فهرست مطالب

  • Volume:32 Issue: 3, 2019
  • TRANSACTIONS C: Aspects
  • تاریخ انتشار: 1397/12/10
  • تعداد عناوین: 14
|
  • B. Farokhi *, M. Rezaei, Z. Kiamehr, S. M. Hosseini Pages 354-359
    In this study, polyethersulfone based nanofiltration membranes were modified by air plasma generated through dielectric barrier discharge to increase the membrane hydrophilicity aiming to improve the separation and antifouling characteristics. The effect of plasma time on the physico-chemical and separation properties of membrane was investigated. The PES nanofiltration membranes were fabricated by the solution casting technique associated with phase inversion method. The FTIR spectra showed formation of imine and amine functional groups on the membrane surface. The water contact angle decreased form 58 ° to 31 ° by plasma treatment which produces more hydrophilic surface. SEM and SOM images demonstrated that the surface morphology was changed due to ions collision with membrane surface bombardment. AFM results indicated that membrane roughness was initially enhanced by plasma treatment up to 1 minute, and then decreased again by a further increase of treatment time. Membrane water flux increased from 10.05 (L/m2.h) to 35.17 (L/m2.h) remarkably by plasma treatment up to 1 minute and then decreased again at longer treatment times. An opposite trend was observed for the salt rejection of membranes. The water flux was enhanced ~270% for the modified membrane at 2 min plasma treatment whereas rejection declined less than 18%.
    Keywords: Surface modification, High Water Flux, nanofiltration membrane, Plasma treatment, Physico-chemical Property
  • M. Khajiyan Sheini Pour *, M. Abdideh Pages 360-365
    Various chemicals can have different effects on the properties of the cement slurry. In this paper, the different effects of L-ascorbic acid have been investigated on the important parameters of cement slurry made from class G oil well cement. These parameters included the amount of free fluid, rheological properties, Thickening Time, and compressive strength. Several cement slurries were made with different dosages of L-ascorbic acid. By increasing the amount of L-ascorbic acid, free fluids were decreased and rheological properties of the slurries were improved. This improvement in the amount of free fluid and rheological properties continued with an increase of L-ascorbic acid. Increasing the dosage of L-ascorbic acid to 0.03% by weight of cement, decreased the thickening time and increased the compressive strength. In other words, L-ascorbic acid acted as an accelerator up to 0.03% by weight of cement and would have the role of a retarder in higher value.
    Keywords: L-Ascorbic Acid, Oil Well Cement, Free Fluid, Thickening Time, Compressive strength
  • P. Narasimha Reddy *, J. Ahmed Naqash Pages 366-372
    Kashmir is located in a region where winter temperatures are very low. During the winter months, the temperature in Kashmir is often below 0⁰ C. Generally concrete placed in colder regions with the help of insulated forms as well as heaters to protect freshly mixed concrete against freezing. These practices try to incorporate unnecessary carbon and leads to an disagreeable carbon footprint. The aim of this study was to evaluate the placing of concrete in colder temperatures with the help of antifreeze admixtures rather than insulated forms or heaters. The objective of this study was to optimize the proportions of two admixtures (Sodium nitrite, Potassium carbonate) to be used in cold weather concreting. Concrete specimens were tested to evaluate the properties such as Strength and elastic properties. The samples were cast in two phases i.e. in exterior winter conditions and under controlled conditions of -5°C with varying proportions of the admixtures. When compared to mixes without antifreeze admixtures the results showed increase in the strength of the concrete samples with addition of 3% Potassium carbonate as well as 3.5% Sodium nitrite by weight of cement was found to be optimum for the temperature range in consideration.
