Hasil untuk "Physics"

Pengli Lei, Baojian Ji, Jing Hou et al.

Reaction-bonded silicon carbide (RB-SiC) is the preferred material for space optical systems because of its low density and high specific stiffness. However, its hardness and multi-component properties lead to low efficiency and pit defects during the polishing process, making the fabrication of RB-SiC a significant challenge. This study proposes a high-efficiency and low-defect fabrication method for RB-SiC using center-inlet computer-controlled polishing (CCP). We first investigated the polishing efficiency and surface quality achieved with center-inlet and non-center-inlet liquids. The results show that the defect density under non-center-inlet conditions was positively correlated with process parameters, while fewer defects and higher efficiency could be achieved under center-inlet conditions. Additionally, the efficient removal and defect suppression mechanisms under the center-inlet condition were revealed based on machining force, heat, and defect characterization. Under center-inlet conditions, the friction coefficient is larger and stable, resulting in high removal efficiency. The macro–micro coupled analysis results show that pit defects are generated through the combined action of force and heat, which leads to the thermo-mechanical degradation and shedding of SiC particles due to the temperature increase in the machining zone. The results demonstrate that center-inlet CCP not only ensures sufficient abrasion at the polishing interface to achieve high removal efficiency but also significantly suppresses the processing heat, thereby resulting in a low-defect surface.

Hao Geng

Abstract The Karch-Randall braneworld provides a natural set-up to study the Hawking radiation from a black hole using holographic tools. Such a black hole lives on a brane and is highly quantum yet has a holographic dual as a higher dimensional classical theory that lives in the ambient space. Moreover, such a black hole is coupled to a nongravitational bath which is absorbing its Hawking radiation. This allows us to compute the entropy of the Hawking radiation by studying the bath using the quantum extremal surface prescription. The quantum extremal surface geometrizes into a Ryu-Takayanagi surface in the ambient space. The topological phase transition of the Ryu-Takayanagi surface in time from connecting different portions of the bath to the one connecting the bath and the brane gives the Page curve of the Hawking radiation that is consistent with unitarity. Nevertheless, there doesn’t exit a derivation of the quantum extremal surface prescription and its geometrization in the Karch-Randall braneworld. In this paper, we fill this gap. We mainly focus on the case that the ambient space is (2+1)-dimensional for which explicit computations can be done in each description of the set-up. We show that the topological phase transition of the Ryu-Takayanagi surface corresponds to the formation of the replica wormhole on the Karch-Randall brane as the dominant contribution to the replica path integral. For higher dimensional situations, we show that the geometry of the brane satisfies Einstein’s equation coupled with conformal matter. We comment on possible implications to the general rule of gravitational path integral from this equation.

Xueqian Gong, Zhanyuan Zhu, Li Guo et al.

Xishu Gardens, an exemplary narrative of classical Chinese gardens, faces challenges in preserving its commemorative spatial structures while accommodating modern visitors’ needs. While trajectory analysis is critical, existing studies struggle to interpret multi-dimensional perception-preference data owing to spatiotemporal mismatches in multi-source datasets. This study adopted an improved Ward–K-medoids hybrid clustering algorithm to analyze 885 trajectory samples and 34,384 synchronized data points capturing emotional valence, cognitive evaluations, and dwell time behaviors via panoramic digital twins across three heritage sites (Du Fu Thatched Cottage, San Su Shrine, and Wangjiang Tower Park). Our key findings include the following: (1) Axial bimodal patterns: Type I high-frequency looping paths (27.6–68.9% recurrence) drive deep exploration, in contrast to Type II linear routes (≤0.5% recurrence), which enable intensive node coverage. (2) Layout-perception dynamics: single-axis layouts maximize behavioral engagement (DFTC), free-form designs achieve optimal emotional-cognitive integration (WTP), and multi-axis systems amplify emotional-cognitive fluctuations (SSS). (3) Spatial preference hierarchy: entrance and waterfront zones demonstrate dwell times 20% longer than site averages. Accordingly, the proposed model synchronizes Type II peak-hour throughput with Type I off-peak experiential depth using dynamic path allocation algorithms. This study underscores the strong spatial guidance mechanisms of Xishu Gardens, supporting tourism management and heritage conservation.

