High-speed Camera Research Articles

Development of a DualEmission Laser-Induced Fluorescence (DELIF) Method for Long-Term Temperature Measurements.

The fluorescence intensity of fluorescent dyes typically employed in the dual-emission laser-induced fluorescence (DELIF) method gradually degrades as the excitation time increases, and the degradation rate depends on the type of fluorescent dye used. Therefore, the DELIF method is unsuitable for long-term temperature measurements. In this study, we focused on the fluorescence intensity ratio of a single fluorescent dye at two fluorescence wavelengths and developed a DELIF method for long-term temperature measurements based on this ratio. The fluorescence intensity characteristics of Fluorescein disodium and Rhodamine B, which are typically used in the DELIF method, in the temperature range of 10-60 °C were comprehensively investigated using two high-speed monochrome complementary metal-oxide semiconductor cameras and narrow bandpass filters. Interestingly, the ratio of the fluorescence intensity of each fluorescent dye at the peak emission wavelength of the fluorescence spectrum, λ, to the fluorescence intensity at wavelengths very close to the peak wavelength (λ ± 10 nm) was highly sensitive to temperature variations but not excitation time. Particularly, when Rhodamine B was used, the selection of the fluorescence intensity ratios at a wavelength combination of 589 and 600 nm enabled highly accurate temperature measurements with a temperature resolution of ≤0.042 °C. Moreover, the fluorescence intensity ratio varied negligibly throughout the excitation time of 180 min, with a measurement uncertainty (95% confidence interval) of 0.045 °C at 20 °C. The results demonstrate that the proposed DELIF method enables highly accurate long-term temperature measurements.

Fracture Mode and Thermal Damage Evolution of Sandstone Under the Coupling Effect of Thermal Treatment and Impact Load

The dynamic properties of high-temperature sandstone quickly deteriorate with different cooling methods, which leads to the instability of underground engineering rock structures. Therefore, it is of great significance to quantify the changes in the dynamic characteristics of high-temperature cooled sandstone under impact loads. Therefore, the sandstone is heated to different temperatures and cooled using three methods. A dynamic tensile test is performed using the Splitting Hopkinson Pressure Bar (SHPB) test set for high-temperature cooled sandstone. At the same time, the transient process of rock failure was examined using high-speed cameras. The influence of different temperatures and cooling methods on the thermal damage value of sandstone was analyzed, and the prediction equation was formed. The change in rock energy during rock failure under impact load was calculated.

Identification of flow patterns in an opaque condenser tube by distributed fiber Bragg gratings

Two-phase loops with phase change heat transfer are pivotal for cooling electronics under high heat flux and for thermal control in spacecraft. Numerous studies aim to clarify the mechanisms behind these loops to enhance cooling capacity and stability, which are closely tied to flow patterns. However, conventional flow pattern identification methods, requiring transparent tubes for direct observation, are impractical for simultaneous heat transfer measurement, especially during condensation. This paper introduces a novel approach for identifying flow patterns within an opaque, vertical condensation tube using embedded distributed fiber Bragg gratings (DFBGs) for R134a. The method involves a “fingerprint” derived from temperature profile derivatives and additional criteria based on temperature variation characteristics. These include the relative deviation from saturation temperature, the relative spatial temperature gradients, and the relative amplitude of temperature fluctuations. Validation against high-speed camera images confirms the method’s efficacy. It enables the determination of flow pattern lengths, the endpoint of condensation, and the construction of a flow regime map. Additionally, it allows for the measurement of vapor velocity in slug flow, facilitating the calculation of slip ratio and void fraction, which correlates reasonably with the Zuber-Findlay model, with systematic positive deviations up to 30%. This method also paves the way for simultaneous measurement of in-tube condensation heat transfer characteristics for various flow patterns.

Vapor Channel Oscillations in Laser Lithotripsy.

