Effective Parameters Research Articles

Magnetically frequency-modulated piezoelectric energy harvester for ultra-low-frequency wave motion

In this paper, a magnetically frequency modulated piezoelectric energy harvester (MFPEH) for ultra-low-frequency wave motion is proposed. The MFPEH employs multiple sets of magnets coupled to achieve optimal electrical output at ultra-low-frequency excitation (<2 Hz). A straight rack and pinion drive converts the vertical motion of the float into rotational motion, and magnets on the rotor provide excitation to the piezoelectric cantilever. As a result, the MFPEH converts random wave motion into steady rotational motion. The MFPEH uses a rational combination of multiple sets of magnets and frequency modulation by magnetic coupling, which greatly improves the output performance. This paper describes the key factors affecting the output performance of MFPEH. An experimental system simulating a wave environment is designed and constructed. Under the most effective experimental parameters, the MFPEH achieves an optimal power of 32.76 mW. In a real wave environment, the MFPEH was able to illuminate 85 LEDs and power a thermohygrometer for normal operation. These results validate the potential of the MFPEH to power small electronic devices.

Experimental investigation of slit weir discharge

ABSTRACT A rectangular slit weir is used to measure small flows, namely, those flows less than 5 L/s and contraction ratios (b/B) less than 0.25. In the present study, flow tests were conducted in a laboratory setup with various contraction ratios (b/B) under models A (b/B = 1/12), B (b/B = 1/8), C (b/B = 1/6), D (b/B = 5/24), and E (b/B = 1/4). The dimensional analysis revealed that b/B, the height of the flow on the crest of the weir to the height of the weir crest (h/P), the Reynolds number (Re), and the Weber number (We) are effective parameters for predicting the discharge coefficient of the slit weir. The experimental results indicated that the discharge coefficient is variable for different contraction ratios; the maximum average discharge coefficient was achieved at the lowest b/B (Model A), with a value of 0.72. The minimum average discharge coefficient obtained in Model B equals 0.639. In addition, former prediction equations were compared with the obtained experimental data, and the minimum, average, and maximum errors were calculated. Furthermore, a relationship was established for deriving the discharge coefficient in slit weirs with R2 = 0.9212, RMSE = 0.02244, and MAE = 0.0134 based on the obtained experimental data with four effective parameters, b/B, h/P, Re, and We.

Bending and buckling responses of organic nanoplates considering the size effect

As humanity progresses, fossil fuel reserves are being increasingly exhausted, leading to increased focus on sustainable energy alternatives. Scientists are now researching solar panels that can efficiently convert solar energy into electricity for human use. This research employs a novel third-order shear deformation theory to investigate the static buckling and static bending behaviors of organic nanoplates, marking the first instance of such an approach being used. The formulas are computed using strain gradient theory to consider the impact of the size effect, where this size effect parameter is considered in both positive and negative cases. The plate's balancing equation is derived using the notion of virtual displacement, and the analytical solution is obtained using Navier's solution. The mathematical expression for deflection and critical buckling load in this study has been validated by comparing it with previously published analytical findings. This study also includes a set of numerical calculations to demonstrate the impact of certain geometric factors and the size effect on the static bending response and static buckling of organic plates. This study aims to assist designers in developing organic plate products that demonstrate optimal functionality in real-world applications

Active versus passive foam rolling on range of motion, tissue property, and neural adaptation in healthy young adults: A randomised controlled trial

IntroductionSelf-massage using a foam roller (foam rolling) is effective for increasing range of motion (ROM). However, the independent effects of pressure stimulation and voluntary movement during foam rolling remain unclear. This study investigated the effects of pressure stimulation and voluntary movement during the foam rolling intervention on ROM and its related parameters from the aspects of tissue mechanical properties and the central nervous system. MethodsThis study set a randomised open-label controlled parallel group design involving active foam rolling with pressure stimulation and voluntary movement (A-FR), passive foam rolling with only pressure stimulation (P-FR), and sham rolling with only voluntary movement (SHAM) of the calf muscle. Twenty-seven healthy active adults (males: 16, females: 11) were analysed. Parameters of tissue mechanical properties (as measured by tissue stiffness and thickness) and systemic nervous adaptation (as measured by PPT, stretch tolerance, HRV, and mood states), as well as maximal ankle active/passive dorsiflexion ROM, were measured. ResultsA-FR significantly improved pressure pain threshold, stretch tolerance, and negative mood and increased active and passive ROM. P-FR significantly improved parasympathetic nervous activity and negative mood and increased passive ROM. However, SHAM did not affect any ROM or parameters of tissue mechanical properties and systemic neural adaptation except for some negative mood improvement. ConclusionVoluntary movement does not independently affect ROM, whereas pressure simulation independently enhances ROM during the foam rolling intervention. Combining pressure stimulation and voluntary movement can enhance the ROM effect and influence parameters of tissue mechanical properties and the central nervous system.