Dong Li, Baoshi Jiang

The free-form single-layer reticulated shell structure has the characteristics of complex shape, a high degree of static indeterminacy, and difficult node positioning in the construction process, and the nodal deviations that may occur in the construction stage have a significant impact on the reliability performance of the structure. In order to evaluate the influence of the nodal deviation on the reliability performance of the structure in the process of shape optimization, this paper takes the free-form surface of the rectangular plane as the initial structure. Shape optimization is carried out with the objective function of minimizing the strain energy under the uniform vertical load, and the influence of the nodal deviation on the reliability performance of the optimized structure is performed by analyzing changes in the structural response’s probability density function (PDF). The elastic modulus, yield strength, and nodal deviation of the material were selected as the basic random variables, and the PDF of the structural response was calculated using the probability density evolution method. In the case of considering and ignoring the nodal deviation, respectively, the PDF of the maximum displacement response of the structure under the same iteration step is calculated and compared. The results indicate that compared with the initial structure, the reliability performance of the optimized structure is significantly less sensitive to node deviations.

Masoud Gazizadeh, Masoumeh Foroutan Koudehi, Hossein Fasihi et al.

In this work, an innovative ratiometric sensing platform was developed for the determination of methotrexate (MTX), an antifolate drug, a chemotherapy agent, and an immune system suppressant based on blue emission graphene quantum dots/Rhodamine B doped gold nanostars (B-GQDs/Au NSt-RB). The developed sensor was a dual-emission fluorescent probe with two major emission peaks at 440 nm (B-GQDs) and 580 nm (Au NSt-RB) by exciting at 330 nm. Based on the inhibiting effect of MTX on the system's fluorescence density, the stable ratiometric fluorescent probe was used for the rapid determination of MTX in aquatic solutions and spiked human serum samples. The results indicated good linear correlations over the logarithmic concentration range of 0.3 nM–50.0 μM. In addition, B-GQDs/Au NSt-RB can further realize highly sensitive detection of MTX with a low LOD value of 2.28 × 10−10 M. The RSD% values obtained for the intra-day and inter-day precision were 0.63–3.86 %. With recoveries of 98.2–100.1 % and 98.7–100.5 %, respectively. The short-term temperature and freeze-thaw tests confirmed the higher stability of the developed sensor. In addition, the calculated recoveries for MTX recognition in real samples were in the range of 98–102 %. These findings suggested the excellent potential of the ratiometric fluorescence B-GQDs/Au NSt-RB sensor for detecting MTX in real plasma samples.

Douglas Mol Resende, José Maria Franco de Carvalho, Bárbara Oliveira Paiva et al.

Plastic is a widely consumed material with a high decomposition time, occupying significant space in landfills and dumps. Thus, strategies to reuse plastic waste are imperative for environmental benefit. Plastic waste is a promising eco-friendly building material for cement-based composites due to its reduced specific gravity and thermal conductivity. However, this waste reduces the composites’ mechanical strength. This work aims to produce and evaluate lightweight concretes made with only lightweight aggregates and mostly recycled plastic aggregates. Initially, an optimized dosage approach for lightweight concrete is presented. The mixture proportion of the lightweight concrete was based on the performance of mortars with the complete replacement of natural aggregate by recycled polyethylene terephthalate (PET) aggregates. The PET aggregates showed irregular shapes, impairing workability and providing lightweight concretes with around 18% water absorption and 21% void index. However, the concretes presented significantly low-unit weight, approximately 1200 kg/m³. This work presented a structural lightweight concrete (ACI 213-R) using only lightweight aggregates and mostly plastic waste aggregate, with a compressive strength of up to 17.6 MPa, a unit weight of 1282 kg/m³, and an efficiency factor of 12.3 MPa·cm³/g. The study shows that with an optimum dosage, reusing plastic waste in concrete is a viable alternative contributing to environmental sustainability.

Igor P. Ivanov

Timescales spanning 24 orders of magnitude smaller than one second can be studied experimentally, and each range is packed with different physical phenomena. This rich range of timescales offers a great context for an innovative undergraduate physics course which introduces modern physics and technology from an unconventional perspective. Based on the author's experience in lecturing on these topics to different audiences, this paper proposes a syllabus of a semester-long timescale-based undergraduate physics course.

Qiong Wu, Haiyun Luo, Hao Wang et al.

