Search Results (4,998)

In this work, Cu₂CoSnS₄ (CCTS) thin films were deposited on glass substrates by thermal evaporation and investigated for photovoltaic applications. The influence of substrate temperature, varied from 25 °C to 200 °C, on the structural, morphological, and optical properties of the films was experimentally studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) measurements. XRD analysis confirmed the formation of crystalline CCTS with a stannite structure and a preferential orientation along the (112) plane. SEM observations revealed rough and non-uniform surfaces accompanied by an increase in grain size with increasing substrate temperature. Room-temperature PL measurements indicated a band-gap energy of approximately 1.3 eV, suitable for photovoltaic applications, and confirmed the presence of secondary phases in the p-type stannite CCTS films. Despite the promising photovoltaic properties of CCTS, numerical studies on CCTS-based solar cells remain scarce in the literature. In this context, a numerical study of the CCTS-based solar structure grown on glass was also performed using SCAPS-1D, showing good agreement with experimental photovoltaic results and validating the simulation model. Replacing the glass substrate with silicon improved the device efficiency to 5.77%. Further optimization of the series and shunt resistances significantly enhanced the photovoltaic performance, achieving a power conversion efficiency of 16.77%, with FF = 52.94%, V_oc = 0.89 V and J_sc = 35.19 mA/cm². Full article

Defect calculations for semiconductors demand both large supercells and accurate electronic structures, posing a significant challenge to first-principles methods. Conventional density functional theory (DFT) with local or semi-local exchange-correlation functionals severely underestimates the band gap, whereas hybrid functionals such as HSE06 provide higher accuracy but at a substantially increased computational cost. In this work, we demonstrate that shell DFT-1/2, a self-energy correction method for electronic structure calculations, may be used jointly with HSE06 to reach the optimal efficiency as well as accuracy. In particular, indium phosphide (InP) was taken as an example. The shell DFT-1/2 method was utilized to yield accurate band structures with a 1.44 eV direct gap, without any empirical parameter. Subsequently, the portion of exact exchange was tuned to match the shell DFT-1/2 electronic structure in HSE06 calculations. The charge transition levels of various point defects in InP were derived using HSE06, and HSE06 and shell DFT-1/2 may be employed alternatively to yield the density of states for the defective supercells. Their consistency proves the feasibility of the complementary employment of the two methods, and this strategy is readily extendable to other semiconductor research. Full article

Weather radar calibration is essential for ensuring data consistency and quantitative precipitation estimation in X-band radar networks. Existing absolute calibration methods (e.g., metal sphere, horn antenna) suffer from high cost, poor timeliness, and difficulty in automation due to meteorological conditions and airspace restrictions, while spatiotemporal matching methods based on volume scan data suffer from interpolation and matching inaccuracies. To address these issues, this study proposes a collaborative calibration method for X-band radar networks based on opposing Range–Height Indicator (RHI) scans. The method uses a rigorously calibrated reference radar as a benchmark and performs opposing RHI scans with the radar under calibration to obtain synchronized observations within the spatial overlap region. Precise spatial matching is achieved using the nearest-neighbor algorithm based on beam-broadening cross-coverage thresholds, and bias is extracted using both the midline 9-point averaging method (midline method) and spatially constrained regional Statistics method (regional method). Based on a total of 58 sets of opposing RHI scanning cases conducted under stratiform precipitation, scattered precipitation, and weak cloud conditions, the results show that under conditions where echo continuity is maintained near the midline of stratiform and scattered precipitation, both the midline method and the regional method can obtain stable matching data. The midline method achieves a median correlation coefficient (0.821–0.942) higher than that of the regional method (0.860–0.872), and its bias standard deviation remains relatively stable (midline method: 1.39–2.20 dB; regional method: 2.61–3.16 dB). Continuous RHI calibration tests confirm that within a 30-min window, the fluctuation of the data matching correlation coefficient is less than 0.05, and the fluctuation of the bias mean is controlled within ±0.3 dB. Under weak cloud conditions, although the midline method can still achieve a high correlation coefficient, the correctness of its results still requires auxiliary validation through other calibration means. This study provides a relatively efficient and effective technical approach for the automated collaborative calibration of dense X-band radar networks. Full article

