Optical Measurement System Research Articles

Buckling Analysis of Thin-Walled Composite Structures with Rectangular Cross-Sections under Compressive Load.

The purpose of this research was the analysis of the stability of compressed thin-walled composite columns with closed rectangular cross-sections, subjected to axial load. The test specimens (made of carbon-epoxy composite) were characterized by different lay-ups of the composite material. Experimental tests were carried out using a universal testing machine and other interdisciplinary testing techniques, such as an optical strain measurement system. Simultaneously with the experimental studies, numerical simulations were carried out using the finite element method. In the case of FEA simulations, original numerical models were derived. In the case of both experimental research and FEM simulations, an in-depth investigation of buckling states was carried out. The measurable effect of the research was to determine both the influence of the cross-sectional shape and the lay-up of the composite layers on the stability of the structure. The novelty of the present paper is the use of interdisciplinary research techniques in order to determine the critical state of compressed thin-walled composite structures with closed sections. An additional novelty is the object of study itself-that is, thin-walled composite columns with closed sections.

Brain-implanted conductors amplify radiofrequency fields in rodents: Advantages and risks.

Over the past few decades, daily exposure to radiofrequency (RF) fields has been increasing due to the rapid development of wireless and medical imaging technologies. Under extreme circumstances, exposure to very strong RF energy can lead to heating of body tissue, even resulting in tissue injury. The presence of implanted devices, moreover, can amplify RF effects on surrounding tissue. Therefore, it is important to understand the interactions of RF fields with tissue in the presence of implants, in order to establish appropriate wireless safety protocols, and also to extend the benefits of medical imaging to increasing numbers of people with implanted medical devices. This study explored the neurological effects of RF exposure in rodents implanted with neuronal recording electrodes. We exposed freely moving and anesthetized rats and mice to 950 MHz RF energy while monitoring their brain activity, temperature, and behavior. We found that RF exposure could induce fast onset firing of single neurons without heat injury. In addition, brain implants enhanced the effect of RF stimulation resulting in reversible behavioral changes. Using an optical temperature measurement system, we found greater than tenfold increase in brain temperature in the vicinity of the implant. On the one hand, our results underline the importance of careful safety assessment for brain-implanted devices, but on the other hand, we also show that metal implants may be used for neurostimulation if brain temperature can be kept within safe limits.

Modeling and design of high-sensitivity dual optical feedback interferometry measurement system enhanced by period-one dynamics

Laser optical feedback interferometry (OFI) is a unique one-channel interferometric measurement technology with the advantages of compact structure, low implementation cost and easy alignment. However, it has a critical challenge that the visibility of interference fringe is often low and further induces low measurement sensitivity, especially in occasions when the optical feedback strength is feeble, e.g., biomedical and fluid detection. Recently, it has been demonstrated that period-one (P1) dynamics can enhance the measurement sensitivity by introducing extra optical feedback to form a dual optical feedback interferometry (DOFI) system. However, the details of the enhancement mechanism and how to design such a system are still required to unveil. In this paper, comprehensive discussions of designing a DOFI system with high measurement sensitivity enhanced by P1 dynamics are presented. First, based on the modified Lang-Kobayashi equations, a mathematical sensing model of a DOFI system working in P1 state was established. Then, simulations were carried out to verify the validity of the proposed model. After that, factors that determine the sensitivity enhancement were analyzed, based on which, theoretical analysis of achieving optimal sensitivity enhancement was performed. Next, we discussed the operation region of a DOFI system in P1 state and investigated the influence of the system parameters on the operation region. At last, experiments were conducted to verify the theoretical analyses. The results of this work provide helpful guidance for the construction of high-sensitivity DOFI sensing and measurement systems.

