Search results for: firing temperature

Authors: Rahmat Ali, Inamullah Khan, Amjad Naseer, Abid A. Shah

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Hydronic Heating and Cooling systems in concrete slab based buildings are increasingly becoming a popular substitute to conventional heating and cooling systems. In exploring the materials, techniques employed, and their relative performance measures, a fair bit of uncertainty exists. This research has identified the simplest method of determining the thermal field of a single hydronic pipe when acting as a part of a concrete slab, based on which the spacing and positioning of pipes for a best thermal performance and surface temperature control are determined. The pipe material chosen is the commonly used PEX pipe, which has an all-around performance and thermal characteristics with a thermal conductivity of 0.5W/mK. Concrete Test samples were constructed and their thermal fields tested under varying input conditions. Temperature sensing devices were embedded into the wet concrete at fixed distances from the pipe and other touch sensing temperature devices were employed for determining the extent of the thermal field and validation studies. In the first stage, it was found that the temperature along a specific distance was the same and that heat dissipation occurred in well-defined layers. The temperature obtained in concrete was then related to the different control parameters including water supply temperature. From the results, the temperature of water required for a specific temperature rise in concrete is determined. The thermally effective area is also determined which is then used to calculate the pipe spacing and positioning for the desired level of thermal comfort.

Keywords: thermally activated building systems, concrete slab temperature, thermal field, energy efficiency, thermal comfort, pipe spacing

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Authors: Taejung Lho, Jonghwan Lee

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Most of the photovoltaic (PV) module manufacturers have recently interested in reducing the manufacturing cost. One of available solution is the use of the thin photovoltaic cell because of reducing of raw material cost. Thin PV cells, however, are damaged large deformation which causes possible microcracks inside PV cell, leading to failure problem. In this paper, deformation characteristics by heat conduction in soldering process of PV cells are analyzed through ANSYS software tool. They have been tested for different PV cell thickness and soldering temperature profile. Accordingly optimal soldering process to minimize the deformation of PV cell has been suggested.

Keywords: photovoltaic (PV) cell, infrared(IR) lamp soldering, optimal soldering temperature profile, deformation, temperature distribution, 3D scanner, ANSYS

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Authors: V. Prasannavenkadesan, A. Elango, S. Chockalingam

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During machining process, chatter is an unavoidable phenomenon. Boring bars possess the cantilever shape and due to this, it is subjected to chatter. The adverse effect of chatter includes the increase in temperature which will leads to excess tool wear. To overcome these problems, in this investigation, Cartridge brass (Cu – 70% and Zn – 30%) is passively fixed on the boring bar and also clearance is provided in order to reduce the displacement, tool wear and cutting temperature. A conventional all geared lathe is attached with vibrometer and pyrometer is used to measure the displacement and temperature. The influence of input parameters such as cutting speed, depth of cut and clearance on temperature, tool wear and displacement are investigated for various cutting conditions. From the result, the optimum conditions to obtain better damping in boring process for chatter reduction is identified.

Keywords: boring, chatter, mass damping, passive damping

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Authors: M. Riaz, Inamur Rehman, Abhishek Sharma

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The present work is the development of an experimental method for determining the thermal diffusivity variations with temperature of selected regular shaped solid fruits and vegetables subjected to forced convection cooling. Experimental investigations were carried on the sample chosen (potato and brinjal), which is approximately of spherical geometry. The variation of temperature within the food product is measured at several locations from centre to skin, under forced convection environment using a deep freezer, maintained at -10°C.This method uses one dimensional Fourier equation applied to regular shapes. For this, the experimental temperature data obtained from cylindrical and spherical shaped products during pre-cooling was utilised. Such temperature and thermal diffusivity profiles can be readily used with other information such as degradation rate, etc. to evaluate thermal treatments based on cold air cooling methods for storage of perishable food products.

Keywords: thermal diffusivity, skin temperature, precooling, forced convection, regular shaped

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Authors: Jyh Jyh Chen, Fu H. Yang, Chen W. Wang, Yu M. Lin

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In this work, a reaction chamber is reciprocated among three temperature regions by using an oscillatory thermal cycling machine. Three cartridge heaters are collocated to heat three aluminum blocks in order to achieve PCR requirements in the reaction chamber. The effects of various chamber moving speeds among different temperature regions on the chamber temperature profiles are presented. To solve the evaporation effect of the sample in the PCR experiment, the mineral oil and the cover lid are used. The influences of various extension times on DNA amplification are also demonstrated. The target fragments of the amplification are 385-bp and 420-bp. The results show when the forward speed is set at 6 mm/s and the backward speed is 2.4 mm/s, the temperature required for the experiment can be achieved. It is successful to perform the amplification of DNA fragments in our device.

