Leg Angle Research Articles

Automated Measurements of Long Leg Radiographs in Pediatric Patients: A Pilot Study to Evaluate an Artificial Intelligence-Based Algorithm.

Assessment of long leg radiographs (LLRs) in pediatric orthopedic patients is an important but time-consuming routine task for clinicians. The goal of this study was to evaluate the performance of artificial intelligence (AI)-based leg angle measurement assistant software (LAMA) in measuring LLRs in pediatric patients, compared to traditional manual measurements. Eligible patients, aged 11 to 18 years old, referred for LLR between January and March 2022 were included. The study comprised 29 patients (58 legs, 377 measurements). The femur length, tibia length, full leg length (FLL), leg length discrepancy (LLD), hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA) were measured automatically using LAMA and compared to manual measurements of a senior pediatric orthopedic surgeon and an advanced practitioner in radiography. Correct landmark placement with AI was achieved in 76% of the cases for LLD measurements, 88% for FLL and femur length, 91% for mLDFA, 97% for HKA, 98% for mMPTA, and 100% for tibia length. Intraclass correlation coefficients (ICCs) indicated moderate to excellent agreement between AI and manual measurements, ranging from 0.73 (95% confidence interval (CI): 0.54 to 0.84) to 1.00 (95%CI: 1.00 to 1.00). In cases of correct landmark placement, AI-based algorithm measurements on LLRs of pediatric patients showed high agreement with manual measurements.

Kinematic analysis on segment angle and angular velocities of recovery leg of world elite race walkers regarding race-walking judgement on world elite competition of athletics

Kinematic analysis on segment angle and angular velocities of recovery leg of world elite race walkers regarding race-walking judgement on world elite competition of athletics

Numerical analysis of the seismic performance of existing steel frames with rigid connection with truss-beam-segments

Addressing the insufficient research on fully welded connection with truss-beam-segments (FWCT), this study conducts a comprehensive investigation into the seismic performance of FWCT and its associated steel frame. Primary parameters influencing the seismic performance of FWCT are examined through numerical analysis, and a design method for FWCT is provided. Subsequently, a time-history analysis of composite frames with FWCTs is proposed to investigate the effect of adding truss-beam-segments during rare earthquakes on the seismic performance of the structure as a whole, along with reinforcement recommendations. The study results show that the width of the truss-beam-segment (TS) should ideally be equal to the width of the beam flange, with a thickness equal to that of the beam flange. The net height should be less than or equal to 0.17 times the clear height of the steel beam. The horizontal angle of the external diagonal leg should be less than or equal to 40°, and the length of the horizontal short leg should be greater than the plastic deformation region length at the beam root. The axial compression ratio for the column should be less than 0.7 to prevent local buckling of the column. As the thickness of the composite slab increases, the initial stiffness and load-bearing capacity of the positive moment region gradually increase, while those of the negative moment region remain relatively constant. Time-history analysis indicates that the maximum story displacement and inter-story displacement of the composite frame with TSs are reduced by 4.7 %–5.3 % and 2.5 %–5.8 %, respectively, compared to the composite frame without TSs under seismic wave action. This implies an enhanced capacity of the composite frame with TSs to withstand lateral deformation. For a mid-to high-rise composite frame with n stories, the addition of TSs was recommended primarily for the first (n/2 + 1) floors where plastic regions occur, aiming for a more economically efficient retrofit design and enhanced seismic performance.

HF/HR VSP acquisition, processing, and interpretation in the deviated section of the high angle geothermal borehole of Grigny GGR5, targeting intra Dogger thin, porous beds.

