Search Results (44)

The output energy of Laser Active Optical Systems (LAOSs), in which image brightness is amplified within the laser-active medium, is always higher than the input energy. This contrasts with conventional optical systems (OSs). As a result, a LAOS enables the creation of laser beams with tailored energy distribution across the aperture, making them ideal for material processing applications. This concept was first successfully implemented using metal vapor lasers as the gain medium. In these systems, material processing was achieved by using a laser beam that either carried the required energy profile or the image of the object itself. Later, other laser media were utilized for LAOSs, including barium vapor, strontium vapor, excimer XeCl lasers, and solid-state media. Additionally, during the development of these systems, several modifications were introduced. For example, Space-Time Light Modulators (STLMs) and CCD cameras were incorporated, along with the use of multipass amplifiers, disk-shaped or thin-disk (TD) solid-state laser amplifiers, and other advancements. These techniques have significantly expanded the range of power, energy, pulse durations, and operating wavelengths. Currently, TD laser amplifiers and STLMs based on Digital Light Processor (DLP) technology or Digital Micromirror Devices (DMDs) enhance the potential to develop LAOS devices for Subtractive and Additive Technologies (ST, AT), applicable in both macromachining (cutting, welding, drilling) and micro-nano processing. This review presents comparable characteristics and requirements for these various LAOS applications. Full article

Electric ducted fans are gaining prominence in aviation due to their compact size, low noise, and zero emissions compared to conventional gas turbines. This study presents an experimental test system for a 390 mm electric Ducted Propulsion Fan developed by the Aerospace Propulsion Systems group at Hanoi University of Science and Technology. The carbon fiber composite thruster, driven by a centrally located BLDC motor, was mounted on a test stand equipped with force and rotational speed (rpm) sensors. Power was supplied through two battery configurations, eight-pack and nine-pack, with voltage and current monitored and controlled via an ESC module. Experiments conducted from 2000 to 7000 rpm explored the relationship between electrical inputs and aero-propulsive outputs. The results revealed that input power, current, and sound pressure level (SPL) amplified meaningfully with rpm, while the voltage slightly declined. The maximum rpm reached 6500 rpm for the eight-pack and 7000 rpm for the nine-pack configurations. When greater than 6000 rpm, the SPL reaches close to 120 dB. The eight-pack configuration provided higher thrust per volt, whereas the nine-pack offered better thrust per ampere and improved starting power. Although dimensionless indices, including power coefficient (CP), thrust coefficient (CT), and figure of merit (FM), reduced with rpm, the FM remained between 0.7 and 0.75 at medium speeds, demonstrating effective energy conversion. Full article

This study employs Monte Carlo (MC) models and thermal-statistical analysis to investigate the production mechanisms of strange ($K_S^0$, $\mathrm{\Lambda }$) and multi-strange ($\mathrm{\Xi }$, $\mathrm{\Omega }$) hadrons in high-multiplicity proton–proton collisions. Through systematic comparisons with experimental data, we evaluate the predictive power of EPOS, PYTHIA8, QGSJETII04, and Sibyll2.3d. EPOS, with its hydrodynamic evolution, successfully reproduces low-$p_T$$K_S^0$ and $\mathrm{\Lambda }$ yields in high-multiplicity classes (MC1–MC3), mirroring quark-gluon plasma (QGP) thermalization effects. PYTHIA8’s rope hadronization partially mitigates mid-$p_T$ multi-strange baryon suppression but underestimates $\mathrm{\Xi }$ and $\mathrm{\Omega }$ yields due to the absence of explicit medium dynamics. QGSJETII04, tailored for cosmic-ray showers, overpredicts soft $K_S^0$ yields from excessive soft Pomeron contributions and lacks multi-strange hadron predictions due to enforced decays. Sibyll2.3d’s forward-phase bias limits its accuracy at midrapidity. No model fully captures $\mathrm{\Xi }$ and $\mathrm{\Omega }$ production, though EPOS remains the closest. Complementary Tsallis distribution analysis reveals a distinct mass-dependent hierarchy in the extracted effective temperature ($T_{\mathrm{eff}}$) and non-extensivity parameter (q). As multiplicity decreases, $T_{\mathrm{eff}}$ rises while q declines—a trend amplified for heavier particles. This suggests faster equilibration of heavier particles compared to lighter species. The interplay of these findings underscores the necessity of incorporating QGP-like medium effects and refined strangeness enhancement mechanisms in MC models to describe small-system collectivity. Full article

