International Journal of Engineering
Volume:33 Issue: 8, Aug 2020

In this work, we model a radiofrequency discharge of hydrogenated silicon nitride in a capacitive coupled plasma reactor using Maxwellian and non-Maxwellian electron energy distribution function. The purpose is to investigate whether there is a real advantage and a significant contribution using non-Maxwellian electron energy distribution function rather than Maxwellian one for determining the fundamental characteristics of a radiofrequency plasma discharge. The results show the evolution of the non-Maxwellian electron energy distribution function, the mobility and the diffusion coefficient required to determine the fundamental characteristics of the radiofrequency plasma discharge of a hydrogenated silicon nitride deposit at low pressure and low temperature, between the two electrodes of the capacitive coupled plasma reactor.  By comparing these results using non-Maxwellian electron energy distribution function with those calculated using the Maxwellian one, we conclude that the use of non-Maxwellian electronic energy distribution function is more efficient for describing the evolution of a radiofrequency plasma discharge in a capacitive reactor, which will improve the quality of the deposition of thin films.

In this research, the generation process of engineered microsphere agarose adsorbent has been explained that has surfaces with different active sites to adsorb protein nanoparticles into the fluidized-bed system. Also, excellent selectivity of protein nanoparticles, high adsorption capacity, and fast equilibrium rate through the eco-friendly polymeric adsorbents were vital aims in here. Hence, agarose as a cheap, and abundant natural polymer, with a ferromagnetic condenser, and dye-ligand adsorbents, were employed to generate the engineered microsphere agarose adsorbent. Then, the performance of produced adsorbents was evaluated in the batch and fluidized-bed system. Scanning electron microscopy, atomic force microscopy, and optical microscope were used. Results showed the shape of adsorbents is spherical, with the size distribution range of 50-250 µm, the porosity of around 90%, and the wet density of 2.6 g/mL. Then, to compare the performance of the engineered adsorbents in a fluidized-bed system, the dye ligand was immobilized on the Streamline™. The obtained results were compared at the same conditions. In batch adsorption tests, the results of lactoferrin nanoparticle adsorption were shown higher dynamic binding capacity with engineered microsphere agarose adsorbents. Also, the results demonstrated that more than 75% of the adsorption process occurred in the first half-hour, which is a very suitable time for a fluidized-bed system. Also, adsorption equilibrium data were evaluated with isothermal adsorption models, and Langmuir’s model suits the data, and the maximum of adsorption was close to 45.3 mg/mL adsorbent. The fluidized-bed adsorption tests showed that engineered adsorbents gained a sound breakthrough performance at high flow velocity and upper dynamic binding capacity compared to commercial adsorbents. The dynamic binding capacity at 10% breakthrough achieved 71% of the flooded adsorption process at the major fluid velocity of 348 cm/h, so the engineered adsorbent has been proved the good potential for use in high flow rate fluidized-bed systems.

The early age shrinkage is responsible for the early age cracking of concrete. It is very critical for durability of concrete. The change in volume of concrete due to evaporation of water or dehydration process is known as shrinkage. To reduce the early age shrinkage utilized the supplementary cementitious material (SCM) in concrete. In present research industrial and agricultural waste byproduct like fly ash (FA) and rice husk ash (RHA) along with cement were used as SCM. The triple blend concrete was prepared by the combination of 20%, 30% and 40% partial cement replacement with FA and RHA for 0.30, 0.35 and 0.40 water-cement ratio. The concrete samples were tested by advanced  instrument as shrinkage cone meter were used for measure the shrinkage. The result shows that the early age shrinkage reduced with increasing the SCM content. The microstructure characteristics enhanced with raising the content of FA and RHA up to 30% replacement; that was due to the dense particle packing.