Kinematic model calibration of a collaborative redundant robot using a closed kinematic chain

In this paper, we propose a novel approach for the kinematic calibration of collaborative redundat robots, focusing on improving their precision using a cost-effective and efficient method. We exploit the redundancy of the closed-loop kinematic chain by utilizing a spherical joint, enabling precise definition of the robot end-effector position while maintaining free joint motion in the null space. Leveraging the availability of joint torque sensors in most collaborative robots, we employ a kinesthetic approach to obtain constrained joint motion for calibration. An optimization approach is utilized to determine the optimal kinematic parameters based on measured joint positions and a constrained end-effector position defined by the spherical joint. The effectiveness of the proposed method is demonstrated and validated on the Franka Emika Panda robot, a 7-DoF robot. Results indicate a significant enhancement in absolute accuracy, with comparable performance to more expensive sensor systems such as optical measurement systems. Our approach offers a practical and cost-effective solution for improving the precision of collaborative robots.

Assessment of micromotion at the bone-bone interface after coracoid and scapular-spine bone-block augmentation for the reconstruction of critical anterior glenoid bone loss—a biomechanical cadaver study

BackgroundGlenoid bone loss is among the most important risk factors for recurrent anterior shoulder instability, and a bony reconstruction is recommended in cases of critical bone loss (> 15%). The commonly used surgical techniques, including coracoid transfer, are associated with considerable complications. The aim of this study was to assess the motion at the glenoid-bone-block interface after coracoid and spina-scapula bone-block reconstruction of the anterior glenoid.MethodsTwelve cadaveric shoulders were tested. A 20% bone defect of the anterior glenoid was created, and the specimens were randomly assigned for glenoid augmentation using a coracoid bone block (n = 6) or a scapular spine bone block (n = 6). The glenoid-bone interface was cyclically loaded for 5000 cycles with a force of 170 N. The micromotion was tracked using an optical measurement system (GOM ARMIS) and was evaluated with the GOM Correlate Pro software.ResultsThe most dominant motion component was medial irreversible displacement for the spina-scapula (1.87 mm; SD: 1.11 mm) and coracoid bone blocks (0.91 mm; SD: 0.29 mm) (n.s.). The most medial irreversible displacement took place during the first nine cycles. The inferior reversible displacement was significantly greater for spina-scapula bone blocks (0.28 mm, SD: 0.16 mm) compared to coracoid bone blocks (0.06 mm, SD: 0.10 mm) (p = 0.02).ConclusionsThe medial irreversible displacement is the dominant motion component in a bone-block reconstruction after a critical bone loss of the anterior glenoid. The spina-scapula and coracoid bone blocks are comparable in terms of primary stability and extent of motion. Thus, spina-scapula bone blocks may serve as alternatives in bony glenoid reconstruction from a biomechanical point of view.

Multi-camera optical tracking and fringe pattern analysis for eye surface profilometry in ocular proton therapy

Background and purposeAn optical tracking system for high-precision measurement of eye position and orientation during proton irradiation of intraocular tumors was designed. The system performed three-dimensional (3D) topography of the anterior eye segment using fringe pattern analysis based on Fourier Transform Method (FTM). Materials and methodsThe system consisted of four optical cameras and two projectors. The design and modifications to the FTM pipeline were optimized for the realization of a reliable measurement system. Of note, phase-to-physical coordinate mapping was achieved through the combination of stereo triangulation and fringe pattern analysis. A comprehensive pre-clinical validation was carried out. Then, the system was set to acquire the eye surface of patients undergoing proton therapy. Topographies of the eye were compared to manual contouring on MRI. ResultsPre-clinical results demonstrated that 3D topography could achieve sub-millimetric accuracy (median:0.58 mm) and precision (RMSE:0.61 mm) in the clinical setup. The absolute median discrepancy between MRI and FTM-based anterior eye segment surface reconstruction was 0.43 mm (IQR:0.65 mm) ConclusionsThe system complied with the requirement of precision and accuracy for image guidance in ocular proton therapy radiation and is expected to be clinically tested soon to evaluate its performance against the current standard.

