Kutatói szeminárium 2022
Az előadássorozat angol nyelvű.
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Date: |
30th March 2022, 13:15 |
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Title: |
Local and dynamic algorithms for analysing graph models of systems |
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Presenter: |
Tursunbai Kyzy Yrysgul |
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Supervisor: |
Dr. Gábor Farkas |
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Abstract |
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The presentation deals with problems from the field of graph theory, carried out at the Institute of Informatics Systems of the Russian Academy of Sciences. A new fully dynamic algorithm for the recognition and representation of a family of chordal and split graphs is presented, where for the first time the addition and removal of a complete r-vertex graph Kr serve as the modifications performed on the graph. Parallel local algorithms are developed for coloring w-perfect graphs, for T-colorings, and summing the colorings of graphs. A local asynchronous algorithm is proposed for finding the center and median of a graph in networks of arbitrary topology. |
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Date: |
6th April, 2022, 13:15 |
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Title: |
The influence of heel height on strain variation of plantar fascia during high heel shoes walking- combined musculoskeletal modelling and finite element analysis |
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Presenter: |
Meizi Wang |
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Supervisor: |
Dr. Gusztáv Fekete |
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Abstract |
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The repetitive tension caused by high heel shoes (HHS) wearing resulting in plantar fasciitis is a high-risk disease in HHS individuals who suffer heel and plantar pain. To explore the biomechanical function on plantar fascia under HHS conditions, in this study, musculoskeletal modelling (MsM) and finite element method (FEM) were used to investigate the effect of heel height on strain distribution of plantar fascia. Three-dimensional (3D) and one-dimensional (1D) finite element models of plantar fascia were generated to analyse the computed strain variation in 3, 5, and 7 cm of heel heights. Results showed that the peak strain of plantar fascia was progressively increased on both 3D and 1D plantar fascia as heel elevated from 3cm to 7cm, and the maximum strain of plantar fascia occurs near the heel pain site at second peak stance. 3D fascia model predicted a higher strain magnitude than that of 1D and provided a more reliable strain distribution on the plantar fascia. It is concluded that HHS with narrow heel support could pose a high risk on plantar fasciitis development, rather than reducing symptoms. |
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Date: |
13th April 2022, 13:15 |
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Title: |
Study of deformation in cold-rolled aluminum sheets |
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Presenter: |
János György Bátorfi |
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Supervisor: |
Prof. Dr. Jurij Sidor, DSc |
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Abstract |
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In the study, we have modeled the behavior of Al alloys during cold rolling by Finite Element Model. We have summarized the applicable simplifications of the method. For simulating the process, a material model was employed based on experimental measurements. The results of the experimental observations and the inbuilt material models were compared, and the simulation was conducted for symmetric and asymmetric rolling. A comparison of simulated and experimental data allowed us to evaluate the friction coefficient. A relationship was determined between the minimum friction coefficient necessary for rolling and determined ones. The method was used for calculating the following components of strain: normal, shear and equivalent. As a further step, the Finite Element Model was employed for determining the wear of the rolls. By comparing the measurements and simulations, we can conclude, that the FEM can be successfully applied for the simulation of cold rolling with high accuracy. |
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Date: |
20th April, 2022, 13:15 |
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Title: |
Experimental and comparative study of the single and double pass solar water heating system by using heat enhancer and thermal storage medium |
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Presenter: |
Khargotra Rohit |
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Supervisor: |
Dr. Tej Singh |
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Abstract |
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The aim of this research work is to investigate the performance of the double-pass solar water heating system (DPSWH) by using the heat enhancer and thermal storage medium. The impact of mass flow rate on output temperature, thermal efficiency, and overall efficiency was also investigated. The experiment would be performed at varying the mass flow rates of water from 9:00 a.m. to 4:00 p.m. at an interval of 30 min. Moreover, the performance of the double-pass solar water would also be compared with the single-pass solar water heating system and their results also compared to see which one has the better thermal performance. |
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Date: |
27th April, 2022, 13:15 |
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Title: |
Aerodynamics of wind turbine blade sections under icing conditions |
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Presenter: |
Ibrahim Kipngeno Rotich |
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Supervisor: |
Prof. Dr. László Kollár |
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Abstract |
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Energy demand has been on the rise with an increase in population during winter seasons with wind power being optimal due to air pressure difference from temperature reduction. Ice accretion on wind turbines worsens performance by increasing drag and reducing lift which significantly reduces power production up to 80% and can cause stall of wind turbine1, micro-cracking and delamination, structural engineering failure and lifespan reduction2. The objective of the study is to determine the optimal aerodynamic performance of a bare and accreted wind turbine airfoil used in convectional power produced and aim at reducing ice accretion and mechanical failures (delamination) due to icing and widen operating conditions of wind turbine. The data will be obtained from airfoil tool will be simulated on the ANSYS software (ANSYS CFX and FENSAP ICE) to determine aerodynamic performance on bare blade and icing (freezing rain-droplets) on wind turbine blade and comparison of aerodynamic performance on bare and iced surface. The parameters that will be considered includes the LWC, density, angle of attack and free stream velocity. Ice accretion on wind turbine blade has previously been studied under adverse weather conditions with zero angle of attack (AoA), with varying LWC and free stream velocity3. However, this study proposes to address the problem with varying angle of attack and air densities and how it can affect the aerodynamic performance (lift and drag coefficients).
