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Changes in pore fluid can significantly impact the geotechnical behavior of soil, especially clayey soil. One source of soil contamination is leachate, which can infiltrate nearby soil during the collection, transportation, and deposition stages of the residential waste disposal process, exerting geotechnical influences on the soil in the surrounding area. To assess these effects, four leachate samples were collected from different sites. The specimen comprises fine soil, created from a mixture of sand, bentonite, and kaolinite. Experimental results reveal a decreasing trend in the liquid limit, compaction parameters, and cohesion values of the soil with an increase in contamination level. However, the internal friction angle exhibits an increasing trend with higher leachate concentration, resembling the behavior of sandy soil, as opposed to the typical behavior of clay.

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    Electrical conductivity (EC) is the ability to conduct electricity which is expressed as micro Siemens per centimeter (µs/cm). The conductance of the milk is attributed mainly to its salts content especially Na, K and Cl ions. Since measuring the milk’s EC is a rapid and inexpensive method for determining of the milk quality, therefore correlation between EC with pH, acidity, and total microbial count (TC) in raw milk was studied in order to assess the freshness of milk in this research. In a pilot study, using skim milk, pH, acidity, and TC were changed and EC measured at 25ºc. Then a total of 200 samples of whole milk were obtained from the receiving platform of a dairy plant in Tehran. In one trial 100 samples of whole milk were examined for pH, acidity and TC. Also EC was measured in different temperatures of milk samples at the time of the analysis. In the second 100 samples of whole milk, pH, acidity and TC determined and EC measured at 25ºC. According to the results obtained from the pilot study (with 10 repetition), increasing the pH caused a decrease in EC and vice versa (P0/05). No significant correlation was found between EC with pH, acidity and TC in other trials (P>0.05). It seems many factors may affect the EC in raw whole milk. Therefore measuring EC solely can not determine the milk quality.

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Research subject: Polymer nanofibers have attracted much industrial interest over the past decade. In general, these fibers are suitable for a variety of applications including medical applications, insulation, capacitors, advanced aerospace technologies, and so on. Specifically in aerospace technology, the used materials must be thermally stable with suitable electrical conductivity. However, many of these polymer nanofibers suffer from low temperature degradation and low electrical conductivity, limiting their use in many potential applications. Graphite has unique properties such as high conductivity and high thermal stability. This exceptional material can be included as a nanoparticle in polymer nanofibers to modify electrical and thermal properties.The aim of this research was to investigate the effect of addition of graphite nanoparticle on thermal and electrical propertiesof polymer fibers.
Research approach:  For this purpose, polyvinyl alcohol 72000 (PVA) as a non-conductive polymer and graphite nanoparticles were used. Polyvinyl alcohol-graphite nanofibers were synthesized method by electrospinning technique under optimized parameters. The optimum conditions for the electrospinning process were: PVA concentration of 8%, applied voltage of 22 Kv, flow rate of 10 ml and tip/collector distance of 20 cm.
Main results:  Scanning electron microscopy (SEM) studies showed that produced PVA fibers were smooth, continuous without any bead, with a diameter of about 350 nm. The PVA / graphite nanofibers were also smooth but much thinner (about 200 nm) than PVA fibers at the same processing parameters. Moreover, X-ray patterns of PVA/graphite nanofibers include peaks of graphite particles in the structure and slso the suppression of crystallinity.  According to the results of 4 point probe teste, by increasing weight percentage of graphite in the fibers, electrical conductivity increased up to 0.5 . The thermal behavior of PVA nanofibers after mixing with graphite was also investigated by differential calorimetry analysis (DSC) and TGA. It was demonstrated that PVA / graphite nanofibers are thermally stable up to 300 ° C.