Direct laser acceleration with radially polarized lasers is an intriguing variant of laser-based particle acceleration that has the potential of offering GeV/cm-level energy while avoiding the instabilities and complex beam dynamics associated with plasma wakefield accelerators. A major limiting factor is the difficulty of generating high-power radially polarized beams. In this paper, we propose the use of CO₂-based long-wave infrared (LWIR) lasers as a driver for direct laser acceleration, as the polarization insensitivity of the gain medium allows a radially polarized beam to be amplified. Additionally, the larger waist sizes, Rayleigh lengths, and pulse lengths associated with the long wavelength could improve the injection efficiency of the electron beam. By comparing acceleration simulations using a near-infrared laser and an LWIR laser, we show that the injection efficiency is indeed improved by up to an order of magnitude with the longer wavelength. Furthermore, we show that even sub-TW peak powers with an LWIR laser can provide MeV-level energy gains. Thus, radially polarized LWIR lasers show significant promise as a driver of a direct laser-driven demonstration accelerator. Full article

Ytterbium laser sources are state-of-the-art systems that are increasingly replacing Ti:Sapphire lasers in most applications requiring high repetition rate pulse trains. However, extending these laser sources to THz Time-Domain Spectroscopy (THz-TDS) poses several challenges not encountered in conventional, lower-power systems. These challenges include pump rejection, thermal lensing in nonlinear media, and pulse durations exceeding 100 fs, which consequently limit the detection bandwidth in TDS applications. In this article, we describe our design of a THz-TDS beamline that seeks to address these issues. We report on the effectiveness of temperature controlling the Gallium Phosphide (GaP) used to generate the THz radiation and its impact on increasing the generation efficiency and aiding pump rejection while avoiding thermal distortions of the residual pump laser beam. We detail our approach to pump rejection, which can be implemented with off-the-shelf products and minimal customization. Finally, we describe our solution based on a commercial optical parametric amplifier to obtain a temporally compressed probe pulse of 55 fs duration. Our study will prove useful to the increasing number of laboratories seeking to move from the high-energy, low-power THz time-domain spectroscopy systems based on Ti:Sapphire lasers, to medium-energy, high-power systems driven by Yb-doped lasers. Full article

The vibration parameters during drilling play a critical role in enhancing drilling speed and ensuring safety. However, traditional downhole vibration sensors face limitations in their power supply methods, hindering widespread adoption. To address this challenge, our research introduces a novel solution: a hybrid downhole vibration sensor (HDV-TENG) utilizing triboelectric nanogenerators. This sensor not only enables the measurement of low- to medium–high-frequency vibrations using self-power but also serves to energize other downhole devices. We utilized a self-constructed vibration simulator to replicate downhole drilling tool vibrations and conducted a comprehensive series of sensor tests. The test results indicate that the frequency measurement bandwidth of the HDV-TENG spans from 0 to 200 kHz. Especially, the measurement errors for vibrations within the low-frequency range of 0 to 10 Hz and the high-frequency range of 10 to 200 k Hz are less than 5% and 8%, respectively. Additionally, the experimental findings regarding load matching demonstrate that the HDV-TENG achieves an output power level in the milliwatt range, representing a significant improvement over the output power of traditional triboelectric nanogenerators. Unlike traditional downhole vibration measurement sensors, HDV-TENG operates without requiring any external power supply, thereby conserving downhole space and significantly enhancing drilling efficiency. Furthermore, HDV-TENG not only offers a broad measurement range but also amplifies output power through the synergy of a triboelectric nanogenerator (TENG), piezoelectric nanogenerator (PENG), and electromagnetic power generator (EMG). This capability enables its utilization as an emergency power source for other micropower equipment downhole. The introduction of HDV-TENG also holds considerable implications for the development of self-powered underground sensors with high-frequency measurement capabilities. Full article

This paper presents recent results on CMOS integrated circuits for automotive radar sensor applications in the 77 GHz frequency band. It is well demonstrated that nano-scale CMOS technologies are the best solution for the implementation of low-cost and high-performance mm-wave radar sensors since they provide high integration level besides supporting high-speed digital processing. The present work is mainly focused on the RF front-end and summarizes the most stringent requirements of both short/medium- and long-range radar applications. After a brief introduction of the adopted technology, the paper addresses the critical building blocks of the receiver and transmitter chain while discussing crucial design aspects to meet the final performance. Specifically, effective circuit topologies are presented, which concern mixer, variable-gain amplifier, and filter for the receiver, as well as frequency doubler and power amplifier for the transmitter. Moreover, a voltage-controlled oscillator for a PLL efficiently covering the two radar bands is described. Finally, the circuit description is accompanied by experimental results of an integrated implementation in a 28 nm fully depleted silicon-on-insulator CMOS technology. Full article

