bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Mechanical Cycling at Elevated Temperatures on The Constitutive Properties and Microstructure of Lead Free Solder Alloys
Authors: Hoque Mohd Aminul , Haq Mohammad Ashraful , Suhling Jeffrey C. , Lall Pradeep
Published: November 2021

Solder joints in electronic packages often experience fatigue failures due to cyclic mechanical stresses and strains in fluctuating temperature environments. These stresses and strains are induced by mismatches in coefficients of thermal expansion, and lead to damage accumulation that contributes to crack initiation, crack propagation, and eventually to failure. In this study, we have tried to compare the effects of elevated mechanical cycling on SAC305 and SAC+Bi (SAC_Q). Initially, small uniaxial cylindrical samples of both alloys were prepared and reflowed in a reflow oven. These samples were then mechanically cycled for various durations at testing temperatures of 100 °C. The measured cyclic stress-strain curves were used to characterize the evolution of the hysteresis loop properties (peak stress, hysteresis loop area, and plastic strain range) with high temperature mechanical cycling. In addition, uniaxial tensile tests and creep tests were also conducted on specimens that had been previously mechanically cycled for various durations (e.g 0, 50, 100, 200, and 300 cycles) at an elevated temperature. This allowed us to study the evolution of the constitutive behavior of the solder alloys that occurred during the high temperature mechanical cycling due to the fatigue damage that builds up in the specimens. The reductions in the properties that occur during high temperature mechanical cycling were also correlated with the corresponding changes in the microstructure of the specimens. Rectangular cross-sectioned samples of the two lead free solder alloys were polished and selected regions indented to track the changes in the microstructure of a fixed region with mechanical cycling at T = 100 °C. Using the results of this study, we are working to develop better fatigue criteria for lead free solders which are subjected to variable temperature applications.
Design for Reliability of Automotive Chip Scale Packages by Calibrated Virtual Prototyping
Authors: Döring Ralf , Dudek R. , Rzepka S. , Scheiter L. , Noack E. , Seiler B.
Published: November 2021

The thermomechanical reliability of the package and interconnections of assembled flip chip ball grid arrays (FC-BGA) is investigated in comparison to a reference chip scale package (CSP). Comparison is made using finite element (FE-) simulation.

A combined measuring-simulation technique is applied to calibrate the finite element simulations on a reference object. Adjustment is made based on the in-plane deformation field evaluated by both simulation and optical measurement. For the latter an optical sensor for in-plane deformation and strain field analysis is used based on grey scale correlation method. A methodology is presented and to extrapolate the knowledge gained to alternative package types of different but similar design in order to evaluate their suitability for the desired application before the physical fabrication (virtual prototyping).
Determination of High and Low Temperature High Strain Rate Mechanical Properties for SAC-R After Exposure to Isothermal Aging of 50°C Up To 8 Months
Authors: Lall Pradeep , Saha Mrinmoy , Suhling Jeff , Blecker Ken
Published: November 2021

Electronic parts may be subjected to continuous activity at high temperatures as well as high strain-rate loads in the oil exploration industry, military, automotive, avionics, and space applications, and parts may be stored in non-climate-controlled enclosures prior to deployment. Material properties evolve at even moderate temperatures after a long period of storage, according to previous studies on undoped SAC alloys. To reduce the aging effects, a number of alloy formulations have been proposed. Data on the mechanical properties of lead-free solder alloys used for interconnection in electronic packaging at high strain rates and high storage temperatures is very important for design optimization of electronic package sustainability at extreme temperatures, since SAC soldiers have shown degradation of mechanical properties after prolonged exposure to storage temperature. The use of dopants in SAC solder has been proposed as a solution to minimize degradation. In this study, After keeping the samples in storage at 50°C for 1–8 months, a doped SAC solder called SAC-R (Ecolloy) was subjected to high strain rate testing. Uniaxial impact hammer tensile tests were conducted on samples with no aging and samples that had been aged for up to 8 months to assess the mechanical properties of SAC-R at high and low operating temperatures ranging from −65°C to 200°C and the Mechanical properties has been compared with an undoped solder SAC 105. The constants for the Anand Visco-Plasticity model were calculated using the material data for SAC-R. By comparing model predictions of the uniaxial tensile test with experimental results, the model’s ability to reflect material constitutive behavior has been quantified.
Performance Characteristics of Additively Printed Strain Gauges Under Different Conditions of Temperature and High Stress Loads
Authors: Lall Pradeep , Thomas Tony , Narangaparambil Jinesh
Published: November 2021

