Rigid Test Research Articles

A Modified Strain‐Wedge Model for Small Strain Rigid Piles in Sand

ABSTRACTThis paper develops a modified strain‐wedge (MSW) model that accounts for the resistance to bending moments caused by the lateral frictional resistance and axial forces of piles in the small‐strain regime in sands and algorithmizes a finite differential analysis program. Two cases of rigid pile tests, one in Blessington and another in Shenton Park were used to calibrate the finite element analysis model and verify the proposed modified model. The results show that the analysis of pile‐side resistance is pivotal for rigid horizontally loaded monopiles, and the MSW model is the most accurate at predicting lateral displacement and the moments. Its accuracy in a small‐strain regime to predict the pile rotation points and the maximum bending moment is almost three times that of other models. With the increase of the soil strain, the accuracy of the MSW decreases. On the contrary, the prediction accuracy of numerical analysis using the UBC3D‐PLM constitutive model increases.

Reflex regulation of model-based biomimetic control for a tendon-driven prosthetic hand

Remarkable compliance of human hands due to muscular biomechanics and neural reflexes, attributes lacking in conventional prosthetic hands. Our prior study replicated neuromuscular reflex in prosthetic control using neuromorphic modeling. Nonetheless, the specific impact of the spinal reflex feedback in biomimetic control on amputees’ manipulation capabilities remains unclear. This study aims to investigate the plausible role of reflex regulation in biomimetic control for tendon-driven prosthetic hands. Eleven subjects with forearm amputations participated in force control tasks and functional tasks. The force control tasks were performed using either the prosthetic forefinger or the entire hand. The functional tasks of varying difficulties included the standard rigid object test (SROT), refined rigid object test (RROT), and fragile object test (FOT). Additionally, the stiffness properties of biomimetic control were tested prior to the human-in-loop evaluations. Closed-loop control (CLC) with integrated proprioceptive feedback and open-loop control (OLC) were employed for assessments. Results showed that the reflex regulation contributed significantly to the increase by 20.4% in success rate, 17.9% in effective throughput, and 65.7% decrease in break rate during in the pressing force control task. CLC consistently outperformed OLC across all indices. Indeed, the gripping force control task revealed comparable trends as well. In functional tasks, the reflex regulation yielded 10.5%, 17.9%, and 146.4% improvements in performance for SROT, RROT and FOT, respectively. The findings highlight the essential role of reflex regulation in biomimetic prosthesis control, providing evidence for enhancing amputees’ fine manipulation abilities by replicating the human sensorimotor functions.

Non-Gaussian properties and their effects on extreme wind pressure of a 4:1 rectangular cylinder

This paper investigates the wind pressure characteristics of a 4:1 rectangular cylinder under 19 wind angles using a rigid model wind tunnel test, focusing on non-Gaussian properties and extreme wind pressure. The wind angle (α) varies from 0° to 90° and the Reynolds number (Re) ranges from 0.32 × 105 to 2.14 × 105. The spatial and statistical distributions of wind pressure, along with its non-Gaussian properties, are presented. Detailed analyses of these characteristics are provided. The peak factor of wind pressure was calculated using the modified Hermite method. The results indicate that the skewness and kurtosis of the windward region of the 4:1 rectangular cylinder remain relatively unchanged with varying wind angles. In contrast, the skewness and kurtosis in the separation and wake zones are significantly influenced by changes in the wind angle. Most wind pressures on the 4:1 rectangular cylinder exhibit negative bias and a softening process. The non-Gaussian properties are most prominent at the corner of the wake zone. The peak factor of 2.5 (used in Chinese code) or peak factor g,G based on Gaussian processes on the separation and wake zones of interest are much smaller than the peak factors g,NG calculated based on the modified Hermite method. Ignoring non-Gaussian properties underestimates extreme wind pressures by at least 20%–30%. Therefore, non-Gaussian properties must be considered when calculating wind pressure extremes for similar rectangular structures. Additionally, the peak factor value in the Chinese code should be increased appropriately to ensure structural safety.

A Study of the Relationship Between Objective Tests to Diagnose Erectile Dysfunction and Markers of Cardiovascular Disease.