B-031 Digital Elisatotal 25-Hydroxyvitamin D

Abstract Evaluation of digital ELISA using a high-resolution computational optical system for measurement of total 25-hydroxyvitamin D Background Biomarkers such as vitamin D occur at very low concentrations in blood, and sensitive detection methods are required in order to measure them. It is difficult to accurately measure low-concentration biomarkers using conventional enzyme-linked immunosorbent assays (ELISA) with fluorescence staining. By developing a digital ELISA (DELISA, Small Machines, Seoul, Korea) platform, a low concentration substance was realized by analyzing the digitalized signal through a high-resolution computational optical system in a microfluidic chip. We evaluated DELISA for measurement of total 25-hydroxyvitamin D (25OHD) in a fluidic chip. Methods The sample with monoclonal antibody bead conjugates mixture was incubated for 20 min at 37°C, then 30 uL sample mixture was applied to inlet of the chip. After additional incubation for 2 min at room temperature and 2 min after sample application, 120 uL of washing buffer was applied onto the washing hole and the chip was incubated for 10 min. 25OHD molecules in the sample bond to magnetic beads coupled with anti-25OHD at the end of the membrane. Chips were inserted into DELISA, and 25OHD results were derived by analysis of the computational method of microscopic imaging, proportional to the concentration of 25OHD. Assay performance characteristics of the limit of detection (LoD), precision and analytical measurement interval (AMI) using Vitamin D Depleted, Low and High Serum (Molecular Depot, San Diego, CA) were determined according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. 87 Samples for method comparison studies were obtained from routine clinical samples submitted for 2 OHD determination or from apparently healthy normal volunteers. The study was approved by the Institutional Review Board of Dongguk University Ilsan Hospital (202207024). Results LoD was 10.3 ng/mL and within-laboratory precision was 11, 12, and 10% coefficient of variation at 14.1, 56.6, and 113.2 ng/mL, respectively. The best fit polynomial was a cubic equation from 14.1 to 113.2 ng/mL and the difference between the third-order equation and the first-order equation at Level 3 and 4 concentrations was outside the non-linearity limit. Comparison with chemiluminescent assay (Elecsys Vitamin D total II, Roche Diagnostics, Mannheim, Germany) yielded a 0.904 of correlation coefficient and 0.921 slope in the range from 7.0 to 57.9 ng/mL. Conclusions The DELISA 25OHD assay has a suitable LoD and precision, however, it is necessary to improve the AMI at high concentration values and correlation with the automated analyzer.

Mechanical properties evaluation of metacarpophalangeal joint prosthesis with new titanium-nickel memory alloy: a cadaver study

ObjectiveNi-Ti memory alloys are unusual materials for hard-tissue replacement because of their unique superelasticity, good biocompatibility, high strength, low specific gravity, low magnetism, wear resistance, corrosion resistance and fatigue resistance. The current study aims to evaluate its mechanical properties and provide biomechanical basis for the clinical application of the prosthesis.MethodsTen adult metacarpophalangeal joint specimens were randomly divided into a prosthesis group (n = 5, underwent metacarpophalangeal joint prosthesis) and a control group (n = 5, underwent sham operation). Firstly, the axial compression strength was tested with BOSE material testing machine to evaluate its biomechanical strength. Secondly, these specimens were tested for strain changes using BOSE material testing machine and GOM non-contact optical strain measurement system to evaluate the stress changes. Thirdly, fatigue test was performed between groups. Lastly, the mechanical wear of the metacarpophalangeal joint prosthesis was tested with ETK5510 material testing machine to study its mechanical properties.ResultsAxial compression stiffness in the prosthesis group was greater than that in the control group in terms of 30 ° and 60 ° flexion positions (P < 0.05). There was no statistically significant difference between two groups with regards to axial compression stiffness and stress change test (P > 0.05). In the fatigue wear test, the mean mass loss in the prosthesis group’s prosthesis was 17.2 mg and 17.619 mm3, respectively. The mean volume wear rate was 0.12%. There was no statistically significant difference in the maximum pull-out force of the metacarpal, phalangeal, and polymer polyethylene pads between the prosthesis group and the control group specimens.ConclusionsNi-Ti memory alloy metacarpophalangeal joint prosthesis conforms to the biomechanical characteristics of metacarpophalangeal joints without implants, and the fatigue strength can fully meet the needs of metacarpophalangeal joint activities after joint replacement.