Applications of printed sensors have increased to industrial, consumer electronics, and medical fields with the advancements in the technology of printing and the adaptability of ink. These sensors are used to monitor a variety of measurements, including temperature, humidity, strain, and sweat, with different systems. This paper studies the performance characteristics of additively printed strain sensors using a nScrypt machine with a direct-write printing technique. The ink used in this study is silver ink which is thermally cured and also has a solderable property. The thermal curing temperature and trace width of the printed silver trace is optimized for better performance in the strain measurements, shear load to failure, and resistivity. Once the printing characteristics of the trace are defined, strain gauges are printed on printed wiring boards (PWB) and are tested at different loading and temperature environments. The sustainability and repeatability of the sensor measurements at high-stress conditions are studied using combined temperature and vibration loads of up to 50 degrees Celsius and 10g acceleration levels. The strain characteristics of the printed strain gauges are studied by comparing them to a commercial strain gauge at a similar position on the test substrate. The repeatability and variation of the strain profile are studied with different conditions of temperature and acceleration conditions at different time instants during vibration. The gauge factor of the printed strain gauge is quantified using a 3-point bending experiment with printed and commercial strain gauges at symmetrical locations of the substrate.
Cooling of High Powered GPUs Using Liquid Nitrogen Cold Plates Made With Additive Manufacturing
Authors: Nordlund Alec , McAfee Rachel , Ledsham Rebecca , Gess Joshua
Published: November 2021

Processor energy density is exceeding the capabilities of conventional air-cooling technology, but two-phase cooling has the potential to manage these resulting heat fluxes at reliable temperatures and higher electrical efficiency. When two-phase cooling is used in tandem with overclocking, data center footprints are reduced as individual chip processing power can be set at limits well beyond the manufacturer’s Thermal Design Power (TDP) or nominal operating condition. This study examines how Liquid Nitrogen (LN2) can be used with Additive Manufacturing (AM) and overclocking to increase the computational performance of a commercially available GPU. The power consumption and frequency relationship were established for both the cryogenically cooled solution and a comparative air-cooled solution. The cryogenic solution saw up to a 17.4% increase in compute efficiency and an 18.1% improvement in compute speed with comparable power efficiency at an equivalent performance level to the air-cooled solution. This study considers the computational performance and efficiency gains that can be acquired through cryogenic cooling on an individual graphics card, which can be replicated on a larger scale in data center applications.
ACOUSTICAL SOCIETY OF AMERICA Silver Medal in Animal Bioacoustics 2021: Peter M. Narins
Authors: Narins Peter M.
Published: November 2021

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
ACOUSTICAL SOCIETY OF AMERICA Silver Medal in Psychological and Physiological Acoustics 2021: Ruth Y. Litovsky
Authors: Litovsky Ruth Y.
Published: November 2021

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
ACOUSTICAL SOCIETY OF AMERICA Silver Medal in Biomedical Acoustics 2021: William D. O'Brien, Jr.
Authors: O'Brien William D.
Published: November 2021

The Silver Medal is presented to individuals, without age limitation, for contributions to the advancement of science, engineering, or human welfare through the application of acoustic principles, or through research accomplishment in acoustics.
A cylindrical expansion of the audio sound for a steerable parametric array loudspeaker
Authors: Zhong Jiaxin , Kirby Ray , Karimi Mahmoud , Zou Haishan
Published: November 2021

In this work, a cylindrical expansion for the audio sound generated by a steerable baffled parametric array loudspeaker (PAL) based on the phased array technique is derived from the Westervelt equation. The expansion is a series of twofold summations with uncoupled angular and radial components in the cylindrical coordinate system. The angular component is determined by the trigonometric functions, and the radial component is an integral containing the Bessel functions and an arbitrary excitation velocity profile. The numerical results for a typical steerable PAL are presented and compared to those obtained using the convolution model. It is found that the prediction of the audio sound using the proposed cylindrical expansion improves the agreement with the experimental results when compared to the existing models. This is because no further approximations are required in the cylindrical expansion of the quasilinear solution of the Westervelt equation, whereas the complex near field nonlinear interactions between the ultrasonic waves cannot be correctly captured in a convolution model. The proposed cylindrical expansion does, therefore, provide an alternative approach to modeling a phased array PAL and high accuracy with a relatively low computational cost.
Sound isolation from a consultant’s perspective
Authors: Hoover K. Anthony
Published: November 2021

Sound isolation addresses transmission between adjacent spaces as well as non-adjacent spaces, related horizontally and vertically, interior/interior and interior/exterior, through flanking paths and weak links and crosstalk, via both airborne and structure borne “paths.” Isolation can be characterized using single-number descriptors, such as Sound Transmission Class (STC) and Impact Insulation Class (IIC), but there are important limitations and caveats. Isolation and methods for improvement are all often misunderstood and misused, especially with an ocean of misinformation and confusion to navigate on the web and elsewhere. This presentation is intended to offer practical, helpful guidance from a consultant’s perspective, with focus on fundamentals and simplicity, toward better overall understanding and effective interactions with colleagues and clients.
Mixed layer acoustic propagation with small scale ocean dynamics
Authors: Richards Edward , Colosi John A.
Published: November 2021