A novel Hydrodynamic Cavitation-Assisted Oxygen Plasma (HCAOP) process, which employs a venturi tube and oxygen injection, has been developed for enhancing the production and utilization of hydroxyl radicals (·OH) in the degradation of organic pollutants. This study has systematically investigated the fluid characteristics and discharge properties of the gas–liquid two-phase body in the venturi tube. The hydraulic cavitation two-phase body discharge is initiated by the bridging of the cavitation cloud between the electrodes. The discharge mode transitions from diffuse to spark to corona as the oxygen flow rate increases. The spark discharge has the highest current and discharge energy. Excessive oxygen results in the change of the flow from bubbly to annular and a subsequent decrease in discharge energy. The effects of cavitation intensity, oxygen flow rate, and power polarity on discharge characteristics and ·OH production were evaluated using terephthalic acid as a fluorescent probe. It was found that injecting 3 standard liter per minute (SLPM) of oxygen increased the ·OH yield by 6 times with only 1.2 times increase in power, whereas<0.5 SLPM of oxygen did not improve the ·OH yield due to lower breakdown voltage. Negative polarity voltage increased the breakdown voltage and ·OH yield due to asymmetric density and pressure distribution in the throat tube. This polarity effect was explained by numerical simulation. Using indigo carmine (E132) as a model pollutant, the HCAOP process degraded 20 mg/L of dye in 5 L water within 2 min following a first-order reaction. The lowest electric energy per order (EEO) was 0.26 (kWh/m3/order). The HCAOP process is a highly efficient flow-type advanced oxidation process with potential industrial applications.

Ye.O. Antonenko, Y.V. Antonenko, D.O. Shtoda et al.

Relevance. The creation of antenna arrays for communication systems is an urgent task in the unmanned aviation industries, in particular, for video signal transmission systems. Also, the relevance of the work is due to the need to use directional or single-beam antennas for direction finding and radar systems. The purpose of the work. Theoretical and experimental verification of the possibility of using both single patch antennas and antenna arrays based on them for video signal transmission systems in the 5.8 GHz band. Optimization of the geometrical parameters of the radiator, at which the gain will be maximum. Solution of the problem of microwave power division for powering the antenna array elements. Materials and methods. The paper presents theoretical results of modeling the frequency and spatial-energy characteristics of a single radiator and a series of antenna arrays based on it. A comparative analysis of experimental and theoretical studies of the matching characteristics for a single radiator is carried out. Modeling and optimization of antenna parameters was carried out using the Ansoft HFSS commercial package. Results. A patch antenna in the form of an open ring was investigated. A series of designs of antenna arrays with linear and circular polarization of 5.8 GHz has been obtained for use in video signal transmission systems, for example, to implement the first-person view (FPV) control mode for unmanned vehicles. A power divider based on quarter-wave transformers is used to power the antenna array. It is shown that the gain of a single patch antenna can exceed 10 dB. An antenna array of 4 elements located in the nodes of a rectangular grid can have a gain of more than 16 dB. Conclusion. The proposed type of antennas is adapted for communication systems, in particular, video signal transmission at 5.8 GHz. Along with satisfactory spatial and energy characteristics, the proposed technical solutions are simple and suitable for mass production.

Petros Petrounias, Panagiota P. Giannakopoulou, Aikaterini Rogkala et al.

This study was based on the reduction of the extraction of natural resources and, at the same time, was focused on the use of by-products and various wastes in construction applications by following the principles of circular economy. Sterile natural rocks (limestones, basalts), industrial by-products (slags), hotel construction wastes (bathroom wastes) and electronic wastes (e-wastes) were tested for pervious concrete aggregates. For this reason, ten concrete specimens were prepared and tested petrographically, structurally, and physically. The physical properties of the tested raw materials directly depended on their petrographic characteristics and played crucial role for the permeability of the produced concrete specimens, for their mechanical behavior, and for the freeze–thaw test results. Generally, from this study, strong encouraging results were achieved as concrete made by variable wastes and by-products can be compatible for concrete production as they show similar performance both in the mechanical strength test and in the freeze–thaw test with those made by natural aggregates. Another goal of this study was to recommend to other researchers the extended use of by-products, construction wastes, and e-wastes as concrete aggregates for producing eco-friendly constructions.

Nadine I. Geldof, Rob A. van Hulst, Milan L. Ridderikhof et al.

