Excellence in Research and Innovation for Humanity

International Science Index

Commenced in January 1999 Frequency: Monthly Edition: International Abstract Count: 39602

Mechanical and Mechatronics Engineering

Development of Al-5%Cu/Si₃N₄, B₄C or BN Composites for Piston Applications
The purpose of this research is to provide a competitive alternative to aluminum silicon alloys used in automotive applications. This alternative was created by developing three types of composites Al-5%Cu- (B₄C, BN or Si₃N₄) particulates with a low coefficient of thermal expansion. Stir casting was used to synthesis composites containing 2, 5 and 7 wt. % of B₄C, Si₃N₄ and 2, 5 of BN followed by squeeze casting. The squeeze casting process decreased the porosity of the final composites. The composites exhibited a fairly uniform particle distribution throughout the matrix alloy. The microstructure and XRD results of the composites suggested a significant reaction occurred at the interface between the particles and alloy. Increasing the aging temperature from 200 to 250°C decreased the hardness values of the matrix and the composites and decreased the time required to reach the peak. Turner model was used to calculate the expected values of thermal expansion coefficient CTE of matrix and its composites. Deviations between calculated and experimental values of CTE were not exceeded 10%. Al-5%Cu-B₄C composites experimentally showed the lowest values of CTE (17-19)·10-6 °С-1 and (19-20) ·10-6 °С-1 in the temperature range 20-100 °С and 20-200 °С respectively.
A First-Principles Investigation of Magnesium-Hydrogen System: From Bulk to Nano
Bulk MgH2 has drawn much attention for the purpose of hydrogen storage because of its high hydrogen storage capacity (~7.7 wt %) as well as low cost and abundant availability. However, its practical usage has been hindered because of its high hydrogen desorption enthalpy (~0.8 eV/H2 molecule), which results in an undesirable desorption temperature of 3000C at 1 bar H2 pressure. To surmount the limitations of bulk MgH2 for the purpose of hydrogen storage, a detailed first-principles density functional theory (DFT) based study on the structure and stability of neutral (Mgm) and positively charged (Mgm+) Mg nanoclusters of different sizes (m = 2, 4, 8 and 12), as well as their interaction with molecular hydrogen (H2), is reported here. It has been found that due to the absence of d-electrons within the Mg atoms, hydrogen remained in molecular form even after its interaction with neutral and charged Mg nanoclusters. Interestingly, the H2 molecules do not enter into the interstitial positions of the nanoclusters. Rather, they remain on the surface by ornamenting these nanoclusters and forming new structures with a gravimetric density higher than 15 wt %. Our observation is that the inclusion of Grimme’s DFT-D3 dispersion correction in this weakly interacting system has a significant effect on binding of the H2 molecules with these nanoclusters. The dispersion corrected interaction energy (IE) values (0.1-0.14 eV/H2 molecule) fall in the right energy window, that is ideal for hydrogen storage. These IE values are further verified by using high-level coupled-cluster calculations with non-iterative triples corrections i.e. CCSD(T), (which has been considered to be a highly accurate quantum chemical method) and thereby confirming the accuracy of our ‘dispersion correction’ incorporated DFT calculations. The significance of the polarization and dispersion energy in binding of the H2 molecules are confirmed by performing energy decomposition analysis (EDA). A total of 16, 24, 32 and 36 H2 molecules can be attached to the neutral and charged nanoclusters of size m = 2, 4, 8 and 12 respectively. Ab-initio molecular dynamics (AIMD) simulation shows that the outermost H2 molecules are desorbed at a rather low temperature viz. 150 K (-1230C) which is expected. However, complete dehydrogenation of these nanoclusters occur at around 1000C. Most importantly, the host nanoclusters remain stable up to ~500 K (2270C). All these results on the adsorption and desorption of molecular hydrogen with neutral and charged Mg nanocluster systems indicate towards the possibility of reducing the dehydrogenation temperature of bulk MgH2 by designing new Mg-based nano materials which will be able to adsorb molecular hydrogen via this weak Mg-H2 interaction, rather than the strong Mg-H bonding. Notwithstanding the fact that in practical applications, these interactions will be further complicated by the effect of substrates as well as interactions with other clusters, the present study has implications on our fundamental understanding to this problem.