Laser-based endoscopic procedures present special challenges to deliver energy for ablation or coagulation of target tissues. When optical fiber-target quasi-contact (< 0.5 mm distance) cannot be maintained or is undesirable, the creation of intervening vapor bubbles and channels provide for the necessary transmission of laser energy to the target. This work investigates the characteristics and the dynamics of vapor channels that directly affect ablation efficiency and ablation rate and are known to effect stone movement, all of which impact procedure efficiency and safety. A simplified, experimental model for thulium fiber laser (1940 nm) lithotripsy consists of a water-filled cuvette and a vertically oriented laser fiber (200 μm core diameter) with its tip at 9 mm for "quasi-free" bubble generation and at vapor channel working distances 1-5 mm from and centered on the transparent cuvette bottom simulating a target's surface. Laser power transmission is recorded and synchronized with video frames from a high-speed camera (24,260 frames per second) to capture the induced vapor channels' and bubbles' development. Laser-induced channel transmission from 0% to 100% for 1, 2, and 3 mm fiber-target distances undergoes oscillations with average periods of 0.32, 0.64, and 1.0 ms, respectively, for 500 W laser output power. For fixed fiber-target distances of 0.5, 1, and 2 mm, the variation of these average oscillation frequencies across laser powers from 500 to 1000 W is much smaller, not exceeding 14%. For fiber-target distances in the range of 1-5 mm, the fraction of the 500 W laser's total pulse energy delivered to the target for 1, 2, and 3 ms pulses linearly decreases from 0.78 to less than 0.2. The channel and bubble dynamics begin with a spherical seed bubble expansion centered on the distal fiber tip that evolves into a pear shape whose surface exhibits periodic irregularities attributable to laser beam interruption by water droplets within the developing bubble. The study of laser-induced channel oscillations provides quantitative information relating fiber-target distance to channel oscillation frequency and energy transmission onto a target. These oscillations directly effect ablation efficiency and ablation rates that are important parameters for the optimization of a procedure's safety and duration. Insights that may lead to further reduction in retropulsion are also presented. Lasers Surg. Med. 00:00-00, 2024. © 2024 Wiley Periodicals LLC.

Multiscale Modeling and Simulation of Falling Collision Damage Sensitivity of Kiwifruit.

Falling damage is the most common form of damage sustained by kiwifruit during the process of picking and post-processing, and it is difficult to conduct a quantitative analysis of this phenomenon through traditional experimental methods. In order to deeply understand the sensitivity of kiwifruit to falling collision damage, the finite element numerical simulation method was used to evaluate and predict the sensitivity of kiwifruit to falling collision damage during harvesting. First, we obtained the appearance characteristics of kiwifruit through reverse engineering technology and determined the geometric and mechanical property parameters of kiwifruit through physical mechanics experiments. Then, according to the characteristics of fruit tissue structure, a multiscale finite element model, including the skin, pulp, and core, was constructed to simulate the effects of different falling heights, collision angles, and contact surface materials on fruit damage, and the accuracy of the model was verified through falling experiments. Finally, based on the simulation results, the Box-Behnken design was employed within the response surface methodology to establish a sensitivity prediction model for the drop damage sensitivity of kiwifruit across different contact materials. The results showed that the maximum relative error between the speed change obtained using finite element simulation and the speed obtained by the high-speed camera was 5.19%. The model showed high rationality in energy distribution, with the maximum value of hourglass energy not exceeding 0.08% of the internal energy. On the contact surface material with a large elastic modulus, a higher falling height and larger collision angle will significantly increase the risk of fruit bruise. When the contact surface material was a steel plate, the falling height was 1 m, and the collision angle was 90°; the maximum bruise sensitivity of kiwifruit reached 6716.07 mm3 J-1. However, when the contact surface material was neoprene, the falling height was 0.25 m, and the collision angle was 0°, the damage sensitivity was the lowest, at 1570.59 mm3 J-1. The multiscale finite element model of kiwifruit falling collision constructed in this study can accurately predict the damage of kiwifruit during falling collision and provide an effective tool for the quantitative analysis of kiwifruit falling collision damage. At the same time, this study can also provide guidance for the design and optimization of the loss reduction method of the harvesting mechanism, which has important theoretical significance and practical value.

