Search results for: external mechanical forces

Authors: Sumit Kumar, Sunil Kumar, Chandan Deep Singh

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This paper presents modeling and simulation of flexible robot in an underwater environment. The underwater environment completely contrasts with ground or space environment. The robot in an underwater situation is subjected to various dynamic forces like buoyancy forces, hydrostatic and hydrodynamic forces. The underwater robot is modeled as Rayleigh beam. The developed model further allows estimating the deflection of tip in two directions. The complete dynamics of the underwater robot is analyzed, which is the main focus of this investigation. The control of robot trajectory is not discussed in this paper. Simulation is performed using Symbol Shakti software.

Keywords: bond graph modeling, dynamics. modeling, rayleigh beam, underwater robot

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Authors: P. Vosynek, T. Návrat, M. Peč, J. Pořízka, P. Diviš

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Changes of mechanical properties and response behavior of bones is an important external sign of medical problems like osteoporosis, bone remodeling after fracture or surgery, osteointegration, or bone tissue loss of astronauts in space. Measuring of mechanical behavior of bones in physiological and osteoporotic states, quantified by different degrees of protein (collagen) and mineral loss, is thus an important topic in biomechanical research. This contribution deals with the relation between mechanical properties of the turkey long bone–tibia in physiological, demineralized, and deproteinized state. Three methods for comparison were used: densitometry, three point bending and harmonic response analysis. The results help to find correlations between the methods and estimate their possible application in medical practice.

Keywords: bone properties, long bone, osteoporosis, response behavior

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Authors: Khaled Ali Soltan

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Iran can be considered a triangle that is affected by 3 forces: the government, the elite, and the people. Over the last 100 years, these three forces have been at odds with each other. This lack of coordination and sometimes antagonism among these three forces has led to lawlessness in Iran (both the government and the people have entered the cycle of lawlessness) and the spread of destructive processes in the country and the destruction of resources, both natural and human resources. The direct and negative impact of this issue on people's lives as well as the environment highlights the importance of this article. This article descriptively deals with the issue and suggests solutions and examines possible problems and obstacles. There seems to be a way to establish a connection’ closeness and coordination among these three forces and put them on the path of development. ELITE RAIN is a scientific-popular process that can create coordination and cooperation between these forces, prevent destructive processes in the country and put it on the path of sustainable development and a better life. This solution is a more advanced model of brainstorming technique introduced by Alex Osborn in 1953. Given that people have tried different types of protests to improve the status quo, such as the change of government in 1979 which led to the establishment of the theocracy, participating in elections that resulted in more frustration and corruption due to the lack of real parties, and sporadic street protests that resulted in nothing more than repression, it seems that this solution can be successful.

Keywords: corruption, destruction of resources, elite rain, Iran, legal complaints, sustainable development, the elite

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Authors: W. I. Mazyan, A. Ahmadi, M. Hoorfar

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Objectives/Scope: This paper proposes a mathematical model for calculating the solid-gas separation efficiency in cyclones. This model provides better agreement with experimental results compared to existing mathematical models. Methods: The separation ratio efficiency, ϵsp, is evaluated by calculating the outlet to inlet count ratio. Similar to mathematical derivations in the literature, the inlet and outlet particle count were evaluated based on Eulerian approach. The model also includes the external forces acting on the particle (i.e., centrifugal and drag forces). In addition, the proposed model evaluates the exact length that the particle travels inside the cyclone for the evaluation of number of turns inside the cyclone. The separation efficiency model derivation using Stoke’s law considers the effect of the inlet tangential velocity on the separation performance. In cyclones, the inlet velocity is a very important factor in determining the performance of the cyclone separation. Therefore, the proposed model provides accurate estimation of actual cyclone separation efficiency. Results/Observations/Conclusion: The separation ratio efficiency, ϵsp, is studied to evaluate the performance of the cyclone for particles ranging from 1 microns to 10 microns. The proposed model is compared with the results in the literature. It is shown that the proposed mathematical model indicates an error of 7% between its efficiency and the efficiency obtained from the experimental results for 1 micron particles. At the same time, the proposed model gives the user the flexibility to analyze the separation efficiency at different inlet velocities. Additive Information: The proposed model determines the separation efficiency accurately and could also be used to optimize the separation efficiency of cyclones at low cost through trial and error testing, through dimensional changes to enhance separation and through increasing the particle centrifugal forces. Ultimately, the proposed model provides a powerful tool to optimize and enhance existing cyclones at low cost.

Keywords: cyclone efficiency, solid-gas separation, mathematical model, models error comparison

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Authors: Peter Ugbedeojo Nelson

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Despite the tremendous advancements and knowledge acquisition around entrepreneurship orientation (EO) research, there may still be more to learn on how environmental dynamics would permute organizational processes and determine the extent to which success would be achieved. Using the contingency theory, we test a model that proposes a moderating influence of external relational capital and environmental hostility on the EO-performance effect of 423 managers/owners of small and medium scale enterprises. The hypotheses were tested using Hayes simultaneous regression, and the results showed that all EO dimensions (risk-taking, innovation, and performance) had a main effect on performance while the moderating variables interacted well with risk-taking (more than other EO dimensions) to improve performance. However, external relational capital, more than environmental hostility, influences the EO-performance relationship. Our findings highlight the differential ways that EO dimensions interact with environmental contingencies to influence performance. Further studies can examine how competitive aggressiveness and autonomy are moderated by external relational capital and environmental hostility.

