Search results for: eddy current loss

Authors: Martin Hofmann, Diego Stutzer, Thomas Niederhauser, Juergen Burger

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Dental biofilm is the main etiologic factor for caries, periodontal and peri-implant infections. In addition to the risk of tooth loss, periodontitis is also associated with an increased risk of systemic diseases such as atherosclerotic cardiovascular disease and diabetes. For this reason, dental hygienists use ultrasonic scalers for prophylactic and periodontal care of the teeth. However, the current instruments are limited to their dimensions and operating frequencies. The innovative design of a planar ultrasonic transducer introduces a new type of dental scalers. The flat titanium-based design allows the mass to be significantly reduced compared to a conventional screw-mounted Langevin transducer, resulting in a more efficient and controllable scaler. For the development of the novel device, multi-physics finite element analysis was used to simulate and optimise various design concepts. This process was supported by prototyping and electromechanical characterisation. The feasibility and potential of a planar ultrasonic transducer have already been confirmed by our current prototypes, which achieve higher performance compared to commercial devices. Operating at the desired resonance frequency of 28 kHz with a driving voltage of 40 Vrms results in an in-plane tip oscillation with a displacement amplitude of up to 75 μm by having less than 8 % out-of-plane movement and an energy transformation factor of 1.07 μm/mA. In a further step, we will adapt the design to two additional resonance frequencies (20 and 40 kHz) to obtain information about the most suitable mode of operation. In addition to the already integrated characterization methods, we will evaluate the clinical efficiency of the different devices in an in vitro setup with an artificial biofilm pocket model.

Keywords: ultrasonic instrumentation, ultrasonic scaling, piezoelectric transducer, finite element simulation, dental biofilm, dental calculus

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Authors: B. Oral, C. Bal, M. S. Kar, A. Akgürbüz

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Loss of maxillary central incisors occurs in many patients, and the treatment of young adults with this problem is a challenge for both prosthodontists and orthodontists. Common treatment alternatives are distalization of adjacent teeth and fabrication of a conventional 3-unit fixed partial denture, a single implant supported crown restoration or a resin-bonded fixed partial denture. This case report describes the indication of a resin-bonded fixed partial denture, preparation of the abutment teeth and the prosthetic procedures. The technique described here represents a conservative, esthetically pleasing and rapid solution for the missing maxillary central incisor when implant placement and/or guided bone regeneration techniques are not feasible because of financial, social or time restrictions. In this case a 16 year-old female patient who lost her maxillary left central incisor six years ago in a bicycle accident applied to our clinic with a major complaint of her unaesthetic appearance associated with the loss of her maxillary left central incisor. Although there was an indication for orthodontic treatment because of the limited space at the traumatized area, the patient did not accept to receive any orthodontic procedure. That is why an implant supported restoration could not be an option for the narrow area. Therefore maryland bridge as a minimal invasive dental therapy was preferred as a retention appliance so the patient's aesthetic appearance was restored.

Keywords: Maryland bridge, single tooth restoration, aesthetics, maxillary central incisors

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Authors: Aritras Roy, Rinku Mukherjee

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The current study couples a quasi-steady Vortex Lattice Method and a camber correcting technique, ‘Decambering’ for unsteady post-stall flow prediction. The wake is force-free and discrete such that the wake lattices move with the free-stream once shed from the wing. It is observed that the time-averaged unsteady coefficient of lift sees a relative drop at post-stall angles of attack in comparison to its steady counterpart for some angles of attack. Multiple solutions occur at post-stall and three different algorithms to choose solutions in these regimes show both unsteadiness and non-convergence of the iterations. The distribution of coefficient of lift on the wing span also shows sawtooth. Distribution of vorticity changes both along span and in the direction of the free-stream as the wake develops over time with distinct roll-up, which increases with time.

Keywords: post-stall, unsteady, wing, aerodynamics

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Authors: Kumar Y., Suman D., Sumathi

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Introduction: Burns to the face account for between one-fourth and one-third of all burns. The loss of an eyebrow due to a burn or infection can have negative physical and psychological consequences for patients because eyebrows have a critical functional and aesthetic role on the face. Plastic surgeons face unique challenges in reconstructing eyebrows due to their complex anatomy and variations within genders. As a general rule, there are three techniques for reconstructing the eyebrow: superficial temporal artery island flap, a composite graft from the scalp, and mini or micro follicular grafts from the scalp. In situations where a sufficient amount of subcutaneous tissue is not available and the defect is big such as the case of burns, flaps like the superficial temporal artery scalp flap remain reliable options. In 2018, a 17-year-old female patient presented to the department of Burns Plastic and reconstructive Surgery of Guru Teg Bahadur Hospital, Delhi, India. A scald-burn injury to the face occurred two years before admission, resulting in bilateral eyebrow loss. We reconstructed the bilateral eyebrows using bilateral scalp island flaps based on the posterior branch of the superficial temporal artery. The reconstructed eyebrows successfully assumed a desirable shape and exhibited a natural appearance, which was consistent with preoperative expectations and the patient stated that she was more comfortable with her social relationships. Among the current treatment procedures, the superficial temporal artery island flap continues to be a versatile option for reconstructing the eyebrows after alopecia, especially in cases of burns. Results: During the 30 days follow-up period, the scalp island flap remained vascularised with normal hair growth, without complications. The reconstructed eyebrows successfully assumed a desirable shape and exhibited a natural appearance; the patient stated that she was more comfortable with her social relationships. Conclusion: In this case report, we demonstrated how scalp island flaps pedicled by the superficial temporal artery could be performed very safely and reliably to create new eyebrows.