Keywords: oscillatory, polymerase chain reaction, reaction chamber, thermal cycling machine

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Authors: Sarayu Vanga, Jorge Galeano-Cabral, Kaya Wei

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Cerebral hypoxia refers to a condition in which there is a decrease in oxygen supply to the brain. Patients suffering from this condition experience a decrease in their body temperature. While there isn't any cure to treat cerebral hypoxia as of date, certain procedures are utilized to help aid in the treatment of the condition. Regulating the body temperature is an example of one of those procedures. Hypoxia is well known to reduce the body temperature of mammals, although the neural origins of this response remain uncertain. In order to speed recovery from this condition, it is necessary to maintain a stable body temperature. In this study, we present an approach to regulating body temperature for patients who suffer from cerebral hypoxia or other similar conditions. After a thorough literature study, we propose the use of thermoelectric blankets, which are temperature-controlled thermal blankets based on thermoelectric devices. These blankets are capable of heating up and cooling down the patient to stabilize body temperature. This feature is possible through the reversible effect that thermoelectric devices offer while behaving as a thermal sensor, and it is an effective way to stabilize temperature. Thermoelectricity is the direct conversion of thermal to electrical energy and vice versa. This effect is now known as the Seebeck effect, and it is characterized by the Seebeck coefficient. In such a configuration, the device has cooling and heating sides with temperatures that can be interchanged by simply switching the direction of the current input in the system. This design integrates various aspects, including a humidifier, ventilation machine, IV-administered medication, air conditioning, circulation device, and a body temperature regulation system. The proposed design includes thermocouples that will trigger the blanket to increase or decrease a set temperature through a medical temperature sensor. Additionally, the proposed design allows an efficient way to control fluctuations in body temperature while being cost-friendly, with an expected cost of 150 dollars. We are currently working on developing a prototype of the design to collect thermal and electrical data under different conditions and also intend to perform an optimization analysis to improve the design even further. While this proposal was developed for treating cerebral hypoxia, it can also aid in the treatment of other related conditions, as fluctuations in body temperature appear to be a common symptom that patients have for many illnesses.

Keywords: body temperature regulation, cerebral hypoxia, thermoelectric, blanket design

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Authors: Fikret Yalcinkaya, Hamza Unsal

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To understand how neurons work, it is required to combine experimental studies on neural science with numerical simulations of neuron models in a computer environment. In this regard, the simplicity and applicability of spiking neuron modeling functions have been of great interest in computational neuron science and numerical neuroscience in recent years. Spiking neuron models can be classified by exhibiting various neuronal behaviors, such as spiking and bursting. These classifications are important for researchers working on theoretical neuroscience. In this paper, three different spiking neuron models; Izhikevich, Adaptive Exponential Integrate Fire (AEIF) and Hindmarsh Rose (HR), which are based on first order differential equations, are discussed and compared. First, the physical meanings, derivatives, and differential equations of each model are provided and simulated in the Matlab environment. Then, by selecting appropriate parameters, the models were visually examined in the Matlab environment and it was aimed to demonstrate which model can simulate well-known biological neuron behaviours such as Tonic Spiking, Tonic Bursting, Mixed Mode Firing, Spike Frequency Adaptation, Resonator and Integrator. As a result, the Izhikevich model has been shown to perform Regular Spiking, Continuous Explosion, Intrinsically Bursting, Thalmo Cortical, Low-Threshold Spiking and Resonator. The Adaptive Exponential Integrate Fire model has been able to produce firing patterns such as Regular Ignition, Adaptive Ignition, Initially Explosive Ignition, Regular Explosive Ignition, Delayed Ignition, Delayed Regular Explosive Ignition, Temporary Ignition and Irregular Ignition. The Hindmarsh Rose model showed three different dynamic neuron behaviours; Spike, Burst and Chaotic. From these results, the Izhikevich cell model may be preferred due to its ability to reflect the true behavior of the nerve cell, the ability to produce different types of spikes, and the suitability for use in larger scale brain models. The most important reason for choosing the Adaptive Exponential Integrate Fire model is that it can create rich ignition patterns with fewer parameters. The chaotic behaviours of the Hindmarsh Rose neuron model, like some chaotic systems, is thought to be used in many scientific and engineering applications such as physics, secure communication and signal processing.