The effects of dynamic oceanographic processes in the upper ocean mixed layer on acoustic propagation are investigated using at-sea sound speed observations and acoustic transmission simulations. The sound speed environment is based on a 400 m deep and 1000 km long East-West salinity and temperature transect that was collected during April of 2005 in the North Pacific where there is a mixed layer acoustic duct with a mean depth of 89 m. The deterministic baseline of this sound speed measurement is first estimated from the observations using a spatial lowpass filter with a cut off length scale of 50-km. The remaining small length scale variations in sound speed are assumed to have two physically distinct contributions: one due to the vertical displacement of isopycnals caused by eddies and internal waves and another due to compensating temperature and salinity anomalies along isopycnals termed spice. These two contributions can be separated yielding three distinct sound speed fields: i(1) the deterministic background; (2) thedisplacement field; and (3) the spice field. Acoustic transmission loss calculations are carried out on these three fields for frequencies of 400 and 1000 Hz for sources both in and below the mixed layer duct. Statistical and deterministic results for acoustic normal modes and full field transmission loss are presented, which quantify the relative importance of displacement and spice for acoustic propagation in the upper ocean.
Physics-informed neural networks for predicting ocean spatio-temporal fields
Authors: Thilges Kayla , Plumley Meredith , Summers Jason E. , Arbic Brian K. , Buijsman M. C.
Published: November 2021

Simulations of the ocean environment are important for assessing acoustic variability due to large and small scale changes in the propagation medium. By incorporating the Internal Gravity Waves (IGWs) partial differential equation (PDE) in ocean models, such as the HYbrid Coordinate Ocean Model (HYCOM) system, it is possible to model the impact of tides on acoustic propagation. This requires HYCOM simulations of the ocean environment, which are computationally expensive, especially at the high vertical resolutions required to capture IGWs. In this work, we develop a machine-learning approach to predicting the effects of IGWs without incurring the computational cost of high-resolution numerical modeling. We apply a deep-learning approach in the form of a Physics Informed Neural Network (PINN) that incorporates the IGW PDE system to make predictions about oceanographic quantities of interest with internal tides at high vertical resolution. Training data comprise HYCOM 4D fields (time, depth, latitude, and longitude) both with (IGW-HYCOM) and without tides in the Pacific subtropical/equatorial region. The developed framework is able to map a relationship between lower-resolution HYCOM inputs to highly resolved ocean fields that include internal tides.
Lipid-stabilized hydrophobically modified silica-coated gold nanorods generate enhanced photoacoustic signal from cavitation with nonlinear dependence on laser fluence
Authors: Goodwin Andrew
Published: November 2021

In this work, we report that gold nanorods coated with hydrophobically modified mesoporous silica shells not only enhance photoacoustic (PA) signal by more than 10-fold over unmodified mesoporous silica coated gold nanorods but also the relationship between PA amplitude and input laser fluence is strongly nonlinear. Mesoporous silica shells of ∼14 nm thickness and with ∼3 nm pores were grown on gold nanorods showing near infrared absorption. The silica was rendered hydrophobic with addition of dodecyltrichlorosilane, then re-suspended in aqueous media with a lipid monolayer. Analysis of the PA signal revealed not only an enhancement of PA signal compared to mesoporous silica coated gold nanorods at lower laser fluences but also a nonlinear relationship between PA signal and laser fluence. We attribute each effect to the entrapment of air in the mesopores: the air has a larger expansion coefficient than silica that enhances conversion to acoustic energy, and the air undergoes thermal size oscillations that increase with laser fluence, leading to a nonlinear trend even at fluences as low as 5 mJ cm−2. At 21 mJ cm−2, the highest laser fluence tested, the PA enhancement was >12-fold over mesoporous silica coated gold nanorods.
High intensity focused ultrasound and microbubbles induce targeted mild hyperthermia suitable for enhanced drug delivery
Authors: Juang Eric , De Koninck Lance H. , Gnanaskandan Aswin , Hsiao Chao-Tsung , Averkiou Michalakis A.
Published: November 2021

High intensity focused ultrasound (HIFU) can elevate the temperature leading to tissue ablation (>60 °C). Mild hyperthermia (39–45 °C) can enhance drug delivery such as in the activation of thermosensitive liposomes for chemotherapy and in radiotherapy. The addition of microbubbles during HIFU could greatly enhance the heating process and increase the treatment area while operating at lower intensities. Here, we present a parametric study of microbubble-enhanced mild hyperthermia with HIFU in ex vivo porcine liver. A 30-s treatment at 0.9 MHz, 372 000 cycles, 82% duty cycle was used, and at estimated non-derated (water) pressures of 0.63, 1.25, 2.50 and 3.75 MPa. The microbubbles were injected locally in the treatment area. The measured temperature rise was greater with microbubbles than without at low acoustic pressures (0.63 and 1.25 MPa). At higher pressures (2.50 and 3.75 MPa), the presence of microbubbles did not have an effect on the measured temperature rise possibly due to inertial cavitation. Our results agree with predictions from a numerical model that solves the coupled acoustic-bubble flow fields with a two-way coupled Euler–Lagrange model. Future work will utilize the numerical model and new measurements to optimize targeted mild hyperthermia before applying it to enhanced drug delivery.
Reliable and safe blood–brain barrier opening by closed-loop feedback control of focused ultrasound
Authors: Chien Chih-Yen , Gong Yan , Yang Yaoheng , Yue Yimei , Chen Hong
Published: November 2021