Investigating orbital angular momentum modes in multimode interference (MMI) waveguides and revealing their mode conversion property

In this work, the propagation of OAM modes in multimode interference (MMI) waveguides, as the basic elements in many integrated optical devices, is studied to utilize their benefits in integrated OAM applications. OAM modes shape the OAM-maintaining image at the specific length of an MMI waveguide. As the most effective parameters on the properties of the generated image, waveguide’s width (W), topological charge (ℓ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\ell$$\\end{document}) and waist radius (WR) of the input OAM modes are investigated. Power overlap integral (POI) is used to evaluate the quality of images. The investigations show that the calculated POI is enhanced by increasing in WR of the input mode (from 86.91% for WR = 1.5 µm to 98.92% for WR = 3.5 µm; where W = 15 µm and ℓ=±1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\ell = \\pm 1$$\\end{document}). Furthermore, the increase in the waveguide’s width leads to decrease the quality of the self-imaged mode (from 98.90% for W = 15 µm to 85.15% for W = 50 µm; where WR = 3 µm and ℓ=±1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\ell = \\pm 1$$\\end{document}). It is also demonstrated that mode conversion between even order of OAM modes with opposite topological charges can occur at OAM-maintaining length of the MMI waveguides, which is the most outstanding achievement of this survey for optical communication systems.

Minimal model for reservoir computing

A minimal model for reservoir computing is studied. We demonstrate that a reservoir computer exists that emulates given coupled maps by constructing a modularised network. We describe a possible mechanism for collapses of the emulation in the reservoir computing by introducing a measure of finite scale deviation. Such transitory behaviour is caused by either (i) an escape from a finite-time stagnation near an unstable chaotic set, or (ii) a critical transition driven by the effective parameter drift. Our approach reveals the essential mechanism for reservoir computing and provides insights into the design of reservoir computer for practical applications.

Mediation Analysis with Multiple Exposures and Multiple Mediators.

A mediation analysis approach is proposed for multiple exposures, multiple mediators, and a continuous scalar outcome under the linear structural equation modeling framework. It assumes that there exist orthogonal components that demonstrate parallel mediation mechanisms on the outcome, and thus is named principal component mediation analysis (PCMA). Likelihood-based estimators are introduced for simultaneous estimation of the component projections and effect parameters. The asymptotic distribution of the estimators is derived for low-dimensional data. A bootstrap procedure is introduced for inference. Simulation studies illustrate the superior performance of the proposed approach. Applied to a proteomics-imaging dataset from the Alzheimer's disease neuroimaging initiative (ADNI), the proposed framework identifies protein deposition-brain atrophy-memory deficit mechanisms consistent with existing knowledge and suggests potential AD pathology by integrating data collected from different modalities.

Thermomechanical interaction in a living tissue due to variable thermal loading with memory

AbstractIn order to address various clinical applications within living tissue, the aim of this work is to analytically study the thermomechanical interaction for a living tissue which is subjected to variable thermal loadings. Human tissues undergoing regional hyperthermia treatment for cancer therapy is based on graded changes of the cells, and as a consequences, the constitutive equations have been formulated using the nonlocal elasticity theory. The heat transport equation for the present problem is formulated in the context of Moore‐Gibson‐Thompson theory of generalized thermoelasticity assimilating the memory‐dependent derivative within a slipping interval. Both the boundaries of the tissue is maintaining the condition of zero traction. The lower boundary of the tissue is subjected to prescribed thermal loading while, the upper boundary is kept at zero temperature. Utilizing the Laplace transform mechanism, the governing equations have been solved and the general solutions have been obtained in the transformed domain. In order to arrive at the solutions in the real space‐time domain, suitable inversion of the Laplace transform has been carried out numerically using the method of Zakian. Numerical findings suggest that thermomechanical waves propagate through skin tissue over finite distances, which helps mitigate the unrealistic predictions made by the Pennes' model. Significant effect due to different effective parameter such as nonlocal parameter and the time‐delay parameter is reported. Also, how a nonlinear kernel function can be more effective in bio‐heat transfer, is outlined in the study also.

