Cross-sectional Area Research Articles

Numerical studies on the performance of Savonius turbines for hydropower application by varying the frontal cross-sectional area

The Savonius turbine is a drag-based device that utilizes hydrokinetic energy in irrigation channels for small-scale hydropower generation. Since it is a drag-type device, the turbine blade frontal cross-sectional area influences the performance of the turbine blade. In this paper, the influence of taper on the turbine blade bottom, top, and middle sides on the Savonius turbine performance was computed numerically using the sliding mesh technique with a 0.5 m/s water inlet velocity. In this study, the effect of various blades with varying cross-sectional areas has been analyzed numerically using the sliding mesh technique, and the results were compared with the semicircular blade profile. The variation of torque coefficient with respect to rotor blade rotation was plotted, and pressure and velocity variation were analyzed to investigate the performance parameters. The results showed that the top small, middle high, and bottom small blade profiles performed better than the semicircular, inverted taper and top high, middle small, and bottom high blade profiles. It is observed that the maximum torque coefficient at a TSR of 0.7 is 0.35, and the maximum power coefficient at a TSR of 0.9 is 0.253.

Sleep Characteristics, Magnetic Resonance Imaging- and Dual-Energy X-Ray Absorptiometry-Based Morphological Parameters, Muscle Strength, and Risk of Falls in Sedentary Older Subjects.

The aims of this cross-sectional study were to (a)assess actigraphy-based sleep parameters (total sample and gender differences), (b)assess differences in morphological parameters and physical function between short- versus normal-sleepers and poor- versus good-sleepers, and (c)assess the possible correlations between sleep variables and morphological and physical function parameters in older subjects. This study enrolled 42 healthy older participants (60-80years). Participants completed the following clinical evaluations: (1)whole-body dual-energy X-ray absorptiometry to assess the appendicular skeletal muscle mass index; (2)magnetic resonance imaging acquisition to determine the cross-sectional muscle area of thigh muscles and intermuscular adipose tissue; (3)risk of fall assessment through the mini-Balance Evaluation Systems Test; (4)strength assessment: (a)chair stand test and (b)handgrip strength test; (5)sleep monitoring by actigraphy to assess total sleep time, sleep efficiency, wake after sleep onset, sleep latency, fragmentation index, mobile time, and subjective sleep quality. 31.0% of subjects were short-sleepers (total sleep time < 6hr), 19.1% were poor-sleepers (sleep efficiency < 85%), and gender differences were detected in mobile time (males: 15.8 ± 6.0 and females: 13.4 ± 6.8; p < .001) and fragmentation index (males: 35.3 ± 14.3 and females: 29.6 ± 14.6; p < .001); no significant differences were observed between groups (short- vs. normal-sleepers and poor- vs. good-sleepers) in morphological and physical function variables; correlation analysis showed that sleep latency negatively correlated with Mini-Balance Evaluation Systems Test (r = -.352; p = .022) and a positive correlation was detected between cross-sectional muscle area and mobile time (r = .349, p = .023). No differences were observed in morphological and function parameters between good- versus poor-sleepers, those subjects with worse sleep onset latency (i.e.,longer time to fall asleep) registered higher for risk of fall. The potential role of sleep in the physiological mechanisms of muscular aging must be explored through cross-sectional cohort studies with a larger population.

Relationship between Lumbar Foraminal Stenosis and Multifidus Muscle Atrophy - A Retrospective Cross-Sectional Study.