Background: Erectile dysfunction (ED) can stem from various organic and functional causes but is often linked to vascular health and cardiovascular disease. Limited data exist on how cardiovascular disease markers correlate with objective ED tests like the Nocturnal Penile Tumescence and Rigidity (NPTR) test and Penile Color Doppler Ultrasound (PCDU). Methods: A prospective observational study was performed, and 58 men with ED were assessed using the International Index of Erectile Function-15 (IIEF-15), NPTR test, and PCDU. Peripheral vascular health was evaluated through carotid intima-media thickness (cIMT) and brachial flow-mediated dilation (FMD). Results: Out of the participants, 44 had normal NPTR results, while 14 had abnormal results. The group with abnormal NPTR results was significantly older and had higher rates of hypertension and diabetes. Although the IIEF-15 scores were similar between the two groups, those with abnormal NPTR results had a lower peak systolic velocity (PSV) and a higher prevalence of impaired PSV. Correlations between the IIEF, NPTR, PCDU, and peripheral vascular markers lost significance after the age adjustment. Conclusions: This study suggests that abnormal NPTR results, combined with cardiovascular risk factors, may signal vascular ED and generalized vasculopathy, highlighting the need for cardiovascular assessment. An accurate ED diagnosis should integrate clinical evaluation with multiple tests while considering aging as a key risk factor.

Experimental investigation on wind loads and wind-induced responses of large-span flexible photovoltaic support structure

Flexible photovoltaic (PV) support structure offers benefits such as low construction costs, large span length, high clearance, and high adaptability to complex terrains. However, due to the high flexibility and low damping of the cable system, wind load becomes the primary control factor for structural safety and the key consideration in the design. In this study, a 45 m span flexible PV support structure with 3 spans and 12 rows was designed. The wind loads on PV panels were obtained by wind tunnel tests on a rigid model and the wind-induced responses were investigated by wind tunnel tests on an aeroelastic model. The shielding effects and tilt angle of PV modules on the wind load and wind-induced vibration of the flexible PV support were studied. The experimental results show that in the rigid model wind tunnel test, the wind pressure on the surface of PV modules exhibits a gradient distribution along the direction of wind flow, with symmetric distribution along the mid span. With the increase in the tilt angle of the PV module, the shielding effect becomes significant and the most pronounced shielding effect on the mean wind pressure coefficient occurs in the second row of the windward zone. In aeroelastic model wind tunnel tests, the mean vertical displacement of the flexible PV support structure increases with the increase of wind speed and tilt angle of PV modules. Due to the wind-resistant anchor cables set in both the windward and leeward zones, the vibration amplitude near the edge rows is significantly smaller than that of the middle rows when the structure is subjected to wind suction. When the flexible PV support structure is subjected to wind pressure, the maximum mean vertical displacement occurs in the first rows at high wind speeds. The shielding effect has a noticeable impact on the wind-induced response of the leeward zone at α = 20° under wind pressure, resulting in the decrease of amplitude vibration by approximately 53 %. The wind vibration coefficients in different zones under the wind pressure or wind suction are mostly between 2.0 and 2.15. Compared with the experimental results, the current Chinese national standards are relatively conservative in the equivalent static wind loads of flexible PV support structure.

