Cross-sectional Area Distribution Research Articles

A Novel SMFL-Based Assessment Method for Corrosion Nonuniformity of Rebar and Its Application in Reliability Analysis of Corroded RC Beam

The reliability of corroded reinforced concrete (RC) structures relies on the accurate minimum cross-sectional area of corroded rebar. In this study, the accurate morphologies and self-magnetic flux leakage (SMFL) field strengths of twenty-eight non-uniformly corroded rebars were obtained using 3D structural light scanning and micromagnetic detection technologies, based on which three indices of the SMFL field variation ratio dH, the corrosion non-uniformity degree dSn, and the cross-sectional area ratio K0.25 are proposed. The statistical results show that the probability densities of dSn and K0.25 obey the Weibull distribution and Gamma distribution at the 95% confidence level, respectively, and their distribution parameters are linearly or inversely proportional to dH. The probability density distribution of the minimum cross-sectional area of corroded rebar can be determined using indices dSn and K0.25, based on which a feasible SMFL-based reliability assessment method of corroded RC structures is proposed. The case study of a real specific corroded RC beam shows that the reliability assessment error of the SMFL-based method is only 1.2%, which is much lower than the 20.7% error of the existing method. This SMFL-based method provides a novel idea that can automatically and accurately assess the effect of rebars’ corrosion non-uniformity on the reliability of specific in-serviceRC structures.

Muscle Fiber Cross-Sectional Area Is Associated With Quadriceps Strength and Rate of Torque Development After ACL Injury.

Graham, MC, Thompson, KL, Hawk, GS, Fry, CS, and Noehren, B. Muscle fiber cross-sectional area is associated with quadriceps strength and rate of torque development after ACL injury. J Strength Cond Res XX(X): 000-000, 2023-The purpose of this study was to investigate the relationship between muscle fiber type-specific properties of the vastus lateralis and quadriceps muscle performance in individuals after an anterior cruciate ligament (ACL) tear. 26 subjects (22.0 ± 5.4 years) were included in this cross-sectional study, and all data were collected before ACL reconstruction. Quadriceps peak torque (QPT) and early (0-100 ms) and late (100-200 ms) rate of torque development (RTD) were obtained from maximal voluntary isometric quadriceps strength testing. Muscle fiber cross-sectional area (fCSA) and percent fiber type distribution (FT%) were evaluated through immunohistochemical analysis of a muscle biopsy. Between-limb differences in fiber characteristics were assessed using paired t-tests (with α-level 0.05). Relationships between fiber-specific properties and quadriceps muscle performance were determined using separate multiple linear regression analyses for ACL-injured and noninjured limbs. There were significant differences in fCSA between ACL-injured and noninjured limbs across all fiber types, but no differences in FT%. Type 1 fCSA, type 2a fCSA, and their interaction effect were the explanatory variables with the strongest relationship to all performance outcomes for the ACL-injured limb. The explanatory variables in the ACL-injured limb had a significant relationship to QPT and late RTD, but not early RTD. These findings suggest that QPT and late RTD are more heavily influenced by fCSA than FT% in ACL-injured limbs. This work serves as a foundation for the development of more specific rehabilitation strategies aimed at improving quadriceps muscle function before ACL reconstruction or for individuals electing nonsurgical management.

Evaluation of the Correlation Between Distribution Location and Vulnerability of Carotid Plaque in Patients with Transient Ischemic Attack.

