Optical Testing Research Articles

Maritime free space optical communications field test and link budget statistics

During sub-optimal weather, a free-space optical (FSO) link range degrades depending on attenuation (atmospheric extinction) and turbulence effects. The ability to predict the system level performance can be exceedingly challenging as the atmospheric variability in a maritime link can be large and difficult to model. Link budget estimation for FSO systems often takes a nominal view of atmospheric conditions; here, we use statistical atmospheric predictions specific to a geographic area of interest to enable performance trades to be evaluated through link budget analysis. We compare these models to field-collected data to show the utility of the statistical atmospheric analysis in predicting FSO link performance for specific parts of the world. We have performed shore-to-ship FSO communications field tests at 10 Gb/s with links reaching out to a horizon limit over 40 km away in times of moderate extinction to clear weather. We provide further analysis by describing the expected performance of the link using statistical probabilities via cumulative distribution functions of both extinction and turbulence. The atmospheric variability can be determined for nearly any region of interest through the implementation of numerical weather prediction data to calculate the atmospheric performance drivers. These conditions are specifically evaluated for the 2017 Trident Warrior field test off the coast of San Diego, California, USA.

Synthesis and characterization of Ni@UiO-66 Metal-Organic Framework for fluorescence detection of heavy metal ions in the aqueous phase

The toxicity of clean fresh water has become a major concern in the 21st century. The pollution of fresh and marine water bodies via anthropogenic activities introduces fatal chemicals like heavy metal ions into the environment causing disastrous impacts on human life as well as floral-faunal biota. Hence, it is crucial to develop a nanomaterial that can probe on these lethal heavy metal ions feasibly as well as with low detection limits. Metal-Organic Frameworks are frequently employed in optics as fluorescence sensors for detecting heavy metal ions. Therefore, in this study, Ni(II) was doped into the UiO-66 network, and the fluorescent characteristics of the obtained MOF structure were observed. The morphological characterizations were conducted via PXRD and SEM while the optical tests based on fluorescent spectroscopy were given more attention. The as synthesized MOF i.e., Ni@UiO-66 gave excellent fluorescent detection exhibiting “Turn-Off” for Hg(II) and Fe(III), while “Turn On” for Cr(VI), and Al(III) analytes. In aqueous phase, the lowest detection limit values of 7.98 x 10−7 M for Hg(II) ions is observed. The former's sensing mechanism was attributed to the inner filter effect (IFE), while the latter's mechanism could potentially be linked to the chelation-enhanced fluorescent (CHEF) effect. These findings imply that the Ni@UiO-66 metal-organic framework has the potential to be used for the detection for minute quantities of Hg(II), Al(III), Cr(VI), and Fe(III) ions.

Impact of SWCNTs and CMCS on efficacy of anastomosis and optical properties in vivo during laser biological tissue soldering

In order to improve the mechanical properties of skin tissue incision, enhance laser absorption efficiency, further shorten healing time and reduce skin fibrosis tendency, this study investigated the effects of CMCS or SWCNT combined with 25 % BSA and 0.4 % ICG on laser tissue welding. Nd:YAG pulsed laser was used for wound closure test on live rats with an energy density of 67.3 J/cm2 and linear scanning of skin incisions. The effects of different types and concentrations of biological dressings on wound closure were tested at different sites. The results showed that biocompatible dressings containing CMCS and SWCNTs had a significant effect in promoting wound healing after laser welding. After laser welding, the tensile strength of the control group without CMCS or SWCNTs was only between 6.5 and 9.8 N/cm2, while that with CMCS reached as high as 26.5 N/cm2. Macroscopic morphology analysis showed that components such as CMCS and SWCNTs could significantly shorten healing time from 14 days to 9–10 days. Optical performance tests demonstrated that a combination of 5 %CMCS and 4 %SWCNTs can significantly increase skin's absorption coefficient for laser photons up to7-8 Lg-1cm−1 and reduce photon diffuse reflectance. HE and Masson staining revealed that when internalized by dressing containing 0.4 %SWCNTs, nanocarbon particles promoted collagen skeleton regeneration but increased fibrosis tendency after 14 days post-laser welding, resulting in unfavorable long-term healing outcomes. However, the combination of CMSC with SWCNTs can significantly improve incision mechanical properties, laser photon absorption rate, and shorten healing time while reducing scar proliferation tendencies.