Defining 5m thin, or even thinner, porous reservoir beds was the feasibility objective assigned to the High Frequency/High Resolution (HF/HR) look ahead VSP survey to be recorded in the deviated section of a geothermal production well drilled down to the top of the carbonate Dogger aquifer in the Paris basin, around 1500m in vertical depth, with a landing angle of 65°. The idea was to predict the depth of the first porous bed(s) to be drilled at high angle, and to determine the minimal DLS (Dog Leg Severity) to be applied by the driller after setting a production casing at the top Dogger level and changing the drilling fluid composition, so as to avoid directional drilling with sharp angles. A 50-100m vertical depth range was targeted for the acoustic impedance to be predicted below the top Dogger carbonate aquifer. Besides, a Pilot Hole (PH) was drilled prior to the high angle leg to assess with full reliability the depth of productive thin beds to be subsequently drilled at high angle. These actions were undertaken within a global R&D project named “SISMOSUB” aiming reservoir characterisation, conducted by the reservoir and drilling engineers of GEOFLUID/GPCIP, in a partnership with IFPEN, and partially financed by ADEME (French Agency for Ecological Transition). High Frequency (HF) VSP still represents a frontier seismic domain to investigate, for which technical difficulties are piling up: First, the surface fix source needs to be extremely repeatable and preferably deliver an increased amount of HF energy to compensate somehow for the higher loss of seismic amplitudes with high frequency. Second, downhole receiver tool or toolstring may not present constant vector fidelity of 3 component reception over the whole recording frequency range, mainly in high frequency, due to mechanical coupling characteristics of the VSP tool hardware and the open borehole ruggedness; in cased hole, the mechanical coupling of the VSP tool to the formation is insured by a good cementing quality between casing and borehole wall. Third, the physics of the seismic attenuation is not fully understood and depends on several factors, mainly viscoelasticity and heterogeneity, potentially variable in depth and laterally to the wellbore. Additionally, the geometrical spreading represents the main factor of amplitude decay, independent from frequency, and can be estimated at processing stage. Surprisingly, the VSP image produced underneath the deviated hole section evidenced a faulted structure. A remarkable abrupt amplitude loss of high frequencies above 120Hz occurs where the direct P-wave ray crosses one of the confirmed minor faults before reaching Total Depth (TD); secondary downgoing arrivals appear locally in depth, mainly in the high frequencies, which are not strictly parallel to the first P-wave arrival...

Longitudinal study of three-dimensional pelvic behaviour in maximal sprint running

The kinematics and kinetics of pelvis are associated with sprint performance. In this study, we aimed to investigate the longitudinal changes in the kinematics and kinetics of the pelvis in response to increasing sprinting velocity. Nine male sprinters performed 60 m regular sprints starting from a crouching start position, once a year. A three-dimensional motion analysis was performed to longitudinally investigate the changes in the pelvic movements and force exertion characteristics during sprinting. Sprinting velocity was significantly higher in the post-test than the pre-test. Step frequency was significantly higher in the post-test than the pre-test. The pelvic anterior/posterior tilt angle at stance leg touch-down, stance leg toe-off, and free leg touch-down were significantly smaller in the post-test than the pre-test. The thigh angle of the stance leg at stance leg toe-off and free leg touch-down were significantly smaller in the post-test than in the pre-test. The integrated contributory component of the lumbosacral joint torsion angular impulse during the stance phase was significantly greater in the post-test than the pre-test. This study provided new insights into the longitudinal evaluation of sprint performance in the transverse plane, focusing on pelvic movement and force exertion characteristics.

Comparing a Portable Motion Analysis System against the Gold Standard for Potential Anterior Cruciate Ligament Injury Prevention and Screening.

Knee kinematics during a drop vertical jump, measured by the Kinect V2 (Microsoft, Redmond, WA, USA), have been shown to be associated with an increased risk of non-contact anterior cruciate ligament injury. The accuracy and reliability of the Microsoft Kinect V2 has yet to be assessed specifically for tracking the coronal and sagittal knee angles of the drop vertical jump. Eleven participants performed three drop vertical jumps that were recorded using both the Kinect V2 and a gold standard motion analysis system (Vicon, Los Angeles, CA, USA). The initial coronal, peak coronal, and peak sagittal angles of the left and right knees were measured by both systems simultaneously. Analysis of the data obtained by the Kinect V2 was performed by our software. The differences in the mean knee angles measured by the Kinect V2 and the Vicon system were non-significant for all parameters except for the peak sagittal angle of the right leg with a difference of 7.74 degrees and a p-value of 0.008. There was excellent agreement between the Kinect V2 and the Vicon system, with intraclass correlation coefficients consistently over 0.75 for all knee angles measured. Visual analysis revealed a moderate frame-to-frame variability for coronal angles measured by the Kinect V2. The Kinect V2 can be used to capture knee coronal and sagittal angles with sufficient accuracy during a drop vertical jump, suggesting that a Kinect-based portable motion analysis system is suitable to screen individuals for the risk of non-contact anterior cruciate ligament injury.

