Search results for: blade force

Authors: Justyna Skrzyńska, Zdzisław Kobos, Zbigniew Wochyński

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The assessment of characterologic type is an essential element which decides about the proper task performance in the Air Forces. The aim of the research was to specify the percentage distribution of characterologic features by cadets studying particular courses in Polish Air Force Academy with the use of questionnaire. 34 first-year cadets chosen by lot and disunited into aircrafts pilots (N-10), helicopter pilots (N-13) and navigators(N-11) participated in the research. All of the questioned have had their psychomotor education examined in Military Aviation Medicine Institute in Warsaw, Poland. Moreover all of them are characterised by very good fitness. In the research, an anonymous poll(based on Myers-Briggs Type Indicator) appraising cadets’ characterologic type has been used. Cadets were provided with the same accommodation and nutrition. The findings have shown that percentage distribution was diversified, however it could be distinctly observed that most of future helicopter pilots (69%) are introverts whereas the majority of aircrafts pilots (70%) and navigators (100%) are extraverts. Moreover, it was also observed that 70% of cadets studying aircrafts pilotage run regular lifestyle and have judging skill according to Myers-Briggs Type Indicator. In future navigators group, 73% of students do not have this characteristic. The research has shown that cadets studying pilotage are more likely to demonstrate the characteristics which are essential for a performance of the important tasks in pilots environment than the cadets studying navigation.

Keywords: pilot, Myers-Briggs Type indicator, questionnaire research, cadets, psychomotor education

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Authors: Maria Elisabete Costa Ferreira

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Domestic violence is a serious social issue in which victims are mostly women. Domestic violence develops in cycles, starting with the building of tension, passing through the incident of abuse and ending with reconciliation, also known as honeymoon. As time goes by, the shorter these phases become, and the greater and more severe the attacks, rarely leading to the death of the victim of abuse. Sometimes, the victim stops the abuse by killing the aggressor, usually after the immediate aggression has taken place. This poses an important obstacle to the claim of self-defense by the victim of domestic violence pending trial for the homicide of her long-time abuser. The main problem with self-defense claims in such cases is that the law requires the act of aggression to be present or imminent (imminent threat or immediate danger) so that it permits the victim to take her defense into her own hands. If the episode of aggression has already taken place, this general requirement for the admissibility of self-defense is not satisfied. This paper sheds new light on the concept of the actuality of the aggression, understanding that, since domestic violence is a permanent offense, for as long as the victim stays under the domain of the aggressor, imminent threat will be present, allowing the self-defense claim of a woman who kills her abuser in such circumstances to be admissible. An actualist interpretation of the requirement of the necessity of the means used in self-defense will be satisfied when evaluated from the subjective perspective of the intimate partner victim. Necessity will be satisfied if it is reasonable for the victim to perceive the use of lethal force as the only means to release herself from the abuser.

Keywords: domestic violence, homicide, self-defense, imminent threat, necessity of lethal force

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Authors: Karim Kheloufi, El Hachemi Amara

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In the present study, a three-dimensional transient numerical model was developed to study the temperature field and cutting kerf shape during laser fusion cutting. The finite volume model has been constructed, based on the Navier–Stokes equations and energy conservation equation for the description of momentum and heat transport phenomena, and the Volume of Fluid (VOF) method for free surface tracking. The Fresnel absorption model is used to handle the absorption of the incident wave by the surface of the liquid metal and the enthalpy-porosity technique is employed to account for the latent heat during melting and solidification of the material. To model the physical phenomena occurring at the liquid film/gas interface, including momentum/heat transfer, a new approach is proposed which consists of treating friction force, pressure force applied by the gas jet and the heat absorbed by the cutting front surface as source terms incorporated into the governing equations. All these physics are coupled and solved simultaneously in Fluent CFD®. The main objective of using a transient phase change model in the current case is to simulate the dynamics and geometry of a growing laser-cutting generated kerf until it becomes fully developed. The model is used to investigate the effect of some process parameters on temperature fields and the formed kerf geometry.

Keywords: laser cutting, numerical simulation, heat transfer, fluid flow

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Authors: Maria Pintea, Nigel Mason

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Induced chemistry is one of the newest pathways in the nanotechnology field with applications in the focused electron beam induced processes for deposition of nm scale structures. Si(OPr)₄ and Ti(OEt)₄ are two of the precursors that have not been so extensively researched, though highly sought for semiconductor and medical applications fields, the two compounds make good candidates for FEBIP and are the subject of velocity slice map imaging analysis for deposition purposes, offering information on kinetic energies, fragmentation channels, and angular distributions. The velocity slice map imaging technique is a method used for the characterization of molecular dynamics of the molecule and the fragmentation channels as a result of induced chemistry. To support the gas-phase analysis, Meso-Bio-Nano simulations of irradiation dynamics studies are employed with final results on Fe(CO)₅ deposited on various substrates. The software is capable of running large scale simulations for complex biomolecular, nano- and mesoscopic systems with applications to thermos-mechanical DNA damage, complex materials, gases, nanoparticles for cancer research and deposition applications for nanotechnology, using a large library of classical potentials, many-body force fields, molecular force fields involved in the classical molecular dynamics.