Retrospective cross-sectional study. To evaluate the relationship between lumbar foraminal stenosis (LFS) and multifidus muscle atrophy. The multifidus muscle is an important stabilizer of the lumbar spine. In LFS, the compression of the segmental nerve can give rise to radicular symptoms and back pain. LFS can impede function and induce atrophy of the segmentally innervated multifidus muscle. Patients with degenerative lumbar spinal conditions who underwent posterior spinal fusion for degenerative lumbar disease from December 2014 to February 2024 were analyzed. Multifidus fatty infiltration (FI) and functional cross-sectional area (fCSA) were determined at the L4 upper endplate axial level on T2- weighted MRI scans using dedicated software. Severity of LFS was assessed at all lumbar levels and sides using the Lee classification (Grade: 0 - 3). For each level, Pfirrmann and Weishaupt gradings were used to assess intervertebral disc disease (IVDD) and facet joint osteoarthritis (FJOA), respectively. Multivariable linear mixed models were run for the LFS grade of each level and side separately as the independent predictor of multifidus FI and fCSA. Each analysis was adjusted for age, sex, BMI, as well as FJOA and IVDD of the level corresponding to the LFS. A total of 216 patients (50.5% female) with a median age of 61.6 years (IQR=52.0 - 69.0) and a median BMI of 28.1kg/m2 (IQR=24.8 - 33.0) were included. Linear mixed model analysis revealed that higher multifidus FI (Estimate [Confidence interval]=1.7% [0.1 - 3.3], P=0.043) and lower fCSA (-18.6mm2 [-34.3 - -2.6], P=0.022) were both significantly predicted by L2-L3 level LFS severity. The observed positive correlation between upper segment LFS and multifidus muscle atrophy points towards compromised innervation. This necessitates further research to establish the causal relationship and guide prevention efforts.

Diagnostic accuracy and confounders of vagus nerve ultrasound in amyotrophic lateral sclerosis-a single-center case series and pooled individual patient data meta-analysis.

Several single-center studies proposed utility of vagus nerve (VN) ultrasound for detecting disease severity, autonomic dysfunction, and bulbar phenotype in amyotrophic lateral sclerosis (ALS). However, the resulting body of literature shows opposing results, leaving considerable uncertainty on the clinical benefits of VN ultrasound in ALS. Relevant studies were identified up to 04/2024 and individual patient data (IPD) obtained from the respective authors were pooled with a so far unpublished cohort (from Munich). An IPD meta-analysis of 109 patients with probable or definite ALS (El Escorial criteria) and available VN cross-sectional area (CSA) was performed, with age, sex, ALS Functional Rating Scale-revised (ALSFRS-R), disease duration, and bulbar phenotype as independent variables. Mean age was 65years (± 12) and 47% of patients (± 12) had bulbar ALS. Mean ALSFRS-R was 38 (± 7), and mean duration was 18months (± 18). VN atrophy was highly prevalent [left: 67% (± 5), mean CSA 1.6mm2 (± 0.6); right: 78% (± 21), mean CSA 1.8 mm2 (± 0.7)]. VN CSA correlated with disease duration (mean slope: left -0.01; right -0.01), but not with ALSFRS-R (mean slope: left 0.004; mean slope: right -0.002). Test accuracy for phenotyping bulbar vs. non-bulbar ALS was poor (summary receiver operating characteristic area under the curve: left 0.496; right 0.572). VN atrophy in ALS is highly prevalent and correlates with disease duration, but not with ALSFRS-R. VN CSA is insufficient to differentiate bulbar from non-bulbar ALS phenotypes. Further studies are warranted to analyze the link between VN atrophy, autonomic impairment, and survival in ALS.

Modeling non-spherical hailstones

Abstract Hail research and forecasting models necessarily involve explicit or implicit – and uncertain – physical assumptions regarding hailstones’ shape, tumbling behavior, fallspeed, and thermal energy transfer. Whereas most models assume spherical hailstones, we relax this assumption by using hailstone shape data from field observations to establish empirical size-shape relationships with reasonable degrees of randomness considering hailstones’ natural shape variability, capturing the observed distribution of tri-axial ellipsoidal shapes. We also incorporate explicit, random tumbling of individual hailstones during their growth to simulate their free-falling behavior and the resultant changes in cross-sectional area (which affects growth by hydrometeor collection.) These physical attributes are incorporated in calculating hailstones’ fallspeeds, using either empirical or analytical relationships based on each hailstone’s Best and Reynolds numbers. Options for drag coefficient modification are added to emulate hailstones’ rough surfaces (lobes), which then modifies their thermal energy and vapor exchange with the environment. We investigate how applying these physical assumptions about nonspherical hail into the Penn State hail growth trajectory model, coupled with Cloud Model 1 supercell simulations, impacts hail production, and examine the reasons behind the resulting variability in hail statistics. The choice of hailstone size-mass relation and fallspeed scheme have the strongest influence on hail sizes. Using non-spherical, tumbling hailstones reduces the number of large hailstones produced. Applying shape-specific thermal energy transfer coefficients subtly increases sizes; the effects of lobes vary depending on the fallspeed scheme used. These physical assumptions, although adding complexity to modeling, can be parameterized efficiently and potentially used in microphysics schemes.

