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The effective large signal longitudinal piezoelectric coefficient (d 33 , f ∗) of piezoelectric thin films on rigid substrates has been widely investigated. Unclamped piezoelectric thin films are predicted to have a higher d 33 , f ∗ coefficient due to reduced constraints on piezoelectric strain, domain reorientation, and domain wall motion, but quantitative measurements of this coefficient have been limited. This study uses microfabrication techniques along with double-beam laser interferometry (DBLI) to accurately determine the longitudinal piezoelectric coefficient of Pb(Zr,Ti)O3 thin films in partially released piezomicroelectromechanical structures. A two-step backside release process was used: first, deep reactive ion etching to create backside vias and second, wet etching of the ZnO sacrificial layer to release the area beneath the Pb(Zr,Ti)O3 thin films. Post wet etching, optical profilometry showed concavely deformed diaphragms resulting from asymmetrical stress profiles through the diaphragm thickness. DBLI was then used to examine diaphragm deflection under an applied unipolar voltage ranging from 0 to 10 V. Devices with 50% and 75% of the area beneath the top electrode released exhibited large signal d 33 , f ∗ values of 410 ± 6 and 420 ± 8 pm/V, respectively, more than three times higher than the d 33 , f ∗ value of the clamped samples: 126 ± 13 pm/V. The reasons contributing to the large d 33 , f ∗ include (i) the change in stress levels due to the release process, (ii) the elimination of mechanical constraints from substrate clamping, and (iii) enhanced domain reorientation. These findings confirm that substrate declamping significantly boosts the piezoelectric coefficient, bringing d 33 , f ∗ closer to the bulk longitudinal piezoelectric coefficient (d33). [ABSTRACT FROM AUTHOR]

We measured the austenitic FeCr18Ni12.5 stainless steel Hugoniot as a function of crystallographic direction to approximately 60 GPa. We shock-compressed FeCr18Ni12.5 samples oriented along ⟨ 100 ⟩ , ⟨ 110 ⟩ , and ⟨ 111 ⟩ to mean stresses ranging 30.5–58.1 GPa via Ta plate impact in a large-bore powder gun and measured the free-surface velocities with laser interferometry. We unambiguously observed the largest post-shock free-surface velocity along ⟨ 100 ⟩ in each experiment, which consequently produced the lowest shock velocity along that orientation. However, the propagation of experimental uncertainties through the impedance matching scheme used to compute the shock velocity produced sufficient uncertainty overlap to preclude definitive conclusion of Hugoniot anisotropy. [ABSTRACT FROM AUTHOR]

Detailed investigation of pathogen transmission by respiratory droplets requires extensive experimental datasets with high spatial–temporal resolution in a wide range of ambient conditions. Respiratory simulators are attractive tools for those measurements, because they improve repeatability, endurance, and control of experimental conditions with respect to studies on human subjects. They also enable the use of powerful experimental techniques, which may raise health concerns if employed on humans. In this paper, we design and present a respiratory simulator, which is capable of accurately reproducing physiological flow rate profiles and allows the investigation of the spatial and temporal features of the exhaust flow by background‐oriented schlieren (BOS) and particle image velocimetry (PIV). We use laser interferometry and high‐magnification shadowgraphy to verify the size distributions of the emitted droplets, and we quantify the evolution of the droplet concentration during cough events by Mie scattering analysis. The experiments demonstrate the ability of the respiratory simulator to generate highly reproducible cough events with precise and controllable droplet size distributions over a wide range of flow rates. [ABSTRACT FROM AUTHOR]

The accurate measurement of inter-satellite distances is fundamental to the successful operation of distributed spacecraft missions, facilitating diverse applications ranging from scientific exploration to navigation and communication. This study comprehensively overviews applications requiring inter-satellite tracking by analyzing 44 multi-spacecraft missions. These missions are divided into seven categories based on their use of inter-satellite distance measurements. Each category necessitates varying levels of accuracy, prompting the utilization of distinct tracking methods. The analysis reveals that missions near Earth typically rely on Global Navigation Satellite Systems measurements, achieving millimeter-level accuracy, while lunar missions opt for radio ranging for centimeter-level accuracy. Inter-satellite Laser Ranging Interferometry emerges as the preferred method for missions demanding exceptionally high accuracy (nanometer to picometer range), such as those dedicated to gravitational wave detection and gravimetry. Notably, the analysis identifies a burgeoning trend towards the adoption of Inter-satellite Laser Transponder Ranging, capable of achieving sub-millimeter accuracy. Furthermore, this work proposes a novel concept: integrating inter-satellite ranging with Laser Communication Terminal (LCTs), either to substitute for existing tracking methods or to enhance measurement accuracy within established frameworks. However, its full potential rests upon the successful adaptation of existing LCTs for ranging functionality without compromising data rates. Future research will play a critical role in quantifying achievable ranging performance by characterizing systematic errors within LCTs. [ABSTRACT FROM AUTHOR]

The addition of an oxidizer to aluminized explosives can promote the reaction of the aluminum particles to release more energy, significantly increasing the energy of the explosion. In this study, metal plate acceleration tests of CL-20-based explosives under strong constraints were performed, and the metal plate velocity was measured by laser interferometry, then the metal plate acceleration processes were simulated. By combining experiment and numerical simulation, the metal acceleration characteristics of the initial detonation stage were obtained, and the energy release and aluminum reaction law of oxidizer-containing cast cured aluminized explosives were investigated. The results showed that, in the initial stage of the detonation product expansion, the energy released from the aluminum reaction in the explosives with an oxidizer was slower than that in the explosives without an oxidizer. As the oxidizer content increased, the acceleration ability decreased, and the energy utilization rate of the explosive decreased. This may be because of the relatively low CL-20 content and high oxidizer content, where the oxidizer does not participate in the initial reaction and absorbs a large amount of the heat released by the CL-20 reaction, resulting in weak acceleration ability in the initial detonation stage of aluminized explosives. [ABSTRACT FROM AUTHOR]

This paper describes the design and principle of operation of a 20 m laser strainmeter of unequal-arm type created on the basis of a Michelson interferometer and frequency-stabilized helium–neon laser. The interferometry methods used allow the measurement of the displacement of an Earth's crust section on the base of the laser strainmeter with an accuracy of 30 pm in the frequency range from 0 (conventionally) to 1000 Hz. This laser strainmeter, when connected to an accurate time system providing an accuracy of 1 μs, should structurally become a part of the laser interferometric seismoacoustic observatory, consisting of spatially separated laser strainmeters installed in various regions of Russia. [ABSTRACT FROM AUTHOR]