NONUNIVERSITY OF CONSTRAINT RELEASE RELAXATION IN ENTANGLED LINEAR POLYMERS OF VARIOUS CHEMICAL STRUCTURES

ABSTRACT Extensive experiments have established that constraint release (CR) relaxation takes place in binary blends of chemically identical long and short polymer chains wherein the long chains are dilute and entangled only with the short chains. Recently, Hannecart et al. (Polymers15, 1569 (2023)) focused on polymers of various chemical structures—polystyrene (PS), polyisoprene (PI), polybutadiene, and poly(methyl methacrylate) (PMMA)—and compared the CR relaxation time τL,CR[b] of the long chains in the binary blends of each polymer species. From this comparison, they concluded that a normalized lifetime of the entanglement obstacle, τobstacle/τe = {τL,CR[b]/ZL2}/τe, with ZL = ML/Me (entanglement number of the long chain) and τe being the Rouse relaxation time of the entanglement segment, is determined only by the entanglements number of the short chain, ZS = MS/Me, irrespective of the chemical structure of the chains. This universality (independence from chemistry) would be an important feature if it were unequivocally concluded from experimental data. However, the values of the molecular weights used in their comparison, ML, MS, and Me, should have unavoidably included experimental uncertainties, which disturbs rigid conclusion of the universality. Aiming at a rigid experimental test avoiding those uncertainties, this study focuses just on data of the linear viscoelastic moduli G* of entangled monodisperse polymers of various chemical structures, PS, PI, PMMA, and poly(t-butyl styrene) (PtBS). We were able to find several pairs of chemically different but viscoelastically equivalent monodisperse polymers exhibiting indistinguishable G*/GN data (with GN being the plateau modulus) from the local Rouse relaxation zone to the terminal relaxation zone. For binary blends of those equivalent polymers in each chemical species, that is, long-X/short-X blends with X = PS, PI, PMMA, or PtBS, our experiments revealed that the CR relaxation of the dilute long chain does not complete at the same reduced frequency ωτe even when the chemically different component chains were viscoelastically equivalent in their monodisperse bulk state. It turned out that the CR relaxation is slower in the order of PS (slowest) < PMMA < PI < PtBS (fastest) and that this difference was by a factor of 3–4 in total (well above the experimental resolution limit), rigidly showing the nonuniversal character of CR. An origin of this nonuniversality is briefly discussed within the framework of existing CR models, for example, Graessley’s CR model that already involved a chemistry-dependent parameter z representing a number of local CR hopping sites per entanglement segment.

Prediction of Backward Erosion, Pipe Formation and Induced Failure Using a Multi‐Physics SPH Computational Framework

ABSTRACTSeepage‐induced backward erosion is a complex and significant issue in geotechnical engineering that threatens the stability of infrastructure. Numerical prediction of the full development of backward erosion, pipe formation and induced failure remains challenging. For the first time, this study addresses this issue by modifying a recently developed five‐phase smoothed particle hydrodynamics (SPH) erosion framework. Full development of backward erosion was subsequently analysed in a rigid flume test and a field‐scale backward erosion‐induced levee failure test. The seepage and erosion analysis provided results consistent with experimental data, including pore water pressure evolution, pipe length and water flux at the exit, demonstrating the good performance of the proposed numerical approach. Key factors influencing backward erosion, such as anisotropic flow and critical hydraulic gradient, are also investigated through a parametric study conducted with the rigid flume test. The results provide a better understanding of the mechanism of backward erosion, pipe formation and the induced post‐failure process.

Study of bond strength and electronic properties at the 6H-SiC/Al interface: Based on first-principles calculations

As the medium between the reinforcement and the matrix, the interface plays a critical role in the mechanical properties of silicon carbide particle reinforced aluminum matrix composites. This study used first-principles calculation methods to systematically analyze 14 different 6H-SiC/Al low-index interfaces, including atomic configuration, interface bonding strength, and electronic structure and bonding principles between interfaces. The adhesion work calculations reveal that the C-top-SiC(0001)/Al (111) and SiC(0001)/Al (100) interfaces have larger adhesion work values, specifically 5.09 J/m2 and 5.021 J/m2, respectively. Additionally, the rigid tensile testing confirms that the tensile stress values at the interfaces of C-top-SiC(0001)/Al (111) and SiC(0001)/Al (100) are higher, measuring 36.4 GPa and 32.5 GPa, respectively. The above results show that the interface bonding strength of these two configurations is the highest, the most stable, and most likely to appear in the 6H-SiC/Al interface configuration. The results of the analysis on charge density difference and partial density of states indicate that the interfaces of C-top-SiC (0001)/Al (111) and SiC (0001)/Al (100) are primarily composed of strong ionic and covalent bonds.

Aerodynamic characteristics of the train under the stationary thunderstorm downburst wind

The aerodynamic characteristics of the train under the stationary thunderstorm downburst wind were studied. The thunderstorm downburst wind test device was employed to simulate the thunderstorm downburst wind field. Based on the rigid model pressure measurement tests, analyses were conducted on the influence of radial distance on the pressure coefficients on the train surface, the aerodynamic load coefficients of the train section, and the total force coefficients of the middle and head cars. On this basis, combined with the computational fluid dynamics model, further exploration was conducted on the characteristics of the mean pressure on the train surface and the flow field around the train at different radial distances under the stationary thunderstorm downburst wind. The research results show that the train's total aerodynamic coefficients fluctuate with the train's position. The non-uniform distribution of the lateral force coefficient for each train section is primarily caused by variations in the wind yaw angle along the train's longitudinal axis. Variations in the wind attack angle at different radial distances cause the total lateral force coefficient to change accordingly. When the radial distance r/Dj = 0.5, there is no significant vortex-shedding phenomenon in the flow field around the train. However, when radial distance r/Dj = 1 and 1.5, the leeward surface exhibits a regular vortex-shedding phenomenon. Vortex shedding starts at the junction of the leeward surface and the top surface, extending from the middle car along the train's longitudinal axis toward the front and rear.