Brittleness, which was the inherent weakness in High Strength Concrete (HSC), can be avoided by reinforcing the concrete with discontinuous fibers. Reinforcing HSC with more than one fiber is advantageous in an overall improvement of the mechanical performance of the composite. In this experimental study, Hybrid Fiber Reinforced High Strength Concrete (HyFR-HSC) mixes were formed by blending single length glass fiber and single length steel fiber with a total volume fraction of 1.65% into the concrete and Hybrid Graded Fiber Reinforced High Strength Concrete (HyGrFR-HSC) mixes were obtained by mixing different lengths of glass fiber with different length of steel fibers at a total volume fraction of 1.65% into the concrete. A comparative study was made between HyFR-HSC and HyGrFR-HSC specimens to investigate the effect of fiber grading on strength properties and the uniaxial compressive behaviour of HSC with hybrid fibers. In both HyFRC and HyGrFRC mixes, glass fibers improved the pre-peak behaviour, and steel fibers improved the post-peak behaviour of concrete, thereby exhibiting a positive synergy in combining glass and steel fiber into the concrete. Among the two-hybrid FRC’s, HyGrFRC outperformed HyFRC with substantial improvement in both strength and ductility. Among all the HyGrFRC mixes, HyGr9 mix, which contain a higher amount of long-length fibers exhibited better improvement in peak strain, ductility factor, total energy and toughness index. The replacement of single length of fibers with graded length fibers at higher volume fraction in HyFRC is useful in improving workability, thereby providing better fiber dispersion and thus enhances both the pre-peak and post-peak performance of the concrete. From this investigation, it can be inferred that grading of fibers improved the mechanical behaviour of HyFRC by exhibiting positive synergy from both fiber geometry and fiber type.

Modern technology has been used to build tunnels in recent years by means of drilling machines (TBM) that were used for civil engineering work in large cities to reduce the harmful effects of spending on the surface of the earth significantly. To build the tunnel, numerical modeling was used on the basis of the finite element method to predict stress behavior during the tunnel construction process. Tunnel simulation model by using the numerical method (FEM) with the Hoek-Brown model, which includes calculating the behavior of predicting stress-that surrounds the tunnel and analysis during the process of building the tunnel and compared with the natural state of the rocks during the different tunnel construction stages. Vertical stresses at the top and bottom of the tunnel are reduced during the advance of tunneling while horizontal stresses are increased. TBM progression is reflected in phases through one to five by performing an axial symmetric FE analysis, math calculation results revealed significant stress changes occurring in rock regions near the boundary of the tunnel. In other words, proximity to rocks is mostly affected by the tunnel. These pressure variations decrease as you move away from the tunnel horizontally and the seams reach extremely small values for distances greater than (2D) meters from the edge of the tunnel, where D is the diameter of tunnel.

In recent decades, the dual systems of steel moment-resisting frames and RC shear walls have found extensive application as lateral load-resisting systems for high-rise structures in seismically active areas. This paper investigated the effectiveness of tuned mass damper (TMD), viscous damper, friction damper, and the lead-core rubber bearing in controlling the damage and seismic response of high-rise structures with concrete shear walls. Five buildings (10, 15, 20, 25, and 30-story) with passive seismic control systems were analyzed in OpenSees using 50 seismic records. The structural responses (acceleration, drift, displacement, velocity, and base shear) were adopted as the criteria. The criteria were nondimensionalized by defining a measure to establish a relationship between the inputs (ground motions) and outputs (structural responses). At the end, Multi Criterion Decision Making (MCDM) method was employed to rank the passive seismic control systems and select the best one. The results showed application of the multiple-criteria decision-making methods in selecting a seismic upgrading strategy and earthquake engineering.