To analyze the relationship among distribution location, characteristics, and vulnerability of carotid plaque using CTA and provide more information on the risk factors of carotid atherosclerotic plaque. We retrospectively analyzed the CTA images of the head and neck of 93 patients with carotid atherosclerosis. Atherosclerosis was developed in 148 carotid arteries. The plaques were divided into a high-risk plaque group and a low-risk plaque group according to whether the plaques had high-risk characteristics. The maximum cross-sectional area of carotid artery bifurcation plaque on the axial image was selected, and the cross-sectional lumen was equally divided into four 90-degree sectors, ventral side wall, dorsal side wall, inner side wall, and outer side wall. The differences in the characteristics and distribution locations of the plaques in the two groups were analyzed. The characteristic parameters of the cross-sectional plaques at the bifurcation of the carotid artery. The logistic regression analysis was used to further analyze the risk factors associated with plaque vulnerability. Among 148 carotid arteries,80 were classified as high-risk and 68 as low-risk groups. There were significant differences between the two groups concerning the thickness, length, maximum cross-sectional area, burden, and cross-sectional distribution of the plaques (P < 0.05). The plaque distribution on the dorsal side wall of the carotid bifurcation was higher in the high-risk group than that in the low-risk group (P < 0.05), dorsal side wall plaque-independent risk factors for the development of vulnerability of plaques in transient ischemic attack (TIA) patients (95% CI:1.522~6.991, P<0.05). High-risk plaques tend to occur on the dorsal side wall of the carotid bifurcation, whereas low-risk plaques tend to occur on the outer side wall of the carotid bifurcation.

Performance degradation of steel rebar considering corrosion spatial variability in concrete

The corrosion of steel bars is the main issue affecting the durability of reinforced concrete structures, which is nonuniform owing to the material properties and external environmental effects. In this study, the performance degradation of steel rebars in concrete is estimated considering corrosion spatial variability. With the aid of a three-dimensional measurement technique, a finite element model based on the scanning result was established to examine the corrosion effect on the tensile behaviour of the corroded bars, which was validated with the experimental results and digital image correlation observation. To assess the deformation behaviour of the corroded steels, a semi-analytical model was developed based on the cross-sectional area distribution and material properties. Subsequently, the spatial weight loss distributions with different degrees of corrosion were generated using a random field model. The model parameters were determined by combining engineering judgement and estimation of the experimental results. Finally, probabilistic model of degraded performance was established using the deterministic assessment and simulated steel weight loss distribution.

Effect of nonsteroidal anti-inflammatory drugs on pelvic floor muscle regeneration in a preclinical birth injury rat model

BackgroundPelvic floor muscle (PFM) injury is a common consequence of vaginal childbirth. Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used postpartum analgesics. Multiple studies report negative effects of these drugs on limb muscle regeneration. The impact of NSAIDs on PFM recovery following birth injury has not been explored. ObjectiveUsing the validated rat model, we assessed the effects of NSAIDs on acute and longer-term PFM recovery following simulated birth injury (SBI). Study DesignThree-month old Sprague-Dawley rats were randomly assigned to (1) controls; (2) SBI; (3) SBI + NSAID; or (4) NSAID group. SBI was induced using a well-established vaginal balloon distention protocol. Ibuprofen was administered in drinking water (0.2 mg/ml) ad lib. Animals were sacrificed at 1,3,5,7,10,28 days post birth injury/ibuprofen administration. The pubocaudalis portion of the rat levator ani, which, like the human pubococcygeus, experiences larger parturition-associated strains, was harvested (N=3-9/timepoint/group). The cross-sectional areas of regenerating (embryonic myosin heavy chain (eMyHC)+) and mature myofibers were assessed at the acute and 28-day timepoints, respectively. The intramuscular collagen content was assessed at the 28-day timepoint. Myogenesis was evaluated using anti-Pax7 and anti-myogenin antibodies to identify activated and differentiated muscle stem cells, respectively. The overall immune infiltrate was assessed using anti-CD45 antibody. Expression of genes coding for pro- and anti-inflammatory cytokines was assessed by qRT-PCR at 3,5,10 days post-injury. ResultsThe pubocaudalis fiber size was significantly smaller in the SBI+NSAID compared to SBI group at 28 days post-injury, P<0.0001. The median size of eMyHC+ fibers was also significantly reduced, with fiber area distribution enriched with smaller fibers in SBI+NSAID compared to SBI group at 3 days post-injury (P<0.0001), suggesting a delay in the onset of regeneration in the presence of NSAIDs. By 10 days post-injury, the median eMyHC+ fiber size in the SBI group decreased from 7 days post-injury (P<0.0001) with a tight cross-sectional area distribution, indicating nearing completion of this state of regeneration. However, in the SBI+NSAID group, the size of eMyHC+ fibers continued to increase (P<0.0001) with expansion of the cross-sectional area distribution, signifying a delay in regeneration in these animals. NSAID decreased the muscle stem cell pool at 7 days post-injury (P<0.0001) and delayed muscle stem cell differentiation, as indicated by persistently elevated number of myogenin+ cells 7 days post-injury (P<0.05). In contrast, the proportion of myogenin+ cells returned to baseline by 5 days post-injury in the SBI group. The analysis of expression of genes coding for pro- and anti-inflammatory cytokines demonstrated only transient elevation of Tgfb1 in SBI+NSAID group at 5 but not at 10 days post-injury. Consistent with previous studies, SBI+NSAID resulted in increased deposition of intramuscular collagen compared to uninjured animals. There were no significant differences in any outcomes of interest between the NSAID group and the unperturbed controls. ConclusionsNSAIDs negatively impact PFM regeneration in the preclinical SBI model. The above appears to be driven by the negative impact of NSAIDs on pelvic muscle stem cell function, resultant in delayed temporal progression of PFM regeneration following birth injury. These novel findings provide impetus to investigate the impact of postpartum NSAID administration on muscle regeneration in women at high risk for PFM injury.