Smart Multifunctionalized and Responsive Polymersomes as Targeted and Selective Recognition Systems
Polymersomes are materials which are considered as artificial counterparts of natural vesicles. The nanotechnology of such smart nanovesicles is very useful to enhance the efficiency of many therapeutic and diagnostic drugs. Those compounds show a higher stability, flexibility, and mechanical strength to the membrane compared to natural liposomes. In addition, they can be designed in detail, the permeability of the membrane can be controlled by different stimuli, and the surface can be functionalized with different biological molecules to facilitate monitoring and target. For this purpose, this study demonstrates the formation of multifunctional and pH sensitive polymersomes and their functionalization with different reactive groups or biomolecules inside and outside of polymersomes´ membrane providing by crossing the membrane and docking/undocking processes for biomedical applications. Overall, they are highly versatile and thus present new opportunities for the design of targeted and selective recognition systems, for example, in mimicking cell functions and in synthetic biology.
A Comparative Study of Microstructure, Thermal and Mechanical Properties of A359 Composites Reinforced with SiC, Si3N4 and AlN Particles
A comparative study of the thermal and mechanical behavior of squeezed A359 composites containing 5, 10 and 15 wt.% SiC, (SiC+ Si3N4) and AlN particulates was investigated. Stir followed by squeeze casting techniques are used to produce A359 composites. It was noticed that, A359/AlN composites have high thermal conductivity as compared to A359 alloy and even to A359/SiC or A359/(SiC+Si3N4) composites. Microstructures of the composites have shown homogeneous and even distribution of reinforcements within the matrix. Interfacial reactions between particles and matrix were investigated using X-ray diffraction and energy dispersive X-ray analysis. The presence of particles led not only to increase peak hardness of the composites but also to accelerate the aging kinetics. As compared with A359 matrix alloy, compression test of the composites has exhibited a significant increase in the yield and the ultimate compressive strengths with a relative reduction in the failure strain. Those light weight composites have a high potential to be used for automotive and aerospace applications.
Blockage By Dendritic Ice In Supercooled Encapsulated Water Superficial Roughness
An experimental device was developed to investigate the blockage by dendritic ice in supercooled water encapsulated process inside cylindrical capsules used for cold storage process. The coolant is a water-alcohol mixture (50% vol.), controlled by a constant temperature bath (CTB). Temperatures varying with time are measured inside and outside the capsule. Cylinder with internal diameter and thickness of 45 mm, 1.5 mm and length 170 mm, respectively, the capsules were made in acrylic, PVC (polyvinyl chloride), bronze and aluminium materials. The results indicate that when the supercooling phenomenon appears, the nucleation process varies according to the temperature distribution of the phase change material, PCM and of the coolant temperature. It has been observed that when the supercooling phenomenon appears, and later the nucleation, a blockage by dendritic ice appears. This blockage was classified according to the capsule material and the coolant temperature, showing different types: total blockage and partial blockage (50% and 25%).
Specified Human Motion Recognition and Unknown Hand-Held Object Tracking
This paper aims to integrate human recognition, motion recognition, and object tracking technologies without requiring a pre-training database model for motion recognition or the unknown object itself. Furthermore, it can simultaneously track multiple users and multiple objects. Unlike other existing human motion recognition methods, our approach employs a rule-based condition method to determine if a user hand is approaching or departing an object. It uses a background subtraction method to separate the human and object from the background, and employs behavior features to effectively interpret human object-grabbing actions. With an object’s histogram characteristics, we are able to isolate and track it using back projection. Hence, a moving object trajectory can be recorded and the object itself can be located. This particular technique can be used in a camera surveillance system in a shopping area to perform real-time intelligent surveillance, thus preventing theft. Experimental results verify the validity of the developed surveillance algorithm with an accuracy of 83% for shoplifting detection.
Wayside Diagnosis of Wheelset Faults of Metros Using One-Period Analysis
Condition monitoring of wheelsets of a railway vehicle is cumbersome since multiple sensor allocations on each wheelset is costly, and sensor calibration is maintained over time unless a wayside diagnosis approach is employed. This research is focused on detection of wheelset faults of Prague metro trainset of type 81-71M using vibration sensors which are placed on the foot of the rail with the contribution of a novel one-period analysis. In order to construct a wayside diagnosis database that is special for Prague metro Line A, a wayside passage is selected so that the operation speed is almost constant. Vibration sensor activity for each metro passing is recorded by two accelerometer sensors on both rights and left rail for all day while metros are in routine operation. Wheelset positions are identified by two optical gates so that sample window of each wheelset is clarified according to the rule of one-period analysis; each wheel perimeter is calculated according to their last known exact radius and samples are collected so that they cover one rotation of each wheel. Signal samples of two known faulty wheels (wheel flats) of a wheelset on the ID-108 metro are used as ground truth information in comparison to ID-119 healthy data. Since multiple passing of each metro train set available, constructed database has 16 faulty signal samples against 16 healthy ones for related passes. Three different methodologies; Wavelet Packet Energy (WPE), Time-Domain Features (TDF) and Local Configuration Pattern-Kurtograms (LCP-K) are used in the feature extraction phase. Two state-of-art classifiers; Fisher Linear Discriminant Analysis and Support Vector Machine are employed in the classification of two-class database. Outstanding results are observed among proposed techniques up to 100% (TDF). Proposed methods may be used to maintain an efficient wayside diagnostic system of any type of railway vehicle after further adjustments are performed.