Real-time cavitation monitoring and feedback controller is critical to safe and effective brain drug delivery by focused ultrasound (FUS)-mediated blood-brain barrier disruption (FUS-BBBD). However, existing controllers were either open-loop or using a generalized target cavitation level (TCL). This study aimed to develop a closed-loop feedback controller with TCL defined based on the baseline stable cavitation level (SCL) of each subject. A single-element FUS transducer with a coaxially aligned passive cavitation detector (PCD) was used. PCD signals were first acquired with “dummy” sonication to determine TCL defined to be 0.5, 1, 2, 3, or 4 dB above baseline SCL. A custom closed-loop feedback controller was developed to control SCL to be at each TCL. After sonication, wild-type mice were intravenously injected with Evans Blue (EB) to quantify FUS-BBBD using ex vivo fluorescence imaging. The fluorescence intensity of delivered EB increased in an average of 1.4-fold, 2.6-fold, and 3.9-fold at 1, 2, and 3dB respectively compared to the 0.5-dB group. No apparent hemorrhage was found in lower TCLs, and hemorrhage was consistently found in the 4-dB group. This study demonstrated that the individualized feedback controller achieved reliable and safe FUS-BBBD at selected TCL.
Micro-elastography on spheroids using a magnetic pulse as a shear wave source and the impact of cavitation on their mechanical properties
Authors: Laloy-Borgna Gabrielle , Lambin Thomas , Lescoat Gabrielle , ngo jacqueline , Perier Magali , Guillermet-Guibert Julie , Lafon Cyril , Catheline Stefan
Published: November 2021

In the context of development of a new treatment against pancreatic adenocarcinoma combining chemotherapy and cavitation, it is interesting to be able to mechanically characterize spheroid tumor models. Spheroids, which are clusters of cancerous cells (KPC) and fibroblasts (iMEF), are made using magnetic nanoparticles which are linked to the cells. Then, by using magnetic cell culture plates, cells aggregate, until forming a spheroid. Hence magnetic nanoparticles are incorporated in the spheroid, and can be used to generate elastic waves inside. A 5-ms magnetic pulse is induced in a coil, allowing to induce vibrations inside the spheroid placed in its center. It is observed using an optical microscope and an ultrafast camera. Then, tracking algorithms allow to measure the displacements at each point of the image, and for each time step. Next, noise correlation algorithms are used to retrieve the local velocity of shear waves inside the spheroid. Therefore, we obtained shear wave velocity maps of spheroids, using a non-destructive method. The influence of trypsine (known for disrupting the bounds between the cells) on shear wave velocity maps has been studied. As expected, a decrease in the wave velocity has been observed, attesting that this method is sensitive to elasticity. Furthermore, the impact of cavitation inside the spheroid has been investigated. Cavitation designates the bubble generation using ultrasound. It has been shown that cavitation also leads to a substantial decrease in the velocity of shear waves.
An ex vivo investigation of ultrasonic shear wave imaging for detecting liver cracks
Authors: Liu Jingfei
Published: November 2021

Liver crack is a type of liver trauma in which a capsular tear of different geometries occurs due to external impacts. Since liver crack is an important source of morbidity and mortality in emergency medicine, a timely and accurate detection of the crack location and geometry is highly demanded. In current emergency care, ultrasonography, although has a low accuracy, is mostly used for initial examination of liver trauma due to its immediate availability, high mobility, and nonionizing nature. To improve the diagnosis accuracy, ultrasonic shear wave imaging, a technique based on shear wave generation and tracking in liver tissue, was proposed. In this study, the feasibility and effectiveness of this method was investigated in an ex vivo scenario. A porcine liver with cracks of different geometries was tested. Shear waves were generated using acoustic radiation force impulse and recorded using ultrafast ultrasound imaging. To find the best way to display the cracks, different methods of signal processing based on time-of-flight, shear wave modulus, and accumulated shear wave path were applied to the shear wave displacement extracted. The results show that shear wave imaging is a more sensitive method than the conventional ultrasonography in detecting liver cracks.
Investigation of transcranial ultrasound delivery via Lamb wave mode conversion leveraging a transducer pair
Authors: Mazzotti Matteo , Kohtanen Eetu , Erturk Alper , Ruzzene Massimo
Published: November 2021

Cranial Lamb waves have been recently proposed for the non-invasive identification of the mechanical properties of the cranial bone, the evaluation of its acoustic radiation characteristics, and the estimation of the elastic and transmission properties of cranial sutures. Few works have focused on the so-called Lamb mode conversion phenomenon for transcranial ultrasound delivery, in which an attempt was made to control the focal point within the brain for incident acoustic beams beyond the critical angle. In our study, we further investigate this problem by overcoming some of the limitations of previous works, which are mainly related to the use of simplified geometries and material properties. To this end, we experimentally and numerically investigate leaky Lamb waves in immersed cranial bones by adopting a two-step strategy. In the first step, the dispersion properties of leaky Lamb waves are retrieved in the 0–500 kHz range along the mechanical properties of the cranial bone layers. The material data are then used to determine, via numerical simulations, the range of frequencies in which Lamb mode conversion can be effectively exploited for transcranial focusing purposes. Finally, we experimentally validate the numerical findings by means of an immersed setup that utilizes a pair of ultrasonic transducers.
Human skull profile and speed of sound estimation using pulse-echo ultrasound signals with deep learning
Authors: He Churan , Jing Yun , Han Aiguo
Published: November 2021

