Search results for: second-order lateral stiffness

Authors: M. Qorbani

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Neuromuscular control of posture as understood through studies of responses to mechanical sudden acceleration automatically has been previously demonstrated in individuals with chronic ankle instability (CAI), but the presence of acute condition has not been previously explored specially in a sudden acceleration. The aim of this study was to determine neuromuscular control pattern in those with and without unilateral acute ankle sprains. Design: Case - control. Setting: University research laboratory. The sinker–card protocol with surface translation was be used as a sudden acceleration protocol with study of EMG upon 4 posture stabilizer muscles in two sides of the body in response to sudden acceleration in forward and backward directions. 20 young adult women in two groups (10 LAS; 23.9 ± 2.03 yrs and 10 normal; 26.4 ± 3.2 yrs). The data of EMG were assessed by using multivariate test and one-way repeated measures 2×2×4 ANOVA (P< 0.05). The results showed a significant muscle by direction interaction. Higher TA activity of left and right side in LAS group than normal group in forward direction significantly be showed. Higher MGR activity in normal group than LAS group in backward direction significantly showed. These findings suggest that compared two sides of the body in two directions for 4 muscles EMG activities between and within group for neuromuscular control of posture in avoiding fall. EMG activations of two sides of the body in lateral ankle sprain (LAS) patients were symmetric significantly. Acute ankle instability following once ankle sprains caused to coordinated temporal spatial patterns and strategy selection.

Keywords: neuromuscular response, sEMG, lateral ankle sprain, posture.

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Authors: Keita Nishio, Takashi Kaburagi, Yosuke Kurihara

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Recent advances in medical technology have served to enhance average life expectancy. However, the total time for which the patients are prescribed complete bedrest has also increased. With patients being required to maintain a constant lying posture- also called bedsore- development of a system to detect patient roll-over becomes imperative. For this purpose, extant studies have proposed the use of cameras, and favorable results have been reported. Continuous on-camera monitoring, however, tends to violate patient privacy. We have proposed unconstrained bio-signal measurement system that could detect body-motion during sleep and does not violate patient’s privacy. Therefore, in this study, we propose a roll-over detection method by the date obtained from the bi-signal measurement system. Signals recorded by the sensor were assumed to comprise respiration, pulse, body motion, and noise components. Compared the body-motion and respiration, pulse component, the body-motion, during roll-over, generate large vibration. Thus, analysis of the body-motion component facilitates detection of the roll-over tendency. The large vibration associated with the roll-over motion has a great effect on the Root Mean Square (RMS) value of time series of the body motion component calculated during short 10 s segments. After calculation, the RMS value during each segment was compared to a threshold value set in advance. If RMS value in any segment exceeded the threshold, corresponding data were considered to indicate occurrence of a roll-over. In order to validate the proposed method, we conducted experiment. A bi-directional microphone was adopted as a high-sensitivity pressure sensor and was placed between the mattress and bedframe. Recorded signals passed through an analog Band-pass Filter (BPF) operating over the 0.16-16 Hz bandwidth. BPF allowed the respiration, pulse, and body-motion to pass whilst removing the noise component. Output from BPF was A/D converted with the sampling frequency 100Hz, and the measurement time was 480 seconds. The number of subjects and data corresponded to 5 and 10, respectively. Subjects laid on a mattress in the supine position. During data measurement, subjects—upon the investigator's instruction—were asked to roll over into four different positions—supine to left lateral, left lateral to prone, prone to right lateral, and right lateral to supine. Recorded data was divided into 48 segments with 10 s intervals, and the corresponding RMS value for each segment was calculated. The system was evaluated by the accuracy between the investigator’s instruction and the detected segment. As the result, an accuracy of 100% was achieved. While reviewing the time series of recorded data, segments indicating roll-over tendencies were observed to demonstrate a large amplitude. However, clear differences between decubitus and the roll-over motion could not be confirmed. Extant researches possessed a disadvantage in terms of patient privacy. The proposed study, however, demonstrates more precise detection of patient roll-over tendencies without violating their privacy. As a future prospect, decubitus estimation before and after roll-over could be attempted. Since in this paper, we could not confirm the clear differences between decubitus and the roll-over motion, future studies could be based on utilization of the respiration and pulse components.

Keywords: bedsore, high-sensitivity pressure sensor, roll-over, unconstrained bio-signal measurement

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Authors: Naeim Akbari Shahkhosravi, Reza Kakavand, Helen M. S. Davies, Amin Komeili

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Equine locomotion and performance are significantly affected by hoof health. One of the most critical diseases of the hoof is laminitis, which can lead to horse lameness in a severe condition. This disease exhibits the mechanical properties degradation of the laminar junction tissue within the hoof. Therefore, it is essential to investigate the biomechanics of the hoof, focusing specifically on excessive and cumulatively accumulated stresses within the laminar junction tissue. For this aim, the current study generated a novel equine hoof Finite Element (FE) model under dynamic physiological loading conditions and employing a hyperelastic material model. Associated tissues of the equine hoof were segmented from computed tomography scans of an equine forelimb, including the navicular bone, third phalanx, sole, frog, laminar junction, digital cushion, and medial- dorsal- lateral wall areas. The inner tissues were connected based on the hoof anatomy, and the hoof was under a dynamic loading over cyclic strides at the trot. The strain distribution on the hoof wall of the model was compared with the published in vivo strain measurements to validate the model. Then the validated model was used to study the development of laminitis. The ultimate stress tolerated by the laminar junction before rupture was considered as a stress threshold. The tissue damage was simulated through iterative reduction of the tissue’s mechanical properties in the presence of excessive maximum principal stresses. The findings of this investigation revealed how damage initiates from the medial and lateral sides of the tissue and propagates through the hoof dorsal area.