Simulation of Ammonia-Water Two Phase Flow in Bubble Pump
The diffusion-absorption refrigeration cycle consists of a generator bubble pump, an absorber, an evaporator and a condenser, and usually operates with ammonia/water/ hydrogen or helium as working fluid. In the absorption diffusion cycles, the bubble pump is one of the most critical components in the cycle, since it’s responsible for displacing the solution from the generator to the rectifier. The aim of the paper is to study the stability problem in the bubble pump. In fact, instability caused reduction of bubble pump efficiency. For achieved this goal, we are simulated the behaviour of two-phase flow in the bubble pump. We are used for that the drift flow model. Equations of drift flow model are formulated in transitional regime, nonadiabatic condition and thermodynamic equilibrium between liquid and vapour phases. Equations resolution allowed to defined void fraction, liquid and vapour velocities, pressure and mixing enthalpy. We are used ammonia- water as working fluid, where ammonia mass fraction in the inlet is fixed at 0.6. Flow behaviour is simulated for a heated bubble pump tube of 1m of length and 0.6 of inner diameter. Heat flux applied is 2 to 5 kW/m². The results of simulation reveal an oscillation of vapour and liquid velocities along time. Oscillation studies decrease with time and with heat flux. For sufficient time steady state regime is established characterised by constant liquid velocity and void fraction values. However vapour velocities haven’t same behaviour, it increases for steady state regime too. In the other hand pressure drop, oscillation is studied.
A Comparison of Three Methods to Evaluate the Surface Roughness in Machining Process
The machinability of workpieces (AISI 1045 Steel, AA2024 aluminum alloy, A48-class30 gray cast iron) in turning operation has been carried out using different types of cutting tool (conventional, cutting tool with holes in toolholder and cutting tool filled up with composite material) under dry conditions on a turning machine at different stages of spindle speed (630-1000 rpm), feed rate (0.05-0.075 mm/rev), depth of cut (0.05-0.15 mm) and tool overhang (41-65 mm). Experimentation was performed as per Taguchi’s orthogonal array. To evaluate the relative importance of factors affecting surface roughness the single decision tree (SDT), Decision tree forest (DTF) and Group method of data handling (GMDH) were applied.
Finite Element Method Simulations to Study the Effects of Laser Power and Scan Speed on Molten Pool Size in Additive Manufacturing
Additive manufacturing (AM) is increasingly essential in biomedical and aerospace industries. As a recently developed AM technique, Selective Laser Melting (SLM) has been a cost-effective method for various manufacturing processes. However, the molten pool configuration during SLM of metal powders is a crucial issue to the product quality. It is very important to investigate the heat transfer characteristics during the laser heating process. In this work, the finite element methods software (FEM) ANSYS® (workbench module 16.0) was used to predict the unsteady temperature distribution for resolving molten pool dimensions with consideration of temperature-dependent thermal physical properties of TiAl6V4 at different laser powers and scanning speeds. The simulated results of the temperature distributions revealed that the ratio of laser power to scanning speed can critically influence the size of molten pool of titanium alloy powder for SLM development.
Ultrasound-Assisted Nickel Electroplating in Post Supercritical CO2 Mixed Watts Bath
The process of post-supercritical CO2 electroplating uses the electrolyte solution left after being exposed to supercritical CO2 and released to atmospheric pressure. It utilizes the microbubbles that form when oversaturated CO2 in the electrolyte returns to gaseous state and adhere to the surface of the cathode; the adhered surface becomes insulated but after a certain time the accumulated bubbles will depart from the surface, which gives the similar effect of pulsed electroplating. Under atmospheric pressure, the CO2 bubbles will gradually diffuse. Therefore, the introduction of ultrasound can potentially excite the CO2 microbubbles to achieve an electroplated surface of even higher quality. In this study, the post-supercritical electroplating was employed, and an ultrasonic agitator was placed in the electroplating solution to induce vibrations. During the electroplating process, three different modes of agitation: magnetic stirrer agitation, ultrasonic agitation and a combined mode (magnetic + ultrasonic) were applied, respectively. Furthermore, different levels of control power (30 – 50 V) to the ultrasonic agitator were applied, in order to obtain an optimal surface morphology and mechanical properties for the electroplated surface. It is found that the combined agitation mode at a current density of 40 A/dm2 achieved the smallest grain size, a lower surface roughness, and produced an electroplated Ni layer that achieved hardness of 320 Hv, much higher when compared with traditional methods, which were usually in the range of 160 to 300 Hv. However, at the same time, the electroplating with combined agitation developed a higher internal stress of 320 MPa. As the excitation to the microbubbles in the post-supercritical CO2 electroplating solution was provided by a controlled voltage from 30 to 50 V, a more bubble agitation tendency was observed with increasing voltage. When the applied voltage was approaching 50 V, a distribution of nickel debris was found all around the prepared electroplated surface. Thus, there was limited improvement to the surface roughness, and even bigger size grains, the hardness of the electroplated surface was gradually reduced as well. Moreover, the increased number of microbubbles in the electrolyte made some of them easier to be trapped in the surface and increased the internal stress. Therefore, it was demonstrated through this study that the application of ultrasonic vibration in post-supercritical CO2 electroplating solution with adequately controlled ultrasonic power can improve the quality of the electroplating process.