Keywords: focused electron beam induced deposition, FEBID, induced chemistry, molecular dynamics, velocity map slice imaging

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Authors: Marco Furinghetti, Alberto Pavese, Michele Rinaldi

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Concave Surface Slider devices have been more and more used in real applications for seismic protection of both bridge and building structures. Several research activities have been carried out, in order to investigate the lateral response of such a typology of devices, and a reasonably high level of knowledge has been reached. If radial analysis is performed, the frictional force is always aligned with respect to the restoring force, whereas under bidirectional seismic events, a bi-axial interaction of the directions of motion occurs, due to the step-wise projection of the main frictional force, which is assumed to be aligned to the trajectory of the isolator. Nonetheless, if non-linear time history analyses have to be performed, standard codes provide precise rules for the definition of an averagely spectrum-compatible set of accelerograms in radial conditions, whereas for bidirectional motions different combinations of the single components spectra can be found. Moreover, nowadays software for the adjustment of natural accelerograms are available, which lead to a higher quality of spectrum-compatibility and to a smaller dispersion of results for radial motions. In this endeavor a simplified design procedure is defined, for building structures, base-isolated by means of Concave Surface Slider devices. Different case study structures have been analyzed. In a first stage, the capacity curve has been computed, by means of non-linear static analyses on the fixed-base structures: inelastic fiber elements have been adopted and different direction angles of lateral forces have been studied. Thanks to these results, a linear elastic Finite Element Model has been defined, characterized by the same global stiffness of the linear elastic branch of the non-linear capacity curve. Then, non-linear time history analyses have been performed on the base-isolated structures, by applying seven bidirectional seismic events. The spectrum-compatibility of bidirectional earthquakes has been studied, by considering different combinations of single components and adjusting single records: thanks to the proposed procedure, results have shown a small dispersion and a good agreement in comparison to the assumed design values.

Keywords: concave surface slider, spectrum-compatibility, bidirectional earthquake, base isolation

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Authors: Justin Pargeter, Metin Eren

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Lithic miniaturization, the systematic production and use of small tools from small cores, was a consequential development in Pleistocene lithic technology. The bipolar reduction is an important, but often overlooked and misidentified, strategy for lithic miniaturization. This experiment addresses the role of axial bipolar reduction in processes of lithic miniaturization. The experiments answer two questions: what benefits does axial bipolar reduction provide, and can we distinguish axial bipolar reduction from freehand reduction? Our experiments demonstrate the numerous advantages of bipolar reduction in contexts of lithic miniaturization. Bipolar reduction produces more cutting edge per gram and is more economical than freehand reduction. Our cutting edge to mass values exceeds even those obtained with pressure blade production on high-quality obsidian. The experimental results show that bipolar reduction produces cutting edge quicker and is more efficient than freehand reduction. We show that bipolar reduction can be distinguished from freehand reduction with a high degree of confidence using the quantitative criteria in these experiments. These observations overturn long-held perceptions about bipolar reduction. We conclude by discussing the role of bipolar reduction in lithic miniaturization and Stone Age economics more broadly.

Keywords: lithic miniaturization, bipolar reduction, late Pleistocene, Southern Africa

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Authors: B. Neethu, Diptesh Das

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The present study investigates the performance of a semi-active controller using magneto-rheological dampers (MR) for seismic response reduction of a multi-span bridge. The application of structural control to the structures during earthquake excitation involves numerous challenges such as proper formulation and selection of the control strategy, mathematical modeling of the system, uncertainty in system parameters and noisy measurements. These problems, however, need to be tackled in order to design and develop controllers which will efficiently perform in such complex systems. A control algorithm, which can accommodate un-certainty and imprecision compared to all the other algorithms mentioned so far, due to its inherent robustness and ability to cope with the parameter uncertainties and imprecisions, is the sliding mode algorithm. A sliding mode control algorithm is adopted in the present study due to its inherent stability and distinguished robustness to system parameter variation and external disturbances. In general a semi-active control scheme using an MR damper requires two nested controllers: (i) an overall system controller, which derives the control force required to be applied to the structure and (ii) an MR damper voltage controller which determines the voltage required to be supplied to the damper in order to generate the desired control force. In the present study a sliding mode algorithm is used to determine the desired optimal force. The function of the voltage controller is to command the damper to produce the desired force. The clipped optimal algorithm is used to find the command voltage supplied to the MR damper which is regulated by a semi active control law based on sliding mode algorithm. The main objective of the study is to propose a robust semi active control which can effectively control the responses of the bridge under real earthquake ground motions. Lumped mass model of the bridge is developed and time history analysis is carried out by solving the governing equations of motion in the state space form. The effectiveness of MR dampers is studied by analytical simulations by subjecting the bridge to real earthquake records. In this regard, it may also be noted that the performance of controllers depends, to a great extent, on the characteristics of the input ground motions. Therefore, in order to study the robustness of the controller in the present study, the performance of the controllers have been investigated for fourteen different earthquake ground motion records. The earthquakes are chosen in such a way that all possible characteristic variations can be accommodated. Out of these fourteen earthquakes, seven are near-field and seven are far-field. Also, these earthquakes are divided into different frequency contents, viz, low-frequency, medium-frequency, and high-frequency earthquakes. The responses of the controlled bridge are compared with the responses of the corresponding uncontrolled bridge (i.e., the bridge without any control devices). The results of the numerical study show that the sliding mode based semi-active control strategy can substantially reduce the seismic responses of the bridge showing a stable and robust performance for all the earthquakes.