Keywords: horse hoof, laminitis, finite element model, continuous damage

Procedia PDF Downloads 159

Authors: Abdolrasoul Daneshjoo

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Introduction: Soccer is a game which draws more attention in different countries especially in Brazil. Kicking among different skills in soccer and soccer players is an excellent role for the success and preference of a team. The way of point gaining in this game is passing the ball over the goal lines which are gained by shoot skill in attack time and or during the penalty kicks.Regarding the above assumption, identifying the effective factors in instep kicking in different distances shoot with maximum force and high accuracy or pass and penalty kick, may assist the coaches and players in raising qualitative level of performing the skill. Purpose: The aim of the present study was to study of a few kinematical parameters in instep kicking from 3 and 5 meter distance among the male and female elite soccer players. Methods: 24 right dominant lower limb subjects (12 males and 12 females) among Tehran elite soccer players with average and the standard deviation (22.5 ± 1.5) & (22.08± 1.31) years, height of (179.5 ± 5.81) & (164.3 ± 4.09) cm, weight of (69.66 ± 4.09) & (53.16 ± 3.51) kg, %BMI (21.06 ± .731) & (19.67 ± .709), having playing history of (4 ± .73) & (3.08 ± .66) years respectively participated in this study. They had at least two years of continuous playing experience in Tehran soccer league.For sampling player's kick; Kinemetrix Motion analysis with three cameras with 500 Hz was used. Five reflective markers were placed laterally on the kicking leg over anatomical points (the iliac crest, major trochanter, lateral epicondyle of femur, lateral malleolus, and lateral aspect of distal head of the fifth metatarsus). Instep kick was filmed, with one step approach and 30 to 45 degrees angle from stationary ball. Three kicks were filmed, one kick selected for further analyses. Using Kinemetrix 3D motion analysis software, the position of the markers was analyzed. Descriptive statistics were used to describe the mean and standard deviation, while the analysis of variance, and independent t-test (P < 0.05) were used to compare the kinematic parameters between two genders. Results and Discussion: Among the evaluated parameters, the knee acceleration, the thigh angular velocity, the angle of knee proportionately showed significant relationship with consequence of kick. While company performance on 5m in 2 genders, significant differences were observed in internal – external displacement of toe, ankle, hip and the velocity of toe, ankle and the acceleration of toe and the angular velocity of pelvic, thigh and before time contact. Significant differences showed the internal – external displacement of toe, the ankle, the knee and the hip, the iliac crest and the velocity of toe, the ankle and acceleration of ankle and angular velocity of the pelvic and the knee.

Keywords: biomechanics, kinematics, soccer, instep kick, male, female

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Authors: Kevin Giraldo, Juan A. Gallego, Uriel Zapata, Fanny L. Casado

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Compliant mechanisms are designed to deform in a controlled manner in response to external forces, utilizing the flexibility of their components to store potential elastic energy during deformation, gradually releasing it upon returning to its original form. This article explores the design of a knee orthosis intended to assist users during stand-up motion. The orthosis makes use of a compliant mechanism to balance the user’s weight, thereby minimizing the strain on leg muscles during standup motion. The primary function of the compliant mechanism is to store and exchange potential energy, so when coupled with the gravitational potential of the user, the total potential energy variation is minimized. The design process for the semi-rigid knee orthosis involved material selection and the development of a numerical model for the compliant mechanism seen as a spring. Geometric properties are obtained through the numerical modeling of the spring once the desired stiffness and safety factor values have been attained. Subsequently, a 3D finite element analysis was conducted. The study demonstrates a strong correlation between the maximum stress in the mathematical model (250.22 MPa) and the simulation (239.8 MPa), with a 4.16% error. Both analyses safety factors: 1.02 for the mathematical approach and 1.1 for the simulation, with a consistent 7.84% margin of error. The spring’s stiffness, calculated at 90.82 Nm/rad analytically and 85.71 Nm/rad in the simulation, exhibits a 5.62% difference. These results suggest significant potential for the proposed device in assisting patients with knee orthopedic restrictions, contributing to ongoing efforts in advancing the understanding and treatment of knee osteoarthritis.

Keywords: biomechanics, complaint mechanisms, gonarthrosis, orthoses.

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Authors: Sophie Mills, Constantinos Aristotelous, Leila L. Touil, Richard C. W. James

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Objectives: Historical studies of the anatomy of the spinal accessory nerve (SAN) have reported conflicting results regarding its relationship with the internal jugular vein (IJV). A literature review was undertaken to establish the prevalence of anatomical variations of the SAN encountered during routine neck dissection surgery in order to increase awareness and reduce morbidity associated with iatrogenic SAN injury. Materials and Methods: The largest systematic review to date was performed using PRISMA-ScR guidelines, which yielded nine articles following the application of inclusion and exclusion criteria. A case report is also included, which demonstrates the rare anatomical relationship of the SAN traversing a fenestrated IJV, seen for the first time in the senior author’s career. Results: The mean number of dissections per study was 119, of which 55.6% (n=5) studies were performed on cadaver subjects, and 44.4% (n=4) were surgical dissections. Incidences of the SAN lateral to the IJV and medial to the IJV ranged from 38.9%-95.7% and 2.8%-57.4%, respectively. Over half of the studies reported incidences of the SAN traversing the IJV in 0.9%-2.8% of dissections. One study reported an isolated variant of the SAN dividing around the IJV with a prevalence of 0.5%. Conclusion: At the level of the posterior belly of the digastric muscle, the surgeon can anticipate the identification of the SAN lateral to the IJV in approximately three-quarters of cases, whilst around one-quarter are estimated to be medial. A mean of 1.6% of SANs traverses a fenestration of the vein. It is essential for surgeons to be aware of these anatomical variations and their prevalence to prevent injury to vital structures during surgery.

Keywords: anatomical variant, internal jugular vein, neck dissection, spinal accessory nerve

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Authors: Florim Grajcevci, Flamur Grajcevci, Fatos Tahiri, Hamdi Kurteshi

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The territory of Kosova is actually included in one of the most seismic-prone regions in Europe. Therefore, the earthquakes are not so rare in Kosova; and when they occurred, the consequences have been rather destructive. The importance of assessing the seismic resistance of existing masonry structures has drawn strong and growing interest in the recent years. Engineering included those of Vulnerability, Loss of Buildings and Risk assessment, are also of a particular interest. This is due to the fact that this rapidly developing field is related to great impact of earthquakes on the socioeconomic life in seismic-prone areas, as Kosova and Prishtina are, too. Such work paper for Prishtina city may serve as a real basis for possible interventions in historic buildings as are museums, mosques, old residential buildings, in order to adequately strengthen and/or repair them, by reducing the seismic risk within acceptable limits. The procedures of the vulnerability assessment of building structures have concentrated on structural system, capacity, and the shape of layout and response parameters. These parameters will provide expected performance of the very important existing building structures on the vulnerability and the overall behavior during the earthquake excitations. The structural systems of existing historical buildings in Pristina, Kosovo, are dominantly unreinforced brick or stone masonry with very high risk potential from the expected earthquakes in the region. Therefore, statistical analysis based on the observed damage-deformation, cracks, deflections and critical building elements, would provide more reliable and accurate results for the regional assessments. The analytical technique was used to develop a preliminary evaluation methodology for assessing seismic vulnerability of the respective structures. One of the main objectives is also to identify the buildings that are highly vulnerable to damage caused from inadequate seismic performance-response. Hence, the damage scores obtained from the derived vulnerability functions will be used to categorize the evaluated buildings as “stabile”, “intermediate”, and “unstable”. The vulnerability functions are generated based on the basic damage inducing parameters, namely number of stories (S), lateral stiffness (LS), capacity curve of total building structure (CCBS), interstory drift (IS) and overhang ratio (OR).