Background: From new results presented in the literature we discuss the hypothesis, presented in an our previous work, that the ultrafast periodic spectral modulations at f S = 0.607 ± 0.08 THz found in the spectra of 236 stars of the Sloan Digital Sky Survey (SDSS) were due to oscillations induced by dark matter (DM) cores in their centers that behave as oscillating boson stars. Two other frequencies were found by Borra in the redshift-corrected SDSS galactic spectra, f 1 , G = 9.71 − 0.19 + 0.20 THz and f 2 , G = 9.17 − 0.16 + 0.18 THz; the latter was then shown by Hippke to be a spurious frequency introduced by the data analysis procedure. Results: Within the experimental errors, the frequency f 1 , G is the beating of the two frequencies, the spurious one, f 2 , G and f S that was also independently detected in a real solar spectrum, but not in the Kurucz's artificial solar spectrum by Hippke, suggesting that f S could actually be a real frequency. Independent SETI observations by Isaacson et al., taken at different epochs, of four of these 236 stars could not confirm with high confidence—without completely excluding—the presence of f S in their power spectra and with the same power initially observed. Instead, the radio SETI deep-learning analysis with artificial intelligence (AI) gave an indirect confirmation of the presence of f S through the detection of a narrowband Doppler drifting of the observed radio signals in two stars, over a sample of 7 with a high S/N. These two stars belong to the set of the 236 SDSS stars. Numerical simulations confirm that this drifting can be due to frequency and phase modulation in time of the observed frequencies (1.3–1.7 GHz) with f S . Conclusions: Assuming the DM hypothesis, the upper mass limit of the axion-like DM particle is m a ≃ 2.4 × 10 3 μ eV , in agreement with the results from the gamma ray burst GRB221009A, laser interferometry experiments, suggesting new physics with additional axion-like particle fields for the muon g-2 anomaly. [ABSTRACT FROM AUTHOR]

The study of high-pressure sound velocity is an important part of shock wave physics, and the study of ultra-high pressure sound velocity of iron is of great significance to many research fields such as geophysics, solid state physics, and crystallography. At present, the measurement of sound velocity is usually carried out by the catch-up sparse wave method and windowed VISAR technology, which is complex in structure and not highly adaptable. In particular, for the ultra-high pressure sonic velocity measurement of metals, it is limited by the loading platform and window materials and cannot realize the high temperature and high-pressure environment of the earth's inner core. In this paper, the sound velocity measurement of iron under high temperature and high-pressure environment (78 GPa) is realized based on the two-stage light gas cannon experimental platform. The side-side sparse wave method was used to establish a coupling model of high-spatially resolved optical group and fiber bundle. A multiplexed all-fiber laser interferometry velocity measurement system (DISAR) was built, and the spatial resolution was better than 20 μm. In this paper, we will provide a feasible route for a method for measuring the high spatiotemporal resolution velocity. [ABSTRACT FROM AUTHOR]

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Blood consists of many numerous cells and presence of protein makes it thicker than water. According to medical research, a normal person has in excess of a 5 l of blood. Protein is natural compound which is naturally found in the human body. In this study, the absorbance of human blood in the range of ultraviolet (UV) and visible (VIS), from 190 to 1100 nm was measured. In our experimental work the absorbance peaks and transmittance peaks have been observed to agree with reported literature values. We have also studied the behaviour of human blood in region of near infrared and calculated the contents of protein with the help of spectrophotometric method by measuring the absorbance value in the test serum with enzymatic reagents. The qualitative measurement of all the samples were measure using dark field microscope with a laser wavelength of 630 nm and bandwidth of 15 nm. In this work we have also established the relation between the concentrations of total protein level with the complete blood count. [ABSTRACT FROM AUTHOR]

In this study, we designed ranging parameters and refined a loop filtering algorithm to solve the problem of parameter compatibility with the phasemeter and low ranging accuracy under bidirectional communication conditions. This enables the ranging and communication system to be integrated directly into the phasemeter as an auxiliary module. Experimental results compare fiber measurement lengths under different clock sources, indicating that the system achieves an ranging accuracy of 82.1 cm with an rms error of 9.14 cm. Additionally, the data communication rate reaches 19.5 kbps with a bit error rate below 10−6, all while ensuring that the implementation of the laser ranging and data communication system utilizes only 1% of the optical power to avoid introducing excessive phase noise to the scientific interferometer.

A new technique is assessed in order to measure, at the wafer scale, direct bonding energies. It is derived from the standard Double Cantilever Beam (DCB) method and uses interferometry in confocal IR laser source microscopy to measure crack openings. Such a bonding energy measurement protocol has better accuracy compared to other techniques. This is due to a better confocal microscopy resolution and the high intensity of the laser source. The elastic energy stored in bent wafers is obtained by measuring the beam curvature. DCB deformation models are discussed from the short-range crack opening theory to long distance beam-bending theories. Comparison is made between models, experimental results, and FEM simulations. Finally, the bonding energy error during standard measurements is estimated. [ABSTRACT FROM AUTHOR]

Laser-shock compression experiments at 3rd and 4th generation light sources generally employ phase plates, which are inserted into the beamline to achieve a repeatable intensity distribution at the focal plane. Here, the laser intensity profile is characterized by a high-contrast, high-frequency laser speckle. Without sufficient smoothing, these laser non-uniformities can translate to a significant pressure distribution within the sample layer and can affect data interpretation in x-ray diffraction experiments. Here, we use a combination of one- and two-dimensional velocity interferometry to directly measure the extent to which spatial frequencies within the laser focal spot intensity pattern are smoothed out during propagation within the laser plasma and a polyimide ablator. We find that the use of thicker polyimide layers results in spatially smoother shock fronts, with the greatest degree of smoothing associated with the highest spatial frequencies. Focal spots with the smallest initial speckle separation produce the most rapid smoothing. Laser systems that employ smoothing by spectral dispersion techniques to rapidly modulate the focal plane intensity distribution are shown to be the most effective ones in producing a spatially smooth shock front. We show that a simple transport model combined with the known polyimide Hugoniot adequately describes the extent of shock smoothness as a function of polyimide thickness. Our results provide a description of spatial structure smoothing across a shock front, which can be used to design targets on x-ray free electron laser facilities. [ABSTRACT FROM AUTHOR]