Keywords: alopecia, burns, eyebrow, flap, superficial temporal artery

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Authors: Z. A. Ahmad, R. C. Omar, I. Z. Baharuddin, R. Roslan

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Assessments of social vulnerability, carried out holistically, can provide an important guide to the planning process and to decisions on resource allocation at various levels, and can help to raise public awareness of geo-hazard risks. The assessments can help to provide answers for basic questions such as the human vulnerability at the geo-hazard prone or disaster areas causing health damage, economic loss, loss of natural heritage and vulnerability impact of extreme natural hazard event. To overcome these issues, integrated framework for assessing the increasing human vulnerability to environmental changes caused by geo-hazards will be introduced using an indicator from landslide risk map that is related to agent based modeling platform. The indicators represent the underlying factors, which influence a community’s ability to deal with and recover from the damage associated with geo-hazards. Scope of this paper is particularly limited to landslides.

Keywords: social, vulnerability, geo-hazard, methodology, indicators

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Authors: Mihaela Popescu, Alexandru Bitoleanu

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This paper is focused on the reference current calculation in the compensation mode of the active DC traction substations. The so-called p-q theory of the instantaneous reactive power is used as theoretical foundation. The compensation goal of total compensation is taken into consideration for the operation under both sinusoidal and nonsinusoidal voltage conditions, through the two objectives of unity power factor and perfect harmonic cancelation. Four blocks of reference current generation implement the conceived algorithms and they are included in a specific Simulink library, which is useful in a DSP dSPACE-based platform working under Matlab/Simulink. The simulation results validate the correctness of the implementation and fulfillment of the compensation tasks.

Keywords: active power filter, DC traction, p-q theory, Simulink library

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Authors: Rian de Villiers

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Human mobility is one of the most significant development, foreign policy and domestic issues in the world today. Teacher loss due to migration is a global phenomenon that is impacting both developed and developing nations the world over. The purpose of this study was to find out how many newly qualified South African teachers were planning to teach in a foreign country; what were the prospective migrant teachers’ motives for migration; what destination countries were the most popular and why; and what were the prospective migrant teachers’ information needs before leaving South Africa. A group of final-year Bachelor of Education student teachers from a single university responded to a questionnaire on intra-and intercontinental migration. The responses were analysed quantitatively and/or qualitatively. The findings showed that 79% of the students indicated that they would be teaching in South Africa, 9% were planning to teach in another country, while 8% were undecided. More than a third of the students (38%) said that they would like to teach in another country in five years time. Just more than a quarter of the students (27%) preferred Australia as a destination, followed by the United Kingdom (16%), Korea (16%) and the USA (14%). The student teachers’ most important motive to teach in a foreign country was the opportunity to travel (27%), followed by earning a higher salary (26%) and professional development (23%). The student teachers indicated that their most important migration needs before leaving South Africa were information about health care, accommodation and banking assistance. Huge loss of teachers to host countries has a serious, negative impact upon the education system of most developing and/or source countries, including South Africa. Several steps and strategies to resolve teacher loss in South Africa are discussed.

Keywords: migration, academic mobility, teachers, teacher students, South Africa

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Authors: Lorcelie B. Taclan, Jolly S. Balila, Maribel Balagtas, Eunice M. Aclan, Myrtle C. Orbon, Emson Y. Taclan, Irenea A. Centeno

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Okara (soy pulp), a by-product and waste from the production of soymilk, tufo and tokwa and soybean-based vegan food products is readily available in the university thrice a week. The Food Factory owned and managed by AUP produces these food products weekly. Generally the study was conducted to determine the drying kinetics of soya pulp using the MCHPD. Specifically, it aimed to establish the time of drying; moisture loss per hour and percent moisture content of soya pulp and to establish the dried okara as an ingredient to other foods. The MCHPD is drying equipment that has an ideal drying condition of 50.00C and 10.0% relative humidity. Fresh and wet soya pulp were weighed at 1.0 kg per tray (21 drying trays), laid on the trays lined with cheese cloth. The MCHPD was set to desired drying conditions. Weight loss was monitored every hour and calculated using standard formulas. Research results indicated that the drying time for soya pulp was 19.0 hours; the % moisture content was reduced from 87.6.0% to 9.7.0% at an average moisture loss of 3.0 g/hr. The nutritional values of okara were favorably maintained with enhanced color. The dried okara was added as an ingredient to other healthy bakery products produced by the AUP Food Factory. Making use of okara would add nutritional values to other food products and would also help waste management concerns inside the university.