Keywords: vulnerability, ductility, seismic microzone, ductility, energy efficiency

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Authors: Ching-Yi Huang, Pi-Fen Cheng, Hui-Zhu Chen, Shi Ting Huang, Heng-Hua Wang

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This is a case of oral cancer after extensive resection and modified right lateral neck lymph node dissection followed by reconstruction with a skin flap. The nursing period lasted From September 25 to October 3, 2017, through observation, interview, physical assessment, and medical record review, the author identified the following nursing problems: acute pain, impaired oral mucous membrane, and body image change. During the nursing period, the author provided individual and overall nursing care and established mutual trust through the use of empathy. Author listened and eased the patient's physical indisposition, such as wound pain, we use medications and acupuncture massage to relieve pain. However, for oral mucosa change caused by surgery, provide continuous and complete oral care and oral exercise training to improve oral mucosal healing and restore swallowing function. In the body-image changes, guided him to express his feeling after the body-image change, and enhanced support and from the family, and encouraged him to attend head and neck cancer survivor alliance which allowed the patient to accept the altered body image and reaffirm self-worth. Hopefully, through sharing this nursing experience will help to the nursing care quality of nursing care for oral cancer patients after extensive resection and modified right lateral neck lymph node dissection followed by reconstruction with a skin flap.

Keywords: oral cancer, acute pain, impaired oral mucous membrane, body image change

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Authors: Sanjai Sureshkumar, Sathish G. Kumar, P. V. V. Sathyanarayana

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For e-gear drivetrain, the transmission error and the resulting variation in mesh stiffness is one of the main source of excitation in High performance Electric Vehicle. These vibrations are transferred through the shaft to the bearings and then to the e-Gear drive housing eventually radiating noise. A parametrical model developed in 1-D system simulation by optimizing the micro and macro geometry along with bearing properties and oil filtration to achieve least transmission error and high contact ratio. Histogram analysis is performed to condense the actual road load data into condensed duty cycle to find the bearing forces. The structural vibration generated by these forces will be simulated in a nonlinear solver obtaining the normal surface velocity of the housing and the results will be carried forward to Acoustic software wherein a virtual environment of the surrounding (actual testing scenario) with accurate microphone position will be maintained to predict the sound pressure level of radiated noise and directivity plot of the e-Gear Drive. Order analysis will be carried out to find the root cause of the vibration and whine noise. Broadband spectrum will be checked to find the rattle noise source. Further, with the available results, the design will be optimized, and the next loop of simulation will be performed to build a best e-Gear Drive on NVH aspect. Structural analysis will be also carried out to check the robustness of the e-Gear Drive.

Keywords: 1-D system simulation, contact ratio, e-Gear, mesh stiffness, micro and macro geometry, transmission error, radiated noise, NVH

Procedia PDF Downloads 135

Authors: Sa`ad M. Ismail, Hung-Hsun Yen, Christina M. Murray, Helen M. S. Davies

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The lumbosacral junction (where the 7th lumbar vertebra (L7) articulates with the sacrum) is a clinically important area in the dog. The 7th lumbar vertebra (L7) is normally shorter than other lumbar vertebrae, and it has been reported that variations in the L7 length may be associated with other abnormal anatomical findings. These variations included the reduction or absence of the portion of the median sacral crest. In this study, 53 greyhound cadavers were placed in right lateral recumbency, and two lateral radiographs were taken of the lumbosacral region for each greyhound. The length of the 6th lumbar (L6) vertebra and L7 were measured using radiographic measurement software and was defined to be the mean of three lines drawn from the caudal to the cranial edge of the L6 and L7 vertebrae (a dorsal, middle, and ventral line) between specific landmarks. Sacrocaudal fusion was found in 41.5% of the greyhounds. The mean values of the length of L6, L7, and the ratio of the L6/L7 length of the greyhounds with sacrocaudal fusion were all greater than those with standard sacrums (three sacral vertebrae). There was a significant difference (P < 0.05) in the mean values of the length of L7 between the greyhounds without sacrocaudal fusion (mean = 29.64, SD ± 2.07) and those with sacrocaudal fusion (mean = 30.86, SD ± 1.80), but, there was no significant difference in the mean value of the length of the L6 measurement. Among different types of sacrocaudal fusion, the longest L7 was found in greyhounds with sacrum type D, intermediate length in those with sacrum type B, and the shortest was found in those with sacrums type C, and the mean values of the ratio of the L6/L7 were 1.11 (SD ± 0.043), 1.15, (SD ± 0.025), and 1.15 (SD ± 0.011) for the types B, C, and D respectively. No significant differences in the mean values of the length of L6 or L7 were found among the different types of sacrocaudal fusion. The occurrence of sacrocaudal fusion might affect direct anatomically connected structures such as the L7. The variation in the length of L7 between greyhounds with sacrocaudal fusion and those without may reflect the possible sequences of the process of fusion. Variations in the length of the L7 vertebra in greyhounds may be associated with the occurrence of sacrocaudal fusion. The variation in the vertebral length may affect the alignment and biomechanical properties of the sacrum and may alter the loading. We concluded that any variations in the sacrum anatomical features might change the function of the sacrum or the surrounding anatomical structures.

Keywords: biomechanics, Greyhound, sacrocaudal fusion, locomotion, 6th Lumbar (L6) Vertebra, 7th Lumbar (L7) Vertebra, ratio of the L6/L7 length

Procedia PDF Downloads 342

Authors: Alexandros Lioulemes, Michail Theofanidis, Varun Kanal, Konstantinos Tsiakas, Maher Abujelala, Chris Collander, William B. Townsend, Angie Boisselle, Fillia Makedon

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This paper presents a home-based robot-rehabilitation instrument, called ”MAGNI Dynamics”, that utilized a vision-based kinematic/dynamic module and an adaptive haptic feedback controller. The system is expected to provide personalized rehabilitation by adjusting its resistive and supportive behavior according to a fuzzy intelligence controller that acts as an inference system, which correlates the user’s performance to different stiffness factors. The vision module uses the Kinect’s skeletal tracking to monitor the user’s effort in an unobtrusive and safe way, by estimating the torque that affects the user’s arm. The system’s torque estimations are justified by capturing electromyographic data from primitive hand motions (Shoulder Abduction and Shoulder Forward Flexion). Moreover, we present and analyze how the Barrett WAM generates a force-field with a haptic controller to support or challenge the users. Experiments show that by shifting the proportional value, that corresponds to different stiffness factors of the haptic path, can potentially help the user to improve his/her motor skills. Finally, potential areas for future research are discussed, that address how a rehabilitation robotic framework may include multisensing data, to improve the user’s recovery process.