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Background: Soil salinization is a world-wide land degradation process in arid and semi-arid regions that leads to sever economic and social consequences.
Materials and Methods: We analyzed soil salinity by two statistical linear (multiple linear regression) and non-linear (artificial neural network) models using Landsat OLI data in Agh-Ghala plain located in north east of Iran. In situ soil electrical conductivity (EC) of 156 topsoil samples (depth of 0-15cm) was also determined. A Pearson correlation between 26 spectral indices derived from Landsat OLI data and in situ measured ECs was used to apply efficient indices in assessing soil salinity. The best correlated indices such as blue, green and red bands, intensity indices (Int1, Int2), soil salinity indices (Si1, Si2, Si3, Si11, Aster-Si), vegetation Indices (NDVI, DVI, RVI, SAVI), greenness and wetness indices were used to develop two models.
Results: Comparison between two estimation models showed that the performance of ANN model (R²=0.964 and RMSE=2.237) was more reliable than that of MLR model (R²=0.506 and RMSE=9.674) in monitoring and predicting soil salinity. Out of the total area, 66% and 55.8% was identified as non-saline, slightly and very slightly saline for ANN and MLR models, respectively.
Conclusions: This shows that remote sensing data can be effectively used to model and map spatial variations of soil salinity. 

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Salinity is the primary water quality concern in irrigated agriculture. An Electrical Conductivity (EC) meter and a hydrometer are two possible methods for measurement of irrigation water salinity. The conductivity meter method is based on measuring the amount of electrical current that a fluid will support. Although it is the most widely used method, the instrumentation is rather expensive and in some instances may require sample dilution. The hydrometer method is based on measuring the density of the fluid. The main objectives of this study were to compare these two methods and, based on hydrometer method, develop empirical models for prediction of EC, sodium adsorption ratio (SAR), and the principle ion concentrations in the irrigation waters of Yazd Province, Iran. The electrical conductivity, temperature, and density of 206 water samples from wells across Yazd Province were measured. Temperature correction factors for adjusting the hydrometer reading to 25 oC were determined. The correlation between EC and hydrometer readings was high (R2 = 0.97). Although the empirical model developed for prediction of EC slightly underpredicted the measured values, it is still accurate enough for practical purposes. Hydrometer readings were also highly correlated with the principle ions and SAR. The salt type also affected the hydrometer readings. Magnesium sulfate solution had the highest density among the major salt types present in irrigation waters. Finally, a chart was developed for rough estimations of EC, sodium and chlorine concentrations in irrigation waters of Yazd Province, Iran.

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  The present work was undertaken with an objective to study the design, development and construction and performance evaluation of a batch ohmic heating system. Direct ohmic heating (Joule’s heating) is a technology to warm up the food using an electric energy where electric current is passed through a material which gets heated by virtue of its electrical resistance. In this study, firstly new batch ohmic heating containing a static cell (200-mm-long Teflon cylinder with 94 mm diameter at a constant voltage gradient of 15 V/cm) was developed and constructed. To evaluate the performance of this heating unit various food systems was used, i.e. sodium chloride solutions (concentrations : 0.2 and 0.6% w/v), starch solutions (2 and 5% w/v) and 0.5% w/v NaCl,  a two-phase food systems (5% starch, 0.5% w/v NaCl and oil (1% and 10% w/v). Heating rates for previously named food systems were determined by tracking and recording the temperature profiles for a given time intervals. The data indicates the heating up rate increases with increasing concentrations of starch and salt but decreases with increasing oil in food.

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Determination of thermo-physical properties of pomegranate juice is necessary to control processes such as drying and concentration. These properties have been affected by soluble solid content and temperature. Therefore the properties including; density, specific heat and thermal conductivity were determined at three levels of soluble solid content, 12^o, 40^o and 65^o Brix and temperature range from 25 to 70 ^oC. Thermal conductivity by co-axial cylinder apparatus, specific heat by differential scanning calorimeter and density by a volumetric pycnometer were measured. Regression analysis indicated that both soluble solid content and temperature affected on these properties but the soluble solid content has more influence. Increase of soluble solid content from 12 to 65 caused a decrease in thermal conductivity from 0.233 to 0.193 W/m.^oC, specific heat from 5.19 to 3.34 kJ/kg.^oC and an increase in density from 1027 to 1323 kg/m³ respectively. With increase in temperature from 30 to 70 ^oC, density decrease from 1173 to 1150 kg/m³ but thermal conductivity increase from 0.188 to 0.229 W/m.^oC during temperature increasing from 28 to 42 ^oC and specific heat increase from 3.9 to 4.4 kJ/kg during temperature increasing from 40 to 60 ^oC. With regression analysis, the suitable empirical models of thermophysical properties of pomegranate juice with operating variables were obtained.

