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Quantum thermocouples: nonlocal conversion and control of heat in nanostructures
No full textNanoscale conductors are interesting for thermoelectrics because of their particular spectral features connecting separated heat and particle currents. Multiterminal devices in the quantum regime benefit from phase-coherent phenomena, which turns the thermoelectric effect nonlocal, and from tunable single-particle interactions. This way one can define quantum thermocouples which convert an injected heat current into useful power in an isothermal conductor, or work as refrigerators. In addition, efficient heat management devices can be defined. We review recent theoretical and experimental progress in the research of multiterminal thermal and thermoelectric quantum transport leading to proposals of autonomous quantum heat engines and thermal devices
Case Study on Effect of Climate Factors on HVAC Energy Consumption in Residential Buildings
No full textThe environmental climate factors have significant impact on building equipment energy consumption, especially in regions with hot summers and cold winters, where building energy consumption patterns are substantially influenced by seasonal climate variations. This research analyzed the actual energy consumption data of a residential building’s HVAC system from July 2023 to February 2024. The Random Forest method was applied to analyze the influence of weather variables on HVAC system energy consumption. K-means clustering was used to categorize energy consumption patterns into high, medium and low and energy consumption characteristics in according to the weather variables in each pattern were analyzed. The results show that: (1) Temperature exerts the greatest influence on the energy consumption of building HVAC system, followed by solar radiation and humidity. (2) The distribution of three high- medium-low energy consumption modes shows significant seasonal characteristics, among which the moderate energy consumption mode is the main contributor to the total energy consumption of HVAC systems. (3) Building HVAC high energy consumption level is mainly driven by the weather conditions of high temperature and intense solar radiation in summer and low temperature with weak solar radiation in winter; Medium energy consumption is commonly seen during summer cooling and winter heating periods, when the HVAC system needs to be switched on but does not require high load operation; Low energy consumption normally corresponds to mild climatic conditions
Fabrication of Dimensionally Stable Rice Husk Biochar Composites and Their Mechanistic Insights into Cu
No full textTo address the challenges of dust emission and poor recoverability associated with conventional powdered biochar, a dimensionally stable and recyclable biochar composite (PCL–CMC@RHB) was fabricated using rice husk biochar (RHB) as the carbon matrix, polycaprolactone (PCL) as a binding polymer, and sodium carboxymethyl cellulose (CMC) as a pore-forming and co-binding agent. The structural morphology and adsorption mechanisms were systematically examined through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The PCL–CMC coating significantly improved the mechanical integrity and interfacial compactness of RHB while preserving its intrinsic porosity and reactive surface chemistry. Kinetic analysis revealed that the Cu²⁺ adsorption process followed a pseudo-second-order model (R² ≈ 0.999), indicating chemisorption as the dominant mechanism. The optimized composite achieved a maximum Cu²⁺ adsorption capacity of 34.4 mg g⁻¹ and a removal efficiency exceeding 96 %, comparable to that of pristine RHB (35.8 mg g⁻¹, ≈ 97 %). These results confirm that polymer incorporation enhanced structural stability without compromising adsorption performance. Moderate PCL–CMC loadings optimized both accessible surface area and reactive site density, maximizing Cu²⁺ uptake and recyclability. FTIR spectra further demonstrated the formation of stable Cu–O coordination complexes through surface complexation and ion-exchange reactions. This study establishes a scalable strategy for engineering dimensionally stable biochar composites that combine high adsorption efficiency, mechanical durability, and environmental reusability—offering a sustainable platform for heavy-metal remediation in water and soil systems.
Study on the Influence of Acrylic-Acid Addition Mode on the Performance of Polycarboxylate Slump-Retaining Superplasticizers
No full textThe study employed ethylene glycol monovinyl ether (EPEG) as the primary monomer and utilized a redox initiation system comprising hydrogen peroxide, ferrous sulfate, ascorbic acid, and mercaptoethanol. Through aqueous-solution free-radical polymerization, a polycarboxylate slump-retaining superplasticizer was synthesized. The research focused on the addition mode (pre-addition to the base mixture versus supplemental dosing in the liquid phase) and dosage of acrylic acid (AA), evaluating their effects on cement paste flowability, concrete expansion‑retention performance, and compressive strength. The results indicated that when AA was pre-added to the base mixture at a proportion of 30 % and the total acid‑ether ratio was set to 2.9, the resulting polycarboxylate slump-retaining agent achieved the optimal cement paste flow, the best concrete slump‑retention behavior, and the highest compressive strength
Policies for Sponge City Transformation in China's Old Urban Areas and Analysis of Construction and Development Dynamics
