Search Results (1,185)

Neutron gamma density (NGD) logging, as a safer and more environmentally friendly density logging method, has been applied in logging while drilling (LWD) for many years. However, most NGD algorithms have low density sensitivity and exhibit significant errors in the presence of gas and high-salinity water. To address the above issues, the inelastic gamma information of the drill collar is simulated by the Monte Carlo method, and its impact on NGD sensitivity and the results are studied. Using the drill-collar inelastic gamma information, a new neutron gamma density algorithm is proposed. The study shows that the drill-collar inelastic gamma information occupies a large proportion of the total inelastic gamma count recorded by the detector, which reduces the sensitivity of the NGD algorithms using the total inelastic gamma information. By eliminating the contribution of the drill collar from the total inelastic gamma count, the density sensitivity of the NGD algorithms can be significantly improved. In addition, the drill-collar inelastic gamma information is closely related to high-energy fast neutrons and can be used to correct the fast neutron distribution in NGD logging. The new NGD algorithm, utilizing the drill-collar inelastic gamma information, has excellent performance in the presence of gas and high-salinity water. However, similar to the other algorithms, the new algorithm is still affected by other environmental factors such as borehole, lithology, and shale. Furthermore, this new algorithm does not require any additional modifications to existing NGD tools and can work with other NGD algorithms. Full article

Energy transition has established hydrogen and compressed natural gas (CNG) as key alternatives for reducing greenhouse gas emissions and promoting sustainable mobility in the transport sector. However, the safe deployment of this infrastructure is essential to ensure that decarbonisation strategies remain environmentally, socially and operationally sustainable. Filling stations handling flammable gases may release hydrogen or CNG into open environments where ventilation alone cannot always prevent unacceptable risk situations in populated and industrial areas. Although the current regulatory framework sets out essential design requirements, including safety distances, this article argues that risk management must go beyond minimum compliance, reconsidering the location of detectors, gas dispersion behaviour and the definition of hazard zones. The analysis takes into account the rapid dilution of these gases under open air ventilation conditions and supports a more risk-based approach to infrastructure planning. Since gas supply facilities operating at 25 MPa, the hazard zone from the vehicle receptacle is estimated at 3 m for hydrogen and 1.7 m for CNG. These findings contribute to a safer and more sustainable transport energy infrastructure. Full article

Spaceborne spectrometers are key optical payloads for global and regional greenhouse gas (GHGs) monitoring. With the increasing demands for high-precision and high-efficiency monitoring, spectrometers are required to provide a wide swath, high spatial resolution, and high spectral resolution. However, existing spaceborne grating spectrometers still face a trade-off between swath width and spatial resolution. To address this issue, this paper presents the optical design and fabrication of an immersed-grating spectrometer for GHG monitoring. The proposed spectrometer achieves a swath width of 100 km and a spatial resolution of 3 km × 3 km while providing high spectral resolution. It operates in four channels centered at 0.76, 1.61, 2.06, and 2.30 μm, covering the O₂-A band and the main absorption bands of CO₂ and CH₄, with corresponding spectral resolutions of 0.04, 0.07, 0.09, and 0.10 nm, respectively. The four channels share a common slit, which reduces system volume and inter-channel spatial registration errors. Immersed gratings are used as the core dispersive elements, enabling high spectral resolution in a compact optical configuration. To correct the smile and anamorphic beam compression induced by high-angular-dispersion immersed gratings, a prism-based simultaneous correction method is proposed. Based on this method, the initial parameters of the dispersion module are determined, and the optical design of the spectrometer is completed. Large-sized immersed gratings with high groove density are precisely fabricated using holographic lithography and ion-beam etching, after which the spectrometer is aligned and tested. The test MTF at the Nyquist frequency of the spatial dimension exceeds 0.72, indicating good imaging quality. The test spectral resolution of the four channels is all better than the design value, and the maximum smile and trapezoidal distortion are both within one pixel. This spectrometer provides an effective technical solution for achieving wide-swath, high-spatial-resolution, and high-spectral-resolution GHG monitoring under constraints imposed by detector size, signal-to-noise ratio, and payload size and mass. Full article