Keywords: human-robot interaction, kinect, kinematics, dynamics, haptic control, rehabilitation robotics, artificial intelligence

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Authors: Wahab Abdul Ghafar, Tao Zhong, Baba Kalan Enamullah

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Steel plate shear walls (SPSWs) are a robust lateral load resistance structure because of their high flexibility and efficient energy dissipation when subjected to seismic loads. This research investigates the seismic Performance of an innovative infill web strip (IWS-SPSW) and a typical unstiffened steel plate shear wall (USPSW). As a result, two 1:3 scale specimens of an IWS-SPSW and USPSW with a single story and a single bay were built and subjected to a cyclic lateral loading methodology. In the prototype, the beam-to-column connections were accomplished with the assistance of semi-rigid end-plate connectors. IWS-SPSW demonstrated exceptional ductility and shear load-bearing capacity during the testing process, with no cracks or other damage occurring. In addition, the IWS-SPSW could effectively dissipate energy without causing a significant amount of beam-column connection distortion. The shear load-bearing capacity of the USPSW was exceptional. However, it exhibited low ductility, severe infill plate corner ripping, and huge infill web plate cracks. The FE models were created and then confirmed using the experimental data. It has been demonstrated that the infill web strips of an SPSW system can affect the system's high Performance and total energy dissipation. In addition, a parametric analysis was carried out to evaluate the material qualities of the IWS, which can considerably improve the system's seismic performances. These properties include the steel's strength as well as its thickness.

Keywords: steel shear walls, seismic performance, failure mode, hysteresis response, nonlinear finite element analysis, parametric study.

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Authors: Cai J. T. Ladd, Mollie F. Duggan-Edwards, Tjeerd J. Bouma, Jordi F. Pages, Martin W. Skov

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Salt marshes are valued for their role in coastal flood protection, carbon storage, and for supporting biodiverse ecosystems. As a biogeomorphic landscape, marshes evolve through the complex interactions between sea level rise, sediment supply and wave/current forcing, as well as and socio-economic factors. Climate change and direct human modification could lead to a global decline marsh extent if left unchecked. Whilst the processes of saltmarsh erosion and expansion are well understood, empirical evidence on the key drivers of long-term lateral marsh dynamics is lacking. In a GIS, saltmarsh areal extent in 25 estuaries across Great Britain was calculated from historical maps and aerial photographs, at intervals of approximately 30 years between 1846 and 2016. Data on the key perceived drivers of lateral marsh change (namely sea level rise rates, suspended sediment concentration, bedload sediment flux rates, and frequency of both river flood and storm events) were collated from national monitoring centres. Continuous datasets did not extend beyond 1970, therefore predictor variables that best explained rate change of marsh extent between 1970 and 2016 was calculated using a Partial Least Squares Regression model. Information about the spread of Spartina anglica (an invasive marsh plant responsible for marsh expansion around the globe) and coastal engineering works that may have impacted on marsh extent, were also recorded from historical documents and their impacts assessed on long-term, large-scale marsh extent change. Results showed that salt marshes in the northern regions of Great Britain expanded an average of 2.0 ha/yr, whilst marshes in the south eroded an average of -5.3 ha/yr. Spartina invasion and coastal engineering works could not explain these trends since a trend of either expansion or erosion preceded these events. Results from the Partial Least Squares Regression model indicated that the rate of relative sea level rise (RSLR) and availability of suspended sediment concentration (SSC) best explained the patterns of marsh change. RSLR increased from 1.6 to 2.8 mm/yr, as SSC decreased from 404.2 to 78.56 mg/l along the north-to-south gradient of Great Britain, resulting in the shift from marsh expansion to erosion. Regional differences in RSLR and SSC are due to isostatic rebound since deglaciation, and tidal amplitudes respectively. Marshes exposed to low RSLR and high SSC likely leads to sediment accumulation at the coast suitable for colonisation by marsh plants and thus lateral expansion. In contrast, high RSLR with are likely not offset deposition under low SSC, thus average water depth at the marsh edge increases, allowing larger wind-waves to trigger marsh erosion. Current global declines in sediment flux to the coast are likely to diminish the resilience of salt marshes to RSLR. Monitoring and managing suspended sediment supply is not common-place, but may be critical to mitigating coastal impacts from climate change.

Keywords: lateral saltmarsh dynamics, sea level rise, sediment supply, wave forcing

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Authors: Fang Liu, Jia Jia Yao, Guan Lin Wu, Ren Jie Liu, Zhuang Guo

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Leveraging plasma-assisted molecular beam epitaxy (PA-MBE) on c-plane free-standing GaN substrates, this work demonstrates high-performance AlN/GaN double-barrier resonant tunneling diodes (RTDs) featuring stable and repeatable negative differential resistance (NDR) characteristics at room temperature. By scaling down the barrier thickness of AlN and the lateral mesa size of collector, a record peak current density of 1551 kA/cm2 is achieved, accompanied by a peak-to-valley current ratio (PVCR) of 1.24. This can be attributed to the reduced resonant tunneling time under thinner AlN barrier and the suppressed external incoherent valley current by reducing the dislocation number contained in the RTD device with the smaller size of collector. Statistical analysis of the NDR performance of RTD devices with different AlN barrier thicknesses reveals that, as the AlN barrier thickness decreases from 1.5 nm to 1.25 nm, the average peak current density increases from 145.7 kA/cm2 to 1215.1 kA/cm2, while the average PVCR decreases from 1.45 to 1.1, and the peak voltage drops from 6.89 V to 5.49 V. The peak current density obtained in this work represents the highest value reported for nitride-based RTDs to date, while maintaining a high PVCR value simultaneously. This illustrates that an ultra-scaled RTD based on a vertical quantum-well structure and lateral collector size is a valuable approach for the development of nitride-based RTDs with excellent NDR characteristics, revealing their great potential applications in high-frequency oscillation sources and high-speed switch circuits.