Transcranial ultrasound brain imaging in human adults remains challenging, largely because human skulls cause severe phase aberration. Prior research has shown that phase aberration can be most accurately corrected if the skull profile (i.e., thickness distribution) and speed of sound are known apriori. We propose a deep-learning-based method to estimate the skull profile and sound speed from pulse-echo ultrasound signals. To demonstrate the feasibility of the method, k-wave simulations were performed to generate ultrasound radiofrequency (RF) signals backscattered from the skulls, using density and speed of sound maps derived from diagnostic CT scans of 5 ex vivo human skulls. An unfocused single-element transducer was simulated for ultrasound transmission and receiving at 0.75 MHz with 4-cycle tone bursts. A one-dimensional convolutional neural network (1D-CNN) model was designed and trained to predict the skull thickness and sound speed from RF signals. In an independent test set, the model yielded a mean absolute error of 0.3 mm for skull thickness prediction and 31 m/s for sound speed prediction. The result demonstrates that the deep learning method is capable of accurately estimating skull thickness and speed of sound, providing a potentially powerful tool for skull phase aberration correction in transcranial ultrasound brain imaging.
Phase in bubble echoes due to nonlinear response improves contrast in ultrasound images
Authors: Lai Ting-Yu , Keller Sara , Averkiou Michalakis A.
Published: November 2021

The image quality of contrast-enhanced ultrasound (CEUS) is limited by the tissue harmonics generated from the nonlinear propagation of sound waves, even at low amplitudes. Amplitude modulation (AM) is typically implemented by firing a full aperture and two complimentary half apertures. A phase difference (ΔΦΑΜ) between the echoes from the full and half pulse has been observed which is lower for tissue than bubble echoes. This phase difference may be used as a segmentation criterion for tissues and bubbles to improve contrast to tissue ratio (CTR) of CEUS images. This technique may be further expanded by considering also the phase difference (ΔΦhalf) between the complementary half amplitude pulses of the AM scheme (ΔΦhalf). This additional phase difference results from the spatial differences of the complementary half amplitude fields. We considered the change in ΔΦhalf when using various aperture patterns for AM. We observed that ΔΦhalf increases as the complementary fields become spatially dissimilar. For certain aperture patterns, we found that the phase difference between the echoes of the complementary apertures was greater than that between the full and half pulse (ΔΦhalf i> ΔΦΑΜ) and that it further contributed to the image CTR.
In vivo assessment of pulmonary edema in rats using the backscatter coefficient and envelope statistics
Authors: Lye Theresa H. , Roshankhah Roshan , Egan Thomas M. , Muller Marie , Mamou Jonathan
Published: November 2021

Ultrasound could be used as a convenient, non-ionizing method for monitoring pulmonary edema. In this study, the ability of backscatter coefficient (BSC) and envelope statistical quantitative ultrasound (QUS) parameters to evaluate edema in rat lungs was investigated. Ultrasound data were acquired from six healthy rats and six with pulmonary edema using a Verasonics Vantage ultrasound scanner. After ultrasound data acquisition, a piece of the lung was excised and immediately weighed (wet weight), before being dried in an oven and weighed again (dry weight). The wet and dry weight were used to compute the wet-to-dry (W/D) weight ratio, used as the gold standard for pulmonary edema severity. BSC and envelope statistical parameters were computed in overlapping time gates over the lung ultrasound data. The average and standard deviation of each parameter, along with the slope and intercept of a linear function fit to each parameter over acoustic propagation time, were obtained. Each QUS parameter was correlated with the W/D ratio. The strongest correlation was achieved by the standard deviation of spectral intercept and by the average homodyned K structure parameter, both with a 0.78 correlation coefficient magnitude. Therefore, BSC and envelope statistical parameters have the potential to improve monitoring of pulmonary edema.
Return to in-person teaching and mentorship after COVID-19: hands-on photoacoustic demonstration apparatus
Authors: Burge Leah E. , Korman Murray S.
Published: November 2021

In March 2020, the U.S. Naval Academy implemented policies for teaching midshipmen off the “yard” (campus) to finish out their spring semester online. Strategies and regulations were put in place so that after spring break midshipmen would go home to families, relatives or friends and establish a learning environment space for on-line synchronous or asynchronous classes. An online summer school served as a link into the fall of 2020— which was a mixture of online and very small in-class size environments. (Every other week half of a class was online.) During the spring of 2021, classes were hybrid. However, Instructors alternated between adjacent classrooms teaching online—but in-person in one of the rooms. During COVID, mentorship student LEB worked off the yard to develop apparatus for online acoustic demonstrations and future research projects. LEB designed and built a homemade pulsed 620 nm LED photoacoustic apparatus for imaging experiments in water. Components include an LED current pulse driver, two aspherical focusing lenses, a cuvette filled with green dye or India ink, an ultrasonic 1 MHz immersion transducer and 4 low noise amplifiers with 87 dB total gain. Photoacoustic signals were averaged (10 000 trials) producing a strong 20 mV seven cycle pulse.
Individual undergraduate research during remote learning
Authors: Riegel Kimberly A.
Published: November 2021

