سجاد کیانی

Connecting the tractor engine to its front axle and maintaining the Wheel-Base (WB) distance of the tractor in its standard range is done using a part called the front bracket. It's part of the tractor's main chassis. This study was carried out to manufacture a new bracket due to the increase in engine power of a tractor from 37 to 52 kW. The WB distance of a tractor directly depends on its engine power. The bracket was designed in three-dimensional form by Catia software and analyzed in terms of mechanical strength by finite element method under static and dynamic loads in Abaqus software. Due to the need for high strength in this part, ductile cast iron (GGG40, yield strength: 250 MPa) was considered as its raw material. Static and dynamic analysis results showed that the maximum stress applied to the part (93.7 MPa) is lower than the yield strength of the designed part. Once the part's strength was verified, a casting mold was designed using Catia software and manufactured by aluminium casting and machining. Five initial samples were then cast and machined before being installed on sample tractors (RK704 model, maximum weight: 2635 kg) for field tests. The results of the tests indicated that the manufactured part maintained the WB distance, installation conditions, and mechanical strength and was reliable for use in producing this tractor.

The common methods that are usually used to identify the devoid rough rice from the healthy ones are often time-consuming and expensive. For this reason, in this research, a smart and fast method based on machine vision system coupled with artificial neural networks is presented in order to predict the percentage of devoid/healthy rough rice grains. Digital images of five varieties of paddy were prepared in three states: healthy, devoid, and mixed, in two states scattered and piled. After pre-processing and segmentation, 3 color features and 5 morphological features were extracted for each rice grain. Principal component analysis (PCA) method was then used in order to identify the most effective features in distinguishing devoid rough from healthy rice. In the next step, multilayer perceptron (MLP) algorithm based on the main components obtained by PCA method was used to create models for identifying and classifying the samples. Root Mean Square Error (RMSE), correlation coefficient (R2), specificity and sensitivity were used to evaluate the modeling capability and validation of each algorithm. The obtained results showed that the designed intelligent method can identify devoid rough rice seeds with acceptable accuracy in all cultivars (R2P>0.81, RMSEp<0.219, Sensitivity>0.8 & Specificity>0.98). Therefore, the machine vision system in combination with artificial neural networks can be used as an intelligent and fast method at the entrance of rice bleaching factories to evaluate the quality of harvested rough rice and predict the percentage of unhealthy rough rice.

In this research, the design, static analysis, and manufacturing of a platform for tractors with a power range of 40 to 60 hp and max weight of 2450 kg was performed. This platform includes the main chassis, steering column chassis, right and left fenders, rollover protection structure (ROPS), and other connecting parts. The main chassis was designed to include all the levers and control pedals, the driver's seat, the dashboard, and the steering system. The ROPS is mounted on the main chassis and is used to protect the driver in the event of a tractor overturning. The platform was designed with ST37 alloy steel for the chassis set and ST44 for ROPS using CATIA software, tested in accordance with ISO 5700 standard for static loading and mechanical strength. Maximum static stress obtained in ROPS compared to the final strength of ST44 steel (580 MPa, and with dimensions of 6×8 mm and thickness of 4 mm) for tractors RK404-A (Paddy/Garden model) and RK604-A (Garden/Farm model) was in the safe range and has sufficient strength. Also, ROPS in the maximum deflection during loadings did not enter the safe area of the driver. Technical knowledge of designed parts (2d and 3d drawings) was extracted and the parts were manufactured, assembled, and evaluated. The final results showed that the designed and manufactured platform with specific dimensions, material, and weight (209 kg) in terms of dimensions, mechanical strength, the place for installing pedals and control systems, and appearance is suitable to use in the production of tractors with a maximum weight of 2450 kg.