Keywords: bridge, semi active control, sliding mode control, MR damper

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Authors: Divyans Mahansaria

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User authentication is an important security measure for protecting confidential data and systems. However, the vulnerability while authenticating into a system has significantly increased. Thus, necessary mechanisms must be deployed during the process of authenticating a user to safeguard him/her from the vulnerable attacks. The proposed solution implements a novel authentication mechanism to counter various forms of security breach attacks including phishing, Trojan horse, replay, key logging, Asterisk logging, shoulder surfing, brute force search and others. QR code (Quick Response Code) is a type of matrix barcode or two-dimensional barcode that can be used for storing URLs, text, images and other information. In the proposed solution, during each new authentication request, a QR code is dynamically generated and presented to the user. A piece of generic information is mapped to plurality of elements and stored within the QR code. The mapping of generic information with plurality of elements, randomizes in each new login, and thus the QR code generated for each new authentication request is for one-time use only. In order to authenticate into the system, the user needs to decode the QR code using any QR code decoding software. The QR code decoding software needs to be installed on handheld mobile devices such as smartphones, personal digital assistant (PDA), etc. On decoding the QR code, the user will be presented a mapping between the generic piece of information and plurality of elements using which the user needs to derive cipher secret information corresponding to his/her actual password. Now, in place of the actual password, the user will use this cipher secret information to authenticate into the system. The authentication terminal will receive the cipher secret information and use a validation engine that will decipher the cipher secret information. If the entered secret information is correct, the user will be provided access to the system. Usability study has been carried out on the proposed solution, and the new authentication mechanism was found to be easy to learn and adapt. Mathematical analysis of the time taken to carry out brute force attack on the proposed solution has been carried out. The result of mathematical analysis showed that the solution is almost completely resistant to brute force attack. Today’s standard methods for authentication are subject to a wide variety of software, hardware, and human attacks. The proposed scheme can be very useful in controlling the various types of authentication related attacks especially in a networked computer environment where the use of username and password for authentication is common.

Keywords: authentication, QR code, cipher / decipher text, one time password, secret information

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Authors: Saim Iftikhar Awan, Farhan Ali

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Wind power has now become one of the most important resources of renewable energy. The machine which extracts kinetic energy from wind is wind turbine. This work is all about the electrical power analysis of horizontal axis wind turbine to check the efficiency of different configurations of wind turbines to get maximum output and comparison of experimental and Computational Fluid Dynamics (CFD) results. Different experiments have been performed to obtain that configuration with the help of which we can get the maximum electrical power output by changing the different parameters like the number of blades, blade shape, wind speed, etc. in first step experimentation is done, and then the similar configuration is designed in 3D CAD software. After a series of experiments, it has been found that the turbine with four blades at an angle of 75° gives maximum power output and increase in wind speed increases the power output. The models designed on CAD software are imported on ANSYS-FLUENT to predict mechanical power. This mechanical power is then converted into electrical power, and the results were approximately the same in both cases. In the end, a comparison has been done to compare the results of experiments and ANSYS-FLUENT.

Keywords: computational analysis, power efficiency, wind energy, wind turbine

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Authors: Djeridi Rachid, Ould Ouali Mohand

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The search of a mechanism for the elastomer abrasive wear study is an open issue. The practice difficulties are complex due to the complexity of deformation mechanism, to the complex mechanism of the material tearing and to the marked interactions between the tribological parameters. In this work, we present an experimental technique to study the elastomers abrasive wear. The interaction 'elastomer/indenter' implicate dependant ant temporary of different tribological parameters. Consequently, the phenomenon that governs this interaction is not easy to explain. An optimal elastomers compounding and an adequate utilization conditions of these materials that define its resistance at the abrasion is discussed. The results are confronted to theoretical models: the weight loss variation in function of blade angle or in function of cycle number is in agreement with rupture models and with the mechanism of fissures propagation during the material tearing in abrasive wear of filler elastomers. The weight loss in function of the sliding velocity shows the existence of a critical velocity that corresponds to the maximal wear. The adding of silica or black carbon influences in a different manner on wear abrasive behavior of filler elastomers.

Keywords: abrasion wear, filler elastomer, tribology, hyperelastic

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Authors: Dries Dulsster

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This research we want to discuss the implications of the concept of ‘lalangue’ and illustrate its importance for lacanian psychoanalysis and its clinical practice. We will look at this concept through an in depth reading of Lacan’s later seminars, his lectures at the North-American universities and his study on James Joyce. We will illustrate the importance of this concept with a case study from a clinical practice. We will argue that the introduction of ‘lalangue’ has several theoretical and clinical implications that will radically change Lacans teachings. We will illustrate the distinction between language and lalangue. Language serves communication, but this is not the case with lalangue. We will claim that there is jouissance in language and will approach this by introducing the concept of ‘lalangue’. We will ask ourselves what the effect will be of this distinction and how we can use this in clinical practice. The concept of ‘lalangue’ will introduce a new way of thinking about the unconscious. It will force us to no longer view the unconscious as Symbolic, but as Imaginary or Real. Another implication will be the approach on the symptom, no longer approaching it as a formation of the unconscious. It will be renamed as ‘sinthome’, as function of the real. Last of all it will force us to rethink the lacanian interpretation and how we direct the treatment. The implications on a clinical level will be how we think about the lacanian interpretation and the direction of the treatment. We will no longer focus on language and meaning, but focus on jouissance and the ways in which the subject deals with this. We will illustrate this importance with a clinical case study. To summarize, the concept of lalangue forces us to radically rethink lacanian psychoanalysis, with major implications on a theoretical and clinical level. It introduces new concepts such as the real unconscious and the sinthome. It will also make us rethink the way we work as lacanian psychoanalysts.

Keywords: Lacan's later teaching, language, Lalangue, the unconscious

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Authors: Somya Ranjan Patro, Abhigna Bhatt, Arnab Banerjee

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Inertial amplifier has recently gained increasing attention as a new mechanism for vibration control of structures. Currently, theoretical investigations are undertaken by researchers to reveal its fundamentals and to understand its underline principles in altering the structural response of structures against dynamic loadings. This paper investigates experimental and analytical studies on the dynamic characteristics of hybrid beam inertial amplifier (HBIA). The analytical formulation of the HBIA has been derived by implementing the spectral element method and rigid body dynamics. This formulation gives the relation between dynamic force and the response of the structure in the frequency domain. Further, for validation of the proposed HBIA, the experiments have been performed. The experimental setup consists of a 3D printed HBIA of polylactic acid (PLA) material screwed at the base plate of the shaker system. Two numbers of accelerometers are used to study the response, one at the base plate of the shaker second one placed at the top of the inertial amplifier. A force transducer is also placed in between the base plate and the inertial amplifier to calculate the total amount of load transferred from the base plate to the inertial amplifier. The obtained time domain response from the accelerometers have been converted into the frequency domain using the Fast Fourier Transform (FFT) algorithm. The experimental transmittance values are successfully validated with the analytical results, providing us essential confidence in our proposed methodology.