High thermal stability effect of vanadium on the binary CuAl base alloy for a novel CuAlV high-temperature shape memory alloy

Abstract In this study, two high-temperature shape memory alloys (HTSMAs) of CuAlV with unprecedented chemical compositions were fabricated using the arc melting technique, followed by traditional ice-brine water quenching after the melting process. To characterize the shape memory properties and structure of the alloys, a series of tests including differential calorimetry (DSC and DTA), EDS, optical microscopy, and XRD were conducted. The DSC tests, performed at different heating and cooling rates, demonstrated highly stable reversible martensitic phase transformation peaks at high temperatures, which were also confirmed by the results of DTA tests. Microstructural XRD and optical microscopy tests were conducted at room temperature, revealing the martensitic structure of the alloys in both cases. Based on all the results, the effects of different minor amounts of vanadium additives directly on the CuAlV alloy were discussed.

MALDI-TOF MS combined with AUC method for tigecycline susceptibility testing in Escherichia coli.

The wide spread of tet(X4) gene orthologues in the environment, food, poultry and humans is causing serious tigecycline resistance. Consequently, developing a fast and universal method to detect tigecycline resistance has become increasingly important. During 2019-2022, 116 Escherichia coli isolates were obtained from nine provinces in China. All isolates were tested for their susceptibility to antimicrobial agents by the microdilution broth method and for the tet(X4) gene by PCR. Ten tet(X4)-positive E. coli isolates were used to confirm certain conditions, including the optimal incubation time, the optimal concentration of tigecycline, and the cut-off of the relative growth (RG) value. The optimal time and concentration of tigecycline for separation of susceptible and resistant isolates was 2 h and 4 mg/L, and the RG cut-off value was 0.4. We validated whether the experiment was feasible using 116 isolates of E. coli. The method yielded a susceptibility of 94.9% (95% CI: 81.4%-99.1%) and a specificity of 96.1% (95% CI: 88.3%-99.0%). This research has shown that this optical antimicrobial susceptibility testing method can rapidly differentiate between susceptible and resistant phenotypes in isolates of E. coli. In the same range as the current gold-standard methods, the clinical turnaround time is reduced from 48 h to 2.5 h. The above results suggest that the method has splendid specificity and operationality.

Experimental Study on the Characterization of Aging Resistance Properties of Optical Cables in the Hydrogen-Containing Downhole Environment.

The utilization of downhole optical cables has significantly enhanced the efficiency and reliability of oilfield production operations; however, the challenging high-temperature and high-pressure conditions prevalent in oil-gas fields markedly reduce the service lifespan of these optical cables. This limitation severely impedes their application and further development in subterranean environments. In this study, a qualitative analysis was conducted on the structural materials utilized in two types of optical cables to identify these materials and assess the high-temperature tolerance and aging resistance properties of the optical fibers incorporated within. It was discovered that hydrogen infiltration into the subterranean optical cables predominantly accounts for their operational failure. To address this issue, an optical loss testing platform was established, facilitating the execution of a high-temperature and high-pressure hydrogen permeation aging experiment on the optical fibers, allowing for the evaluation of the hydrogen resistance capabilities of the two types of optical fibers. The findings from this study provide a theoretical foundation and methodological guidance for the optimization of optical fibers, aiming to enhance their durability and functional performance in adverse environmental conditions encountered in oil-gas field applications.

Femtosecond mode-locked laser at 1.5 μm region using topological semimetals NbAs nanosheets

For the first time, NbAs nanosheets are used as a saturable absorber for fiber laser mode locking, achieving high efficiency saturation absorption. NbAs nanosheets are prepared through a liquid-phase exfoliation method, and the following nonlinear optical testing is performed with a self-built twin balanced detection device, with a modulation depth of 3.92 %. Additionally, NbAs nanosheets are embedded in erbium-doped fiber laser as saturable absorber to produce stable laser output with excellent performance. NbAs nanosheets based saturable absorber can achieve a pulse width of 640 fs. Compared with other topological materials, weyl semi-metal NbAs nanosheets based saturable absorber shows narrower pulses and broader linewidths. Those results hold significant importance for exploring the potential applications of NbAs in ultrafast fiber lasers.