Numerical study of transient supercooling performance and thermal stress analysis of segmented annular thermoelectric cooler

A multiphysics-coupled numerical simulation of a segmental annular thermoelectric cooler (SATEC) was performed using a three-dimensional finite element method. A coupling model of the temperature, stress, and electric fields was established based on the three-dimensional transient states. Moreover, the effects of different pulse width (τ), pulse current amplitude (Pa), pulse current shape parameter (m), heat transfer coefficient (h), angle (θ), and length (H) of the thermoelectric leg on the SATEC transient properties and von Mises stress were studied. The results show that τ and Pa are the key influencing factors of SATEC. The larger the h, the more optimized the heat transfer effect of the SATEC hot end. However, when h increased to a certain value, the changes in the transient performance were insignificant. The optimal pulse can be achieved when the input pulse current Iop = 6.47 A and pulse width τ = 20 s. When the length of the thermoelectric leg H4 was 3 mm and the thermoelectric leg angle θ2 was 7°, the performance of SATEC was optimal, with Tc,min being 249.57 K, Tc,max being 279.50 K, thold being 5.5 s, and the maximum von Mises stress being 37.48 MPa. The results show that different supercooling indices and von Mises stresses could be obtained for different pulse current shapes. Geometric optimization of SATEC can improve the cooling performance and reduce the von Mises stress, thereby providing a theoretical reference for practical engineering applications and thermoelectric cooling research.

CPG-Fuzzy Heading Control for a Hexapod Robot with Arc-Shaped Blade Legs

Based on the central pattern generator (CPG) and fuzzy controller, this paper proposes a heading control method for the directional motion for a new type of blade legged hexapod robot (BLHR). First, the modified Hopf oscillator is used to construct the CPG model of BLHR based on the limit cycle. Second, the fuzzy controller is applied to adjust the support angles of legs to change the heading of BLHR, thereby correcting the error between the actual and desired heading angle in real-time. Finally, the feasibility and effectiveness of the proposed CPG-Fuzzy control method is verified in Gazebo simulations and real-world experiments. This is the first attempt to combine CPG and fuzzy control in the context of hexapod robot. In comparison to existing control methods, the proposed CPG-Fuzzy controller can implement heading control of BLHR with better performance and value of further investigation.

Correlation analysis between biomechanical characteristics of taekwondo double roundhouse kick and effective scoring of electronic body protector.