Keywords: okara, MCHPD, drying kinetics, nutritional values, waste management

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Authors: Selvam Noyel Victoria, Kavita Yadav, Manivannan Ramachandran

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The extract of Tagetes erecta (marigold flower) was used as a green corrosion inhibitor for mild steel (MS) in nitric acid medium. The weight loss measurements were performed to understand the inhibition mechanism. The effect of temperature on the behaviour of mild steel corrosion without and with inhibitor was studied. The temperature studies revealed that the activation energy increased from 12 kJ/mol to 28.8 kJ/mol with the addition of 500 ppm inhibitor concentration. The thermodynamic analysis and the adsorption isotherm studies revealed that the molecules of inhibitor show physical adsorption on the surface of mild steel. Based on weight loss measurements, adsorption of the inhibitor on the surface of mild steel follows Langmuir isotherm.

Keywords: Tagetes erecta, corrosion, adsorption, inhibitor

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Authors: Suzan Ibrahim

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Oil-based muds are the most regularly used rotary drilling methods in the oil and gas industry. However, they have a negative impact on the environment, which leads to restrictions of their application in many countries of the world. Consequently, looking for new eco-friendly alternative formulations of oil-based drilling fluids for the exploration of troublesome formations. As one of the developments of Novel formulation of environmentally friendly drilling fluids and investigation of the formulation for jatropha oil-based drilling fluid samples at different concentrations of viscosifiers such as low viscosity polyanionic cellulose (PAC- LV), high viscosity polyanionic cellulose (PAC-V) and local Egyptian bentonite. The oil-water ratio was taken as 70:30, which is beneficial in producing a low fluid loss. 15 drilling fluid samples were formulated different concentrations of bentonite, PAC- LV and PAC-V individually and their mud density, rheological properties, electrical stability and filtration loss properties were determined. The rheological performance showed at higher concentrations of viscosifier, the trend of viscosity increment of PAC performed in a similar way to bentonite. The best result of electrical stability by using the lowest concentration of viscosifier was achieved with PAC-V. The lowest fluid loss volumes were obtained by using the highest concentrations (4 g) of viscosifiers. Mud cake thickness of samples increased by using viscosifiers; however, a lower range was achieved compared to API specification. From the overall experiment, it can be concluded that as the concentrations of viscosifier increase, the viscosity trend increase in a similar way to both PAC-V and bentonite. But we must note that the PAC-V is a more environmentally friendly additive and a renewable resource, cheaper than bentonite and improves properties of eco-friendly OBMs well. It is a preferable choice for oil-based drilling fluids.

Keywords: invert emulsion mud, oil-based mud, rheological properties, viscosifier

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Authors: Maria Alekxandra B. Sison, Reginald C. Mallare, Joseph Albert M. Mendoza

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Ammonia (NH₃) is the alternative carbon-free fuel of the future for its promising applications. Investigations on NH₃-fuel blends recommend using hydrogen (H₂) to increase the heating value of NH3, promote combustion performance, and improve NOx efflux mitigation. To further examine the effects of this concept, the study analyzed the combustion performance, in terms of turbulence, combustion efficiency (CE), and NOx emissions, of NH3/fuel with variations of combustor diameter ratio, H2 fuel mole fraction, and fuel mass flow rate (ṁ). The simulations were performed using Computational Fluid Dynamics (CFD) modeling to represent a non-premixed (NP) and partially premixed (PP) combustion under a two-dimensional ultra-low NOx Rich-Burn, Quick-Quench, Lean-Burn (RQL) combustor. Governed by the Detached Eddy Simulation model, it was found that the diameter ratio greatly affects the turbulence in PP and NP mode, whereas ṁ in PP should be prioritized when increasing CE. The NOx emission is minimal during PP combustion, but NP combustion suggested modifying ṁ to achieve higher CE and Reynolds number without sacrificing the NO generation from the reaction.