Abstract Purpose The aim of this study was to investigate the result of hyperbaric oxygen therapy (HBOT) in women with treated gynaecological malignancies who suffer from late radiation-induced tissue toxicity (LRITT). Moreover, which symptoms of LRITT benefit most from HBOT was evaluated as well. Material and Methods An online literature search was conducted using PubMed; Embase and the Cochrane Library. Studies were included if the study examined gynaecological cancer patients who had been treated with radiotherapy, who suffered from LRITT and who subsequently received HBOT. In addition, the outcome measures were based on examining the effects of HBOT. Results Twenty-one articles were included. The study investigating proctitis reported an improvement and three out of four studies investigating cystitis reported decreased complaints in women treated for gynaecological malignancies. In addition, all studies reported improvement in patients with wound complications and fifty percent of the studies reported better Patient Reported Outcome Measurements (PROMS) in women with gynaecological malignancies. Finally, all studies, except one related to pelvic malignancies reported reduced prevalence of symptoms for cystitis and proctitis and all studies reported better PROMS. However, only eleven studies reported p-values, nine of which were significant. Conclusion This study demonstrated that HBOT has a positive effect in women with gynaecological LRITT. Within the included patient group, gynaecological cancer patients with wound complications seem to benefit most from this treatment compared to other late side effects of LRITT.

Xing Yang, Hang Wu, Zhenping Feng

In this paper, detailed flow patterns and heat transfer characteristics of a jet impingement system with extended jet holes are experimentally and numerically studied. The jet holes in the jet plate present an inline array of 16 × 5 rows in the streamwise (i.e., the crossflow direction) and spanwise directions, where the streamwise and spanwise distances between adjacent holes, which are normalized by the jet hole diameter (<i>x</i>_n/<i>d</i> and <i>y</i>_n/<i>d</i>), are 8 and 5, respectively. The jets impinge onto a smooth target plate with a normalized distance (<i>z</i>_n/<i>d</i>) of 3.5 apart from the jet plate. The jet holes are extended by inserting stainless tubes throughout the jet holes and the extended lengths are varied in a range of 1.0<i>d</i>–2.5<i>d</i>, depending on the jet position in the streamwise direction. The experimental data is obtained by using the transient thermochromic liquid crystal (TLC) technique for wide operating jet Reynolds numbers of (1.0 × 10⁴)–(3.0 × 10⁴). The numerical simulations are well-validated using the experimental data and provide further insight into the flow physics within the jet impingement system. Comparisons with a traditional baseline jet impingement scheme show that the extended jet holes generate much higher local heat transfer levels and provide more uniform heat transfer distributions over the target plate, resulting in the highest improvement of approximately 36% in the Nusselt number. Although the extended jet hole configuration requires a higher pumping power to drive the flow through the impingement system, the gain of heat transfer prevails over the penalty of flow losses. At the same pumping power consumption, the extended jet hole design also has more than 10% higher heat transfer than the baseline scheme.

Xiaoqiang Yu, Qian Zhang, Xin Liu et al.

Solar interfacial evaporation, featured by high energy transfer efficiency, low cost, and environmental compatibility, has been widely regarded as a promising technology for solar desalination. However, the interplay between energy transfer and water transport in the same channels suggests that the tradeoff between high efficiency and long-term stability inherently exists in conventional photothermal nanomaterials. We summarize state-of-the-art research on various anti-salt clogging photothermal microstructures as long-term stable interfacial solar evaporators for solar desalination. The review starts with an overview of the current status and the fundamental limit of photothermal materials for solar desalination. Four representative strategies are analyzed in detail with the most recent experimental demonstrations, including fluid convection enhancement, surface wettability engineering, energy-mass-path decoupling, and surface chemistry engineering. Finally, this article focuses on the challenges in anti-salt clogging solar interfacial evaporators and potential point-of-use applications in the future.

Valeria Nardelli, Valeria D’Amico, Mariateresa Ingegno et al.

The evaluation of cereal-based product contamination by pesticide residues is a topic of worldwide importance, and reliable analytical methods for official check analyses and monitoring studies are required for multi-residue analysis at trace levels. In this work, a validated multi-residual analytical method by gas-chromatography and tandem mass spectrometry coupled with a rapid QuEChERS procedure was used for the determination of 37 pesticides (pyrethroids, organophosphorus and organochlorine compounds) in 209 commercially available samples of cereals and 11 legumes, placed on the Italian market in 2018 and 2019, coming from different regions of Italy, eastern Europe, and some non-European countries. No pesticide traces were observed in the analyzed legume samples. A total of 18 cereal samples were found to be contaminated by at least one pesticide, with a concentration level higher than the corresponding quantification limit, but never exceeding the maximum level fixed in the European Regulations. This work is the first part of a surveillance study for pesticide control in food samples.

Bernard F. Schutz

This chapter sets the stage for the rest of the book by exploring the role of intuition as a tool to deepen understanding in Einsteinian physics. Drawing on examples from the history of general relativity, we argue that the development of physical intuition is a crucial goal in physics education in parallel with any mathematical development of a physics subject. This chapter is for readers who wish to learn how expert physicists think conceptually about their subjects to understand them plus readers who wish to see how we can introduce Einsteinian physics to students by developing their intuition as well as teaching them the mathematics.