This paper focuses on the response of circular machine foundation resting on different soils (sand and clay) through studying the variation of soil shear strength parameters and strain with the number of cycles. The objective of the current study is to explore the results related to the parameters of the dynamic load (number of loading cycles and frequency of load) related to the circular footing of a machine on the dynamic shear strength parameters (for sand soil (ϕ˚dyn) and for clay soil (Cudyn)) in addition to the amplitude strain foundation. A special setup was designed and manufactured to simulate the vertical vibration of a circular machine foundation. A steel circular machine foundation with a diameter of 150 mm was used to represent the footing. A total of 6 cases were examined to take into account the effects of different parameters including different frequencies (0.5, 1, and 2 Hz); state of sand (medium and dense) which corresponded to relative densities of (50 and 80%), while the state of clay (medium and stiff) corresponded to undrained shear strengths (50 and 70 kPa).  All tests were carried out under load amplitude of 2.5 kN. It was found that the rate of increase in shear strength parameters for the soil under a circular machine foundation decreases remarkably when increasing the frequency for both types of soil under the footing. While little change in the shear strength parameters, or even no change was observed under the effect of other locations. Moreover, the amplitude strain decreased when increasing the frequency for both types of soil.

In fiber concretes, microcracks in the boundary area between the cement paste and the surface of aggregates or fibers are higher. Natural and artificial pozzolans can be used for reinforcing this area. In this research, the combination of glass fiber, zeolite, and nano silica particles were used in lightweight self-compacting concrete containing scoria. Fiber volume fractions between 0% to 1.5% in combination with  0% to 6% nano silica particles were examined. The scoria aggregates and zeolite were considered constant in all mixes. The fresh and hardened properties of specimens were evaluated using T50, slump flow, V-funnel, L-box, compressive strength, splitting tensile strength, flexural strength, ultrasonic, electrical resistivity, and water absorption tests. Also, the microstructure of concrete was investigated using scanning electron micrograph images. The combined use of nano silica particles and glass fiber increased the splitting tensile strength by about 3 to 56%. Also, the use of nano silica particles increased electrical resistivity by 136 to 194%. Nano silica particles, due to their high specific surface and high reactivity, result in consuming calcium hydroxide that is quickly organized within the hydration, filling pores of the calcium silicate gel structure and eventually producing more and more compacting hydrated products.

Investigating the behavior of the box-shaped column panel zone has been one of the major concerns of scientists in the field.  In the American Institute of Steel Construction the shear capacity of I-shaped cross- sections with low column thickness is calculated. This paper determines the shear capacity of panel zone in steel columns with box-shaped cross-sections by using artificial neural network (ANN) and genetic algorithm (GA). It also compares ABAQUS finite element software outputs and AISC relations. Therefore, neural networks were trained using parametric information obtained from 510 connection models in ABAQUS software. The results show that the predicted shear capacity of the NN and the GA in comparison with the AISC relations use a wide range of all effective parameters in the calculation of the shear capacity of panel zone. Therefore, the use of artificial intelligence can be a good choice. Finally, the GA, along with optimization of a mathematical relation, has been able to minimize the error in determining the shear capacity of panel zones of steel-based columns, even at high column thicknesses.

The cost associated with the application of large volume of cement and synthetic admixtures was one of the major drawbacks of Self Compacting Concrete (SCC), which can be reduced by the use of supplementary cementitious materials (SCM). When the demand of cement reduces, the release of carbon dioxide (CO2) from cement industries will come down, which has a positive impact on global warming. The present paper reports an attempt in this direction by experimental examination on the fresh properties and durability performance of SCC by replacing cement with SCM such as fly ash (FA) and ultra-fine Ground Granulated Blast Furnace Slag (GGBS) in varying ratios. SCC mix was obtained by fixing the water-binder ratio and superplasticizer (SP) dosage with respect to total cementitious content. Along with the Fresh properties, SCC mixes incorporating both alccofine and fly ash at 10 and 25%, respectively; which gave the best fresh properties were selected to assess the durability issues. Incorporating 10% alccofine and 25% fly ash gave the best result in both fresh and durability studies in comparison with other combinations.