Keywords: Izhikevich, adaptive exponential integrate fire, Hindmarsh Rose, biological neuron behaviours, spiking neuron models

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Authors: Hamed Rahmati

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Nowadays, increasing demand for electric energy makes applying high-temperature superconductors inevitable. However, the most important problem of the superconductors is their critical temperature, which necessitates using a cryogenic system for keeping these substances’ temperatures lower than the critical level. Cryogenic systems used for this reason are not efficient enough, and keeping these large systems maintained is costly. Moreover, the low critical temperature of superconductors has delayed using them in electrical equipment. In this article, at first, characteristics of three superconductors, magnesium diboride (MgB2), yttrium barium copper oxide (YBCO), and iron-based superconductors (FeSC), have been analyzed and a new structure of YBCO superconductors is presented. Generally, YBCO (YBa2Cu7O2) has a weak mechanical structure. By introducing some changes in its configuration and adding one silver atom (Ag) to it, its mechanical characteristics improved significantly. Moreover, for each added atom, a star-form structure was introduced in which changing the location of Ag atom led to considerable changes in temperature. In this study, Ag has been added by applying two accurate methods named random and substitute ones. The results of both methods have been examined. It has been shown that adding Ag by applying the substitute method can improve the mechanical properties of the superconductor in addition to increasing its critical temperature. In the mentioned strategy (using the substitute method), the critical temperature of the superconductor was measured up to 99 Kelvin. This new structure is usable in designing superconductors’ rings to be applied in superconducting magnetic energy storage (SMES). It can also lead to a reduction in the cryogenic system size, a decline in conductor wastes, and a decrease in costs of the whole system.

Keywords: critical temperature, cryogenic system, high-temperature superconductors, YBCO

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Authors: Arseniy M. Kondratyev, Sergey V. Onufriev, Alexander I. Savvatimskiy

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The microsecond electrical pulse heating technique which provides uniform energy input into an investigated specimen is considered. In the present study we investigated ZrC+C carbide specimens in a form of a thin layer (about 5 microns thick) that were produced using a method of magnetron sputtering on insulating substrates. Specimens contained (at. %): Zr–17.88; C–67.69; N–8.13; O–5.98. Current through the specimen, voltage drop across it and radiation at the wavelength of 856 nm were recorded in the experiments. It enabled us to calculate the input energy, specific heat (from 2300 to 4500 K) and resistivity (referred to the initial dimensions of a specimen). To obtain the true temperature a black body specimen was used. Temperature of the beginning and completion of a phase transition (solid–liquid) was measured.Temperature of the onset of melting was 3150 K at the input energy 2.65 kJ/g; temperature of the completion of melting was 3450 K at the input energy 5.2 kJ/g. The specific heat of the solid phase of investigated carbide calculated using our data on temperature and imparted energy, is close to 0.75 J/gК for temperature range 2100–2800 K. Our results are considered together with the equilibrium Zr-C phase diagram.

Keywords: pulse heating, zirconium carbide, high temperatures, melting

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Authors: E. Moroydor Derun, N. Tugrul, N. Baran Acarali, A. S. Kipcak, S. Piskin

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Fly ash is a waste material of coal firing thermal plants that is released from thermal power plants. It was defined as very fine particles that are drifted upward which are taken up by the flue gases. The emerging amount of fly ash in the world is approximately 600 million tons per year. In our country, it is expected that will be occurred 50 million tons of waste ash per year until 2020. The fly ashes can be evaluated by using as adsorbent material. The purpose of this study is to investigate the possibility of use of various fly ashes (Tuncbilek, Catalagzi, Orhaneli) like low-cost adsorbents for heavy metal adsorption. First of all, fly ashes were characterized. For this purpose; analyses such as XRD, XRF, SEM and FT-IR were performed.

Keywords: adsorbent, fly ash, heavy metal, waste

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Authors: Ruyang Ren, Yaohua Zhao, Yanhua Diao