Flow behavior and heat transfer characteristics of liquid film on vertical hot surface by inclined jet impingement

In this study, the flow behavior and heat transfer characteristics of the liquid film on the hot wall by inclined jet impingement are experimentally studied in detail. The effects of jet parameters, such as jet inclination angle, impingement distance, jet Reynolds number (Rej), and nozzle diameter are explored. The liquid film flow is visualized using a high-speed camera, and the surface temperature and heat flux are obtained by solving the inverse heat conduction problem. The results indicate that the liquid film shape is strongly affected by jet inclination angle but is almost unaffected by other parameters. As the inclination angle increases, the liquid film shape changes from elliptical to fusiform. In addition, the onset, enhancement, and disappearance of boiling cause the expansion and contraction of liquid film. The splashing rate is barely affected by jet parameters and remains within the range of 80–95 % under all conditions. The propagation of wetting fronts exhibits anisotropy. Except for the impingement distance, the position of wetting fronts along y-axis direction displays a high dependence on all parameters. The Rej and nozzle diameter have a significant effect on the heat flux at the impingement point and parallel flow zone, while the jet inclination angle and impingement distance only effect the impingement point. The visualization image proves that the droplet impingement pattern is the main reason for the increase in heat flux at higher impingement distances. Optimizing jet parameters can promote the wall to enter the rapid cooling stage in advance and increase maximum heat flux, thereby improving the maximum cooling capacity of the jet. Finally, an empirical equation is proposed to predict the maximum Nusselt number.

Investigation of spatial distribution characteristics of emission intensity in detachment on the divertor simulator TPDsheet-ICR

For the first time, we have revealed the spatial structure of a detached plasma with electron–ion recombination (EIR) and molecular-activated recombination (MAR) in response to changes in ion temperature (Ti) and gas pressure. This was achieved using high-density sheet plasma generated by a linear divertor simulator (TPDsheet-ICR). The parallel-plate electrodes were positioned above and below the sheet plasma (∼1019 m−3). We varied the Ti from 3 to 7 eV using ion cyclotron resonance heating and investigated the parameters of the detached plasma near the target in the divergent field region. Plasma emission intensities at Balmer series (Hα and Hγ) and Fulcher band wavelengths (610 ± 10 nm) were measured with a high-speed camera equipped with an Arbaa prism. Additionally, a Langmuir probe measured the electron density and temperature of the plasma. Our results show that as the Ti increases, EIR generated near the plasma periphery disappears, while MAR gradually forms near the plasma center during the transition from detached to attached plasma. This transition occurs because the increase in Ti in the detached plasma transfers energy from ions to electrons, raising the high-energy component of the electrons, resulting in EIR disappearance and the onset of MAR.

Temperature measurement method with line and continuum emissions in Ar-N2 DC arc

This study discusses a technique for accurate temperature measurement of thermal plasmas with a high-speed camera. The temperature of thermal plasmas is an important parameter for plasma processes. High-speed cameras are useful to measure plasma temperatures in two dimensions. Measurements of plasma emission with a high-speed camera and band-pass filter provide only the spectral intensity of the entire transmitted wavelength range. Temperature measurements with high-speed cameras by the Boltzmann plot method or Fowler⎯Milne method are less accurate. Theoretical consideration of the line and continuum emissions has improved the accuracy of plasma temperature measurement. The measurement target was a free-burning arc in an argon and nitrogen atmosphere. Temperature errors were estimated based on the deviation from the true emission coefficient. The calculation and measurement errors were discussed as the factors of the deviation. Error estimation provides important insight into the selection of the measurement wavelength.