Existence and approximation of densities of chord length- and cross section area distributions

In various stereological problems an $n$-dimensional convex body is intersected with an $(n-1)$-dimensional Isotropic Uniformly Random (IUR) hyperplane. In this paper the cumulative distribution function associated with the $(n-1)$-dimensional volume of such a random section is studied. This distribution is also known as chord length distribution and cross section area distribution in the planar and spatial case respectively. For various classes of convex bodies it is shown that these distribution functions are absolutely continuous with respect to Lebesgue measure. A Monte Carlo simulation scheme is proposed for approximating the corresponding probability density functions.

Influence of abrasive waterjet pre-cutting slit on the performance of shield cutter cutting reinforced concrete

To improve the efficiency and safety of shield machines cutting reinforced concrete (RC) obstacles, using an abrasive waterjet (AWJ)-assisted shield cutter to cut RC is considered a feasible solution. To explore the effect of an AWJ on a shell cutter cutting RC, laboratory experiments and numerical simulation methods were used to compare the breaking performance and damage mechanism of a shell cutter cutting RC with and without a slit. The results showed that the waterjet pre-cutting slit could effectively reduce the cutter force of the shell cutter and promote the cutting of steel bars. The reduction rate of the cutter force by the waterjet slit increased and then decreased with an increase in the penetration degree. When the penetration degree was 1.5 mm, the waterjet cutting slit had the best reduction effect on the cutting force. An optimal critical value was found for the waterjet cutting slit of the steel bar; when the waterjet slit was larger than ½ of the diameter of the steel bar, the steel bar was prone to tensile fracture under the cutting action. The waterjet pre-cutting slit reduced the residual cross-sectional area and stress distribution of the steel bar, which promoted the bending and tensile fracture of the steel bar and thus improved the cutting efficiency. Furthermore, construction recommendations for the AWJ-assisted shield cutting of RC obstacles were identified. The findings presented in this paper can provide useful reference information for the design and construction of AWJ shield machines.

Effect of stress level and localized corrosion on the strain transfer between corroded steel rebar and distributed fiber optic sensor

Distributed fiber optic sensors (DFOSs) have become an effective tool for deformation and cracking monitoring in reinforced concrete structures due to their multiple sensing points. However, the monitoring accuracy is affected by the strain transfer efficiency between the monitored structural substrate and DFOS. This study experimentally investigates the effect of localized corrosion and stress level on the strain transfer efficiency between corroded steel rebars and DFOS. Steel rebars installed with DFOS were cast in a concrete slab and then subjected to accelerated corrosion tests up to ∼ 12.00% area loss. The residual cross-sectional area distribution of corroded steel rebars was determined based on 3D laser scan data. Tensile tests were conducted, during which the strain distribution of DFOS under different loading levels was recorded with an optical interrogator and then compared with theoretical values. Results show that corrosion does not directly affect the strain transfer efficiency between steel rebars and DFOS, but spatial variation of corrosion causes high strain gradients in steel rebars that result in erroneous strain readings. DFOSs are able to identify the location of big corrosion pits, but the strain transfer coefficient is less than 100% at locations with big corrosion pits while it is over 100% at nearby sections. The strain transfer coefficient increases with an increase in stress level in the elastic stage of steel rebars, while it decreases with an increase in area loss especially for sections with pitting corrosion.