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The intermittent and unstable characteristics of renewable energy such as solar energy can be effectively solved through battery energy storage system. Lithium-ion battery is widely used in battery energy storage system because of its advantages of high energy density, small internal resistance, low self-discharge rate, no memory effect and long service life. However, the performance and service life of lithium-ion battery is seriously affected by its operating temperature. Thus, the safety operation of the lithium-ion battery module is inseparable from an effective thermal management system (TMS). In this study, a new type of TMS based on micro heat pipe array (MHPA) for lithium-ion battery is established, and the TMS is applied to a battery energy storage box that needs to operate at a high temperature environment of 40 °C all year round. MHPA is a flat shape metal body with high thermal conductivity and excellent temperature uniformity. The battery energy storage box is composed of four battery modules, with a nominal voltage of 51.2 V, a nominal capacity of 400 Ah. Through the excellent heat transfer characteristics of the MHPA, the heat generated by the charge and discharge process can be quickly transferred out of the battery module. In addition, if only the MHPA cannot meet the heat dissipation requirements of the battery module, the TMS can automatically control the opening of the external fan outside the battery module according to the temperature of the battery, so as to further enhance the heat dissipation of the battery module. The thermal management performance of lithium-ion battery TMS based on MHPA is studied experimentally under different ambient temperatures and the condition to turn on the fan or not. Results show that when the ambient temperature is 40 °C and the fan is not turned on in the whole charge and discharge process, the maximum temperature of the battery in the energy storage box is 53.1 °C and the maximum temperature difference in the battery module is 2.4 °C. After the fan is turned on in the whole charge and discharge process, the maximum temperature is reduced to 50.1 °C, and the maximum temperature difference is reduced to 1.7 °C. Obviously, the lithium-ion battery TMS based on MHPA not only could control the maximum temperature of the battery below 55 °C, but also ensure the excellent temperature uniformity of the battery module. In conclusion, the lithium-ion battery TMS based on MHPA can ensure the safe and stable operation of the battery energy storage box in high temperature environment.

Keywords: heat dissipation, lithium-ion battery thermal management, micro heat pipe array, temperature uniformity

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Authors: Ruby Siwach, Manish Kumar, Raman Seth

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Extent of inactivation of pectin methylesterase (PME) in mosambi juice during thermal and thermosonication treatments was studied to obtain a minimally processed product. Effect of both treatments on cloud value, pH, titratable acidity, oBrix, and sensory attributes (flavour and taste) was studied. Thermal treatments (HT) were carried out at three temperatures 60, 70, and 80°C in a serological water bath for 5, 10, 15, and 20 min at each temperature. Thermosonication treatments (TS) were also given for same time-temperature combinations in water bath of a thermosonicator. Treated samples were stored in a deep freezer at 18°C for PME assay. PME activity of untreated sample was also assayed and residual PME activity and % loss in PME activity was calculated at each time-temperature combination. The extent of inactivation of PME increased with increase in treatment temperature and duration. Thermosonication treatments were found far more effective than thermal treatments of same time temperature combination in PME inactivation and retention of sensory attributes.

Keywords: pectin methylesterase, heat inactivation kinetics, thermosonication, thermal treatment

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Authors: M. Jalali Azizpour

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In this paper, the effect of WC-12Co particle Temperature in HVOF thermal spraying process on the coating thickness has been studied. The statistical results show that the spray distance and oxygen-to-fuel ratio are more effective factors on particle characterization and thickness of HVOF thermal spraying coatings. Spray Watch diagnostic system, scanning electron microscopy (SEM), X-ray diffraction and thickness measuring system were used for this purpose.

Keywords: HVOF, temperature thickness, velocity, WC-12Co

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Authors: D. Latha, V. Sunitha, Samson Mathew

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In India, most of the pavement is laid by bituminous road and the consumption of binder is high for pavement construction and also modified binders are used to satisfy any specific pavement requirement. Since the binders are visco-elastic material which is having the mechanical properties of binder transition from visco-elastic solid to visco-elastic fluid. In this paper, two different protocols were used to measure the viscosity property of binder using a Brookfield Viscometer and there is a need to find the appropriate mixing and compaction temperatures of various types of binders which can result in complete aggregate coating and adequate field density of HMA mixtures. The aim of this work is to find the transition temperature from Non-Newtonian behavior to Newtonian behavior of the binder by adopting a steady shear protocol and the shear rate ramp protocol. The transition from non-Newtonian to Newtonian can occur through an increase of temperature and shear of the material. The test has been conducted for unmodified binder VG 30. The transition temperature was found in the unmodified binder VG is 120oC. So the application of both modified binder and unmodified binder in the pavement construction needs to be studied properly by considering temperature and traffic loading factors of the respective project site.

Keywords: unmodified and modified binders, Brookfield viscometer, transition temperature, steady shear and shear rate protocol

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Authors: Mohammed Aliyu, Kazunori Iwabuchi, Ibrahim Shaba Mohammed, Abubakar Sadeeq Mohammed, Solomon Musa Dauda, Zinash Delebo Osunde

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Hydrothermal carbonization (HTC) is recognised as a low temperature and effective technique for the conversion of biomass to solid biofuel. In this study, the effect of process temperature and biomass-to-water ratio (B/W) on the fuel properties of hydrochar produced from wood shavings was investigated. HTC was conducted in an autoclave using reaction temperature of 230 °C and 260 °C for 20 minutes with B/W ratio of 0.11 to 0.43. The produced hydrochars were characterised by the mass yield (MY), higher heating value (HHV), proximate and ultimate properties. The results showed that the properties of the hydrochars improved with increasing process temperature and B/W ratio. The higher heating value (HHV) increased to 26.74 MJ/kg as the severity of the reaction was increased to the process temperature of 260 °C. Also, the atomic H/C and O/C ratios of hydrochars produced at 230 °C and 260 °C were closed to the regions of a peat and lignite on the plotted van Krevelen diagram. Hence, the produced hydrochar has a promising potential as a sustainable solid biofuel for energy application.