Dynamic Response Analysis of Moving Trains Passing Through the Stationary Thunderstorm Downburst Wind

The safety of the high-speed train traveling through the stationary thunderstorm downburst wind was studied. First, a thunderstorm wind test device was used to simulate the stationary thunderstorm downburst wind. Based on the rigid model pressure measurement tests, the aerodynamic forces of the train traveling along different paths through the stationary thunderstorm downburst wind were measured. The influence of the radial distance of the crossing path on the aerodynamic force coefficients of the train was investigated. On this basis, an unsteady aerodynamic model of the high-speed train crossing through the stationary thunderstorm downburst wind was established, and dynamic response analysis was carried out using the SIMPACK multibody dynamics simulation software to explore further the safety of the high-speed train crossing through the stationary thunderstorm downburst wind. The research showed that the stationary thunderstorm downburst wind field has significant spatial variation characteristics compared with the atmospheric boundary layer wind field. When the train passes through the thunderstorm downburst wind, the radial wind speed and wind yaw angle experienced by the train constantly change, and the change curve shows a symmetrical distribution. The aerodynamic force of the train will undergo sudden loading and unloading processes, and the lateral force coefficient of the train on different paths shows a “pulse-type” variation. Moreover, the lateral force coefficient increases with the increase of wind yaw angle. Under the influence of the thunderstorm downburst wind, the variation trend of the aerodynamic force coefficients of the train is consistent with that under crosswind. However, there are significant differences in the numerical values. Therefore, it is impossible to simply use the formula for calculating the aerodynamic force coefficients of the train under crosswinds to predict the aerodynamic force coefficients of the train under the thunderstorm downburst wind. While passing through the thunderstorm downburst wind, the overturning coefficient index plays a decisive role in the safety of train operations. Train rollover is the main form of train safety accidents, while derailment accidents are not easy. The numerical results obtained in this study are significant for evaluating the operational safety while moving trains traversing the stationary thunderstorm downburst wind.

Motor improvement of remote programming in patients with Parkinson's disease after deep brain stimulation: a 1-year follow-up.

Remote programming (RP) is an emerging technology that enables the adjustment of implantable pulse generators (IPGs) via the Internet for people with Parkinson's disease (PwPD) who have undergone deep brain stimulation (DBS). Previous studies have not comprehensively explored the effectiveness of RP in managing motor symptoms, often omitting assessments such as the rigidity and retropulsion tests during the follow-up. This study evaluates the comprehensive improvements in motor performance and the potential cost benefits of RP for PwPD with DBS. A retrospective analysis was conducted on two groups of patients-those who received RP and those who received standard programming (SP). Clinical outcomes including motor improvement, quality of life, and daily levodopa dosage were compared between the groups during a 12 (± 3)-month in-clinic follow-up. A total of 44 patients were included in the study, with 18 in the RP group and 26 in the SP group. No significant differences were observed in the frequency of programming sessions or clinical outcomes between the groups (p > 0.05). However, the RP group experienced significantly lower costs per programming session than the SP group (p < 0.05), despite patients in the former group living further from our center (p < 0.05). Our findings suggest that RP could significantly reduce the costs of programming for PwPD with DBS, especially without compromising the effectiveness of treatment across all motor symptoms in the short term.