Design of a new fiber-optical transmission-based fast ion loss probe on Experimental Advanced Superconducting Tokamak

For the first time, a new probe for fast ion loss has been developed for use in the Experimental Advanced Superconducting Tokamak (EAST) and utilizes optical fiber transmission, the aim of the probe is to study fast ion losses triggered by the ion cyclotron range of frequencies (ICRF) heating and neutral beam injection (NBI) synergy. This probe is used to determine the pitch angle and gyroradii of the ion losses based on the particle positions striking the two-dimensional scintillator. In this paper, the calculation and design of the probe scintillator by using the NLSDETSIM code is discussed. The emitted light from the scintillator is captured by a high-speed camera via an optical lens and high-temperature-resistant fibers and then processed by a signal processing system to determine the real-time energy and angle of the fast ion. Due to the flexible nature of the fiber, the probe is capable of measuring the fast ion losses at various locations within the EAST. Furthermore, the probe can be easily installed by using one of the numerous vacuum feeds on the EAST instead of occupying the entire window. This feature enhances the flexibility of the diagnostic technique.

Aerodynamic and rheological impact on aerosol generation in a synthetic larynx model

This study aims to investigate the fluid mechanical properties and particle dynamics of mucus in a biomimetic synthetic larynx model, focusing on aerosol and droplet formation under varying conditions of vocal fold adduction, oscillation frequency, and synthetic mucus liquids. A synthetic larynx model, equipped with multi-layered silicone vocal folds, was used to replicate human laryngeal dynamics and vocal fold oscillation. Two types of synthetic mucus, varying in visco-elastic properties, were used for aerosol generation. Vocal fold oscillations were driven by controlled airflow, and measurements of subglottal pressure, sound pressure levels, and particle velocities, which were acquired using high-speed cameras and laser-based high-speed particle image velocimetry. The surface of the synthetic vocal folds was treated to enhance wettability, mimicking human tissue more accurately. The study identified two distinct phonation modes characterized by different oscillation patterns and particle dynamics. The first phonation mode exhibited larger, more stable vortices and higher aerosol particle counts, while the second phonation mode showed higher oscillation frequencies with smaller, less coherent vortices and lower particle counts. The synthetic mucus with lower surface tension produced a higher number of aerosol particles and greater particle velocities compared to the mucus with higher surface tension. The results underscore the importance of mucus properties and vocal fold dynamics in aerosol generation. The study provides insights into the mechanisms of aerosol formation in the upper respiratory tract, with implications for understanding respiratory disease transmission.

Experimental DMD Analysis of Combustion Modes and Instabilities in a Scramjet Combustor

The combustion characteristics of a gaseous hydrogen fueled scramjet combustor were experimentally investigated through single-shot micro-pulse detonation engine (μPDE) operations across a range of fuel injection pressures and corresponding equivalence ratios. This study utilized a lab-scale direct-connect scramjet combustor integrated with a μPDE, designed to simulate flight conditions at Mach numbers between 4.0 and 5.0 at altitudes of 20 to 25 km. Static wall pressure was measured using 16 pressure probes from the isolator to the scramjet combustor at a sampling rate of 500 Hz. Additionally, Z-fold type Schlieren and flame luminosity were captured using a high-speed camera in a test section equipped with a quartz visualization window. Experiments were conducted under five conditions with equivalence ratios ranging from 0.10 to 0.55, each performed three times to ensure repeatability. Fast Fourier transform (FFT) and dynamic mode decomposition (DMD) analyses were applied to the pressure and image data obtained. Although auto-ignition was not achieved in all cases, combustion persisted while fuel was injected following the single-shot μPDE ignition. This allowed for the identification of distinct combustion modes according to equivalence ratio, by observing the dominant flame types and the shock structure within the flow of the combustor. These combustion modes showed different types of instability.