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Date: |
4th May, 2022, 13:15 |
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Title: |
Lower limb kinetic comparisons between the chasse step and one step footwork during stroke play in table tennis |
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Presenter: |
He Yuqi |
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Supervisor: |
Dr. Gusztáv Fekete |
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Abstract |
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Biomechanical footwork research during table tennis performance has been the subject of much interest players and exercise scientists. The purpose of this study was to investigate the lower limb kinetic characteristics of the chasse step and one step footwork during stroke play using traditional discrete analysis and one-dimensional statistical parameter mapping. Twelve national level one table tennis players (Height: 172 ± 3.80 cm, Weight: 69 ± 6.22 kg, Age: 22 ± 1.66 years, Experience: 11 ± 1.71 year) from Ningbo University volunteered to participate in the study. The kinetic data of the dominant leg during the chasse step and one step backward phase (BP) and forward phase (FP) was recorded by instrumented insole systems and a force platform. Paired sample T tests were used to analyze maximum plantar force, peak pressure of each plantar region, the force time integral and the pressure time integral. For SPM analysis, the plantar force time series curves were marked as a 100% process. A paired-samples T-test in MATLAB was used to analyze differences in plantar force. One step produced a greater plantar force than the chasse step during 6.92– 11.22% BP (P = 0.039). The chasse step produced a greater plantar force than one step during 53.47–99.01% BP (P < 0.001). During the FP, the chasse step showed a greater plantar force than the one step in 21.06–84.06% (P < 0.001). The one step produced a higher maximum plantar force in the BP (P = 0.032) and a lower maximum plantar force in the FP (P = 0) compared with the chasse step. The one step produced greater peak pressure in the medial rearfoot (P = 0) , lateral rearfoot (P = 0) and lateral forefoot (P = 0.042) regions than the chasse step during BP. In FP, the chasse step showed a greater peak pressure in the Toe (P = 0) than the one step. The one step had a lower force time integral (P = 0) and greater pressure time integral (P = 0) than the chasse step in BP, and the chasse step produced a greater force time integral (P = 0) and pressure time integral (P = 0.001) than the one step in the FP. The findings indicate that athletes can enhance plantarflexion function resulting in greater weight transfer, facilitating a greater momentum during the 21.06– 84.06% of FP. This is in addition to reducing the load on the dominant leg during landing by utilizing a buffering strategy. Further to this, consideration is needed to enhance the cushioning capacity of the sole heel and the stiffness of the toe area. |
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Date: |
11th May, 2022, 13:15 |
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Title: |
Effects of Running Fatigue on Lower Extremity Symmetry among Amateur Runners From a Biomechanical Perspective |
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Presenter: |
Gao Zixiang |
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Supervisor: |
Dr. Gusztáv Fekete |
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Abstract |
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Fatigue caused by running alters the postural control ability and the symmetry of bilateral limbs, while asymmetry is associated with a higher risk of injury. The objective of this study was to reveal the effects of running fatigue on the symmetry of lower limb dynamics and kinematics parameters. Eighteen male amateur runners participated in this study. The marker trajectories and ground reaction forces were collected via an 8-camera VICON and Kistler 3D force platform before and after the running-induced fatigue protocol. Symmetry angles (SA) of joint moments, range of motions (ROM), and joint stiffness in three planes were calculated pre- and post-fatigue. Normality tests and Paired sample T-tests were carried out to analyze the bilateral lower limb differences and SA of parameters between pre- and post-fatigue. One-dimensional statistical parameter mapping (SPM_1d) was used to compare parameters with the characteristic of one-dimensional time-varying of lower limbs. After fatigue, the extension angles of the knee joint, flexion angle, and hip joint moment increased by 17%, 12%, and 11% separately. In comparison, the flexion angle of the knee angle decreased by 5%, which was statistically different (P<0.05). SA of ankle abduction angle decreased, while the SA of knee abduction moment, ROM, and joint stiffness in the coronal plane increased. SA of hip adduction angle, ROM, and joint stiffness increased significantly, while the SA of abduction angle decreased significantly is shown on the ankle (P<0.05). The symmetry of internal rotation of three joints in the horizontal plane increased, while the SA of external rotation of the three joints decreased significantly (P<0.05). These findings provide preliminary evidence that fatigue changes lower limb symmetry in running gait and provide potential evidence for the exploration of lower limb function, athletic performance, running-related injuries, and the research and development of footwear and equipment. |