Keywords: inertial amplifier, fast fourier transform, natural frequencies, polylactic acid, transmittance, vibration absorbers

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Authors: Irati Barandiaran, Xabier Velasco-Iza, Galder Kortaberria

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Hybrid inorganic/organic nanostructured materials based on block copolymers are of considerable interest in the field of Nanotechnology, taking into account that these nanocomposites combine the properties of polymer matrix and the unique properties of the added nanoparticles. The use of block copolymers as templates offers the opportunity to control the size and the distribution of inorganic nanoparticles. This research is focused on the surface modification of inorganic nanoparticles to reach a good interface between nanoparticles and polymer matrices which hinders the nanoparticle aggregation. The aim of this work is to obtain a good and selective dispersion of Fe3O4 magnetic nanoparticles into different types of block copolymers such us, poly(styrene-b-methyl methacrylate) (PS-b-PMMA), poly(styrene-b-ε-caprolactone) (PS-b-PCL) poly(isoprene-b-methyl methacrylate) (PI-b-PMMA) or poly(styrene-b-butadiene-b-methyl methacrylate) (SBM) by using different grafting strategies. Fe3O4 magnetic nanoparticles have been surface-modified with polymer or block copolymer brushes following different grafting methods (grafting to, grafting from and grafting through) to achieve a selective location of nanoparticles into desired domains of the block copolymers. Morphology of fabricated hybrid nanocomposites was studied by means of atomic force microscopy (AFM) and with the aim to reach well-ordered nanostructured composites different annealing methods were used. Additionally, nanoparticle amount has been also varied in order to investigate the effect of the nanoparticle content in the morphology of the block copolymer. Nowadays different characterization methods were using in order to investigate magnetic properties of nanometer-scale electronic devices. Particularly, two different techniques have been used with the aim of characterizing synthesized nanocomposites. First, magnetic force microscopy (MFM) was used to investigate qualitatively the magnetic properties taking into account that this technique allows distinguishing magnetic domains on the sample surface. On the other hand, magnetic characterization by vibrating sample magnetometer and superconducting quantum interference device. This technique demonstrated that magnetic properties of nanoparticles have been transferred to the nanocomposites, exhibiting superparamagnetic behavior similar to that of the maghemite nanoparticles at room temperature. Obtained advanced nanostructured materials could found possible applications in the field of dye-sensitized solar cells and electronic nanodevices.

Keywords: atomic force microscopy, block copolymers, grafting techniques, iron oxide nanoparticles

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Authors: Bohsiu Wu

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Among serious crimes, child homicide is a rather rare event. However, the killing of children stirs up a special type of emotion in society that pales other criminal acts. This study examines the relevancy of three possible community-level explanations for child homicide: social deprivation, female empowerment, and social isolation. The social deprivation hypothesis posits that child homicide results from lack of resources in communities. The female empowerment hypothesis argues that a higher female status translates into a higher level of capability to prevent child homicide. Finally, the social isolation hypothesis regards child homicide as a result of lack of social connectivity. Child homicide data, aggregated by US postal ZIP codes in California from 1990 to 1999, were analyzed with a negative binomial regression. The results of the negative binomial analysis demonstrate that social deprivation is the most salient and consistent predictor among all other factors in explaining child homicide victimization at the ZIP-code level. Both social isolation and female labor force participation are weak predictors of child homicide victimization across communities. Further, results from the negative binomial regression show that it is the communities with a higher, not lower, degree of female labor force participation that are associated with a higher count of child homicide. It is possible that poor communities with a higher level of female employment have a lesser capacity to provide the necessary care and protection for the children. Policies aiming at reducing social deprivation and strengthening female empowerment possess the potential to reduce child homicide in the community.

Keywords: child homicide, deprivation, empowerment, isolation

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Authors: Sifriyani Sifriyani, I Nyoman Budiantara, Sri Haryatmi, Gunardi Gunardi

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East Java Province has a first rank as a province that has the most counties and cities in Indonesia and has the largest population. In 2015, the population reached 38.847.561 million, this figure showed a very high population growth. High population growth is feared to lead to increase the levels of unemployment. In this study, the researchers mapped and modeled the unemployment rate with 6 variables that were supposed to influence. Modeling was done by nonparametric geographically weighted regression methods with truncated spline approach. This method was chosen because spline method is a flexible method, these models tend to look for its own estimation. In this modeling, there were point knots, the point that showed the changes of data. The selection of the optimum point knots was done by selecting the most minimun value of Generalized Cross Validation (GCV). Based on the research, 6 variables were declared to affect the level of unemployment in eastern Java. They were the percentage of population that is educated above high school, the rate of economic growth, the population density, the investment ratio of total labor force, the regional minimum wage and the ratio of the number of big industry and medium scale industry from the work force. The nonparametric geographically weighted regression models with truncated spline approach had a coefficient of determination 98.95% and the value of MSE equal to 0.0047.