Khuzestan province has fertile plains for agriculture. In recent years, the regular supply of water in Izeh plain and Bagh Malek has been a concern, especially for agricultural purposes. With the help of a pumping station, the water of these areas reaches the heights overlooking the area from the reservoir of the Karun 3 dam and moves by gravity towards the delivery points after passing through a tunnel. The normal level of the dam during operation is 840 meters, the maximum level of the reservoir is 845 and the top level is 850 meters from the level of the Azad sea, also the minimum and maximum level of water intake from the lake of Karun Dam 3 is equal to 800 and 845 meters, respectively. Basic studies and numerical methods to achieve the goal of the current research, which is to optimize the level to which water is pumped, it was done. According to the optimizations, the lowest cost will be at the level of 970 if the tunnel level of 1000 is considered in the initial plan.

This study aimed to design, perform static and dynamic analysis, manufacture, and evaluate an oleaster mill machine. It was designed from a crusher, anti-crusher, tray, body, chassis, inlet, and outlet. After the 3D design, static and dynamic analyses were performed to confirm the strength of the crusher. Then, the technical knowledge (drawings) was extracted and used to manufacture the machine through sheet metal and welding (body and its accessories) as well as casting-machining methods (crusher and anti-crusher parts). An electric motor (2.206 kW) was utilized to rotate the crusher. The manufactured machine was evaluated by measuring the amount of pulverization of oleaster fruit (particles smaller than 250 microns) at various moisture content of the fruit (close to 0% or no change in the moisture content of the sample at 70 C, 5%, and 10%), different speeds of the crusher (750, 1000, 1250, 1500 rpm) and different sizes of tray meshes (0.5, 0.75 and 1 mm) in the form of a factorial experiment based on a completely randomized design in three replications. Statistical analysis showed that the maximum amount of pulverization (80.16) was achieved at the highest rotating speed of the crusher, with the size of tray meshes of 0.75 mm, and samples at moisture content close to zero. By a similar setup, the pulverization was calculated at 79.33% and 55.12% at 5% and 10% moisture content of the samples, respectively. For the manufactured machine and samples at 5% moisture content, which is recommended, the total capacity was calculated at 30 kg/h.

In this study, the discriminatory power of Metal Oxide Semiconductor (MOS) gas sensors was evaluated to develop a portable electronic nose (e-nose) system for clustering different types of saffron samples based on their Volatile Organic Components (VOCs). The system was comprised of ten MOS gas sensors, direct headspace sampling, microcontroller devices, and a laptop computer coupled with multivariate computational tools. Eleven saffron samples were procured from different geographical origins for the experiments. Principal Component Analysis (PCA) and Hiricultural Cluster Analysis (HCA) models were applied for sample clustering and for demonstrating the discriminatory power of the gas sensors as well. The quality assessment of the samples was also performed by the standard laboratory method (ISO3632). The gas sensors data were acquired at 350-360 seconds after the samples were exposed to the sensors. Results of the PCA and HCA analysis of the sensors data indicated that the saffron samples were divided into three main clusters. Also, it was found that the discrimination power of the sensors was different and the possibility of removing sensors with low discriminatory power (2 sensors) was provided. Results of laboratory analysis (destructive method) were obtained in accordance with the classification results of the e-nose data analysis. Using the proposed method to find the most effective MOS sensors and eliminating the redundant sensors can help to reduce the development costs of the electronic nose systems and the processor input data. It also increases the classification accuracy of the e-nose system in the quality control of medicinal plants.

The production of waste has caused environmental crises that pose serious threats to the life of creatures on Earth. This study aimed to evaluate the strategy and location of waste disposal site in Kiyan watershed with an emphasis on EIA through survey-analytical method. Based on the locating process, a suitable landfill site of 10 hectares was selected in the village of Karke-oliya. As basalt-andesite rocks have high permeability and are resistant to erosion, the proposed area has high environmental capacity for waste disposal. Data from the Meteorological Organization show the prevailing wind direction within the study area is northwest. The western wind dominates, and since the villages of the study area are northwest and west of the landfill area, the effects of the landfill's unpleasant odor will be far off. In addition, since the area is enclosed in terms of topography, which can be seen in the transverse and longitudinal profiles of the region, the effect of the displacement of lightweight waste by the wind has been neutralized. It is important to note that the suggested burial ground is far from natural drainage, which makes the area suitable for landfill for hydro geological watershed purposes. The results of the environmental impact assessment also showed that the project has a positive impact of about 45%. Therefore, the proposed site is well-suited to environmental standards.