Due to the COVID-19 pandemic Queensborough Community College converted all learning to remote instruction. The college has remained fully remote from March 2020 until the present. During this time, the Queensborough ACousticS group (QuACS) continued to conduct individual undergraduate research. The author oversaw the NSF REU in a remote setting in the summer of 2020 and in a hybrid modality in the summer of 2021 including all professional development and logistical activities. For the first time, the program was able to accept students from community colleges as far away as California. This paper will highlight some suggestions about how to conduct remote research effectively. In addition, some observations about the difficulties of overseeing a remote undergraduate research program will be provided. Using the lessons learned from this remote experience, how to carry these lessons forward to enhance a traditional in person research experience will be discussed.
Fruitful femtofluidics using fast (acousto)fluidics
Authors: Zhang Naiqing , Horesh Amihai , Manor Ofer , Friend James
Published: November 2021

Acoustic streaming relies upon viscous attenuation of a propagating acoustic wave in a fluid to generate momentum flux and fluid flow. It is a nonlinear second-order phenomenon that generally produces rapid (∼10 cm/s) fluid flow but only against weak (∼10 kPa) pressure gradients. Here we describe a new form of acoustic streaming—acoustogeometric streaming—that is still nonlinear but relies on the interaction between the acoustic wave and the bounds of the fluid passage. If the boundaries oscillate with an amplitude that is significant in comparison to the width of the fluid passage, similarly rapid fluid flows may be generated even against very large (>1MPa) pressure gradients. This is used to propel fluids at 6 mm/s in 20–150 μm wide, 100 nm tall nanoslit geometries and to transport, split, combine, and mix ∼100 fl droplets of fluid. In this presentation, we will also show what happens when the nanoslit height is reduced below 10 nm, and demonstrate specific examples with some simple analysis that explains the various phenomena, closed by some explanation of the broader potential benefit of this approach.
Theory for attenuation and dispersion of acoustic propagation through a muddy medium
Authors: Pierce Allan D.
Published: November 2021

Mud as a medium typically consists of clay particles, small silt particles (primarily quartz), and water. The clay particles lock together in what is called a card-house configuration, and the silt particles are held in suspension by the card house. The low frequency velocity of sound waves appears to be well-predicted by the Mallock-Wood theory that gives weighted averages of bulk compressibility and material density. At low frequencies, the attenuation is caused by the viscous dag of the water on the suspended silt particles, and the attenuation varies as the frequency squared. The deviation of the phase velocity from the low frequency limit at low frequencies is less well-understood but appears to vary as the frequency to the three-halfs. At higher frequencies, the dominant mechanism appears to be a relaxation mechanism associated with the card house. Each clay particle carries a net electrical charge and the resulting repulsion forces the clay particles to be spatially separated. However, the particles tend to stick together edge to face, and the van der Waals attraction between the clay particles tends to dominate over the electrostatic repulsion. However, the passage of a sound wave temporarily breaks some van der Waals bonds and they subsequently recombine as the acoustic pressure ebbs. The present paper seeks to quantify the effects of the relaxation processes. It is demonstrated that the latter leads to an attenuation that, at higher frequencies, varies nearly linearly with frequency. [Work supported by ONR.]
Modulation of acoustofluidic parameters to assess effect on molecular loading in human T cells
Authors: Centner Connor , Moore John , Baxter Mary , Vinseiro Figueira Mariana , Long Zachary , Belott Clinton , Menze Michael , Bates Paula , Yaddanapudi Kavitha , Kopechek Jonathan A.
Published: November 2021

T-cell therapies are rapidly emerging for treatment of cancer and other diseases but are limited by inefficient non-viral delivery methods. Acoustofluidic devices are in development to enhance non-viral delivery to cells. The effect of acoustofluidic parameters, such as channel geometry, on molecular loading in human T cells was assessed using 3D-printed acoustofluidic devices. Devices with rectilinear channels (1- and 2-mm diameters) were compared directly with concentric spiral channel geometries. Intracellular delivery of a fluorescent dye (calcein, 100 μg/ml) was evaluated in Jurkat T cells using flow cytometry after ultrasound treatment with cationic microbubbles (2.5% v/v). B-mode ultrasound pulses (2.5 MHz, 3.8 MPa output pressure) were generated by a P4-1 transducer on a Verasonics Vantage ultrasound system. Cell viability was assessed using propidum iodine staining (10 μg/ml). Intracellular molecular delivery was significantly enhanced with acoustofluidic treatment in each channel geometry, but treatment with the 1-mm concentric spiral geometry further enhanced delivery after acoustofluidic treatment compared to both 1- and 2-mm rectilinear channels (ANOVA p < 0.001, n = 6/group). These results indicate that 3D-printed acoustofluidic devices enhance molecular delivery to T cells, and channel geometry modulates intracellular loading efficiency. This approach may offer advantages to improve manufacturing of T cell therapies.
Acoustic radiation force and torque on objects with continuous and discrete inhomogeneity
Authors: Jerome Thomas S. , Hamilton Mark F.
Published: November 2021