Keywords: external relational capital, entrepreneurial orientation, risk-taking, innovation, proactiveness

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Authors: D. Henninger, A. Zopey, T. Ihde, C. Mehring

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The dynamic performance of a 4-way solenoid operated hydraulic spool valve has been analyzed by means of a one-dimensional modeling approach capturing flow, magnetic and fluid forces, valve inertia forces, fluid compressibility, and damping. Increased model accuracy was achieved by analyzing the detailed three-dimensional electromagnetic behavior of the solenoids and flow behavior through the spool valve body for a set of relevant operating conditions, thereby allowing the accurate mapping of flow and magnetic forces on the moving valve body, in lieu of representing the respective forces by lower-order models or by means of simplistic textbook correlations. The resulting high-fidelity one-dimensional model provided the basis for specific and timely design modification eliminating experimentally observed valve oscillations.

Keywords: dynamic performance model, high-fidelity model, 1D-3D decoupled analysis, solenoid-operated hydraulic servo valve, CFD and electromagnetic FEA

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Authors: Saltanat Zhilkibayeva, Muratulla Utenov, Nurzhan Utenov

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The distributed inertia forces of complex nature appear in links of rod mechanisms within the motion process. Such loads raise a number of problems, as the problems of destruction caused by a large force of inertia; elastic deformation of the mechanism can be considerable, that can bring the mechanism out of action. In this work, a new analytical approach for the definition of internal forces in links of robotic systems and mechanisms with statically indeterminate and determinate structures taking into account the distributed inertial and concentrated forces is proposed. The relations between the intensity of distributed inertia forces and link weight with geometrical, physical and kinematic characteristics are determined in this work. The distribution laws of inertia forces and dead weight make it possible at each position of links to deduce the laws of distribution of internal forces along the axis of the link, in which loads are found at any point of the link. The approximation matrixes of forces of an element under the action of distributed inertia loads with the trapezoidal intensity are defined. The obtained approximation matrixes establish the dependence between the force vector in any cross-section of the element and the force vector in calculated cross-sections, as well as allow defining the physical characteristics of the element, i.e., compliance matrix of discrete elements. Hence, the compliance matrixes of an element under the action of distributed inertial loads of trapezoidal shape along the axis of the element are determined. The internal loads of each continual link are unambiguously determined by a set of internal loads in its separate cross-sections and by the approximation matrixes. Therefore, the task is reduced to the calculation of internal forces in a final number of cross-sections of elements. Consequently, it leads to a discrete model of elastic calculation of links of rod mechanisms. The discrete model of the elements of mechanisms and robotic systems and their discrete model as a whole are constructed. The dynamic equilibrium equations for the discrete model of the elements are also received in this work as well as the equilibrium equations of the pin and rigid joints expressed through required parameters of internal forces. Obtained systems of dynamic equilibrium equations are sufficient for the definition of internal forces in links of mechanisms, which structure is statically definable. For determination of internal forces of statically indeterminate mechanisms (in the way of determination of internal forces), it is necessary to build a compliance matrix for the entire discrete model of the rod mechanism, that is reached in this work. As a result by means of developed technique the programs in the MAPLE18 system are made and animations of the motion of the fourth class mechanisms of statically determinate and statically indeterminate structures with construction on links the intensity of cross and axial distributed inertial loads, the bending moments, cross and axial forces, depending on kinematic characteristics of links are obtained.

Keywords: distributed inertial forces, internal forces, statically determinate mechanisms, statically indeterminate mechanisms

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Authors: Marinete Araujo da Silva Fobister

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This presentation aims to discuss how the feeling of ‘nostalgia’ both present on Westerns and migrants could shed light to a mutual recognition and an exchange of ways of life that could enhance mutual possibilities of self-realization. It seems that this feeling of nostalgia is related to another unfolding of the nihilism of the death of God diagnosed by Nietzsche. Westerns are feeling on the margins of the values of their own culture as they feel such values as external to them. At the same time, some groups are claiming the return of the old devalued values. In this scenario, the West is receiving many migrants from different parts of the world since the second half of the last century. Migrants might be suffering from nostalgia or homesickness for having left their home. It might be that sharing a sense of nostalgia, although with different meanings, can bring together Westerns and migrants. Migrants bring ways of life that might be unknown and inexperienced in the West, and these can shed light to new forms of interpretation and cultivation of ones’ drives, and forces and this could become a source of mutual strength cultivation. Therefore, this mutual feeling of nostalgia could lead to ways of exploring the idea of self- realization in Nietzsche detaching it from the idea of being mainly individual to a more trans-individual-cultural claim. Nietzsche argues that nihilism is a European event here translated as a Western event, which would take 200 years until it could be overcome. To overcome nihilism a new kind of human would be needed, a creative and strong kind. For Nietzsche, there is not a fixed or true self, hence one possibility for one to achieve self-realization would reside on cultivating their multiple creative forces. The argument here is that in this recent unfolding of nihilism, translated in the sense of nostalgia, the encounter between the mainstream western immersed on nihilism with migrants could create a sense of a shared temporary home, where these different ways of life could inspire each other to create new meanings. Indeed, contributing to the expansion of one’s world view, drives and forces. Therefore, fertilizing the soil for the cultivation of self-realization and consequently the creation of new values.