Plasticity in Matrix Dominated Metal-Matrix Composite with One Active Slip Based Dislocation
The main aim of this paper is to suggest one active slip based continuum dislocation approach to matrix dominated MMC plasticity analysis. The approach centered the free energy principles through the continuum behavior of dislocations combined with small strain continuum kinematics. The analytical derivation of this method includes the formulation of one active slip system, the thermodynamic approach of dislocations, determination of free energy, and evolution of dislocations. In addition zero and non-zero energy dissipation analysis of dislocation evolution is also formulated by using varational energy minimization method. In general, this work shows its capability to analyze the plasticity of matrix dominated MMC with inclusions. The proposed method is also found to be capable of handling plasticity of MMC.
Hybrid Quasi-Steady Thermal Lattice Boltzmann Model for Studying the Behavior of Oil in Water Emulsions Used in Machining Tool Cooling and Lubrication
Oil in water (O/W) emulsions are utilized extensively for cooling and lubricating variety of cutting tools during parts machining. A robust Lattice Boltzmann (LBM) thermal-surfactants model, which provides a useful platform for exploring complex emulsions’ characteristics under variety of flow conditions, is used here for the study of the fluid behavior during conventional tools cooling. The transient thermal capabilities of the model, are employed for simulating the effects of the flow conditions of O/W emulsions on the cooling of cutting tools. The model results show that the temperature outcome is slightly affected by reversing the direction of upper plate (workpiece). On the other hand, an important increasing in effective viscosity is seen which supports better lubrication during the work.
Solid Angle Approach to Quantify the Shape of Daughter Cavity in Drying Nano Colloidal Sessile Droplets
Drying of a sessile droplet imbibed with colloidal solution is a complex process in many aspects. Till now, most of the work revolves around; conditions for buckling onset, post-buckling effects, nature of change of droplet shape etc. In this work, we are determining the shape of daughter cavity (DC) formed during post-buckling onset, a less explored stage, and its relationship with experimental parameters. We have introduced solid angle as a special parameter that can quantify the shape of DC at any instant. It facilitates us to compare the shape while experimenting across different substrate types, droplet sizes and particle concentration. Furthermore, the angular location of ‘weak spot’ on the periphery of droplet, which marks the initiation of cavity growth, varies in different conditions. To solve this problem, we have evaluated the deflection angle of weak spots w.r.t. the vertical axis going through the middle of droplet. Subsequently, the solid angle subtended by DC is analyzed about that inclined axis. Finally, results of analysis allude that increasing colloidal concentration has inverse effect on the growth rate of cavity’s shape. Moreover, the cap radius of DC is observed lower for high PLR which makes the capillary pressure higher and thus tougher to expedite cavity formation relatively. This analysis can be helpful in further studies to relate the shape, deflection angle, growth rate of daughter cavity to the type of droplet crust formed in the end. Examining DC stage shall add another layer to nano-colloidal research which aims to influence many industrial applications like patterning, coatings, drug delivery, food processing etc.
Learning Dynamic Representations of Nodes in Temporally Variant Graphs
In many industries, including telecommunications, churn prediction has been a topic of active research. A lot of attention has been drawn on devising the most informative features, and this area of research has gained even more focus with spread of (social) network analytics. The call detail records (CDRs) have been used to construct customer networks and extract potentially useful features. However, to the best of our knowledge, no studies including network features have yet proposed a generic way of representing network information. Instead, ad-hoc and dataset dependent solutions have been suggested. In this work, we build upon a recently presented method (node2vec) to obtain representations for nodes in observed network. The proposed approach is generic and applicable to any network and domain. Unlike node2vec, which assumes a static network, we consider a dynamic and time-evolving network. To account for this, we propose an approach that constructs the feature representation of each node by generating its node2vec representations at different timestamps, concatenating them and finally compressing using an auto-encoder-like method in order to retain reasonably long and informative feature vectors. We test the proposed method on churn prediction task in telco domain. To predict churners at timestamp ts+1, we construct training and testing datasets consisting of feature vectors from time intervals [t1, ts-1] and [t2, ts] respectively, and use traditional supervised classification models like SVM and Logistic Regression. Observed results show the effectiveness of proposed approach as compared to ad-hoc feature selection based approaches and static node2vec.