The neck structure design of vehicle crash finite element dummy model

Anthropomorphic Test Devices (ATDs) with high biofidelity and compatibility play a crucial role in vehicle safety. This study focuses on enhancing the neck of Hybrid III finite element model by optimising its design and material. The improved Hybrid III model (IH3) is validated through neck calibration tests. Comparing to experimental results,IH3 has a peak torque error of only 1.00% and 5.11%and a 60.04% improvement in calculation efficiency. Then MLH3 with low stiffness and equivalent muscles and ligaments is designed and tested. The results of MLH3 show higher biofidelity than l than Hybrid III. Finally, both IH3 and MLH3 have been tested in a 100% frontal rigid barrier test, with IH3 showing significant accuracy and computational efficiency, indicating that it could replace the current Hybrid III neck for simulation analysis. MLH3 has potential engineering application value in the future, as it improves upon the limitations of the Hybrid III neck’s biofidelity and more closely resembles the real human neck.

Computational Investigation of Vessel Injury Due to Catheter Tracking During Transcatheter Aortic Valve Replacement.

Catheter reaction forces during transcatheter valve replacement (TAVR) may result in injury to the vessel or plaque rupture, triggering distal embolization or thrombosis. In vitro test methods represent the arterial wall using synthetic proxies to determine catheter reaction forces during tracking, but whether they can account for reaction forces within the compliant aortic wall tissue in vivo is unknown. Moreover, the role of plaque inclusions is not well understood. Computational approaches have predicted the impact of TAVR positioning, migration, and leaflet distortion, but have not yet been applied to investigate aortic wall reaction forces and stresses during catheter tracking. In this study, we investigate the role that catheter design and aorta and plaque mechanical properties have on the risk of plaque rupture during TAVR catheter delivery. We report that, for trackability testing, a rigid test model provides a reasonable estimation of the peak reaction forces experienced during catheter tracking within compliant vessels. We investigated the risk of rupture of both the aortic tissue and calcified plaques. We report that there was no risk of diseased aortic tissue rupture based on an accepted aortic tissue stress threshold (4.2MPa). However, we report that both the aortic and plaque tissue exceed a rupture stress threshold (300kPa) with and without the presence of stiff and soft plaque inclusions. We also highlight the potential risks associated with shorter catheter tips during catheter tracking and demonstrate that increasing the contact surface will reduce peak contact pressures experienced in the tissue.

Micro-Satellite Systems Design, Integration, and Flight.

Within the past decade, the aerospace engineering industry has evolved beyond the constraints of using single, large, custom satellites. Due to the increased reliability and robustness of commercial, off-the-shelf printed circuit board components, missions have instead transitioned towards deploying swarms of smaller satellites. Such an approach significantly decreases the mission cost by reducing custom engineering and deployment expenses. Nanosatellites can be quickly developed with a more modular design at lower risk. The Alpha mission at the Cornell University Space Systems Studio is fabricated in this manner. However, for the purpose of development, the initial proof of concept included a two-satellite system. The manuscript will discuss system engineering approaches used to model and mature the design of the pilot satellite. The two systems that will be primarily focused on are the attitude control system of the carrier nanosatellite and the radio frequency communications on the excreted femto-satellites. Milestones achieved include ChipSat to ChipSat communication, ChipSat to ground station communication, packet creation, error correction, appending a preamble, and filtering the signal. Other achievements include controller traceability/verification and validation, software rigidity tests, hardware endurance testing, Kane damper, and inertial measurement unit tuning. These developments matured the technological readiness level (TRL) of systems in preparation for satellite deployment.

Method of generating speckle patterns for digital image correlation based on modified Conway's Game of Life.

The measurement accuracy of digital image correlation (DIC) is influenced by the quality of the speckle pattern. Although various models for generating random speckle patterns have been well discussed, obtaining appropriate speckle images with isotropic quality and performance could be a challenging issue in DIC. In this paper, we propose a novel (to our knowledge) method for generating speckle patterns based on modified Conway's game of life (GoL). By sequentially assembling the speckle patterns generated from the modified GoL, we produced the GoL speckle image. Then, verification and comparison experiments were conducted through pure in-plane translations. The results show that the generated speckle image which was resized with k s=6& k r=2 processing and subsequently fuzzified using a Gaussian filter, produces the best accuracy for DIC measurement. Furthermore, based on the rigid body in-plane rotation displacement tests in the physical experimental results of three different speckle images, the GoL speckle generated from our proposed method shows the smallest measurement error. This indicates that the proposed speckle patterns generating method could provide a new type of speckle pattern with better quality and accuracy.

Longitudinal CT-based finite element analyses provide objective fracture healing measures in an ovine tibia model.