Keywords: combustion efficiency, turbulence, dual-stage combustor, NOx emission

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Authors: Mohammad Ali Hasanzadeh, Thierry Van Elslander, Eddy Van De Voorde

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About 90 percent of world merchandise trade by volume being carried by sea. Maritime transport remains as back bone behind the international trade and globalization meanwhile all seaborne goods need using at least two ports as origin and destination. Amid seaborne traded cargos, container traffic is a prosperous market with about 16% in terms of volume. Albeit containerized cargos are less in terms of tonnage but, containers carry the highest value cargos amongst all. That is why efficient handling of containers in ports is very important. Accidents are the foremost causes that lead to port inefficiency and a surge in total transport cost. Having different port safety management systems (PSMS) in place, statistics on port accidents show that numerous accidents occur in ports. Some of them claim peoples’ life; others damage goods, vessels, port equipment and/or the environment. Several accident investigation illustrate that the most common accidents take place throughout transport operation, it sometimes accounts for 68.6% of all events, therefore providing a safer workplace depends on reducing collision risk. In order to quantify risks at the port area different variables can be used as exposure measurement. One of the main motives for defining and using exposure in studies related to infrastructure is to account for the differences in intensity of use, so as to make comparisons meaningful. In various researches related to handling containers in ports and intermodal terminals, different risk exposures and also the likelihood of each event have been selected. Vehicle collision within the port area (10-7 per kilometer of vehicle distance travelled) and dropping containers from cranes, forklift trucks, or rail mounted gantries (1 x 10-5 per lift) are some examples. According to the objective of the current research, three categories of accidents selected for collision risk assessment; fall of container during ship to shore operation, dropping container during transfer operation and collision between vehicles and objects within terminal area. Later on various consequences, exposure and probability identified for each accident. Hence, reducing collision risks profoundly rely on picking the right risk exposures and probability of selected accidents, to prevent collision accidents in container terminals and in the framework of risk calculations, such risk exposures and probabilities can be useful in assessing the effectiveness of safety programs in ports.

Keywords: container terminal, collision, seaborne trade, risk exposure, risk probability

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Authors: Iftikhar Raza

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Well control is the management of the hazardous effects caused by the unexpected release of formation fluid, such as natural gas and/or crude oil, upon surface equipment of oil or gas drilling rigs and escaping into the atmosphere. Technically, oil well control involves preventing the formation fluid, usually referred to as kick, from entering into the wellbore during drilling. Oil well control is one of the most important aspects of drilling operations. Improper handling of kicks in oil well control can result in blowouts with very grave consequences, including the loss of valuable resources. Even though the cost of a blowout (as a result of improper/no oil well control) can easily reach several millions of US dollars, the monetary loss is not as serious as the other damages that can occur: irreparable damage to the environment, waste of valuable resources, ruined equipment, and most importantly, the safety and lives of personnel on the drilling rig. In this paper, case study of a well is discussed with field data showing the properties of the well. The whole procedure of controlling this well is illustrated in this which may be helpful for professional dealing with such kind of problems.

Keywords: kick control, kill sheet, oil well, gas drilling

Procedia PDF Downloads 508

Authors: Orose Rugchati, Kanita Thanacharoenchanaphas, Sarawut Wattanawongpitak

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In this study, the effect of electric stimulation on the quality of hot-boned beef brisket muscles was evaluated, including the tenderness, pH, temperature change, and colorant. Muscles were obtained from steers in the local slaughter house. (3 steers for each muscle), removed from the carcasses 4-hour postmortem and variable time to treated with direct current electric 1 and 5 minutes, respectively. Six different electric intensities (direct current voltage of 50, 70 and 90 Volt, pulse with 10, 20 and 40 ms) plus a control were applied to each muscle to determine the optimum treatment conditions. Hot-boned beef brisket was found to get tender with increasing treatment direct current voltage and reduction in the shear force with pulsed with electric treatment. But in a long time to treated with electric current get fading in red color and temperature increase whereas pH quite different compared to non-treated control samples.

Keywords: electric stimulation, characteristic changes, hot-boned beef brisket, potential tenderness

Procedia PDF Downloads 342

Authors: Kenza Maher, Yahya Zakaria, Noora S. Al-Jaidah

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Temperature is a critical parameter for lithium-ion battery performance, life, and safety. In this study, four commercially available 18650 lithium-ion cells from four different manufacturers are subjected to accelerated cycle aging for up to 500 cycles at two different temperatures (25°C and 45°C). The cells are also calendar-aged at the same temperatures in both charged and discharged states for 6 months to investigate the effect of aging and temperature on capacity fade and state of health. The results showed that all battery cells demonstrated good cyclability and had a good state of health at both temperatures. However, the capacity loss and state of health of these cells are found to be dependent on the cell chemistry and aging conditions, including temperature. Specifically, the capacity loss is found to be higher at the higher aging temperature, indicating the significant impact of temperature on the aging of lithium-ion batteries.

Keywords: lithium-ion battery, aging mechanisms, cycle aging, calendar aging.