No full textAfter a period of conceptual introduction, pilot exploration, and demonstration and promotion, the sponge transformation of old urban areas in my country has entered a phase of nationwide implementation. With the continuous introduction of supportive policies from national and local governments, the institutional framework for sponge transformation in my country's old urban areas has gradually improved, but implementation still faces certain bottlenecks. This article systematically reviews policy documents and construction data, analyzes the policies and practices supporting this transformation, and offers targeted recommendations. The study finds a positive correlation between the intensity of policy support and the effectiveness of transformation in different regions, with Tianjin, Inner Mongolia, and Jilin making rapid progress, while Tibet and Ningxia lag behind. Financial and credit support accounts for the highest proportion (24.53%), reflecting a common bottleneck for transformation across regions. Project operation and maintenance support accounts for the lowest proportion (3.46%), primarily concentrated in northern China, indicating that insufficient post-project operation and maintenance is a prominent shortcoming. Current bottlenecks include an incomplete policy system, a significant funding gap, an inadequate third-party evaluation mechanism, and insufficient internal motivation among transformation entities. Recommendations include improving the policy and standard support system, developing diversified financing mechanisms, and establishing a full-cycle management system for transformation to facilitate the high-quality development of sponge transformation in old urban areas
Study on the Effects of Soft Soil curing agent on the Properties of Different Soils
No full textThis study systematically evaluates the engineering performance improvement of Soft Soil curing agent on four typical special soils: demolition waste, marine mud, shielded soil, and nuclear power station soil. Results indicate that without the addition of stabilizer, these soils exhibit poor workability, low strength, or setting difficulties; specifically, demolition waste remains unsetting with extremely low strength (0.11 MPa at 7d), marine mud suffers severe bleeding and fails to set even after 28 days, while shielded soil and nuclear power station soil demonstrate slow setting and insufficient early strength. With increased stabilizer dosage (10%–30%), significant improvements in flowability are observed, along with markedly shortened initial and final setting times, and linear growth in unconfined compressive strength. Notably, bleeding is completely inhibited in marine mud when the dosage reaches ≥20%. Although shielded soil contains foam agents that delay hydration, high dosages can still accelerate the reaction. For nuclear power station soil, the strength peaks around a dosage of 20%. This technology not only solves the difficult problem of special soil solidification but also achieves resource conservation and environmental emission reduction, demonstrating significant economic and environmental benefits
How do recollimation-induced instabilities shape the propagation of hydrodynamic relativistic jets?
No full textContext. Recollimation is a phenomenon of particular importance in the dynamical evolution of jets and in the emission of high-energy radiation. Additionally, the full comprehension of this phenomenon provides insights into fundamental properties of jets in the vicinity of the active galactic nucleus (AGN). Three-dimensional (3D)(magneto)hydrodynamic simulations revealed that the jet conditions downstream of recollimation shocks favor the growth of strong instabilities, challenging the traditional view – supported by two-dimensional (2D) simulations – of confined jets undergoing a series of recollimation and reflection shocks.
Aims. In order to investigate the stability of relativistic jets in AGNs at recollimation sites, we performed a set of long duration 3D relativistic hydrodynamic simulations, to focus on the development of hydrodynamical instabilities. We explored the nonlinear growth of the instabilities and their effects on the physical jet properties as a function of the initial jet parameters.
Methods. We performed 2D and 3D relativistic hydrodynamic simulations using the state-of-the-art PLUTO code. We assumed that an initially free-expanding jet is collimated by the external medium, and we explored the role of the jet Lorentz factor, temperature, opening angle, and jet-environment density-contrast in the jet deceleration and entrainment. The parameter space was designed to describe low-power, weakly magnetized jets at small distances from the core (around the parsec scale).
Results. All of the collimating jets that we simulate develop instabilities. Recollimation instabilities decelerate the jet, heat it, entrain external material, and move the recollimation point to shorter distances from the core. This is true for both conical and cylindrical jets. The instabilities, which are first triggered by the centrifugal instability, appear to be less disruptive in the case of narrower, denser, warmer, and more relativistic jets. These results provide valuable insights into the complex processes governing AGN jets and could be used to model the properties of low-power, weakly magnetized jetted AGNs
Looking into the faintEst WIth MUSE (LEWIS): Exploring the nature of ultra-diffuse galaxies in the Hydra-I cluster
No full textContext. As some of the oldest stellar systems in the Universe, globular clusters (GCs) are key fossil tracers of galaxy formation and interaction histories. This paper is part of the LEWIS project, which provides the first homogeneous MUSE integral-field spectroscopic survey of a complete sample of ultra-diffuse galaxies (UDGs) in the Hydra I cluster.
Aims. We use MUSE spectroscopy and new VIRCAM H-band imaging data to study the GC populations and dark matter content in four dwarf galaxies from the LEWIS sample, which were found to host several GC candidates based on previous photometric studies.
Methods. We retrieved line-of-sight velocities (LOSVs) for all the sources in the observed MUSE fields and classified them based on their spectral features and LOSVs. Because the spectroscopic measurements are limited to relatively bright sources (mH ≲ 23.5 AB mag), we developed a multi-band photometric procedure to identify additional GC candidates that are too faint for spectroscopic confirmation. GC candidates were selected based on a combination of photometric properties (colors, magnitudes) and morphometric criteria (shape and size). The same selection criteria were applied to empty fields to estimate a statistical background correction for the number of identified GC candidates. Additionally, H-band observations were used to constrain the stellar masses of the studied galaxies.