To robustly and adaptively reconstruct displacement, we propose the amplitude modulation integral reconstruction method (AM-IRM) for displacement sensing in a self-mixing interferometry (SMI) system. By algebraically multiplying the SMI signal with a high-frequency sinusoidal carrier, the frequency spectrum of the signal is shifted to that of the carrier. This operation overcomes the issue of frequency blurring in low-frequency signals associated with continuous wavelet transform (CWT), enabling the precise extraction of the Doppler frequency of the SMI signal. Furthermore, the synchrosqueezing wavelet transform (SSWT) is utilized to enhance the frequency resolution of the Doppler signal. Our experimental results demonstrate that the proposed method achieves a displacement reconstruction accuracy of 21.1 nm (0.89%). Additionally, our simulations demonstrated that this method can accurately reconstruct target displacement under the conditions of time-varying optical feedback intensity or a signal-to-noise ratio (SNR) of 0 dB, with a maximum root mean square (RMS) error of 22.2 nm. These results highlight its applicability in real-world environments. This method eliminates the need to manually determine the window length for time–frequency conversion, calculate the parameters of the SMI system, or add additional optical devices, making it easy to implement. [ABSTRACT FROM AUTHOR]

This work presents issues related to selected errors accompanying spatial measurements of surface roughness using contact profilometry. The influence of internal heat sources, such as engines or control electronics, on the thermal expansion of the drive responsible for the measurement probe's movement in the X-axis direction was investigated. In terms of starting measurements on a thermally unstable device, the synchronization error of individual profile paths was 16.1 µm. Based on thermographic studies, the time required for full thermal stabilization of this drive was determined to be 6–12 h from when the device was turned on. It was demonstrated that thermal stabilization of the profilometer significantly reduced positioning errors of the measurement probe on the X-axis. Thermal stabilization time should be determined individually for a specific device variant. This research also determined how changes in the center of gravity caused by the measurement probe's movement affected the overall rigidity of the profilometer structure and the leveling of the tested surface. Laser interferometry was used for this purpose. The determined vulnerability of the profilometer structure was 0.8 µm for a measurement section of 25 mm. Understanding the described relationships will reduce errors associated with conducting measurements and preparing equipment for tests. Additionally, it will enable the correct evaluation of surface geometry. [ABSTRACT FROM AUTHOR]

The novel laser ranging interferometer (LRI) on GRACE Follow-On (GRACE-FO) provides range and range rate measurements for more than 4 years now. Since the launch of the GRACE-FO mission there were few investigations about this measurement system on the level of gravity field recovery and analysis of post-fit residuals. We applied techniques such as along-orbit-analysis or time-argument of latitude diagrams (TAL) to analyse the post-fit range rate residuals as well as the post-fit range acceleration residuals to identify unknown characteristics and systematic effects. The effects are the range rate effect, the panel effect, the Carrier-To-Noise Ratio (CNR) effect and the polar effect. The range rate effect occurs, when the range rate observation ρ ̇ of the LRI is around 0 m/s. In the TAL diagram the effect appears as a mesh pattern. The panel effect shows patterns of increased residuals when a specific satellite panel starts or stops being illuminated by the Sun. Increased residuals appear when the laser beam is aligned with the Sun. A CNR drop as well as a fluctuation of the yaw and pitch pointing angles obtained from the LRI steering mirrors is observable. Additionally, when the satellites flying into or out of the Earth shadow this effect coincides with the shadow transition effect. Another effect is the CNR effect which appears as an elliptic shape in the TAL diagram. This pattern occurs when the CNR values drop below the LRI requirements of 70 dB-Hz. All these effects have not been detected in the residuals of the GRACE-FO K-band ranging system (KBR) and therefore further investigation and studies will improve the understanding and applications of LRI technology. [ABSTRACT FROM AUTHOR]

The three spacecraft of the space gravitational wave antenna employ heterodyne interferometry to mitigate the effects of Doppler shift. Constrained by laser relative intensity noise (RIN) and the sampling frequency constraints of phase readout circuits, the widespread adoption of fixed offset frequencies effectively regulates the frequency of heterodyne interferometric beat notes within a reasonable frequency domain of [5 MHz, 25 MHz]. In this work, a high-precision fitness genetic algorithm for heterodyne interferometry is utilized to generate the initial offset frequency distribution scheme. To address issues with unreasonable switching times and offset frequency settings in the initial scheme for partial frequency domains, optimization strategies are proposed from three aspects: frequency domain selection extension, switch times control, and numerical low frequency. Results demonstrate that the optimization of frequency domain selection extension narrows the reasonable frequency domain to [5 MHz, 15 MHz] and [7 MHz, 17 MHz]. Optimization of switch times control ensures that switching times of offset frequency distribution scheme generated under the settings of [6 MHz, 17 MHz] and wider frequency domains can be controlled within a reasonable range of 6 to 13 times. Fixed offset frequency settings are generally reduced by 24.3% after low-frequency optimization. This methodology and result can provide a reliable reference for Program Taiji and even related space gravitational wave antenna projects. [ABSTRACT FROM AUTHOR]

On the basis of diffraction transformations of wave fields, a mathematical model of a speckle interferometer of transverse displacements of a scattering object has been developed and numerical modeling of speckle-modulated interference patterns and signals at the output of the interferometer has been performed. Numerical calculations of the spatial distribution of complex amplitudes of wave fields in an interferometer were used for modeling when the displaced scattering surface was illuminated by two obliquely incident laser Gaussian beams. A statistical numerical experiment was performed to determine the measurement error of the scattering surface displacement caused by the change of realizations of interfering speckle fields. The simulation results are in good agreement with the results of experimental studies of transverse displacements in the range up to 600 micrometers. [ABSTRACT FROM AUTHOR]

Biological neurons are electro-mechanical systems, where the generation and propagation of an action potential are coupled to the generation and transmission of an acoustic wave. Neuristors, such as VO2, characterized by insulator-metal transition (IMT) and negative differential resistance, can be engineered as self-oscillators, which are good approximations of biological neurons in the domain of electrical signals. In this study, we show that these self-oscillators are coupled electro-opto-mechanical systems, with better energy conversion coefficients than the conventional electro-mechanical or electro-optical materials. This is due to the significant contrast in the material's resistance, optical refractive index, and density across the induced temperature range in a Joule heating driven IMT. We carried out laser interferometry to measure the opto-mechanical response while simultaneously driving the devices electrically into self-oscillations of different kinds. We analyzed films of various thicknesses, engineered device geometry, and performed analytical modeling to decouple the effects of refractive index change vis-à-vis mechanical strain in the interferometry signal. We show that the effective piezoelectric coefficient (d13*) for our neuristor devices is 660 ± 20 pm/V, with a 31% internal energy conversion efficiency, making them viable alternatives to Pb-based piezoelectrics for MEMS applications. Furthermore, we show that the effective electro-optic coefficient (r13*) is ∼22 nm/V, which is much larger than that in thin-film and bulk Pockels materials. [ABSTRACT FROM AUTHOR]