Steel-reinforced concrete (SRC) columns, which are classified as composite columns, became the most widely used in recent years; because of their extensive advantages over the reinforced concrete and the steel columns. In this paper, the ductility index and its influential factors were explored to investigate the behavior of SRC columns. A straightforward approach was then proposed by establishing the necessary equations based on the plastic stress distribution method. Accordingly, an experimental program was performed on six SRC column specimens with two H- and cross-shaped steel sections and three eccentricity ratios of 0.4, 0.55, and 0.7. In addition, a finite element model was developed for numerical analysis using Abaqus software, which was verified by the experimental results. A total of 30 columns were thus analyzed for the parametric study where the effects of geometric and material variables, including steel percentage, concrete compressive strength, lateral tie spacing, and geometrical shape of the steel core on the ductility index of these columns were assessed. The results confirm that for the H-shaped column, reducing the lateral tie spacing ratio from 0.6 to 0.2 not only increases the ductility index to as much as 72%, it also induces a post-yield hardening in the load-displacement curve and increases the bearing capacity by 20%. Subsequently, load-bending moment interaction curves were developed according to plastic stress distribution method cited in EC4 Code and then compared with those obtained through the software. Thus, normalized curves were presented as a means to design these columns.

The current study focuses on two main goals. First, with the use of construction and demolition (C&D) of building materials, a new aggregate was produced and it was utilized for green concrete production. The compressive strength test confirmed the good function of C&DW aggregate concrete. This concrete did not show significant differences with natural sand concrete. Second, Backpropagation neural network (BNN) was adjusted for C&DW concrete strength prediction at different curing times. Although BNN has good accuracy for strength prediction, due to the importance of 28th day of concrete strength the need to improve the accuracy was felt. So discrete wavelet transform (DWT) was used on BNN and a hybrid network was produced. DWT by filtering the noises can improve the homogeneity of the dataset. The results of DWT-BNN showed that the regression can increase to 98% and the MSE index reduces to 0.001. Continued research has shown that increasing the number of filters to four steps leads to reduced accuracy and increased computational cost. So using DWT-BNN as a hybrid network with one filter can improve prediction ability to the desired level but adding up the number of filters not recommended.

In Iran, using the hand excavated pits (wells) have been more common compared to other countries. As a matter of fact, recent years, utilizing the dynamic probing test (DPT) in these types of pits has been significantly developed in Iran. This is while the standard state of doing this test is from the ground level. In this work, the dynamic probing test is carried out in two similar wells with diameter of 1 m and the depth of 10 m in two areas in city of Qom in Iran; one has silty sand soil and the other is clay. Then, both tests are simulated using numerical modeling in Abaqus software and the results are compared and calibrated with the values obtained at the mentioned sites. The results show a good agreement between the simulation data and tests done in the sites. After calibrating the simulated values with the values obtained from the site, we perform another simulation, this time, for the standard state (It means that the test is done from the ground level or with the assumption without well), as deep as 10 m and for both areas and with the mentioned soils specifications. The results show 35 and 22 percent difference in the dynamic resistance of cone’s tip between the testing in standard state and hand excavated pit, for silty sand and clay soils, respectively. Finally, using the simulation, we present the relations between the depth of the test point and dynamic resistance of cone’s tip for both states and both types of the soils studied in this paper.

The average life span of knee prosthesis used in Total Knee Replacement (TKR) is approximately 10 to 15 years. Literature indicates that the reasons for implant failures include wear, infection, instability, and stiffness. However, the majority of failures are due to wear and tear of the prosthesis. The most common biopolymer used in TKR  is Ultra High Molecular Weight Polyethylene (UHMWPE). Prevailing research reports that implants are restrained by tiny UHMWPE debris generated by long term friction between the femoral component and polyethylene articulating surface. This necessitates an alternative material with high wear-resistance to reduce the wear rate. Polyether ether ketone (PEEK) is one of the biopolymers expected to possess better mechanical properties and biocompatibility with surrounding tissue and hence can be suitable for orthopedic applications. In this regard, a study on UHMWPE and PEEK biopolymers was carried out and tribological behavior was examined. The effect of process parameters such as normal load and speed on the tribological performance of biopolymers were evaluated. The experiment plan was designed as per Taguchi’s Design of Experiments methodology. An empirical relation between wear and process parameters was established using linear regression analysis. Microanalysis and failure analysis of worn-out surfaces of both the biopolymers was carried out using  Scanning Electron Microscopy(SEM). Results exhibit that UHMWPE had deep grooves as compared to finer grooves on PEEK indicating a low wear rate in the latter. This was also supported by the experimental results suggesting PEEK as a suitable alternative biopolymer for TKR.