Keywords: wood shavings, biomass/water ratio, thermochemical conversion, hydrothermal carbonization, hydrochar

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Authors: Magdi M. Nabi, Ding-Li Yu

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This paper presents a neural network based model predictive control (MPC) strategy to control a strongly exothermic reaction with complicated nonlinear kinetics given by Chylla-Haase polymerization reactor that requires a very precise temperature control to maintain product uniformity. In the benchmark scenario, the operation of the reactor must be guaranteed under various disturbing influences, e.g., changing ambient temperatures or impurity of the monomer. Such a process usually controlled by conventional cascade control, it provides a robust operation, but often lacks accuracy concerning the required strict temperature tolerances. The predictive control strategy based on the RBF neural model is applied to solve this problem to achieve set-point tracking of the reactor temperature against disturbances. The result shows that the RBF based model predictive control gives reliable result in the presence of some disturbances and keeps the reactor temperature within a tight tolerance range around the desired reaction temperature.

Keywords: Chylla-Haase reactor, RBF neural network modelling, model predictive control, semi-batch reactors

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Authors: S. K. Fasogbon, O. E. Oguegbu

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Pasteurization is one of the most important steps in the preservation of beer products, which improves its shelf life by inactivating almost all the spoilage organisms present in it. However, there is no gain saying the fact that it is always difficult to determine the slowest heating zone, the temperature profile and pasteurization units inside bottled beer during pasteurization, hence there had been significant experimental and ANSYS fluent approaches on the problem. This work now developed Computational fluid dynamics model using COMSOL Multiphysics. The model was simulated to determine the slowest heating zone, temperature profile and pasteurization units inside the bottled beer during the pasteurization process. The results of the simulation were compared with the existing data in the literature. The results showed that, the location and size of the slowest heating zone is dependent on the time-temperature combination of each zone. The results also showed that the temperature profile of the bottled beer was found to be affected by the natural convection resulting from variation in density during pasteurization process and that the pasteurization unit increases with time subject to the temperature reached by the beer. Although the results of this work agreed with literatures in the aspects of slowest heating zone and temperature profiles, the results of pasteurization unit however did not agree. It was suspected that this must have been greatly affected by the bottle geometry, specific heat capacity and density of the beer in question. The work concludes that for effective pasteurization to be achieved, there is a need to optimize the spray water temperature and the time spent by the bottled product in each of the pasteurization zones.

Keywords: modeling, heat transfer, temperature profile, pasteurization process, bottled beer

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Authors: Satyanarayana Kosaraju, Venu Gopal Anne, Sateesh Nagari

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In this paper, the effect of cutting speed, feedrate and rake angle in tool geometry on cutting forces and temperature generated on the tool tip in turning were investigated. The data used for the investigation derived from experiments conducted on precision lathe according to the full factorial design to observe the effect of each factor level on the process performance. During the tests, depth of cut were kept constant and each test was conducted with a sharp coated tool insert. Ti-6Al-4V was used as the workpiece material. The effects of cutting parameters and tool geometry on cutting forces and tool tip temperature were analyzed. The main cutting force was observed to have a decreasing trend and temperature found to be increasing trend as the rake angle increased.

Keywords: cutting force, tool tip temperature, rake angle, machining

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Authors: Basma Hamdi, Lakdar Kairouani, Ezzedine Nahdi

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The objective of this work is to present a thermodynamic analysis of low temperature solar Rankine cycle with ejector for power generation using zeotropic mixtures. Based on theoretical calculation, effects of zeotropic mixtures compositions on the performance of solar Rankine cycle with ejector are discussed and compared with corresponding pure fluids. Variations of net power output, thermal efficiency were calculating with changing evaporation temperature. The ejector coefficient had analyzed as independent variable. The result show that (R245fa/R152a) has a higher thermal efficiency than using pure fluids.

