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Spur gear systems are widely used in power transmission systems in the industry. One of the common defects of the gears is tooth crack. Tooth crack increases the vibration and also generates noise. Previous studies have shown that tooth stiffness will decrease due to any crack and it is important to estimate the magnitude of reduction of tooth stiffness. This research suggests a new analytical approach for crack modeling and determining the reduction of time-varying gear mesh stiffness by Elastic Spring Method (ESM). Based on this approach, two or more cracks can be considered in one tooth. However, previous studies have primarily concentrated on one crack. In addition, it should be voted that each crack is replaced by one linear and one torsional spring in the present study. The results that were obtained from this method are validated through a comparison with Limit Line Method (LLM) and Finite Element Method (FEM). [ABSTRACT FROM AUTHOR]

Spacecraft attitude determination is a crucial task in attitude control subsystems. It provides the necessary feedback to close the control loop. Several sensors such as star trackers, Sun sensors, and horizon sensors are used for this purpose. The development of other methods can help control engineer with newer options to design their systems. Here, an innovative sensor for determining the attitude of a spacecraft is presented. The proposed sensor measures the Lorentz force vector due to the interaction between the magnetic field of the Earth, and the high linear velocity of the spacecraft. This sensor is composed of three series of orthogonal variable capacitors. The capacitors are connected in parallel to increase the total capacitance. The capacitors have movable plates which actuated by alternating current with specific frequency. Due to very high speed of spacecraft relative to magnetic field of earth in low orbit, the Lorentz force is exerted on the charges of the capacitor plates. The plates have same velocity as the spacecraft does. The applied Lorentz force to the plates affects their motion so that the harmonic can be seen in the output. Measuring the amplitude of the mentioned harmonic results in measurement of a component of the Lorentz force in the direction of capacitors. Installing the three capacitors orthogonally can measure the three rectangular components of the Lorentz force. This vector will be in the body frame of the spacecraft. The two-plate and three-plate capacitor are the two different proposed mechanisms and their performance is compared. Once the Lorentz force is known as a vector in the body frame, it can be applied along with data from another sensor to determine the attitude of the spacecraft. Based on simulation results, achievable resolution is better than 3°, which can be improved by further research. [ABSTRACT FROM AUTHOR]

Gear systems are used to transmit power in the industry when accuracy and synchrony are needed and helical gear systems are used in more accurate and high-speed industries. It is important to ensure that these systems work faultlessly, therefore the detection of the crack location and situation is very efficient in the gear systems. In this research, a new approach is proposed to detect the multi crack location and length in the helical gear teeth. To this end, after giving an explanation of helical gear mesh stiffness and demonstrating the helical gear pair dynamic modeling, the transmission error ratio method is used to detect the cracks locations and lengths. Then, according to solved examples, when the cracks locations are far enough that their effects on the transmission error are completely separated, the cracked teeth and the lengths of cracks can be detected exactly, and when the cracks are in adjacent teeth, according to the cracks lengths and depths and their effects overlap, the number of cracks and their lengths can be detected exactly, approximately or absolutely undetectable. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Factors controlling mineralization must be ideally combined during system evolution. • CO 2 degassing with cooling of the system are the important factors for mineralization. • Supersaturation of NaCl in primitive fluids is linked with maximun ore-efficiently. • Signals of high metal fertility as non-unique factors could be seen in other PCDs. Abstract The Cenozoic Urumieh-Dokhtar Magmatic Belt (UDMB) in Iran is considered as one of the major Cu-bearing regions in the world with high potential for the occurrence of giant/large porphyry Cu ± Mo ± Au systems. In the UDMB, porphyry Cu mineralization is strictly associated with Miocene intrusions originating mostly from collisional-related partial melting of subduction-modified juvenile lower crust. In this study fluid inclusion coupled with laser Raman analysis is used to characterize and compare the fluid evolution of the large Meiduk deposit and smaller low grade porphyry copper systems (e.g., Keder, Sarkuh, and Iju) in the UDMB. It can be shown that enhancement of metal fertility of a porphyry system is controlled by several factors: (1) The salinity of early hydrothermal ore fluids; maximum ore-efficiency is seen in porphyry deposits showing supersaturation of NaCl in the pristine high temperature fluids (e.g., Meiduk), (2) Presence of CO 2 and fast exhausting of CO 2 vapor components during early stages of mineralization, (3) Temperature decrease especially during the main ore stage, and (4) High oxygen fugacity (near to the magnetite – hematite oxygen buffer) of the most primitive fluids in the early stages of hydrothermal system. [ABSTRACT FROM AUTHOR]

