High duty engineering component life is usually demonstrated through extensive testing and statistical analysis applied to empirical curve-fit equations. Because of this, the extent of the testing required is huge and costly: it must consider the load cycle range and test to high numbers of cycles. Furthermore, this testing must be repeated for every material, method of manufacture, and subsequent post-processing. Additive Manufacturing (AM) for high duty components has brought to the fore the question of the effect of porosity and surface roughness on fatigue life. Because there is relatively little service life experience, it is possible that the testing approach could also fail to represent conservatively the true life of a critical component. The authors propose the development of a fatigue model based on well-established engineering physics principles, by creating computational specimens with modelled surface roughness and porosity, and subjected to cyclic loading using Finite Element Analysis. They show that the combination of roughness features and sub-surface pores leads to an equivalent plastic strain distribution pattern that suggests an emergent physical process. Such a phenomenological understanding of the fatigue failure process should lead to improved life prediction techniques, more cost effective test procedures, and the development of better AM methods.
In this manuscript, a two-port semi-circular patch antenna with Koch curve fractals is presented as a suitable candidate for portable UWB communication systems. The proposed fractal array is engraved on a 1.57 mm thick FR-4 substrate with an overall array size of 30.5 × 47 × 1.64 mm3. The upper substrate layer consists of two microstrip-line fed semi-circular patches combined with two Koch curve fractals (optimized up to 2nd order of iteration) separated by a distance of λ/2. To mitigate the effect of mutual coupling between the radiating elements, the lower substrate layer consists of a reduced ground plane with a funnel-shaped decoupling structure. To achieve a high degree of isolation (S21/S12 ≤ -16.8 dB) between the ports of the proposed array, two rectangular and L-shaped slots (mirror images of each other) are etched from the upper surface of the reduced ground. The design and simulation of the proposed antenna array is implemented in CST MWS’18. The optimized fractal array covers the simulated frequency band from 4.395-10.184 GHz with a fractional bandwidth of 79.4 % (at a center frequency of 5.789 GHz) and provides a peak radiation efficiency of 88.8% (at 6.2 GHz frequency). The antenna diversity performance is analyzed in terms of envelope correlation coefficient (ECC ≤ 0.0021), diversity gain (DG ≥ 9.989), mean effective gain (MEG ≥ -3.7 dB), channel capacity loss (CCL ≤ 0.4 bits/s/Hz) and total active reflection coefficient (TARC ≤ -10 dB). The experimentally measured S-parameter results show a good match with the simulated ones.
The synthetic rubber industry is of great importance and it is present in the daily life of world society. BR (butadiene rubber or polybutadiene) is one of the most used polymers in this field, mainly in tire production. Therefore, the control of operational conditions and final properties of the polymer formed are important points to be studied as they are a challenge for the industry. Thus, the present work focus in simulate the batch polymerization of polybutadiene using the Aspen Plus software, where 1,3-butadiene, titanium tetrachloride, triethylaluminium and hexane were used as monomer, catalyst, co-catalyst and solvent, respectively. Four cases were simulated changing the number of catalyst sites in order to predict and compare the final properties of polybutadiene resins including the average molecular weights, the molecular weight distribution and the evolution of operation conditions that are used at plant to monitor the course of the reaction like the reaction temperature and pressure.
Recently, nanostructure perovskite oxides such as LaMO3 (M=Co, Ni, Fe, …) received attention in academic researches due to its catalytic properties. In this research, the LaCoO3 perovskite nanoparticles have been synthesized by single-step route via the sol-gel auto-combustion method. The precursors used in this method were lanthanum nitrate and cobalt nitrate, as metals sources dissolved in distilled water and also using PVP as a surfactant, Urea and glycine as an oxidizer. The sol formed at stirring stage at 60 °C continued by gelation through the water evaporation at 90 °C and then auto-combustion occurred. Product of combustion step was washed and centrifuged three times and later calcined at 600 °C for 2 h. As synthesized nanoparticles are characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and particle size analyzer (PSA). The characterization results proved the synthesis of nanoparticles below 100 nm with perovskite structure in narrow size distribution by using this method. The purity and size of nanoparticles vary depending on the fuel and fuel to oxidizer ratio.
Reduction in the torsional vibration of heavy rotors like turbo-generator rotor is important for the safe and efficient functioning of the power plant. In this paper theoretical study is performed to control the torsional vibration in the turbo-generator rotor using piezoelectric material as sensor and actuator. Polyvinylidene fluoride (PVDF) layer is used as sensor and actuator. Proportional and velocity feedback is used as control law. The variation in the electromagnetic torque of synchronous generator during various electrical faults is evaluated using dq0 model. Finite element method is used to model the rotor elements. The coupled equations are solved in MATLAB using Newmark-beta integration method. The coupling elements of turbine and generator are most susceptible to the shear failure so torsional vibration of coupled rotor on coupling elements are compare for controlled and uncontrolled scenario. Simulation results show that for actively controlled rotor significant reduction in the amplitude of torsional vibrations is observed.