Keywords: migration, nihilism, nostalgia, self-realization

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Authors: Wheyming Song, Ssu-Ping Lin

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The primary advantage of package-on-package (PoP) packaging is that since it has less volume, it weighs less. But this is also related to its principal drawback, which is warpage. This research investigates how PoP package warpage patterns are affected by assembling process parameters, including substrate temperature, injection speed, injection temperature, and compound forces. We also investigate how warpage patterns are affected by the location of the silicon chip. The methodologies used in this research are design of experiment and warpage simulation via ANSYS. We propose a regression model to predict the warpage value as a function of substrate temperature, injection speed, injection temperature, and compound forces. Our results show that interaction effects exist between substrate temperature and compound forces and between injection speed and injection temperature. Therefore, determining the optimal values for substrate temperature, compound forces, injection speed, and injection temperature cannot be done individually. Also, our results show that the warpage patterns based on the location of silicon chips can be classified into 11 groups, with the largest warpage occurring at the left-most and right-most sides.

Keywords: package-on-package, warpage, design of experiment, simulation

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Authors: Jingde Li, Hong Hao

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Recent oil and gas accidents have reminded us the severe consequences of gas explosion on structure damage and financial loss. In order to protect the structures and personnel, engineers and researchers have been working on numerous different explosion mitigation methods. Amongst, venting is the most economical approach to mitigate gas explosion overpressure. In this paper, venting is used as the overpressure alleviation method. A theoretical method and a numerical technique are presented to predict the internal and external pressure from vented gas explosion in a large enclosure. Under idealized conditions, a number of experiments are used to calibrate the accuracy of the theoretically calculated data. A good agreement between the theoretical results and experimental data is seen. However, for realistic scenarios, the theoretical method over-estimates internal pressures and is incapable of predicting external pressures. Therefore, a CFD simulation procedure is proposed in this study to estimate both the internal and external overpressure from a large-scale vented explosion. Satisfactory agreement between CFD simulation results and experimental data is achieved.

Keywords: vented gas explosion, internal pressure, external pressure, CFD simulation, FLACS, ANSYS Fluent

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Authors: D. Chronopoulos, I. Antoniadis, V. Spitas, D. Koulocheris, V. Polenta

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A concept of a simple linear oscillator, incorporating a negative stiffness element is demonstrated to exhibit extraordinary damping properties. This oscillator shares the same overall (static) stiffness, the same mass and the same damping element with a reference classical linear SDOF oscillator. However, it differs from the original SDOF oscillator by appropriately redistributing the component spring stiffness elements and by re-allocating the damping element. Despite the fact that the proposed oscillator incorporates a negative stiffness element, it is designed to be both statically and dynamically stable. Once such an oscillator is optimally designed, it is shown to exhibit an extraordinary apparent damping ratio, which is even several orders of magnitude higher than that of the original SDOF system, especially in cases where the original damping of the SDOF system is low. This damping behavior is not a result of a novel additional extraordinary energy dissipation mechanism, but a result of the phase difference between the positive and the negative stiffness elastic forces, which is in turn a consequence of the proper re-distribution of the stiffness and the damper elements. This fact ensures that an adequate level of elastic forces exists throughout the entire frequency range, able to counteract the inertial and the excitation forces. Next, Acoustic or Phononic Meta-materials are considered, in which one atom is replaced by the concept of the above simple linear oscillator. The results indicate that not only the damping of the meta-material verifies and exceeds the one expected from the so-called "meta-damping" behavior, but also that the band gap of the meta-material can be significantly increased.

Keywords: wave propagation, periodic structures, wave damping, mechanical engineering

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Authors: A. Abdel-Moniem, H. Madkour, K. Farah, A. Abdullah

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The reduction in dapped end beams depth nearby the supports tends to produce stress concentration and hence results in shear cracks, if it does not have an adequate reinforcement detailing. This study investigates numerically the efficiency of applying different external strengthening techniques to the dapped end of such beams. A two-dimensional finite element model was built to predict the structural behavior of dapped ends strengthened with different techniques. The techniques included external bonding of the steel angle at the re-entrant corner, un-bounded bolt anchoring, external steel plate jacketing, exterior carbon fiber wrapping and/or stripping and external inclined steel plates. The FE analysis results are then presented in terms of the ultimate load capacities, load-deflection and crack pattern at failure. The results showed that the FE model, at various stages, was found to be comparable to the available test data. Moreover, it enabled the capture of the failure progress, with acceptable accuracy, which is very difficult in a laboratory test.