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Application of feed pellets in animal and aquatic farming industries has grown because of both the physical and the nutritional benefits it provides. Development of feed pellets manufacturing industry is also considerable. Steam conditioning process, which plays an important role in pelleting production, includes heating feed particles, adding moisture, and mixing the mash. Pellets cooling and drying processes are also involved in heat transfer phenomena. In this study, thermal conductivity of feed pellets was determined at different temperatures ranging from 25 to 85°C and moisture contents of 11.8 to 18.2% wb. It was measured by the transient technique using the line heat source method assembled in a thermal conductivity probe. It turned out that decreasing moisture contents from 18.2 to 11.8% (wb) produced non-linear reduction in thermal conductivity. The average values of thermal conductivity changed from 0.1509 to 0.2143 W m^-1 °C^-1 at different moisture contents. Tests conducted on two pellet size categories (based on nominal diameter) revealed a significant difference in thermal conductivity between these categories. The thermal conductivities of the first category (minor than nominal dia.) appeared to be 8.5% higher than those of the second category (superior to nominal dia.). Average values of thermal conductivity changed from 0.1538 to 0.2333 W m^-1 °C^-1 for the first category and from 0.1235 to 0.2456 W m^-1 °C^-1 for the second category (in 25°C). In addition, some empirical models were developed to express thermal properties as a function of moisture content and temperature.

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During the past few decades, growing global concern about environmental problems, caused by widespread use of fossil fuels, attracts more research attention toward adsorption systems technology. However, one of the main problems of these systems is the poor heat transfer rate in adsorbent bed due to its low thermal conductivity. In the present study, extended surfaces and metal piece additives are applied to the adsorbent bed in order to numerically investigate the effect of heat transfer enhancement on the adsorption system performance. Employing metal pieces increases effective thermal conductivity of the bed by at least 100%. Results indicate that decreasing fin space and fin height and adding metal pieces to the adsorbent bed reduce the cycle time which finally improves the system specific cooling power. However, it is worth mentioning that the effect of metal piece additives on the cycle time reduction and specific cooling power improvement decreases at smaller fin spaces. Moreover, results show that the increase of fin height improves the coefficient of performance while decreases the specific cooling power of the system. On the contrary, the reduction of fin space simultaneously increases the coefficient of performance and the specific cooling power of the adsorption system.

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This work presents a model for calculating the effective thermal conductivity of nanofluids. In this method, the effect of non-uniform sizes of nanoparticles and interfacial layer is investigated simultaneously. The developed model for the thermal conductivity of nanofluids takes into account the effects of the thermal conductivity of base fluids, the thermal conductivity, the volume fraction and the size of nanoparticles, the interfacial layer, non-uniform sizes of nanoparticles, Brownian motion and temperature. Hence, this model has the capability of offering both analytical and numerical Predictions. The accuracy of proposed model for the effective thermal conductivity of water-〖 Al〗_2 O_3, ethylene glycol-〖 Al〗_2 O_3, water- CuO, ethylene glycol-CuO, ethylene glycol-Al, water- TiO_2 is investigated. The effect of temperature, size of nanopartcles and volume fraction of nanopartcles is determined. Results show that the interfacial layer at the nanoparticle-liquid interface and non-uniform sizes of nonparticles are the important parameters for calculating the thermal conductivity of nanofluids. The Comparison between the result and available experimental data of several types of nanofluids indicates that the proposed model provides accurate results and the maximum error is 5%.