Effect of rolling on crack behavior of FeCrAl alloys in ultra-long life

PurposeThe purpose of this paper is to determine (1) the relationship between microstructure and fatigue cracking behavior and (2) effect of rolling on the process of crack initiation and propagation in FeCrAl alloys.Design/methodology/approachThe qualitative and quantitative fracture studies were performed using scanning electron microscopy and the non-contact optical measurement system (IFMG5).FindingsThe results show that the formation of facets, rough facets and parallel stripes in the crack initiation and early crack propagation zones are closely related to the sensitivity of crack behavior to the microstructure of the material. Besides, the rolling process has a significant influence on the small crack initiation and propagation behavior. Quantitative analysis demonstrates that the size of the stress intensity factor and plastic zone size in the rough zone is associated with the rolling process.Originality/valueThe findings of this study have the potential to enhance the understanding of the microstructural crack formation mechanisms in FeCrAl alloys and shed light on the impact of rolling on the long-term and ultra-long fatigue behavior of these alloys. This new knowledge is vital for improving manufacturing processes and ensuring the safety and reliability of FeCrAl alloys used in nuclear industry applications.

Single- and double-wythe brick masonry walls subjected to four-point bending tests under different support conditions: Simply supported, rigid, non-rigid

Out-of-plane actions cause confined unreinforced masonry walls (URM) to develop what is known as an arching action. The role of arching is central in the resisting mechanisms of a wall; it contributes significantly to its loadbearing capacity as long as the wall’s deflections are minor, but gradually loses effect with increasing deflections, until collapse occurs. To date, limited experimental data is available on how arching develops in relation to the out-of-plane behaviour of the wall. This study brings new experimental evidence to this aspect. Quasi-static monotonic four-point bending tests were conducted on eleven brick wall strips, with reinforced concrete (RC) slabs affixed below and over the walls to simulate contact conditions of a typical construction system. The walls were tested vis-à-vis three different support conditions: simply supported, rigid, and non-rigid. The influence of these support conditions on the out-of-plane behaviour of the walls was studied on specimens with varying thickness – single and double wythe – and subjected to different levels of axial compression (or overload). While the former support condition was designed not to yield any arching inside the wall (unconfined masonry), the intermediate and latter solutions generated an arching action that was proportional respectively to the elongation of the wall (partially confined masonry), and its deflection (confined masonry). The walls were tested inside a bi-axial test setup that allowed not only the out-of-plane force but also the arching action to be measured, corroborating its central role in the development of the out-of-plane capacity of the walls. To support the observations, deformation characteristics and crack distributions were determined using two optical measurement systems placed in front and to the side of the walls, making use of the Digital Image Correlation (DIC) technique. The results of the tests are discussed in terms of failure mechanism as well as force and displacement capacity of the walls in relation to the investigated parameters. The test data is collected and made available to help with future research on the out-of-plane capacity of URM walls.

Leakage Monitoring and Quantitative Prediction Model of Injection–Production String in an Underground Gas Storage Salt Cavern

The leakage of the injection–production string is one of the important hidden dangers for the safe and efficient operation of underground salt cavern gas storage. Although distributed fiber optic temperature measurement system (DTS) can accurately locate the position of the string leakage port, how to establish the quantitative relationship between the temperature difference and leakage rate of the leakage port still needs further exploration. This paper proposes a new quantitative prediction model based on a DTS for the leakage monitoring of the injection–production string of salt cavern gas storage. The model takes into account the gas’s physical parameters, unstable temperature conditions, and the Joule–Thomson effect. In order to verify the accuracy of the model, a simulation experiment of string leakage based on a DTS was carried out. The test results show that the relative deviation between the predicted leakage rate and the measured value is less than 5% compared with the calculated value. When the leakage rate drops to 0.16 m3/h and the temperature range is less than 0.5 °C, it is difficult to accurately monitor the DTS. The results of this study help to improve the early warning time of underground salt cavern gas storage string leakage.