Vibration measurement is crucial in fields like aviation, aerospace, and automotive engineering, which are trending towards larger, lighter, and more complex structures with increasingly complicated dynamics. Consequently, measuring a structure's dynamic characteristics has gained heightened importance. Among non-contact approaches, those based on high-speed cameras combined with laser interferometry or computational imaging have gained widespread attention. These techniques yield sequences of images that form a three-dimensional space-time data set. Effectively processing these data is a prerequisite for accurately extracting dynamic deformation information. This paper presents two examples to illustrate the significant advantages of signal processing along the time axis in dynamic interferometric and digital speckle-image-based dynamic measurements. The results show that the temporal process effectively minimizes speckle and electronic noise in the spatial domain and dramatically increases measurement resolutions. [ABSTRACT FROM AUTHOR]

Dimensional measurements are fundamental in microfluidic device manufacturing and performance. The main focus of this study is the measurement of the connection port sizes in microfluidic devices and components and, accordingly, the possible existence of fluid leaks determined using the flow rate error. The sizes associated with three different microfluidic systems were determined using laser interferometry and through an optical measuring instrument, with metrological traceability to national length standards. It was possible to infer the method with the greatest accuracy and lowest measurement uncertainty for characterizing this kind of system. In conclusion, the results of this work directly address the current lack of dimensions measuring methods of microfluidic components by providing a comprehensive comparison of different protocols, ultimately suggesting a preferred option for immediate application within the microfluidic industry. [ABSTRACT FROM AUTHOR]

The laser interferometer space antenna (LISA) uses laser interferometry to measure gravitational wave-induced distance changes between freely falling test masses on separate spacecraft. In practice, the space-borne gravitational wave detector operates in a plasma medium, and subsequently, the variations in electron density affect the refractive index and add displacement noise to measurements. Geometric time-delay interferometry (TDI) is the TDI combinations searched by geometric method, which is employed to mitigate overwhelming laser phase noise. This study explores all forty-five second-generation geometric TDI combinations up to sixteen links, analyzing plasma noise effects via power spectral density and cross-spectral density calculations for different optical links. Our findings reveal that plasma noise can exceed the noise floor, which comprises optical metrology system and test mass acceleration noise, in certain low-frequency regions due to different noise transfer behaviors. Further, we establish electron density requirements for various TDI combinations, showing that densities below 100 cm − 3 / Hz @ 10 mHz satisfy LISA's criteria across all forty-five combinations. This allows for optimized TDI selection based on specific plasma densities. [ABSTRACT FROM AUTHOR]

A method is proposed for measuring absolute distances from the low-frequency spectrum of the interference signal of a frequency-modulated laser diode. The method of modulation of the self-mixing laser signal according to the harmonic law is used, in the spectrum of which a wide range of frequency components is observed. The connection between the maximum frequency of change of the interference signal and the absolute distance to the reflector is shown. A linear dependence of the frequency corresponding to the inflection region of the decay envelope of the interference signal spectrum on the distance is shown, which can be used to implement a non-contact distance measurement method with harmonic modulation of the self-mixing laser supply current. [ABSTRACT FROM AUTHOR]

Spectrally resolved interferometry utilizing a femtosecond laser is widely employed for absolute distance measurement. However, deviations in the output time pulse of the conventional algorithm through inverse Fourier transform are inevitable. Herein, an improved data processing algorithm employing a time-shifting parameter is proposed to improve the accuracy of spectrally resolved interferometry. The principle of the proposed time-shifting algorithm is analyzed theoretically after clarifying the deviation source of the conventional algorithm. Simulation and experimental work were conducted to indicate the improvement in the accuracy of the output absolute distance. The results demonstrated that the proposed algorithm could reduce the deviation of output distances towards the reference values, reaching 0.58 μm by half compared to the conventional algorithm. Furthermore, the measurement uncertainty was evaluated using the Guide to the Expression of Uncertainty in Measurement (GUM), resulting in an expanded uncertainty of 0.71 μm with a 95% confidence. [ABSTRACT FROM AUTHOR]

A 3D nano-displacement measurement method, where the difference in phase between the beams in a four-beam laser interference is changed, is proposed. Simulation results demonstrate that the variation of phase difference causes the deviation of the interference pattern in the laser interference system. Based on this theory, we design and build a four-beam laser interference system. The corner cube prism in the optical path is shifted, and the phase of the beam is changed by applying different voltages to a piezoelectric stage. The phase difference is obtained by analyzing the lattice pattern with subpixel precision, and then the displacement is determined by correlation operation. The experimental measurement results are consistent with the theoretical analysis, thereby verifying the feasibility of this measurement method. Highlights: The four-beam laser interference lattice pattern can achieve higher precision displacement measurement. The 3D displacement measurement system of the four-beam laser interference can realize single-dimensional or multi-dimensional displacement measurement. At the same time, it provides a basis for micro-displacement measurement in various applications. The specific pixels of the interference pattern are accurately located using the correlation operation to achieve precise measurement results and minimize errors. [ABSTRACT FROM AUTHOR]

A conceptual design for diagnosing erosion of the first wall and divertor plates of a tokamak with reactor technologies TRT is proposed. The principles of constructing a diagnostic complex based on the following systems are developed: laser radar, dual-wavelength digital holographic interferometry and active laser IR thermography. An optical scheme is developed for combining the optical paths to input laser radiation and collect scattered light from diagnostic systems. To view the maximum area of the first wall, a scheme for optical scanning of the surface of the first wall and divertor is proposed. Based on optical simulation, the spatial distribution of the power density and phase of interferometry laser radiation in the illuminated region of the first wall is constructed, and the dimensions of the light fields and power density for IR thermography and laser radar diagnostics are determined. An image formation scheme is proposed and the spatial resolution is determined for interferometry and IR thermography methods. The light scattering function on models of the ITER divertor cladding is studied experimentally. The energy of the collected signal is calculated on the basis on the experimental data for all three diagnostic methods and the requirements for the diagnostic equipment are formulated. [ABSTRACT FROM AUTHOR]

The analysis of Z-pinch implosion dynamics plays one of the most important roles in the study of pulsed power discharges. At the same time, it is difficult to determine the density distribution together with the current density (current coupling to the imploding layer) to provide more detailed information about the dynamics. Numerical simulations can now provide high-resolution results that are almost unattainable in experiments. The challenge, however, is to obtain reliable results that are close enough to the experimental data to describe individual physical phenomena. In this paper, we show that it is possible to use a combination of experimental data and magnetohydrodynamic (MHD) simulations to verify and identify the physical processes during the stagnation of a Z-pinch. We focus on the analysis of the density profile from experimental data of the mega-ampere plasma focus PF-1000 and its reconstruction using an extended MHD code. Thanks to multi-frame interferometry, we recorded a total of 29 interferometric images of two shots, each in a 200 ns time window around the pinch phase. We were then able to obtain density profiles and observe the reflection of the shock wave from the axis. By the appropriate choice of initial conditions and boundary values in the simulation, we were able to obtain reasonable agreement with the experimental values. We also evaluated the possible shortcomings of the 1D simulation, such as mass loss and current flow at the periphery. [ABSTRACT FROM AUTHOR]