The development of efficient photocatalysts for hydrogen production is a key challenge for sustainable energy technologies. In this study, strontium titanate (SrTiO₃) was synthesized via a citrate-assisted sol-gel method and subsequently modified by deposition-precipitation using nominal HAuCl₄ precursor concentrations of 1.0, 1.5, and 2.0 mM. The resulting materials were characterized by XRD, Raman spectroscopy, UV-Vis diffuse reflectance spectroscopy, SEM with EDS, and X-ray fluorescence (XRF). Au incorporation did not produce detectable changes in the SrTiO₃ crystalline phase or its optical band gap, which remained at 3.19–3.20 eV. The additional absorption band centered near 550 nm was consistent with the localized surface plasmon resonance of metallic Au nanoparticles. Microscopy indicated increasing surface coverage and aggregation at the highest nominal precursor concentration. Under irradiation with a low-pressure Hg lamp, all Au-containing materials presented substantially greater H₂ evolution than pristine SrTiO₃, whereas the comparatively small differences among the Au-modified samples indicated an apparent activity plateau across the evaluated concentration range. Because the Au-associated absorption band near 550 nm lies outside the main 254 nm emission of the lamp and the SrTiO₃ band gap remained mostly unchanged, the enhanced H₂ evolution is consistent with improved interfacial charge separation in the Au/SrTiO₃ system. A Schottky-junction-mediated pathway is proposed based on the observed activity trends and the electronic properties reported for Au/SrTiO₃ interfaces, rather than to a plasmonic or band-gap-tuning effect. The selected STO/Au 2.0 mM material retained approximately 97% of its initial apparent H₂ evolution rate after three consecutive cycles, indicating favorable short-term activity retention. Overall, this comparatively simple synthesis route provides a practical baseline for investigating the influence of nominal Au precursor concentration on H₂ evolution over SrTiO₃. Full article

The controlled formation of coherent interfaces in lattice-mismatched II–VI semiconductor heterostructures remains challenging. In this work, ZnSe/ZnS laminar nanomaterials were synthesized by an ultrasound-assisted reverse micelle method to determine how ultrasonic power (150 and 200 W) and water-to-surfactant molar ratio (16:1, 32:1, and 48:1) jointly regulate morphology, crystal structure, lattice accommodation, optical response, and photoelectrochemical behavior. Higher ultrasonic power favored more clearly defined laminar morphologies, whereas increasing the water-to-surfactant ratio produced more heterogeneous growth domains. XRD and Raman spectroscopy confirmed the presence of zinc-blende ZnSe and ZnS phases and provided indirect evidence consistent with partial pseudomorphic lattice accommodation, with calculated mismatch values of 1.59–3.07%, compared with the theoretical value of 4.43%. The apparent optical band gap decreased from 3.39 to 3.06 eV at 200 W and from 3.34 to 3.04 eV at 150 W as the water content increased. Photochronoamperometry showed predominantly cathodic responses, whereas P1R1 exhibited an anodic response. These results establish ultrasonic power and micellar composition as coupled synthesis parameters for tuning lamellar growth, interfacial strain, and optoelectronic response in ZnSe/ZnS heterostructures. Full article

In femtosecond-laser processing of titania in water, light can induce reduction and oxidation simultaneously. We follow this redox energy partitioning, in this perspective, from colloidal titania synthesis to hot-electron devices. Femtosecond ablation/fragmentation of an aqueous anatase suspension (515 nm, 230 fs, $5\mathsf{\mu }$J, fluence $F\approx 25.5$ J cm⁻²/pulse at clamped intensity ∼${10}^{13}$ W cm⁻²) yields surface-reduced, Ti³⁺-rich bluish TiO_2−x, while the same optical breakdown generates reactive oxygen species (ROS), among them H₂O₂ and HO^• radicals, which compete by re-oxidising Ti³⁺. When the reduced titania is decorated with plasmonic nanoparticles (e.g., Au), an n-type plasmonic photo-electrode is realised: $sp$ hot electrons are injected over the Schottky barrier, while the deep d-band supplies oxidising holes. The oxygen evolution reaction (OER) proceeds in stages at potentials well above the formal $1.23$ V via the two-electron peroxide route (∼$1.77$ V) or, for sufficiently energetic holes, via the one-electron HO^• route (∼$2.7$ V). In a biased cell, H₂ evolves on Pt through the adsorbed (H₂⁺)_ad intermediate. The same Au/semiconductor physics on silicon enables sub-band-gap hot-electron photo-detection. Energy-level diagrams (flat-band and in-contact) and the $sp$- vs. d-band origin of the injected carriers are discussed. Full article