1641-P: C-C Motif Chemokine Ligand 2 Promotes Myogenesis Recovery, Muscle Strength, and Muscle Performance In Vivo and Has Clinical Relevance for Muscle Performance in Human

Muscle mass decreases with aging, while the C-C motif chemokine ligand 2 (CCL2) increases with aging. In our previous study, CCL2 positively affects in vitro myogenesis. In this context, CCL2 can be considered a potential aging-promoting factor. To further confirm the relationship between muscle and CCL2, we sought to establish the role of CCL2 in vivo and in humans. It was divided into Dimethyl Sulfoxide (DMSO) control, dexamethasone (Dexa) intraperitoneal treatment group, and Dexa with the CCL2 treatment group. As a result, grip power and exercise endurance were reduced in the Dexa treatment group compared to the control group but recovered with the CCL2 treatment. In muscle mass, there was no significant difference in mass between groups. We examined the cross-sectional area distribution (CSA) with the tibialis anterior muscle. The Dexa treatment group was distributed between CSA 1000-3000 µm² and was left-shifted. However, the Dexa and CCL2 group was similar or slightly higher than the DMSO group; it was right-shifted and distributed in the 2000-5000 µm². In humans, the median value was 303.8 pg/ml in the no sarcopenia group and 321.7 pg/ml in the sarcopenia group. Subsequently, the CCL2 level was checked by dividing the groups into whether there was sarcopenia, low mass, low strength, or low speed. The CCL2 level was statistically significantly higher in the group showing low speed. In conclusion, CCL2 promotes myogenesis recovery, muscle strength, and muscle performance in vivo and has clinical relevance for muscle performance in humans. Disclosure E.Hong: None. E.Ha: None. J.Lee: None. Y.Choi: None. K.Lee: None. J.Won: None. M.Kwak: None. Funding Ministry of Education, Republic of Korea (2020R1I1A3073230)

Effect of ultrasonic power on moisture migration and microstructure of contact ultrasound enhanced far-infrared radiation drying on taro slices

To clarify the moisture migration and microstructure of taro in contact ultrasound enhanced far-infrared radiation drying (CUFRD), low-field nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), paraffin sectioning and microscopic observation techniques were applied to explore the changes of the drying curves, water status, microstructure, porosity, microscopic images and distribution curves of cell microstructure parameters of taro under different ultrasound powers of 0, 40, and 80 W. The results showed that applying contact ultrasound (CU) during drying was beneficial to accelerating the dehydration process and improving the porosity of taro slice. With the augment of CU power, the drying times of taro reduced by 16.67% to 25.00%, and the effective water diffusion coefficient was improved by 14.72% to 31.38%. In addition, the application of CU resulted in an increase firstly and then decrease in the cross-sectional area and perimeter distribution curves of taro cells and a widening of the peak shape of the distribution curve of taro cell roundness. In conclusion, CU application could cause faster internal moisture migration, and higher CU power had more obvious effect on microstructure and cell morphological parameters of taro during CUFRD.