Keywords: East Java, nonparametric geographically weighted regression, spatial, spline approach, unemployed rate

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Authors: Nafiseh Ebrahimi, Amir Jafari

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The study of humanoid character is of great interest to researchers in the field of robotics and biomechanics. One might want to know the forces and torques required to move a limb from an initial position to the desired destination position. Inverse dynamics is a helpful method to compute the force and torques for an articulated body limb. It enables us to know the joint torques required to rotate a link between two positions. Our goal in this study was to control a human-like articulated manipulator for a specific task of path tracking. For this purpose, the human arm was modeled with a three-link planar manipulator activated by Hill muscle model. Applying a proportional controller, values of force and torques applied to the joints were calculated by inverse dynamics, and then joints and muscle forces trajectories were computed and presented. To be more accurate to say, the kinematics of the muscle-joint space was formulated by which we defined the relationship between the muscle lengths and the geometry of the links and joints. Secondary, the kinematic of the links was introduced to calculate the position of the end-effector in terms of geometry. Then, we considered the modeling of Hill muscle dynamics, and after calculation of joint torques, finally, we applied them to the dynamics of the three-link manipulator obtained from the inverse dynamics to calculate the joint states, find and control the location of manipulator’s end-effector. The results show that the human arm model was successfully controlled to take the designated path of an ellipse precisely.

Keywords: arm manipulator, hill muscle model, six-muscle model, three-link lodel

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Authors: Fatemeh Sadat Sharifi

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In this research, a barotropic model was employed to consider the tidal studies in the Persian Gulf and Oman Sea, where the only sufficient force was the tidal force. To do that, a finite-difference, free-surface model called Regional Ocean Modeling System (ROMS), was employed on the data over the Persian Gulf and Oman Sea. To analyze flow patterns of the region, the results of limited size model of The Finite Volume Community Ocean Model (FVCOM) were appropriated. The two points were determined since both are one of the most critical water body in case of the economy, biology, fishery, Shipping, navigation, and petroleum extraction. The OSU Tidal Prediction Software (OTPS) tide and observation data validated the modeled result. Next, tidal elevation and speed, and tidal analysis were interpreted. Preliminary results determine a significant accuracy in the tidal height compared with observation and OTPS data, declaring that tidal currents are highest in Hormuz Strait and the narrow and shallow region between Iranian coasts and Islands. Furthermore, tidal analysis clarifies that the M_2 component has the most significant value. Finally, the Persian Gulf tidal currents are divided into two branches: the first branch converts from south to Qatar and via United Arab Emirate rotates to Hormuz Strait. The secondary branch, in north and west, extends up to the highest point in the Persian Gulf and in the head of Gulf turns counterclockwise.

Keywords: numerical model, barotropic tide, tidal currents, OSU tidal prediction software, OTPS

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Authors: Sanghamitra Acharya, Suwarna Datar

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Extensive use of digital and smart communication createsprolong expose of unwanted electromagnetic (EM) radiations. This harmful radiation creates not only malfunctioning of nearby electronic gadgets but also severely affects a human being. So, a suitable microwave absorbing material (MAM) becomes a necessary urge in the field of stealth and radar technology. Initially, Aluminum based hexa ferrite was prepared by sol-gel technique and for carbon derived composite was prepared by the simple one port chemical reduction method. Finally, composite films of Poly (Vinylidene) Fluoride (PVDF) are prepared by simple gel casting technique. Present work demands that aluminum-based hexaferrite phase conjugated with graphene in PVDF matrix becomes a suitable candidate both in commercially important X and Ku band. The structural and morphological nature was characterized by X-Ray diffraction (XRD), Field emission-scanning electron microscope (FESEM) and Raman spectra which conforms that 30-40 nm particles are well decorated over graphene sheet. Magnetic force microscopy (MFM) and conducting force microscopy (CFM) study further conforms the magnetic and conducting nature of composite. Finally, shielding effectiveness (SE) of the composite film was studied by using Vector network analyzer (VNA) both in X band and Ku band frequency range and found to be more than 30 dB and 40 dB, respectively. As prepared composite films are excellent microwave absorbers.

Keywords: carbon nanocomposite, microwave absorbing material, electromagnetic shielding, hexaferrite

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Authors: Paul E. Olsen

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Researchers, businesses, and governments study the glass ceiling faced by women and members of minority groups at work, but the experiences of gay men, lesbians, and bisexual men and women with the lavender ceiling have not received similar attention. This qualitative research traces similarities between the lavender ceiling and the glass ceiling. More specifically, it presents a study designed to elucidate the experiences of gay men at work and compare them with those of women and minority group members, as reported in research literature on the glass ceiling. This research asked: 1) What have gay men experienced in the workplace? 2) What experiences have they had with recruitment, mentors, corporate climate, advancement opportunities, performance evaluation, social activities, harassment, and task force and committee assignments? 3) How do these experiences compare with those of women and minorities who have described their experiences with the glass ceiling? Purposeful and convenience sampling were used as participant selection strategies. Participants were diverse in terms of age, education, and industry. Data for this study were collected through semi-structured individual interviews with eight self-identified gay men working in human services, manufacturing, marketing, finance, government, the nonprofit sector, and retail. The gay men in the study described workplace experiences similar to descriptions of the glass ceiling faced by women and minorities. The lavender ceiling parallels the glass ceiling in corporate climates, harassment, mentors, social activities, promotions and performance appraisal, and task force and committee assignments at work. Women and most minorities do not, however, face the disclosure dilemma: Should one reveal his sexual orientation at work?