Liquid film breakup pattern and optimization of vane-type separator

The formation of liquid film and fragmentation downstream of swirler in vane-type separators, which is the key phenomena affecting the separation efficiency, is not well understood. To reveal the film breakup mechanism and the distribution characteristics of liquid film at the outlet of swirler, a visual vane-type separator test facility has been developed. By high-speed camera from the top, serious film breakup occurs in the rear of arc-vane swirler due to liquid accumulation on the hub and vanes is captured. While both bag breakup and ligament breakup are the dominant film breakup types, bag breakup resulting in divergent secondary droplets prolongs the gas–liquid separation path and is the main threaten to achieve high separation efficiency. New swirler using tilted-flat vanes with micro-pillars are proposed to guide the liquid film to migrate towards the wall of the riser and suppress liquid film fragmentation. Visual observation verified that the liquid film and fragmentation on the hub are significantly reduced. This is consistent with the quantitative measurement of void fraction distribution by wire mesh conductivity sensor (WMS). The average void fraction at the outlet of the new swirler (1.3D above) is increased, especially in low gas flow rate and high fluid flow rate cases, and the maximum increasement is as high as 26.0% compared to the original arc-vane swirler. The results deepen our knowledge about the film structure near the outlet of swirler in vane-type separators and provide guide to the optimization of vanes.

Binary collision dynamics of immiscible Newtonian and non-Newtonian fluid droplets

This experimental and theoretical study is devoted to the investigation of head-on collisions of two immiscible Newtonian and non-Newtonian droplets. The density of the two droplets is similar, and the viscosity of 0.3% carboxymethyl cellulose droplet is slightly larger than 10 cSt silicone oil. The sizes and relative velocity of the colliding droplets close to the point of impact are measured by means of image processing. The deformed states after the impact and their evolution with time are studied by experimental visualization and the energy evolution with time are discussed by numerical results. The accuracy of the two-dimensional axisymmetric three-phase flow computational model is validated. We study the effects of collisions of non-Newtonian droplets with Newtonian droplets and the subsequent retraction kinetics. Droplet “cannibalization” is commonly observed: after collision and spreading, the droplet retracts rapidly, resulting in a Newtonian droplet wrapping around a non-Newtonian droplet. We show the whole process of droplet collision captured by a high-speed camera and obtain the cloud and velocity vector maps of the droplets by numerical simulation. The droplet wrapping phenomenon is produced by different three-phase interfacial tensions and viscosities. We delineate the different phases of the collision process and discuss the dominant forces in each phase. We calculate the energy evolution of the spreading phase and use it to derive a predictive model for the dimensionless maximum spreading diameter and spreading time.

Laser Oscillation Diameter Variation Effect on Laser Wire Additive Manufacturing Deposition Morphology

A high-speed camera was employed to capture the melting process and investigate the impact of laser beam oscillation diameter on weld pool fluctuation and deposition morphology during laser wire additive manufacturing (LWAM) of 316L wire. The transient fluctuations of the weld pool caused by the laser beam were observed at different oscillation diameters. Additionally, 3D morphology measurements were conducted on the deposited layer to assess the effects of different oscillation diameters on its morphology. Further analysis examined the heat dispersion resulting from beam oscillation by plotting the energy distribution for various oscillation diameters. The key findings are as follows: Changes in oscillation diameter resulted in fluctuations within the weld pool that impacted the surface morphology of the deposit and refinement of pore condition as well as alterations in the energy distribution of the weld pool that influenced its contour geometry. Increasing the laser oscillation diameter can effectively make the keyhole shallower, weaken the bottom protrusion of the weld pool, and reduce the curvature of the top surface of the bead. Simultaneously, it can promote the stirring of the liquid solution, effectively refining the porosity area, reducing porosity within the weld pool, and improving the specimen’s density. However, larger oscillation diameters lead to more-significant hump arch formation on the deposited surface and larger roughness values.

Liquid breakup and droplets behavior of free triple-impinging jets with different impinging distance

The breakup characteristics and droplet behavior of free triple-impinging jets (FTIJs) were investigated using a high-speed camera. The liquid sheet and droplets breakup mechanism, liquid sheet breakup length, width, droplet diameter and velocity, were studied under different jet velocity and horizontal impinging distance and perpendicular impinging distance. The results revealed that with increasing jet velocity from 1.42 m/s to 6.61 m/s, different breakup modes were observed: closed-rim mode, open-rim mode, rimless mode, and wave or ligament mode. At low jet velocities, increasing impinging distance delayed the development of breakup mode. Based on experimental observations, the sheet breakup mechanism is categorized into two main regimes with four subregimes. Droplet breakup occurs in two stages: growth and necking, however, at high jet velocities complete breakup was achieved. Increasing jet velocity led to an increase in liquid sheet breakup length, width, and droplet velocity but a decrease in droplet diameter. Conversely, increasing impinging distance resulted in a decrease in liquid sheet breakup width and droplet radial velocity but an increase in droplet diameter. The effect of perpendicular impinging distance on axial velocity and breakup length was found to be more significant than that of horizontal impinging distance due to the effect of perpendicular nozzle. The findings indicate that the perpendicular jet greatly enhances atomization. This study provides a theoretical basis for designing and optimizing FTIJs.