Design of a new detachable pedicle screw based on medical optical imaging inspection to improve osteoporosis and enhance vertebral body revision effect

Osteoporosis is a common bone disease that often leads to difficulty in vertebrae revision. Traditional pedicle screws are often complicated to operate and have poor visibility during implantation. A new detachable pedicle screw is needed to improve the revision effect. The aim of this study was to design a new detachable pedicle screw based on medical optical imaging to improve the outcome of vertebral revision in osteoporosis, and to improve operational feasibility and visibility. In this study, the parameters related to the degree of osteoporosis were obtained by optical imaging detection of the osteoporotic vertebral body. Then a new detachable pedicle screw was designed according to the test results to improve the effect of vertebral body revision. By preparing and optimizing the material and structure of the screw, it is ensured that it has sufficient mechanical strength and stability. Finally, the visibility and operability of the improved screw during implantation were verified by medical optical imaging. Compared with traditional screws, the new detachable pedicle screw can improve the vertebral body revision in the case of osteoporosis. The optical imaging test results show that the new screw has good visibility and maneuverability, providing more accurate guidance and positioning for the vertebral body revision operation.

First‐Principles Calculations to Investigate the Ground State, Mechanical Stability, Electronic Structure, and Optical Properties of Tl2SnX3 (X = S, Se, Te)

AbstractIn this work, the Density Functional Theory (DFT) analysis of the Tl2SnX3 series (X = S, Se, Te) is performed, and the ground states are confirmed by the calculation of the elastic constant Cij. Based on the DFT calculation, the Tl2SnX3 structures are direct‐gap semiconductors with bandgaps of 1.434, 1.181, and 0.907 eV, respectively. Chalcogen substitution significantly impacts their electronic structures, notably increasing the Density of States (DOS) width in the valence band from sulfur to tellurium, and shifting the dielectric function's real part, ε1(ω), toward lower energies. This change means that the optical activity and response to electric fields are better, with Tl2SnTe3 showing the best polarization response and light‐matter interaction abilities. Optical tests show that Tl2SnTe3 has very high optical absorption, peaking at ≈17 × 104 cm−1 along [010], and reflectivity levels above 90%, marking its suitability for high‐reflectivity applications. Moreover, loss energy function analysis also shows that Tl2SnTe3 has a strong electron loss resonance at lower energies, which means it has strong interactions with electrons.

The Behavior of Ceramic Fiber Geopolymer Concrete under the Effect of High Temperature

Geopolymer concrete (GC), also known as green concrete, contains slag, silica fume, and fly ash as binders. The absence of cement in concrete is critical to protect the world from the environmental impacts of cement production. In addition, exposure to high temperatures is a critical parameter that causes loss of strength in concrete. In this study, Geopolymer concrete samples were prepared with 10 different samples containing different proportions of slag, silica fume, and porous ash and subjected to various physical, mechanical, and optical tests. The sample (GS90) with optimum workability and compressive strength, which also showed high performance in water absorption, freeze-thaw, and UPV tests, was used in high-temperature tests. Portland cement concrete (PCC) was used as a control sample. This study investigated the effect of high temperatures on the physical and mechanical properties of fiber-free GCs containing 2%, 5%, and 10% by volume of ceramic fibers. Therefore, fiber-reinforced, fiber-free, and PCC specimens were subjected to high-temperature tests at 100, 300, 600, and 900 °C. As a result of the observation of crack growth, color changes, and compressive strength parameters in the samples subjected to high-temperature tests, the thermal resistance of the 10% ceramic fiber geopolymer concrete sample was 2.5% higher than other samples. There is no study in the literature that examines the behavior of ceramic fiber-reinforced geopolymer concrete at high temperatures. This research revealed an important finding by proving that ceramic fiber reinforcement increases the compressive strength of geopolymer concretes at a remarkable rate after high-temperature impact.

Experiment of droplet contact angle hysteresis on PTFE fibrous membrane in pore-scale

The present paper aims to study the influence of pore-scale fiber structure on the Cassie-Baxter contact angle of droplets on PTFE fibrous hydrophobic membranes. The fiber structure is obtained by the Confocal Laser Scanning Microscope (CLSM), and an optical test bench is built to measure the Cassie-Baxter contact angles of a droplet on a PTFE membrane. The free energy of the solid-liquid interface is measured by the surface tension integral on the droplet profile. An iterative algorithm for liquid-vapor interface shrinking is brought forward to analyze the liquid-vapor interface area between the droplet and the membrane, and the interface parameters of the Cassie-Baxter model are recognized. The experiment shows that the Cassie-Baxter contact angles and the contact line radii along the droplet circumference are in a normal distribution due to random fiber structures, and the variance of the normal distribution increases with the membrane pore diameter. The normal distribution of Cassie-Baxter’s contact angle indicates the constraint of the solid-liquid interface to the liquid-vapor interface. On the same normal contact pressure condition, the liquid-vapor area ratio of the droplet and membrane interface changes little, and Cassie-Baxter’s contact angle increases with the solid-liquid interface area ratio.