Ag-Ti₃SiC₂ composites are promising electrical contact materials, yet the atomic-scale interfacial behaviour between Ti₃SiC₂ and Ag remains poorly understood. Here, first-principles calculations were performed to investigate the interfacial stability, electronic structure, and alloying effects at the Ti₃SiC₂(0001)/Ag(111) interface. Surface-energy calculations for six terminations of Ti₃SiC₂(0001) show that the TiC(TiC) termination is preferred at low carbon chemical potential, whereas the TiC(TiSi) termination becomes the most stable once ΔμC exceeds −1.50 eV. Eighteen interface models combining the six terminations with three stacking sequences (OT, MT, and HCP) were constructed, and their work of adhesion (Wad) and equilibrium spacing (d₀) were determined by the Universal Binding Energy Relation and full structural relaxation. The HCP stacking is preferred for all terminations, and the C(TiC)-terminated HCP interface exhibits the highest work of adhesion among all configurations, with Wad = 9.25 J/m² at d₀ = 1.2 Å; relaxation enhances Wad by 10%–75%. Charge density, charge density difference, and partial density of states analyses reveal that the interfacial bonding is dominated by C 2p-Ag 4d hybridization accompanied by electron transfer from Ag and Ti atoms to the interfacial C atoms, which accounts for the adhesion hierarchy. Substitutional alloying with Cu, Ni, Zn, and Cr preferentially segregates into the interfacial Ag layer, where the defect formation energies, although positive, are the lowest, and Wad increases in the order Cu < Zn < Ni < Cr, reaching 11.0 J/m² for interfacial Cr, an enhancement of 19% over the pristine interface. The strengthening correlates directly with the filling of the dopant 3d band. These results provide theoretical guidance for the interfacial design of high-performance Ag-Ti₃SiC₂ electrical contact composites. Full article

In recent decades, due to the rapid development and application of wireless communication, flexible electronics, and smart devices, electromagnetic interference (EMI) and radiation pollution have been intensified, creating an urgent demand for efficient EMI shielding materials. Carbon nanostructures such as graphene and carbon nanotubes are considered promising candidates due to their excellent properties, such as high electrical conductivity, low density, large specific surface area, and flexibility. This work reports our recent results in the design and testing of polymer nanocomposites with irradiated hybrid carbon nanostructure (graphene/multi-walled carbon nanotubes) used as EMI shielding materials. Five representative composites with varying filler loadings (AH of 15% and AM1 of 20 wt%), thicknesses (0.208–0.48 mm), and e-beam irradiation doses (from 50 to 400 kGy) were systematically characterized using SEM, FTIR, TGA/DSC, and vector network analyzer (VNA) measurements in the S-band (2.65–3.90 GHz). The effects of different e-beam irradiation doses and hybrid carbon contents on conductive network construction, interface engineering, and porous or layered structures on EMI shielding performance are discussed. Experimental results show that all studied composites exhibited strong absorption-dominant behavior (SE_A), while the multiple reflection component (SE_M) was found to be negligible. Both filler loading and sample thickness significantly enhanced shielding performance, with a pronounced synergistic interaction observed between these parameters. A quadratic Response Surface Methodology (RSM) model was developed to correlate the total shielding effectiveness (SE_T) with thickness and filler content, yielding high predictive accuracy (R² > 0.96). The model enables efficient optimization of composite design for targeted shielding levels. Full article

Phishing remains the dominant initial-access vector in modern cyberattacks, yet Turkish-language resources for benchmarking phishing e-mail detectors are scarce and methodologically fragile. We first show that a publicly released Turkish phishing dataset—our own earlier one (v1; 7504 messages)—is pathological: after entity masking it collapses to seven phishing and one legitimate content templates, and 99.95% of sender addresses share one artificial pattern, so any classifier memorizes artifacts rather than phishing semantics. We introduce TurkPhish v2, a class-balanced corpus of 2653 Turkish e-mails built from a generation matrix crossing phishing themes, persuasion tactics, length bands, and stylistic registers; the matrix is encoded as LLM-ready prompts, while the released corpus is instantiated by a deterministic, anti-leakage template composer. Against the v1 pathologies, the corpus is clean: unique masked templates, no near-duplicates (maximum pairwise cosine 0.808), opening and punctuation views at chance (49.8–52.8%), and matched lengths (p = 0.999). We also report the residual these gates miss: class signal lives in a closed pool of intent sentences, so a zero-learning lookup rule reaches 0.928 macro F1 in distribution and 0.894 out of topic, outscoring five of the ten benchmarked detectors. In-distribution performance is therefore a ceiling artifact, not evidence of learned phishing semantics. Benchmarking ten detectors across classic machine learning, Turkish/multilingual transformers, and an instruction-tuned large language model, eight exceed 0.99 macro F1 in distribution and are statistically indistinguishable (McNemar, p > 0.05), whereas out of topic TF-IDF linear models lead (logistic regression 0.947, 95% CI [0.926, 0.966]; 0.959 under the body-only protocol we recommend to users of the corpus) and mBERT collapses (0.570). Because persuasion phrasing is shared across themes, this protocol measures transfer to unseen theme vocabulary rather than robustness to novel phrasing. The transformer deficit out of topic is, for two of three encoders, a thresholding rather than a ranking failure: mBERT retains 0.960 out-of-topic AUC while its recall at the default 0.5 rule falls to 0.263. The corpus, splits, generation framework, and the full leakage audit, including its negative results, are available for research use. Full article