Gait Kinetics in Medial Meniscus Posterior Root Tears: Investigating Protective Strategies and the Effects of Root Repair

Objectives To investigate changes in external moments in medial meniscus posterior root tear (MMPRT) patients, and the effect of medial meniscus posterior root repair (MMPRR) in restoring normal kinetics. Methods We present preliminary findings from six subjects with MMPRT, four with MMPRR, and three healthy age-matched control participants (CON). Participants walked on level ground at a self-selected gait speed. Data were collected using high-speed cameras and ground-embedded force plates. Peak knee moments for flexion-extension (KFM and KEM), abduction-adduction (KAbM, KAdM), and internal-external rotation (KERM, KIRM) were calculated using inverse dynamics during the stance phase of gait, and normalized to body mass and height. Group comparisons were conducted using the Kruskal-Wallis and Dunn test with Bonferroni correction. Results were considered statistically significant if p-values were less than 0.05. Results Both MMPRT and MMPRR groups exhibited significantly lower KFM relative to the CON group, suggesting a strategy to reduce quadriceps activation in both patient groups, which may persist after surgery. MMPRT patients showed significantly diminished KEM relative to both MMR and CON groups, indicating a strategy to reduce external knee forces following injury. MMPRR patients presented KEM that resembled the healthy control group, showing that repair surgery could potentially restore this gait variable. KAbM was statistically higher in the MMPRR and CON groups relative to MMPRT patients, which presented lower KAM than the other groups, suggesting a protective strategy to offload the medial compartment. KERM were significantly higher in the CON group compared to the MMT group, suggesting a protective strategy to avoid excessive external rotation by the MMT group. No significant differences were observed in KIRM across the three groups. Conclusion MMPRT leads to alterations in gait kinetics, compatible with a protective strategy to unload the knee and compensate for increased medial compartment contact pressures, which are partially restored following root repair.

Wave mode observation of hydrogen/oxygen driven rotating detonations in the hollow and annular rotating detonation rocket engine

The rotating detonation rocket engine (RDRE) fueled by hydrogen/oxygen propellant represents a promising propulsion technology due to its high thermodynamic efficiency and propellant superior specific impulse. The rotating detonation wave (RDW) must propagate in a specific propagation mode while maintaining the self-sustaining state to ensure stable operation. An experimental system of hydrogen/oxygen fueled RDRE was developed in the present study. The operation of RDRE and propagation mode of RDW were investigated under atmospheric pressure conditions, and both hollow and annular combustors were tested. The high-frequency pressure fluctuations in the RDRE were measured by the dynamic pressure transducer, while a high-speed camera was used to capture images of flame luminescence at the rear end of the RDRE. The experimental results showed that the RDW could be initiated and reached a self-sustaining propagation state with hydrogen/oxygen propellant in the hollow and annular RDRE. A single-wave mode, a two-wave co-rotating mode, and a three-wave co-rotating mode were visualized under different conditions. With the increase in the equivalence ratio, the number of rotating detonation fronts decreased, and the variations in the RDW propagation modes were consistent in the hollow and annular RDRE. However, when the equivalence ratio exceeds 1.2, the propagation velocity decreases sharply in the annular combustor, while in the hollow combustor the RDW propagates stably, revealing a higher upper limit for the equivalence ratio. Also, the dominant frequency distribution was more concentrated in the hollow combustor. The findings provide valuable insight into the variations in detonation modes related to the equivalence ratio and combustor configuration.