A theoretical study on evaluating brain tumor changes in tumor treating fields therapy by impedance detection.

TTFields is a novel FDA-approved technology utilized for treating glioblastoma multiforme (GBM) within the brain. Presently, the effectiveness of therapy is evaluated through MRI imaging at random two-month intervals. Electrical impedance is an important and effective parameter for reflecting changes in tissue properties. In TTFields treatment for brain tumors, electrodes attached to the scalp deliver electric field energy to the tumor region. We hypothesize that these electrodes can also serve as sensors to detect impedance changes caused by tumor alterations in real time, thus continuously assessing the effectiveness of the treatment. In this work, we propose and scrutinize this hypothesis by conducting an in silico study to confirm the potential feasibility of the proposed concept. Our results indicate that the impedance amplitude change measured between opposing TTFields electrode arrays utilizing voltage and frequency of 50 V and 200 kHz (typical TTFields treatment parameters), has enough resolution (> 1mm) and Signal-to-Noise Ratio (> 40 dB) to evaluate tumor size change in the head. The impedance detection technique may be a significant augmentation to TTFields cancer treatment, enabling the continuous evaluation of safety and efficacy throughout the procedure.

New probe of non-Gaussianities with primordial black hole induced gravitational waves

We propose a new probe of primordial non-Gaussianities (NGs) through the observation of gravitational waves (GWs) induced by ultra-light (MPBH<109g) primordial black holes (PBHs). Interestingly enough, the existence of primordial NG can leave imprints on the clustering properties of PBHs and the spectral shape of induced GW signals. Focusing on a scale-dependent local-type NG, we identify a distinct double-peaked GW energy spectrum that, contingent upon MPBH and the abundance of PBHs at the time of formation, denoted as ΩPBH,f, may fall into the frequency bands of upcoming GW observatories, including LISA, ET, SKA, and BBO. Thus, such a signal can serve as a novel portal for probing primordial NGs. Intriguingly, combining BBN bounds on the GW amplitude, we find for the first time the joint limit on the product of the effective non-linearity parameter for the primordial tri-spectrum, denoted by τ¯NL, and the primordial curvature perturbation power spectrum PR(k), which reads as τ¯NLPR(k)<4×10−20ΩPBH,f−17/9(MPBH104g)−17/9.

Multiscale mushy layer model for Arctic marginal ice zone dynamics

Perhaps the most dynamic component of the Arctic sea ice cover is the marginal ice zone (MIZ), the transitional region between dense pack ice to the north and open ocean to the south. It widens by a factor of four while seasonally migrating more than 1600 km poleward in the Bering–Chukchi Sea sector, impacting climate dynamics, ecological processes, and human accessibility to the Arctic. Here we showcase a transformative mathematical modeling approach to understanding changes in MIZ location and width, focusing on their seasonal cycles as observed by satellites. We view the MIZ as a liquid-solid phase transition region, or mushy zone, on the scale of the Arctic Ocean. Invoking the physics of phase changes, the MIZ is modeled as a dynamic, multiscale composite material layer; this model captures 96% of the annual cycle of MIZ location and 78% of the annual cycle of MIZ width. Temperature in the upper ocean is described by a nonlinear heat equation with effective parameters obtained using homogenization theory for a random medium of ice floes in a sea water host. Observations and simulations together indicate that MIZ location closely tracks the below-ice 273 K isotherm while the width of the MIZ follows vertical heat flux convergence, but with a three-week lag.

Identifying Network Ties from Panel Data: Theory and an Application to Tax Competition

Abstract Social interactions determine many economic behaviors, but information on social ties does not exist in most publicly available and widely used datasets. We present results on the identification of social networks from observational panel data that contains no information on social ties between agents. In the context of a canonical social interactions model, we provide sufficient conditions under which the social interactions matrix, endogenous and exogenous social effect parameters are globally identified if networks are constant over time. We also provide an extension of the method for time-varying networks. We then describe how high-dimensional estimation techniques can be used to estimate the interactions model based on the Adaptive Elastic Net Generalized Method of Moments. We employ the method to study tax competition across US states. The identified social interactions matrix implies that tax competition differs markedly from the common assumption of competition between geographically neighboring states, providing further insights into the long-standing debate on the relative roles of factor mobility and yardstick competition in driving tax setting behavior across states. Most broadly, our identification and application show that the analysis of social interactions can be extended to economic realms where no network data exists.