The recent advances in manufacturing systems motivate several studies to focus on Economic Production Quantity (EPQ) problem. Althuogh there are several extentions to the EPQ, this paper provides a new extension by considering some of the real world parameters like: (a) shortages in the form of partial backordering, (b) inventory can deteriorate stochastically, (c) machine can break down stochastically, and (d) machine repair time may change stochastically based on the failure status of machine. As far as we know, there is no study treated all these suppositions in an EPQ framework. In addition to this development, two forms of uniformly- and exponentially-distributed repair times are formulated and necessary convexity conditions are discussed. Then, the corresponding optimality conditions are written that lead to finding the roots of two equations. Due to difficulty of achieving a closed-form solution, the solution is obtained numerically by means of Newton-Raphson method. Finally, some sensitivity analyses are provided to explain the models’ applicability. The practicality and efficiency of the proposed method in this context lends weight to development of proposed EPQ with more complex elements and its application more broadly.

In the presented article, the temperature effect was studied on creep properties and fracture behaviors of AlSi12Cu3Ni2MgFe aluminum-silicon alloys, unreinforced and reinforced with SiO2 nano-particles. For such objective, standard specimens were fabricated by gravity casting and stir-casting methods, for aluminum alloys and nano-composites, respectively. Then, force-controlled creep testing was performed on standard specimens at 250, 275 and 300°C, under 100 MPa. Then, to find failure mechanisms, the fracture surface of test samples was also analyzed by the field emission scanning electron microscopy. Experimental results depicted the temperature changed creep behaviors of both materials, effectively. Moreover, a significant improvement in creep properties was observed by reinforcing the aluminum matrix with nano-particles, besides a heat treatment process. Such an increase in the creep lifetime was higher at 300°C. In addition, the fracture surface investigation of both materials implied the same brittle behavior, with quasi-cleavage marks. The failure location changed from inside the intermetallic phase into boundaries of the intermetallic phase in the nano-composite.

One of the major industry problems is the flow boiling, where reaching to the critical heat flux (CHF) condition can lead to a temperature jump and damage of the systems. In the present study, the effects of a uniform change in tube diameter on subcooled flow boiling and CHF was numerically investigated. The Euler-Euler model was used to investigate the relationship between the two liquid and vapor phases. The ANSYS Fluent code was used for simulation. According to the results, a linear increase in the tube diameter leads to increase of vapor volume fraction adjacent to the tube wall, as compared to a regular  tube with a fixed-diameter, which leads to increase of the tube wall temperature due to the low value of the heat transfer coefficient. At CHF conditions, where the tube wall temperature is much higher than that in subcooled flow boiling, an increase in tube diameter may lead to higher tube wall temperature before the temperature jump, as compared to the post-jump temperature of a tube with a constant diameter. The best approach for decreasing the tube wall temperature was found to be a linear decrease in tube diameter. For the tube diameter change angles of θ < - 0.0383°, tube wall temperature exhibited a decreasing trend from the inlet of the tube to its end.