Essential oils are natural products frequently subject to economically motivated adulteration with cheaper substances like vegetable oils, mineral oils, or organic solvents. This study developed and validated a rapid high-temperature gas chromatography with flame ionization detection (HTGC-FID) method for the simultaneous determination of high-boiling adulterants: triacylglycerides (vegetable oils) and medicinal white oil (mineral oil) in essential oils. The method utilizes on-column injection onto a DB-5 capillary column (30 m × 0.53 mm, 0.88 μm) with a temperature program from 60 to 380 °C and hydrogen carrier gas. Validation parameters demonstrated excellent linearity (R² = 0.9957–0.9978), high repeatability (content RSD < 3%), and sufficient sensitivity (LOQ of 0.03% for triacylglycerides, and 0.63% for medicinal white oil). The method was successfully applied to 20 commercial essential oils. While medicinal white oil was undetected, several samples contained triacylglycerides (up to 3.79%) and other adulterants (up to 52%). Significantly reduced response factors confirmed extensive adulteration in some products. The proposed HTGC-FID method represents a simple, cost-effective, and efficient tool for routine quality control, enabling direct quantification of high-boiling adulterants without tedious sample preparation. Full article

Radon is a naturally occurring radioactive gas present in soil, rocks, and water, and is one of the main sources of exposure to natural radiation. It is the second leading cause of lung cancer after smoking. An accurate assessment of indoor radon concentrations is therefore essential for radiation protection and risk management. This study presents a metrological analysis of indoor radon measurements performed using CR-39 nuclear track detectors exposed over varying exposure times. A dataset of 90 measurements was analyzed in accordance with ISO 11929 and ISO 11665-4, with particular attention to the combined use of measurement uncertainty and characteristic limits (decision threshold and detection limit). The results show that characteristic limits allow a statistically consistent discrimination between true radon signals and background fluctuations, while measurement uncertainty provides a quantitative description of the reliability of individual results. The combined interpretation of these quantities enables a more accurate assessment of the validity of the measurements, particularly for values close to the detection limit. In addition, a dimensionless Reliability Ratio (R), defined as the ratio of the measured concentration to the detection limit, is introduced as an operational indicator for evaluating the reliability of individual measurements and comparing results obtained under different exposure times. The proposed framework is demonstrated using real measurement data and highlights the practical role of metrological concepts in supporting decision-making processes in indoor radon risk assessment and mitigation strategies. Full article

Gas Electron Multiplier (GEM) detectors have become an indispensable component of modern tracking systems. The heart of a GEM detector is a thin polyimide foil (∼50 µm) clad with copper (∼5 µm) on both sides and containing an array of regularly spaced holes (typically diameter of ∼70 µm and pitch of ∼140 µm) fabricated using photolithographic techniques. The presence of the dielectric substrate (polyimide) within the amplification region introduces a time dependent response when the detector is exposed to external irradiation, a phenomenon commonly referred to as the charging-up effect. This effect arises from the accumulation of charge on the insulating polyimide surfaces, leading to a gradual modification of the local electric field configuration inside the GEM holes and, consequently, a variation in the detector gain over time. The charging-up behaviour has been systematically investigated for triple GEM chamber prototypes using an Fe-55 radioactive source (5.9 keV X-rays) with an activity of ∼20 mCi. The characteristic charging-up time constant has been extracted, and its dependence on detector gain and irradiation rate has been examined. In addition, the uniformity of detector performance in terms of count rate, gain, and energy resolution has been studied both before and after the charging-up process. In this review article, the experimental setup, data acquisition methodology, and analysis procedures developed and carried out by our group are summarised. The key findings reported by other groups, relevant Monte Carlo simulation efforts, and future outlook for the charging-up investigation on GEM based detectors are also discussed in this article. The investigations and their outcomes reviewed here provide valuable insight into the charging-up dynamics of GEM detectors and their dependence on operational parameters. Full article