Objective: To explore the inherent relationship between lower limb biomechanical indicators and effective scoring values of double roundhouse kick (DRK) by taekwondo athletes, and to find key biomechanical factors that trigger effective scoring. Methods: Using the DAEDO Protector and Scoring System (PSS) in conjunction with the Vicon optical motion capture system and Kistler 3D force plate, kinematic and dynamic indicators of the front kicking motion were obtained from 12 professional taekwondo athletes (18.00 ± 2.20years, 182.15 ± 8.62cm and 70.00 ± 14.82kg). The correlation between kinematics, dynamics, and scoring values was initially analyzed using bivariate linear correlation. Subsequently, based on the results of the linear correlation analysis, a stepwise regression analysis was performed to establish a stepwise regression equation. Results: The results reveal that during the First Hit, there is a significant positive correlation (r > 0, p < 0.05) between peak hip flexion angular velocity of the dominant leg, knee abduction angle, and peak foot horizontal plane linear velocity of the non-dominant leg with effective score. On the other hand, peak ankle flexion angular velocity of the non-dominant leg, peak foot sagittal plane linear velocity, peak hip abduction angle, and peak hip flexion angle of the dominant leg exhibit a significant negative correlation (r < 0, p < 0.05) with effective score. These correlations hold statistical significance (DW> 1.023). During the Second Hit, there is a significant positive correlation (r > 0, p < 0.05) between peak ankle internal rotation angular velocity of the dominant leg, foot coronal plane linear velocity, hip adduction angular velocity, and peak ankle internal rotation moment of the non-dominant leg with effective score. Conversely, peak hip flexion angle of the dominant leg shows a significant negative correlation (r < 0, p < 0.05) with effective score. All these variables have a statistically significant impact on effective score (DW > 1.023). Conclusion: Explosive power, body posture, adequate terminal velocity, and body rotation have an association with effective scoring of the electronic protector. The peak angular velocity of the ankle joint of the dominant leg and the peak linear velocity of the foot horizontal plane of the non-dominant leg significantly contribute to the effectiveness score of the electronic protector.

Investigation of outcome measures and anomalous lower extremity in osteoarthritis patients with Jumpstart nutrition® supplementation.

Osteoarthritis (OA) is characterized by cartilage and synovial inflammation as well as anomalous lower extremity leading to joint pain, and impairment in lifestyle and epidemic of obesity. This study aimed to use the Jumpstart Nutrition® supplement (JNS) for achieving symmetry of aberrant lower extremity and improving the outcome measures in the management of OA. This week-twelve registry included 108 patients treated with JNS mainly comprised of calcium, phosphorus, magnesium, vitamin-K2, coenzyme-Q10, vitamin-C, boswellic acids, and curcumin mixed with soy and whey proteins (experimental group) and 72 were treated with symptomatic slow-acting drugs (control group) for chronic OA confirmed with radiological images. The outcome measures (Visual analogue scale, Western Ontario and McMaster Universities Osteoarthritis Index, Knee-injury Osteoarthritis Outcomes Scale, and Body mass index), and anomalous lower extremity included bilateral: knee gaps between biceps femoris-short head and surface of the bed, diameters of muscles at the calf, the thigh, 4cm above and below the patella, angles of straight leg raising, knee- flexion and-extension in supine were evaluated with appropriate protocol at week-0 and at week-12 for both the groups. After week-12, risk ratios of studied lower extremity, and mean ±standard deviation of all outcome measures were significantly improved (p<0.0001), and Kellgren-Lawrence scale (KLS) was upgraded to ≥2 in experimental group compared to control. This registry study indicates that JNS can be used to achieve symmetry of studied lower extremity and to improve the outcome measures safely as an effective management of OA patients confirmed with radiological images correlated with KLS.

Biomechanical analysis of the danger of the whip-leg striking maneuver in martial arts sparring bouts

Abstract This paper recognizes the human motion in martial arts movements based on the LSTM recurrent neural network algorithm, which uses signal statistics to extract the action time series features through the data collection from the relevant human motion sensors in order to effectively recognize the athletes’ movements. The parameter settings of the LSTM neural network model are optimized using an improved particle swarm algorithm. The experimental process is then created. After filming the video, it is divided into two documents, A and B, and saved. The experimenter’s actions undergo technical analysis using LSTM. Three groups of athletes were invited to carry out the actual test after the design was completed, and biomechanical analysis was performed based on the experimental data. The experiments showed that the activation of the left medial femoral muscle of the athletes was greater than that of the left lateral femoral muscle, and the root mean square of electromyography was 25.38±11 and 27.54+11, respectively. The angle of the left leg was 69±2.5, and that of the right leg was 71±9.2, which was more than 80% of the safe rotational amplitude. It is easy to cause sports injury if there is too much difference in the activation level of leg muscles during whiplash.

Effects of simultaneous short-term neuromuscular electrical stimulation and static stretching on calf muscles.