Measuring the healing status of a bone fracture is important to determine the clinical care a patient receives. Implantable devices can directly and continuously assess the healing status of fracture fixation constructs, while subject-specific virtual biomechanical tests can noninvasively determine callus structural integrity at single time points. Despite their potential for objectification, both methods are not yet integrated into clinical practice with further evidence of their benefits required. This study correlated continuous data from an implantable sensor assessing healing status through implant load monitoring with computer tomography (CT) based longitudinal finite element (FE) simulations in a large animal model. Eight sheep were part of a previous preclinical study utilizing a tibial osteotomy model and equipped with such a sensor. Sensor signal was collected over several months, and CT scans were acquired at six interim time points. For each scan, two FE analyses were performed: a virtual torsional rigidity test of the bone and a model of the bone-implant construct with the sensor. The longitudinal simulation results were compared to the sensor data at corresponding time points and a cohort-specific empirical healing rule was employed. Healing status predicted by both in silico simulations correlated significantly with the sensor data at corresponding time points and correctly identified a delayed and a nonunion in the cohort. The methodology is readily translatable with the potential to be applied to further preclinical or clinical cohorts to find generalizable healing criteria. Virtual mechanical tests can objectively measure fracture healing progressing using longitudinal CT scans.

(141) Can a Nocturnal Penile Tumescence and Rigidity Test Detect Organic Aetiology of Erectile Dysfunction? A Peripheral and Penile Vascular Study

Abstract Introduction In the diagnostic workup of erectile dysfunction (ED) the Nocturnal Penile Tumescence and Rigidity test (NPTR) is being used less and less because of its inconvenience but also in part because of the intrinsic limits of this test. In particular, the NPTR has been considered very useful to diagnose psychogenic ED when it is positive (normal) but less informative when it is negative (pathological) because of the high incidence of false negatives. Other tests have been suggested to better diagnose an organic ED, especially the dynamic Penile Colour-Doppler Ultrasound (PCDU) to study the penile vascular response and detect a vasculogenic ED. Objective The purpose of the study was to explore the value of a pathological NPTR by investigating relationship between the NPTR result and the peripheral vascular health at the carotid, brachial and cavernous arteries. Methods We conducted an observational study involving patients with ED who had undergone a NPTR as part of their ED diagnostic workup. We assessed their peripheral vascular health through (1) the measurement of the intima-media thickness at the carotid arteries (cIMT), (2) the measurement of the flow-mediated dilation at the brachial artery (FMD), and (3) performing a PCDU. Results Globally, our patients presented with a normal cIMT, FMD and Peak Systolic Value (PSV) in the PCDU. The group with pathological NPTR were significantly older than patients with normal NPTR (55.6 vs 44.1 years, p=0.002), had a higher prevalence of hypertension (50.0 vs 6.8%, p=0.001), longer hypertension duration (8.0 vs 1.3 years, p=0.035), a higher prevalence of diabetes mellitus (42.9 vs 6.8%, p= 0.004), higher blood glucose (111 vs 92 mg/dl, p=0.004) and higher blood triglycerides levels (188 vs 96 mg/dl, p=0.002). Furthermore, they showed lower PSV (46.2 vs 71.0 cm/s, p=0.002) while we did not find significant differences as regards cIMT and FMD between the two groups. Interestingly, the prevalence of patients with pathological PSV (&amp;lt;35 cm/s) was higher among patients with a pathological NPTR but without reaching the statistical significance. However, when adopted an age-dependant cut-off described in the literature (PSV &amp;lt; age x 0.7 + 6.73) the difference between the two groups became significant (50.0 vs 11.4%, p=0.005). Finally, the correlation analysis showed a significant correlation between PSV and the cIMT (-0.352, ρ=0.009), the maximum number of events in the RPTR record (+0.344, ρ=0.012), and the mean tip tumescence (+0.303, ρ=0.036). When corrected for age, these associations lost their statistical significance. Conclusions This study demonstrates the diagnostic value of a pathological NPTR which suggests an organic aetiology of the ED and associates with pathological findings in the PCDU. Age appears to be one of the most important risk factors for ED, even when other risk factors are present. Finally, when using a PCDU to diagnose vasculogenic ED, a cut-off of 35 cm/s might be less sensitive than an age-dependent cut-off to detect early impairments of penile endothelial function. Disclosure No.