Tourism is the sum of the phenomena and interactions resulting from the interaction between tourists, capital, governments and host communities, universities and non-governmental organizations, in the process of attracting, transporting, accommodating and controlling tourists and other visitors. Over the past 6 decades, the tourism industry has experienced continuous development and diversification, which has become one of the largest and fastest growing sectors of economic growth in the world. Turkey was ranked sixth in the world in tourism in 2011, so the number of Russian tourists entering Turkey was more than 3 million in 2011 alone, despite our potential for attracting tourists. It has yet to achieve its true status at the regional or even global level. Antalya Free Beaches (Turkey) attracted about 9 million tourists in 2011, while Qeshm, despite all its strengths in the field of tourism, failed to attract tourists.
The purpose of this study was to compare analytical analysis of Qeshm and Antalya in order to present tourism development strategies. The research method is descriptive-analytical and reliant on SOWT model and library and documentary studies and field and authoritative field and journals.

The present research deals with the introduction and simulation of viscoelastic effects in transient flows in polymeric pipes widely used in pipe network. The viscoelastic properties result in appearing newterms in transient flow governing equations which are generally absent in available models. In this study, the governing equations are rewritten and manipulated for considering the viscoelastic properties. The equations are then solved using the method ofcharacteristics coupled with the finite difference method. In order to calibrate the unknown parameters including the unsteady friction and creep coefficients as well as to verify the model, a model of viscoelastic pipe network was made at the hydraulics laboratory of Water Sciences Engineering department of Shahid Chamran University. The configuration of the experimental set-up consists of a pipe network with six square loops, having each loop 3m×3m. The pipes are made of PE with 50 mm nominal diameter and 5.5 mm of wall thickness. The data of dynamic pressure oscillation during these transient events were collected by Pressure transducers. Appling the inverse transient analysis method and with the aid of a genetic algorithm, the friction and creep coefficients of the experimental pipe are determined. The results show that the classical water hammer solver cannot accurately analyze the transient flows in polyethylene pipes. In fact, modeling both dynamic effects of unsteady friction losses and viscoelasticity for such pipes is quite necessary. However, it is also found that the viscoelasticity is obviously more effective than the unsteady friction effects in formation and attenuation of transient signals so that, considering onlyviscoelastic effects would result in acceptable responses.

In this paper, a voltage controlled LC oscillator is proposed for various frequency band. In the design of the oscillator, the active inductor has been used with a controllable negative resistance method, which improves phase noise and has low power consumption. The circuit is simulated by ADS. The simulation results in the 0.18 μm TSMC CMOS technology shows that the oscillator has a phase noise of -143.682 dBc/Hz in band 1 (1.2 GHz) and at offset 1 MHz. The adjustable frequency range is from 0.72 to 1.25 GHz. Power consumption in the oscillator core is 2.6 to 3.4 mW, which is supplied from 1.8 volt source. Also, the oscillator has a phase noise of -136.174 dBc/Hz in band 2 (1.57 GHz) and at 1 MHz offset. The adjustable frequency range is 1.29 to 1.85 GHz. Power consumption in the oscillator core is also 2.6 to 3.5 mW. The simulation results indicate that the power consumption has been reduced by about 50%, and the phase noise has been improved by 16% to -136.174 dBc/Hz.