Hyperglycaemia Attenuated C2C12 Myoblast Proliferation and Induced Skeletal Muscle Atrophy via Modulating Myogenic Regulatory Factors Genes Expression in Diabetic Rats

Diabetes mellitus is characterised by high blood glucose level termed hyperglycaemia (HG). It has been reported to affect skeletal muscle by inducing skeletal muscle atrophy and skeletal muscle protein degradation leading to impairment of muscle function. This study aimed to investigate the effects of HG on the expression of myogenic regulatory factor genes in muscle progenitor cells and in skeletal muscle. The number of C2C12 myoblasts cultured in HG condition was significantly decreased compared to control in dose and time dependent manner. In addition, the number of Ki-67 positive nuclei was significantly decreased after treatment under HG condition. Real time PCR showed significant suppression of MyoD and myogenin, while Myf5 gene expression was significantly enhanced, compared to control. Furthermore, histological examinations of muscle fibres showed atrophy of tibialis anterior (TA) muscle from diabetic rats. The frequency of distribution of muscle fibre cross-sectional area (MCA) in diabetic rats was shifted leftward from that of normal control rats. In contrast, the MyoD and myogenin expression in TA muscle of diabetic rats were significantly increased compared to normal control rats. This study provides novel knowledge on the changing myogenic regulatory factor gene expression in hyperglycaemic condition, both in vitro and in vivo, leading to skeletal muscle atrophy.

Integrating Real Tree Skeleton Reconstruction Based on Partial Computational Virtual Measurement (CVM) with Actual Forest Scenario Rendering: A Solid Step Forward for the Realization of the Digital Twins of Trees and Forests

Digital twins of forests (trees) are computational virtual recreations of forests (trees) in which the entity distributions and physical processes in real-world forests (trees) are duplicated. It is expected that conventional forest science and management can be undertaken in a digital twin of forests (trees) if the recreation of a real-world forest (tree) has accurate and comprehensive enough information. However, due to the various differences between the current tree model and the real tree, these envisioned digital twins of the forests (trees) stay a theoretical concept. In this study, we developed a processing strategy that partially integrated computational virtual measurement (CVM) process into the tree modeling workflow. Owing to the feature of CVM, partial tree skeleton reconstruction procedures were considered to have higher mechanical objectivity compared to conventional mathematical modeling methods. The reason was that we developed a novel method called virtual diameter tape (VDT), which could provide a certain percentage of modeling elements using CVM. Technically, VDT was able to virtually measure diameters and spatial distribution of cross-sectional area of trees, including the basal area, from point clouds. VDT simulated the physical scenario of diameter tapes, observing point clouds of trees. Diameter and the cross-sectional area of stem and branches were obtained by two consecutive physical measurement processes, one in the forest sample site and another in the virtual space. At the same time, VDT obtained better or a similar accuracy compared to the mathematical methods, i.e., Hough transform-based methods, using the same data sets. The root-mean-square deviation (RMSE) of retrieval of diameter at breast height (DBH) using VDT was 1.02 cm, while DBH obtained from three conventional methods varied from 1.29 cm to 1.73 cm. Based on VDT measurement results, tree skeleton reconstruction and actual forest scenario rendering of our sample plots were further implemented. Beyond the visual consistency, we believe that our work might be a small and solid step in the technological evolution from tree models to the digital twin of forests (trees).

Pseudospectral Approach to the Shape Optimization of Beams Under Buckling Constraints

In this article, a direct transcription approach to the minimization of the volume of elastic straight beams undergoing plane deformation and subject to buckling loads is presented. In particular, the so-called pseudospectral method is employed, where state variables are approximated by Lagrange interpolating polynomials and static equations are collocated at Legendre-Gauss-Radau nonuniform mesh points. The resulting shape optimization problems are thus transcribed into constrained nonlinear programming problems, which in turn are solved by developed routines. Historical benchmark and academic problems such as simply supported beams subject to a concentrated compressing force, compressed and rotating cantilever beams and simply supported beams under a non-conservative follower distributed load are revisited and numerically solved under the conditions of plane deformation theory. Numerical solutions are discussed and compared to those obtained by the shooting method, which is largely employed for these problems, emphasizing how the proposed method could forecast optimal cross sectional area distributions within a unified fashion and without resorting to accurate guesses beforehand.