In this study, it was attempted to design a high-performance single-walled carbon nanotube (SWCNT) bundle interconnects in a full adder. For this purpose, the circuit performance was investigated using simulation in HSPICE software and considering the technology of 32-nm. Next, the effects of geometric parameters including the diameter of a nanotube, distance between nanotubes in a bundle, and width and length of the bundle were analyzed on the performance of SWCNT bundle interconnects in a full adder using Taguchi approach (TA). The results of Taguchi sensitivity analysis (TSA) showed that the bundle length is the most effective parameter on the circuit performance (about 51% on the power dissipation and 47% on the propagation delay). Moreover, the distance between nanotubes greatly affects the response compared to other parameters. Also, response surface method (RSM) indicated that an increase in the length of interconnects (L) improves the output of power dissipation. As the width of interconnects (W) and diameter of CNTs (D) increase the power dissipation also increases. Decrease in the distance between CNTs in a bundle (d) leads to an increase in power dissipation. The highest value of power dissipation is achieved if the maximum values for the parameters of length and width of interconnects (L, W), and diameter of CNTs (D) and the minimum value of the distance between CNTs in a bundle (d) are considered. It is also revealed that an increase in the length of interconnects (L) increases the propagation delay. Eventually, the optimum parameters are reported and the performance of the optimized system is compared using different methods (TA and RSM). Results indicate that the difference between the performance of optimal design of SWCNT bundle interconnects in a full adder predicted by different methods is less than 6% which is acceptable according to engineering standards.

Small diesel engines are widely used for commercial vehicle and passenger car applications due to their higher torque requirements, fuel economy, and better thermal efficiency. These engines are exposed to different operating and environmental conditions and hence emissions from these engines are erratic. Strategies are required to enhance performance and reduce engine-out emissions considering environmental pollution and regulations. The main objective of this experimental study is to develop strategies for performance improvement and emission reduction for naturally aspirated engines, which can further be used for emission reduction of the multicylinder engine. Experimental work has been carried out on a single-cylinder naturally aspirated diesel engine to study the impact of engine operating parameters like valve timing, swirl ratio, and injection pressure on engine performance and emissions. Parameters considered for the study are: three intake valve opening timings, two fuel injection pump pressures, two-cylinder head swirls, and three start of injection timings.  Results showed improvement in performance, lower exhaust gas temperature, and reduction of engine-out emission. Exhaust gas temperature was reduced by 5-18% with advanced valve opening and lower cylinder head swirl option. NOx emission was reduced by 5-50% at advanced intake valve opening (IVO) options with retarded start of injection (SOI) and lower swirl cylinder head. This has a penalty on CO and HC emissions since the availability of fresh air is less due to higher internal exhaust gas recirculation (EGR). Higher pressure fuel injection pump helps in improving engine torque with an adverse effect on engine-out NOx emission. As these engines are of low power capacity segment and are used in few countries, research on these engines is limited. All research work has been carried out in the field of intake valve closing timings, swirl ratio and injection timings; however, very limited research is available for the effect of intake valve opening timings due to practical limitations of the lower valve to piston clearance in diesel engines.

Qualification of employees who operate technological processes directly influences the safety of production. However, the employees’’ qualification cannot completely exclude human factor. Today, there are many technologies that can minimize or eliminate human factor impact on production safety ensuring. The augmented reality technology is an example of this technology. Nowadays, the augmented reality technologies and industrial technologies integration process moves to a new level of development. These technologies have huge experience, which has been accumulated in a long period of time. -This new level turns available by this experience combination and integration; it brings additional profit to the enterprise and can be a basis for completely new technologies. This paper shows an example of combination of augmented reality technology and oil pumps maintenance. For researching of efficiency of augmented reality system for oil pump maintenance, the laboratory unit with Grundfos vertical electric centrifugal pump (CR15-4 A-FGJ-AE-HQQE) was used. The laboratory unit is a physical model of one of the continuous oil processes. The oil pump of this laboratory unit is object of this research. The algorithm of servicing of oil pump was developed. The test of system and algorithms were carried out with four groups of people: the first one had only instructions to use on hand, the second one only used the internal recommendations of the system, the third one used only the help of an expert, and the fourth used internal recommendations and, if necessary, contacted the expert. The results show the efficiency and actuality of augmented reality technology for maintenance of industrial equipment, especially for the equipment operated in remote Arctic conditions.