Design and Finite Element Analysis of Clamp Cylinder for Capacity Augmentation of Injection Moulding Machine
The Injection Moulding is one of the principle methods of conversions of plastics into various end products using a very wide range of plastics materials from commodity plastics to specialty engineering plastics. Injection Moulding Machines are rated as per the tonnage force applied. The work present includes Design & Finite Element Analysis of a structure component of injection moulding machine i.e. clamp cylinder. The work of the project is to upgrade the 1300T clamp cylinder to 1500T clamp cylinder for injection moulding machine. The design of existing clamp cylinder of 1300T is checked. Finite Element analysis is carried out for 1300T clamp cylinder in ANSYS Workbench, and the stress values are compared with acceptance criteria and theoretical calculation. The relation between the clamp cylinder diameter and the tonnage capacity has been derived and verified for 1300T clamp cylinder. The same correlation is used to find out the thickness for 1500T clamp cylinder. The detailed design of 1500T cylinder is carried out based on calculated thickness.
Parametric Study and Modelling of Orthogonal Cutting Process for AISI 4340 and Ti-6Al-4V Alloy
The influence of parameters like velocity and depth of cut on cutting forces is investigated for the empirical relation of the coefficient of friction derived for CRS 1018 for different materials like AISI 4340 and Ti6Al4V. For this purpose, turning tests were carried out on the above materials using coated cemented carbide tool inserts for steel grade and uncoated cemented carbide cutting tool inserts for Titanium with different chip breaker geometries. The cutting forces were measured using a Kistler dynamometer where the multiplication factor taken is 200.The effect of cutting force variation was analyzed experimentally and are compared with the analytical results.
Heat Transfer Dependent Vortex Shedding of Thermo-Viscous Shear-Thinning Fluids
The focal point of this work is the wake flow behind a heated circular cylinder in the laminar vortex shedding regime for thermo-viscous shear thinning fluids. In the case of isothermal flows of Newtonian fluids, the vortex shedding regime is characterized by a distinct Reynolds number and an associated Strouhal number. In the case of thermo-viscous shear thinning fluids, the flow regime can significantly change in dependence of the temperature of the viscous wall of the cylinder. The Reynolds number alters locally and, consequentially, the Strouhal number globally. In the present CFD study, the temperature dependence of the Reynolds and Strouhal Number is investigated for the flow of a Carreau fluid around a heated cylinder. Its temperature dependence of the viscosity has been modelled by the standard Williams-Landel-Ferry (WLF) equation. For the CFD study, the incompressible Finite-Volume solver THETA developed at DLR has been applied. The fluid domain is a rectangle 20 times larger than the cylinder with inflow, outflow and symmetry boundary conditions. At the inflow boundary, a fluid flow with 3.2 m/s has been set. There the temperature has been specified to 405K at which the fluid has a zero viscosity of 100 Pas. Hence the initial Reynolds number of 0.64 with the cylinder diameter of 0.02 m as the reference length. A Newtonian fluid shows no flow separation under this creeping flow conditions. In the present simulation campaign, the fluid parameters and on-flow and thermal boundary conditions have been varied over a certain range in order to derive a relation between dimensionless heat transfer, Reynolds and Strouhal number. Thereto, for each simulation case the temperature of the cylinder wall has increased stepwise from 405 K to 485 K whereas the temperature of the in-flowing fluid has kept constant at 405 K. Together with the shear thinning due to the high shear rates close to the cylinder wall this leads to a significant decrease of viscosity of three orders of magnitude in the nearfield of the cylinder and a reduction of two orders of magnitude in the wake field. Yet the shear thinning effect is able to change the flow topology: a complex Kármán vortex street occurs, also revealing two distinct characteristic frequencies associated with the dominant and sub-dominant vortices. Heating up the cylinder wall leads to a delayed flow separation and narrower wake flow, giving lesser space for the sequence of counter-rotating vortices. This spatial limitation does not only reduce the amplitude of the oscillating wake flow it also shifts the dominant frequency to higher frequencies, and it damps higher harmonics. Eventually, the locally heated wake flow smears out. Eventually, the CFD simulation results of the systematically varied flow and fluid parameter study have been used to formulate a relation for the main characteristic numbers. Additionally for further interpretation a special version of the Nahme number has been derived based on a variation of the standard WLF formulation of the Andrade temperature-viscosity shift factor revealing that viscous heating has less influence than the temperature at the cylinder wall.