Pixelated detectors based on inorganic scintillation materials are widely used in radiation detection systems for medical imaging and many other fields of science and technology. A substantial application is X-ray scanning using flat-panel detectors (FPDs) for both fluorography and mammography. In this article, the detection properties of the monolithic planar ceramic scintillation elements are reported for the first time. A high-light yield (Gd,Y)₃Al₂Ga₃O₁₂:Ce,Mg garnet-type scintillation material was used to form square-shaped pixels, while a material of similar composition was used as a substrate. Green bodies were successfully fabricated by a digital light processing (DLP) 3D printing method. Subsequent debinding and pressureless high-temperature sintering resulted in composite elements consisting of two layers with different chemical compositions. The lower bulk layer consisted of transparent, non-luminescent garnet, whereas the upper pixelated layer, with pixel dimensions of 230 × 230 µm, was made of scintillation material. The spatial resolution of the matrices under UV light and alpha-particle excitation was evaluated. It was confirmed that the spatial resolution of the matrices produced by the developed technology is approximately 0.4 times the pixel size. The proven ability of the integrated technology of inorganic scintillation matrix production opens the way for future improvement in spatial resolution through optimizing the printed pixel dimensions. Full article

The proliferation of AI-generated content and personalized AI systems has sharpened two fundamental and related computational problems: the progressive erosion of authentic identity in AI-mediated representations, and the growing difficulty of distinguishing human-originated from AI-generated behavioral and textual streams. This paper proposes a rigorous computational framework in which digital identity is formalized as a holomorphic function of complex time T = (a + ib) ∈ ℂ, where the real component Re$\left(T\right)$ encodes chronological progression and the imaginary component Im$\left(T\right)$ spans a continuum from episodic memory ($Im\left(T\right) < 0$) through the present moment ($Im\left(T\right) = 0$) to prospective imagination ($Im\left(T\right) > 0$). We argue that holomorphicity—enforced via Cauchy–Riemann regularization during CTNN learning (Proposition 1)—provides a theoretically grounded encoding of identity coherence, and discuss its advantages over alternative mathematical choices, including Lipschitz continuity, ${\mathit{C}}^{\mathbf{\infty }}$ smoothness, piecewise analytic functions, and stochastic models. Under four explicit Assumptions 1–4 covering the Markovian structure and fixed context window of current LLM architectures, we establish via Lemmas 1 and 2 and Theorem 1 that AI-generated behavioral trajectories exhibit structural limitations in satisfying the Cauchy–Riemann conditions at temporal depths characteristic of human biographical memory—limitations that do not arise for human trajectories learned under CTNN regularization. Building on this result, we introduce the Human–AI Authenticity Discriminant (HAAD), a theoretically grounded classifier with a fully specified calibration algorithm and sensitivity analysis ($\mathit{\kappa }$ ΔAUROC ≤ 0.04 over ±30% perturbation). Five metrics—TCS, ISI, PAS, GAS, and HAAD—are derived analytically from the holomorphic structure. The algorithmic framework is instantiated on four real-world datasets: MovieLens 25M, the Pushshift Reddit corpus, the Stack Overflow Data Dump, and the LIAR dataset. On the LIAR benchmark, TDT-HAAD achieves AUROC = 0.82 (95% CI: [0.79, 0.85]), exceeding a RoBERTa-based LLM detector baseline (AUROC = 0.75, DeLong p < 0.01); an ablation study supports the structural contribution of each component. A credibility harvesting signature is detectable 45.3 ± 12.1 days before standard temporal models reach statistical significance. Full article