Effect of acrylic acid on water‐whitening resistance of polyacrylate latex films and its mechanism

AbstractTwo groups of polyacrylate latexes with higher (21 ~ 35 °C) or lower (−33 ~ −43 °C) glass transition temperatures (Tg) were prepared by adjusting the monomer ratio of butyl acrylate (BA) and styrene (St), and the effect of acrylic acid (AA) on water‐whitening resistance of these latex films was investigated. It was found that the water‐whitening resistance of the two groups of latex films was different. With the increase of AA content, the water whitening resistance of the latex films with higher Tg continued to improve, while that of the latex films with lower Tg increased first and then decreased. A series of characterizations, such as light transmittance, water whitening, water absorption, static water contact angle, surface morphology, and optical microscope test of the latex film, and so forth, showed that the reason for this difference was that under higher AA content (≥5%), compared with the polyacrylate latex films with lower Tg, the latex films with higher Tg could reach the saturation state of water absorption quickly, and water in these latex films exhibited continuous and large area distribution, rather than formation of many so‐called micro‐ or nano‐scale water sacs that can scatter light as found in the latex films with lower Tg.

Use of simulation tools to enhance classroom instruction in aberrations, interferometry, and optical testing

Use of simulation tools to enhance classroom instruction in aberrations, interferometry, and optical testing

Non-destructive techniques for corrosion detection: A review

Corrosion detection (CD) has become a high priority in chemical industries, defense and transportation sectors to extend the life of existing or new systems while ensuring the safety of the existing components and reducing downtime to minimise economic losses. Here, this article is aimed to review and discuss non-destructive techniques used widely in the industry to detect, monitor and repair corrosion problems early on. The comprehensive review provides a detailed discussion, a functional mechanism, advantages and disadvantages of crucial non-destructive CD techniques widely used in the industry, helping the reader choose the type of corrosion monitoring methods effectively. An extensive literature review of visual and optical testing techniques, acoustic emissions, eddy current, guided wave and equipment, infrared thermography, radiographic, microwave and millimeter wave, and terahertz imaging is discussed. The underlying mechanism, its merits and limitations, along with the usage scenario, is explained that can be related across different areas making it interdisciplinary research for corrosion monitoring techniques.

Synchronous Imaging and Multimodal Fusion of Optical and Electromagnetic Measurements for Overlapping Defects Inspection

It is a challenging problem to accurately detect overlapping defects. This paper proposes a system that can obtain optical and electromagnetic signals synchronously. It contains an industrial camera, a chromatic confocal displacement sensor (CCDS) and an eddy current testing (ECT) probe with high-resolution array tunneling magnetoresistance (TMR) sensors. A multimodal fusion algorithm is proposed to combine the advantages of the optical testing and ECT. The fusion of the visual image and CCDS measurement results in morphology of the surface defects. To recognize the overlapping buried defect, a finite element method model is developed to estimate the surface defect signal using parameters from the optical measurements, and then the surface defect signal is subtracted from the experimental image, based on which the overlapping defects are precisely detected. This method can be widely used in industry to comprehensively assess the health and integrity of structures.

Experimental demonstration of quantum-inspired optical symmetric hypothesis testing.

We use a phase-sensitive measurement to perform a binary hypothesis testing, i.e., distinguish between one on-axis and two symmetrically displaced Gaussian point spread functions. In the sub-Rayleigh regime, we measure a total error rate lower than allowed by direct imaging. Our results experimentally demonstrate that linear-optical spatial mode transformations can provide useful advantages for object detection compared with conventional measurements, even in the presence of realistic experimental cross talk, paving the way for meaningful improvements in identifying, detecting, and monitoring real-world, diffraction-limited scenes.