To investigate photosynthetic physiological response mechanisms of rice (Oryza sativa L.) seedling leaves under drought stress, a pot experiment with controlled watering was conducted. Four treatments were applied—control (CK), mild drought (LD), moderate drought (MD), and severe drought (SD)—to four cultivars (H17B7, HY3015, LH1H, WNSM) at seedling stage. The results showed that, after drought stress, the morphological indicators and chlorophyll content of the four rice cultivars all showed decreased trend, but a compensatory effect appeared in some varieties under the LD treatment. As drought intensified, the chlorophyll fluorescence induction kinetics (OJIP) curves’ polyphasic rise was inhibited, mainly affecting the J-I and I-P phases. Under SD, the P-phase declined by 44.36%, 36.75%, 32.61% and 50.62% compared with CK, and positive L-band, K-band, and J-band. Chlorophyll fluorescence parameters showed dynamic changes. Most chlorophyll fluorescence parameters (e.g., F_v/F_m) decreased, whereas TR_o/CS_o and DI_o/CS_o exhibited cultivar-dependent variations. Principal components of the chlorophyll fluorescence parameters in seedling leaves of the four rice cultivars showed differences and were clearly distinguished. Plant height, chlorophyll content, etc., are highly significantly positively correlated with F_o, DI_o/CS_o, etc., as well as chlorophyll content with DI_o/CS_o. The OJIP/JIP-test responses suggest impairment of the PQ pool and downstream electron transport, with the extent of damage varying among cultivars. Full article

A novel distributed Transmission-Only Vector Network Analyzer (TVNA) based on two Six-Port Reflectometers (SPRs) is experimentally verified. The prototype distributed SPR-TVNA measures $S_{21}$ and operates with two independent RF sources, allowing the two ports of the Device Under Test (DUT) to be widely separated with no common cables coming to a central location. Using the distributed SPR-TVNA allows for measurements of, e.g., distantly separated antennas, or taking grain bin imaging measurements that would otherwise require long coaxial cables. A key issue of these large DUTs is accurate measurement of the through-measurement, $S_{21}$. The distribution (separation) of the two RF sources in the SPR-VNA requires novel procedures to obtain accurate results. The results are confirmed using simulations and experiments, with the experimental results obtained using custom-built hardware. While, in theory, a full VNA can measure $S_{11}$ and $S_{22}$, which is confirmed through simulation, the experimental results show significant errors in $S_{11}$ and $S_{22}$. We thus call the current device a Transmission-Only VNA. The fundamental math of the SPR-VNA means there is a ±180° phase uncertainty that must be solved, e.g., via a wide-band sweep looking for phase jumps. The experimental $S_{21}$ measurements of the prototype show maximum errors of 1.5 dB in magnitude and 6 degrees in phase over a bandwidth of 0.6–1.2 GHz. Full article

Public-sector organisations must often commit to AI adoption decisions before longitudinal performance data are available to inform them. This study introduces and preliminarily demonstrates a Delphi–PERT–Monte Carlo framework for probabilistic KPI estimation in public-sector AI projects, applied to Kazakhstan’s e-government environment. A three-round modified Delphi study was conducted with 20 domain experts (competence threshold K ≥ 0.70). The Technology–Organisation–Environment framework structured elicitation across three AI scenarios (S0: no AI; S1: partial automation; S2: advanced AI) and four KPIs: timeline, cost, risk detection, and process transparency. Categorical percentage-band responses were translated into PERT distributions via a documented band-to-midpoint mapping rule and simulated through 10,000 Monte Carlo iterations. All outputs reflect structured expert belief, not observed performance data. Under S2, timeline effects were directionally ambiguous (P50 = −0.5%; bootstrap 95% CI: [−5.0%, +13.5%]); cost was consistently positive (P50 = +13.7%), reflecting near-term implementation cost increases expected by 55% of panelists. Risk detection (P50 = +5.8%; CI: [+3.7%, +12.8%]) and transparency (P50 = +8.2%; CI: [+2.5%, +8.8%]) showed modest but stable positive effects. Round 3 returned 80% consensus acceptance. The framework provides a replicable, sensitivity-tested procedure for generating probabilistic planning inputs in expert-data-scarce contexts; the Kazakhstan case is its first Central Asian application. Full article