Experiments and design of laminated bamboo and concrete-filled steel tube columns under axial compression

To reduce the large amount of carbon emissions generated during concrete production and increase the application of green and sustainable building materials in the engineering field, laminated bamboo is used to replace the core section of concrete-filled steel tubes. The effects of cross-sectional forms and core section types on the failure modes and axial compressive properties of column structures are evaluated. The axial compressive behaviors of 16 bamboo columns, bamboo-steel tube (BST) columns, and concrete-filled steel tube (CFST) columns were compared from the perspectives of strength-to-weight ratio, stiffness, and absorbed energy. The experimental results show that the failure modes of laminated bamboo and concrete-filled steel tube (BCFST) columns are end buckling failure and diagonal shear failure. The axial compressive strength of the BST column increased by 94.49 % due to the restraining effect of the steel tube on the bamboo. The key finding is that the cross-sectional area of the core bamboo is a critical factor affecting the axial compressive strength. The BCFST columns with circular cross-sections show excellent ductility, with higher ductility factors of 111.50 % and 30.24 % than BST and CFST columns, respectively. In addition, laminated bamboo is found to be an excellent energy-absorbing material compared to other materials. Based on the confinement effect of BST columns, a prediction model for the axial compressive strength of BCFST columns is proposed, by which the predicted value shows a good agreement (overall error is less than 10 %) with the experimental results.

Investigation of the Relationship Between Disc Degeneration and Cross-Sectional Area of Deep Extensor Muscles in Patients with Chronic Non-specific Neck Pain

Investigation of the Relationship Between Disc Degeneration and Cross-Sectional Area of Deep Extensor Muscles in Patients with Chronic Non-specific Neck Pain

Cold-formed Q1200 ultra-high strength steel angle- and channel-section stub columns

This paper presents the experimental and numerical analysis of cold-formed Q1200 ultra-high-strength steel (UHSS) angle- and channel-section stub columns to elucidate their resistance performance. Initially, the mechanical property test including the flat and corner coupon specimens was conducted to quantify the effect of the cold-forming process on Q1200 UHSS. Then, the stub column test was conducted on 16 cold-formed Q1200 UHSS angle- and channel-section stub columns. Based on the experimental results, a finite element model was established to simulate the resistance performance of the cold-formed Q1200 UHSS angle- and channel-section stub columns. Subsequently, a parametric study involving 133 numerical models was performed. Then, the suitability of the design approaches in EN 1993-1-12, AISI S100, AS/NZS 4600, and the direct strength method (DSM) was evaluated. For angle-section stub columns, the design approach outlined in EN 1993-1-12 was deemed suitable and the effective cross-sectional area design approach and DSM in AISI S100 were found to be safe. However, these approaches were excessively conservative for slender cross-sections in directly predicting the ultimate resistance of angle sections. Because of unsafe predictions, the design approaches in EN 1993-1-12, AISI S100, and DSM were deemed inappropriate for channel-section stub columns. The modification suggestions were proposed for the current design approaches, where the beneficial effects from the strain hardening were included. Based on the comparisons, the revised design approaches in EN 1993-1-12, AISI S100, and DSM could be used to accurately predict the ultimate resistance of the cold-formed Q1200 UHSS angle- and channel-section stub columns.

Infrapatellar fat pad size and subcutaneous fat in knee osteoarthritis radiographic progression: data from the osteoarthritis initiative