Keywords: GaN resonant tunneling diode, peak current density, peak-to-valley current ratio, negative differential resistance

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Authors: Amir Abbas Fatemi, Zahra Tabrizian, Kabir Sadeghi

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To find the location and severity of damage that occurs in a structure, characteristics changes in dynamic and static can be used. The non-destructive techniques are more common, economic, and reliable to detect the global or local damages in structures. This paper presents a non-destructive method in structural damage detection and assessment using GA and static data. Thus, a set of static forces is applied to some of degrees of freedom and the static responses (displacements) are measured at another set of DOFs. An analytical model of the truss structure is developed based on the available specification and the properties derived from static data. The damages in structure produce changes to its stiffness so this method used to determine damage based on change in the structural stiffness parameter. Changes in the static response which structural damage caused choose to produce some simultaneous equations. Genetic Algorithms are powerful tools for solving large optimization problems. Optimization is considered to minimize objective function involve difference between the static load vector of damaged and healthy structure. Several scenarios defined for damage detection (single scenario and multiple scenarios). The static damage identification methods have many advantages, but some difficulties still exist. So it is important to achieve the best damage identification and if the best result is obtained it means that the method is Reliable. This strategy is applied to a plane truss. This method is used for a plane truss. Numerical results demonstrate the ability of this method in detecting damage in given structures. Also figures show damage detections in multiple damage scenarios have really efficient answer. Even existence of noise in the measurements doesn’t reduce the accuracy of damage detections method in these structures.

Keywords: damage detection, finite element method, static data, non-destructive, genetic algorithm

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Authors: Somya R. Patro, Arnab Banerjee, G. V. Ramana

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A flexural beam carrying elastically mounted concentrated masses, such as engines, motors, oscillators, or vibration absorbers, is often encountered in mechanical, civil, and aeronautical engineering domains. To prevent resonance conditions, the designers must predict the natural frequencies of such a constrained beam system. This paper investigates experimental and analytical studies on vibration suppression in a cantilever beam with a tip mass with the help of spring-mass to achieve local resonance conditions. The system consists of a 3D printed polylactic acid (PLA) beam screwed at the base plate of the shaker system. The top of the free end is connected by an accelerometer which also acts as a tip mass. A spring and a mass are attached at the bottom to replicate the mechanism of the spring-mass resonator. The Fast Fourier Transform (FFT) algorithm converts time acceleration plots into frequency amplitude plots from which transmittance is calculated as a function of the excitation frequency. The mathematical formulation is based on the transfer matrix method, and the governing differential equations are based on Euler Bernoulli's beam theory. The experimental results are successfully validated with the analytical results, providing us essential confidence in our proposed methodology. The beam spring-mass system is then converted to an equivalent two-degree of freedom system, from which frequency response function is obtained. The H2 optimization technique is also used to obtain the closed-form expression of optimum spring stiffness, which shows the influence of spring stiffness on the system's natural frequency and vibration response.

Keywords: euler bernoulli beam theory, fast fourier transform, natural frequencies, polylactic acid, transmittance, vibration absorbers

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Authors: Rafael Muñoz, Juan Melchor, Alicia Valera, Laura Peralta, Guillermo Rus

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A torsional piezoelectric ultrasonic transducer design is proposed to measure shear moduli in soft tissue with direct access availability, using shear wave elastography technique. The measurement of shear moduli of tissues is a challenging problem, mainly derived from a) the difficulty of isolating a pure shear wave, given the interference of multiple waves of different types (P, S, even guided) emitted by the transducers and reflected in geometric boundaries, and b) the highly attenuating nature of soft tissular materials. An immediate application, overcoming these drawbacks, is the measurement of changes in cervix stiffness to estimate the gestational age at delivery. The design has been optimized using a finite element model (FEM) and a semi-analytical estimator of the probability of detection (POD) to determine a suitable geometry, materials and generated waves. The technique is based on the time of flight measurement between emitter and receiver, to infer shear wave velocity. Current research is centered in prototype testing and validation. The geometric optimization of the transducer was able to annihilate the compressional wave emission, generating a quite pure shear torsional wave. Currently, mechanical and electromagnetic coupling between emitter and receiver signals are being the research focus. Conclusions: the design overcomes the main described problems. The almost pure shear torsional wave along with the short time of flight avoids the possibility of multiple wave interference. This short propagation distance reduce the effect of attenuation, and allow the emission of very low energies assuring a good biological security for human use.

Keywords: cervix ripening, preterm birth, shear modulus, shear wave elastography, soft tissue, torsional wave

Procedia PDF Downloads 330

Authors: Oluwatoyin Joseph Gbadeyan, Sarp Adali, Bright Glen, Bruce Sithole

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Sodium lauryl surfactant concentration optimization, for nanoparticle production, provided the platform for advanced research studies. Different concentrations (0.05 %, 0.1 %, and 0.2 %) of sodium lauryl surfactant was added to snail shells powder during milling processes for producing CaCO3 at smaller particle size. Epoxy nanocomposites prepared at filler content 2 wt.% synthesized with different volumes of sodium lauryl surfactant were fabricated using a conventional resin casting method. Mechanical properties such as tensile strength, stiffness, and hardness of prepared nanocomposites was investigated to determine the effect of sodium lauryl surfactant concentration on nanocomposite properties. It was observed that the loading of the synthesized nano-calcium carbonate improved the mechanical properties of neat epoxy at lower concentrations of sodium lauryl surfactant 0.05 %. Meaningfully, loading of achatina fulica snail shell nanoparticles manufactures, with small concentrations of sodium lauryl surfactant 0.05 %, increased the neat epoxy tensile strength by 26%, stiffness by 55%, and hardness by 38%. Homogeneous dispersion facilitated, by the addition of sodium lauryl surfactant during milling processes, improved mechanical properties. Research evidence suggests that nano-CaCO3, synthesized from achatina fulica snail shell, possesses suitable reinforcement properties that can be used for nanocomposite fabrication. The evidence showed that adding small concentrations of sodium lauryl surfactant 0.05 %, improved dispersion of nanoparticles in polymetrix material that provided mechanical properties improvement.

