International Journal of Engineering
Volume:28 Issue: 8, Aug2015

The gimbal stabilization mechanism system is used to provide the stability to an object mounted on the gimbal by isolating it from the base angular motion and vibration. In this paper the model of one axis gimbal system with dynamics flying object is introduced. The gimbal torque relationships are obtained using Newton’s second law equation on the assumption that gimbal is rigid body. The system is modelled using Simulink MATLAB. In fact, the purpose of this research was to analyse effects of flight dynamics on performance of one axis gimbal system. The simulation results are discussed and compared to show the validity of the gimbal system proposed at the flight path. Also, the results show that the gimbal system stabilizes the line of sight even when the disturbance torques effect on the system performance.

In this study, Lipase from Aspergillus niger after extraction of medium culture was precipitated with different percentages of acetone and purified by ion exchange chromatography using SP Sepharose HP and Q-Sepharose HP. The process of purification of the enzyme was studied by electrophoresis and the molecular weight was detected and determined by Zymography using overlying containing phenol red and Rhodamine B. The results showed that the vast majority of lipase from this strain has been precipitated by 70% saturation acetone, and leads to the 1.67 fold the purified enzyme, with special activities 32.8 U. mg-1 and efficiency of 38.5%. Using two-phase chromatography, enzyme specific activity reached 246.47 U. mg-1and 12.59-fold purification were achieved. The results of Zymography and electrophoresis indicate a lipase band with weighing about 30 kDa.

In this study, the adsorption of mercury ions by Sargassum bevanom (S. bevanom) by batch method was investigated.SEM was used to study the surface morphology of the biosorbent. The optimum operating parameters such adsorbent dosage, contact time, and pH, were obtained as:a biomass dose of 0.4 g in 100 ml of mercurysolution, contact time of 90 mins and pH 7, respectively. Three equations Morris –Weber, Lagergren and pseudo second order are tested to verifythekinetics of the adsorption process. The data are well explained by the model of Weber Morris. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevichare subjected to sorption data to estimate sorption capacity that the Langmuir model indicatedbetter performance in the fitting of equilibrium data.Also, the thermodynamic parameters indicated that the adsorption process of mercury by S. bevanom is spontaneous and endothermic.Artificial Neural Networks (ANN) was used to predict the adsorption efficiency for the removal of mercury ions that the ANN model can estimate the behavior of mercury removal process.

L- asparaginase enzyme is a renown enzyme because of its chemotherapeutic properties. This enzyme may also be employed in food processing technology. The present study aimed, optimizing the agitation and aeration rate in L-asparaginase production, using C. utilis, ATCC 9950 in batch fermentation system. Beet molasses used as the carbohydrate source for enzyme production. A maximum asparaginase activity of 245.6 U/ml obtained after 20h of fermentation under optimal condition of 1.25 vvm aeration rate and 300 rpm agitation speed. Purification of the enzyme was also done by Acetone Precipitation and column chromatograph. Purified L-asparaginase revealed molecular weight 75 kDa and 82.7 % yield with 10.02 fold increase in specific activity.

Global warming and consequently climate change are important topics studied extensively by researchers throughout the world in the recent decades where changes in climatic parameters are investigated. Considering large-scaled output of AOGCMs and low precision in computational cells, uncertainty analysis is one of the principles in hydrological studies. For this reason, the uncertainty due to precision of computational cells and in passing from global scale to regional scale through LARSWG model and CRU institute, precipitation changes in Mashhad synoptic station located in Ghareghom basin were analyzed. The results showed enough ability of the model to simulate precipitation parameter in the base period. Downscaled output of HadCM3 generated by CRU with high precision shows gradual decreasing of precipitation trend for frequency and sum values. Comparing the downscaled output of the AOGCM with 2.5*3.75 resolution and the output of CRU with 0.5*0.5 resolution, the uncertainty is due to precision of computational cells from global to regional scale which the latter scale is closer to real values.