Keywords: zeotropic mixture, thermodynamic analysis, ejector, low-temperature solar rankine cycle

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Authors: Wen-Jay Lee, Kuo-Ning Chiang

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The graphene binding with silicon substrate has apparently Schottky barriers property, which can be used in the application of solar cell and light source. Because graphene has only one atom layer, the atomistic structure of graphene binding with the silicon surface plays an important role to affect the properties of graphene. In this work, temperature effect on the morphology of graphene sheet attached on different crystal planes of silicon substrates are investigated by Molecular dynamics (MD) (LAMMPS, developed by Sandia National Laboratories). The results show that the covered graphene sheet would cause the structural deformation of the surface Si atoms of stubtrate. To achieve a stable state in the binding process, the surface Si atoms would adjust their position and fit the honeycomb structure of graphene after the graphene attaches to the Si surface. The height contour of graphene on different plane of silicon surfaces presents different pattern, leading the local residual stress at the interface. Due to the high density of dangling bond on the Si (111)7x7 surface, the surface of Si(111)7x7 is not matching with the graphene so well in contrast with Si(100)2x1and Si(111)2x1. Si(111)7x7 is found that only partial silicon adatoms are rearranged on surface after the attachment when the temperature is lower than 200K, As the temperature gradually increases, the deformation of surface structure becomes significant, as well as the residue stress. With increasing temperature till the 815K, the graphene sheet begins to destroy and mixes with the silicon atoms. For the Si(100)2x1 and Si(111)2x1, the silicon surface structure keep its structural arrangement with a higher temperature. With increasing temperature, the residual stress gradually decrease till a critical temperatures. When the temperature is higher than the critical temperature, the residual stress gradually increases and the structural deformation is found on the surface of the Si substrates.

Keywords: molecular dynamics, graphene, silicon, Schottky barriers, interface

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Authors: J. Julius Adebayo

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The objective of this paper is to assess the agro-climatic condition of Ibadan in the rain forest ecological zone of Nigeria, using rainfall pattern and temperature between 1978-2018. Data on rainfall and temperature in Ibadan, Oyo State for a period of 40 years were obtained from Meteorological Section of Forestry Research Institute of Nigeria, Ibadan and Oyo State Meteorology Centre. Time series analysis was employed to analyze the data. The trend revealed that rainfall is decreasing slowly and temperature is averagely increasing year after year. The model for rainfall and temperature are Yₜ = 1454.11-8*t and Yₜ = 31.5995 + 2.54 E-02*t respectively, where t is the time. On this basis, a forecast of 20 years (2019-2038) was generated, and the results showed a further downward trend on rainfall and upward trend in temperature, this indicates persistence rainfall shortage and very hot weather for agricultural practices in the southwest rain forest ecological zone. Suggestions on possible solutions to avert climate change crisis and also promote climate-smart agriculture for sustainable food and nutrition security were also discussed.

Keywords: climate change, rainfall pattern, temperature, time series analysis, food and nutrition security

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Authors: Jung-Ho Moon, Tae Kwon Ha

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Continually increasing working temperature and growing need for greater efficiency and reliability of automotive exhaust require systematic investigation into the thermal fatigue properties especially of high temperature stainless steels. In this study, thermal fatigue properties of 300 series austenitic stainless steels have been evaluated in the temperature ranges of 200-800°C and 200-900°C. Systematic methods for control of temperatures within the predetermined range and measurement of load applied to specimens as a function of temperature during thermal cycles have been established. Thermal fatigue tests were conducted under fully constrained condition, where both ends of specimens were completely fixed. Load relaxation behavior at the temperatures of thermal cycle was closely related with the thermal fatigue property.

Keywords: austenitic stainless steel, automotive exhaust, thermal fatigue, microstructure, load relaxation

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Authors: Iliya Bitrus Abaje

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This study examines the evidence of climate change scenario in Kaduna State from the analysis of temperature and rainfall data (1976-2015) from three meteorological stations along a geographic transect from the southern part to the northern part of the State. Different statistical methods were used in determining the changes in both the temperature and rainfall series. The result of the linear trend lines revealed a mean increase in average temperature of 0.73oC for the 40 years period of study in the State. The plotted standard deviation for the temperature anomalies generally revealed that years of temperatures above the mean standard deviation (hotter than the normal conditions) in the last two decades (1996-2005 and 2006-2015) were more than those below (colder than the normal condition). The Cramer’s test and student’s t-test generally revealed an increasing temperature trend in the recent decades. The increased in temperature is an evidence that the earth’s atmosphere is getting warmer in recent years. The linear trend line equation of the annual rainfall for the period of study showed a mean increase of 316.25 mm for the State. Findings also revealed that the plotted standard deviation for the rainfall anomalies, and the 10-year non-overlapping and 30-year overlapping sub-periods analysis in all the three stations generally showed an increasing trend from the beginning of the data to the recent years. This is an evidence that the study area is now experiencing wetter conditions in recent years and hence climate change. The study recommends diversification of the economic base of the populace with emphasis on moving away from activities that are sensitive to temperature and rainfall extremes Also, appropriate strategies to ameliorate the scourge of climate change at all levels/sectors should always take into account the recent changes in temperature and rainfall amount in the area.