ObjectivesAdipose tissue has been associated with knee osteoarthritis (KOA) pathogenesis, but the longitudinal changes in adipose tissue with KOA progression have not been carefully evaluated. This study aimed to determine if longitudinal changes of systemic and local adipose tissue is associated with radiographic progression of KOA.MethodsThis case-control study used data from the Osteoarthritis Initiative (OAI) and included 315 cases (all the right knees with a minimum of Kellgren-Lawrence score (KL) of 0 and an increase of ≥ 1 KL from baseline to 48 months) and 315 controls matched by age, sex, race, and baseline KL. Cross sectional area of IPFP (IPFP CSA) and subcutaneous adipose tissue around the distal thigh (SCATthigh) were measured using MRI images at baseline and 24 months. Conditional logistic regression models were fitted to estimate associations of obesity markers, IPFP CSA, and SCATthigh with radiographic KOA progression. Mediation analysis was used to assess whether IPFP CSA or SCATthigh mediates the relationships between baseline BMI and radiographic KOA progression.Results24-month changes of IPFP CSA (ΔIPFP CSA) and SCATthigh (ΔSCATthigh) were significantly greater in cases compared to controls, whereas Δ BMI and Δ abdominal circumference were similar in both groups during follow-up. Adjusted ORs for radiographic KOA progression were 9.299, 95% CI (5.357–16.141) per 1 SD increase of Δ IPFP CSA and 1.646, 95% CI (1.288–2.103) per 1 SD increase of Δ SCATthigh. ΔIPFP CSA mediated the association between baseline BMI and radiographic KOA progression (87%).ConclusionsSubjects with radiographic progression of KOA, had significant increases in IPFP CSA and subcutaneous adipose tissue while BMI and abdominal circumference remained stable. Additional studies are needed to confirm these associations.

Muscle structure predictors of vertical jump performance in elite male volleyball players: a cross-sectional study based on ultrasonography

ObjectiveThe objective of this investigation is to examine the contribution of key muscle groups in the lower limbs to vertical jumping performance in elite male volleyball players. Specifically, the study focuses on the rectus femoris (RF), vastus lateralis (VL), and lateral gastrocnemius (LG), as well as exploring differences between attack jump and other vertical jump types.MethodsTo achieve this, we employed B-mode ultrasound to evaluate the anatomical cross-sectional area (ACSA), muscle thickness (MT), pennation angle (PA), and fascicle length (FL) of the RF, VL, and LG in the participants. Fifteen elite male volleyball players were recruited as participants for this study. Jump heights were measured for four types of vertical jumps: attack jump (AJ), countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ). We conducted regression analyses to assess whether the previously mentioned muscle structures could predict jump performance.ResultsOur findings reveal that the muscle structure of the RF does not exhibit any significant correlation with the height of any jump. However, VL-ACSA displays a significant and the most potent predictive effect on jump height for all four jump types (AJ: R2 = 0.32, p = 0.001; CMJ: R2 = 0.37, p = 0.005; SJ: R2 = 0.52, p = 0.001; DJ: R2 = 0.25, p = 0.021). Conversely, LG-FL only demonstrates a significant and stronger predictive effect on AJ jump height (R2 = 0.18, p = 0.009). Combining VL-ACSA, LG-FL, and training age through multiple linear regression analysis resulted in a highly significant model for predicting AJ jump height (F = 13.86, R2 = 0.73). Moreover, the model incorporating VL-ACSA and training age is also important for predicting CMJ, SJ, and DJ jump heights (F = 8.41, R2 = 0.51; F = 13.14, R2 = 0.63; F = 5.95, R2 = 0.41; respectively).ConclusionThe muscle structure indicators in the lower limbs significantly predict jump performance among elite male volleyball players. However, different jump types are influenced by distinct indicators, particularly in the case of AJ, which is associated with LG-FL. This suggests that enhancing LG-FL may positively impact AJ ability, thereby emphasizing the importance of specificity in training. To optimize specialized jump performance in volleyball players, practitioners are advised to assess VL-ACSA and LG-FL and incorporate step-up and eccentric strength training targeting the calf muscles to yield considerable benefits.

Computer Simulation of Catheter Cryoablation for Pulmonary Vein Isolation

Cryoablation is a well-established medical procedure for surgically treating atrial fibrillation. Cryothermal catheter therapy induces cellular necrosis by freezing the insides of pulmonary veins, with the goal of disrupting abnormal electrical heart signals. Nevertheless, tissue damage induced by cold temperatures may also lead to other complications after cardiac surgery. In this sense, the simulation of catheter ablation can provide safer environments for training and the performance of cryotherapy interventions. Therefore, in this paper, we propose a novel approach to help better understand how temperature rates can affect this procedure by using computer tools to develop a simulation framework to predict lesion size and determine optimal temperature conditions for reducing the risk of major complications. The results showed that a temperature profile of around −40 °C caused less penetration, reduced necrotic damage, and smaller lesion size in the tissue. Instead, cryotherapy close to −60 °C achieved a greater depth of temperature flow inside the tissue and a larger cross-section area of the lesion. With further development and validation, the framework could represent a cost-effective strategy for providing personalized modeling, better planning of cryocatheter-based treatment, and preventing surgical complications.