Numerical Analysis of a Strainer Using Porous Media Technique
Strainer filter serves to block the inflow of impurities while mixed fluid is entering or exiting the piping. The filter of the strainer has a perforated structure, so that the pressure drop and the velocity change necessarily occur when the mixed fluid passes through the filter. It is possible to predict the pressure drop and velocity change of the strainer by numerical analysis by implementing all the perforated plates. However, if the size of the perforated plate exceeds a certain size, it is difficult to perform the numerical analysis, and sometimes we cannot guarantee its accuracy. In this study, we tried to predict the pressure drop and velocity change by using the porous media technique to obtain the equivalent resistance without actual implementation of the perforation shape of the strainer. Ansys-CFX, a commercial software, is used to perform the numerical analysis. The analysis procedure is as follows. Firstly, the unit pattern of the perforated plate is modeled, and the pressure drop is analyzed by varying the velocity by symmetry of the wall surface. Secondly, since the equation for obtaining resistance is a quadratic equation of pressure having unknown velocity, the viscous resistance and the inertia resistance of the perforated plate are obtained from the relationship between pressure and speed. Thirdly, by using the calculated resistance values, the values are substituted into the flat plate implemented as a two-dimensional porous media, and the accuracy is verified by comparing the pressure drop and the velocity change. Fourthly, the pressure drop and velocity change in the whole strainer are analyzed by using the resistance values obtained on the perforated plate in the actual whole strainer model. Using the porous media technique, it is found that pressure drop and velocity change can be predicted in relatively short time without modeling the overall shape of the filter. Acknowledgements: This work was supported by the Valve Center from the Regional Innovation Center(RIC) Program of Ministry of Trade, Industry & Energy (MOTIE).
Improved Structure and Performance by Shape Change of Foam Monitor
Foam monitors are devices that are installed on cargo tank decks to suppress cargo area fires in oil tankers or hazardous chemical ship cargo ships. In general, the main design parameter of the foam monitor is the distance of the projection through the foam monitor. In this study, the relationship between flow characteristics and projection distance, depending on the shape was examined. Numerical techniques for fluid analysis of foam monitors have been developed for prediction. The flow pattern of the fluid varies depending on the shape of the flow path of the foam monitor, as the flow losses affecting projection distance were calculated through numerical analysis. The basic shape of the foam monitor was an L shape designed by N Company. The modified model increased the length of the flow path and used the S shape model. The calculation result shows that the L shape, which is the basic shape, has a problem that the force is directed to one side and the vibration and noise are generated there. In order to solve the problem, S-shaped model, which is a change model, was used. As a result, the problem is solved, and the projection distance from the nozzle is improved.
Visual Search Based Indoor Localization in Low Light via RGB-D Camera
Most of traditional visual indoor navigation algorithms and methods only consider the localization in an ordinary daytime, while we focus on the indoor re-localization in low light in the paper. As RGB images are degraded in low light, less discriminative infrared and depth image pairs are taken, as the input, by RGB-D cameras, the most similar candidates, as the output, are searched from databases which are built in the bag-of-word framework. The epipolar constraint can be used to compute re-localize the query infrared and depth image sequence. We evaluate our proposed method in two datasets captured by Kinect2. The results demonstrate very promising re-localization results for the indoor navigation system in low light environments.
Application Of The Finite Window Method To A Time-dependent Convection-diffusion Equation
The FWM (Finite Window Method) is a new numerical meshfree technique for solving problems defined either in terms of PDEs (Partial Differential Equation) or by a set of conservation/equilibrium laws. The principle behind the FWM is that in such problem each element of the concerned domain is interacting with its neighbors and will always try to adapt to keep in equilibrium with respect to those neighbors. This leads to a very simple and robust problem solving scheme, well suited for transfer problems. In this work, we have applied the FWM to an unsteady scalar convection-diffusion equation. Despite its simplicity, it is well known that convection-diffusion problems can be challenging to be solved numerically, especially when convection is highly dominant. This has led researchers to set the scalar convection-diffusion equation as a benchmark one used to analyze and derive the required conditions or artifacts needed to numerically solve problems where convection and diffusion occur simultaneously. We have shown here that the standard FWM can be used to solve convection-diffusion equations in a robust manner as no adjustments (Upwinding or Artificial Diffusion addition) were required to obtain good results even for high Peclet numbers and coarse space and time steps. A comparison was performed between the FWM scheme and both a first order implicit Finite Volume Scheme (Upwind scheme) and a third order implicit Finite Volume Scheme (QUICK Scheme). The results of the comparison was that for equal space and time grid spacing, the FWM yields a much better precision than the used Finite Volume schemes, all having similar computational cost and conditioning number.