Keywords: anomalies, linear trend, rainfall, temperature

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Authors: Andi Syahputra, R. H. Jatmiko, D. R. Hizbaron

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Land surface temperature (LST) in an area is influenced by conditions of vegetation density, building density, and the number of inhabitants who live in the area. Medan City is one of the largest cities in Indonesia, with a high rate of change from vegetation to developed land. This study aims to identify the relationship between the percentage of building density and land surface temperature in Medan City. Pixel image analysis method is carried out to obtain the value of building density in pixel images of Landsat 8 images with the help of WorldView-2 satellite imagery. The results showed the highest land surface temperature in 2018 of 35, 4°C was found in Medan Perjuangan District, and the lowest was 22.5°C in Medan Belawan District. Building density samples with a density level of 889.17 m were also found in Medan Perjuangan District, while the lowest building density sample was found in Medan Timur District. Linear regression analysis of the effect of building density with land surface temperature obtained a correlation (R) was 0.64, and a coefficient of determination (R²) was 0.411 and modeling of building density based on the LST has a correlation (R), and a coefficient of determination (R²) was 0.72 with The RMSE obtained 0.853.

Keywords: land surface temperature, Landsat, imagery, building density, vegetation, density

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Authors: Wendong Yang, Changhai Wang, Valeria Arrighi

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Low ink sintering temperature is desired for flexible electronics, as it would widen the application of the ink on temperature-sensitive substrates where the selection of silver precursor is very critical. In this paper, four types of organic silver precursors, silver carbonate, silver oxalate, silver tartrate and silver itaconate, were synthesized using an ion exchange method, firstly. Various characterization methods were employed to investigate their physical phase, chemical composition, morphologies and thermal decomposition behavior. It was found that silver oxalate had the ideal thermal property and showed the lowest decomposition temperature. An ink was then formulated by complexing the as-prepared silver oxalate with ethylenediamine in organic solvents. Results show that a favorable conductive film with a uniform surface structure consisting of silver nanoparticles and few voids could be produced from the ink at a sintering temperature of 150 °C.

Keywords: conductive ink, electrical property, film, organic silver

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Authors: Ahmed M. Seyam, Rita Nemes

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In this study, the influence of elevated temperature and concrete age on the compressive strength of concrete produced by normal quartz aggregate, expanded clay, expanded glass, crushed andesite and crushed clay bricks aggregates were investigated. For this purpose, six different mixtures were prepared by 100% replacement of the coarse aggregate. The specimens were cured in water for seven days, then kept in the laboratory for 120 days and 240 days. The concrete specimens were heated in an electric furnace up to 200, 400, 600, 800, and 1000 °C and kept at these temperatures for two hours heating, then for 24 hours cooling. The residual compressive strength of the specimens was measured. The results showed that, the elevated temperature induces a significant decrease in a compressive strength in both normal weight and lightweight aggregate concrete, by comparing the behavior of different mixes, in all cases, the strength of the specimens containing crushed andesite aggregates showed a better performance for compressive strength after exposure to elevated temperatures over 800 °C, while the specimens containing expanded glass showing the least residual strength after subjected to elevated temperature; moreover the age of the concrete in all mixes has also been an effective factor, the behavior of the concrete strength loss by increasing heating temperature was not changed but the strength results showing the better performance and higher compressive strength in both ambient and elevated temperature.

Keywords: elevated temperature, concrete age, compressive strength, expanded clay, expanded glass, crushed andesite, crushed clay bricks

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Authors: Ruxandra Aursulesei, David O’Callaghan, Cian Ryan, Diarmaid O’Cualain, Viktor Varkarakis, Alina Sultana, Joseph Lemley

Abstract:

Human errors caused by drowsiness are among the leading causes of road accidents. Neurobiological research gives information about the electrical signals emitted by neurons firing within the brain. Electrical signal frequencies can be determined by attaching bio-sensors to the head surface. By observing the electrical impulses and the rhythmic interaction of neurons with each other, we can predict the mental state of a person. In this paper, we aim to better understand intersubject and intrasubject variability in terms of electrophysiological patterns that occur at the onset of drowsiness and their evolution with the decreasing of vigilance. The purpose is to lay the foundations for an algorithm that detects the onset of drowsiness before the physical signs become apparent.