Vagus nerve size determined via ultrasonography is associated with white matter lesions in patients with vascular risk factors.

The cross-sectional area (CSA) of the cervical vagus nerve (VN), as assessed through ultrasonography, might be linked to autonomic nervous system dysfunction. Hypertension is the primary factor associated with cerebral white matter lesions (WMLs), but there is also evidence of a connection with autonomic nervous system dysfunction. However, the associations between WMLs and VN size are unclear. Our objective was to investigate the associations between WMLs and VN size in patients with vascular risk factors. The CSA of the VN was evaluated using carotid ultrasonography in patients with a history of stroke (acute or chronic) and comorbidities (n = 196, 70.2 ± 12.7years). Common carotid artery (CCA) intima-media thickness and interadventitial diameter (IAD) were also measured. The severity of the WMLs was assessed by the Fazekas classification and Scheltens' scale. The CSA of the right VN (2.08 ± 0.65mm2) was significantly greater than that of the CSA of the left VN (1.56 ± 0.44mm2) (P < 0.001). Multiple linear regression analyses revealed that older age, hypertension, increased right CCA IAD, and decreased CSA of the right VN (standardized partial regression coefficient [β] -0.226; P < 0.001) were independently associated with the severity of WMLs (Scheltens' scale). A decreased CSA of the left VN was also associated with the severity of WMLs (β = -0.239; P < 0.001). VN size determined via ultrasonography was associated with the severity of WMLs. While these findings do not establish a causal relationship, they suggest that autonomic nervous system dysfunction is involved in the progression of WMLs.

Research on the influence of major ions in weakly alkaline mine water on anchor cable corrosion and protection technique

Anchor cables in water-rich roadways frequently experience severe corrosion and resultant fractures due to the combined effects of mine water and high stress. However, the precise factors influencing corrosion on these cables remain ambiguous, presenting challenges to roadway support safety. This study investigated the impact of major ions present in weakly alkaline mine water on anchor cable corrosion using salt spray corrosion experiments. The results indicated that major anions such as Cl- notably influence anchor cable corrosion, which primarily manifested as pitting corrosion. The nominal yield strength decreased by 95.68–156.01 MPa, and the nominal tensile strength decreased by 133.44–202.77 MPa because of a decrease in the cross-sectional area. During the corrosion process, major anions such as Cl- continuously degraded the passivation film on the surface of the anchor cable, exposing its internal metal structure and exacerbating corrosion until eventual fracture failure occurred. Therefore, this paper proposes a corrosion protection technique for mine anchor cables to realize superior protective effects compared to conventional anchor cables used concurrently in field applications.

Back to Bernoulli: a simple formula for trans-stenotic pressure gradients and retrospective estimation of flow rates in cerebral venous disease

BackgroundVenous sinus stenosis can be associated with cerebrovascular disorders. Understanding the role of blood flow disturbances in these disorders is often hampered by the lack of patient-specific flow rates. Our...