The shock compression of porous nickel from nanosized particles nNi was studied at a pressure range of 4–61 GPa. The average size of the nNi particles was 50 nm, and the porosity of the samples was 50%. Plane shock waves in the samples were generated by the impact of aluminum plates accelerated to velocities ranging from 0.8 to 5 km/s. Laser interferometry was used to monitor particle velocity histories at the interface between the samples and water or LiF windows. The data obtained at pressures below 8 GPa showed a complex shock wave profile with the formation of an elastic precursor wave. The shock Hugoniot and data on the expansion isentropes were obtained. The Hugoniot of nanosized nNi coincided within the experimental errors with the Hugoniot of micron-sized nickel. The Hugoniot calculated on the basis of the equation of state for porous nickel was in good agreement with that of experimental data. It has been established that in the middle pressure range (20–35 GPa), the expansion isentropes in the "pressure–particle velocity" coordinates become noticeably flatter with a significant increase in the particle velocity. The reason for this phenomenon is still unclear. An assumption was made about the onset of particle melting upon reaching pressures above 15 GPa. [ABSTRACT FROM AUTHOR]

Boundary-layer disturbances are analysed on a 5° half-angle blunted cone in Mach 5, high-enthalpy flow (h0 =9 MJ kg-1) with a low wall-to-edge temperature ratio, Tw/Te = 0.18. Schlieren and focused laser differential interferometry (FLDI) are utilized to assess the structures and frequency content associated with disturbances. Wave packets are identified from bursts of modal content on time-resolved spectrograms. Bandpass filtering, proper orthogonal decomposition (POD) and space-time POD are then applied to the schlieren data. Bandpass filtering suggests the presence of wave packet dispersion and elongation indicative of slow-acoustic-wave synchronization. Modal reconstruction techniques indicate the radiation of content outside the boundary layer and distinct orientation changes within disturbances, potentially the first experimental evidence of the supersonic-mode instability in such a flow field. Cross-bicoherence computations are carried out for discrete time segments of data from both schlieren and FLDI data. They demonstrate that the most dominant nonlinear interactions are the fundamental-first-harmonic and the fundamental-low-frequency interactions. [ABSTRACT FROM AUTHOR]

Twenty years of gravity observations from various satellite missions have provided unique data about mass redistribution processes in the Earth system, such as melting of Greenland's ice shields, sea level changes, ground and underground water depletion, droughts, floods, etc. The ongoing climate change underlines the urgent need to continue this kind of observations with future gravimetry missions using enhanced concepts and sensors. This paper studies the benefit of enhanced electrostatic and novel optical accelerometers and gradiometers for future gravimetry missions. One of the limiting factors in the current space gravimetry missions is the drift of the Electrostatic Accelerometers (EA) which dominates the error contribution at low frequencies (<1mHz). This study focuses on the modeling of enhanced EAs with laser-interferometric readout, so-called optical accelerometers, and on evaluating their performance for gravity field recovery in future satellite missions. In this paper, we simulate gravimetry missions in multiple scopes, applying various software modules for satellite dynamics integration, accelerometer (ACC) and gradiometer simulation and gravity field recovery. The total noise budgets of the modeled enhanced electrostatic and optical ACCs show a similar sensitivity as the ACC concepts from other research groups. Parametrization w.r.t. the weight of the test mass (TM) of ACCs and the gap between the TM and the surrounding electrode housing confirmed the fact known from previous results that an ACC with a heavier TM and a larger gap will perform better. Our results suggest that the anticipated gain of novel ACCs might at some point be potentially limited by noise from the inter-satellite laser ranging interferometry. In order to present the advantage of the novel sensors, time-variable background models and associated aliasing errors were not considered in our simulations. The utilization of enhanced EAs and optical ACCs shows a significant improvement of accuracy compared to the currently used GRACE-like EA. In addition, their benefit in double satellite pairs in a so-called Bender constellation as well as in the combination of low-low satellite-to-satellite tracking with cross-track gradiometry has been investigated. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the association of body stature with ocular biometrics and refraction in preschool children. Methods: A cross-sectional, school-based study was conducted in Shenzhen, China. Preschool children aged 3 to 6 from 10 randomly-selected kindergartens were recruited. Ocular biometric parameters, including axial length (AL), anterior chamber depth (ACD), vitreous chamber depth (VCD), corneal radius curvature (CR), axial length to corneal radius ratio (AL-to-CR ratio) and lens thickness (LT) were measured using non-contact partial-coherence laser interferometry. Cycloplegic refractions were obtained by a desktop autorefractor. Body height and weight were measured using standard procedures. The association between body stature and ocular biometrics were analyzed with univariable and multivariable regression model. Results: A total of 373 preschoolers were included. AL, ACD, VCD, CR, and AL-to-CR ratio, were positively associated with height and weight (p < 0.05), whereas LT was negatively associated with height and weight (p < 0.01). No association was observed between stature and central cornea thickness and refraction. After adjusted for age and gender in a multivariable regression model, AL had positive associations with height (p < 0.01) and weight (p < 0.01). However, refraction had no significant association with stature parameters. Conclusion: Taller and heavier preschoolers had eyes with longer AL, deeper vitreous chamber, and flatter cornea. The significant associations between body stature and ocular biometric parameters reveal the driving influence of body development on the growth of eyeballs in preschoolers. [ABSTRACT FROM AUTHOR]

Hypersonic boundary-layer transition onset is commonly characterized in wind tunnel experiments by measuring the surface heat transfer rise above the laminar level. Techniques such as infrared thermography and thin film gauges are routinely used in the field. However, when an interfering cooling effect is present due to foreign gas transpiration, these methods are known to be inadequate. This study uses a 7° half-angle cone at Mach 7 with helium or nitrogen injection through a porous segment within the model frustum. The injector spans 60° in azimuth and is located 300 mm from the sharp nose tip, close to the onset of natural boundary-layer transition. Nitrogen and helium injection reduce the surface heat flux below the laminar level for up to 50 mm downstream of the injector. Comparisons to schlieren images and pressure measurements indicate an advance of transition. Optical diagnostics reveal how instabilities are pushed away from the model surface by the injected gas. This is found through spectral analysis of schlieren images and focused laser differential interferometry signals, which revealed further information about how inaccuracies of detecting transition with surface gauges under the influence of transpiration cooling originate. [ABSTRACT FROM AUTHOR]