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Authors: Ali Kadivar, Kaveh Niayesh

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MVDC markets for green power generations, Navy, subsea oil and gas electrification, and transportation electrification are extending rapidly. The lack of fast and powerful DC circuit breakers (CB) is the most significant barrier to realizing the medium voltage DC (MVDC) networks. A concept of hybrid circuit breakers (HCBs) benefiting from ultrafast disconnectors (UFD) is proposed. A set of mechanical switches substitute the power electronic commutation switches to reduce the losses during normal operation in HCB. The success of current commutation in such breakers relies on the behaviour of elongated, wall constricted arcs during the opening across the contacts inside the UFD. The arc voltage dependencies on the contact speed of UFDs is discussed through multiphysics simulations contact opening speeds of 10, 20 and 40 m/s. The arc voltage at a given current increases exponentially with the contact opening velocity. An empirical equation for the dynamic arc characteristics is presented for the tested UFD, and the experimentally verfied characteristics for voltage-current are utilized for the current commutation simulation prior to apply on a 14 kV experimental setup. Different failures scenarios due to the current commutation are investigated

Keywords: MVDC breakers, DC circuit breaker, fast operating breaker, ultra-fast elongated arc

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Authors: Samia Hachemi, Abdelhafid Ounis, W. Heriheri

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This paper presents an experimental investigation of high temperatures applied to normal and high performance concrete made with natural coarse aggregates. The experimental results of physical and mechanical properties were compared with those obtained with recycled brick aggregates produced by replacing 30% of natural coarse aggregates by recycled brick aggregates. The following parameters: compressive strength, concrete mass loss, apparent density and water porosity were examined in this experiment. The results show that concrete could be produced by using recycled brick aggregates and reveals that at high temperatures recycled aggregate concrete preformed similar or even better than natural aggregate concrete.

Keywords: high temperature, compressive strength, mass loss, recycled brick aggregate

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Authors: S. Nigri, R. Oumeddour, F. Djazi

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The inhibition of the corrosion of copper in 1 M HNO3 solution by oleic acid was investigated by weight loss measurement, potentiodynamic polarization and scanning electron microscope (SEM) studies. The experimental results have showed that this compound revealed a good corrosion inhibition and the inhibition efficiency is increased with the inhibitor concentration to reach 98%. The results obtained revealed that the adsorption of the inhibitor molecule onto metal surface is found to obey Langmuir adsorption isotherm. The temperature effect on the corrosion behavior of copper in 1 M HNO3 without and with inhibitor at different concentration was studied in the temperature range from 303 to 333 K and the kinetic parameters activation such as Ea, ∆Ha and ∆Sa were evaluated. Tafel plot analysis revealed that oleic acid acts as a mixed type inhibitor. SEM analysis substantiated the formation of protective layer over the copper surface.

Keywords: oleic acid, weight loss, electrochemical measurement, SEM analysis

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Authors: Sukhvinder Singh

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Punjabi language is related to the languages of New Indo-Aryan group that, in turn, is related to the branch of Indo-European language family. Punjabi language covers the areas of Western part (that is in Pakistan) and Eastern part (the Punjab state, Haryana, Delhi Himachal and J&K) and abroad (particularly Canada, USA, U.K. and Arab Emirates), where it is spoken widely. Besides India and Pakistan, Punjabi is the third language spoken in Canada after English, French having more than one hundred millions speakers worldwide. It is the fourth language spoken in Canada after English, French, and Chinese. It is also being taught as second language in most of the community school of British Columbia. The total number of Punjabi speakers is more than one hundred millions including India, Pakistan and abroad. Punjabi has a long tradition of linguistic tradition. A large number of scholars have studied Punjabi at different linguistic levels. Various studies are devoted to its special phonological characteristics, especially the tone, which has now started disappearing in favour of aspiration, a rare example of a language change in progress in its reversal direction. This process of language change in progress in reversal is dealt with in this paper a change towards a loss of linguistic indigeneity. The tone being a distinctive linguistic feature of Punjabi language is getting lost due to the increasing influence of Hindi and English particularly in the speech Urban Punjabi and Punjabi settled abroad. In this paper, an attempt has been made to discuss the sociolinguistics and sociology of Punjabi language and Punjab to trace the initiation and progression of this change towards a loss of Linguistic Indigeneity.