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This Study presents a numerical investigation of the hydro-thermal behavior of a Non-Newtonian ferrofluid (non-Newtonian base fluid and 4% Vol. Fe3O4) in a rectangular vertical duct in the presence of different magnetic fields, using two-phase mixture model, power-law model, and control volume technique. Considering the electrical conductivity of the base fluid, in addition to the ferrohydrodynamics principles, the magnetohydrodynamics principles have also been taken into account. To study the effects of non-Newtonian base fluid using power-law model, assuming the same flow consistency index with viscosity of Newtonian fluid, two different power law indexes (i.e., n=0.8 and 0.6), have been investigated and the results have been compared with that of Newtonian ones (i.e., n=1). Three cases for magnetic field have been considered to study mixed convection of the ferrofluid: non-uniform axial field, uniform transverse field and another case when both fields are applied simultaneously. The results indicate that the overall influence of magnetic fields on Nusselt number and friction factor is similar to the Newtonian case, although, by decreasing the power law index, the effect of axial field on velocity profile, Nusselt number and friction factor become more significant. Moreover, the results indicate that electrical conductivity has a significant effect on the behavior of ferrofluid and cannot be neglected and also negative gradient axial field and uniform transverse field act similarly and enhance both the Nusselt number and the friction factor, while positive gradient axial field decreases them.

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Awareness of the thermal conductivity of nanofluids regard to a significant development for use in research,it is necessary with regard to the inability of the analytical and experimental models that presented in most cases, it experimentally thermal conductivity can be measured. In this paper, the design and performance of thermal conductivity of fluids and nanofluidics measurement device without using a Wheatstone bridge is tested. Wheatstone bridge short transient hot wire method has previously been used for construction that requiring complex electronic systems and high power consumption. In this paper, a new method is provided so that no current or voltage is kept constant, but the method of measuring the relative resistance of the copper-clad lacquered with a diameter of 40 microns was used probe is easy to is within reach. The difference between the results of the design references, 1.17% is obtained. In this regard, changes in the magnetic fluid thermal conductivity is studied experimentally. Magnetic fluids are a new class of nanofluids are affected by magnetic fields and their properties can be changed. Fe3O4 magnetic water-based tests for different volume percentages.

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The soaking stage is the most important steps of the parboiling process. Hot soaking requires precise control, because starch granules are gelatinized during soaking. Degree of starch gelatinization (DSG) of rice was measured using differential scanning calorimetry (DSC). This method has high costs and can not be utilized to obtain online data. Thus, in this study a mathematical relationship correlating the DSG of rice to the paddy physical (paddy moisture) -electrical (electrical conductivity (EC) and capacitance sensor output voltage of paddy water) during the soaking portion of the parboiling process was formulated. For measuring of electrical properties of paddy water was designed and manufactured an experimental system of ohmic heater and capacitance sensor for measuring electrical conductivity and voltage, respectively. For doing experiment, paddy (Shiroudi variety) was parboiled by soaking at 60, 65 and 70 oC. At each temperature, samples of paddy and paddy water were selected at five different soaking times. The experimnet results showed that paddy moisture content (21.18-35.1%w.b.), electrical conductivity (0.63-1.6 mS.cm-1) and output voltage of capacitance sensor (216 – 595 mV) of paddy water and rice DSG (5.5 to 31.7%) increased significantly (p<0.05) and exponentially (R2>0.98), exponentially (R2>0.93), quadraticly (R2>0.95) and exponentially (R2>0.96) during soaking, respectively. Linear relationships were fitted between DSG of parboiled rice and physical-electrical properties of paddy water. The results revealed that EC of paddy water be able to predict the DSG of rice during soaking with the lowest regression error.

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In this paper, efficiency of defected graphene nano ribbon incorporating with additional nanoparticles on mass detection operations is studied via the Reverse Non Equilibrium Molecular Dynamics (RNEMD) method. Thermal conductivity management of this structure is challenging because of imposed losses in electrical conductivity and any procedure could manage the thermal conductivity of graphene will be useful. In this paper it is observed that on the mass detection operation, due to the porosity generation in the nano ribbon surface or even creation of external nanoparticles, thermal properties of graphene change considerably. This should be noted in calibration of graphene based mass sensors. In summary, results show that the graphene’s thermal conductivity would reduce by increasing the concentration of nanoparticles and thermal conductivity of graphene is higher when porosities and impurities are at the edges. This indicates that the location of vacancies and nanoparticles influences the thermal conductivity. For a better thermal management with the help of nanoparticles, wither respect to the porosities, addition of nanoparticles decrease the thermal conductivity more and more. By increasing the cavity’s diameter from 0.5nm to 4.4nm in a specific single layer graphene, thermal conductivity was reduced from 67 W/mk to 1.43 W/mk.