Open channel junction is one of the most common hydraulic structures that are used in various practical situations such as sewer, drainage, and flood control systems. Knowing the fluid flow behavior, is one of the most important topics in designing the efficient open channel junctions. The complexity and deviation of flow in the junction’s zone disrupts the proper functioning of the flowmeter devices which are located in the cross section and causing error in their measurements. Various three-dimensional Computational Fluid Dynamic (CFD) models were developed in this paper in order to study in the velocity field and flowmeter accuracy of junctions in different hydraulic conditions and confluence angles. The results showed that by increasing the confluence angle, the junction’s downstream flow becomes more complicated, and consequently, the difference between the flowmeter measured discharge values and the real discharge value becomes greater. For the junction with 30° confluence, the flowmeter discharge prediction error is equal to 2 and 6.45% in the junction’s upstream and downstream, respectively. These values increase to 6 and 38.65% for the junction’s upstream and downstream with 90° confluence, respectively.

Stone columns are extensively used and most popular techniques in soft calys and loose sands to improve the ground which is used for embankments, raft foundations, oil storage tanks etc. where a relatively large settlement is permissible. This ground improvement technique has been successfully applied to increase the bearing capacity and to reduce the settlement of foundations. The stone columns not only act as reinforcing material increasing the overall strength and stiffness of the compressible soft soil, but also they promote consolidation through effective drainage. In the present study, the stone columns were reinforced by providing lateral circular discs of geogrids within the column. The circular discs were placed at two different spacing (D and D/2) over full column length and investigated the effect of reinforcement to improve the properties of the clay bed. It has been observed that reinforcing the column with the circular geogrids improves the load carrying capacity of the quary waste stone column and reduce the setlements.

In this paper, a new hybrid methodology is introduced to design a cost-sensitive fuzzy rule-based classification system. A novel cost metric is proposed based on the combination of three different concepts: Entropy, Gini index and DKM criterion. In order to calculate the effective cost of patterns, a hybrid of fuzzy c-means clustering and particle swarm optimization algorithm is utilized. This hybrid algorithm finds difficult minority instances; then, their misclassification cost will be calculated using the proposed cost measure. Also, to improve classification performance, the lateral tuning of membership functions (in data base) is employed by means of a genetic algorithm. The performance of the proposed method is compared with some cost-sensitive classification approaches taken from the literature. Experiments are performed over 37 imbalanced datasets from KEEL dataset repository; the classification results are evaluated using the Area Under the Curve (AUC) as a performance measure. Results reveal that our hybrid cost-sensitive fuzzy rule-based classifier outperforms other methods in terms of classification accuracy.

In this research, WO3 and Au-WO3 thin films were prepared at different temperatures using the sol gel method. The effect of gold nanoparticles (GNPs) on the electrochromic properties of W 3 was also studied. 2.5 nm GNP was synthesized through sodium citrate reduction of gold chloride in an aqueous solution. These films were characterized by XRD, SEM, TEM, and spectrophotometer analyses. The films annealed at 200˚C were amorphous and crystallized at high temperatures. According to the scanning electron microscopy (SEM) image, the films annealed at 200˚C were dense. Moreover, the particles were uniformly distributed on them. Spectrophotometer analysis of WO3 thin films annealed at 200˚C showed high electrochromic properties (transmission modulation (ΔT) was 72% and response time was 3.25s for 80% coloring). Spectrophotometer analysis of Au-WO3 thin films annealed at 200˚C showed that their coloration properties increased (ΔT = 78%) and response duration decreased (1.65s) when gold nanoparticles were added. This enhancement is attributed to the increased conductivity caused by the addition of gold nanoparticles as well as the surface plasmon resonance based absorption of GNPs.