Keywords: language change in reversal, reaspiration, detonalization, new Indo-Aryan group

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Authors: G .D. B. N. Kulasaooriya, H. B. S. Ariyarathne, I. Abeygunawardene, A. A. J. Rafarathne, B. V. Perera

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Elephant is the largest resident of the wild and has small surface to volume ratio as well as less number of sweat glands which cause challenges to the thermoregulation of this mammal. However, this megaherbivore has adopted specialised meachanisms to maintain its thermal balance through behavioral adaptations, ear flapping and well anastomosed arterioles and venules of the ear. Nevertheless, little is known on the involvement of the skin in the process of thermoregulation. The present study was undertaken to monitor the water evaporation rate from the skin of unrestrained wild elephant calves throughout the day and to understand its importance in the thermoregulation. Seven baby elephants housed in the elephant transit home, Udawalawe were used. Ambient temparature, relative humidity (RH) and radiation heat load was monitored throughout the day of the study period. Similarly, surface temparature of the skin was taken at six points including lateral ear pinna, lateral body and the rump during the same period. The skin water evaporation was also measured from the same sites using cobolt chloride method. The surface are of the skin was determined by assigning geometrical shapes to each body part. The results showed that the ambient temperature gradually increased with the day reaching maximum around 3.00 pm. The relative humidity was lowest early in the morning. The radiation heat load did not show any significant change in the study period. The skin temperature was different among lateral ear pinna, lateral body and the rump where the highest temperature was on the rump and the lowest on the lateral ear pinna. The skin temperature gradually increase with increasing ambient temperature but there was not a strong correlation (R2 =53.53) between these two. The skin temperature had strong correlation with RH (p<0.05 R2 =70.84% ) but a significant relationship was not considered since the radiation heat load was not varying in large scale. The skin evaporative water loss had a weak negative correlation with ambient temperature (correlation coefficient= -0.01) whereas strong positive correlation with RH (correlation coefficient= 25.275 ) and no corelation with radiation heat load. It also appeared that skin water loss increases as the skin temperature increased. In the present study, it was observed that on average, skin of the baby elephant looses 403 g/m2/h of water. Based on these observations it can be concluded that a large volume of water is evaporated from the skin of baby elephants and evaporative heat loss may be contributing significantly to the thermoregulation. However, further investigation on the influence of environmental factors on evaporative heat loss has to be conducted to understand the thermoregulatory mechanisms of the baby elephant.

Keywords: thermoregulation, behavioral adaptations, evaporation, elephant

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Authors: X. F. Sun, X. D. Wen, L. J. Liu, C. C. Wu, Y. H. Jia

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The field reversed closed magnetic field configuration plasmoid has a potential for large thrust and high power propulsion missions such as deep space exploration due to its high plasma density and larger azimuthal current, which will be a most competitive program for the next generation electric propulsion technology. Moreover, without the electrodes, it also has a long lifetime. Thus, the research on this electric propulsion technology is quite necessary. The plasmoid will be formatted and accelerated by applying a rotation magnetic field (RMF) method. And, the essence of this technology lies on the generation of the azimuthal electron currents driven by RMF. Therefore, the effect of RMF current on the plasmoid acceleration efficiency is a concerned problem. In the paper, the influences of the penetration process of RMF in plasma, the relations of frequency and amplitude of input RF power with current strength and the RMF antenna configuration on the plasmoid acceleration efficiency will be given by a two-fluid numerical simulation method. The results show that the radio-frequency and input power have remarkable influence on the formation and acceleration of plasmoid. These results will provide useful advice for the development, and optimized designing of field reversed configuration plasmoid thruster.

Keywords: rotation magnetic field, current driven, plasma penetration, electric propulsion

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Authors: Yakup Sahin, Naim Suleyman Ting, Ismail Aksoy

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In this paper, an improved active snubber cell is proposed on account of soft switching (SS) family of pulse width modulation (PWM) DC-DC converters. The improved snubber cell provides zero-voltage transition (ZVT) turn on and zero-current transition (ZCT) turn off for main switch. The snubber cell decreases EMI noise and operates with SS in a wide range of line and load voltages. Besides, all of the semiconductor devices in the converter operate with SS. There is no additional voltage and current stress on the main devices. Additionally, extra voltage stress does not occur on the auxiliary switch and its current stress is acceptable value. The improved converter has a low cost and simple structure. The theoretical analysis of converter is clarified and the operating states are given in detail. The experimental results of converter are obtained by prototype of 500 W and 100 kHz. It is observed that the experimental results and theoretical analysis of converter are suitable with each other perfectly.

Keywords: active snubber cells, DC-DC converters, zero-voltage transition, zero-current transition

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Authors: Buddhiprabha D. D. Pathirana

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Despite a rapid increase in the number of school counselors in the recent past; procuring the service of school counselors is a luxury that many Sri Lankan schools cannot afford. In addition, school counseling in Sri Lanka also faces new challenges in implementation due to the fact that a generally agreed consensus on training, ethical standards, role identity, counseling model, and structures for school counselors has not been reached. Therefore, this paper has several objectives. First, it reviews a brief history of school counseling in Sri Lanka and describes its current status. Second, it describes current trends/ problems specific to Sri Lankan school counseling milieu which have limited the progress of school counseling as a practice. Third, it discusses societal and cultural issues that are important to consider when implementing school counseling as a practices in Sri Lanka and provides recommendations to improve it.