Keywords: sodium lauryl surfactant, mechanical properties , achatina fulica snail shel, calcium carbonate nanopowder

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Authors: Pahirangan Sivapatham, , Esser Barbara

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The impacts of the asphalt mix design, the properties of aggregates and quality differences in the same type of bitumen, as well as the dosage rate of reclaimed asphalt on the relevant material parameter of the analytical pavement design method are not known. Due to that, in this study, the influence of the above mentioned characteristics on relevant material parameters has been determined and analyzed by means of the analytical pavement calculations method. Therefore, material parameters for several asphalt mixes for asphalt wearing course, asphalt binder course and asphalt base course have been determined. Thereby several bitumens of the same type from different producer’s have been used. In addition, asphalt base course materials with three different dosages of reclaimed asphalt have been produced and tested. As material parameter according to the German analytical pavement design guide(RDO Asphalt), the stiffness’s at different temperatures and fatigue behavior have been determined. The findings of asphalt base course materials produced with several pen graded bitumen from different producers and different dosages of reclaimed asphalt indicate the distinct impact on fatigue behaviors and mechanical properties. The calculated test results of the analytical pavement design method show significant differences in the lifetimes. The pavement design calculation is to carry out by means of the actual material parameter. The calculated lifetime of the asphalt base course materials differentiates by the factor 3.2. The determining test results of bitumen characteristics meet the requirement according to the German Standards. But, further investigations of bitumen in different aging conditions show significant differences in their quality. The fatigue behavior and stiffness of asphalt pavement improves with increasing dosage of reclaimed asphalt. Furthermore, the type of aggregates used shows no significant influences.

Keywords: reclaimed asphalt pavement, quality differences in the bitumen, life time calculation, Asphalt mix with RAP

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Authors: Spyridon Komaitis, Christos Koutsarnakis, Evangelos Drosos, Aristotelis Kalyvas

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This study opts to investigate the intrinsic architecture, morphology, and spatial relationship of the subcortical pathways implicated in the connectivity of the motor/premotor cortex and SMA/pre-SMA complex. Twenty normal, adult, formalin-fixed cerebral hemispheres were explored through the fiber micro-dissection technique. Lateral to medial and medial to lateral dissections focused on the area of interest were performed in a tandem manner and under the surgical microscope. We traced the subcortical architecture, spatial relationships, and axonal connectivity of four major pathways: a) the dorsal component of the SLF (SLF-I) was found to reside in the medial aspect of the hemisphere and seen to connect the precuneus with the SMA and pre-SMA complex, b) the frontal longitudinal system (FLS) was consistently encountered as the natural anterior continuation of the SLF-II and SLF-III and connected the premotor and prefrontal cortices c) the fronto-caudate tract (FCT), a fan-shaped tract, was documented to participate in connectivity of the prefrontal and premotor cortices to the head and body of the caudate nucleus and d) the cortico-tegmental tract(CTT) was invariably recorded to subserve the connectivity of the tegmental area with the fronto-parietal cortex. No hemispheric asymmetries were recorded for any of the implicated pathways. Sub-segmentation systems were also proposed for each of the aforementioned tracts. The structural connectivity and functional specialization of motor and premotor areas in the human brain remain vague to this day as most of the available evidence derives either from animal or tractographic studies. By using the fiber-microdissection technique as our main method of investigation, we provide sound structural evidence on the delicate anatomy of the related white matter pathways.

Keywords: neuroanatomy, premotor, motor, connectivity

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Authors: E. Faizan, Wahab Abdul Ghafar, Tao Zhong

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Steel plate shear walls (SPSWs) are a robust lateral load resistance structure because of their high flexibility and efficient energy dissipation when subjected to seismic loads. This research investigates the seismic performance of an innovative infill web strip (IWS-SPSW) and a typical unstiffened steel plate shear wall (USPSW). As a result, two 1:3 scale specimens of an IWS-SPSW and USPSW with a single story and a single bay were built and subjected to a cyclic lateral loading methodology. In the prototype, the beam-to-column connections were accomplished with the assistance of semi-rigid end-plate connectors. IWS-SPSW demonstrated exceptional ductility and shear load-bearing capacity during the testing process, with no cracks or other damage occurring. In addition, the IWS-SPSW could effectively dissipate energy without causing a significant amount of beam-column connection distortion. The shear load-bearing capacity of the USPSW was exceptional. However, it exhibited low ductility, severe infill plate corner ripping, and huge infill web plate cracks. The FE models were created and then confirmed using the experimental data. It has been demonstrated that the infill web strips of an SPSW system can affect the system's high performance and total energy dissipation. In addition, a parametric analysis was carried out to evaluate the material qualities of the IWS, which can considerably improve the system's seismic performances. These properties include the steel's strength as well as its thickness.

Keywords: steel shear walls, seismic performance, failure mode, hysteresis response, nonlinear finite element analysis, parametric study

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Authors: Ilya Simanovskii

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Nonlinear convective flows developed under the joint action of buoyant and thermo-capillary effects in a two-layer system with periodic boundary conditions on the lateral walls have been investigated. The influence of an interfacial heat release on oscillatory regimes has been studied. The computational regions with different lengths have been considered. It is shown that the development of oscillatory instability can lead to the appearance of different no steady flows.

Keywords: interface, instabilities, two-layer systems, bioinformatics, biomedicine

Procedia PDF Downloads 385

Authors: Akram Khelaifia, Salah Guettala, Nesreddine Djafar Henni, Rachid Chebili

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Reinforced concrete shear walls are pivotal in protecting buildings from seismic forces by providing strength and stiffness. This study highlights the importance of strategically placing shear walls and optimizing the shear wall-to-floor area ratio in building design. Nonlinear analyses were conducted on an eight-story building situated in a high seismic zone, exploring various scenarios of shear wall positioning and ratios to floor area. Employing the performance-based seismic design (PBSD) approach, the study aims to meet acceptance criteria such as inter-story drift ratio and damage levels. The results indicate that concentrating shear walls in the middle of the structure during the design phase yields superior performance compared to peripheral distributions. Utilizing shear walls that fully infill the frame and adopting compound shapes (e.g., Box, U, and L) enhances reliability in terms of inter-story drift. Conversely, the absence of complete shear walls within the frame leads to decreased stiffness and degradation of shorter beams. Increasing the shear wall-to-floor area ratio in building design enhances structural rigidity and reliability regarding inter-story drift, facilitating the attainment of desired performance levels. The study suggests that a shear wall ratio of 1.0% is necessary to meet validation criteria for inter-story drift and structural damage, as exceeding this percentage leads to excessive performance levels, proving uneconomical as structural elements operate near the elastic range.