Hollow-core photonic crystal fibers (HC-PCFs) provide an ideal transmission medium and experimental platform for laser–matter interaction. Here, we report a cascaded all-fiber gas Raman laser based on deuterium (D₂)-filled HC-PCFs. D₂ is sealed into a gas cavity formed by a 49 m-long HC-PCF and solid-core fibers, and two homemade fiber Bragg gratings (FBGs) with the Raman and pump wavelength, respectively, are further introduced. When pumped by a pulsed fiber amplifier at 1540 nm, the pure rotational stimulated Raman scattering of D₂ occurs inside the cavity. The first-order Raman laser at 1645 nm can be obtained, realizing a maximum power of ~0.8 W. An all-fiber cascaded gas Raman laser oscillator is achieved by adding another 1645 nm high-reflectivity FBG at the output end of the cavity, reducing the peak power of the cascaded Raman threshold by 11.4%. The maximum cascaded Raman power of ~0.5 W is obtained when the pump source is at its maximum, and the corresponding conversion efficiency inside the cavity is 21.4%, which is 1.8 times that of the previous configuration. Moreover, the characteristics of the second-order Raman lasers at 1695 nm and 1730 nm are also studied thoroughly. This work provides a significant method for realizing all-fiber cascaded gas Raman lasers, which is beneficial for expanding the output wavelength of fiber gas lasers with a good stability and compactivity. Full article

On the basis of density functional theory (DFT) at the B3LYP/cc-pVQZ level with the C-PCM solvation model, a comparative analysis of the reactivity of the garlic metabolites 2-propenesulfenic acid (PSA) and allyl mercaptan (AM, 2-propene-1-thiol) was performed. In particular, the thermodynamic descriptors (BDE, PA, ETE, AIP, PDE, and G_acidity) and global descriptors of chemical activity (ionization potential (IP), electron affinity (EA), chemical potential (μ), absolute electronegativity (χ), molecular hardness (η) and softness (S), electrophilicity index (ω), electro-donating (ω⁻) and electro-accepting (ω⁺) powers, and Ra and Rd indexes) were determined. The calculations revealed that PSA is more reactive than AM, but the latter may play a crucial role in the deactivation of free radicals due to its greater chemical stability and longer lifetime. The presence of a double bond in AM enables its polymerization, preserving the antiradical activity of the S-H group. This activity can be amplified by aryl-substituent-containing hydroxyl groups. The results of the calculations for the simplest phenol–AM derivative indicate that both the O-H and S-H moieties show greater antiradical activity in a vacuum and aqueous medium than the parent molecules. The results obtained prove that AM and its derivatives can be used not only as flavoring food additives but also as potent radical scavengers, protecting food, supplements, cosmetics, and drug ingredients from physicochemical decomposition caused by exogenous radicals. Full article

This paper investigates the narratives involved in the becoming public of an ecological, relational, and culinary culture through artistic mediums. Specifically, the question posed is this: how do food and cooking feature in some selected design and architecture exhibitions? The argument is developed through a series of thematic case studies that aim to affirm the presence in contemporary design, architecture, and exhibition-making of an ecological paradigm. The examples blur the lines of food and art by being proposed as processes of collective authorship happening in atmospheres of conviviality and hospitality. I bring forth the argument that developing exhibitions through the lines of hospitality can improve the quality of public engagement, and amplify a relational model which calls for the collective and entangled nature of all things. Alongside the potential of the arts of sparking a cognitive restructuring and shift in perspective, some risks associated with the mainstream model of society are considered. The final aim is to affirm the importance of relationships to oppose the neoliberal geopolitics of power which foster object-oriented perspectives. Full article

The multi-hop amplify-and-forward free-space optical communication (FSOC) system is studied in random fog using the I-function, considering Gamma-Gamma atmospheric turbulence and Beckmann pointing error. Outage probability, average bit error rate and average ergodic channel capacity are obtained. Channel-state-information assisted relay performs better than fixed-gain relay under high transmitted power. Increasing the hop number significantly improves the performance. More hops are needed in medium fog than in light fog to achieve the same performance. In addition, on a single-hop link, the influence of fog channel on system performance is dominant, while atmospheric turbulence intensity, normalized jitter standard deviation and normalized boresight error have little effect on the system performance. However, on a multi-hop link, atmospheric turbulence intensity, normalized jitter standard deviation and normalized boresight error have serious effects on system performance. Compared with correcting the normalized boresight error, compensating the normalized jitter standard deviation greatly improves the multi-hop FSOC system performance. Furthermore, optimizing beam width can further improves the performance. To ensure good communication, the system should select a low-order modulation scheme. Full article