Keywords: electroencephalography, drowsiness, ADAS, annotations, clinician

Procedia PDF Downloads 76

Authors: R. Morbidelli, C. Saltalippi, A. Flammini, A. Garcia-Marin, J. L. Ayuso-Munoz

Abstract:

The climate change, mainly due to greenhouse gas emissions associated to human activities, has been modifying hydrologic processes with a direct effect on air surface temperature that has significantly increased in the last century at global scale. In this context the Mediterranean area is considered to be particularly sensitive to the climate change impacts on temperature indices. An analysis finalized to study the evolution of temperature indices and to check the existence of significant trends in the Umbria Region (Italy) is presented. Temperature data were obtained by seven meteorological stations uniformly distributed in the study area and characterized by very long series of temperature observations (at least 60 years) spanning the 1924-2015 period. A set of 39 temperature indices represented by monthly and annual mean, average maximum and average minimum temperatures, has been derived. The trend analysis was realized by applying the non-parametric Mann-Kendall test, while the non-parametric Pettit test and the parametric Standard Normal Homogeneity test (SNHT) were used to check the presence of breakpoints or in-homogeneities due to environmental changes/anthropic activity or climate change effects. The Umbria region, in agreement with other recent studies exploring the temperature behavior in Italy, shows a general increase in all temperature indices, with the only exception of Gubbio site that exhibits very light negative trends or absence of trend. The presence of break points and in-homogeneity was widely explored through the selected tests and the results were checked on the basis of the well-known metadata of the meteorological stations.

Keywords: reception theory, reading, literary translation, horizons of expectation, reader

Procedia PDF Downloads 125

Authors: Ifeyinwa Orakwe, Ngozi Nwogu, Edward Gobina

Abstract:

This work presents experimental results relating to the structural characterization of a commercially available alumina membrane. A γ-alumina mesoporous tubular membrane has been used. Nitrogen adsorption-desorption, scanning electron microscopy and gas permeability test has been carried out on the alumina membrane to characterize its structural features. Scanning electron microscopy (SEM) was used to determine the pore size distribution of the membrane. Pore size, specific surface area and pore size distribution were also determined with the use of the Nitrogen adsorption-desorption instrument. Gas permeation tests were carried out on the membrane using a variety of single and mixed gases. The permeabilities at different pressure between 0.05-1 bar and temperature range of 25-200oC were used for the single and mixed gases: nitrogen (N2), helium (He), oxygen (O2), carbon dioxide (CO2), 14%CO₂/N₂, 60%CO₂/N₂, 30%CO₂/CH4 and 21%O₂/N₂. Plots of flow rate verses pressure were obtained. Results got showed the effect of temperature on the permeation rate of the various gases. At 0.5 bar for example, the flow rate for N2 was relatively constant before decreasing with an increase in temperature, while for O2, it continuously decreased with an increase in temperature. In the case of 30%CO₂/CH4 and 14%CO₂/N₂, the flow rate showed an increase then a decrease with increase in temperature. The effect of temperature on the membrane performance of the various gases is presented and the influence of the trans membrane pressure drop will be discussed in this paper.

Keywords: alumina membrane, Nitrogen adsorption-desorption, scanning electron microscopy, gas permeation, temperature

Procedia PDF Downloads 287

Authors: Renu Gupta, Ashim K. Pramanik

Abstract:

We report the evolution of structure and magnetic properties in perovskite ruthenates Sr1-xPrxRuO3 (x = 0.0 and 0.1). Our main expectations, to induce the structural modification and change the Ru charge state by Pr doping at Sr site. By the Pr doping on Sr site retains orthorhombic structure while we find a minor change in structural parameters. The SrRuO3 have itinerant type of ferromagnetism with ordering temperature ~160 K. By Pr doping, the magnetic moment decrease and ZFC show three distinct peaks (three transition temperature; TM1, TM2 and TM3). Further analysis of magnetization of both samples, at high temperature follow modified CWL and Pr doping gives Curie temperature ~ 129 K which is close to TM2. Above TM2 to TM3, the inverse susceptibility shows upward deviation from CW behavior, indicating the existence AFM like clustered in this regime. The low-temperature isothermal magnetization M (H) shows moment decreases by Pr doping. The Arrott plot gives spontaneous magnetization (Ms) which also decreases by Pr doping. The evolution of Rhodes-Wohlfarth ratio increases which suggests the FM in this system evolves toward the itinerant type by Pr doping.

Keywords: itinerant ferromagnet, Perovskite structure, Ruthenates, Rhodes-Wohlfarth ratio

Procedia PDF Downloads 323