In this study an intelligent system based on machine vision, Multilayer Perceptron (MLP) artificial neural network and Partial Least Square (PLS) models was developed to estimate the L*, a*, and b* values for saffron samples utilizing their RGB color values. Color images of 33 saffron samples (165 images) and 150 color images of standard colored plates were captured utilizing the developed machine vision system. In order to extract RGB parameters, the images were processed using image processing algorithms. Also, L*a*b* values of each sample was measured using a commercial colorimeter (Hunter Lab, color Flex, USA) in triplicate and the measurements were averaged to obtain the final values. RGB values and their linear transformations were set as the inputs of the models and L*, a*, and b* values were set as model outputs, respectively. Experimental results showed that the performance of MLP models were better than those of PLS, with high correlation coefficients of cross validation (R2 and RMSE values equal to 99% and 0.769, 0.953, and 0.785, respectively). Finally, it can be stated the capability of machine vision technology for color quality evaluation of saffron.

Stilling basins are the most common structures for energy dissipation downstream of spillways. A properly designed stilling basin can ensure 60–70% dissipation of energy in the basin. The purpose of this study is to evaluate the performance of perforated end sill and effect of the sill on characteristics of hydraulic jump. The perforated sills with different heights and four ratios of opening 12, 25, 50 and 75% were tested for three tail water depths. Results of experiments confirmed significant effect of the perforated sill on dissipation of energy, reduction of the basin length and reducing dependence of jump location on tail water depth. Based on experimental observation, in a constant Froude number, decreasing of the tail water depth causes the hydraulic jump to move forward toward the end of the basin. In this case, to control the jump and to avoid the hydraulic jump being swept out of the basin, sill distance is decreased. Also, observation showed the sill height needs to be increased as inflow Froude number increases and tail water decreases. In the other words, relative sill height increases up to 30% as tail water depth ratio decreases from 1 to 0.8. Furthermore, the results showed that sills with the 50% opening in comparison with other openings have most effective in energy dissipation and reduction of the hydraulic jump length. The comparison of stilling basin with perforated sill and free jump indicated that the sill with perforation ratio of 50% dissipated 60–90% of water energy in inflow Froude number range of 4.5-12. Moreover, once Froude number increases from 4.5 to 12, stilling basin length increases about 19% for this perforated sill in the tail water depth ratio of 1.

Rectangular orifices are considered as a common structure for discharge measurement in hydraulics. The purpose of the present research is to investigate the effect of the ratio of length to width of rectangular orifices with same surface area on discharge coefficient. Different rectangles are examined as orifice while the aspect ratio in one of them is equal to 1.618 (golden ratio). Golden ratio is a special number which can be frequently existed in nature and this study attempts to find the probable specialty of this ratio in hydraulics. So, the experiments were carried out on five rectangle orifices that the ratio of length to width of ones varied from 1 to 16. Also, a comparison between the discharge coefficient of rectangular and circular orifices is performed. Therefore, the number of 94 tests was conducted on the orifices in the discharge range of 0.136 - 0.637 L/s. A mathematical relation is developed as pressure distribution coefficient in order to account the effect of non-hydrostatic pressure distribution under low head condition. Results of the experiments showed that the increasing of aspect ratio generally leads to increase discharge coefficient so that discharge coefficient of orifices with variation of the ratio of length to width changes about 11.7%. Furthermore, it is illustrated that golden ratio doesn’t have any specialty in flow evacuation and the discharge coefficient of circular orifices is equal to minimum discharge coefficient of rectangular orifices.

Kinetic energy of the water over large spillways should be dissipated in the stilling basins by generation of a hydraulic jump in order to prevent scouring of riverbed and damaging the downstream structures. There are many types of stilling basins, and the most popular ones in practice are the standard USBR basins. The purpose of this study is to evaluate the behavior of perforated and continuous sills in stilling basin as well as their effects on the characteristics of a hydraulic jump including jump length and relative dissipated energy. Results of experiments indicate that the perforated sill, in comparison with the continuous one, has a better behavior in controlling and stabilization of hydraulic jump within the stilling basin which increases the energy dissipation and reduces the jump length. Furthermore, the results show that the perforated sill with 50% opening reduces the basin length about 61% of the required basin length for a free hydraulic jump. Moreover, perforated sill basins are able to dissipate 60% of the inflow energy at Froude number 4.5, while dissipation of energy increases to 90% at Froude number 12.