Automation of Process Waste-Free Air Filtration in Production of Concrete, Reinforced with Basalt Fiber
Industrial companies - one of the major sources of harmful substances to the atmosphere. The main cause of pollution on the concrete plants are cement dust emissions. All the cement silos, pneumatic transport, and ventilation systems equipped with filters, to avoid this. Today, many Russian companies have to decide on replacement morally and physically outdated filters and guided back to the electrostatic filters as usual equipment. The offered way of a cleaning of waste-free filtering of air differs in the fact that a filtering medium of the filter is used in concrete manufacture. Basalt is widespread and pollution-free material. In the course of cleaning, one part of basalt fiber and cement immediately goes to the mixer through flow-control units of initial basalt fiber and cement. Another part of basalt fiber goes to filters for purification of the air used in systems of an air lift, and ventilating emissions passes through them, and with trapped particles also goes to the mixer through flow-control units of the basalt fiber fulfilled in filters. At the same time, regulators are adjusted in such a way that total supply of basalt fiber and cement into the mixer remains invariable and corresponds to a given technological mode.
An Improved Mesh Deformation Method Based on Radial Basis Function
Mesh deformation using radial basis function interpolation method has been demonstrated to produce quality meshes with relatively little computational cost using a concise algorithm. However, it still suffers from the limited deformation ability, especially in large deformation. In this paper, a pre-displacement improvement is proposed to improve the problem that illegal meshes always appear near the moving inner boundaries owing to the large relative displacement of the nodes near inner boundaries. In this improvement, nodes near the inner boundaries are first associated to the near boundary nodes, and a pre-displacement based on the displacements of associated boundary nodes is added to the nodes near boundaries in order to make the displacement closer to the boundary deformation and improve the deformation capability. Several 2D and 3D numerical simulation cases have shown that the pre-displacement improvement for radial basis function (RBF) method significantly improves the mesh quality near inner boundaries and deformation capability, with little computational burden increasement.
A Correlation Analysis-Based Swarm Intelligent Search Algorithm for Robust Identification of Multi-Input Multi-Output Systems with Outliers
In industrial areas, the measurement outputs usually contain small amounts of outliers that can lead to imprecise parameter estimation of system models. In order to solve the problem, this paper proposes a correlation analysis-based swarm intelligent identification algorithm. Firstly, the correlation analysis is employed to get equivalent finite impulse response (FIR) models. Since the growth of number of effective samples lowers the percentage of outliers, the bias caused by outliers can be minimized. However, the unknown-but-bounded errors due to the previous correlation analysis may lead to biased parameter estimation over the finite data windows. Taking advantage of global search capability of particle swarm optimization (PSO) and exactly local optimization of new Luus-Jaakola (NLJ), a PSO-NLJ intelligent algorithm is developed to identify parameters of a multi-input multi-output (MIMO) system. The simulation example shows that the proposed method works well.
Flow Field Analysis of a Liquid Ejector Pump Using Embedded Large Eddy Simulation Methodology
The understanding of entrainment and mixing phenomenon in the ejector pump is of pivotal importance for designing and performance estimation. In this paper, the existence of turbulent vortical structures due to Kelvin-Helmholtz instability at the free surface between the motive and the entrained fluids streams are simulated using Embedded LES methodology. The efficacy of Embedded LES for simulation of complex flow field of ejector pump is evaluated using ANSYS Fluent®. The enhanced mixing and entrainment process due to breaking down of larger eddies into smaller ones as a consequence of Vortex Stretching phenomenon is captured in this study. Moreover, the flow field characteristics of ejector pump like pressure velocity fields and mass flow rates are analyzed and validated against the experimental results.
Modelling of Exothermic Reactions during Carbon Fibre Manufacturing and Coupling to Surrounding Airflow
Carbon fibres are fibrous materials with a carbon atom amount of more than 90%. They combine excellent mechanicals properties with a very low density. Thus carbon fibre reinforced plastics (CFRP) are very often used in lightweight design and construction. The precursor material is usually polyacrylonitrile (PAN) based and wet-spun. During the production of carbon fibre, the precursor has to be stabilized thermally to withstand the high temperatures of up to 1500 °C which occur during carbonization. Even though carbon fibre has been used since the late 1970s in aerospace application, there is still no general method available to find the optimal production parameters and the trial-and-error approach is most often the only resolution. To have a much better insight into the process the chemical reactions during stabilization have to be analyzed particularly. Therefore, a model of the chemical reactions (cyclization, dehydration, and oxidation) based on the research of Dunham and Edie has been developed. With the presented model, it is possible to perform a complete simulation of the fibre undergoing all zones of stabilization. The fiber bundle is modeled as several circular fibers with a layer of air in-between. Two thermal mechanisms are considered to be the most important: the exothermic reactions inside the fiber and the convective heat transfer between the fiber and the air. The exothermic reactions inside the fibers are modeled as a heat source. Differential scanning calorimetry measurements have been performed to estimate the amount of heat of the reactions. To shorten the required time of a simulation, the number of fibers is decreased by similitude theory. Experiments were conducted to validate the simulation results of the fibre temperature during stabilization. The experiments for the validation were conducted on a pilot scale stabilization oven. To measure the fibre bundle temperature, a new measuring method is developed. The comparison of the results shows that the developed simulation model gives good approximations for the temperature profile of the fibre bundle during the stabilization process.