Results. Based on the spectroscopic classification, we confirm one GC in UDG 3, two in UDG 7, and four in UDG 11, while UDG 9 has no spectroscopically confirmed bright GCs. We identify four intracluster GCs in the vicinity of UDG 3 and UDG 11, and one ultra-compact dwarf (UCD) with a radial velocity only −85 ± 10 km/s different from that of UDG 7 and thus possibly bound to it. Considering the completeness correction and accounting for possible contamination by unresolved background galaxies, from the photometry we estimate that the number of GCs ranges between 0 and ∼40 for the investigated UDGs. Their specific frequencies suggest that three out of four UDGs are either GC rich, similar to those in the Coma cluster, or belong to an intermediate population, as seen in the Perseus cluster. Dark matter content estimates, inferred from GC counts and stellar mass, indicate that these galaxies are dark matter dominated, with dynamical-to-stellar mass ratios ranging from ∼10 − 1000
A deep X-ray look to the most obscured quasar at
No full textContext. The most luminous and obscured quasars (QSOs) detected through sensitive infrared all-sky surveys are thought to represent a key co-evolutionary phase from nuclear to circumgalactic (CG) scales in the formation of massive galaxies. In this context, hot dust obscured galaxies (hot DOGs) in the redshift interval z ∼ 2 − 4 (the so-called cosmic noon) provide unique opportunities to investigate the relation between cosmic mass assembly and the nuclear accretion processes of luminous QSOs and galaxies at high-z. W0410−0913 (hereafter W0410−09) is a luminous (Lbol ∼ 6.4 × 1047 erg s−1) and obscured QSO at z = 3.631 that is characterized by a 30 kpc CG Lyα nebula (CGLAN), which is rather small when the ∼ 100 kpc Lyα nebulae around the unobscured QSO is compared to the Type I QSO peers, and by an exceptional overdense environment of Lyα emitters (LAEs), with ∼19 of them located in the CG region with a radius of 300 kpc at a distance of ±200 km s−1 from the Hot DOG.
Aims. Our aim is to detect and characterize active nuclear accretion in the Hot DOG W0410−09 and its environment.
Methods. We carried out this study by exploiting a deep proprietary ∼280 ks Chandra X-ray Observatory observation. We employed a set of empirical models suited for obscured sources and physically motivated spectroscopic models to account for a toroidal X-ray obscurer and the reprocessing of the X-ray radiation.
Results. The source W0410−09 consistently exhibits nuclear obscuration levels from mild to high star formation; it is Compton-thick (CT) and has a hydrogen column density of NH > 1024 cm−2 (and up to NH ∼ 1025 cm−2) and an intrinsic luminosity of L2 − 10 > 1045 erg s−1. W0410−09 is therefore one of the most luminous and obscured QSO at z > 3.5 discovered so far. This level of obscuration and the highly accreting nature of the Hot DOGs suggest that W0410−09 is undergoing a blow-out phase. This phase is predicted by models of merger-driven QSO formation scenarios, where strong winds begin to clear the dusty obscuring medium from the nuclear surroundings. We speculate that this heavy nuclear obscuration limits the amount of UV disk emission that powers its CGLAN, which in turn likely explains its small nebula size. Except for W0410−09, we detected no X-ray emission from any of the 19 LAEs. We analyzed their combined emission in several bands and only found a significant signal at the 3σ level in the 6−7 keV rest-frame energy band. We interpret this as caused by the Fe Kα line. This strongly suggests heavily obscured but so far undetected active galactic nuclei (AGN) emission in several LAEs. Considering W0410−09, we estimate an AGN fraction of . This value can reach ∼35% when we account for unresolved obscured AGN, as suggested by the detection of the Fe Kα line.
Conclusions. W0410−09 is powered by an intrinsically luminous CT quasar. Its high obscuration likely explains the limited extent of its CGLAN. Our analysis suggests that this object is in a crucial transitional blow-out phase, during which powerful QSO-driven outflows will sweep out the nuclear obscuration to pave the way for an unobscured bright quasar
Strategic mine method transformation to enhance marginal gold deposits and extend mine life
No full textThe economic viability of marginal gold reserves remains a major challenge in the final stages of mining operations, particularly when constrained by underground mining methods. This study investigates a strategic transition from underground to open-pit mining to enhance the economic potential of marginal gold deposits and extend the overall life of mine. Focusing on a gold mine approaching depletion, the research evaluates the technical, economic, and operational implications of converting the mining method to access previously uneconomic ore zones. A comparative analysis was carried out between underground and open-pit scenarios using parameters such as stripping ratio, recovery factor, cut-off grade, and Net Present Value (NPV). A sensitivity analysis was also conducted to assess the influence of gold price, mining cost, and ore grade on project feasibility and risk. The results demonstrate that transitioning to open-pit mining significantly increases recoverable reserves by reclassifying marginal zones as economically viable, leading to improved project NPV and extended life of mine. In addition to economic benefits, the transformation supports operational continuity and improved resource utilization. Nevertheless, geotechnical stability, environmental management, and regulatory compliance remain critical aspects to be addressed in implementing such a transition