Gallium oxide (Ga₂O₃) is emerging as a promising material for X-ray detectors due to its high sensitivity, high melting point, and stable physicochemical properties. However, intrinsic background shallow donors in raw materials hinder the preparation of high-resistance intrinsic crystals, making doping essential to tailor electrical properties. This study grew Ti³⁺-doped β-Ga₂O₃ single crystals via the Edge-defined Film-fed Growth (EFG) method using Ti₂O₃ as a dopant, achieving high resistivity and a moderate reduction in bandgap. High-resolution X-ray diffraction (HRXRD) showed a rocking curve full width at half maximum (FWHM) of 96.50 arcsec. Compared with the unintentionally doped (UID) crystal, the bandgap exhibited a slight reduction, decreasing from 4.76 eV to 4.59 eV. In the infrared transmission spectra, the onset wavelength of the decrease in transmittance for the Ti³⁺: β-Ga₂O₃ crystal showed a distinct redshift relative to that of the UID crystal, indicating effective suppression of free electrons within the crystal. X-ray photoelectron spectroscopy (XPS) revealed that Ti³⁺ incorporation minimally affected the valence states of Ga and O or the Ga/O ratio, with no significant shift in valence band maximum (EVBM). A metal–semiconductor–metal (MSM) structured X-ray detector fabricated on polished Ti³⁺: β-Ga₂O₃ (100) substrate with Ti/Au electrodes exhibited a peak sensitivity of 943.16 μC/(Gy·cm²) at 40 V bias and 2.944 μGy/s dose rate, surpassing the upper sensitivity limit reported for semi-insulating doping bulk β-Ga₂O₃ detectors. The rise and fall times were 0.23 s and 0.30 s, respectively, with a minimum detectable limit (MDL) of 164.26 nGy/s, demonstrating its potential for high-performance X-ray detection applications. Full article

Radon (²²²Rn) is a noble, radioactive gas and tends to be accumulated in poorly ventilated enclosed spaces. Mainly due to its radioactive daughters and the α-particles emitted, ²²²Rn poses a risk of cancer and therefore its concentration in air and water should be kept under certain reference levels. Several methods have been developed to accurately measure ²²²Rn concentration in water, using α, β or γ counting. A well-established, but not the only, method involves γ-spectroscopy using a High-Purity Germanium (HPGe) detector to identify the ²²²Rn decay isotopes ²¹⁴Pb and ²¹⁴Bi, assuming they are in secular equilibrium with ²²²Rn. This technique requires costly, bulky equipment due to the HPGe’s operation at −196 °C and the need for substantial shielding. The present study introduces a more affordable and compact device, utilizing CdZnTe (CZT) crystals, which provide exceptional energy resolution in the 300 to 600 keV range, with nearly eight times the Full Width at Half Maximum (FWHM) of HPGe. Four stacked CZT detectors, each containing a 0.5 cm³ crystal, were compared with measurements from an HPGe detector. Water samples were collected from boreholes and taps in a region where radon concentration in water ranged from 10 to 900 Bq/L. The results are promising for samples around 100 Bq/L, considering the potential advancements of the device with larger CZT detectors. Additionally, the method has the potential for in situ use due to its handheld capability. Full article

This paper presents the design, fabrication, and characterization of a sub-milliwatt graphene-based micro thermal conductivity detector (µTCD) that utilizes a suspended multilayer graphene (MLG) bridge to sense volatile organic compounds (VOCs) in the gas phase based on their thermal transport properties. The graphene bridge is transferred onto a silicon chip with integrated microchannels using a photolithography-free process. By incorporating microchannel designs, this approach enables precise transfer of suspended MLG dimensions without conventional patterning steps. A key innovation of this work lies in the use of an ultra-low thermal mass suspended graphene architecture, which significantly increases temperature rise per unit input power, thereby enhancing sensitivity per unit power compared to conventional metal-based TCDs. The fabricated µTCD successfully produces chromatograms of multiple VOC species, closely matching those obtained using a standard flame ionization detector (FID). The device demonstrates an estimated limit of detection (LOD) of 190 ppm while consuming an average power of 151 µW under DC operation. Full article

To realise high-speed free-space optical communication links in harsh space environments, it is crucial to consider the link’s operating wavelength, the performance of the optical receiver, and the radiation hardness of the avalanche photodiode (APD)—optical detectors in the optical receivers. In this work, we experimentally evaluated the radiation hardness of 2.5 Gb/s receivers based on InGaAs/AlGaAsSb APDs integrated with Ommic CGY2102UH/C2 transimpedance amplifiers. Proton energy (62 MeV) and fluence (up to 3.8 × 10¹⁰ p/cm²) representative of space environments were used to irradiate multiple receivers, ensuring rigour. After irradiation, the receivers maintained their avalanche gain and photocurrent, while exhibiting bandwidths exceeding 1.5 GHz. Despite a slight increase in APD’s dark current at high reverse bias, there was no degradation of the receiver’s bit error rate. At 2.5 Gb/s data rate and 1550 nm wavelength, the irradiated receivers achieved a bit error rate of 10⁻⁹ with an average optical power of −38.2 dBm, outperforming selected commercial receivers by ~3 dB. Since the displacement damage dose induced by the proton radiation levels used in this work are representative of those in Low Earth, Geostationary and Global Positioning System orbits, we demonstrated that InGaAs/AlGaAsSb APDs have sufficient radiation hardness to be employed as optical detectors of high-speed optical links in harsh space environments. Full article