Keywords: dapped-end beams, finite element, shear failure, strengthening techniques, reinforced concrete, numerical investigation

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Authors: N. V. Klassen, A. A. Vasin, A. M. Likhter, K. A. Voronin, A. V. Mariasevskaya, I. M. Shmit’ko

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Regular patterning in mixtures of bio-polymers (chitosan and collagen) and nanoparticles in water suspensions has been found by means of optical microscopy. The patterning was created either by external electrical field of moderate amplitude (200–1000 v/cm) or spontaneously. Simultaneously with the patterning pushing out of water drops mixed with nanoparticles to the external regions was observed. These phenomena are explained by interactions of charged bio-polymers and nanoparticles with external and internal electrical fields as well as with the regions of decreased dielectrical permittivity surrounding nano-objects in water which possesses anomalously high dielectrical permittivity. Electrical charges of opposite signs of the nano-objects induce their mutual attraction whereas dipole moments created around these nano-objects by the electrical fields are pushing these particles to the regions with lower fields. Due to this reason, non-homogeneities of dielectrical permittivity around nano-objects immersed into water suspension induces mutual repulsion of the objects. This spatial decrease of this repulsion with the inter-particle distances is more sharp than that of the Coulomb attraction. So, at longer distances, the attractions are stronger whereas at shorter distances the repulsion prevails. At a certain distance these two forces compensate each other creating the equilibrium state of the mixture of nano-objects with opposite charges. When the groups of positive and negative nano-objects consist from identical particles, quasi-periodical pattern of the suspension is observed like mesoscopic two-dimensional super-crystal. These results can clarify the mechanisms of healing of internal organs with direct or alternative electrical fields.

Keywords: bio-polymers, chitosan, collagen, nanoparticles, Coulomb attraction, polarization repulsion, periodical patterning, electrical low frequency resonances

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Authors: Zhenyu Yang, Qiunan Chen, Xiaocheng Huang

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Reliable prediction of tunnel collapse remains a prominent challenge in the field of civil engineering. In this study, leveraging the nonlinear Hoek-Brown failure criterion and the upper-bound theorem, an analytical solution for the collapse surface of shallowly buried circular tunnels was derived, taking into account the coupled effects of surface loads and pore water pressures. Initially, surface loads and pore water pressures were introduced as external force factors, equating the energy dissipation rate to the external force, yielding our objective function. Subsequently, the variational method was employed for optimization, and the outcomes were juxtaposed with previous research findings. Furthermore, we utilized the deduced equation set to systematically analyze the influence of various rock mass parameters on collapse shape and extent. To validate our analytical solutions, a comparison with prior studies was executed. The corroboration underscored the efficacy of our proposed methodology, offering invaluable insights for collapse risk assessment in practical engineering applications.

Keywords: tunnel roof stability, analytical solution, hoek–brown failure criterion, limit analysis

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Authors: Hao-Su Liu, Jun-Qing Lei

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This study introduces the theory of modified particle swarm optimizer and its application in time-domain expressions for bridge self-excited aerodynamic forces. Based on the indicial function expression and the rational function expression in time-domain expression for bridge self-excited aerodynamic forces, the characteristics of the two methods, i.e. the modified particle swarm optimizer and conventional search method, are compared in flutter derivatives’ fitting process. Theoretical analysis and numerical results indicate that adopting whether the indicial function expression or the rational function expression, the fitting flutter derivatives obtained by modified particle swarm optimizer have better goodness of fit with ones obtained from experiment. As to the flutter derivatives which have higher nonlinearity, the self-excited aerodynamic forces, using the flutter derivatives obtained through modified particle swarm optimizer fitting process, are much closer to the ones simulated by the experimental. The modified particle swarm optimizer was used to recognize the parameters of time-domain expressions for flutter derivatives of an actual long-span highway-railway truss bridge with double decks at the wind attack angle of 0°, -3° and +3°. It was found that this method could solve the bounded problems of attenuation coefficient effectively in conventional search method, and had the ability of searching in unboundedly area. Accordingly, this study provides a method for engineering industry to frequently and efficiently obtain the time-domain expressions for bridge self-excited aerodynamic forces.