Liisa M. Hirvonen, Klaus Suhling

Fluorescence lifetime imaging (FLIM) is increasingly used in many scientific disciplines, including biological and medical research, materials science and chemistry. The fluorescence label is not only used to indicate its location, but also to probe its immediate environment, via its fluorescence lifetime. This allows FLIM to monitor and image the cellular microenvironment including the interaction between proteins in their natural environment. It does so with high specificity and sensitivity in a non-destructive and minimally invasive manner, providing both structural and functional information. Time-Correlated Single Photon Counting (TCSPC) is a popular, widely used, robust and mature method to perform FLIM measurements. It is a sensitive, accurate and precise method of measuring photon arrival times after an excitation pulse, with the arrival times not affected by photobleaching, excitation or fluorescence intensity fluctuations. It has a very large dynamic range, and only needs a low illumination intensity. Different methods have been developed to advance fast and accurate timing of photon arrival. In this review a brief history of the development of these methods is given, and their merits are discussed in the context of their applications in FLIM.

Balakrishnan Saravanakumar, Chandran Radhakrishnan, Murugan Ramasamy et al.

In quest for cost-affordable but high performing supercapacitor (SC), we explored fabrication of electrode material of copper oxide (CuO) nanostructures using simple solution-based synthesis procedure and different surfactants. Here, we report the influence of the surfactants on the morphological and structural evolutions as well as energy-storage capacity of the CuO. As an SC electrode material, CuO exhibits considerably high specific capacity (51 mAhg−1 @ 1Ag−1), good rate performance (31 mAhg−1 @ 10Ag−1) and better cyclic stability. In addition, it has low charge transfer resistance (1.6 Ω), which is very important when performing charge–discharge at high current rates. These results are highlighting the way for its use in design of advanced CuO-based supercapacitor devices. Keywords: Copper oxide, Neutral electrolyte, Surfactant, Supercapacitor

Hyeong-Seok Oh, Chan-Bae Park, Seung-Hwan Lee et al.

In this paper, to complement the capability of the existing heating system using an electric-heating wire for melting snow and ice in railway turnouts, 250kHz-200W-class Induction Heating (IH) system was designed. The IH system consists of the resonant inverter and the IH device. In order to perform the electric circuit, the electromagnetic field, and the thermal analysis, the Multi-Physics analysis for IH system was derived. In addition, IH system was compared with the existing heating system.

Robert J. Scherrer

In the Ijjas-Steinhardt cyclic model, the universe passes through phases dominated by radiation, matter, and a dark energy scalar field, with the value of the scale factor increasing with each cycle. Since each cycle terminates in a finite time, it is straightforward to calculate the fraction of time that the universe spends in a state for which the matter and dark energy densities have comparable magnitudes; when this fraction is large, it can be taken as a solution of the coincidence problem. This solution of the coincidence problem requires a relatively short lifetime for each cycle, but unlike in the case of phantom models, there is no fixed upper bound on this lifetime. However, scalar field models satisfying the Swampland conjectures yield sufficiently short lifetimes to provide a satisfactory resolution of the coincidence problem.

M. Cepeda, S. Gori, P. Ilten et al.

The discovery of the Higgs boson in 2012, by the ATLAS and CMS experiments, was a success achieved with only a percent of the entire dataset foreseen for the LHC. It opened a landscape of possibilities in the study of Higgs boson properties, Electroweak Symmetry breaking and the Standard Model in general, as well as new avenues in probing new physics beyond the Standard Model. Six years after the discovery, with a conspicuously larger dataset collected during LHC Run 2 at a 13 TeV centre-of-mass energy, the theory and experimental particle physics communities have started a meticulous exploration of the potential for precision measurements of its properties. This includes studies of Higgs boson production and decays processes, the search for rare decays and production modes, high energy observables, and searches for an extended electroweak symmetry breaking sector. This report summarises the potential reach and opportunities in Higgs physics during the High Luminosity phase of the LHC, with an expected dataset of pp collisions at 14 TeV, corresponding to an integrated luminosity of 3 ab$^{-1}$. These studies are performed in light of the most recent analyses from LHC collaborations and the latest theoretical developments. The potential of an LHC upgrade, colliding protons at a centre-of-mass energy of 27 TeV and producing a dataset corresponding to an integrated luminosity of 15 ab$^{-1}$, is also discussed.