Electric wheelchair is one of the equipment to be used by the incapacitated and disable people. Constant exposure to vibration affects human comfort and health. Reducing the vibrations transmitted to the human body is important in the electric wheelchair design and becomes a healthcare industry demand. This paper deals with the study on vibration control of the electric wheelchair suspension system. A generalized model of the electric wheelchair suspension, including the biodynamic model of seated human body is presented. In order to achieve optimal suspension performance, an active control for wheelchair suspension is designed based on H-infinity control criterion. Numerical simulations are carried out to demonstrate the effectiveness of the proposed wheelchair suspension system. The simulation results show that the proposed control system can effectively attenuate the vibration amplitude and improve the wheelchair suspension performance. This control system could be used for electric wheelchair design and assist with improving human comfort.

Single staggered is a design development of normal wire and tube heat exchanger that wires are welded with staggered configuration on two sides. Capacity of wire and tube heat exchanger is the ability of the heat exchanger to release heat. The objective of this study is to analyse the effect of wire pitch (pw) on capacity of single staggered wire and tube heat exchanger. The research method uses Computational Fluid Dynamic (CFD) simulation by ANSYS Fluent to analyse heat transfer of wire and tube; also to analyse airflow at surface the wire and tube. The simulation is experimentally validated by measuring temperatures at some points of wire and tube. Based on results, temperature contours increasing capacity of heat exchanger depend on smaller wire pitch that the highest value is 72.02 W at pw 7 mm. The reason is smaller wire pitch increases area of convection heat transfer surface. Whereas, airflow patterns show air move slowly at the wire and tube surface and flow with free convection. This study contributes new design of wire and tube heat exchanger with CFD and it can be applied to improve the performance of this heat exchanger in refrigeration system and other applications.

In this work, a simple semi-empirical model is proposed, based on Response Surface Model, RSM, to determine the shape of an attached oblique shock wave emanating from a pointed axisymmetric nose at zero angle of attack. Extensive supersonic visualization images have been compiled from various nose shapes at different Mach numbers, along with some others performed by the author for the present paper. The method is based on the relationship between the body shape and the shock shape. The body shape and the free stream Mach number determine the shape of the oblique shock standing ahead. From the statistical data bank containing the visualization tests and employing the RSM, an analytic relationship has been established between the body and the shock shape. From this relationship, knowing the body shape and the Mach number, one can simply determine the shock shape. The visualization tests performed by the author for some other cases have approved the accuracy of the proposed relationship. However, the approach is restricted to attached shocks emanating from sharp noses at zero angle of attack. Despite the limitations, this relationship can effectively be used in model scale determination for wind tunnel tests to prevent shock reflection from the walls that could lead to erroneous results.

This study presents a combined pneumatic seed-metering device (SMD) that could not only fill, carry, and meter seeds, but also switch quickly between seed-metering and seed-cleaning modes, and clean seeds thoroughly and rapidly. The seed-filling, seed-carrying, and seed-metering modes of the SMD were analyzed based on a theoretical kinematic model. Furthermore, a three-factor, three-level orthogonal test was conducted by using a performance test bench arranged for the SMD as well as Design-Expert software. The combination of parameters that led to the lowest mis-seeding rate (0.59%) was as follows: an air pressure of 2.67 kPa, a slot width of 2.83 mm, and a seed-metering speed of 20 r/min. The optimized scheme that resulted in a relatively low multiple-seeding rate (4.3%) and met other requirements at the same time was as follows: an air pressure of 2.35 kPa, a slot width of 2.78 mm, and a seed-metering speed of 20 r/min. A field test was subsequently performed by using a combined pneumatic plot cotton planter prototype. While the mis-seeding and re-seeding rates obtained from the field test were both somewhat higher than those obtained from the laboratory bench test, they still met precision planting requirements. The field test validated the accuracy of the theoretical analysis and bench test and served as a foundation for future prototype production and popularization.

This paper analyzes the effects of structures and loads on the static bending and free vibration problems of bilayer beams. Based on static mechanical equilibrium and energy equilibrium, the static and dynamic governing equations of bilayer beam are established. It is found that the value of the thickness ratio has a significant effect on the static and dynamic responses of the beam, and the structure factors have their own critical value. When the value of the relative thickness is lower than its critical value or the length thickness ratio is greater than its critical value, the static and dynamic responses of the beam increase obviously. The results reveal that a critical value exists in bilayer beam, the value has noticeable influence on the mechanical properties of bilayer beams. Therefore, investigators should predict the critical structures accurately, when they design the bilayer beam.