Numerical investigation on multi-stage swirl cooling at mid-chord region of gas turbine blades

• Numerical research on the multi-stage swirl cooling using fluid–solid-thermal coupled method for Turbine blade. • The multi-stage swirling cooling is designed with the better comprehensive thermal performance. • The high cooling effectiveness and uniform temperature distribution are obtained through adjusting cross-section area distribution of the chambers. • The temperature uniformity of the adjusted structure is less affected by Reynolds number. Compared with the single-stage one, the multi-stage swirl cooling technique has great potential at the mid-chord region of gas turbine blades. Currently, the effect of the chamber structure at the mid-chord region of the blades on the multi-stage swirl cooling is still unknown. In this study, four kinds of the multi-stage swirl chamber models are built: Case 1 has two swirl nozzles and three chambers, and cases 2–4 have six swirl nozzles and seven chambers. Fluid flow and heat transfer characteristics of the coolant in the swirl cooling configurations are numerically investigated. The standard k-ε turbulent model is adopted in current study and the Reynolds number of the coolant varies from 12,000 to 52000. The results show that the long swirl chamber in case 1 has negative effect on the performance of the swirl cooling this is because the swirl velocity along the axial direction is gradually reduced and the Nusselt number is decreased remarkably. For cases 2–4, the chambers are separated into several short ones. Therefore, the swirl velocity could keep high value and so is the Nusselt number. Although more swirl chambers could lead to higher pressure loss coefficient, cases 2–4 show better comprehensive thermal performance as compared to case 1. Among the current cases, the swirl chamber structure in case 4 shows the highest cooling effectiveness and obtains more uniform temperature distributions on the external surface of the blade.

An Improved Glottal Flow Model Based on Seq2Seq LSTM for Simulation of Vocal Fold Vibration

An improved data-driven glottal flow model for fluid-structure interaction (FSI) simulation of the vocal fold vibration is proposed in this paper. This model aims to improve the prediction performance of the previously developed deep neural network (DNN) based empirical flow model (EFM)1 on accuracy and efficiency. A Seq2Seq long short-term memory (LSTM) network is employed in the present model to infer the flow rate and pressure distribution from the subglottal pressure and cross-sectionarea distribution of the glottis. The training data is collected from the generalized glottal shape library generated in Zhang etal.1 RESULTS AND CONCLUSIONS: Compared to the EFM, the present model not only discards the time-consuming optimization process, but also drastically reduces the errors, therefore the prediction performance can be greatly improved. The present model is evaluated by coupling with a solid dynamics solver for FSI simulation, and the results demonstrate a great improvement on accuracy and efficiency.

IMPLEMENTATION OF TRANSONIC AREA RULE AND SWEPT BACK DELTA WING DESIGN ON AN AIRCRAFT.

The transonic area rule was first implemented in the 1950s. It is an important concept related to the drag on an aircraft or other body in transonic and supersonic flight which states that two airplanes with the same longitudinal cross-sectional area distribution have the same wave drag, independent of how the area is distributed laterally. A swept back delta wing increases the critical Mach number of the wing and performs well at low speeds, as a result of unique swirling vortices that form on the upper surface of the wing. BOOM Supersonic plans to bring back Supersonic Commercial aircrafts by implementing these modifications in the famous Concorde. In this paper two aircraft designs inspired by Concorde and BOOM Overture are compared using ANSYS Fluent. These were designed in CATIA with changes in fuselage dimensions, wing configuration and engine configuration. The lift to drag ratio of both the designs are calculated and compared. Pressure contours, velocity vectors, vector pathlines, turbulence pathlines and pressure pathlines are also compared. The results show that the design with the implementation of transonic area rule and swept back delta wing has a better Lift to Drag ratio when compared to the design with a wide fuselage and a delta wing design.

Multistep train nose for reducing micro-pressure waves

The peak value of a micro-pressure wave radiating from tunnel portals of high-speed railways depends on the shape of the train nose. Previous studies have shown that a train nose shape with a small gradient of cross-sectional area distribution, except at the tip and end, is effective at reducing micro-pressure waves. Using acoustic theory, this study showed that multistep train noses are more effective at reducing micro-pressure waves than the previously suggested nose shapes. Moreover, the multistep noses were optimized using the response surface method and computational fluid dynamics techniques for axisymmetric compressible airflow. In addition, model experiments were performed to verify the usefulness of the optimized multistep noses. The optimized multistep noses reduced the peak values of the micro-pressure wave by over 5% compared to the previous noses. Thus, this study theoretically, numerically, and experimentally suggests new optimal nose shapes that can better reduce micro-pressure waves than existing shapes.