Keywords: school counseling, Sri Lanka, current situation, recommendations

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Authors: Pradeep Raj Sharma, Bogeun Jang, Jongill Hong

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Spin-orbit torque (SOT) is an efficient approach for manipulating the magnetization of ferromagnetic materials (FMs), providing improved device performance, better compatibility, and ultra-fast switching with lower power consumption compared to spin-transfer torque (STT). Among the various materials and structural designs, two-dimensional (2D) van-der Waals (vdW) layered materials and their heterostructures have been demonstrated as highly scalable and promising device architecture for SOT. In particular, a bilayer heterostructure consisting of fully 2D-vdW-FM, non-magnetic material (NM) offers a potential platform for controlling the magnetization using SOT because of the advantages of being easy to scale and less energy to switch. Here, we report filed-free deterministic switching driven by SOT at room temperature, integrating perpendicularly magnetized 2D-vdW material Fe₃GaTe₂ (FGaT) and NM WTe₂. Pulse current-induced magnetization switching with an ultra-low current density of about 6.5×10⁵ A/cm², yielding a SOT efficiency close to double-digits at 300 K, is reported. These values are two orders of magnitude higher than those observed in conventional heavy metal (HM) based SOT and exceed those reported with 2D-vdW layered materials. WTe₂, a topological semimetal possessing strong SOC and high spin Hall angle, can induce significant spin accumulation with negligible spin loss across the transparent 2D bilayer heterointerface. This promising device architecture enables highly compatible, energy-efficient, non-volatile memory and lays the foundation for designing efficient, flexible, and miniaturized spintronic devices.

Keywords: spintronics, spin-orbit torque, spin Hall effect, spin Hall angle, topological semimetal, perpendicular magnetic anisotropy

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Authors: Marco Camilli

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This article examines the impact of the pandemic outbreak of COVID-19 in the tourism sector in Italy, analyzing the current scenario, the government decisions and the private company reaction for the summer season 2020. The framework of the data analyzed shows how massive it’s the impact of the pandemic outbreak in the tourism revenue, and the weaknesses of the measures proposed. Keywords Travel &Tourism, Transportation, Sustainability, COVID-19, Businesses Introduction The current COVID-19 scenario shows a shocking situation for the tourism and transportation sectors: it could be the most affected by the Coronavirus in Italy. According to forecasts, depending on the duration of the epidemic outbreak and the lockdown strategy applied by the Government, businesses in the supply chain could lose between 24 and 66 billion in turnover in the period of 2020-21, with huge diversified impacts at the national and regional level. Many tourist companies are on the verge of survival and if there are no massive measures by the government they risk closure. Data analysis The tourism and transport sector could be among the sectors most damaged by Covid-19 in Italy. Considering the two-year period 2020-21, companies operating in the travel & tourism sector (Tour operator, Travel Agencies, Hotel, Guides, Bus Company, etc..) could in suffer losses in revenues of 24 to 64 billion euros, especially in the sectors such as the travel agencies, hotel and rental. According to Statista Research Department, from April 2020 estimated that the coronavirus (COVID-19) pandemic will have a significant impact on revenues of the tourism industry in Italy. Revenues are expected to decrease by over 40 billion euros in the first semester of 2020, compared to the same period of the previous year. According to the study, hotel and non-hotel accommodations will experience the highest loss. Revenues of this sector are expected to decrease by 13 billion euros compared to the first semester of 2019 when accommodations registered revenues for about 17 billion euros. According to Statista.com, in 2020, Italy is expected to register a decrease of roughly 28.5 million tourist arrivals due to the impact of coronavirus (COVID-19) on the country's tourist sector. According to the estimate, the region of Veneto will record the highest drop with a decrease of roughly 4.61 million arrivals. Similarly, Lombardy is expected to register a decrease of about 3.87 million arrivals in 2020.

Keywords: travel and tourism, sustainability, COVID-19, businesses, transportation

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Authors: Jonas Kahlert

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Blockchain technology has gained importance and momentum in the energy sector. Yet, there is no structured analysis of how specific features of the blockchain technology can create value in the energy sector. We employ a qualitative analysis on insights gained from the current literature and expert interviews. Along the four most prevalent use cases of blockchain technology in the energy sector, we discuss the potential of blockchain technology to support a transition to a more affordable, sustainable and reliable energy system. We show that in its current state, blockchain and adjacent technologies are not a necessity but a sufficiency towards this transition. We also show how current limitations of the blockchain and adjacent technologies can be even counterproductive. Finally, we discuss implications for policy makers and managers.