[Purpose] The simultaneous application of static stretching and neuromuscular electrical stimulation (NMES) to calf muscles may enhance physiological parameters in young and healthy individuals; however, the efficacy of this intervention and potential sex variation remain to be elucidated. The present study aimed to investigate these aspects. [Participants and Methods] Thirty healthy university students (15 males and 15 females) participated in this study. All participants simultaneously underwent static stretching and NMES of the calf muscles for 4 min while lying on an upright and tilted table. The mean differences in the dorsiflexion angle (DFA), finger-floor distance (FFD), and straight leg raising (SLR) angle before and after the intervention were calculated. Sex variations were assessed using a two-way analysis of variance (ANOVA). [Results] The DFA, FFD, and SLR angle exhibited significant effects on time. No significant sex variations were observed between the groups. [Conclusion] Simultaneous static stretching and NMES of the calf muscles potentially enhanced the DFA, FFD, and SLR angle in healthy university students, irrespective of sex.

The Relationship Between Hamstring Shortness and Postural Control in Football Players: A Pilot Study

Hamstring muscles significantly contribute to lower limb mobility and overall body balance. Specifically, hamstring muscle tightness has been suggested as a potential factor affecting an athlete’s postural control. Therefore, this study aims to contribute to the ongoing discourse by investigating the possible relationship between hamstring muscle tightness and postural control among football players. Sixteen male football players (mean age: 20.19 ± 2.17 years, body mass index: 22.01 ± 1.82 kg/m2) with hamstring muscle tightness participated in this cross-sectional study. The assessment of hamstring muscle tightness was conducted through the Active Knee Extension Test. Additionally, the participants’ postural control was evaluated using the Biodex Balance System. The correlation between Active Knee Extension Angle and Postural Control was analyzed through Spearman correlation test. No significant relationship was found between the active knee extension angles of both dominant and non-dominant legs and the postural control measurements (p &amp;gt; 0.05). The study revealed a lack of correlation between active knee extension angle and postural control among football players with hamstring muscle tightness. These findings indicate that hamstring muscle tightness may not impact postural control. Furthermore, it is observed that research involving broader and more diverse participant groups is needed to comprehensively understand this relationship.

Neuromechanical stabilisation of the centre of mass during running

BackgroundStabilisation of the centre of mass (COM) trajectory is thought to be important during running. There is emerging evidence of the importance of leg length and angle regulation during running, which could contribute to stability in the COM trajectory The present study aimed to understand if leg length and angle stabilises the vertical and anterior-posterior (AP) COM displacements, and if the stability alters with running speeds. MethodsData for this study came from an open-source treadmill running dataset (n = 28). Leg length (m) was calculated by taking the resultant distance of the two-dimensional sagittal plane leg vector (from pelvis segment to centre of pressure). Leg angle was defined by the angle subtended between the leg vector and the horizontal surface. Leg length and angle were scaled to a standard deviation of one. Uncontrolled manifold analysis (UCM) was used to provide an index of motor abundance (IMA) in the stabilisation of the vertical and AP COM displacement. ResultsIMAAP and IMAvertical were largely destabilising and always stabilising, respectively. As speed increased, the peak destabilising effect on IMAAP increased from −0.66(0.18) at 2.5 m/s to −1.12(0.18) at 4.5 m/s, and the peak stabilising effect on IMAvertical increased from 0.69 (0.19) at 2.5 m/s to 1.18 (0.18) at 4.5 m/s. ConclusionTwo simple parameters from a simple spring-mass model, leg length and angle, can explain the control behind running. The variability in leg length and angle helped stabilise the vertical COM, whilst maintaining constant running speed may rely more on inter-limb variation to adjust the horizontal COM accelerations.