Given their considerable specific surface area and amorphous characteristics, nanoparticles exhibit excellent pozzolanic activity, and when undergoing a reaction with calcium hydroxide, this leads to the generation of a denser matrix by promoting the formation of a greater amount of C-S-H gel, thereby enhancing the strength and durability of the concrete and fortifying the overall structure. Indeed, the present study investigates a comparative study of the buckling and free vibration analyses of concrete beams reinforced with various types of nanoparticles. For its simplicity and accuracy, a higher-order shear deformation theory will be used to analytically model the reinforced concrete beam. Furthermore, the powerful Eshelby’s model is used to derive the equivalent nanocomposite properties. The soil medium is simulated with Pasternak elastic foundation, including a shear layer, and Winkler’s spring, interlinked with a Kerr foundation. The motion equations are derived using Hamilton’s principle. Moreover, based on Navier’s analytical methods, the closed-form solutions of simply supported beams have been obtained. Different parameters, such as type and volume percent of nanoparticles, geometrical parameters, choice of theory and soil medium, on the buckling and dynamic behavior of the beam, are exercised and shown. The major findings of this work indicate that the use of nanoparticles in concretes increases better mechanical resistance and amplifies the natural frequencies. In addition, the elastic foundation has a significant impact on the buckling and vibration performances of concrete beams. Full article

This article describes a master oscillator and power amplifier (MOPA) system with a single longitudinal mode (SLM) and high-repetition-frequency Pr³⁺:YLF active medium that was end-pumped by two 444 nm laser diodes. The Pr³⁺:YLF MOPA laser system produced a maximum pulse energy of 13.5 μJ with a pulse width of 130.2 ns at a pulse repetition frequency of 20 kHz, translating to a peak power of around 103.7 W. The Pr³⁺:YLF MOPA laser system’s output wavelength was 639.7 nm, and the line-width of its laser spectra was roughly 168 MHz. Additionally, at the highest output level, the laser beam quality did not decrease much due to amplification. Full article

The in vitro cultures of Rindera graeca, a rare endemic plant, were developed as a sustainable source of phenolic acids. Various shoot and root cultures were established and scaled up in a sprinkle bioreactor. A multiplication rate of 7.2 shoots per explant was achieved. HPLC–PDA–ESI–HRMS analysis revealed the presence of rosmarinic acid (RA) and lithospermic acid B (LAB) as the main secondary metabolites in both the shoot and root cultures. The maximum RA (30.0 ± 3.2 mg/g DW) and LAB (49.3 ± 15.5 mg/g DW) yields were determined in root-regenerated shoots. The strongest free radical scavenging activity (87.4 ± 1.1%), according to 2,2-diphenyl-1-picrylhydrazyl-hydrate assay, was noted for roots cultivated in a DCR medium. The highest reducing power (2.3 µM ± 0.4 TE/g DW), determined by the ferric-reducing antioxidant power assay, was noted for shoots cultivated on an SH medium containing 0.5 mg/L 6-benzylaminopurine. A genetic analysis performed using random amplified polymorphic DNA and start codon targeted markers revealed genetic variation of 62.8% to 96.5% among the investigated shoots and roots. This variability reflects the capacity of cultivated shoots and roots to produce phenolic compounds. Full article

This paper presents a real-time remote water level monitoring system based on dense wavelength division multiplexing (DWDM)-passive optical fiber sensor (OFS) network for the application of the Internet of Things (IoT). This network employs a broadband light source based on amplified spontaneous emission (ASE) as a seed light. This ASE light is spectrum-sliced by an athermal type arrayed waveguide grating (200 GHz × 16 channel), then distributed towards multiple sensing units (SU). Here, 16 SUs are installed vertically at the specified height in the water pool according to the design specification (i.e., spatial resolution). Then, each SU reflects an optical spectrum having a different reflection coefficient depending on the surrounding medium (e.g., air or water). By measuring these reflected optical spectra with an optical spectrum analyzer, the water level can be easily recognized in real time. However, as the sensing distance increases, system performance is severely degraded due to the Rayleigh Back-Scattering of the ASE light. As a result, the remote sensing capability is limited at a short distance (i.e., <10 km). To overcome this limitation, we propose a simple signal processing technique based on feature extraction of received optical spectra, which includes embedding a peak detection algorithm with a signal validation check. For the specific, the proposed signal processing performs the peak power detection, signal quality monitoring, and determination/display of the actual water level through three function modules, i.e., data save/load module, signal processing module, and Human–Machine Interface display module. In particular, the signal quality of the remote sensing network can be easily monitored through several factors, such as the number of spectral peaks, the wavelength spacing between neighboring peaks and the pattern of detected peak power. Moreover, by using this validation check algorithm, it is also possible to diagnose various error types (such as peak detection error, loss of data and so on) according to the pattern of measured optical spectra. As a result, the IoT sensor network can recognize 17 different level statuses for the water level measurement from a distance of about 25 km away without active devices such as optical amplifiers (i.e., passive remote sensing). Full article