Miniaturization and Model-Integration of the Optical Measurement System for Temperature-Sensitive Paint Investigations.

The temperature-sensitive paint (TSP) method, an optical measurement technique, is used for qualitative skin friction visualizations in a wide variety of aerodynamic applications. One such application is the visualization of the laminar-turbulent boundary-layer transition. Optical access to the surface of interest is mandatory for the measurement system, which consists of scientific cameras and LEDs. But the optical access to the area of interest is often impeded by the available windows of the wind tunnel and the wind tunnel model itself, reducing the field of view and the spatial resolution. In some cases, it is of interest to increase the flexibility of the installation of the optical measurement system by reducing its physical dimensions and placing the installation inside the plenum. The DLR Swept flat PlatE Cross-flow TRAnsition (SPECTRA-A) configuration was selected to investigate the influence of two-dimensional steps on the cross-flow-induced boundary layer transition by means of TSP, as part of the EU project Clean Sky 2. The SPECTRA-A configuration consists of two main elements: a flat plate and a displacement body mounted within a very close distance of each other, creating a narrow gap between the two elements. The surface of interest is the area on the flat plate facing the displacement body. The narrow gap limits the utilization of an external camera setup due to poor optical access. A new optical setup consisting of four miniature CMOS machine-vision cameras and five miniature high-power LEDs was integrated into the displacement body. The characteristics of the camera system were analyzed in laboratory tests, establishing that the miniature CMOS machine-vision cameras are suitable for qualitative TSP skin friction visualizations. This was confirmed by successfully measuring the laminar-turbulent boundary-layer transition on the SPECTRA-A configuration. The integrated TSP system is capable of resolving even small variations of the transition location caused by changing the amplitude of the stationary cross-flow instability. The quality of the TSP visualization with the integrated optical system allows for the measurement of the transition location and the wavelength of the stationary cross-flow instability. Overall, a cost-effective TSP visualization system with small space requirements was developed and tested for future applications in wind tunnel models, model support, or side walls of wind tunnels.

Hundred-femtosecond-level concise optical time delay measurement system based on linear optical sampling

Fiber-delay measurement is one of the key fundamental technologies in numerous fields. Here, we propose and experimentally demonstrate a high-precision and concise optical time delay measurement system based on the technique of linear optical sampling, reaching the precision better than 100 fs under averaging. The use of only two optical frequency combs without locking the carrier-envelope-offset frequency greatly simplifies the structure of the time-delay measurement system. We also experimentally investigate the current limitations on the precision of the system. The timing jitter noises of two sources are mainly non-common mode and are both restricted to the frequency sources. Our results indicate that the proposed device can measure fiber length fluctuations below 10 µm, paving the way for further analyses of the external disturbances on the fiber link.

Optically pumped polarized [formula omitted]He[formula omitted] ion source development for RHIC/EIC

The proposed polarized 3He++ acceleration in RHIC and the future Electron-Ion Collider will require about 2×1011 ions in the source pulse. A new technique had been proposed for production of high intensity polarized 3He++ ion beams. It is based on ionization and accumulation of the 3He gas (polarized by metastability-exchange optical pumping and in the 5T high magnetic field) in the existing Electron Beam Ion Source (EBIS). A novel 3He cryogenic purification and storage technique was developed to provide the required gas purity. An original gas refill and polarized 3He gas injection to the EBIS long drift tubes, (which serves as the storage cell) were developed to ensure polarization preservation. An infrared laser system for optical pumping and polarization measurements in the high 3–5T field has been developed. The 3He polarization 80–85% (and sufficiently long ∼30min relaxation time) was obtained in the “open” cell configuration with refilling valve tube inlet and isolation valve closed. The development of the spin-rotator and 3He4He absolute nuclear polarimeter at 6MeV 3He++ beam energy is also presented.