Effect of Rarefactions and Convective Heat Change on Free Convective Unsteady MHD Flow in a Slip-Flow Regime Past a Vertical Wall with Convective Surface Boundary Condition

The study investigates the unsteady free convective two-dimensional MHD flow past a vertical porous plate with convective surface boundary condition in porous medium in slip flow regime under the action of variable suction velocity. Analytical solutions are obtained for the system using perturbation technique that converts non-linear coupled governing partial differential equations into non-dimensional form of ordinary differential equations. Effects of variable suction velocity, rarefactions parameter and heat change parameter are analysed and discussed graphically for various values of effective physical parameter such as Grasshof number, Magnetic field parameter, Prandtl number, Permeability parameter on fluid velocity and temperature, skin friction, and heat transfer.

Becoming Self Employed: Israeli Family Physicians' Push and Pull Factors.

As primary care is an important infrastructure for the entire health system, the employment structure choices of family physicians-whether to work in a managed care organization or be self-employed, can impact all effectiveness parameters of healthcare: quality, access, health equity, patients' experiences, and cost-effectiveness. The aim of this study is to assess the push and pull factors influencing family physicians' employment choices. This study employed a qualitative approach to explore the experiences of family physicians (FPs) who choose to work a self-employment practice. We conducted semi-structured interviews with twenty-seven self-employed FPs in Israel, selected through purposive and snowball sampling. The interviews were conducted via Zoom, recorded, and transcribed verbatim. Data analysis followed thematic analysis framework. The analysis yielded 10 themes, which were organized into two categories: pull and push factors. Pull factors, i.e., factors that attract family physicians to become self-employed, included professional self-fulfillment, higher income, professional and business autonomy, working with secretaries according to one's personal choice, designing the space of the clinic, and flexibility in working hours. Push factors, i.e., factors that demotivated family physicians to work under managed care and pushed them to choose self-employment included low control over the work environment, workload, decreased professional and organizational autonomy, managerial pressures on quality measures, engagement in marketing activities, and tensions with non-medical staff in the Health Maintenance Organization. There are obvious implications of this work for Health Maintenance Organizations' policy makers. Balancing managerial pressure and tensions between family physicians and non-medical administration and ensuring suitable working conditions increased physicians' control over the work environment, and professional autonomy may decrease push factors and retain family physicians as Health Maintenance Organization-employed. Understanding pull factors may help to develop a strategy for maximizing cooperation with self-employed family physicians and reinforce physicians' linkage to the healthcare system's treatment objectives.

Selective solid phase extraction of folic acid from tomato as a biological source with a magnetic molecularly imprinted polymer measured by fluorescence spectroscopy

AbstractA novel magnetic molecular-imprinted polymer (MMIP) was used to selectively extract folic acid directly from real samples. Folic acid was used as template molecule, Fe3O4/SiO2-3-triethoxysilyl-propyl-acrylamide as functional monomer, azobisisobutyronitrile as initiation, ethylene glycol dimethacrylate as crosslinker agent, and acrylamide as the secondary monomer in a mixed ethanol-water solvent. The effect of different parameters on the extraction efficiency was studied, and the optimum conditions were established as follows: the concentrations of crosslinking and template were fixed at 0.05 and 0.06 g, absorption percentage was 96.5, pH was adjusted to 8, and extraction time was 8 h with a temperature of 25 °C. By examining the effect of pH, we tried to investigate the effect of the amide groups that present in MMIP and its intermolecular hydrogen interaction with folic acid. After optimising the effective parameters in polymer synthesis and adsorption rate, a magnetic imprinting dispersive solid-phase extraction method combined with fluorescence spectrophotometry at λem = 367 nm (MMIP-DSPE-FL) was constructed for sensitive determination of folic acid in tomato samples. The limit of quantification (LOQ) and limit of detection (LOD) values were 30.00 ± 0.01 μg L−1 and 10.00 ± 0.03 μg L−1, respectively, after the MMIP-DSPE preconcentration. Three tomato samples were analysed to give recoveries in the range of 80.2–81.6%, with relative standard deviation values below 0.6% (n = 3). The prepared MMIP-DSPE showed high selectivity toward folic acid, which could be used six times without changing adsorption capacity. The adsorption isotherm of the folic acid-imprinted polymer pursued the Langmuir model (RL = 0.029), and the kinetics model followed pseudo-first-order (R2 = 0.9974).