Keywords: time-domain expressions, bridge self-excited aerodynamic forces, modified particle swarm optimizer, long-span highway-railway truss bridge

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Authors: Megat Zuhairy, Megat Tajuddin, Hadijah Iberahim, Noraini Ismail

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This paper aims to discuss the impact of external networking on innovation and organizational performance in the construction industry. In Malaysia, the construction industry is known to be one of the industries that contribute significantly towards her economic growth. The construction industry is described as a fragmented and complex product system as construction projects implementation requires involvement of varying combination of large and small organizations across the supply chain spectrum. The innovation and performance of Malaysian construction industry are reported to be at underachieving and efforts for its improvement have inspired this study initiative. External networking among industry players is capable in bringing them to work together as a team, reducing the adversarial relationships among them for innovation effort and greater performance. The instrument in measuring innovation and organizational performance specific to the construction industry was developed by adapting measures introduced by several scholars in these fields. Contractors and consulting companies were the sampling frames of this study representing the construction industry in Malaysia. The population lists were developed from the lists provided by CIDB, BEM, BOA and BQSM. The samples were selected based on a stratified sampling method to gauge representation of the different groups in the population. Regression analysis was performed in this quantitative study to assess relationships amongst variables. The results revealed that principally, external networking is significant in influencing both innovation and organizational performance. Nevertheless, external networking with different industry players has a different impact on innovation and organizational performance. The study revealed that external networking with project players is significant on project performance but not on innovation. On the other hand, external networking with government agencies, academic institutions and professional bodies is significant in influencing innovation but not on organizational performance.

Keywords: innovation, external networking, organizational performance, construction industry

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Authors: Abdulhamit Donder, Erhan Ilhan Konukseven

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Grinding operation is performed in order to obtain desired surfaces precisely in machining process. The needed relative motion between the cutting tool and the workpiece is generally created either by the movement of the cutting tool or by the movement of the workpiece or by the movement of both of them as in our case. For all these cases, the coherence level between the movements and the interaction forces is a key influential parameter for efficient grinding. Therefore, in this work, spectral coherence analysis has been performed to investigate the coherence level between grinding interaction forces and the movement of the workpiece on our robotic-grinding experimental setup in METU Mechatronics Laboratory.

Keywords: coherence analysis, correlation, FFT, grinding, hanning window, machining, Piezo actuator, reverse arrangements test, spectral analysis

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Authors: Carlos Teodoro, Oscar Bautista

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In this work, we analyze theoretically the mass transport in a time-periodic electroosmotic flow through a parallel flat plate microchannel under different periodic functions of the applied external electric field. The microchannel connects two reservoirs having different constant concentrations of an electro-neutral solute, and the zeta potential of the microchannel walls are assumed to be uniform. The governing equations that allow determining the mass transport in the microchannel are given by the Poisson-Boltzmann equation, the modified Navier-Stokes equations, where the Debye-Hückel approximation is considered (the zeta potential is less than 25 mV), and the species conservation. These equations are nondimensionalized and four dimensionless parameters appear which control the mass transport phenomenon. In this sense, these parameters are an angular Reynolds, the Schmidt and the Péclet numbers, and an electrokinetic parameter representing the ratio of the half-height of the microchannel to the Debye length. To solve the mathematical model, first, the electric potential is determined from the Poisson-Boltzmann equation, which allows determining the electric force for various periodic functions of the external electric field expressed as Fourier series. In particular, three different excitation wave forms of the external electric field are assumed, a) sawteeth, b) step, and c) a periodic irregular functions. The periodic electric forces are substituted in the modified Navier-Stokes equations, and the hydrodynamic field is derived for each case of the electric force. From the obtained velocity fields, the species conservation equation is solved and the concentration fields are found. Numerical calculations were done by considering several binary systems where two dilute species are transported in the presence of a carrier. It is observed that there are different angular frequencies of the imposed external electric signal where the total mass transport of each species is the same, independently of the molecular diffusion coefficient. These frequencies are called crossover frequencies and are obtained graphically at the intersection when the total mass transport is plotted against the imposed frequency. The crossover frequencies are different depending on the Schmidt number, the electrokinetic parameter, the angular Reynolds number, and on the type of signal of the external electric field. It is demonstrated that the mass transport through the microchannel is strongly dependent on the modulation frequency of the applied particular alternating electric field. Possible extensions of the analysis to more complicated pulsation profiles are also outlined.

Keywords: electroosmotic flow, mass transport, oscillatory flow, species separation

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Authors: Myung Kwon Cho, Seul Ki Min, Gwang Heum Yoon, Jung Hyun Joo, Sang Jun Sim, Hwa Sung Shin

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Mechanotransduction is a mechanism that external mechanical stimulation is converted to biochemical activity in the cell. When applying this mechanism to the unicellular green algae Chlamydomonas reinhardtii, the dramatic result that the accumulation of intracellular lipid was up to 60% of dry weight basis occurred. Furthermore, various variations in cellular physiology occurred, but there is a lack of the development of the system and related research for applying that technology to control the mechanical stress and facilitate molecular analyses. In this study, applying a mechanical stress to microalgae, the microfluidic device system that finely induced direct membrane distortion of microalgae. Cellular membrane distortion led to deflagellation, calcium influx and lipid accumulation in microalgae. In conclusion, cytological studies such as mechanotransduction can be actualized by using this system and membrane distortion is a promising inducer for biodiesel production.