Applications and limitations of distributed acoustic sensing in shallow seismic surveys and monitoring

Distributed acoustic sensing (DAS) is an emerging technology gaining acceptance in a variety of seismological applications. We systematically analyze the adaptability and usefulness of horizontal DAS deployments for near-surface geophysical applications, such as surface wave inversion, diving wave tomography, and passive subsurface source location. We find that, in accordance with previous studies, DAS data are generally similar to traditional sensors and can be successfully used independently. Nonetheless, DAS data suffer from inherent limitations due to the design of the optical measurement system. Among others, we identify the gauge length, measurement directivity, and saturation at near offsets as the primary limiting factors. When operating in low-velocity environments and a standard 10 m gauge length, surface wave analysis may be constrained to the usage of low frequencies due to the wavenumber filtering effect of the gauge length. The measurement directivity generally prohibits applications that are based on upgoing P-wave energy, such as near-offset diving wave tomography. In addition, saturation at near offsets prevents reliable diving wave traveltime picking. As a consequence of these limitations, the ultrashallow resolution achievable with DAS data is poor. Source directivity also strongly limits passive source location resolution. Whereas some of the limitations can be alleviated through an optimal choice of optical parameters at the interrogator level, we mostly rely on adapted field acquisition and data processing workflows that use the undisturbed portion of the recorded signal. Eventually, the spatiotemporal resolution and relative ease of long-term deployments turn DAS into a worthwhile option for monitoring and time-lapse scenarios, or when operating in urban environments over existing infrastructure.

High-throughput optical sensing of peri-cellular oxygen in cardiac cells: system characterization, calibration, and testing.

Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) represent a scalable experimental model relevant to human physiology. Oxygen consumption of hiPSC-CMs has not been studied in high-throughput (HT) format plates used in pre-clinical studies. Here, we provide comprehensive characterization and validation of a system for HT long-term optical measurements of peri-cellular oxygen in cardiac syncytia (human iPSC-CM and human cardiac fibroblasts), grown in glass-bottom 96-well plates. Laser-cut oxygen sensors having a ruthenium dye and an oxygen-insensitive reference dye were used. Ratiometric measurements (409nm excitation) reflected dynamic changes in oxygen, as validated with simultaneous Clark electrode measurements. Emission ratios (653nm vs. 510nm) were calibrated for percent oxygen using two-point calibration. Time-dependent changes in the Stern-Volmer parameter, ksv, were observed during the initial 40-90min of incubation, likely temperature-related. Effects of pH on oxygen measurements were negligible in the pH range of 4-8, with a small ratio reduction for pH > 10. Time-dependent calibration was implemented, and light exposure time was optimized (0.6-0.8s) for oxygen measurements inside an incubator. Peri-cellular oxygen dropped to levels <5% within 3-10h for densely-plated hiPSC-CMs in glass-bottom 96-well plates. After the initial oxygen decrease, samples either settled to low steady-state or exhibited intermittent peri-cellular oxygen dynamics. Cardiac fibroblasts showed slower oxygen depletion and higher steady-state levels without oscillations, compared to hiPSC-CMs. Overall, the system has great utility for long-term HT monitoring of peri-cellular oxygen dynamics in vitro for tracking cellular oxygen consumption, metabolic perturbations, and characterization of the maturation of hiPSC-CMs.

Method and Application of Spatial Positioning for Valid Temperature-measuring Optical Fibers in Concrete Dams

Spatial positioning of Valid Temperature-measuring Optical Fiber (VTOF) is of great significance for accurately grasping the real temperature distribution of a concrete dam. However, there is barely an effective way to accurately locate the measuring points of optical fiber in concrete dams. A comprehensive data symmetry analysis technique is presented for determining the optimal spatial positioning of valid temperature-measuring optical fibers (VTOFs) in concrete dams. This approach includes a mathematical model to confirm the center of symmetry in monitoring data, which is required to reconstruct the real spatial temperature distribution. This process can identify VTOF locations and verify the reliability of temperature predictions. Experimental validation was conducted using findings from research on a new mathematical model, site measurements from a concrete dam, and corresponding data from distributed optical fibers. These results were successfully applied to the construction of the Baihetan dam; the concrete temperature from 405 pouring blocks in 5 typical dam monoliths was accurately monitored, and the temperature-measuring points of VTOFs were more than 24711. Meanwhile, the optical fiber temperature measurement and temperature field analysis system of Baihetan dam located in southwest China was developed based on accurately acquired temperature measurement data, which provides data basis and engineering application platform support for temperature evolution and temperature field analysis and precise temperature control management of pouring blocks.