The mining chute is an important equipment in the process of coal transportation and coal screening preparation. During the working process, the mining chute will generate a lot of vibration and noise because of constantly friction and impact of gangue and coal blocks. In order to reduce the vibration and noise during the operation of the chute, a new type of foam aluminum laminated structure is used to manufacture the mining chute. According to the characteristic of chute, the laminated structure is optimization designed by taking the vibration amplitude as the objective function, the thickness of the steel plate and the foam aluminum core plate as the design variables. And then, the vibration and noise reduction performance of two type chutes are carried out by using experiment and finite element simulation method. The results show that the using of foam aluminum laminate structure to manufacture the chute can obviously increase the damping ratio of the system, which can effectively reduce the vibration amplitude of the chute. And the average sound insulation performance of foam aluminum laminated chute is better than prototype chute, especially in the middle and high frequency section, which can be reduced by about 7.1 dB on average comparison with prototype chute. So, it can be seen that the foam aluminum laminated structure chute has a more significant sound insulation and vibration reduction effect than the prototype chute.

Physical and geochemical characteristics of shale play conclusive role in confirming operation measures during drilling and stimulation. The properties of shale samples from Jiyang depression were investigated through X-ray diffraction, scanning electron microscope, adsorption isothermal, high pressure mercury intrusion, methylene blue trihydrate, pressure pulse decay, tests of specific water wettability and shale stability index. Correlations, geological and engineering significances of them were discussed. Results show that shale reservoir in Jiyang depression has exploitation value corroborated by good characteristic parameters: 2.86% TOC, 69.9% brittle mineral, 26.14% clay mineral, high permeability of 0.011 × 10-3μm2, large Langmuir volume (5.82 cm3/g) and Langmuir specific area (0.91 m2/g), effective porosity (3.77%) and thickness (130.66m). Langmuir specific area is the key control on methane adsorption and storage verified by its moderate positive relativity with Langmuir volumes rather than TOC. High illite content (69.29%) may lead to instability of borehole and velocity sensitivity damage. Microfractures provide channels for filtration, invasion and loss of drilling fluid. Large specific water wettability (4.36 × 10-7g/m2) and smaller shale stability index (19.99 mm) dispalyed that shale formation were unstable once contacting with fresh water. Countermeasures must be adopted during drilling and fracturing to reduce reservoir damage and complex downhole conditions.

The rheological regulation of the “three high” (high temperature, high density and high salinity) water-based drilling fluid is a worldwide problem due to the combined influence of temperature, solid content and salinity. This paper investigates the factors and regulation methods about rheological property of “three high” water based drilling fluid, and the effects of clay, salinity and weighting materials on the drilling fluid rheology. The experimental results show that base mud compound bentonite with attapulgite had good salt resistance and temperature resistance. The clay content should be kept close to 2% in high density mud (ρ=2.0g/cm3), to control drilling fluid rheology. The sequence of rheological parameters of the “three high” water-based drilling fluid with same density was: manganese oxide> micronized barite> barite> ilmenite powder. When barite compounded with ilmenite powder or micronized barite in the ratio of 1:1 to weight drilling fluid respectively, the rheology and filtration of the “three high” water-based drilling fluid performed well. Based on the optimization of a series of mud additives including fluid loss additive, thinner, anti-collapse filtration reducing agent, lubricant with salt and calcium resistance, a formula of the “three high”water-based drilling fluid system was prepared which had excellent rheology, filtration and sedimentation stability property with the density of 2.2g/cm3 (180℃). The expansion rate of the drilling fluid was 1.84%, shale recovery rate was 85.73%, lubrication coefficient was 0.122, and resistanced to pollution of 1% CaCl2 and 10% poor clay. It also had excellent reservoir protection and plugging performance.