Effects of Diethoxymethylsilane/Helium Flow Rate Ratio on Low-k Films Deposited by Plasma-Enhanced Chemical Vapor Deposition

As the semiconductor industry has continuously reduced the integrated circuit (IC) chip size, a resistance-capacitance (RC) delay emerged, causing deterioration of the chip performance. To reduce the RC delay, low dielectric constant (low-k) films with suitable mechanical strengths have been adopted as intermetal dielectrics (IMDs). In this study, low-k plasma-polymerized diethoxymethylsilane (ppDEMS) films were fabricated by plasma-enhanced chemical vapor deposition of the DEMS precursor with a flow rate ratio of the DEMS precursor to helium (He) carrier gas (DEMS/He FRR) as a key parameter. As the DEMS/He FRR increased, the refractive index was reduced from 1.401 to 1.386, and the k value decreased from 2.77 to 2.10. From high-resolution scans of C1s, O1s, and Si2p peaks of X-ray photoelectron spectroscopy, the carbon contents increased, and the oxygen contents decreased, along with a decrease in the film density. With the increased DEMS/He FRR, hardness decreased from 2.5 to 1.8 GPa, and elastic modulus decreased from 17.08 to 11.50 GPa. Leakage current densities for all the ppDEMS films were less than 10−7 A cm−2 at 1 MV cm−1. The ppDEMS films could be suggested as the IMDs according to their electrical and mechanical performance.

The cost-effectiveness of preventing, diagnosing, and treating postpartum haemorrhage: A systematic review of economic evaluations.

Postpartum haemorrhage (PPH) is an obstetric emergency. While PPH-related deaths are relatively rare in high-resource settings, PPH continues to be the leading cause of maternal mortality in limited-resource settings. We undertook a systematic review to identify, assess, and synthesise cost-effectiveness evidence on postpartum interventions to prevent, diagnose, or treat PPH. This systematic review was prospectively registered on PROSPERO (CRD42023438424). We searched Medline, Embase, NHS Economic Evaluation Database (NHS EED), EconLit, CINAHL, Emcare, Web of Science, and Global Index Medicus between 22 June 2023 and 11 July 2024 with no date or language limitations. Full economic evaluations of any postpartum intervention for prevention, detection, or management of PPH were eligible. Study screening, data extraction, and quality assessments (using the CHEC-E tool) were undertaken independently by at least 2 reviewers. We developed narrative syntheses of available evidence for each intervention. From 3,993 citations, 56 studies were included: 33 studies of preventative interventions, 1 study assessed a diagnostic method, 17 studies of treatment interventions, 1 study comparing prevention and treatment, and 4 studies assessed care bundles. Twenty-four studies were conducted in high-income countries, 22 in upper or lower middle-income countries, 3 in low-income countries, and 7 studies involved countries of multiple income levels. Study settings, methods, and findings varied considerably. Interventions with the most consistent findings were the use of tranexamic acid for PPH treatment and using care bundles. In both cases, multiple studies predicted these interventions would either result in better health outcomes and cost savings, or better health outcomes at acceptable costs. Limitations for this review include that no ideal setting was chosen, and therefore, a transferability assessment was not undertaken. In addition, some sources of study uncertainty, such as effectiveness parameters, were interrogated to a greater degree than other sources of uncertainty. In this systematic review, we extracted, critically appraised, and summarised the cost-effectiveness evidence from 56 studies across 16 different interventions for the prevention, diagnosis, and treatment of PPH. Both the use of tranexamic acid as part of PPH treatment, and the use of comprehensive PPH bundles for prevention, diagnosis, and treatment have supportive cost-effectiveness evidence across a range of settings. More studies utilizing best practice principles are required to make stronger conclusions on which interventions provide the best value. Several high-priority interventions recommended by World Health Organization (WHO) such as administering additional uterotonics, non-pneumatic anti-shock garment, or uterine balloon tamponade (UBT) for PPH management require robust economic evaluations across high-, middle-, and low-resource settings.

Development of a UPLC-MS/MS Method to Simultaneously Measure 13 Antiepileptic Drugs with Deuterated Internal Standards.