The Coriolis force is a significant source of systematic phase errors and dephasing in atom interferometry and is often compensated by counter-rotating the interferometry laser beam against Earth's rotation. We present a novel method for performing Coriolis force compensation for long-baseline atom interferometry, which mitigates atom-beam misalignment due to beam rotation, an effect which is magnified by the long lever arm of the baseline length. The method involves adjustment of the angle of the interferometer beam prior to a magnifying telescope, enabling the beam to pivot around a tunable position along the interferometer baseline. By tuning the initial atom kinematics and adjusting the angle with which the interferometer beam pivots about this point, we can ensure that the atoms align with the center of the beam during the atom optics laser pulses. This approach will be used in the MAGIS-100 atom interferometer and could also be applied to other long-baseline atom interferometers. An additional challenge associated with long baseline interferometry is that since long-baseline atom interferometers are often located outside of typical laboratory environments, facilities constraints may require lasers to be housed in a climate-controlled room a significant distance away from the main experiment. Nonlinear effects in optical fibers restrict the use of fiber-based transport of the high-power interferometry beam from the laser room to the experiment. We present the design of and prototype data from a laser transport system for MAGIS-100 that maintains robustness against alignment drifts despite the absence of a long fiber. [ABSTRACT FROM AUTHOR]

In this paper we report an improved method of coherent sensing through the use of a generalized phase-stepping algorithm to extract magnitude and phase information from interferometric fringes acquired by laser feedback interferometry (LFI). Our approach allows for significantly reduced optical sampling and acquisition times whilst also avoiding the need for fitting to complex models of lasers under optical feedback in post-processing. We investigate theoretically the applicability of this method under different levels of optical feedback, different laser parameters, and for different sampling conditions. We furthermore validate its use experimentally for LFI-based sensing using a terahertz (THz)-frequency laser in both far-field and near-field sensing configurations. Finally we demonstrate our approach for two-dimensional nanoscale imaging of the out-of-plane field supported by individual micro-resonators at THz frequencies. Our results show that fully coherent sensing can be achieved reliably with as little as 4 sampling points per imaging pixel, opening up opportunities for fast coherent sensing not only at THz frequencies but across the visible and infra-red spectrum. [ABSTRACT FROM AUTHOR]

Laser interferometry is one of the most accurate measurement technologies whose displacement resolution can reach the femtometer (fm) level. With the development of Micro‐Electro‐Mechanical Systems(MEMS) technology, many excellent optical interferometric MEMS sensors have emerged, which play an essential role in intelligent manufacturing, aerospace, and many other fields. Among them, optical interferometric MEMS accelerometers develop rapidly due to their high sensitivity, low noise, and anti‐electromagnetic interference advantages. Lots of research in optical interferometric chip design, micro‐nano fabrication process, signal demodulation algorithm, and range extension technology are performed, and different types of MEMS accelerometers based on the optical interferometric principles are developed, which have been demonstrated and applied in the fields of disaster monitoring, equipment operation and maintenance, and resource exploration. This paper reviews the development status of optical interferometric MEMS accelerometers, mainly focusing on the critical problems and solutions that need to be solved in the development process of optical interferometric accelerometers, and finally introduces the typical application scenarios. [ABSTRACT FROM AUTHOR]

This paper proposes a solution to the need for appropriate methods to control the health of the final product which is among the challenges of applying three-dimensional (3D) printers in mass production. Sheared laser interferometry so-called shearography is considered a proper option for this aim. The main objective of this paper is to inspect defective 3D-printed polymer parts. In addition, this study explores the influence of the infill percentage of the samples on the defect detectability as well as the shearography setup parameters. To this aim, three samples of Polylactic-acid (PLA) with different infill percentages were printed by the fused deposition modeling (FDM) method. Burnt filament defects were deliberately created inside the samples during printing. Shearography tests were carried out applying thermal excitation. Based on the results, the infill percentage directly affects the defect detectability as well as the shearography parameters. Accordingly, an increase in infill percentage enhanced the quality of shearography resultant fringe patterns. Additionally, it significantly leads to an increase in the detectable range of loading size and shear distance. Therefore, shearography was regarded as appropriate for detecting burnt filament defects, especially in high infill percentages. [ABSTRACT FROM AUTHOR]

Dispersive interferometry based on a femtosecond laser is extensively utilized for achieving absolute distance measurements with high accuracy. However, this method cannot measure arbitrary distances without encountering a dead zone, and deviations in its output results are inevitable due to inherent theory limitations. Therefore, two enhanced data-processing algorithms are proposed to improve the accuracy and reduce the dead zone of dispersive interferometry. The principles of the two proposed algorithms, namely the truncated-spectrum algorithm and the high-order-angle algorithm, are proposed after explaining the limitations of conventional methods. A series of simulations were conducted on these algorithms to show the improved accuracy of measurement results and the elimination of the dead zone. Furthermore, an experimental setup based on a dispersive interferometer was established for the application of these proposed algorithms to the experimental interference spectral signals. The results demonstrated that compared with the conventional algorithm, the proposed truncated-spectrum algorithm could reduce the output distance deviations derived from direct inverse Fourier transforming by eight times to reach as low as 1.3 μm. Moreover, the unmeasurable dead zone close to the zero position of the conventional algorithm, i.e., the minimum working distance of a dispersive interferometer, could be shortened to 22 μm with the implementation of the proposed high-order-angle algorithm. [ABSTRACT FROM AUTHOR]

The shock wave response of [100] lithium fluoride (LiF) single crystals at high stresses is of long-standing interest due to their extensive use as optical windows in dynamic compression experiments. The report of melting in shock-compressed LiF single crystals between 134 and 152 GPa—based on a single sound speed datum [Liu et al., J. Appl. Phys. 117, 045901 (2015)]—was surprising because good optical transmission was previously demonstrated in LiF shock compressed to ∼200 GPa [Rigg et al., J. Appl. Phys. 116, 033515 (2014)]. To address these apparent differences, we report on plate impact experiments on [100] LiF single crystals shock compressed to 168 GPa. Wave profiles were measured using laser interferometry to determine Hugoniot states and longitudinal sound speeds in shock-compressed LiF. The measured Hugoniot states are in good agreement with those measured in previous studies. However, the measured sound speeds presented here show no evidence of melting up to 168 GPa. In particular, the abrupt drop reported previously in sound speed at 152 GPa was not observed in the present work. Our results establish a lower bound of 168 GPa for the onset of melting in shock-compressed LiF single crystals. [ABSTRACT FROM AUTHOR]