Keywords: blockchain technology, affordance theory, energy trilemma, sustainability

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Authors: Khalid Bashir, Hammad Zahid

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Most of the investors consider that economic and financial information is the most important at the time of making investment decisions. But it is not true, as in the past two decades, the Behavioral aspects and the behavioral biases have gained an important place in the decision-making process of an investor. This study is basically conducted on this fact. The purpose of this study is to examine the impact of behavioral factors on the decision-making of the individual real estate investor in Pakistan. Some important behavioral factors like overconfidence, anchoring, gambler’s fallacy, home bias, loss aversion, regret aversion, mental accounting, herding and representativeness are used in this study to find their impact on the psychology of individual investors. The targeted population is the real estate investor of Pakistan, and a sample of 650 investors is selected on the basis of convenience sampling technique. The data is collected through the questionnaire with a response rate of 46.15 %. Descriptive statistical techniques and SEM are used to analyze the data by using statistical software. The results revealed the fact that some behavioral factors have a significant impact on the decision-making of investors. Among all the behavioral biases, overconfidence, anchoring, gambler’s fallacy, loss aversion and representativeness have a significant positive impact on the decision-making of the individual investor, while the rest of biases like home bias, regret aversion, mental accounting, herding have less impact on the decision-making process of an individual.

Keywords: behavioral finance, anchoring, gambler’s fallacy, loss aversion

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Authors: Olga Koutsika

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The paper deals primarily with the question of the legal framework of non-orbital flights. The submission is based upon two pillars, starting with the ill-defined current legal regime and proceeding to further recommendations for the prospective legal regime for non-orbital flights. For this reason, the paper focuses on certain key legal aspects of the topic, including among other things liability, responsibility, jurisdiction, registration and authorisation. Furthermore, taking into consideration the hybrid nature of both the craft conducting non-orbital flights and of the flights themselves, which exit airspace but do not enter an orbit in outer space, the paper addresses each legal question from the perspective of both air law and space law and concludes to a number of recommendations regarding the applicability of each legal regime for each legal question individually.

Keywords: current regime, legal framework, non-orbital flights, prospective regime

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Authors: A. Benhadji, M. Taleb Ahmed

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Among the various methods of treatment, advanced oxidation processes (AOP) are the most promising ones. In this study, Peroxi Electrocoagulation Process (PEP) was investigated for the treatment of detergent wastewater. The process was compared with electrooxidation treatment. The results showed that chemical oxygen demand (COD) was high 7584 mgO₂.L^-1, while the biochemical oxygen demand was low (250 mgO₂.L^-1). This wastewater was hardly biodegradable. Electrochemical process was carried out for the removal of detergent using a glass reactor with a volume of 1 L and fitted with three electrodes. A direct current (DC) supply was used. Samples were taken at various current density (0.0227 A/cm² to 0.0378 A/cm²) and reaction time (1-2-3-4 and 5 hour). Finally, the COD was determined. The results indicated that COD removal efficiency of PEP was observed to increase with current intensity and reached to 77% after 5 h. The highest removal efficiency was observed after 5 h of treatment.

Keywords: AOP, COD, detergent, PEP, wastewater

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Authors: Ecem Deniz Kırkpantur, Ozge Ecmel Onur, Tuba Cimilli Ozturk, Ebru Unal Akoglu

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Moyamoya disease is a unique chronic progressive cerebrovascular disease characterized by bilateral stenosis or occlusion of the arteries around the circle of Willis with prominent arterial collateral circulation. The occurrence of Moyamoya disease is related to immune, genetic and other factors. There is no curative treatment for Moyamoya disease. Secondary prevention for patients with symptomatic Moyamoya disease is largely centered on surgical revascularization techniques. We present here a 62-year old male presented with headache and vision loss for 2 days. He was previously diagnosed with hypertension and glaucoma. On physical examination, left eye movements were restricted medially, both eyes were hyperemic and their movements were painful. Other neurological and physical examination were normal. His vital signs and laboratory results were within normal limits. Computed tomography (CT) showed dilated vascular structures around both lateral ventricles and atherosclerotic changes inside the walls of internal carotid artery (ICA). Magnetic resonance imaging (MRI) and angiography (MRA) revealed dilated venous vascular structures around lateral ventricles and hyper-intense gliosis in periventricular white matter. Ischemic gliosis around the lateral ventricles were present in the Digital Subtracted Angiography (DSA). After the neurology, ophthalmology and neurosurgery consultation, the patient was diagnosed with Moyamoya disease, pulse steroid therapy was started for vision loss, and super-selective DSA was planned for further investigation. Moyamoya disease is a rare condition, but it can be an important cause of stroke in both children and adults. It generally affects anterior circulation, but posterior cerebral circulation may also be affected, as well. In the differential diagnosis of acute vision loss, occipital stroke related to Moyamoya disease should be considered. Direct and indirect surgical revascularization surgeries may be used to effectively revascularize affected brain areas, and have been shown to reduce risk of stroke.

Keywords: headache, Moyamoya disease, stroke, visual loss

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