The goal of this study was to develop and validate a UPLC-MS/MS method for simultaneous mea-surement of 13 AEDs, including carbamazepine, oxcarbazepine, lamotrigine, levetiracetam, topiramate, primidone, zonisamide, gabapentin, lacosamide, perampanel, pregabalin, rufinamide, and vigabatrin, in whole blood samples. A UPLC-MS/MS method for simultaneous determination of 13 AEDs in whole blood was developed, and validation was conducted for accuracy, precision, limit of quantification (LOQ), matrix effect, and stability. Our method was compared to two different hospitals using UPLC-MS/MS. All AEDs exhibited linearity across the AMR (analytical measurement range), with R2 values ranging from 0.994 to 1.000. The imprecision and inaccuracy for low and high quality control (QC) levels were within an acceptable range, with the coefficient of variation (CV) < 15%. The LOQ was 0.62 µg/mL for carbamazepine, 1.61 µg/mL for oxcarbazepine, 1.30 µg/mL for lamotrigine, 13.20 µg/mL for levetiracetam, 1.26 µg/mL for topira-mate, 1.01 µg/mL for primidone, 1.59 µg/mL for zonisamide, 1.09 µg/mL for lacosamide, 1.61 µg/mL for gabapentin, 0.50 µg/mL for pregabalin, 0.07 ng/mL for perampanel, 3.00 µg/mL for rufinamide, and 2.06 µg/mL for vigabatrin. All AEDs demonstrated acceptable assay parameters for carryover, stability, and matrix effects. Moreover, the assay showed satisfactory results compared to two different hospitals with a bias of less than 15%. We successfully developed and validated a fast and robust UPLC-MS/MS method for routine therapeutic drug monitoring of thirteen antiepileptic drugs simultaneously.

Small grazing angle reflection and the sound siphon effect over a low velocity layer of sediments.

The low-order normal modes with small grazing angles (SGA) often control long-range sound field characteristics in shallow water. The SGA reflection loss from a half-space low-velocity bottom (LVB) is independent of the sound attenuation, except around the angle of complete transmission; the SGA bottom reflection loss (BRL) from a seafloor with a top low-velocity layer is very insensitive to the LVB attenuation also, except around a few selected frequencies. Thus, the "seafloor velocity-attenuation coupling" problem will be more fatal for LVB geo-acoustic inversions. The dispersion equation of the normal modes in the LVB layer is coincidentally the same as the singularity expression of the SGA reflection coefficient in the water column, resulting in a sound siphon effect that causes the abnormally high SGA BRL and transmission loss in the water at the siphon frequencies. The siphon effect is very sensitive to seafloor acoustic parameters, might offer a physical base for geo-acoustic inversion, and show a dim light in a "gray area" for inverting the LVB sound attenuation at low to mid frequencies. As an example, the acoustic siphon effect and related seafloor geophysical parameters forming it in the Yellow Sea are reported in this paper.

A numerical simulation method for ultrasonic transmission in cancellous bone based on a four-parameter random growth method

Abstract Quantitative ultrasound (QUS) has been widely used in non-destructive evaluation of bone health in research and clinical practice. To make a more accurate bone evaluation, the transmission characteristics of ultrasound in the bone need to be understood in detail. In the two-dimensional finite element model, cancellous bone is usually simulated by a non-porous structure solid or by approximating bone trabeculae as ellipses, which is different from real bone. However, although the error of the model constructed by bone CT images is small, it needs to be based on real bone samples, and the samples are limited. Therefore, a modeling method of cancellous bone based on four-parameter random growth method was proposed in this paper, and on this basis, numerical simulation of ultrasonic transmission was carried out. Firstly, based on the four-parameter random growth method, the aggregation algorithm is used to concentrate discrete pixels and smooth the edge of pores. Meanwhile, the built-in algorithm ensures the same porosity before and after processing to reduce the discrete pore structure. Secondly, based on COMSOL to establish the simulation model of ultrasonic propagation in cancellous bone, we analyzed the change of acoustic field distribution, discussed the correlation between the porosity of cancellous bone and backscattering coefficient (BSC) based on the ultrasonic backscattering method, and compared the experimental results of CT scan images of bone samples. The experimental results show that the cancellous bone modeling method in this paper has the same conclusion as the method based on CT images, which verifies the feasibility of this method. This method can generate a geometric model of the cancellous bone microstructure with specified porosity and different bone trabecular distribution, which is similar to the real bone structure, and can be directly imported into the finite element software to facilitate the study of bone microstructure related problems. It provides a more convenient method to study the mechanism of ultrasonic propagation in cancellous bone and has important significance in solving the inverse problem of recovering effective bone parameters from the received ultrasonic signals.