Primordial black holes (PBHs) in the asteroid-mass range, with typical masses ${10}^{17}\mathrm{g}\lesssim M\lesssim {10}^{23}\mathrm{g}$, have drawn significant recent attention as viable dark matter candidates. The peak frequencies of photons emitted via Hawking radiation from asteroid-mass PBHs range from infrared to $\gamma$-ray bands. We calculate expected local transit rates for extended PBH mass distributions that could comprise all dark matter. We evaluate prospects for detecting Hawking-radiated photons from local PBH transits through the inner Solar System and from PBH explosions in the far outer edges of the Solar System. We consider several existing and proposed ground-based and space-based instruments sensitive to photons from the radio band to ultrahigh-energy $\gamma$-rays. We find that the proposed instruments, such as the All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) satellite, can reliably detect PBH transits within $\mathcal{O}\left(0.1\mathrm{AU}\right)$ of the Earth, while the High Altitude Water Cherenkov (HAWC) observatory and Large High Altitude Air Shower Observatory (LHAASO) are both sensitive to PBH explosions out to $\mathcal{O}\left(0.1\mathrm{pc}\right)$ and $\mathcal{O}\left(0.5\mathrm{pc}\right)$, respectively. We conclude by specifically considering potential companion electromagnetic signatures in the case of a PBH explosion about ${10}^3\mathrm{AU}$ from Earth, which has been suggested as a potential source for the ∼220 PeV ultrahigh-energy KM3-230213A neutrino event observed by the KM3NeT collaboration in 2023. Whereas we find that the recent KM3NeT event would not have yielded detectable electromagnetic signals—due to its location on the sky, proposed distance from Earth, and the offline status of the HAWC observatory at that time—we demonstrate that future PBH explosions at comparable distances could yield electromagnetic signals measurable from Earth, depending on the alignment of the PBH burst with detector fields of view. Full article

The rapid expansion of terahertz (THz) communication, nondestructive testing and biosensing puts forward urgent demands for absorbers with switchable working bandwidth, yet parts of existing graphene-based absorbers adopt costly noble-metal backplanes and can hardly realize reversible narrow and broadband absorption conversion. In this work, a three-layer metamaterial absorber is designed, where low-cost tungsten replaces precious metals as reflective substrate, polyimide serves as intermediate dielectric and patterned graphene composes the top absorbing layer. The finite element method (FEM) is employed to investigate the synergistic modulation of THz absorption characteristics by graphene’s Fermi level (E_f) and relaxation time (τ) across the 0–6 THz frequency range. Simulation results reveal that increasing E_f from 0.1 eV to 0.9 eV effectively broadens the effective absorption range. At fixed E_f = 0.9 eV, dual discrete absorption peaks with peak absorptivity up to 99.8% emerge at τ = 0.1 ps, while reducing τ to 0.05 ps enables an ultrawide 2.5 THz high-efficiency absorption band (absorptivity ≥ 90%) including a 1.4 THz near-perfect absorption (absorptivity ≥ 99%) region. Benefiting from high geometric symmetry, the proposed structure exhibits polarization-insensitive absorption and stable performance for incident angles up to 60°. This numerical work provides design references for low-cost switchable THz absorbers. Full article

SrTiO₃/Nb₂O₅ composite materials with 1 and 10 wt.% Nb₂O₅ were prepared by a sol–gel route and characterized by XRD, Raman spectroscopy, SEM, BET, UV-Vis DRS, photoluminescence, and dielectric spectroscopy. The photocatalytic activity was evaluated via degradation of rhodamine B and tetracycline under UV and visible light. The addition of Nb₂O₅ resulted in a significant reduction in specific surface area (from 22.7 to 3.1 m²/g), a narrowing of the optical band gap (from 3.22 to 2.49 eV), and a decrease in photoluminescence intensity. Despite these changes, the photocatalytic performance decreased with increasing Nb₂O₅ content. For rhodamine B degradation, the UV rate constant fell from 0.0136 min⁻¹ for pristine SrTiO₃ to 0.0035 min⁻¹ for SrTiO₃/10% Nb₂O₅. The lower activity is mainly ascribed to the loss of active sites, surface carbonate formation, and enhanced non-radiative recombination at interface defects, which suppress charge transfer to the surface. The results demonstrate that careful control of the composite microstructure is essential for achieving efficient photocatalysis, even when heterojunction formation is thermodynamically favorable. Full article