Plunging pools are constructed at the downstream of dam spillways to dissipate the excess energy. The turbulent flow velocity converts to the dynamic pressure due to impact of flow with the pool’s bed. The aim of this research is to determine impact pressure of a vertical jet on plunging pool bed. Hence, the experiments were carried out in four different discharges (ranging from 6 to 27.5 lit/s according to the nozzle diameters), three jet diameters including 4.3, 5.2 and 8.2 cm and four falling heights of 37, 60, 90 and 120 cm. Also the experiments are conducted in similar flow conditions for smooth and rough surfaces, and results are compared. Dynamic pressures were measured with a pressure transducer. The analysis of data showed that increase of jet diameter causes decrement in the dynamic pressure coefficient. Results revealed an increase in dynamic pressures due to roughness of contacting surface. Moreover, variations of jet Froude number and fall length have significant effects on the dynamic pressure coefficient. The impact pressure was the highest in the surface center and was gradually reduced in outer zones.

Transient flow is generated by an instantaneous reduction in flow rate due to rapid valve closure or pump failure in a water network. Transient flow creates high and low pressure waves that it may be to damage pipelines. Comparison of experimental and numerical results in previous studies revealed that quasi-steady models with assumption of uniform and 1D velocity profile could not correctly predict the damping process of the pressure waves. So¡ the aims of this study are investigation of velocity profile at the downstream end section of pipeline to give a correct understanding of transient flow dynamics. Also¡ this paper evaluates the ability of the instantaneous acceleration–based (IAB) unsteady friction models to estimate pressure history in transient flow using the method of characteristics. To achieve this goal¡ a pipeline¡ made of PVC¡ with a nominal diameter of 63 mm in the two different lengths of 40 m and 80 m was used. In addition¡ a ball valve at the downstream end was installed to create transient flow. The data of velocity distribution and dynamic pressure oscillation during these transient events were collected by Ultrasonic Doppler Velocimetry and Pressure transducers. Results of experiments indicate existence of inflection points in the base flow velocity profile and the large velocity gradient near the pipe wall. Furthermore¡ the results show that two-coefficient models produce a better match with the experimental measurements. The terms Vt and Vx in unsteady friction models affect the phase shift and the damping of transient pressure waves¡ respectively. Moreover¡ the coefficients of acceleration terms vary from 0.0037 to 0.006 for kt and from 0.0325 to 0.052 for kx.

The security and stability of dams for flood passing through the spillway should be provided. So, kinetic energy of flow over large spillway must be dissipated. One of the energy dissipation structures at downstream dams, are plunging pools. The aim of this paper is to investigate dynamic pressure that is created by the impact of a series of rounded non-submerged jets on a flat plate with the roughness height of 0.8 cm in the angles of the impact of 30, 60 and 90 degrees. This research uses sensors to measure the instantaneous pressure (Pressure transducer) with the ability to record and store the dynamic pressure oscillation of water jet. The results showed that increasing the drop height, average coefficient of dynamic pressure decreases. The extreme dynamic pressures coefficient increased with increase fall height. The mean coefficient of dynamic pressure increases with increasing discharge. As the angle of the impact jet decreases, the dynamic pressures reduce. Also, the roughness increases the dynamic pressure up to 70% in the test interval.