Epigallocatechin-3-gallate combination on the growth of Enterococcus faecalis and cytotoxicity on fibroblast cells

Background: Calcium hydroxide is an ingredient that is often used in pulp capping procedures. Calcium hydroxide can cause chronic inflammation and has weak antibacterial properties against Enterococcus faecalis. Epigallocatechin-3-gallate (EGCG) has anti-inflammatory properties and antibacterial properties against Enterococcus faecalis bacteria. Materials applied to the oral cavity were non-cytotoxic, biocompatible and antibacterial. Purpose: To determine the inhibitory effect against Enterococcus faecalis bacterial growth and cytotoxic to fibroblast cells of calcium hydroxide and EGCG combination with various concentrations of EGCG solution 5 µg/mL, 10 µg/mL, 20 µg/mL. Method: Calcium hydroxide mixed with EGCG with EGCG concentration in distilled water, at 5 µg/mL, 10 µg/mL, 20 µg/mL concentrations. The inhibitory test was tested using Petri dishes with Mueller-Hinton agar, using a dilution method. Observation of the inhibition zone at Petri dishes was carried out by measuring the diameter around the well using calipers. The cytotoxicity test was tested on BHK-21 fibroblast cells using the MTT assay test. The Formazan optical density test indicated the number of live cells. Result: The result of the inhibitory test showed a significant difference between the calcium hydroxide-EGCG group. The cytotoxicity test showed that there was no significant difference in the percentage of living fibroblasts, after administration of the calcium hydroxide-EGCG combination.

Experimental and Theoretical Study on Forming Film Properties of Hollow Cylindrical Rollers

Bending deformation of a hollow cylindrical roller (HCR) was calculated by curve bending theory and slice technology. Furthermore, an elastohydrodynamic lubrication (EHL) model involving hollow rollers was established by coupling the finite line EHL model and bending deformation. Measurements of film thickness for hollow rollers were carried out by using a line-contact optical EHL test rig, and the experimental data and theoretical results agreed well with each other. For a roller with a straight-line profile, the hollow structure could reduce pressure peak at the roller ends, but the edge effect was still present. The film thickness at the ends unfortunately could not be improved by such hollow structures, unless a profile modification for the operating surface is designed.

Ink Analysis for Forensic Investigations: An Integrated Approach Incorporating Physico-chemical Techniques and Image Processing

Background: Criminal actions using falsified papers are on the rise. Any changes to the document's content are usually made with ballpoint and gel pens. All changes made to a document using a pen necessitate ink analysis. Thus, a quick and accurate ink analysis process must be created to cope with the challenges associated with counterfeiting. Aim: This study aims to analyze several brands of ballpoint and gel pen inks using physicochemical and computational techniques and provide a database of the results. Methods: A total of 24 pen samples from various brands were colour-tested first, followed by an optical test using ImageJ software. The composition of each ink sample was distinguished using the non-destructive method ATR-FTIR, followed by a destructive technique TLC. Lastly, a computational technique algorithm was applied for rapid and desirable results. Results: The results distinguished each brand based on RGB measures and mean values. The differentiation of each sample using ATR-FTIR spectroscopy was challenging due to similar structural characteristics. However, TLC (destructive) was used with several solvent systems. Ballpoint pen inks separated well in all solvent systems, with the greatest results achieved in solvent systems 2 and solvent system 4. The TLC spots were identical, but when evaluated digitally using MATLAB, substantial changes were visible, which were utilized to differentiate similar colour inks from various brands. Conclusion: The chemical approaches, in conjunction with the computational techniques, offered a rapid and sophisticated method that allowed for better distinction of the inks and provided more accuracy in substantially less time than typical methods employed in forensic laboratories.

Experimental study of lube oil pre-ignition in an optical gas engine test rig

Lean-premixed gas combustion is an attractive option for meeting future emission standards toward considerably lower particulate matter and emissions while obtaining an efficiency comparable to diesel combustion. However, ignition processes still pose considerable challenges, with pre-ignition being a major issue. The pre-ignition phenomenon might result from the self-ignition of lube oil in hot zones, making it challenging to observe in real engines. To study single or sparsely separated lube oil droplets under engine-like conditions, the “Flex-OeCoS” experimental test facility was used. To be able to induce such pre-ignitions artificially a novel piezo droplet injector was developed and manufactured, which enabled the metering of minor amounts of lubricating oil or even the injection of single droplets. High-speed cameras and specially developed and partially automatable and adaptive evaluation algorithms were used to record and track the behavior of the injected droplet using overlaid schlieren and OH* chemiluminescence. During the measurement campaigns, relevant operating parameters were varied, and optical investigations were carried out with an ignitable mixture on the Flex-OeCoS test facility under engine-relevant operating conditions. Spontaneous ignition of the vaporized lubricating oil was observed, which subsequently led to ignition of the whole air-fuel mixture in the optical combustion chamber. This was especially evident for lean methane-air mixtures up to an air-fuel ratio of 2.0. With this approach, information could be gathered about the necessary internal engine conditions that lead to pre-ignition in lean mixtures and where their limits lie.