Improving performance of the plant layout requires careful consideration of various factors including changes in flows between departments over time and design of transportation system. This paper primarily presents a comprehensive dynamic layout design model which involves the design of facility plant layouts problems based on a multi-period planning horizon. The presented model integrates layout and transportation system design via considering more realistic assumptions, such as taking account of fixed-position departments and distance between departments that endanger each other. In addition, specific criteria such as capacity, cost and reliability of facilities are considered in transportation system design decision. The combinatorial nature of the problem necessitates using a meta-heuristic approach to deal with this issue. Therefore, an efficient hybrid meta heuristic based on variable neighborhood search (VNS) and simulated annealing (SA) is proposed to design a proper dynamic layout for a specific planning horizon. The validity of the superiority of the proposed solution method is proven through comparing with all of the other solution methods upon the original model available in the literature. Finally, an extensive computational results lead to the conclusion that the proposed method outperforms other existing methods. In addition, solving an example from the dynamic layout design of a home appliance manufacturer demonstrates the efficiency of the proposed model and solution algorithm in terms of solution quality to solve real-world instances.

A profile is a relationship between a response variable and one or more independent variables that can describe the quality of a process or product. On the other hand, for an in-control process, capability indices are criteria for process quality improvement that allows meeting customer expectations. Although a considerable number of applications and monitoring methods have been already proposed for profiles, a few researches have focused on the process capability index of profiles. In this paper, we propose a new Spmk index to measure process capability when the quality of process is characterized by a logistic regression profile. In addition, we present an approximate 100(1-α)% confidence interval based on percentile bootstrap method. The performance of the proposed index and corresponding confidence interval is evaluated through simulation studies. The result shows that when the number of observations in each level increases the index performs better. Furthermore, increasing number of levels leads to improving precision of the proposed index. Also, the coverage rates of the confidence intervals are greater than 93.6% lower limit of the stated nominal in most cases. Finally, the application of the proposed index is illustrated through a real case.

In this study, surface of medium carbon steel (AISI 1045) was modified by titanizing followed by plasma nitriding. Titanizing was performed using pack cementation method, in a pack mixture of ferrotitanium, ammonium chloride and alumina, at 950 °C for 45 and 180 min. Plasma nitriding was conducted at two temperatures of 530 and 550 °C for 5 h, in a gas mixture of 75N2+2 H2 (vol.%). The samples were characterized by scanning electron microscope (SEM), X-ray diffractometre (XRD), Vickers microhardness and pin-on-disk wear tests. The thicknesses of titanized layers was 8-10μm, the thicknesses had no significant change after plasma nitriding. The duplex treated surface layers consisted of Fe4N, TiN and TiCN phases. Lower titanizing time and higher plasma nitriding temperature provided superior wear resistance and hardness. The highest wear resistance and the lowest friction coefficient were achieved in the sample which was titanized for 45 min and then plasma nitrided at 550 °C, with 2130 HV microhardness.

Combustion in homogeneous charge compression ignition (HCCI) engine is controlled by auto ignition of well-mixed charge of fuel, air and residual gas. Since onset of HCCI combustion depends on the auto ignition of fuel/air mixture, there is no direct control on the start of combustion process, therefore, HCCI combustion becomes easily unstable especially at lower and higher engine load. Charge stratification has the potential to extend the load limits of HCCI combustion by improving the control over the combustion phase as well as reducing the maximum pressure rise. In this study, a combination of experiment and numerical simulation is carried out to investigate the effect of fuel stratification using reformer gas and EGR on HCCI natural gas combustion. Results show that fuel stratification in this case increased the autoignition property of natural gas. On the lean operation boundary, reformer gas and EGR blending enhanced the autoignition by advancing combustion timing at identical initial conditions compared to pure natural gas that expanded the lean boundary of the operating region.

Radial forging is an open die forging process used in reducing the diameters of shafts, tubes, stepped shafts and axles in addition to creating internal profiles such as rifling the gun barrels. The radial forging of tube is usually performed over a mandrel to create an internal profile and/or size the internal diameter. Most of the previous studies conducted on the radial forging process have used axisymmetric models. In this study, the residual stresses of a short hollow tube in a cold radial forging process is assessed through 3-D finite element simulation. The mandrel used here contains six helical grooves and two steps along its length. This kind of mandrel is innovated in this research. The workpiece is modeled as an elastic-plastic material and the commercial finite element software, ABAQUS is used to simulate the process. The accuracy of the finite element model is tested by comparing the predicted results with available experimental works and is validated by both the slab and upper bound methods. Residual stresses in the radial forged product and influence of the process parameters on stress distribution, such as workpiece motions, friction and percentage of reduction are studied to determine the optimized parameters of simulation and improve the condition of this process.