Keywords: mechanotransduction, microalgae, membrane distortion, biodiesel

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Authors: Daumantas Zidanavicius

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In order to investigate the bond between concrete and steel in the circular steel tube column filled with concrete, the 7 series of specimens were tested with the same geometrical parameters but different concrete properties. Two types of specimens were chosen. For the first type, the expansive additives to the concrete mixture were taken to increase internal forces. And for the second type, mechanical components were used. All 7 series of the short columns were modeled by FEM and tested experimentally. In the work, big attention was taken to the bond-slip models between steel and concrete. Results show that additives to concrete let increase the bond strength up to two times and the mechanical anchorage –up to 6 times compared to control specimens without additives and anchorage.

Keywords: concrete filled steel tube, push-out test, bond slip relationship, bond stress distribution

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Authors: Dawoon Choi, Jian Li, Yunhyun Cho

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Axial Flux Permanent Magnet (AFPM) machines have been widely used in various applications due to their important merits, such as compact structure, high efficiency and high torque density. This paper presents one of the most important characteristics in the design process of the AFPM device, which is a recent issue. To design AFPM machine, the predicting electromagnetic forces between the permanent magnets and stator is important. Because of the magnitude of electromagnetic force affects many characteristics such as machine size, noise, vibration, and quality of output power. Theoretically, this force is canceled by the equilibrium of force when it is in the middle of the gap, but it is inevitable to deviate due to manufacturing problems in actual machine. Such as large scale wind generator, because of the huge attractive force between rotor and stator disks, this is more serious in getting large power applications such as large. This paper represents the characteristics of Double-Stator Inner –Rotor AFPM machines when it has rotor eccentricity. And, unbalanced air-gap and inclined air-gap condition which is caused by rotor offset and tilt in a double-stator single inner-rotor AFPM machine are each studied in electromagnetic and mechanical aspects. The output voltage and cogging torque under un-normal air-gap condition of AF machines are firstly calculated using a combined analytical and numerical methods, followed by a structure analysis to study the effect to mechanical stress, deformation and bending forces on bearings. Results and conclusions given in this paper are instructive for the successful development of AFPM machines.

Keywords: axial flux permanent magnet machine, inclined air gap, unbalanced air gap, rotor eccentricity

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Authors: N. Musayeva, N. Rustamova, N. Bagirov, S. Ibadov

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Purpose: to analyze the long-term results of external dacryocystorhinostomy (DCR), which remains the preferred primary procedure in the surgical treatment of lacrimal duct obstruction in chronic dacryocystitis. Methodology: long-term results of external DCR (after 3 years) performed on 90 patients (90 eyes) with chronic dacryocystitis from 2018 to 2020 were evaluated. The Azerbaijan National Center of Ophthalmology, named after acad. Zarifa Aliyeva. 15 of the patients were men, 75 – women. The average age was 45±3.2 years. Surgical operations were performed under local anesthesia. All patients suffered from diabetes mellitus for more than 3 years. All patients underwent external DCR and silicone drainage (tube) was implanted. In the postoperative period (after 3 years), lacrimation, purulent discharge, and the condition of the scar at the operation site were assessed. Results: All patients were under observation for more than 18 months. In general, the effectiveness of the surgical operation was 93.34%. Recurrence of disease was observed in 6 patients and in 3 patients (3.33%), the scar at the site of the operation was rough (non-cosmetic). In 3 patients (3.33%) – the surgically formed anastomosis between the lacrimal sac and the nasal bone was obstructed by scar tissue. These patients were reoperated by trans canalicular laser DCR. Conclusion: Despite the long-term (more than a hundred years) use of external DCR, it remains one of the primary techniques in the surgery of chronic dacryocystitis. Due to the high success rate and good long-term results of DCR in the treatment of chronic dacryocystitis in patients suffering from diabetes mellitus, we recommend external DCR for this group of patients.

Keywords: chronic dacryocystitis, diabetes mellitus, external dacryocystorhinostomy, long-term results

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Authors: Abdeljalil Beniiche

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The limitation with smart contracts is that they cannot access external data that might be required to control the execution of business logic. Oracles can be used to provide external data to smart contracts. An oracle is an interface that delivers data from external data outside the blockchain to a smart contract to consume. Oracle can deliver different types of data depending on the industry and requirements. In this paper, we study and describe the widely used blockchain oracles. Then, we elaborate on his potential role, technical architecture, and design patterns. Finally, we discuss the human oracle and its key role in solving the truth problem by reaching a consensus about a certain inquiry and tasks.