The increasing adoption of alternative fuels such as hydrogen and ammonia in energy systems has created a growing need for advanced diagnostic techniques capable of monitoring combustion products with high specificity and flexibility. In this context, Raman spectroscopy represents a promising optical approach for gas analysis, as it enables the simultaneous detection of multiple species without requiring sample preparation. In this work, the performance of a cost-effective Raman-based system on quantitative detection of nitrogen oxides (NO and NO₂) and nitrous oxide (N₂O) is presented. The experimental setup is based on a multi-pass optical configuration designed to enhance the Raman signal and employs off-the-shelf components, including an uncooled CMOS detector. Calibration measurements were carried out using gas mixtures at known partial pressures, and gas concentrations were retrieved through a nonlinear least-squares fitting procedure applied to the measured spectra. The results show that the system provides linear and repeatable responses for NO and N₂O over the investigated pressure ranges, with low mean errors and limited data dispersion, while NO₂ performance could not be fully quantified in a comparable manner due to the high reactivity of the species under the tested conditions. Overall, the proposed system represents a viable and cost-effective solution for multi-species gas analysis in emerging combustion applications. This work aims to extend the industrial applicability of Raman spectroscopy to NO_x and NO₂ diagnostics. Full article

In this work, we report the fabrication and characterization of single-film and double-film composite epitaxial garnet structures based on single-crystalline films (SCFs) and bulk single-crystal (SC) scintillators for enhanced α–γ discrimination in mixed radiation fields. These composite scintillators consist of TbAG:Ce and YAG:Ce SCFs grown by liquid-phase epitaxy (LPE) on Czochralski-grown Gd₃Ga_2.5Al_2.5O₁₂ (GAGG:Ce) bulk SC substrates. Single- and double-film architectures were designed to optimize the energy absorption and pulse-shape discrimination (PSD) performance for low-penetrating α-particles and high-energy γ-rays. Energy calibration was performed using different γ-ray sources (⁵⁷Co, ⁵¹Cr, and ¹³⁷Cs), enabling the conversion of detector signals to a calibrated electron-equivalent energy scale (keVee). Integration gates were systematically optimized, yielding maximum figures of merit (FOM) of 1.4 for the GAGG:Ce SC substrate, 1.9 for the single-film composite, and 5.0 for the double-film composite, demonstrating a progressive improvement in α–γ discrimination with increasing structural complexity. Two-dimensional PSD density maps reveal well-separated α and γ events, with the highest separation observed for the double-film composite. These results indicate that the engineering of LPE-grown composites provides tunable scintillation decay profiles, enhanced temporal separation, and increased light yields, making them promising candidates for applications such as mixed radiation field detection, dosimetry, and radiation monitoring. Full article

The separation of chiral compounds is a challenging issue in various fields, e.g., biochemistry, the pharmaceutical industry, food chemistry, forensics, agriculture, etc. Very often, one of the two enantiomers can exhibit different activity. Therefore, the separation and analysis of enantiomers requires analytical methods for, e.g., quality control, pharmacokinetic studies, etc. Their separation is usually performed by high-performance liquid chromatography (HPLC), gas chromatography, supercritical fluid chromatography and microfluidic techniques such as capillary electrophoresis (CE), nano-liquid chromatography, and capillary electrochromatography (CEC). CEC is a modern analytical technique that combines the features of HPLC and CE (high selectivity and high chromatographic efficiency, respectively). The enantiomers are moved to the detector by an electroosmotic flow generated by the application of high voltage. In this review, the main features of CEC, and the basic principles of enantiomer separation are briefly summarized. Selected applications (appearing 2023–2026 February) employing packed capillaries, and monolithic and open tubular columns, are presented and discussed. Full article