Non Uniform Rational B-splines (NURBs) have proved to be very promising for metamodeling in engineering problems, because they have unique properties such as local modification scheme, strong convex hull property, and infinitely differentiability, etc. Since NURBs are defined by control points, knot vector, and weights associated with control points, the precision of NURBs is influenced by all of the parameters. In order to improve the accuracy and calculation efficiency, an enhanced method of building NURBs metamodel is presented. Some improvements are made in certain aspects, such as: improving the date normalization method and the calculating method of weight coefficient. Compared with the existing methods, this method can calculate the weight coefficient of each control point more quickly, because it avoids the inverse operation of correlation matrix, which may cause singular. Several classic numerical examples show that the presented method is effective for building approximate model with higher accuracy than existing NURBs metamodel.

The buckling torque may be much less than the yield torque in very thin rectangular tubes under torsion. In this paper, simple closed-form formulae are presented for buckling analysis of long hollow rectangular tubes under torsion. By the presented formulae, one can obtain the critical torque or the critical angle of twist of the tube in terms of its geometrical parameters and material constants. First, an approximate function for critical angle of twist, including a part in terms of the Poisson’s ratio and another part in terms of geometrical parameters with unknown coefficients are considered. Then, the unknown coefficients are found by a minimax optimization method and also by using the accurate results obtained by the finite element method. The formulae can be used for a wide range of dimensions of hollow rectangular tubes. The numerical studies show that the maximum error of the presented formulae is less than 10%.

H∞ controller for active magnetic bearings (AMBs) with flexible rotor system was designed in this paper. The motion equations of AMBs and flexible rotor system are built based on finite element methods (FEM). Weighting function matrices of H∞ controller for AMBs are studied for both the sensitivity and the complementary sensitivity of H∞ control theory. The experiments are completed on a four-degree freedom magnetic bearings-flexible rotor test rig, and the experimental results show that the H∞ control method has a better ability to depress vibration than traditional PID control. H∞ controller is characterized by the effectiveness of interference immunity and robust stability. The peak to peak vibration amplitudes of flexible rotor are less than 60μm at the first critical speed of flexible rotors, and the results indicate that H∞ controller for the active magnetic bearings with flexible rotor system is stable through the first critical speed of the flexible rotor system.

The regime of nucleate pool boiling near critical heat flux (60-98% of CHF) is known as vapor mushroom regime. Understanding mechanism of heat transfer in regime of vapor mushroom of nucleate pool boiling is not only helpful to explain high rate heat transfer, but also useful to explain boiling crisis phenomenon. In this paper, an experimental setup is designed and fabricated to study the mechanism of heat transfer from boiling surface to bulk liquid near critical heat flux (vapor mushroom regime). In addition, vapor mass frequency and thickness of macro-layer are measured at various heat fluxes in this regime of boiling. The experimental study reveals that individual bubble coalesce due to very high bubble site density and form vapor mass entrapping a relatively thicker film of liquid known as ‘macro-layer’ between the growing vapor mass and the heating surface of pool boiling near the high heat flux region. The rate of evaporation of macro-layer and transient conduction through macro-layer is the prime parameter to transfer heat from the heated surface. The thickness of the macro-layer is found to be lying in the range of 153- 88 μm respectively for range of 60-98% critical heat flux. As the heat flux increases, the thickness of macro-layer decreases. The vapor mass frequency varies from 4 Hz to 8.80 Hz for water in the range of 60-98 % of critical heat flux. The vapor mass frequency increases as heat flux increases due to higher evaporation rate associated with higher heat flux. The data reported in this manuscript are more consistent as comparing to data available in literature and these data are useful in modeling of heat transfer in nucleate pool boiling near critical heat flux.