Keywords: blockchain, oracles, oracles design, human oracles

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Authors: Bummo Ahn

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Palpation is widely used to measure soft tissue firmness or stiffness in the living condition in order to apply detection, diagnosis, and treatment of tumors, scar tissue, abnormal muscle tone, or muscle spasticity. Since these methods are subjective and depend on the proficiency level, it is concluded that there are other diagnoses depending on the condition of the experts and the results are not objective. The mechanical property obtained by using the elasticity of the tissue is important to calculate a predictive variable for monitoring abnormal tissues. If the mechanical load such as reaction force on the foot increases in the same region under the same conditions, the mechanical property of the tissue is changed. Therefore, objective diagnosis is possible not only for experts but also for patients using this quantitative information. Furthermore, the portable system also allows non-experts to easily diagnose at home, not in hospitals or institutions. In this paper, we introduce a portable palpation system that can be used to measure the mechanical properties of human tissue, which can be applied to monitor diabetic foot ulceration patients with measuring the mechanical property change of foot tissue. The system was designed to be smaller and portable in comparison with the conventional palpation systems. It is consists of the probe, the force sensor, linear actuator, micro control unit, the display module, battery, and housing. Using this system, we performed validation experiments by applying different palpations (3 and 5 mm) to soft tissue (silicone rubber) and measured reaction forces. In addition, we estimated the elastic moduli of the soft tissue against different palpations and compare the estimated elastic moduli that show similar value even if the palpation depths are different.

Keywords: palpation probe, portable, diabetic foot ulceration, monitoring, mechanical property

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Authors: Pei-Gi Shu, Yin-Hua Yeh, Chao-Ting Chen

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Using a dataset consisting of 7,120 firm-year observations from the Taiwan stock market over the 2007-2011 sample period, we find a significantly negative relationship between board external connectedness and firm diversification. We propose a learningeffect hypothesis indicating that an externally connected board member’s experiences in other companies directly affect his recommendations regarding the underlying firm’s diversification. The partial correlation between diversification and the performance of firms with externally connected board members is used as a proxy for the learning effect. The empirical results show that the learning effect is asymmetrically embedded in firm diversification, with negative experiences having a greater effect on firm diversification than positive experiences. Externally connected board members are associated with reduced diversification in one firm after they learn that diversification is detrimental to value in other companies. Moreover, the diversification of a firm due to board external connectedness is moderated by the controlling owner’s interest alignment and entrenchment.

Keywords: board, external, connectedness, diversification

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Authors: Bergun Meric Bingul, Cigdem Bulgan, Ozlem Tore, Mensure Aydin, Erdal Bal

Abstract:

The aim of the study was to compare the effects of impact forces and some kinematic parameters with two different straight punch stance positions in boxing. 9 elite boxing athletes from the Turkish National Team (mean age± SD 19.33±2.11 years, mean height 174.22±3.79 cm, mean weight 66.0±6.62 kg) participated in this study as voluntarily. Boxing athletes performed one trial in straight punch technique for each two different stance positions (orthodox and southpaw stances) at sandbag. The trials were recorded at a frequency of 120Hz using eight synchronized high-speed cameras (Oqus 7+), which were placed, approximately at right- angles to one another. The three-dimensional motion analysis was performed with a Motion Capture System (Qualisys, Sweden). Data was transferred to Windows-based data acquisition software, which was QTM (Qualisys Track Manager). 11 segment models were used for determination of the kinematic variables (Calf, leg, punch, upperarm, lowerarm, trunk). Also, the sandbag was markered for calculation of the impact forces. Wand calibration method (with T stick) was used for field calibration. The mean velocity and acceleration of the punch; mean acceleration of the sandbag and angles of the trunk, shoulder, hip and knee were calculated. Stance differences’ data were compared with Wilcoxon test for using SPSS 20.0 program. According to the results, there were statistically significant differences found in trunk angle on the sagittal plane (yz) (p<0.05). There was a significant difference also found in sandbag acceleration and impact forces between stance positions (p < 0.05). Boxing athletes achieved more impact forces and accelerations in orthodox stance position. It is recommended that to use an orthodox stance instead of southpaw stance in straight punch technique especially for creating more impact forces.

Keywords: boxing, impact force, kinematics, straight punch, orthodox, southpaw

Procedia PDF Downloads 294

Authors: Valery Gulyayev, Sergey Glazunov, Elena Andrusenko, Nataliya Shlyun

Abstract:

Enhancement of technology and techniques for drilling deep directed oil and gas bore-wells are of essential industrial significance because these wells make it possible to increase their productivity and output. Generally, they are used for drilling in hard and shale formations, that is why their drivage processes are followed by the emergency and failure effects. As is corroborated by practice, the principal drilling drawback occurring in drivage of long curvilinear bore-wells is conditioned by the need to obviate essential force hindrances caused by simultaneous action of the gravity, contact and friction forces. Primarily, these forces depend on the type of the technological regime, drill string stiffness, bore-hole tortuosity and its length. They can lead to the Eulerian buckling of the drill string and its sticking. To predict and exclude these states, special mathematic models and methods of computer simulation should play a dominant role. At the same time, one might note that these mechanical phenomena are very complex and only simplified approaches (‘soft string drag and torque models’) are used for their analysis. Taking into consideration that now the cost of directed wells increases essentially with complication of their geometry and enlargement of their lengths, it can be concluded that the price of mistakes of the drill string behavior simulation through the use of simplified approaches can be very high and so the problem of correct software elaboration is very urgent. This paper deals with the problem of simulating the regimes of drilling deep curvilinear bore-wells with prescribed imperfect geometrical trajectories of their axial lines. On the basis of the theory of curvilinear flexible elastic rods, methods of differential geometry, and numerical analysis methods, the 3D ‘stiff-string drag and torque model’ of the drill string bending and the appropriate software are elaborated for the simulation of the tripping in and out regimes and drilling operations. It is shown by the computer calculations that the contact and friction forces can be calculated and regulated, providing predesigned trouble-free modes of operation. The elaborated mathematic models and software can be used for the emergency situations prognostication and their exclusion at the stages of the drilling process design and realization.