Keywords: nonlinear analyses, pushover analysis, shear wall, plastic hinge, performance level

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Authors: Erik Vassøy Olsen, Hirpa G. Lemu

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Inspired by the Formula-1 competition, IMechE (Institute of Mechanical Engineers) and Formula SAE (Society of Mechanical Engineers) organize annual competitions for University and College students worldwide to compete with a single-seat race car they have designed and built. The design of the chassis or the frame is a key component of the competition because the weight and stiffness properties are directly related with the performance of the car and the safety of the driver. In addition, a reduced weight of the chassis has a direct influence on the design of other components in the car. Among others, it improves the power to weight ratio and the aerodynamic performance. As the power output of the engine or the battery installed in the car is limited to 80 kW, increasing the power to weight ratio demands reduction of the weight of the chassis, which represents the major part of the weight of the car. In order to reduce the weight of the car, ION Racing team from the University of Stavanger, Norway, opted for a monocoque design. To ensure fulfilment of the above-mentioned requirements of the chassis, the monocoque design should provide sufficient torsional stiffness and absorb the impact energy in case of a possible collision. The study reported in this article is based on the requirements for Formula Student competition. As part of this study, diverse mechanical tests were conducted to determine the mechanical properties and performances of the monocoque design. Upon a comprehensive theoretical study of the mechanical properties of sandwich composite materials and the requirements of monocoque design in the competition rules, diverse tests were conducted including 3-point bending test, perimeter shear test and test for absorbed energy. The test panels were homemade and prepared with an equivalent size of the side impact zone of the monocoque, i.e. 275 mm x 500 mm so that the obtained results from the tests can be representative. Different layups of the test panels with identical core material and the same number of layers of carbon fibre were tested and compared. Influence of the core material thickness was also studied. Furthermore, analytical calculations and numerical analysis were conducted to check compliance to the stated rules for Structural Equivalency with steel grade SAE/AISI 1010. The test results were also compared with calculated results with respect to bending and torsional stiffness, energy absorption, buckling, etc. The obtained results demonstrate that the material composition and strength of the composite material selected for the monocoque design has equivalent structural properties as a welded frame and thus comply with the competition requirements. The developed analytical calculation algorithms and relations will be useful for future monocoque designs with different lay-ups and compositions.

Keywords: composite material, Formula student, ION racing, monocoque design, structural equivalence

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Authors: Keda Li, Hong Hu

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Auxetic materials, as an emerging artificial designed metamaterial has attracted growing attention due to their promising negative Poisson’s ratio behaviors and tunable properties. The conventional auxetic lattice structures for which the deformation process is governed by a bending-dominated mechanism have faced the limitation of poor mechanical performance for many potential engineering applications. Recently, both load-bearing and energy absorption capabilities have become a crucial consideration in auxetic structure design. This study reports the finite element analysis of a class of hexagonal double-arrowhead auxetic structures with enhanced stiffness and energy absorption performance. The structure design was developed by extending the traditional double-arrowhead honeycomb to a hexagon frame, the stretching-dominated deformation mechanism was determined according to Maxwell’s stability criterion. The finite element (FE) models of 2D lattice structures established with stainless steel material were analyzed in ABAQUS/Standard for predicting in-plane structural deformation mechanism, failure process, and compressive elastic properties. Based on the computational simulation, the parametric analysis was studied to investigate the effect of the structural parameters on Poisson’s ratio and mechanical properties. The geometrical optimization was then implemented to achieve the optimal Poisson’s ratio for the maximum specific energy absorption. In addition, the optimized 2D lattice structure was correspondingly converted into a 3D geometry configuration by using the orthogonally splicing method. The numerical results of 2D and 3D structures under compressive quasi-static loading conditions were compared separately with the traditional double-arrowhead re-entrant honeycomb in terms of specific Young's moduli, Poisson's ratios, and specified energy absorption. As a result, the energy absorption capability and stiffness are significantly reinforced with a wide range of Poisson’s ratio compared to traditional double-arrowhead re-entrant honeycomb. The auxetic behaviors, energy absorption capability, and yield strength of the proposed structure are adjustable with different combinations of joint angle, struts thickness, and the length-width ratio of the representative unit cell. The numerical prediction in this study suggests the proposed concept of hexagonal double-arrowhead structure could be a suitable candidate for the energy absorption applications with a constant request of load-bearing capacity. For future research, experimental analysis is required for the validation of the numerical simulation.

Keywords: auxetic, energy absorption capacity, finite element analysis, negative Poisson's ratio, re-entrant hexagonal honeycomb

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Authors: Stepanov Ivan, Musalimov Viktor, Monahov Uriy

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This report examines the current state of human gait simulator development based on the human hip joint model. This unit will create a database of human gait types, useful for setting up and calibrating mechano devices, as well as the creation of new systems of rehabilitation, exoskeletons and walking robots. The system has ample opportunity to configure the dimensions and stiffness, while maintaining relative simplicity.

Keywords: hip joint, human gait, physiotherapy, simulation

Procedia PDF Downloads 383

Authors: Nonde Lushinga, Jiang Xin, Danstan Chiponde, Lawrence P. Mutale

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In this paper, falling weight deflectometer (FWD) was used to determine the bonding condition of a newly constructed semi-rigid base pavement. Using Evercal back-calculation computer programme, it was possible to quickly and accurately determine the structural condition of the pavement system of FWD test data. The bonding condition of the pavement layers was determined from calculated shear stresses and strains (relative horizontal displacements) on the interface of pavement layers from BISAR 3.0 pavement computer programmes. Thus, by using non-linear layered elastic theory, a pavement structure is analysed in the same way as other civil engineering structures. From non-destructive FWD testing, the required bonding condition of pavement layers was quantified from soundly based principles of Goodman’s constitutive models shown in equation 2, thereby producing the shear reaction modulus (Ks) which gives an indication of bonding state of pavement layers. Furthermore, a Tack coat failure Ratio (TFR) which has long being used in the USA in pavement evaluation was also used in the study in order to give validity to the study. According to research [39], the interface between two asphalt layers is determined by use of Tack Coat failure Ratio (TFR) which is the ratio of the stiffness of top layer asphalt layers over the stiffness of the second asphalt layer (E1/E2) in a slipped pavement. TFR gives an indication of the strength of the tack coat which is the main determinants of interlayer slipping. The criteria is that if the interface was in the state full bond, TFR would be greater or equals to 1 and that if the TFR was 0, meant full slip. Results of the calculations showed that TFR value was 1.81 which re-affirmed the position that the pavement under study was in the state of full bond because the value was greater than 1. It was concluded that FWD can be used to determine bonding condition of existing and newly constructed pavements.