Maximizing choreography and performance in artistic swimming team free routines: the role of hybrid figures

Hybrid figures serve as an important component of artistic swimming, however, no prior research has investigated objective indicators for predicting total scores in competition. This study aimed to identify significance of hybrid figure (HF) elements in predicting total scores in artistic swimming competitions and compare these variables between the Beijing team trials and international official competitions. Eight HF variables were measured in the videos from the international artistic swimming competitions, with calibration and measurement of the variables leg height index and leg angle deviation being performed by means of Kinovea. Multiple linear regression was conducted to predict the total scores based on these variables investigated for the international teams, which showed 5 significant predictors including movement frequency, leg height index, leg angle deviation, mean pattern duration, and rotation frequency. Wilcoxon signed-rank test was used to determine the differences in the variables between the Beijing team and the international teams (top 5), which showed significant difference on movement frequency, leg angle deviation, leg height index and total score. When designing hybrid figures choreography of team free routine in artistic swimming, coaches should prioritize appropriate movement frequency, pattern changes and rotations over excessively long durations. Overly complex HF choreography may lead to a decline on performance in artistic swimming competition.

Relation of leg phase angle from bioelectrical impedance analysis with voluntary and evoked contractile properties of the plantar flexors

Introduction: Bioelectrical impedance analysis (BIA) can noninvasively and quickly assess electrical properties of the body, such as the phase angle. Phase angle is regarded as the quantity and/or quality of skeletal muscle and is associated with exercise performance, such as jump height and walking speed. Although the phase angle derived from BIA is assumed to be a useful way to assess muscle function, the relationship between the phase angle and neuromuscular properties has not been fully investigated. The purpose of this study was to investigate the association of phase angle with voluntary and evoked contractile properties in 60 adults (age, 21–83 years; 30 females and 30 males).Methods: The phase angle of the right leg at 50 kHz was evaluated using BIA. The twitch contractile properties (peak twitch torque [PTtwitch], rate of twitch torque development [RTDtwitch], and time-to-PTtwitch [TPTtwitch]) of the plantar flexors were measured using tibial nerve electrical stimulation. Maximal voluntary isometric contractions (MVICs) were performed to measure the maximal muscle strength and explosive muscle strength, from which the peak MVIC torque (PTMVIC) and rate of torque development (RTD) over a time interval of 0–200 ms were assessed, respectively. The root mean square (RMS) values of electromyographic (EMG) activity during the PTMVIC and RTD measurements (EMG-RMSMVIC and EMG-RMSRTD, respectively) were calculated. The RTD and EMG-RMSRTD were normalized using PTMVIC and EMG-RMSMVIC, respectively.Results and discussion: Phase angle significantly correlated with twitch contractile properties (|r| ≥ 0.444, p &amp;lt; 0.001), PTMVIC (r = 0.532, p &amp;lt; 0.001), and RTD (r = 0.514, p &amp;lt; 0.001), but not with normalized RTD (r = 0.242, p = 0.065) or normalized EMG-RMSRTD (r = −0.055, p = 0.676). When comparing measurement variables between the low- and high-phase angle groups while controlling for sex and age effects, the high-phase angle group showed greater PTtwitch, RTDtwitch, PTMVIC, and RTD (p &amp;lt; 0.001) and shorter TPTtwitch (p &amp;lt; 0.001) but not normalized RTD (p = 0.184) or normalized EMG-RMSRTD (p = 0.317). These results suggest that the leg phase angle can be an indicator of voluntary and evoked muscle contractile properties but not the neuromuscular activity of the plantar flexors, irrespective of sex and age.

Does the ankle affect knee hyperextension during gait in hemiparetic stroke? A pilot study.

Knee hyperextension is common following stroke because of changes in joint range of motion (ROM), muscle tone and strength on the hemiparetic side. There is no clear consensus in the literature as to the cause of knee hyperextension during the stance phase of gait. Our study aimed to determine the feasibility of methods to investigate the association between ankle joint function and knee hyperextension in patients with hemiparetic stroke during the stance phase of gait. We used a cross-sectional observational study to assess bilateral ankle muscle strength using a handheld dynamometer, ROM using a digital inclinometer and muscle tone using the Modified Tardieu Scale. The knee angles of the hemiparetic leg during the stance phase of gait were assessed using the Kinovea movement analysis software. Data were analysed using the Statistical Package for the Social Sciences with significance level set at 0.05 and 95% confidence intervals. Twelve participants were included, and no alterations were necessary to the planned methodology. We found positive associations in six participants between the tibialis anterior muscle tone and the hemiparetic knee angles during heel strike, terminal stance and pre-swing phases (p < 0.05, p < 0.01 and p < 0.01, respectively). The results of the data analysis suggests that there may be a correlation between tibialis anterior muscle tone and knee hyperextension, a larger study will be imperative to confirm this association. The methods described in our pilot study are feasible for a larger study to be conducted with the recommendations considered.