Keywords: curvilinear drilling, drill string tripping in and out, contact forces, resistance forces

Procedia PDF Downloads 120

Authors: Elaf N. Mahrous, Fares Al Mushref, Turkey Al Dossary

Abstract:

An embedded particle finite element model has been developed to simulate the transient capillary forces acting on a moving contact line of spreading liquid drop on a smooth solid surface. Three common dissipative force models were tested numerically to account for the capillary effect at the solid-liquid interface. Among those models, Jiang’s model was found to be the most stable one. Our proposed numerical model was validated experimentally for a wide variety of surface wettability. A dimensionless relationship between the spreading rate and time was established, and the results showed good agreement with the experimental data.

Keywords: PFEM-embedded, Eulerian-PFEM, surface tension, capillary forces, moving contact line, non-dimensional analysis

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Authors: Chris Thurlbourne

Abstract:

Due to the continual demand for material to build, and a limit of good environmental material credentials of 'normal' building materials, there is a need to look at new and reconditioned material types - both biogenic and non-biogenic - and a field of research that accompanies this. This research development focuses on biogenic and non-biogenic material engineering and the impact of our environment on new and reconditioned material types. In our building industry and all the industries involved in constructing our built environment, building material types can be broadly categorized into two types, biogenic and non-biogenic material properties. Both play significant roles in shaping our built environment. Regardless of their properties, all material types originate from our earth, whereas many are modified through processing to provide resistance to 'forces of nature', be it rain, wind, sun, gravity, or whatever the local environmental conditions throw at us. Modifications are succumbed to offer benefits in endurance, resistance, malleability in handling (building with), and ergonomic values - in all types of building material. We assume control of all building materials through rigorous quality control specifications and regulations to ensure materials perform under specific constraints. Yet materials confront an external environment that is not controlled with live forces undetermined, and of which materials naturally act and react through weathering, patination and discoloring, promoting natural chemical reactions such as rusting. The purpose of the paper is to present recent research that explores the after-life of specific new and reconditioned biogenic and non-biogenic material types and how the understanding of materials' natural processes of transformation when exposed to the external climate, can inform initial design decisions. With qualities to receive in a transient and contingent manner, ecological relationships between material, the colonizing organisms and resulting performances invite opportunities for new design explorations for the benefit of both the needs of human society and the needs of our natural environment. The research follows designing for the benefit of both and engaging in both biogenic and non-biogenic material engineering whilst embracing the continual demand for colonization - human and environment, and the aptitude of a material to be colonized by one or several groups of living organisms without necessarily undergoing any severe deterioration, but embracing weathering, patination and discoloring, and at the same time establishing new habitat. The research follows iterative prototyping processes where knowledge has been accumulated via explorations of specific material performances, from laboratory to construction mock-ups focusing on the architectural qualities embedded in control of production techniques and facilitating longer-term patinas of material surfaces to extend the aesthetic beyond common judgments. Experiments are therefore focused on how the inherent material qualities drive a design brief toward specific investigations to explore aesthetics induced through production, patinas and colonization obtained over time while exposed and interactions with external climate conditions.

Keywords: biogenic and non-biogenic, natural processes of transformation, colonization, patina

Procedia PDF Downloads 59

Authors: Pratyush Vatsala, Sanjay Ahuja

Abstract:

The national security and human rights are related terms as there is nothing like absolute security or absolute human right. If we are committed to security, human right is a problem and also a solution, and if we deliberate on human rights, security is a problem but also part of the solution. Ultimately, we have to maintain a balance between the two co-related terms. As more and more armed forces are being deployed by the government within the nation for maintaining peace and security, using force against its own citizen, the search for a judicious balance between intent and action needs to be emphasized. Notwithstanding that a nation state needs complete political independence; the search for security is a driving force behind unquestioned sovereignty. If security is a human value, it overlaps the value of freedom, order, and solidarity. Now, the question needs to be explored, to what extent human rights can be compromised in the name of security in Kashmir or Mizoram like places. The present study aims to explore the issue of maintaining a balance between the use of power and good governance as human rights, providing security as a human value. This paper has been prepared with an aim of strengthening the understanding of the complex and multifaceted relationship between human rights and security forces operating for conflict management and identifies some of the critical human rights issues raised in the context of security forces operations highlighting the relevant human rights principles and standards in which Security as human value be respected at all times and in particular in the context of security forces operations in India.

Keywords: Kashmir, Mizoram, security, value, human right

Procedia PDF Downloads 251