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The existence of soft clay and dispersive soft clay at the site of engineering structures is regarded as one of the geotechnical problems. This study is performed on silty soft clay that according to the experimental results showed 100% dispersivity potential. Due to the low bearing capacity of this type of soil in the site, the slaked lime was used to stabilize the soil geotechnical properties, to increase its strength, to decrease plasticity behaviour of soil, and to overcome its dispersive properties. The main goal of the present study is to determine the growth rate and progress of lime-soil pozzolanic reactions in short and long terms from micro- and macro- structural point of view, as well as the measurement of the consumed lime rate over the time and its effect on mechanical parameters of the stabilized soil. The results of this study allow determining the minimum percentage of the lime that is necessary to react with clay minerals for making an acceptable change in long-term properties of stabilized soil. In this regard, a number of tests carried out with different percentages (0 to 10 percent) of hydrated lime. The pH, electric conductivity (EC), unconfined compressive strength, and lime consumption rate determination by X-ray diffraction analysis were the tests used in this study to observe the progress of lime reaction with clay. In order to determine the microstructural and mineralogical changes, and reaction products formed in the modified soil, X-ray diffraction (XRD) evaluation and scanning electron microscopy images have been used. Among the most important results of the present study, this paper propose a simple criterion for the onset of pozzolanic reactions and determination of the consumed lime rate during the pozzolanic reaction process based on pH and electric conductivity measurements. Based on the results from pH, EC, XRD, and unconfined compressive strength (UCS) tests, the pozzolanic reaction occurs at EC ≥ 4 mS/cm. Following that, the formation of new components such as calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH) causes an increase in soil strength. Over the time, with the reduction of EC ≤ 4 mS/cm and pH ≤ 12.4, the progress rate of pozzolanic reaction and the progress rate in soil strength suspend. The results show that for the dispersive soil around 3-4% lime is sufficient for its short-term reaction, which includes cation exchange. Based on the achieved results, the use of 6% lime for stabilization of sample gives EC ≥ 4.0 mS/cm and pH ≥ 12 after the first 14 days period. The unconfined compressive strength of the stabilized sample increased around 10 times in the same period, while only 5% increase in strength observed after 14 days (EC ≤ 4.0 mS/cm and pH ≤ 12).

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In this study, a Lattice Boltzmann Method (LBM) has been developed to calculate the distribution of a scalar quantity, like temperature, in a natural convection flow field under the condition of varying fluid thermal conductivity. The standard form of an LBM usually considers the fluid properties to be constant without any source term in conservation equations. The model developed is to account for variation of thermal conductivity with temperature in the presence of an external heat source. The proposed model has been examined against various case studies. It is shown that it is capable of modeling the extremely nonlinear problems. To magnify the nonlinear term in the natural convection case of under study, the radiation and other thermal sources have been used. The multiple relaxation time scheme has been applied to assure the solution stability. Using Chapman-Enskog analysis, the error associated with the proposed model has been estimated. The part of error which was not due to variations in the fluid properties, may be eliminated by introducing a correction term in higher order terms in Chapman-Enskog analysis. In addition, it has been shown that the correction term associated with the fluid conductivity variations, create an error of second order in terms of Knudsen number and is negligible. The present LBM model has an error of the second order of magnitude with respect to time.

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This Paper, with the help of the device was made in this university as "rapid prototyping device base on direct metal laser melting", study interaction of metal powder apparent density and heat transfer experimentally. Selective Laser Melting (SLM) is a direct fabrication of part through layer by layer powder deposition and successive laser beam irradiation. One of the important properties of the SLM is thermal conductivity and thermal diffusivity of the metal powder. In this paper, thermal conductivity and diffusivity of metal powder with various apparent densities were studied. According to the method of measuring (the difference between two temperatures), The tests showed the dependence of thermal properties to metal powder apparent density. Changes in apparent density was established through the pressure applied to the raw powder bed. Because achieve to desirable apparent density through proper distribution is much expensive. This study was done in range of apparent density 44.75% to 56.4% compared to the density of pure iron. Comparing the samples produced in different densities it was understood that the pressure applied to the raw powder bed with the optimum point of arrest. In fact, the best quality of the manufactured parts, in density of about 46% was obtained.