Reuse of wastewater plays a key role in reducing the consumption of water resources. Results show that the use of wastewater in agriculture had a positive effect on sodium absorption ratio and humus soil and improves soil conditions. The aim of this study was to improve the performance of the treatment of industrial effluents for reuse through applying the analytic hierarchy process. In determining the promotion of industries wastewater treatment system, the most important criterion was environment with relative weighting of 43.7%; the best sub-criterion was desired treatment degree with relative weight of 23.6%. regarding to management criteria, the best sub-criterion was sustainable operation with relative weight of 28.8%; for the economic criteria, the sub-criterion was the land requirement with relative weight of 58.2% and finally for technical criteria, the sub-criterion was treatment plant upgrading and development with the relative weight of 38.5%. Therefore, for improving system performance of the industrial wastewater treatment to prevent the accumulation of heavy metals, recycling and increased soil salinity to the level not resulting in soil salinity are recommended as environmental criteria (degree of treatment).

In this study, using sound created by wheat grain passing through a pipe, wheat flow rate was measured. The developed device consists of a hopper, metering device, sound sensor, delivery tube, DC motor and power supply. Several wheat mass flow rates were tested and the sound signal created by the passage of the grain through the discharge tube was measured and transferred to a computer using Data Acquisition Card (DAC). Utilizing MATLAB signal processing toolbox and wavelet transfer functions, it was possible to extract frequency characteristics of the sound signals used as distinguishing features of the different flow rates. Artificial Neural Networks-Multilayer Perceptron (ANN-MLP) and Discriminate Analysis (DA) were used to classify different wheat flow rates. Results showed that by using DA and ANN-MLP it was possible to determine the wheat flow rates with 97% and 89% accuracy from each other respectively.

The Crest of an Ogee spillway with a curved plan is longer than that of one with a straight crest; therefore, its capacity for the overflow at any reservoir level is higher than that of the straight-crested spillway. Thus it is a preferred design in most water ponding projects. The objective of this study was to investigate the degree of its curvature on its hydraulics. This was a achieved on a 1:25 experimental model of the Germ chai ogee spillway at the Hydraulics Laboratory of the Soil Conservation and Water Management Research Institute of the Ministry of Jihadi Agriculture. The results revealed that the cavitation number at any discharge rate was higher than the critical value compared with that of the straight- crested weirs Moreover, the discharge coefficient was lower than that of the other type with an equal crest length.

Every landscape has two principal component or feature of the structure and process, Stone cognitive factors are the main reason for the development of structural elements, especially water; Water as one of the main causes of human life have particular importance in addition to drinking water needs for other purposes related to man and nature. The aim of study is Landscape planning of kiyan (Nahavand) using hydro geological features with an emphasis on sustainable development. Resulted indicated source of kiyan water is characteristic karstic (limestone) and sakhtsia whit the dissolution of Holes (Dolin) in topographical of area, in addition of Precipitation. Snow in these holes to be filled by strong winds and formed spring of kiyan by the gradual melting them. Due to lack of rainfall in recent years recommended the use of existing water resources as we need to be sustainable until enjoy the benefits of it. As a result, for each geographical area should be consistent with sustainability indicators utility diagram ecosystems and human life utility indices will be developed and implemented based on ecological features of the region.