Future GRACE-like geodesy missions could benefit from adopting accelerometer technology akin to that of the LISA Pathfinder, which employed laser interferometric readout at the sub-picometer level in addition to the conventional capacitive sensing, which is at best at the level of 100 pm. Improving accelerometer performance holds great potential to enhance the scientific output of forthcoming missions, carrying invaluable implications for research in climate, water resource management, and disaster risk reduction. To reach sub-picometer displacement sensing precision in the millihertz range, laser interferometers rely on suppression of laser-frequency noise by several orders of magnitude. Many optical frequency stabilization methods are available with varying levels of complexity, size, and performance. In this paper, we describe the performance of a Mach–Zehnder interferometer based on a compact monolithic optic. The setup consists of a commercial fiber injector, a custom-designed pentaprism used to split and recombine the laser beam, and two photoreceivers placed at the complementary output ports of the interferometer. The structural stability of the prism is transferred to the laser frequency via amplification, integration, and feedback of the balanced-detection signal, achieving a fractional frequency instability better than 6 parts in 10 13 , corresponding to an interferometer pathlength stability better than 1 pm / Hz . The prism was designed to host a second interferometer to interrogate the position of a test mass. This optical scheme has been dubbed "single-element dual-interferometer" or SEDI. [ABSTRACT FROM AUTHOR]

We propose that during the evaporation of sessile droplets, the evaporative flux profile is primarily influenced by droplet geometry and composition under diffusion-limited conditions. Most studies have focused solely on the evaporation feature from the liquid to the gas phase, neglecting the extent to which the evaporated vapors affect the evaporation process. We hypothesize that if the molecular weight of the evaporated vapors is significantly high or low compared to the ambient gas, it could alter the evaporative flux. We employed a direct optical measurement technique, specifically Mach-Zehnder interferometry. This demonstrated that the distribution of evaporated vapor molecules can substantially modify the evaporative flux profile. Our study discovered that substantial density gradients between vapor and air could either suppress or enhance the evaporative flux, depending on the droplet's orientation. This research offers fresh insights into evaporative fluxes by taking into account the relative vapor concentration and gravitational effects. • Laser interferometry was employed to accurately gauge the evaporative flux of a sessile droplet both on and underneath a plate. • Accuracy of the interferometric results was validated by comparison with side-view shadowgraphy results. • Both the molecular weight of evaporated vapor and the droplet orientation significantly impact the vapor distribution. • Vapor distribution surrounding droplets can significantly influence the evaporative flux. [ABSTRACT FROM AUTHOR]

Spatially inhomogeneous structures (SIS) are important to realize the integrated optical devices transmitting and processing light signals. Nowadays, there are several methods used to create such structures with different characteristics and topologies. However, research on the methods of forming and modifying the characteristics of these structures continues to this day. In this work, we create and study SIS in a lithium niobate crystal surface-doped with copper ions. The results prove that SIS can be created by the point-by-point method using a continuous-wave frequency-doubled YAG:Nd3+ laser. The realized structures were formed as diffraсtion and waveguide optical elements with different characteristics and topologies. It is demonstrated that we can change the refractive index up to 10–3 by the point-by-point illumination of an X‑cut lithium niobate crystal during the structure formation. The properties of the fabricated structures were investigated by diffraction analysis, laser interferometry, and the optical probing method using He–Ne laser radiation. On the formed diffraction structures (DSs), the far-field diffraction patterns (DPs) show that the light power transfers from the incident radiation to first-order maxima. The first-order maxima intensity can exceed the intensity of the zero-order maximum up to several times. The near-field study after the excitation of waveguide structures (WSs) shows that they exhibit the properties of mode filters. The point-by-point method of forming SIS may be useful for creating integrated optical circuits and modifying the characteristics of optoelectronic and photonic devices. [ABSTRACT FROM AUTHOR]

For space-based gravitational wave detection, a laser interferometric measurement system composed of a three-spacecraft formation offers the most rewarding bandwidth of astrophysical sources. There are no oscillators available that are stable enough so that each spacecraft could use its own reference frequency. The conversion between reference frequencies and their distribution between all spacecrafts for the synchronization of the different metrology systems is the job of the inter-spacecraft frequency setting strategy, which is important for continuously acquiring scientific data and suppressing measurement noise. We propose a hierarchical optimization algorithm to solve the frequency setting strategy. The optimization objectives are minimum total readout displacement noise and maximum beat-note frequency feasible range. Multiple feasible parameter combinations were obtained for the Taiji program. These optimized parameters include lower and upper bounds of the beat note, sampling frequency, pilot tone signal frequency, ultrastable clock frequencies, and modulation depth. Among the 20 Pareto optimal solutions, the minimum total readout displacement noise was 4.12 pm / Hz , and the maximum feasible beat-note frequency range was 23 MHz. By adjusting the upper bound of beat-note frequency and laser power transmitted by the telescope, we explored the effects of these parameters on the minimum total readout displacement noise and optimal local laser power in greater depth. Our results may serve as a reference for the optimal design of laser interferometry system instrument parameters and may ultimately improve the detection performance and continuous detection time of the Taiji program. [ABSTRACT FROM AUTHOR]

A new era of lunar exploration has begun bringing immense opportunities for science as well. It has been proposed to deploy a new generation of observatories on the lunar surface for deep studies of our Universe. This includes radio antennas, which would be protected on the far side of the Moon from terrestrial radio interference, and gravitational-wave (GW) detectors, which would profit from the extremely low level of seismic disturbances on the Moon. In recent years, novel concepts have been proposed for lunar GW detectors based on long-baseline laser interferometry or on compact sensors measuring the lunar surface vibrations caused by GWs. In this article, we review the concepts and science opportunities for such instruments on the Moon. In addition to promising breakthrough discoveries in astrophysics and cosmology, lunar GW detectors would also be formidable probes of the lunar internal structure and improve our understanding of the lunar geophysical environment. [ABSTRACT FROM AUTHOR]

Nanoparticles of CuO have been synthesized by the sol-gel technique and their structural, optical and chemical properties were studied to assess their antibacterial properties. These nanoparticles were found to be excellent antibiotic against E.coli and cocci gram-positive. Graphene oxide (GO) nanoparticles were also synthesized by hummers modified method and their optical, chemical and structural properties were confirmed. A composite of CuO and GO has also been prepared by sonication method. Using laser interferometry its ultraviolet (UV)-visible (VIS) spectrum has been observed to be consistent with its reference UV-VIS spectrum, which verified the formation of nanocomposite. The composites were prepared in suspension form, and were used for antibacterial activity, appeared to be a great antibacterial substance against two different types (E.coli and pseudo) of gram-positive bacteria. [ABSTRACT FROM AUTHOR]