Electroacupuncture alleviates motor dysfunction by regulating neuromuscular junction disruption and neuronal degeneration in SOD1G93A mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurological disease characterized by the progressive destruction of the neuromuscular junction (NMJ) and the degeneration of motor neurons, eventually leading to atrophy and paralysis of voluntary muscles responsible for motion and breathing. NMJs, synaptic connections between motor neurons and skeletal muscle fibers, are extremely fragile in ALS. To determine the effects of early electroacupuncture (EA) intervention on nerve reinnervation and regeneration following injury, a model of sciatic nerve injury (SNI) was first established using SOD1G93A mice, and early electroacupuncture (EA) intervention was conducted at Baihui (DU20), and bilateral Zusanli (ST36). The results revealed that EA increased the Sciatic nerve Functional Index, the structural integrity of the gastrocnemius muscles, and the cross-sectional area of muscle fibers, as well as up-regulated the expression of acetylcholinesterase and facilitated the co-location of α7 nicotinic acetate choline receptors and α-actinin. Overall, these results suggested that EA can promote the repair and regeneration of injured nerves and delay NMJ degeneration in SOD1G93A-SNI mice. Moreover, analysis of the cerebral cortex demonstrated that EA alleviated cortical motor neuron damage in SOD1G93A mice, potentially attributed to the inhibition of the cyclic GMP-AMP synthase-stimulator of interferon genes pathway and the release of interferon-β suppressing the activation of natural killer cells and the secretion of interferon-γ, thereby further inhibiting microglial activation and the expression of inflammatory factors. In summary, EA delayed the degeneration of NMJ and mitigated the loss of cortical motor neurons, thus delaying disease onset, accompanied by alleviation of muscle atrophy and improvements in motor function in SOD1G93A mice.

The Magnetic Resonance Imaging of the Psoas Muscle Area as the Prognostic Factor for Survival and Adverse Events in Spinal Metastasis Surgery.

Retrospective study. This study aimed to evaluate the ability of the mortality and adverse events prediction following metastatic spinal surgery of MRI-based cross-sectional psoas muscle area (PMA). A retrospective chart review, 120 patients who had undergone metastatic spinal surgery were included. The cross-sectional area identified the PMA under MR-imaging at the L3 or L4 pedicle level, which was classified into 3 tertiles. We used univariate and multivariate cox proportional hazard regression to assess whether PMA was associated with 30-day, 90-day, 1-year, and overall mortality. The small psoas tertile group populations had a higher mortality rate than the large psoas tertile group. PMA in T1 and T2 had a probability of a higher 90-d mortality rate than PMA in T3 (T1 VS T3: P = .29 and T2 VS T3: P = .12). The median survival time was 7months, 9months, and 10months in PMA T1, T2, and T3, respectively. PMA in tertile 2 had a significantly higher mortality rate of 38% compared to PMA in tertile 3 (HR 1.38, 95% CI .83-2.32, P = .02). Considering PMA as a continuous variable, every 1mm2 increment of PMA resulted in the increase survivorship of 1% (HR .99 with 95% CI .99-1). The MRI-based cross-sectional PMA tends to predict the 90-d mortality rate and overall mortality rate in spinal metastasis patients who underwent spinal surgery. The PMA should be considered one of the prognostic factors in the treatment of metastatic spinal patients.

Numerical investigation of the impact of various parameters on blowing accuracy in the XRT intelligent ore sorting machine blowing process

XRT separation equipment is attracting much attention as the mining industry increasingly uses pre-sorting technology. Its sorting accuracy is affected by differences in ore shape and particle size during operation. This paper, in which numerical simulations are conducted to investigate the resistance of ores under various situations, including varying blowing distances, cross-sections, and practical sizes, Additionally, this paper conducts validation tests. The test results indicate that within the 0.1-0.25 m section from the nozzle exit, there is a rapid decrease in velocity, accompanied by a significant change in ore resistance. Beyond the 0.25 m mark, the velocity reduction slows down, while the ore resistance becomes smaller. There exists a notable disparity in the resistance of ores with varying cross-sectional geometries. The size of the jet velocity surface caused by blowing distance significantly influences the resistance of ore with varying particle sizes. Furthermore, the resistance of the ore remains constant subsequent to the impact surface of the ore surpassing the surface of the jet velocity. Consequently, appropriately modifying the blowing distance, inlet pressure, and jet speed in accordance with the cross-sectional area and particle size of the majority of the ores stream can enhance the precision of the sorting process.