Keywords: discrimination, diversity, gay and lesbian, human resource

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Authors: Xiujing Chen, Thammananya Sakcharoen, Wilailuk Niyommaneerat

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China's tourism industry is in a state of shock and recovery, although COVID-19 has brought great impact and challenges to the tourism industry. The theory of sustainable development originates from the contradiction of increasing awareness of environmental protection and the pursuit of economic interests. The sustainable development of tourism should consider social, economic, and environmental factors and develop tourism in a planned and targeted way from the overall situation. Guilin is one of the popular tourist cities in China. However, there exist several problems in Guilin tourism, such as low quality of scenic spot construction and low efficiency of tourism resource development. Due to its unwell-managed, Guilin's tourism industry is facing problems such as supply and demand crowding pressure for tourists. According to the data from 2009 to 2019, there is a change in the degree of sustainable development of Guilin tourism. This research aimed to evaluate the sustainable development state of Guilin tourism using the DPSIR (driving force/pressure/state/impact/response) framework and to provide suggestions and recommendations for sustainable development in Guilin. An improved TOPSIS (technology for order preference by similarity to an ideal solution) model based on the entropy weights relationship is applied to the quantitative analysis and to analyze the mechanisms of sustainable development of tourism in Guilin. The DPSIR framework organizes indicators into sub-five categories: of which twenty-eight indicators related to sustainable aspects of Guilin tourism are classified. The study analyzed and summarized the economic, social, and ecological effects generated by tourism development in Guilin from 2009-2019. The results show that the conversion rate of tourism development in Guilin into regional economic benefits is more efficient than that into social benefits. Thus, tourism development is an important driving force of Guilin's economic growth. In addition, the study also analyzed the static weights of 28 relevant indicators of sustainable development of tourism in Guilin and ranked them from largest to smallest. Then it was found that the economic and social factors related to tourism revenue occupy the highest weight, which means that the economic and social development of Guilin can influence the sustainable development of Guilin tourism to a greater extent. Therefore, there is a two-way causal relationship between tourism development and economic growth in Guilin. At the same time, ecological development-related indicators also have relatively large weights, so ecological and environmental resources also have a great influence on the sustainable development of Guilin tourism.

Keywords: DPSIR framework, entropy weights analysis, sustainable development of tourism, TOPSIS analysis

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Authors: Kelsey Scanlon

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Introduction: With the rate of female collegiate and professional athletes on the rise in recent decades, fluctuations in physical performance in relation to the menstrual cycle is an important area of study. PURPOSE: The purpose of this research was to compare differences in upper and lower body maximal anaerobic capacities across a single menstrual cycle. Methode: Participants (n=11) met a total of four times; once for familiarization and again on day 1 of menses (follicular phase), day 14 (ovulation), and day 21 (luteal phase) respectively. Upper body power was assessed using a bench press weight of ~50% of the participant’s predetermined 1-repetition maximum (1-RM) on a ballistic measurement system and variables included peak force (N), mean force (N), peak power (W), mean power (W), and peak velocity (m/s). Lower body power output was collected using a standard Wingate test. The variables of interest were anaerobic capacity (w/kg), peak power (W), mean power (W), fatigue index (W/s), and total work (J). Result: Statistical significance was not observed (p > 0.05) in any of the aforementioned variables after completing multiple one ways of analyses of variances (ANOVAs) with repeated measures on time. Conclusion: Within the parameters of this research, neither female upper nor lower body power output differed across the menstrual cycle when analyzed using 50% of one repetition (1RM) maximal bench press and the 30-second maximal effort cycle ergometer Wingate test. Therefore, researchers should not alter their subject populations due to the incorrect assumption that power output may be influenced by the menstrual cycle.

Keywords: anaerobic, athlete, female, power

Procedia PDF Downloads 146

Authors: Nahed Al-Hajeri

Abstract:

Time and cost is an integral part of every construction plan and can affect each party’s contractual obligations. The performance of both time and cost are usually important to the client and contractor during the project. Almost all construction projects are experiencing time overrun. These time overruns always contributed as expensive to both client and contractor. Construction of any project inside the gathering centers involves complex management skills related to work force, materials, plant, machineries, new technologies etc. It also involves many agencies interdependent on each other like the vendors, structural and functional designers including various types of specialized engineers and it includes support of contractors and specialized contractors. This paper mainly highlights the types of construction delays due to which project suffer time and cost overrun. This paper also speaks about the delay causes and factors that contribute to the construction sequence delay for the oil and gas projects. Construction delay is supposed to be one of the repeated problems in the construction projects and it has an opposing effect on project success in terms of time, cost and quality. Some effective methods are identified to minimize delays in construction projects such as: 1. Site management and supervision, 2. Effective strategic planning, 3. Clear information and communication channel. Our research paper studies the types of delay with some real examples with statistic results and suggests solutions to overcome this problem.

Keywords: non-compensable delay, delays caused by force majeure, compensable delay, delays caused by the owner or the owner’s representative, non-excusable delay, delay caused by the contractor or the contractor’s representative, concurrent delay, delays resulting from two separate causes at the same time

Procedia PDF Downloads 242

Authors: Pawel Martynowicz

Abstract:

Vibrations are a crucial problem for slender structures such as towers, masts, chimneys, wind turbines, bridges, high buildings, etc., that is why most of them are equipped with vibration attenuation or fatigue reduction solutions. In this work, a slender structure (i.e., wind turbine tower-nacelle model) equipped with nonlinear, semiactive tuned vibration absorber(s) is analyzed. For this study purposes, magnetorheological (MR) dampers are used as semiactive actuators. Several optimal-based approaches to structural vibration attenuation are investigated against the standard ‘ground-hook’ law and passive tuned vibration absorber(s) implementations. The common approach to optimal control of nonlinear systems is offline computation of the optimal solution, however, so determined open loop control suffers from lack of robustness to uncertainties (e.g., unmodelled dynamics, perturbations of external forces or initial conditions), and thus perturbation control techniques are often used. However, proper linearization may be an issue for highly nonlinear systems with implicit relations between state, co-state, and control. The main contribution of the author is the development as well as numerical and experimental verification of the Pontriagin maximum-principle-based vibration control concepts that produce directly actuator control input (not the demanded force), thus force tracking algorithm that results in control inaccuracy is entirely omitted. These concepts, including one-step optimal control, quasi-optimal control, and optimal-based modified ‘ground-hook’ law, can be directly implemented in online and real-time feedback control for periodic (or semi-periodic) disturbances with invariant or time-varying parameters, as well as for non-periodic, transient or random disturbances, what is a limitation for some other known solutions. No offline calculation, excitations/disturbances assumption or vibration frequency determination is necessary, moreover, all of the nonlinear actuator (MR damper) force constraints, i.e., no active forces, lower and upper saturation limits, hysteresis-type dynamics, etc., are embedded in the control technique, thus the solution is optimal or suboptimal for the assumed actuator, respecting its limitations. Depending on the selected method variant, a moderate or decisive reduction in the computational load is possible compared to other methods of nonlinear optimal control, while assuring the quality and robustness of the vibration reduction system, as well as considering multi-pronged operational aspects, such as possible minimization of the amplitude of the deflection and acceleration of the vibrating structure, its potential and/or kinetic energy, required actuator force, control input (e.g. electric current in the MR damper coil) and/or stroke amplitude. The developed solutions are characterized by high vibration reduction efficiency – the obtained maximum values of the dynamic amplification factor are close to 2.0, while for the best of the passive systems, these values exceed 3.5.

Keywords: magnetorheological damper, nonlinear tuned vibration absorber, optimal control, real-time structural vibration attenuation, wind turbines

Procedia PDF Downloads 124

Authors: Yiping Meng, Yiming Sun

Abstract:

The traditional construction industry is unable to meet the requirements for novel fabrication and construction. Automated construction and digital design have emerged as industry development trends that compensate for this shortcoming under the backdrop of Industrial Revolution 4.0. Benefitting from more flexible working space and more various end-effector tools compared to CNC methods, robot fabrication and construction techniques have been used in irregular architectural design. However, there is a lack of a systematic and comprehensive design and optimisation workflow considering geometric form, material, and fabrication methods. This paper aims to propose a design optimisation workflow for improving the rationality of a free-form timber structure fabricated by the robotic arm. Firstly, the free-form surface is described by NURBS, while its structure is calculated using the finite element analysis method. Then, by considering the characteristics and limiting factors of robotic timber fabrication, strain energy and robustness are set as optimisation objectives to optimise structural morphology by gradient descent method. As a result, an optimised structure with axial force as the main force and uniform stress distribution is generated after the structure morphology optimisation process. With the decreased strain energy and the improved robustness, the generated structure's bearing capacity and mechanical properties have been enhanced. The results prove the feasibility and effectiveness of the proposed optimisation workflow for free-form timber structure morphology design.

Keywords: robotic fabrication, free-form timber structure, Multi-objective optimisation, Structural morphology, rational design

Procedia PDF Downloads 194

Authors: Luis Prada, Jose Gomez, Arlex Chaves, Julio Pedraza

Abstract:

Polymeric liquids have been used in the oil industry, especially at enhanced oil recovery (EOR). From the rheological point of view, polymers have the particularity of being viscoelastic liquids. One of the most common and useful models to describe that behavior is the Upper Convected Maxwell model (UCM). The main characteristic of the polymer used in EOR process is the increase in viscosity which pushes the oil outside of the reservoir. The elasticity could contribute in the drag of the oil that stays in the reservoir. Studying the elastic effect on the oil drop at the pore scale, bring an explanation if the addition of elastic force could mobilize the oil. This research explores if the contraction and expansion of the polymer in the pore scale may increase the elastic behavior of this kind of fluid. For that reason, this work simplified the pore geometry and build two simple geometries with micrometer lengths. Using source terms with the user define a function this work introduces the UCM model in the ANSYS fluent simulator with the purpose of evaluating the elastic effect of the polymer in a contraction and expansion geometry. Also, using the Eulerian multiphase model, this research considers the possibility that extra elastic force will show a deformation effect on the oil; for that reason, this work considers an oil drop on the upper wall of the geometry. Finally, all the simulations exhibit that at the pore scale conditions exist extra vortices at UCM model but is not possible to deform the oil completely and push it outside of the restrictions, also this research find the conditions for the oil displacement.

Keywords: ANSYS fluent, interfacial fluids mechanics, polymers, pore scale, viscoelasticity

Procedia PDF Downloads 132

Authors: Ahmed A. El-Kafy Amer, H. M. Gad, A. I. Ibrahim, S. I. Abdel-Mageed, T. M. Farag

Abstract:

This paper represents an experimental study of LPG diffusion flame at elevated air preheated temperatures. The flame is stabilized in a vertical water-cooled combustor by using air swirler. An experimental test rig was designed to investigate the different operating conditions. The burner head is designed so that the LPG fuel issued centrally and surrounded by the swirling air issues from an air swirler. There are three air swirlers having the same dimensions but having different blade angles to give different swirl numbers of 0.5, 0.87 and 1.5. The combustion air was heated electrically before entering the combustor up to a temperature about 500 K. Three air to fuel mass ratios of 30, 40 and 50 were also studied. The effect of air preheated temperature, swirl number and air to fuel mass ratios on the temperature maps, visible flame length, high temperature region (size) and exhaust species concentrations are studied. Some results show that as the air preheated temperature increases, the volume of high temperature region also increased but the flame length decreased. Increasing the air preheated temperature, EINOx, EICO2 and EIO2 increased, while EICO decreased. Increasing the air preheated temperature from 300 to 500 K, for all air swirl numbers used, the highest increase in EINOx, EICO2 and EIO2 are 141, 4 and 65%, respectively.