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Date: |
18th May, 2022, 13:15 |
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Title: |
Gender and leg-dominance differences in shoe properties and foot injuries in badminton |
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Presenter: |
Shen Siqin |
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Supervisor: |
Dr. Gusztáv Fekete |
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Abstract |
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Background: While the roles of injury prevention and performance enhancement have increasingly been investigated for badminton footwear, there is a lack of research on gender-specific badminton footwear. The purpose of this study was to examine the gender differences in footwear demands and foot injuries in badminton. Methods: A supervised questionnaire survey of 326 recreational badminton players was collected. The questionnaire was divided into four sections enquiring about the characteristics of (1) participant profiles, (2) importance of shoe properties (3) shoe complaints. (4) and pain or discomfort in different foot regions. The Mann-Whitney U test and Wilcoxon Signed Ranks test were performed to determine the differences between genders and the differences between leg dominance, respectively. The significance level was set at 0.05. Results: Both males and females rated shoe fit as the most important feature, followed by overall comfort, and injury protection. Females considered forefoot cushioning, comfort, breathability, and color as the more important compared with other properties, which showed distinct pattern differences from males. The shoe problem results indicated that plantar pain of the non-dominant foot was considered the most reported footwear problem by both males and females. The problem of excessive arch-support on the dominant and non-dominant sides of male participants was significantly higher than females (p < 0.05). Occasional pain or frequent pain were mainly distributed in the forefoot, followed by the rearfoot and midfoot regions. Conclusion: There were small differences in footwear demand between the dominant and non-dominant sides, but several differences existed between females and males. The results from gender differences suggested that female-specific shoes prefer a specific better fit, rather than a modified version of male shoes. In the future, the design of badminton shoes should consider footwear demands and foot discomfort profiles in respective male and female badminton players. |
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Date: |
25th May, 2022, 13:15 |
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Title: |
Effects of forefoot shoe on knee and ankle loading during running in male recreational runners |
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Presenter: |
Quan Wenjing |
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Supervisor: |
Dr. Gusztáv Fekete |
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Abstract |
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Although overuse running injury risks for the ankle and knee are high, the effect of different shoe designs on Achilles tendon force (ATF) and Patellofemoral joint contact force (PTF) loading rates are unclear. Therefore, the primary objective of this study was to compare the ATF at the ankle and the PTF and Patellofemoral joint stress force (PP) at the knee using different running shoe designs (forefoot shoes vs. normal shoes). Methods: Fourteen healthy recreational male runners were recruited to run over a force plate under two shoe conditions (forefoot shoes vs. normal shoes). Sagittal plane ankle and knee kinematics and ground reaction forces were simultaneously recorded. Ankle joint mechanics (ankle joint angle, velocity, moment and power) and the ATF were calculated. Knee joint mechanics (knee joint angle velocity, moment and power) and the PTF and PP were also calculated. Results: No significant differences were observed in the PTF, ankle plantarflexion angle, ankle dorsiflexion power, peak vertical active force, contact time and PTF between the two shoe conditions. Compared to wearing normal shoes, wearing the forefoot shoes demonstrated that the ankle dorsiflexion angle, knee flexion velocity, ankle dorsiflexion moment extension, knee extension moment, knee extension power, knee flexion power and the peak patellofemoral contact stress were significantly reduced. However, the ankle dorsiflexion velocity, ankle plantarflexion velocity, ankle plantarflexion moment and achilles tendons force increased significantly. Conclusions: These findings suggest that wearing forefoot shoes significantly decreases the patellofemoral joint stress by reducing the moment of knee extension, however the shoes increased the ankle plantarflexion moment and ATF force. The forefoot shoes effectively reduced the load on the patellofemoral joint during the stance phase of running. However, it is not recommended for new and novice runners and patients with Achilles tendon injuries to wear forefoot shoes. |
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