At the Fall ASA meeting in 2019, the Born approximation was extended to acoustic radiation force and torque on objects of arbitrary shape with spatially varying density and compressibility [Proc. Meet. Acoust. 39, 045007 (2020)]. This model is applied here to a standing plane wave incident on objects either with continuously varying material properties or composed of connected homogeneous regions with different material properties. The approximation for inhomogeneous objects is subject to the same restrictions on incident field structure, scatterer size, and material contrast as for homogeneous objects. Results are presented for cylinders with a variety of strongly asymmetric inhomogeneity distributions. Closed-form expressions are obtained for a sphere with material properties that vary linearly with distance from its center and for a sphere surrounded by concentric spherical layers. Results for the latter case are shown to be in close agreement with existing theory for the radiation force on a nucleated cell modeled as a multilayered compressible sphere [Wang et al., J. Appl. Phys. 122, 094902 (2017)]. The Born approximation thus proves convenient for determining radiation force and torque on soft objects with both arbitrary shape and inhomogeneity. [TSJ was supported by the ARL:UT McKinney Fellowship in Acoustics.]
Remote acoustic sensing of damage in vibrating plates
Authors: Dowling David R. , Flynn Tyler J.
Published: November 2021

The presence of damage in a structure often changes its vibrational characteristics. For example, resonant frequencies and mode shapes may be changed in a damaged structure relative to a healthy counterpart. For structures immersed in a fluid medium, these changes alter the radiated sound such that passive recordings can be examined to glean information about the damage. This approach toward structural health monitoring enjoys the benefit of being non-contacting, allowing sensors to be independent from the system of interest, but comes at the cost of introducing challenges associated with the acoustic environment and exogenous noise. In this presentation we describe a set of remote acoustic techniques for detection, localization, and classification of damage in base-excited clamped plates in a reverberant environment. This is accomplished by measuring audible broadband sound (0.2–6 kHz) from 12 × 12 × 1/16 in3 plates with and without damage in an ordinary laboratory using a remote microphone array. For detection and localization, damage-free plates serve as baselines compared against potentially damaged plates. For classification, a data-driven approach is employed using finite element simulations as training data. Results are presented for various damage types—including cuts, boundary failures, and delamination—in aluminum and fiber-composite plates. [Sponsored by NAVSEA and the NDSEG Fellowship.]
Nonlinear ultrasound to characterize dislocation-based damage in classical and rolling contact fatigue
Authors: Matlack Kathryn
Published: November 2021

Material damage in structural components is driven by nano- and micro-scale defects that evolve early in the component’s life. In metals, the interaction of an ultrasonic wave with these nano- and micro-structural defects, such as dislocations, precipitates, and micro-cracks, generates a second harmonic wave that is proportional to the acoustic nonlinearity parameter, which is an absolute and measurable material parameter. These defects are known to cause measurable changes in the nonlinearity parameter, which changes as the nano- and micro-structural defects evolve in the material. This talk will discuss how nonlinear ultrasound (NLU) techniques that measure the nonlinearity parameter can be used as a nondestructive evaluation tool to characterize dislocation-based damage in metals, and thus characterize early-stage damage. Our group’s recent work on using NLU to characterize different types of cyclic loading, classical fatigue and rolling contact fatigue, will be discussed. Specifically, ultrasonic measurements are related directly to materials characterizations on similar length scales to better understand the relationship between the nonlinearity parameter and the dislocation-based damage evolution.
Nonlinear resonant ultrasound spectroscopy (NRUS) for nondestructive evaluation
Authors: Shokouhi Parisa , Riviere Jacques
Published: November 2021

Nonlinear Resonant Ultrasound Spectroscopy (NRUS) is a simple yet effective technique for nondestructive evaluation of incipient damage in a wide range of materials. NRUS combines the advantages of resonance-based testing and nonlinear ultrasonic or acoustic testing in that it can be used for testing complex-shaped objects and detection of microscopic defects. In this talk, I describe several applications of NRUS in: (1) monitoring of microcracking in concrete materials due to various damage processes; (2) monitoring the growth of microscopic fatigue cracks in aluminum; and (3) predicting the fatigue life of additively manufactured metallic alloys. In addition, I provide a snapshot of our ongoing research in developing non-contact NRUS test set up and using NRUS for in-process monitoring of additively manufactured parts. I close with describing the limitations of NRUS and possible directions for future research to realize NRUS potential in nondestructive evaluation (NDE) applications.
Ultrasonic time reversal on defects in carbon fibre reinforced polymer using chirp-coded ultrasound in complex media
Authors: Lints Martin , Salupere Andrus , Dos Santos Serge
Published: November 2021