Correlation between momentum and ball speed in shooting movements of female futsal players

The purpose of this study was to find a correlation between momentum and ball speed in the shooting movements of female futsal players. This study used a correlational research design. Five female futsal players (aged 19) participating in this study performed shooting movements, which were recorded on video for analysis. The shooting movements of female futsal players were analyzed based on swing movements, foot contact with the ball, and body position. Pearson correlation test was used for data analysis. The results showed that the average magnitude of momentum (impact from foot contact with the ball) was 8.14±4.68 Ns and resulted in an average ball speed of 18.51±10.63 m/s. There is a relationship between the amount of momentum and the resulting ball speed (sig &lt; 0.05). The correlation was positive, which shows the direction of a positive relationship so that the greater the momentum, the faster the ball speed. The greatest momentum is 16.49 Ns resulting in the highest ball speed of 37.48 m/s. To generate great momentum and the highest ball speed, the shooting movement is carried out with a backswing flexion angle of 106°, a kicking leg angle of 57°, and a hip and shoulder tilt angle of 14°.

Assessment of design procedures for the buckling resistance of hot-rolled steel equal leg angles under concentric and eccentric compression

This work presents an extensive advanced numerical study calibrated with recent experimental results available in the literature on the buckling behavior of hot-rolled steel angles under concentric and eccentric compression to support the ongoing revision in Europe of the design rules for angles concentrically and eccentrically loaded in compression. The numerical results were used for the assessment of existing design procedures commonly applied in practice (Eurocodes and AISC), as well as new recently proposed recommendations. In general, the current analytical rules do not present good agreement with the experimental and calibrated numerical results, even showing unsafe results for some slenderness ranges. In case of fixed members in eccentric compression, these design rules are extremely conservative, reaching ratios rN (numerical versus analytical resistances) in excess of 2. The new proposals resulting from the project ANGELHY present an improved agreement with the numerical results, showing that they may efficiently replace the current design rules in the Eurocodes. However, for concentric compression, a reliability assessment shows that the required partial factor is γM1* = 1.1.

Structural Optimization of Annular Thermoelectric Module Applied to Liquefied Natural Gas Cold Energy Recovery

The gasification of liquefied natural gas (LNG) is characterized by a substantial release of cold energy, which can be utilized for power generation via thermoelectric generator (TEG). Employing a gasifier integrated with a thermoelectric generator for LNG gasification allows for the recovery of cold energy and its conversion to useful power, a process that holds significant potential for widespread application. In the study, a thermoelectric model has been developed for an annular thermoelectric module, which formed a new category of gasifier tube. The influence of the module’s structure as well as the heat transfer parameters on the thermoelectric performance was examined. The results revealed that an optimum height of the thermoelectric leg, specifically 2 mm, maximized the output power while allowing the thermoelectric conversion efficiency to reach a peak of 3.25%. Another noteworthy finding is that an increase in the central angle of the thermoelectric leg leads to a concomitant rise in output power but a decrease in conversion efficiency. Furthermore, when the heat transfer coefficients at the hot and cold ends of the module achieved 4000 W/(m2·K) and 10,000 W/(m2·K), respectively, the conversion efficiency can be elevated to 6.98%. However, any additional enhancement in power generation performance derived from further augmenting the heat transfer is marginal. These findings can serve as a valuable reference in the design and optimization of TEG intended for the recovery of cold energy from LNG.