1.5 kW 유도전동기 엔드링 기공이 회전체 진동 및 베어링 내구성에 미치는 영향 분석

This paper presents the results of rotordynamic analyzing the effect of the end-ring porosity of a 1.5 kW induction motors on the rotor vibration and the bearing durability. Firstly, the end ring porosity shape of the induction motor was simplified by the porosity cross-sectional area (S) and porosity distribution angle (θ), and a mathematical model was established to calculate the amount of unbalance. The amount of unbalance due to porosity shape was analyzed through a mathematical model. As a result, it was confirmed that the amount of unbalance significantly increased to more than the balancing grade G40 by S and θ. In general, the proper balancing class for induction motors is G2.5. Second, a rotordynamic analysis model was developed that can predict the vibration characteristics of rotor. In addition, the analysis model was validated through the modal test. Finally, the vibration characteristics of the rotor were analyzed according to the amount of unbalance and phase angle through the rotordynamic analysis. As S decreases, the maximum rotor amplitude linearly decreased and the bearing life increased. As θ increases, the maximum rotor amplitude nonlinearly decreased and the bearing life increased. As the phase angle increases, the maximum rotor amplitude decreased by 75% and the bearing life increased 63 times.

Experimental Investigation to Evaluate the Behavior of Concrete-Filled Steel Tubular Columns under the Effect of the Distribution of the ‎Total Steel Area between the Internal Concrete Core and the External Steel Tube

Composite columns are generally installed in high-rise buildings and bridges. As well as being smaller and lighter than conventional reinforced concrete columns, composite columns offer high efficiency and ductility. In this research, experimental and analytical studies were carried out to investigate the optimal distribution of the ‎total steel area of the Concrete-Filled Hollow Steel Tube (CFHST) columns; the experimental program included 20 CFHST columns. ‎The main variables of the experimental study were the distribution of the total steel cross-sectional area over the internal concrete core (steel reinforcement) and the external steel tube, the cross-sectional shape, the width-to-breadth ratio t/b, and the presence or absence of shear connectors. In addition, using equations of different codes, comparison was conducted between the experimental and analytical results. For a constant steel cross-sectional area, the use of internal steel bars and external steel tubes, together with the use of shear connectors, was found to exhibit a better ultimate load capacity, stiffness, and ductility for the CFHST columns.

In situ Pumping Rate of 20 Marine Demosponges Is a Function of Osculum Area

Sponges play a key role in the transfer of energy and nutrients into many benthic ecosystems, and the volume of water they process is an important regulator of these fluxes. Theoretical scaling relationships between sponge volume, osculum cross-sectional area, and pumping rates were recently proposed and confirmed for small sponge specimens in the lab. To examine how these relationships apply to field populations we measured, in situ, the pumping rate (PR) of 20 species representative of different morphologies and host types (high- and low-microbial-abundance, HMA and LMA) from temperate and tropical regions. The total oscula area (∑OSA) increased allometrically with sponge volume (V) exhibiting similar exponents (∑OSA=aVb, b ranging 0.6–0.7) for all species, except for tropical HMAs (b = 0.99). Osculum flow rate (OFR) also increased allometrically with OSA and oscula of the same size pumped at the same rate irrespective of sponge volume. As a result, and in contrast to former reports, the PR of most of the sponges increased allometrically (PR=a∑OSAb) with scaling exponent b≈0.75, whereas PR of tropical HMAs increased isometrically. Osculum jet speed declined with the increase in the OSA for most species. The number of oscula and their OSA were the best predictors of the PR in sponges, explaining 75–94% of the in situ variation in PR throughout the natural range of sponge size. The pumping rate of a sponge population can be estimated by measuring the osculum density and cross-sectional area distribution once the relationships between the OSA and OFR are established for each species.