Search Results (204)

Stress fields imparted with an ultrafast laser can correct low spatial frequency surface figure error of mirrors through ultrafast laser stress figuring (ULSF): the formation of nanograting structures within the bulk substrate generates localized stress, creating bending moments that equilibrize via wafer deformation. For ULSF to be used as an optical figuring process, the ultrafast laser generated stress must be effectively permanent or risk unwanted figure drift. Two isochronal annealing experiments were performed to measure ultrafast laser-generated stress stability in fused silica and Corning ultra-low expansion (ULE) wafers. The first experiment tracked changes to induced astigmatism up to 1000 °C on 25.4 mm-diameter wafers. Only small changes were measured after each thermal cycle up to 500 °C for both materials, but significant changes were observed at higher temperatures. The second experiment tracked stress changes in fused silica and ULE up to 500 °C but with 4 to 16× higher signal-to-noise ratio. Change in trefoil on 100 mm-diameter wafers was measured, and the induced stress in fused silica and ULE was found to be stable after thermal cycling up to 300 °C and 200 °C, respectively, with larger changes at higher temperatures. Full article

The inhibition of recrystallization in high-strain nickel-based single-crystal superalloys remains a critical challenge for advanced turbine blade applications. This study investigates the evolution of the primary γ’ phase and dislocation during annealing in a third-generation Re-containing single-crystal superalloy (WZ30) subjected to 5% compressive deformation. Isochronal annealing (700 to 1200 °C, 1 min) combined with scanning electron microscopy (SEM) and an electron backscatter diffraction (EBSD) analysis revealed a nonlinear variation of the geometrically necessary dislocation (GND) density, which reached a minimum of 1000 °C with 62.7% of the primary γ’ phase retained. Prolonged recovery annealing at 1000 °C for 10 h effectively inhibited recrystallization during subsequent solution heat treatment. This result provides a practical strategy for inhibiting recrystallization in single-crystal superalloys. Full article

Carsharing has long supported trip purposes typically made by private vehicles, with grocery shopping especially benefiting from the carrying capacity of a personal vehicle. BlueLA is a one-way, station-based electric vehicle (EV) carsharing service in Los Angeles aimed at improving access in low-income neighborhoods. We hypothesize that BlueLA improves grocery access for underserved households by increasing their spatial-temporal reach to diverse grocery store types. We test two hypotheses: (1) accessibility from BlueLA stations to grocery stores varies by store type, traffic conditions, and departure times; and (2) Standard (general population) and Community (low-income) members differ in perceived grocery access and station usage. Using a mixed-methods approach, we integrate walking and driving isochrones, store data (n = 5888), trip activity data (n = 59,112), and survey responses (n = 215). Grocery shopping was a key trip purpose, with 69% of Community and 61% of Standard members reporting this use. Late-night grocery access is mostly limited to convenience stores, while roundtrips to full-service stores range from 55 to 100 min and cost USD 12 to USD 20. Survey data show that 84% of Community and 71% of Standard members reported improved grocery access. The findings highlight the importance of trip timing and the potential for carsharing and retail strategies to improve food access. Full article

This study addresses the problem of locating urban green spaces. Public health policies encompass a set of activities aimed at protecting individuals’ physical integrity and well-being, where prevention plays a critical role at both individual and collective levels. Having green spaces in urban areas is essential for providing mental relaxation, stimulating social cohesion and supporting physical activity. However, deciding where to place these green spaces is challenging, as various types of information must be considered, and the impact of such decisions needs thorough evaluation and visualization. To tackle this issue, we propose a methodology that combines mathematical programming with Geographic Information Systems (GIS). GIS tools are crucial for capturing and incorporating real-world data, which supports the mathematical model and helps visualize solutions. Our proposed multi-objective model aims to maximize coverage and equity. We demonstrate the application of this methodology with a case study focused on Valencia, Spain, where 20 potential locations were identified, and five were selected. Full article

The recovery of radiation damage induced by 231-MeV xenon ions with varying fluence (from 5 × 10¹¹ to 2 × 10¹⁴ cm⁻²) in α-Al₂O₃ (corundum) single crystals has been studied by means of isochronal thermal annealing of radiation-induced optical absorption (RIOA). The integral of elementary Gaussians (product of RIOA spectrum decomposition) OK has been considered as a concentration measure of relevant oxygen-related Frenkel defects (neutral and charged interstitial-vacancy pairs, F-H, F⁺-H⁻). The annealing kinetics of these four ion-induced point lattice defects has been modelled in terms of diffusion-controlled bimolecular recombination reactions and compared with those carried out earlier for the case of corundum irradiation by fast neutrons. The changes in the parameters of interstitial (mobile component in the recombination process) annealing kinetics—activation energy E and pre-exponential factor X—in ion-irradiated crystals are considered. Full article