Association between testosterone levels and RigiScan parameters of patients with erectile dysfunction.

It is difficult to diagnose hypogonadism because of the lack of objective assessments of erectile dysfunction (ED), which is caused by hypogonadism. To provide a new approach for diagnosing hypogonadism, this study evaluated the efficacy of nocturnal penile tumescence and rigidity (NPTR) testing with RigiScan for patients with ED with and without hypogonadism. From June 2021 to February 2023, 133 patients with ED (62 with hypogonadism and 71 without) underwent NPTR testing at the Department of Andrology. A detailed history of all participants was obtained. All participants also underwent a physical examination, sex hormone testing, and ultrasound examination of the cavernous vessels of the penis. Patient characteristics, sex hormone serum levels, and RigiScan Plus data of NPTR testing of patients with ED were obtained and evaluated. Between the groups, there were no significant differences in age, body mass index, or erectile function score or in the prevalence of smoking, drinking, diabetes, hypertension, and hyperlipidemia. RigiScan data revealed differences in erection episodes per night, average event rigidity, erection durations, and percentage of tumescence greater than baseline, which were significantly lower in the testosterone-deficient group than in the normal testosterone group. The average event rigidity of the tip displayed the largest area under the curve value, with a sensitivity of 67.6%, a specificity of 85.5%, and a cutoff value of 52.50. Our findings may allow appropriate patients to receive testosterone replacement therapy, which has been shown to be an effective treatment for hypogonadism. This is the first study of its kind to perform a comprehensive review of the association between hypogonadism and RigiScan parameters. This study was limited by its small sample size. RigiScan parameters of patients with ED and testosterone deficiency were significantly lower than those of patients with normal testosterone; therefore, RigiScan is useful for the differential diagnosis of patients with ED caused by hypogonadism.

Damage characteristics and evaluation investigation of rigid projectiles penetrating steel-concrete-steel composite targets based on AHP-TOPSIS method

The steel-concrete-steel (SCS) structures are widely used in construction engineering with its excellent load-bearing capacity. To investigate the damage characteristics and anti-penetration performance of the SCS targets, rigid projectile penetration tests were conducted. In this study, the macroscopic measurement and 3D scanning imaging techniques were used to record SCS target damage parameters. Strain and accelerometer sensors were used to investigate the dynamic response parameters of the target. A comprehensive AHP-TOPSIS evaluation model was constructed based on the damage parameters to evaluate the effect of structural configuration on the anti-penetration capability of the SCS targets. The results indicated that the deformation of the steel plate, the dimensions of the impact crater and the dynamic response were proportional to the impact velocity of the projectile. Moreover, the most severe damage to the backside occurred when the projectile velocity was lower than the perforation velocity. The damage modes of the target at three typical impact velocities were also summarized based on the damage characteristics. Furthermore, the weights of each damage index and the closeness of different SCS targets to the evaluation indexes were obtained using the established AHP-TOPSIS evaluation model. Finally, it was determined that the SCS target in the structure form of F2R5 had the best anti-penetration performance. The results of this paper provide a reference for the design and performance evaluation of the SCS structures.

Aeroelastic instability mechanisms of single-axis solar trackers

Single-axis solar trackers are currently the most commonly used racking system in utility scale solar photovoltaic (PV) plants. The last decade has seen significant advances in the understanding of single-axis tracker aerodynamics after significant failures have occurred due to aerodynamic instabilities. The current study focuses on the aeroelastic mechanisms causing these divergent instabilities. The analytical background as a function of static tilt angle is presented for the different instabilities. The role of aerodynamic stiffness and aerodynamic damping are examined through rigid sectional model testing and these results are used to perform numerical stability estimates using multiple theoretical approaches. These results are compared with aeroelastic model testing of a single-axis solar tracker over a wide range of static tilt angles. These analytical, numerical, and experimental approaches are used to assess the static tilt angles governed by stiffness-driven and damping-driven aerodynamic instabilities. The small size and light weight of single-axis trackers makes them more susceptible to turbulent gusts. This aspect has been addressed in the current study through the concept of the structurally averaged wind speed and the effective gust velocity factor. Comparison to the experimental results suggests that stiffness-driven torsional instability can respond quite rapidly to the passage of turbulent gusts.