Displacement driven simulation and material calibration based on digital image correlation Part I - Theory

Standard material characterization methods for subsequent finite element analysis rely on the simulation utilizing ideally discretized specimen that represent its geometrical characteristics as in the real experiment. Since many material models hold a set of parameters which is dependent on the discretization, e.g. the mesh size, especially when failure prediction for crash analysis is relevant, various mesh sizes are utilized during this calibration process. Optical measurement systems accompanying the experimental tests have become a standardized procedure, at least for a 2-dimensional (or specimen top-surface) measurements. Investigated calibration methods relying on the results of these optical measurements either include the derived strain field into the characterization process (full-field calibration), determine the crack path and iteratively derive plasticity curves (stepwise-modelling approach) or establish virtual fields based on the principal of virtual work allowing to solve for the scalar unknowns of the underlying chosen constitutive equation (virtual fields method). In the presented work, we directly use displacements measured using a GOM/ARAMIS system, mapped as boundary conditions for the nodal displacements of differently discretized specimen to establish a material characterization scheme being as close to the experiment as possible.

A newly developed dilution system for optical particle size and concentration measurements in oil-injected screw compressors

Oil mist coalescence separators are widely used downstream of screw compressors. Unfortunately, due to high concentration most of the available literature reporting particle sizes in raw or clean gas of screw compressors is on model systems at atmospheric pressure and room temperature. To study oil mist coalescence separators under real-world conditions, the pressurized aerosol needs to be diluted.In this work, two newly developed isobaric and isothermal dilution systems for particle size measurements using an optical particle counter (200 nm–10 µm) in the application scenario are presented. For both systems, one a single-stage and the other a triple-stage system, transfer functions were determined in the laboratory using a pressurized oil atomizer.As a proof of concept, the triple-stage dilution system was used on a compressor test bench to study the influence of operating conditions (varying pressure and volume flow) on the particle size distribution and concentration in raw and clean gas. Both raw and clean gas particle size distributions showed most particles in the size range below 500 nm. The achievable dilution factor of 1000 was sufficient for measuring the raw gas concentration.On a second compressor test bench, the single-stage dilution system was used to study the influence of different coalescence separators on clean gas particle size distribution and concentration. Three separators were used for experiments: one industry-typical reference separator, one with less layers, and one with a weakened entrainment separation fleece. As expected, the particle size distributions showed clear differences, i.e., higher penetration or increased entrainment.Copyright © 2023 American Association for Aerosol Research

Gear Profile Measurement Based on Thin Line Structured Light

In order to achieve the high precision 3D measurement of gear tooth profile, a telecentric optical measurement system with large FOV (field of view), WD (working distance) and measuring range was proposed, the system was applied to the gear tooth profile measurement experiment and obtained a good effect. Firstly, the composition and the principle of the system were introduced. The lights of projection and imaging with an angle of 45° from the normal line of the measured surface can reduce the requirement of DOF (depth of field) of the imaging objective lens. Secondly, in combine with the application background of small modulus gear tooth profile measurement, the magnification, NA (numerical aperture) and other optical parameters were calculated, the optical system was constructed and the system performance parameters are listed. Then, the calibration model of the system was demonstrated and the calibrations of depth pixel resolution and horizontal pixel resolution were completed through experiments. Finally, an involute artifact with a modulus of 2.9992mm and a total tooth profile deviation of 1.1μm was measured. The results show that the deviation of the total tooth profile measured is about 2μm, which is consistent with the calibration curve of the involute artifact.