The aim of this paper is to develop a case study of the recent situation of a bike-sharing service in a chosen small urban area. Žilina is situated in northern Slovakia, with a population exceeding 80,000 and an area of 80.03 km². This study represents a complex analysis of the available data on a bike-sharing service, as well as data on bicycle rentals from a local provider. Both were processed by the QGIS software. First, the number of rentals and the attractiveness of the bicycle stations were evaluated, taking into account the seasons from 2019 to the end of the 2023 season. Spatial analysis, based on marking the availability of the isochrones of the 32 bike-sharing stations at the end of the season 2024, was conducted considering the map’s characteristics. The analysis was supplemented with a questionnaire survey of bike-sharing service users. This study provides an overall view of the recent situation of a bike-sharing service operating for five years in a small urban area with the intention of identifying deficiencies and improving the service for future system expansion. The originality of this paper lies in the processing of a wide dataset with an extensive set of control variables and the connection of spatial and non-spatial analyses. The approaches and results can serve as proposals for introducing or designing bike-sharing services in other small urban areas for researchers. Full article

Post-processing plays a vital role in the determination of the final structures and properties of oriented materials. As a sustainable candidate of oil-based poly(ethylene terephthalate), biobased poly(ethylene 2,5-furandicarboxylate) (PEF) reflects great promise in green fiber, film, and packaging applications, but it undergoes poor stress-induced crystallization (SIC) under tensile deformation, necessitating a post-processing technique to improve its crystallinity and stability. Here, the structural evolution of pre-stretched PEF under post heating after uniaxial deformation was monitored by online synchrotron X-ray diffraction/scattering, differential scanning calorimetry, and ex situ infrared spectroscopy. The results delineate the significantly enhanced crystallization of pre-deformed PEF that happened far below its cold crystallization temperature. Through the isochronous analyses of the temperature-dependent evolution of mechanical response, the mesophase, crystal structure, orientation factor, chain conformation, and interchain ═C−H···O═C hydrogen bonding, the molecular mechanisms of microstructural transition and oriented crystallization of pre-drawn PEF under post heating were clarified. This research can enhance the understanding of PEF crystallization in an oriented state and provide guidelines on the structural design and technical control for processing high-performance PEF-based materials. Full article

This study evaluated the allocation of residential detention tanks in the Alto da Boa Vista Condominium, Federal District, Brazil, using hydrological and hydraulic modeling using the PCSWMM software (version 7.6.3610). The objective was to investigate the impact of urbanization on local hydrology, considering the occurrence of erosive processes in the area. Critical points in the infrastructure and regions susceptible to flooding were identified. The methodology involved implementing residential detention tanks in different allocation scenarios, including the use of isochrones. Isochrones, which represent lines of equal concentration time in the drainage network, were employed to segment the basin into three main regions: upstream (ISO 1+2), central (ISO 3+4), and downstream (ISO 5+6). The isochrone-based scenarios enabled the assessment of the impact of concentrating residential detention tanks in these specific zones. Additionally, two other scenarios were analyzed: one with the residential detention tanks uniformly distributed throughout the basin and another without the presence of these devices. Finally, a scenario with a random distribution of residential detention tanks was tested, encompassing a total of 54 distinct configurations, to investigate the influence of different spatial arrangements on the basin’s hydraulic performance. The results indicated that the number of residential detention tanks installed is the main determinant for peak flow attenuation at the basin’s outlet. It was observed that, regardless of the distribution of the devices, whether in concentrated scenarios (upstream, central, and downstream, as defined by the isochrones) or in randomly distributed configurations, the results were similar. In all cases, installing residential detention tanks in more than 30% of the basin area resulted in an approximately 5% reduction in peak flow at the outlet. It is concluded that implementing residential detention tanks is an effective and feasible solution for sustainable stormwater management, significantly contributing to surface runoff control and peak flow mitigation in urbanized areas. Full article