As a high-end medical technology, high-intensity focused ultrasound (HIFU) is widely used in cancer treatment and ultrasonic lithotripsy technology. The acoustic output level and safety of ultrasound treatments are closely related to the accuracy of sound pressure measurements. Heterodyne laser interferometry is applied to the measurement of ultrasonic pressure owing to its characteristics of non-contact, high precision, and traceability. However, the upper limit of sound pressure measurement is limited by the bandwidth of the interferometer. In this paper, a high-bandwidth heterodyne laser interferometer for the measurement of high-intensity focused ultrasound pressure is developed and tested. The optical carrier with a frequency shift of 358 MHz is realized by means of an acousto-optic modulator. The selected electrical devices ensure that the electrical bandwidth can reach 1.5 GHz. The laser source adopts an iodine frequency-stabilized semiconductor laser with high-frequency spectral purity, which can reduce the influence of spectral purity on the bandwidth to a negligible level. The interference light path is integrated and encapsulated to improve the stability in use. An HIFU sound pressure measurement experiment is carried out, and the upper limit of the sound pressure measurement is obviously improved. [ABSTRACT FROM AUTHOR]

Measurements of surface heat flux via IR thermography and boundary layer density fluctuations using a variation of focused laser differential interferometry (FLDI) were performed concurrently on two models in a Mach 6 flow with freestream Reynolds number sweeps. For a flared cone geometry, the local surface heating and mean amplitude of turbulent wave packets are shown to increase in tandem. Furthermore, the combined data show that a significant increase in surface heat transfer coincides with the appearance of nonlinear interactions associated with the second-mode instability. For a tangent ogive model with roughness-dominated transition, a similar correlation between FLDI data and surface heat flux is observed. In both cases, the correlation is observed when using band-passed content near the characteristic frequency of the boundary layer, which suggests structures on the order of the boundary layer in scale dominate the surface heating process. In total, the present work suggests that analysis of wave packet amplitudes in FLDI can be directly tied to information about surface heating and identifying the eventual transition to fully turbulent flow. [ABSTRACT FROM AUTHOR]

In contribution 2, a precision 3D measurement instrument integrating multiple laser range sensors was designed, which fuses the information of multiple redundant laser range sensors to obtain the coordinates of a 3D position. Laser-based measurement and sensing technology has been paid more and more attention by academia and industry because of its incomparable advantages, such as high sensitivity, fast response, and no contact. In contribution 8, an evaluation method based on fitting planes was proposed to evaluate laser plane attitude and determine the degree of laser coplanarity effectively. Using the method in this study, the laser plane attitude can be quantified and accurately assessed on both sides, effectively resolving the problem with traditional methods that can only assess the laser plane attitude qualitatively and roughly, thereby providing a solid foundation for calibration and error correction of the measurement system. [Extracted from the article]

We propose an analysis of the recovery strategies for the science mode of the Laser Interfer-ometer Space Antenna (LISA) mission after a meteoroid impacts the spacecraft. The mission consists of a three-spacecraft constellation traveling in a heliocentric orbit, detecting gravitational waves through laser interferometry. To this end, each spacecraft must travel in a free-fall condition in order to reject any possible disturbance and noise affecting the control loop. Nevertheless, if one of the three satellites crosses a meteoroids stream, the collisions can produce attitude perturbations that must be compensated by the control loop. Indeed, in this latter case, the interferometer laser links can be lost. Unfortunately, the link recovery is accomplished through a quite time-consuming re-acquisition maneuver, implying a significant reduction of the science mode time. For this reason, we propose different strategies for a fast recovery of the nominal attitude. The strategies are supported and traded-off by means of extensive simulations, including a Monte Carlo campaign and a worst-case analysis. • Different GNC recovery strategies for LISA mission are identified and compared. • An attitude guidance and control system is designed for handling the attitude perturbation due to micrometeoroid impacts. • Different navigation filters, based on sensors measurements, are designed and compared. • Monte Carlo and worst-case simulations are presented to verify the effectiveness of the proposed GNC strategies. [ABSTRACT FROM AUTHOR]

Palm or coconut oil is capable of dissolving in a mixture of bisphenol A-based epoxy resin and a high-temperature hardener (4,4′-diaminodiphenyl sulfone) when heated and then forms a dispersed phase as a result of cross-linking and molecular weight growth of the epoxy medium. Achieving the temporary miscibility between the curing epoxy matrix and the vegetable oil allows a uniform distribution of vegetable oil droplets in the epoxy medium. This novel approach to creating a dispersed phase-change material made a cured epoxy polymer containing up to 20% oil. The miscibility of epoxy resin and oil was studied by laser interferometry, and phase state diagrams of binary mixtures were calculated according to theory and experiments. A weak effect of oil on the viscosity and kinetics of the epoxy resin curing was demonstrated by rotational rheometry. According to differential scanning calorimetry and dynamic mechanical analysis, the oil plasticizes the epoxy matrix slightly, expanding its glass transition region towards low temperatures and reducing its elastic modulus. In the cured epoxy matrix, oil droplets have a diameter of 3–14 µm and are incapable of complete crystallization due to their multi-component chemical composition and non-disappeared limited miscibility. The obtained phase-change materials have relatively low specific energy capacity but can be used alternatively as self-lubricating low-noise materials due to dispersed oil, high stiffness, and reduced friction coefficient. Palm oil crystallizes more readily, better matching the creation of phase-change materials, whereas coconut oil crystallization is more suppressed, making it better for reducing the friction coefficient of the oil-containing material. [ABSTRACT FROM AUTHOR]

The FMCW (Frequency Modulated Continuous Wave) laser interferometer can achieve high-precision displacement measurement by calculating the phase of the interference signal. Due to the need for continuous superposition of signal phases, the optical path and power supply cannot be interrupted during the measurement process. To solve this problem, this article proposes a new absolute ranging method—the decimal comparison method. Two distributed feedback lasers with different central wavelengths are used to measure the same target. The digital signal processing technology is used to solve the sampled interference signals, and the initial phase value corresponding to the decimal of interference is taken. Combined with the central wavelength of the two laser sources, the length variation of the F–P cavity corresponding to the number of interference periods is calculated. Finally, the optical path difference of the target is calculated by the established mathematical model. The experimental results show that this method can realize the absolute measurement of laser interferometry and can expand the application range of FMCW interferometry. [ABSTRACT FROM AUTHOR]