    Keywords: Cold Weather Concrete, Elastic properties, Mechanical properties, Antifreeze Admixtures
  • M. Gharib, M. A. Arjomand *, M. R. Abdi, A. Arefnia Pages 373-380
    Use of soft clay soils in construction activities has faced many problems. Some improvement, stabilization, and reinforcement methods is required to use these soils in body of roads, sub-foundations and embankments. In this research, the effect of chitin nanofiber and rice husk ash as additives on the behavioral properties and bearing resistance of soft clay soils by considering the processing time of 7, 28, 42 and 90 days was investigated. The suitability of chitin nanofiber to be used as an additive was evaluated by FTIR, XRD and SEM analysis. Different percentages of additives (1, 2, 4, 6 and 8%) with variations in chitin nanofiber and rice husk ash ratio were added to soil containing 6% lime. Maximum reduction on liquid limit and plastic index was obtained by addition of 2% additives to the soil containing 6% lime in which the percentage of chitin nanofiber was more than rice husk ash. Using examined additives in clay soil resulted in to a significant increase in bearing resistance, specifically at higher percentages of additives and curing times (days). As a whole, obtained results confirmed the potential use of chitin nanofiber and rice husk ash as additives for the improvement of soft clay soils.
    Keywords: Soft Clay Soils, Chitin Nanofiber, Rice Husk Ash, Bearing Resistance, Atterberg limit
  • F. Eslami, Chalandar, M. Valinataj *, H. Jazayeri Pages 381-392
    Reversible logic is one of the new paradigms for power optimization that can be used instead of the current circuits. Moreover, the fault-tolerance capability in the form of error detection or error correction is a vital aspect for current processing systems. In this paper, as the multiplication is an important operation in computing systems, some novel reversible multiplier designs are proposed with the parity-preserving property which will be useful for error detection. At first, two optimal signed serial multipliers are presented based on the Booth’s algorithm and its enhanced version called the K-algorithm, utilizing the new arrangements of reversible gates. Then, another low-cost serial multiplier is proposed based on the conventional Add & Shift method to be utilized in the applications in which unsigned numbers are used. Finally, a new signed parallel multiplier is proposed based on the Baugh-Wooley method that is useful for speed-critical applications. The comparative results showed that the proposed multipliers are much better than the existing designs regarding the main criterions used in reversible logic circuits including quantum cost, gate count, constant inputs, and garbage outputs.
    Keywords: Reversible logic, Parity-Preserving Gates, Multiplication, Booth’s algorithm, Error detection, Fault-tolerance
  • M. Shiravi *, B. Ganji, A. Shiravi Pages 393-399
    One of the main challenges in developing magnetic resonance imaging (MRI) systems is to create a static coil that needs to generate magnetic field density along with the characteristics of optimal homogeneity and magnitude size. To do this, two N42 Block PMs are used and the iron core is designed and optimized in accordance with the dimensions of PM pieces using ANSYS Maxwell software. Then, all iron parts are lathed, the yoke pieces and pole spacers are welded. In addition, PM and pole pieces are installed. Finally, measurement is done by Lutron to evaluate the static coil performance.
    Keywords: Magnetic resonance imaging, Permanent Magnet, Static Coil, Inhomogeneity
  • E. Av?ar Aydin * Pages 400-404
    A low-cost and portable vector network analyzer (VNA) which covered operating frequency between 1MHz to 3GHz is used for vector reflection coefficient and standing wave ratio (swr) of the various microstrip antennas. This paper presents measurements of various ultra wideband (uwb) microstrip antennas for applications in biomedical field. Selection of antenna is an important key for detection of different situations in biological signals. Measurements of antennas were performed by using miniVNA Tiny which operates by radiating an electromagnetic wave through an antenna and measuring standing wave ratio (swr) and return loss. However, the miniVNA Tiny is low-cost components and easy-to-produce antennas. The results indicate the good performance for UWB systems, especially microwave medical imaging applications. However, this device may enable for a low cost stepped-frequency system for use in tissue spectroscopy, field monitoring, and potentially in breast tumor detection.