The Xulaojiugou Pb–Zn deposit, situated in the eastern Xing’an-Mongolia Orogenic Belt (XMOB), represents a medium-scale Pb–Zn deposit in central Heilongjiang Province, NE China. The mineralization occurs mainly near the contact zone of porphyritic biotite granite, medium-grained monzogranite, and marble in the Early Cambrian Qianshan Formation. Orebodies exhibit typical skarn characteristics and are structurally controlled by NE trending faults. To constrain the metallogenic age, ore-forming processes, and sources of ore-forming materials, we conducted integrated geochemical analyses, Re–Os isotope dating, in situ sulfur isotope analysis, and trace element analysis. Five molybdenite samples provided a Re–Os isochron age of 184.6 ± 3.0 Ma, indicating Early Jurassic mineralization. In situ δ³⁴S values from 20 sphalerite and 9 galena samples ranged from 5.31‰ to 5.83‰, suggesting derivation of sulfur from a deep magmatic source. Trace element analysis of 42 spots from three sphalerite samples revealed formation temperatures of 248–262 °C, which are consistent with mesothermal conditions. Integrated with regional tectonic evolution, the Xulaojiugou deposit is genetically linked to medium-grained monzogranite emplacement and represents a typical skarn polymetallic deposit, which is genetically associated with the regional porphyry–skarn metallogenic system that developed during the Early Yanshanian (Jurassic) tectonic–magmatic event and was driven by the subduction of the Paleo-Pacific plate. Full article

A chaotic synchronization system based on two mutually injected semiconductor ring lasers (SRLs) is constructed and the synchronization performance is analyzed. First, based on the symmetric theory, three types of chaos synchronization, isochronal chaos synchronization between the same modes (ICSS), isochronal chaos synchronization between different modes (ICSD), and leader-laggard chaos synchronization between different modes (LLCSD) are identified. Then, the performance of the three types of synchronization is investigated by cross-correlation technology. The results show that, with the appropriate feedback and injection parameters, all three synchronization structures can achieve high-quality chaos synchronization. Among them, ICSS can achieve high-quality synchronization under various parameters, while ICSD and LLCSD require larger injection and feedback parameters to achieve a comparable synchronization quality. Finally, the impact of a parameter mismatch on three types of synchronization quality is studied, and the results showed that the LLCSD has a stronger robustness than ICSS and ICSD. Therefore, under larger injection and feedback parameters, LLSCD is the preferred structure for synchronization communication in SRL. The research results can provide a theoretical reference for the application of SRLs in chaotic secure communication. Full article

Fiber Bragg gratings are key components for optical fiber sensing applications in harsh environments. Microvoids, or so-called type III fiber Bragg gratings, fabricated using femtosecond lasers and the point-by-point technique, were characterized at high temperatures (>1100 °C). For this purpose, we monitored the spectral characteristics of the grating, as well as the evolution of the microstructure during a 30 min isochronal annealing process. This study allowed us to correlate the behavior of the microvoids with the spectral performances (amplitude, wavelength drift) of the sensors at very high temperatures. As the grating signal is being lost at increasing temperatures (above 1125 °C), the periodic array of microvoids becomes disordered and deformed, ultimately losing its periodic spacing. Full article

The Jinjingzui gold (Au) deposit is located in the central part of Edong, China. The theoretical gold reserves are large with significant potential for mining and future development. This deposit is the only Au-bearing deposit discovered in the Middle-Lower Yangtze River Valley Metallogenic Belt, which has existing ore bodies that are mainly diorite. Re–Os dating of molybdenite from the Jinjingzui deposit confirm that the deposit formed in the Lower Cretaceous period, with an isochron age of 138.5 ± 2.7 Ma. The geochemical data of the rocks indicate that the diorite contains 54.75% to 56.66% SiO₂, 5.68% to 8.94% Fe₂O₃, 2.05% to 2.19% MgO, and 1.06% to 1.08% TiO₂, and with enrichment of large-ion lithophile elements (e.g., Rb and Ba). High-field-strength elements U-Nb–Ti displayed strong negative anomalies. Six pyrites from the Jinjingzui Au deposit δ³⁴S_V-PDB(‰) ranged from −2.4% to −8.4%, with an average value of −3.1%, and ²⁰⁶Pb~²⁰⁴Pb, ²⁰⁷Pb~²⁰⁴Pb, ²⁰⁸Pb~²⁰⁴Pb contents ranged from 17.77–18.58, 15.48–15.67 to 37.91–39.05, with average values of 18.14, 15.59 and 38.49, respectively. These values indicate that the metallic components originated from the upper mantle and lower crust. The Re concentrations in the molybdenites are significantly higher than those in other ores within the district (847.91~2018.58 × 10⁻⁶), suggesting a significant mantle component was involved in the mineralization process. Full article