Keywords: air preheated temperature, air swirler, flame length, emission index

Procedia PDF Downloads 480

Authors: Majid Haghshenas, James Wilson, Ranganathan Kumar

Abstract:

In this study, an Algebraic Coupled Level Set-Volume of Fluid (A-CLSVOF) method with capillary pressure treatment is proposed for the modeling of two-phase capillary flows. The Volume of Fluid (VOF) method is utilized to incorporate one-way coupling with the Level Set (LS) function in order to further improve the accuracy of the interface curvature calculation and resulting surface tension force. The capillary pressure is determined and treated independently of the hydrodynamic pressure in the momentum balance in order to maintain consistency between cell centered and interpolated values, resulting in a reduction in parasitic currents. In this method, both VOF and LS functions are transported where the new volume fraction determines the interface seed position used to reinitialize the LS field. The Hamilton-Godunov function is used with a second order (in space and time) discretization scheme to produce a signed distance function. The performance of the current methodology has been tested against some common test cases in order to assess the reduction in non-physical velocities and improvements in the interfacial pressure jump. The cases of a static drop, non-linear Rayleigh-Taylor instability and finally a droplets impact on a liquid pool were simulated to compare the performance of the present method to other well-known methods in the area of parasitic current reduction, interface location evolution and overall agreement with experimental results.

Keywords: two-phase flow, capillary flow, surface tension force, coupled LS with VOF

Procedia PDF Downloads 358

Authors: Zehra Betül Karakoç

Abstract:

Aim: The aim of our study is to determine the changement pf plantar pressure after extracorporeal shock wave therapy (ESWT) in a patient with calcaneal spur (CS). Method: Thirty patients with CS who received ESWT treatment at Kartal Yavuz Selim State Hospital between May 2020 and November 2022 participated in this study. Demographic information of the cases was obtained. Pain levels and plantar pressure were measured with Visuel Analog Scale (VAS) and pedobarography, respectively. Pedobarography measured the maximal strength, peak pressure level, and contact area values of the hind, middle, forefoot, and toes. The cases were re-evaluated 4 weeks after the application of 15 Hz, 2-3 bar, 2,000 beats ESWT for 3 sessions. 22 cases participated in the second evaluation. The data of all patients were evaluated bilaterally. Results: Pain intensity levels after treatment were statistically significantly decreased compared to before treatment (p=0.012). Maximum force and contact area values of total foot and forefoot increased significantly (p < 0.05). Conclusion: We consider that the increased max force value of total foot and forefoot area after ESWT is due to the normal walking rate gained related to decreased pain. ESWT treatment may have positive effects on foot pressure distribution and body biomechanics. In order to interpret the results of our study more clearly, randomized controlled studies with a larger number of cases were planned in the future.

Keywords: calcaneal spur, ESWT, plantar pressure, pain

Procedia PDF Downloads 72

Authors: Yingchen Yang

Abstract:

In the present work, development of a new vertical-axis unidirectional wave rotor is reported. The wave rotor is a key component of a wave energy converter (WEC), which harvests energy from ocean waves. Differing from the huge majority of WEC designs that perform reciprocating motions (heaving up and down, swaying back and forth, etc.), our wave rotor performs unidirectional rotation about a vertical axis when directly exposed in waves. The unidirectional feature of the rotor makes the rotor respond well in a wide range of the wave frequency. The vertical axis arrangement of the rotor makes the rotor insensitive to the wave propagation direction. The rotor employs blades with a cross-section in an airfoil shape and a span curled into a semi-oval shape. Two sets of blades, with one nested inside the other, constitute the rotor. In waves, water particles perform an omnidirectional motion that constantly changes in both spatial and temporal domains. The blade nesting permits a compact rotor configuration that ‘sees’ a relatively uniform local flow in the spatial domain. The rotor was experimentally tested in simulated waves in a wave flume under various conditions. The testing results show a promising unidirectional rotor that is capable of extracting energy from waves at a capture width ratio of 0.08 to 0.15, depending on detailed wave conditions.

Keywords: unidirectional, vertical axis, wave energy converter, wave rotor

Procedia PDF Downloads 236

Authors: Bander Alzahrani

Abstract:

Information-centric networking (ICN) using architectures such as Publish-Subscribe Internet Routing Paradigm (PSIRP) is one of the promising candidates for a future Internet, has recently been under the spotlight by the research community to investigate the possibility of redesigning the current Internet architecture to solve many issues such as routing scalability, security, and quality of services issues.. The Bloom filter-based forwarding is a source-routing approach that is used in the PSIRP architecture. This mechanism is vulnerable to brute force attacks which may lead to denial-of-service (DoS) attacks. In this work, we present a new forwarding approach that keeps the advantages of Bloom filter-based forwarding while mitigates attacks on the forwarding mechanism. In practice, we introduce a special type of forwarding nodes called Edge-FW to be placed at the edge of the network. The role of these node is to add an extra security layer by validating and inspecting packets at the edge of the network against brute-force attacks and check whether the packet contains a legitimate forwarding identifier (FId) or not. We leverage Certificateless Aggregate Signature (CLAS) scheme with a small size of 64-bit which is used to sign the FId. Hence, this signature becomes bound to a specific FId. Therefore, malicious nodes that inject packets with random FIds will be easily detected and dropped at the Edge-FW node when the signature verification fails. Our preliminary security analysis suggests that with the proposed approach, the forwarding plane is able to resist attacks such as DoS with very high probability.

Keywords: bloom filter, certificateless aggregate signature, denial-of-service, information centric network

Procedia PDF Downloads 198