    Keywords: Reflection coefficient, Standing Wave Ratio, Low-Cost Vector Network, Microstrip Antenns, Ultra Wideband
  • M. Mansoursamaei *, A. Hadighi, N. Javadian Pages 405-412
    The paper describes the usage of the fuzzy Mamdani analysis and Taguchi method to optimize the tourism satisfaction in Thailand. The fuzzy reasoning system is applied to pursue the relationships among the options of a tour company in order to be used in Taguchi experiments as the responses. In this research, tourism satisfaction is carried out using L18 Taguchi orthogonal arrays on parameters such as budget, duration, hotel-choices, travel-options inside the country and theme of the travel are analyzed for one output objective as satisfaction. The output of the fuzzy reasoning system is used as an input in the response of each experiment in Taguchi method. But, the improvement is used for the mean de-fuzzified output in the same experiment. The result is estimated using Taguchi-Fuzzy application and if companies focus on the selected options, it is most probable to achieve more than 90 percent of satisfaction.
    Keywords: Multi-Objective Optimization, Taguchi Fuzzy-based, tourism industry, Satisfaction
  • Z. Akbarzadeh, A. H. Safaei Ghadikolaei *, M. Madhoushi, H. Aghajani Pages 413-423
    In recent years, taking advantage of LARG supply chain (SC) paradigm, a combination of four paradigms (clean, agile, resilience and green) has been increasingly employed. For capturing the advantages of LARG in SC, companies needed to recognize proper practices and implement them with appropriate planning and infrastructure. However, one of its deficiencies is lack of proper method in the prioritization of the LARG paradigms and practices as well as explanation of their relationship. Hence, the main contribution of this paper is to present a comprehensive approach to deal with inherent vagueness and uncertainty of the human decision process using fuzzy set theory, it aims to provide a quantitative basis via a hybrid fuzzy multi-criteria decision making (FMCDM) model that will make easy data collection and shall decrease the calculation. This model combines fuzzy decision making trial and evaluation laboratory (DEMATEL) with fuzzy analytical network process (ANP), i.e. FDANP, to determine the global weights of paradigms and practices and develop their impact relation map. Finally, the implementation of practice was prioritized by using interpretative structural model (ISM). It should be noted that, to measure the efficiency of this method, Iranian dairy industries as a case study was considered. With the help of obtained results, it can be determined the most and the least important practices and paradigms and prioritization of their implementation.
    Keywords: LARG Supply Chain, LARG Practices, FDANP Technique, ISM, Dairy Industries
  • S. E. Rezaei, S. K. Sadrnezhaad * Pages 424-429
    Fe is an impurity in most leach liquors. Its coexistence with copper in leaching solution of chalcopyrite (CuFeS2) which is the most important mineral of copper creates major extraction problems. Hydrochloric acid dissolves both copper and iron during chloride leaching of this mineral. Separation of Fe from Cu is thus necessary to obtain pure copper. This paper presents a novel method for precipitation of Cu over Fe from mixed chloride acidic liquors. Hydrofluoric acid is used as the major unraveling agent. Kinetic studies show that a second-order CuCl2 precipitation reaction with a chemical rate constant of k = 0.416 L/mol prevails the process at the room temperature. For validation of the results, precipitate characterization by x-ray fluorescence (XRF) and x-ray diffraction (XRD) and solution analysis by atomic absorption spectrometry (ABS) are performed. Nitrogen presence is shown to help separation of iron from copper. The optimum value of pH (1.09) is achieved when nitrogen helps parting of 99 % iron II ions in the solution and sole deposition of copper II chloride precipitate.
    Keywords: Chalcopyrite, Chloride Leaching, Copper-Iron Separation, CuF2 Deposition, Reaction mechanism
  • A.R. Toloei *, H. Asgari Pages 430-437
    In this paper, a quaternion-based finite-time sliding mode attitude controller is designed for a spacecraft performing high-thrust orbital maneuvers, with cold gas thrusters as its actuators. The proposed controller results are compared with those of a quaternion feedback controller developed for the linearized spacecraft dynamics, in terms of settling time, steady-state error, number of thruster firings and their fuel usage. It is then proved that the sliding mode control has enough robustness against disturbances as well as a high accuracy in attitude tracking and also a low number of thruster firings. A 6 degree of freedom (DOF) total simulation, including spacecraft dynamics, guidance, navigation and control systems is also designed and the sliding mode controller performance in a sample transfer from an ecliptic orbit to a circular one is investigated. In order to solve the chattering problem caused mainly because of the discontinuity of sliding mode control algorithm and multiple switching on sliding surfaces, the sign function in the control input is replaced with a hyperbolic tangent function. Being aware of the advantages of sliding mode control method, using this algorithm in orbital transfers seems to be innovative and efficient.