Keywords: falling weight deflectometer (FWD), backcaluclation, semi-rigid base pavement, shear reaction modulus

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Authors: Sif J. Friis, Mette Poulsen, Torben Strom Hansen, Peter Herskind, Jens V. Nygaard

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Gastric biomechanics governs a large range of scientific and engineering fields, from gastric health issues to interaction mechanisms between external devices and the tissue. Determination of mechanical properties of the stomach is, thus, crucial, both for understanding gastric pathologies as well as for the development of medical concepts and device designs. Although the field of gastric biomechanics is emerging, advances within medical devices interacting with the gastric tissue could greatly benefit from an increased understanding of tissue anisotropy and heterogeneity. Thus, in this study, uniaxial tensile tests of gastric tissue were executed in order to study biomechanical properties within the same individual as well as across individuals. With biomechanical tests in the strain domain, tissue from the antrum region of six porcine stomachs was tested using eight samples from each stomach (n = 48). The samples were cut so that they followed dominant fiber orientations. Accordingly, from each stomach, four samples were longitudinally oriented, and four samples were circumferentially oriented. A step-wise stress relaxation test with five incremental steps up to 25 % strain with 200 s rest periods for each step was performed, followed by a 25 % strain ramp test with three different strain rates. Theoretical analysis of the data provided stress-strain/time curves as well as 20 material parameters (e.g., stiffness coefficients, dissipative energy densities, and relaxation time coefficients) used for statistical comparisons between samples from the same stomach as well as in between stomachs. Results showed that, for the 20 material parameters, heterogeneity across individuals, when extracting samples from the same area, was in the same order of variation as the samples within the same stomach. For samples from the same stomach, the mean deviation percentage for all 20 parameters was 21 % and 18 % for longitudinal and circumferential orientations, compared to 25 % and 19 %, respectively, for samples across individuals. This observation was also supported by a nonparametric one-way ANOVA analysis, where results showed that the 20 material parameters from each of the six stomachs came from the same distribution with a level of statistical significance of P > 0.05. Direction-dependency was also examined, and it was found that the maximum stress for longitudinal samples was significantly higher than for circumferential samples. However, there were no significant differences in the 20 material parameters, with the exception of the equilibrium stiffness coefficient (P = 0.0039) and two other stiffness coefficients found from the relaxation tests (P = 0.0065, 0.0374). Nor did the stomach tissue show any significant differences between the three strain-rates used in the ramp test. Heterogeneity within the same region has not been examined earlier, yet, the importance of the sampling area has been demonstrated in this study. All material parameters found are essential to understand the passive mechanics of the stomach and may be used for mathematical and computational modeling. Additionally, an extension of the protocol used may be relevant for compiling a comparative study between the human stomach and the pig stomach.

Keywords: antrum region, gastric biomechanics, loading-unloading, stress relaxation, uniaxial tensile testing

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Authors: Sofie Verstraete, Stijn Debruyne, Frederik Desplentere

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Considering environmental issues, the interest to apply sustainable materials in industry increases. Specifically for composites, there is an emerging need for suitable materials and bonding techniques. As an alternative to traditional composites, short bio-fiber (cellulose-based flax) reinforced Polylactic Acid (PLA) is gaining popularity. However, these thermoplastic based composites show issues in adhesive bonding. This research focusses on analyzing the effects of the fibers near the bonding interphase. The research applies injection molded plate structures. A first important parameter concerns the fiber volume fraction, which directly affects adhesion characteristics of the surface. This parameter is varied between 0 (pure PLA) and 30%. Next to fiber volume fraction, the orientation of fibers near the bonding surface governs the adhesion characteristics of the injection molded parts. This parameter is not directly controlled in this work, but its effects are analyzed. Surface roughness also greatly determines surface wettability, thus adhesion. Therefore, this research work considers three different roughness conditions. Different mechanical treatments yield values up to 0.5 mm. In this preliminary research, only one adhesive type is considered. This is a two-part epoxy which is cured at 23 °C for 48 hours. In order to assure a dedicated parametric study, simple and reproduceable adhesive bonds are manufactured. Both single lap (substrate width 25 mm, thickness 3 mm, overlap length 10 mm) and double lap tests are considered since these are well documented and quite straightforward to conduct. These tests are conducted for the different substrate and surface conditions. Dog bone tensile testing is applied to retrieve the stiffness and strength characteristics of the substrates (with different fiber volume fractions). Numerical modelling (non-linear FEA) relates the effects of the considered parameters on the stiffness and strength of the different joints, obtained through the abovementioned tests. Ongoing work deals with developing dedicated numerical models, incorporating the different considered adhesion parameters. Although this work is the start of an extensive research project on the bonding characteristics of thermoplastic bio-fiber reinforced composites, some interesting results are already prominent. Firstly, a clear correlation between the surface roughness and the wettability of the substrates is observed. Given the adhesive type (and viscosity), it is noticed that an increase in surface energy is proportional to the surface roughness, to some extent. This becomes more pronounced when fiber volume fraction increases. Secondly, ultimate bond strength (single lap) also increases with increasing fiber volume fraction. On a macroscopic level, this confirms the positive effect of fibers near the adhesive bond line.

Keywords: adhesive bonding, bio-fiber reinforced composite, flax fibers, lap joint

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Authors: Nirmala Lama

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The construction of high dams has led to significant challenges in managing flow rates discharging over spillways, resulting in cavitation damages on hydraulic surfaces. To address this, aerator devices were designed and installed to promote fore aeration, thereby controlling and mitigating damages caused by cavitation. Consequently, these aerator types, three-dimensional aerators (3DAEs), have demonstrated superior efficiency in introducing forced air into the flow.This research focuses on the installation and evaluation of three-dimensional aerator devices at the high discharge spillway surface. In the laboratory, the air concentration downstream of the hydraulic structures was extensively measured, and the data were analyzed in details.Multiple flow scenarios and structural arrangements of the aerators were adopted for the study. The outcomes of these experiments are listed as In terms of air concentration value, the comparison between 3 DAE (three-dimensional aerator) with offset only and offset with ramp reveals significant differences. The concentration value on the side wall was justified. The side cavity length was found to increase with higher approach Froude numbers and lateral enlargement widths. Furthermore, 3DAE exhibited shorter side cavity lengths compared to three-dimensional aerator devices without ramps (3DAD), a beneficial features for controlling water fins. An empirical formula to express the side cavity length was derived from the measured data. Also, the comparison were made on the basis of water fin formation between the different arrangements of 3D aerators. In conclusion, this research provides valuable insights into the performance of three-dimensional aerators in mitigating cavitation damages and controlling water fins in high dam spillways. The findings offer practical implications for designers and engineers seeking to enhance the efficiency and safety of hydraulic structures subjected to high flow rates.

Keywords: three-dimension aerator, cavity, water fin, air entrainment

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