A free overfall offers a simple device for flow discharge measuring by a single measurement of depth at the end of the channel yb which is known as the end depth or brink depth. When the bottom of a channel drops suddenly, the flow separates from sharp edge of the brink and the pressure distribution is not hydrostatic because of the curvature of the flow. In channels with subcritical flow regime, control section occurs at the upstream with a critical depth (yc). Although pressure distribution at the critical depth is hydrostatic, the location of the critical depth can vary with respect to the discharge value. So, the end depth at brink is offered to estimate the discharge. A unique relationship between the brink depth (yb) and critical depth (yc), known as end-depth ratio (EDR = yb/yc), exist. Since a relationship between the discharge and critical depth exists, the discharge can ultimately be related to yb. However, when the approaching flow is supercritical, critical section does not exist. Therefore, the discharge will be a function of end depth and channel longitudinal slope.
In current study, an analytical model is presented for a circular free overfall with different flat base height in subcritical and supercritical flow regimes. The flow over a drop in a free overfall is simulated by applying the energy to calculate the EDR and end depth-discharge (EDD) relationship.
End-depth-discharge relationship: The flow of a free overfall in a channel can be assumed that is similar to the flow over a sharp-crested weir by taking weir height equal to zero. It is assumed that pressure at the end section is atmospheric, and also streamlines at the end section are parallel. To account for the curvature of streamlines, the deflection of jet due to gravity, the coefficient of contraction, Cc, is considered. At a short distance upstream the end section, the pressure is hydrostatic. By applying the energy equation between end section and control section which is at upstream the end section, the flow depth at the end of the channel yb in terms of depth at the control section can be determined.
Subcritical flow regime: In this case, the approach flow to the brink is subcritical for negative, zero and mild bed slopes with critical depth at the control section. Using the definition of the Froude number at critical depth, the discharge can be determined. As the explicit relationship between discharge and depth at the brink don’t exist, a relationship should be presented through regression analysis between discharge and yb using the different values of yc over the practical range of 0.01 to 0.84. In this study, below explicit equation is presented for computing Q*(dimensionless discharge) in terms of ( ): Where d is channel diameter, is the ratio of bottom elevation to the channel diameter and . This equation can be used for different values of over the practical range of 0.06–0.6.
Supercritical flow regime: A critical flow occurs upstream of the free overfall under the subcritical approach flow. However, no such critical flow occurs in the vicinity of the overfall under supercritical flow regime. Therefore, the Manning equation for known value of channel bed slope and Manning’s coefficient is exercised to derive the discharge relationship under the supercritical flow regime. Since an explicit equation for discharge in term of yb is impossible, a direct graphical solution for discharge for known end depth, channel bed slope, and ratio of bottom elevation has been provided for supercritical flow regime.
The free overfall in a circular channel with flat base has been simulated by the flow over a sharp-crested weir to calculate the end-depth ratio. This method also eliminates the need of an empirical pressure coefficient. The method estimates the discharge from the known end-depth. In subcritical flows, the EDR has been related to the critical-depth. On the other hand, in supercritical flows, the end-depth has been expressed as a function of the longitudinal slope of the channel using the Manning equation. The mathematical solutions allow estimation of discharge from the known end-depth in subcritical and supercritical flows. The comparisons of the experimental data with this model have been satisfactory for subcritical flows and acceptable for supercritical flows.

In the present study, Co1-xZnxCr2O4 nano-pigments have been successfully synthesized via polymeric precursor method. The phase analysis was carried out by X-ray diffraction (XRD) indicating that all the samples have cubic spinel structure. SEM images showed that the grains are homogeneously individualized with a particle size of between 100-200 nm. Furthermore, UV-Vis absorption spectra exhibited an intense broad band in the eange of 500-700 nm, which could be related to 4A2(F)→4T1(P) spin-allowed electronic transition of Co2 ions in the tetrahedral position of spinel structure. On the bedrock of colorimetric properties and UV-Vis-NIR reflectance measurements, Zn2 enrichment of spinel structure up to 75% resulted in enhancement of chroma and green hue as well as improvement of NIR solar reflectance. High NIR reflectance properties for these pigments clearly highlights the potential for the utility of these pigments in the cool coatings.

In this research, silver selenide (Ag2Se) quantum dots were synthesized via artificial atoms method and the effect of reaction ratio on the final structure was evaluated. The crystal phases, photophysical properties, morphology, and the stability of nanoparticles were investigated using comprehensive analyses such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FT-IR), UV-Vis optical absorption, and photoluminescence (PL) spectrometer. The XRD patterns revealed that the Ag2Se nanocrystals obtained from the ratio of AgN 3:Se,1.35:1, had Orthorohmbic structure with average crystallite size of 6.8 nm. Moreover, this sample also exhibited spherical particles with high shape uniformity, optical bandgap of 2.32 eV, and the good stability in 20:80, cyclohexane: chlorobenzene dispersion.