    Keywords: Attitude control, Orbital maneuver, Spacecraft, Sliding mode, Quaternion
  • E., A. Attia, K. Khader *, O. Nada Pages 438-444
    Controlling the occurrence of defects is a major challenge for manufacturing organizations that are seeking to enhance their competitive position in today’s global market. This paper considers the process of screen-printing T-shirts using hydraulic and pneumatic printing machines. Several defects in the output of this printing process have been observed, especially with multi colors printing as well as maintenance problems. The six-sigma DMADV approach has been implemented to improve the process performance. Modifications of the current printing machine design using mistake proofing principles that have been proposed to prevent or diminish the occurrence of defects. The analysis indicates that manipulation of wrong oriented products of T-shirts printing machines can be considered as the main effective problem results from machines that are driven by hydraulic or pneumatic systems. Consequently, the quality level and productivity are affected. Moreover, some stained products with leakage fluid from the hydraulic systems can appear. Relying on the DMADV process, an effective mechanical mechanism using Geneva cams was used for diminishing these problems. Geneva cams prototype is manufactured to be used in printing machines instead of the hydraulic or pneumatic systems. A prototype of the cams mechanism is used for testing and validating the presented idea.
    Keywords: Six-sigma Process, DMADV Process, Cams Mechanism, Printing Machines, quality improvement
  • M. Abdolalipouradl *, Sh. Khalilarya, S. Jafarmadar Pages 445-450
    In this paper, a new power, heating and hydrogen cogeneration cycle from Sabalan geothermal two wells is proposed and analyzed. In the proposed system, a new double flash cycle and organic Rankine cycle are used for power production. A proton exchange membrane (PEM) is also used for hydrogen production and the domestic water heater is used for heating. The impacts of some design parameters, such as separators pressures, evaporator temperature, pinch point temperature difference and PEM temperature on the integrated system performance are investigated and then optimization is done from exergy point of view for three considered scenarios. According to the optimization results, the value of heating, net output power, hydrogen production and thermal and exergy efficiencies of the cogeneration system are obtained as 15751 kW, 18436 kW, 11.13 kg/h, 29.48% and 65.23%, respectively.
    Keywords: Energy, Exergy Analysis, Sabalan Geothermal Power Plant, Organic Rankine Cycle, Hydrogen production, heating
  • F. Khalvati *, A. Omidvar Pages 451-459
    In this paper, a novel analytical method was developed based on statistical energy analysis framework to evaluate sound transmission loss through ventilated windows. The proposed method was compared to numerical and analytical models available in the literature. Results showed the success and advantage of the proposed model in predicting the acoustic performance of the ventilated window and the proposed method proved itself as a low-cost and high-accurate method. Considering the slit-like effect of the inlet and outlet of the ventilated window and channel attenuation is the distinct feature of the proposed method compared to the existing analytical models. This paper also discussed the effectiveness of the ventilated window in the provision of indoor acoustic comfort according to the different types of the outdoor traffic noise spectra and sound transmission loss. The results showed the acceptance of the indoor noise level made by the ventilated window. To recognize how the effective factors improve the acoustic performance of the ventilated window, the effect of window aspect ratio, channel thickness and opening size on Sound Transmission Class (STC) were studied. The results revealed that the ventilated window with higher aspect ratio and wider airflow channel has a higher STC while widening the opening size reduces the sound insulation.
    Keywords: Ventilated Window, Statistical Energy Analysis, Sound Insulation, Traffic Noise Spectra, Sound Transmission Loss, Acoustic Comfort