Time-dependent mesh stiffness is a most important reason of vibration and dynamic excitation in gear sets. In this research, analytical formulas of the helical gear set and the planetary gear system are combined to calculate the time-dependent mesh stiffness of the helical planetary gear system. For this purpose, at the first step, the analytical equations are derived for the spur gear pair. Then by dividing a helical tooth into the several independent thin spur tooth slices, the helical gear pair mesh stiffness is extracted. Finally, these equations are extended to the helical planetary gear system. The suggested analytical results and those which obtained by the finite element method (FEM) are compared and are in good agreement when the helix angle is less than 15 degrees. Also, the helical planetary gear system mesh stiffness in different cases such as fixed carrier, fixed sun gear and fixed ring gears is calculated. These results show that the value of mesh frequency ratio in each case scales the mesh stiffness shapes in the rotation angle direction. In other words, mesh frequency ratio parameter determines the number of meshing period in each rotation of planets. [ABSTRACT FROM AUTHOR]

The aim of the present research was to evaluate the impact of coating layers on release profile from enteric coated dosage forms. Capsules were coated with Eudragit FS 30D using dipping method. The drug profile was evaluated in both phosphate buffer and Hank's solutions. Utilization X-ray imaging, gastrointestinal transmission of enteric coated capsules was traced in rats. According to the results, no release of the drug was found at pH 1.2, and the extent of release drug in pH 6.8 medium was decreased by adding the coating layers. The results indicated single-layer coated capsules in phosphate buffer were significantly higher than that in Hank's solution. However, no significant difference was observed from capsules with three coating layers in two different dissolution media. X-ray imaging showed that enteric coated capsules were intact in the stomach and in the small intestine, while disintegrated in the colon. [ABSTRACT FROM AUTHOR]

A new integrated process of biofuel production is introduced and analyzed. This process consists of lignocellulosic biomass fast pyrolysis, gasification, electrical power generation and latest bio-oil upgrading in biorefinery processes. Upgrading processes include hydrotreating, distillation, hydrocracking and steam reforming units. Biomass is converted to bio-oil, gas and bio-char through fast pyrolysis which is then used in biorefinery and gasification. Simulation results show that 1 kg/s hybrid poplar biomass generate about 0.68 kg/s bio-oil, 0.16 kg/s gas and 0.17 kg/s char. Also 5.62 MW electrical power can be gained from the steam cycle. The excess heat of gasification can be used as a part of the required heat source in the process. Moreover the produced syngas is used in the steam reforming unit to provide the required hydrogen in the refinery. In addition, by heat integration the consumption of hot and cold utilities decreased and consequently the process performance improved. The obtained results show that synthetic biofuel yield is about 0.49 wt% and 0.51 wt% gasoline/diesel blendstocks. Moreover economic analysis, sensitivity analysis was also done to study the effects of major operating parameters, i.e., steam reforming temperature, steam/carbon ratio of gasification and greenhouse gas emission, on the process performance. [ABSTRACT FROM AUTHOR]

Abstract: DNAzyme and aptamer conjugations have already been used for sensitive and accurate detection of several molecules. In this study, we tested the relationship between conjugation orientation of DNAzyme and aflatoxin B1 aptamer and their subsequent peroxidase activity. Circular dichroism (CD) spectroscopy and biochemical analysis were used here to differentiate between these two conjugation patterns. Results showed that DNAzyme–aptamer has more catalytic activity and efficiency than aptamer–DNAzyme. Thereby, DNAzyme–aptamer with its superior efficiency can be used for design and development of more sensitive aflatoxin B1 DNA based biosensors. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a liposomal formulation to selectively target cancer cells. Liposomes were prepared using thin layer method and folic acid (FA) was applied for targeted delivery of 5FU to cancer cells. Liposomes prepared were characterized for encapsulation efficiency (EE%), morphology and their particle size. Cellular uptake, cytotoxicity study and ROS production were evaluated using CT26 cell line. Hemolysis test was performed on rat red blood cells (RBCs). Moreover, the efficacy of targeted liposomes were investigated by in vivo antitumor activity and tissue toxicities were studied by histological examination. The EE% and average particle size of liposomes were 67.88 ± 1.84% and 114.00 ± 4.58 nm, respectively. TEM image revealed that liposomes were spherical in shape. Targeted liposomes showed higher cellular uptake, lower IC 50 (12.02 μM compared to 39.81 μM for liposomal 5FU and 39.81 μM for free 5FU) and higher ROS production than free drug (62,271.28 vs 2369.55 fluorescence intensity) on cancer cells. Results of hemolysis assay confirmed the blood biocompatibility of the liposomes. Moreover, folate targeted liposomes showed better tumor inhibition than free drug (88.75 mm 3 tumor volume vs 210.00 mm 3 ) and no tissue abnormalities were found in histological examination. It can be concluded that folate targeted liposomes provide an effective and safe strategy for colon cancer targeted chemotherapy. [ABSTRACT FROM AUTHOR]