Cross-section extraction and model reconstruction of lava tube based on L1-medial skeleton

Lunar lava tube caves, due to their unique geographical structure and potential as shelters, have repeatedly emerged as prime candidates or priority areas during discussions on lunar base site selection. However, owing to current technological limitations and the complexities of lunar exploration, obtaining detailed data directly from the interiors of lunar lava tubes poses a significant challenge. Hence, the study of terrestrial lava tubes assumes critical importance. By delving into Earth’s lava tubes, we can gain insights into crucial aspects such as their formation mechanisms, geological characteristics, and stability, which can then inform and guide research on lava tubes found on extraterrestrial bodies like the Moon and Mars. During the data acquisition process for lava tubes, given their intricate spatial configurations and dim lighting conditions, we have opted to employ LiDAR technology to collect point cloud data, revealing the internal structural information of the lava tubes. Consequently, this paper thoroughly explores a method for extracting lava tube parameters and constructing models using this point cloud data. This approach encompasses four key steps: data preprocessing, axis construction of the lava tube, cross-sectional feature extraction, and 3D model reconstruction. Initially, raw data is refined through the creation of point cloud voxels to mitigate noise interference. Subsequently, an iterative algorithm is utilized to obtain the L1-medial skeleton, enabling precise capture of the lava tube’s axis information. Using this extracted axis, we proceed with sampling at fixed intervals to derive cross-sectional points of the lava tube. These points are then utilized to extract fundamental geometric parameters such as cross-sectional area, length, and width. Ultimately, by integrating all these cross-sectional point cloud data, a comprehensive 3D model of the lava tube is constructed. Remarkably, this method achieves a high degree of accuracy, with 99 % of the extracted cross-sectional points exhibiting an error of less than 0.12 m, and 99 % of the model’s positional errors falling within 0.15 m. This not only enhances the precision of parameter extraction but also provides significant technical support for in-depth studies of extraterrestrial volcanic activities and lava tube formation mechanisms. Furthermore, it offers a valuable tool for parameter extraction and research on other irregular natural tunnels.

The effect of including dynamic imaging derived airway wall motion in CFD simulations of respiratory airflow in patients with OSA

Obstructive sleep apnea (OSA) is an airway disease caused by periodic collapse of the airway during sleep. Imaging-based subject-specific computational fluid dynamics (CFD) simulations allow non-invasive assessment of clinically relevant metrics such as total pressure loss (TPL) in patients with OSA. However, most of such studies use static airway geometries, which neglect physiological airway motion. This study aims to quantify how much the airway moves during the respiratory cycle, and to determine how much this motion affects CFD pressure loss predictions. Motion of the airway wall was quantified using cine MRI data captured over a single respiratory cycle in three subjects with OSA. Synchronously-measured respiratory airflow was used as the flow boundary condition for all simulations. Simulations were performed for full respiratory cycles with 5 different wall boundary conditions: (1) a moving airway wall, and static airway walls at (2) peak inhalation, (3) end inhalation, (4) peak exhalation, and (5) end exhalation. Geometric analysis exposed significant local airway cross-sectional area (CSA) variability, with local CSA varying as much as 300%. The comparative CFD simulations revealed the discrepancies between dynamic and static wall simulations are subject-specific, with TPL differing by up to 400% between static and dynamic simulations. There is no consistent pattern to which static wall CFD simulations overestimate or underestimate the airway TPL. This variability underscores the complexity of accurately modeling airway physiology and the importance of considering dynamic anatomical factors to predict realistic respiratory airflow dynamics in patients with OSA.

Experimental study of micro-prismatic electrode array wear during EDM and application to the preparation of microcylindrical electrode array

The focus of this study is to compare the wear characteristics of different types of micro-prismatic electrode array during EDM, and to propose a method for preparing microcylindrical electrode array based on micro-prismatic electrode array. Firstly, the characteristic of the micro-prismatic electrode that the front cross-section becomes circular after wear during EDM is clarified, and the wear form of the micro-prismatic electrode is analyzed. Then, the laws of the influence of electrode shape (triangle, square, hexagon), electrode material (pure copper, copper-tungsten alloy, pure tungsten), electrode size (200 μm, 300 μm, 400 μm) on the wear characteristics of the micro-prismatic electrode array, including the length of the wear of each part of the electrodes, the length of the area of the front cross-section that becomes rounded, the consistency of the wear of the electrode array, the machining efficiency, and electrode wear rate are summarized. After that, the process of changing the electrode array from square columns to cylinders using the new method is given, which confirms the feasibility of the method. Finally, the effects of peak current and pulse width on the size, machining efficiency, surface roughness, and surface micro-morphology of micro-cylindrical electrode array prepared by the new method are summarized. This study is of great significance for achieving mass production of microcylindrical electrode array.