Validity of Local Thermal Non-Equilibrium (LTNE) Condition in a Forced Convective Heat Flow through a Porous Channel Using Lattice Boltzmann Method (LBM)
The present research deals with a validation of the local thermal non-equilibrium condition for a forced convective heat transfer in a channel filled with a saturated porous medium using two criteria. The first one is based on the maximum value of the temperature difference between the solid and fluid phases across the entire channel while the other criteria is based on the average value of the temperature difference between the two phases at each point of the computational domain. The Brinkman-Forchheimer-extended-Darcy model is used to describe the fluid flow. The energy transport is simulated using the two-equation model, which accounts for local thermal non-equilibrium between the fluid and solid phases. A thermal Lattice Boltzmann model using three-distribution-functions has been proposed to simulate fluid flow and temperature fields for both fluid and solid phases. Results are presented and discussed in terms of the criteria profiles as function of the solid-to-fluid thermal conductivity ratio upon varying a number of dimensionless parameters such as the Biot number, Prandtl number, Reynolds number, and the medium’s porosity. It was found that the increase of solid-to-fluid thermal conductivity ratio expands the validity over the local thermal non-equilibrium assumption independently from the dimensionless parameters combinations. Also, the parameters’ ranges for the validity of local thermal equilibrium depend strongly on the selected local thermal non-equilibrium criterion for the same operating conditions.
Integration of Magnetoresistance Sensor in Microfluidic Chip for Magnetic Particles Detection
Application of magnetic particles (MPs) has been applied in biomedical field for many years. There are lots of advantages through this mediator including high biocompatibility and multi-diversified bio-applications. However, current techniques for evaluating the quantity of the magnetic-labeled sample assays are rare. In this paper, a Wheatstone bridge giant magnetoresistance (GMR) sensor integrated with a homemade detecting system was fabricated and used to quantify the concentration of MPs. The homemade detecting system has shown high detecting sensitivity of 10 μg/μl of MPs with optimized parameter vertical magnetic field 100 G, horizontal magnetic field 2 G and flow rate 0.4 ml/min.
Combustion Characteristics of Wet Woody Biomass in a Grate Furnace: Including Measurements within the Bed
Biomass combustion is a growing technique for heat and power production due to the increasing stringent regulations with CO2 emissions. Grate-fired systems have been regarded as a common and popular combustion technology for burning woody biomass. However, some grate furnaces are not well optimized and may emit significant amount of unwanted compounds such as dust, NOx, CO, and unburned gaseous components. The combustion characteristics inside the fuel bed are of practical interest, as they are directly related to the release of volatiles and affect the stability and the efficiency of the fuel bed combustion. Although numerous studies have been presented on the grate firing of biomass, to the author’s knowledge, none of them have conducted a detailed experimental study within the fuel bed. It is difficult to conduct measurements of temperature and gas species inside the burning bed of the fuel in full-scale boilers. Results from such inside bed measurements can also be applied by the numerical experts for modeling the fuel bed combustion. The current work presents an experimental investigation into the combustion behavior of wet woody biomass (53 %) in a 4 MW reciprocating grate boiler, by focusing on the gas species distribution along the height of the fuel bed. The local concentrations of gases (CO, CO2, CH4, NO, and O2) inside the fuel bed were measured through a glass port situated on the side wall of the furnace. The measurements were carried out at five different heights of the fuel bed, by means of a bent stainless steel probe containing a type-k thermocouple. The sample gas extracted from the fuel bed, through the probe, was filtered and dried and then was analyzed using two infrared spectrometers. Temperatures of about 200-1100 °C were measured close to the grate, indicating that char combustion is occurring at the bottom of the fuel bed and propagates upward. The CO and CO2 concentration varied in the range of 15-35 vol % and 3-16 vol %, respectively, and NO concentration varied between 10-140 ppm. The profile of the gas concentrations distribution along the bed height provided a good overview of the combustion sub-processes in the fuel bed.