Influence of intensity distributions on the process dynamics during laser deep penetration welding of pure nickel with a flexible ring mode laser source

Current research results demonstrate the potential of spatter reduction in laser deep penetration welding by using adapted laser beam intensity distributions between a ring and a core intensity. The spatter-reducing effect, resulting from the additional ring intensity, is often attributed to an enlarged keyhole opening. However, it remains a matter of debate how exactly an additional ring intensity influences the process. This study, therefore, investigates the effect of an increasing ring intensity on process dynamics and the spatter formation regime. Laser beam welding experiments were carried out on 2.4068 nickel hidden T-joints at different welding speeds of up to 16 m/min, as well as different intensity distributions, while maintaining a constant weld depth. The tests were evaluated by using two high-speed cameras from different angles to analyze spatter and their formation mechanisms as well as the keyhole opening. Metallographic analyses and x-ray images were used to determine influences on the seam shape and porosity. It was shown that a change in intensity distribution has a significant influence on the melt flow, the resulting amount of spatter, and the porosity, which is comparable across the investigated welding speeds. While a core-based power distribution leads to spatter formation on the rear of the keyhole opening, it was shown that a ring-based power distribution leads to spatter formation on both sides of the keyhole. With an optimal power distribution, spatter formation could be largely prevented. Based on these findings, the single wave regime, a stabilized regime, and a lateral spatter regime were identified.

Dynamic visualization study of in situ cleaning of polystyrene microparticles off silicon wafer surface

With the improvement of chip performance, the requirements for cleaning the surface of silicon wafers are becoming higher. However, due to equipment and technology, it is difficult to observe the complex motion processes of particles at the microscopic scale. In this paper, an in situ dynamic visualization experiment on the cleaning of Polystyrene Latex (PSL) on the surface of silicon wafers is carried out by using a high-speed camera and image processing software. The mechanical behavior of PSL particles in fluid was investigated on a microscopic scale, and the trajectory and force of the polystyrene particles on the surface of the wafers were visualized, which provided a new perspective for understanding the complex cleaning process. Theoretical models were developed to explain the motion characteristics of the particles by calculating parameters such as van der Waals force, surface tension, and trailing force, and these models provide a theoretical basis for optimizing the cleaning process. There are four particle motion modes in the fluid: (1) interface capture, where the particles on the surface of silicon wafer are trapped by gas–liquid interface under surface tension; (2) particle collision, where the particles captured by the water film collide with the particles on the wafer surface to make the latter leave the silicon wafer; (3) jump attachment, where the particles jump and attach to the surface of the particle group under the action of lift; and (4) wall surface movement, where the particles start up under the action of water flow and then leave the silicon wafer quickly.

Distribution of bone fragments in angled shots: an experimental study conducted on composite models containing artificial bone plates.

In conventional gunshot injuries to targets containing bone the resulting osseous fragments do not precede but follow the bullet on its further way through adjacent soft tissues. The term "secondary projectiles" for the particles does not appear to be appropriate since they are not believed to have enough energy necessary for creating their own wound channels away from the temporary cavity. Former studies have shown that in angled shots to glass panes the bulk of splinters does not follow the bullet's trajectory: The majority of the glass fragments, especially the larger ones, move at right angles to the pane shot through. The aim of the presented study was to examine whether osseous fragments behave like glass splinters in angled shots to flat synthetic bone. In this context, it should also be assessed, whether the bone fragments might act as secondary projectiles in rare cases. To answer these questions, test shots were fired to composite models consisting of flat synthetic bone and ballistic gelatin. Pistol cartridges 9mm Luger were used to fire the shots which were video-documented with a high-speed camera. Afterwards, the composite models underwent CT examination and macroscopic inspection. Video-documentation revealed that the larger bone particles from the perforation site move at a roughly right angle from the osseous sheet into the gelatin, causing an eccentric bulge of the temporary cavity. The smaller bone fragments were also lodged along the bullet's path, predominantly in the cracks radiating from the permanent wound channel.