in the hydrothermal system, contributing to Cu saturation. Sulfide minerals range in δ34S from −1.5 to 3.7 ‰, indicating a probable magmatic sulfur source. This view is further supported by the carbon and oxygen isotopes of hydrothermal carbonates, with δ13CPDB of −2.2 to −1.5 ‰ and δ18OSMOW between 5.30 and 11.75 ‰. Stable isotope and fluid inclusion data illustrate that boiling of the ore fluid and its mixing with meteoric water facilitated mineralization at the North Narbaghi. We suggest that the North Narbaghi Cu-Ag deposit can be best interpreted as an intermediate-sulfidation epithermal deposit formed due to post-Eocene magmatic-hydrothermal activity. The intersections of post-Eocene subvolcanic rocks with regional faults were the most favorable sites for focusing fluids responsible for epithermal mineralization along the UDMA.

An unconditionally stable, high-order and flux-conservative fluid–fluid coupling method

Stability has been an elusive issue for high-order time integration of two fluids coupled across an interface. Iteration between fluid domains can be used to enforce stability, but then there can be time step restrictions for the iterations to converge. The design of methods is complicated by additional properties like conservation of fluxes between fluids and multirate time stepping that are needed for applications. We propose and investigate an iterative approach that has no time step restriction to achieve a stable, multirate, flux-conservative and high-order accurate method for the fluid–fluid problem. Computational examples also illustrate a clear advantage for computing with large time steps, compared to another recent method.

Efficient and stable electrorheological fluids based on chestnut-like cobalt hydroxide coupled with surface-functionalized carbon dots.

Intrinsically polarized electrorheological fluids (ERFs) have better thermal stability than ERFs with polar molecules, so they have a broader application prospect. However, the electrorheological efficiency of the common intrinsically polarized ERF is still lower than 1500, which is related to the poor wettability between polarized materials and the continuous phase. Carbon dots (CDs) exhibit good stability, semiconductor properties and low toxicity. We prepared biomimetic chestnut-like cobalt hydroxide coupled with surface-functionalized CD particles (Co(OH)2@CDs) by a simple hydrothermal method. Then we prepared an ERF by mixing Co(OH)2@CDs with silicone oil and studied the effect of CDs on its rheology and electrorheology properties. The synergistic effect of the lipophilic groups on the surface of CDs and the biomimetic chestnut-like structure makes Co(OH)2@CDs exhibit good wettability with silicone oil, and the optimal zero-field viscosity of Co(OH)2@CDs-ERF is only 0.46 Pa s (particle mass fraction of 40%). Exceptional electrorheological efficiency (about 10 000, shear rate 0.1 s-1, 5 kV mm-1) and dynamic shear stress stability of optimal Co(OH)2@CDs-ERF can be attributed to the dielectric enhancement of the biomimetic chestnut-like structure coupled with the semiconductor properties of CDs. In addition, Co(OH)2@CDs-ERF has excellent anti-settling performance, outstanding thermal stability and low current density.

Pressure-Temperature-Fluid Constraints for the Formation of the Halo-Shakiso Emerald Deposit, Southern Ethiopia: Fluid Inclusion and Stable Isotope Studies

ABSTRACT The Halo-Shakiso emeralds were discovered near the town of Shakiso in southern Ethiopia in 2016. They are gem quality, Cr-dominant emeralds hosted within ultramafic rocks and associated with Cambrian pegmatite intrusions of the Adola Belt. Aqueous-carbonic primary fluid inclusions hosted within emerald have a composition of approximately 3.0 wt.% NaCl eq. and an XCO2 of 0.06, with minor amounts of N2, CH4, and H2S. Stable isotope thermometry of contemporaneous quartz and emerald yields temperatures in the range of 420 to 470 °C. Combined stable isotope and fluid inclusion data are consistent with emerald precipitation at pressures ranging from 2.0 to 3.0 kbar, corresponding to depths of 5.9 to 8.9 km. Additionally, emerald channel water δD and calculated δ18O isotope values are consistent with an igneous origin for the fluids responsible for emerald precipitation; these fluids are also responsible for the metasomatization of the host rocks in and near the pegmatite, forming the phlogopite schist that is host to the Halo-Shakiso emeralds. The isotopic signatures, combined with the occurrence of adjacent pegmatites, support the classification of the Halo-Shakiso emerald deposit as a Tectonic-Magmatic-Related emerald deposit.

The influence of thermal boundary conditions of wellbore on the heat extraction performance of deep borehole heat exchangers

The previous studies on the heat transfer characteristics of deep borehole heat exchangers (DBHE) were mainly numerical simulations due to the high cost of in-situ experiments. The thermal boundary conditions of the wellbore used in these numerical simulations can be divided into the following three categories: (a) Robin or mixed boundary condition where a stable fluid with constant inlet water temperature flows through a coaxial tube. (b) Neumann boundary condition of constant heat flux locally or averaged as a whole through the wellbore, and (c) Dirichlet boundary condition of constant wellbore temperature. In this paper, a numerical study on the heat extraction performance of the deep borehole heat exchanger is carried out, the model is verified by comparing the obtained results with the experimental or numerical simulation results reported in the literature, and the influences of three thermal boundary conditions on heat output that varies with time were analyzed. The results indicate that the Neumann boundary condition commonly used in the analysis of shallow borehole heat exchangers are not suitable for actual DBHE. Under Dirichlet boundary conditions, the thermal disturbance radius after 120 days of continuous heat extraction is the largest. In addition, stable heat outputs under different operating parameters was obtained.

The theme-recipient alternation in Chinese: tracking syntactic variation across seven centuries

AbstractPrevious research has tracked the history of the theme-recipient alternation (or: “dative” alternation) in Chinese, but few studies have embedded their analysis in a probabilistic variationist framework. Against this backdrop, we explore the language-internal and language-external factors that probabilistically influence the alternation between theme-first and recipient-first ordering in a large diachronic corpus of Chinese writing (1300s–1900s). Our analysis reveals that the recipient-first variant is consistently more frequent than its competitor and even more common in more recent texts than in older texts. Regression analysis also suggests that there are stable linguistic constraints (i.e., animacy and definiteness of theme) and fluid constraints (i.e., end-weight, recipient animacy). Notably, the diachronic instability of end-weight and animacy points to cross-linguistic parallels for ditransitive constructions, including the English dative alternation. We thus contribute to theory building in variationist linguistics by advancing the field’s knowledge about the comparative fluidity versus stability of probabilistic constraints.