S-wave seismic data are unaffected by natural gas trapped in strata, making them a valuable tool to study evaporite facies comparing to P-wave data. S-wave seismic data were utilized to construct an isochronous framework and analyze evaporite facies by seismic sedimentology methods in the Quaternary biogenic gas-bearing Taidong area, Sanhu Depression, Qaidam Basin, NW China, with calibration from wireline logs, geochemical evidences, and modern analogs. Techniques of phase rotation, frequency decomposition, R (Red), G (Green), B (Blue) fusion, and stratal slices were integrated to reconstruct seismic geomorphological features. Linear and sub-circular morphologies, resembling those observed in modern saline pans such as Lake Chad, were identified. Observations from Upper Pleistocene outcrops of anhydrite and halite at Yanshan (east of the Taidong area), along with lithological and paleo-environmental records from boreholes SG-5, SG-1, and SG-1b (northwest of the Taidong area), support the seismic findings. The slices generated from the S-wave seismic data indicate a progressive increase in the occurrence of evaporite features from the K2 standard zone upwards. The vertical occurrence of evaporite facies in the Taidong area increases, which coincides with the contemporary regional and global arid paleo-environmental changes. The interpretation of Quaternary stratal slices reveals a transition from a freshwater lake to brackish, saline, and finally, a dry saline pan, overlaid by silt. This analysis provides valuable insights into locating evaporites as cap rocks for biogenic gas accumulation and also into mining the evaporite mineral resources in shallow layers of the Taidong area. Full article

To address the inadequacies of traditional Advanced Orbiting Systems (AOS) multiplexing algorithms in accommodating the networked and diverse transmission demands of space data, this paper proposes an efficient network AOS integrated multiplexing algorithm based on elastic time slots. The AOS network traffic is categorized into three types based on its characteristics, and a strongly scalable AOS integrated multiplexing model is established, which consists of a packet multiplexing layer, a virtual channel multiplexing layer, and a decision-making layer. For synchronous services, an isochronous frame generation algorithm and a periodic polling virtual channel scheduling algorithm are employed to meet the periodic transmission requirements. For asynchronous non-real-time services, a high-efficiency frame generation algorithm and a uniform queue length virtual channel scheduling algorithm are utilized to satisfy the high-efficiency transmission requirements. For asynchronous real-time services, an adaptive frame generation algorithm based on traffic prediction and a virtual channel scheduling algorithm based on comprehensive channel state are proposed. These algorithms optimize frame generation efficiency and dynamically calculate optimal scheduling results based on virtual channel scheduling status, transmission frame scheduling status, virtual channel priority status, and traffic prediction status, thereby meeting the high dynamics, low latency, and high efficiency transmission requirements. Additionally, a slot preemption-based elastic time slot scheduling strategy is proposed at the decision layer, which dynamically adjusts and optimizes the time slot allocation for the three types of traffic based on the current service request status and time slot occupancy status. Simulation results show that the proposed algorithm not only achieves lower average delay, fewer frame residuals, and higher transmission efficiency, but also maintains high stability under different working conditions, effectively meeting the transmission requirements of various types of space network traffic. Full article

This paper considers a target-defense game in an open area with one or two defenders as well as an intruder. The intruder endeavors to reach the boundary of the island, while the defenders strive to prevent that by capturing the intruder through contact. Islands, as closed areas, restrict the free movement of the defenders, since the defenders—represented by USVs—cannot traverse the target area directly. First, we are concerned with the barrier, which is the boundary of the winning zones, taking into account the impact of the target. For the initial states lying in the defenders’ winning zone, there exists a strategy for the defenders to intercept the intruder regardless of the intruder’s best effort, while for the initial states lying in the intruder’s winning zone, the intruder can always invade successfully. We propose a geometric method to construct the barrier analytically for two kinds of speed ratios. Then, by taking index functions into consideration, we present optimal strategies for the players after constructing the dominance regions when their initial states lie in different winning zones. Simulation results verify the effectiveness of the proposed method. This study can be extended to scenarios involving multiple defenders. Full article