Various nonlinear methods have been investigated in recent years offering improvements of over conventional B-mode in medical imaging and non-destructive testing (NDT) [1]. The most common include harmonic and overtone generation, inter-modulation product generation and resonant frequency shift, also known as Nonlinear Elastic Wave Spectroscopy (NEWS) methods. Furthermore, new optimized excitations such as Nonlinear Time Reversal (TR) based methods are needed and, thanks to the analysis of symmetry properties of cross-correlation generated functions, a wide range of innovation are classified within TR-NEWS methods [2]. This work proposes to unite the frequency-modulated constant-wave scatterer localization with TR-NEWS principles to enable the localization of scatterers distant from the transducers and the analysis of their nonclassical nonlinearity which often can be caused by microdamage or cracking. In this paper, using the found frequency of the defect, the delayed TR–NEWS can be leveraged to periodically excite the damaged region with the focused ultrasound. Resonance excitation results show potential for enhancing the wave motion more than a simple focused waves [3]. Thanks to the complexity of the acoustical propagation in a complex medium, the physical interpretation of the cross-correlation function used during the TR-NEWS analysis can be easily understood in terms of the acoustic energy focused in space and in time.
Nondestructive evaluation of solid cargo inside cylindrical containers with linear and nonlinear resonance spectroscopy
Authors: Lin Kevin Y. , Mobley Joel , Prather Wayne , Gladden Joseph
Published: November 2021

Nondestructive evaluation (NDE) of cylindrical containers is of critical importance because of their ubiquity in industrial applications. However, there is a paucity of research on the NDE of solid cargo inside sealed enclosures with external sensors. This talk covers the application of linear and nonlinear resonance spectroscopy to the NDE of cargo inside cylindrical containers. The first study focused on a Transnuclear-32 (TN-32) cask used for the dry storage of spent nuclear fuel assemblies. The modes of the TN-32 were measured onsite and Finite Element Analysis was used to investigate modal changes due to loadings of fuel assemblies. Because of the difficulties introducing damage to fuel assemblies inside a TN-32, a 1:6 scaled cask containing 32 mock-up fuel assemblies was manufactured for laboratory studies. Using the linear approach, metrics were developed that could detect cargo damage down to the single assembly level. To resolve the signatures of damaged versus missing assemblies, nonlinear ultrasound resonance spectroscopy was utilized to investigate the contact nonlinearity between a smaller scale container and loose spheres which mimicked internal debris. Based on the resulting data, a phenomenological contact-loss model was developed which could estimate the total mass of the spheres regardless of the material and radius.
Airborne acoustic characterisation of cultural heritage paintings: A preliminary study
Authors: Takahashi Victor , Fortineau Jerome , Lemâtre Michaël , LETHIECQ Marc
Published: November 2021

In order to assess the health of cultural heritage paintings, for example prior to their restoration, visual inspections as well as techniques such as X-ray imaging are commonly used. Non-contact acoustic methods could become another exploration modality thanks to their non-destructive character and the fact that they are expected to be more sensitive to certain defects, such as a delamination, than other techniques. A setup has been designed for such applications, based on airborne ultrasonic transducers operating in the several hundred kHz to over 1 MHz range, specific transmit/receive electronics and automated scanning stages allowing 2D through-transmission scans to be performed on areas up to 80 × 80 square centimeters. Measurements on well-known thin plates made of plastic, wood and gesso on wood were first performed to evaluate the possibilities of the technique, then simple paintings on canvas were tested and finally a real ancient painting was scanned. A method where the transmission amplitude is plotted versus the angle between the propagation axis and the normal to the painting surface is developed for local characterization of the elastic constants of the sample under test, thanks to comparison with simulated Lamb wave dispersion curves using a fitting procedure. These promising results open the way towards comparison between acoustic, radiological and other imaging results on paintings with severe defects that require restoration.
Vibrometric ranging for air-coupled ultrasonic testing
Authors: Bühling Benjamin , Maack Stefan , Strangfeld Christoph
Published: November 2021

Ultrasonic testing is a well-established method to assess characteristics of a specimen non-destructively via the time of flight (ToF) of the acoustic signal. While traditional methods require dry or liquid coupling of transducer and specimen, air-coupled ultrasound (ACU) transducers allow contact-free measurements. The signal is passing through air before it interacts with the specimen and, finally, is received by a sensor. Knowledge of the acoustic travel time between transducer and specimen is imperative to calculate the correct ToF through the specimen. In this contribution, we propose the use of a laser Doppler vibrometer to obtain this delay time through air. Exploiting the opto-acoustic effect, an ACU signal is observable before and after reflection at the specimen surface. By auto-correlating the signal, the delay time through air can then be found non-invasively, calibration-free, resonance-free, and on-line. Furthermore, this method provides a reference signal for pulse compression approaches. The benefits of vibrometric ranging are demonstrated experimentally using a piezoelectric and a fluidic transducer.