The paper presents a novel technique to detect the solvents in water like sugar, salt, and its combination using a wideband CPW fed microstrip antenna with periodic EBG ground structure. The antenna is designed and fabricated to operates at the bandwidth of 3 GHz with a stable gain of 9 dBi maintaining VSWR<2. The uniquely designed antenna works as a sensor in its near field to sense the solvents in water in terms of resonant frequency and reflection method in wider bandwidth. The technique also detects the changes in the temperature of the soft drinks as a function of reflection characteristics. This technique will be useful for finding the percentage of solvents in soft drinks before consumption. The sensing technique is without physical contact with the solution and chemical process. Therefore it is a healthy way to find the ingredients in solutions like soft drinks. The technique will be useful to the food regulation boards to limit the contents of beverages and cold drinks.
As digitilisation is being applied in redefining products and business models world-wide, evidence abound in the construction industry as a sector that is slow to its adoption. While digitilisation tools have been applied in modifying processes/procedures in the global North; a larger percentage of the sector in the global South is yet to be disrupted. For indigenous firms to join the rapid transformation wheel, this study reviews the interrelationship between digitilisation and building information modeling. The study objectives are to examine the prevalence of cultural and strategic capability, evaluate the relationship between cultural orientation and strategic capability as well as predict a model of building information adoption from culture and strategy. The study population was drawn from the list of construction firms registered with the Lagos State Tender board, list of registered construction firms from the Institute and specific listed firms on the internet. Factor Analysis, Correlation and Regression were the adopted statistical tools. The results revealed production; task and goal attainment; information/communication technology; workforce; innovation, learning and knowledge management as well as conflict and dispute resolution as the prevalent cultural orientations. The availability of resources to communicate, interact and collaborate digitally and leadership capability to organise and coordinate digitally are the top two strategic capabilities. Consequently, 3 out of every 5 firms have moderate awareness on BIM implementation. It was concluded that the level of agreement on the adoption of the culture and the strategy did not reflect on the level of BIM adoption model. Since the results revealed that the existing orientation and strategy contribute about a tenth of BIM adoption model; the firms’ leadership need cultural re-orientation from the client angle and from business environment. On strategy, the firms need support from institutions/government on policies that will cushion the effect of the provision of resources for transformation.
Aerospace components and its coatings are required to possess excellent surface properties namely: fatigue, wear and corrosion resistance over a wide temperature range. Stainless steels, titanium, nickel superalloy and more recently high entropy alloys have been used to improve the exterior properties of these components. In this study, AlCoCrFeNiCu and AlTiCrFeCoNi High Entropy Alloys were successfully fabricated using laser additive manufacturing to produce coatings on a mild steel base plate. The influence of the laser parameters (laser power and scan speed) on the microstructure, hardness and coat geometry (height, width and depth) were also investigated. The results revealed that coatings homogeneously adhered to substrate. The optimum processing parameters for both alloys with defect free structures at a preheat temperature of 400 °C, were at 1200-1600 W at 8-12 mm/s with the layers composed of both FCC and BCC phases. The laser parameters affected the geometry, quality and hardness. The results showed that optimizing the laser parameters achieved by preheating temperature invariably improved the performance of the alloys with potential coatings and aerospace structural applications.
The ambitious Algerian program for diversification of electric energy sources is targeting 22 000 MWe from the renewable energy to the horizon of 2030. This study is a thermo-economic assessment of an integrated solar combined cycle system installed in the Saharan region, which during the nights or cloudy days works as a conventional combined cycle and does not need storage or back-up systems. The obtained results show, in one side that the solar electricity ratio may reach about 17 % and the global thermal efficiency up to 63 %, leading to lower fuel consumption and carbon emission. In the other side, the economic assessment depicts that the levelized cost of energy may reach a value of 0.0222 $/kWh which is about 28 % higher than CC plants. By considering the environment this latter is even more and may reach about 0.0272 $/kWh, but the annual solar contribution, relatively to that installation site, allows about 18.45 million $ of fuel saving and avoidance of 0.89 million ton of CO2 emission over 30 years of operation. operation.
Simulated microgravity (s-µg) devices provide unique conditions for elucidating the effects of gravitational unloading on biological processes. However, s-µg devices are being increasingly applied for mechanobiology studies without proper characterization of the mechanical environment generated by these systems, which confounds results and limits their interpretation. Furthermore, the cell culture methodology central to s-µg approaches introduces new conditions that can fundamentally affect results, but these are currently not addressed. It is essential to understand the complete culture environment and how constituent conditions can individually and synergistically affect cellular responses in order to interpret results correctly, otherwise outcomes may be misattributed to the effects of microgravity alone. For the benefit of the growing space biology community, this article critically reviews a typical s-µg cell culture environment in terms of three key conditions: fluid-mediated mechanical stimuli, oxygen tension and biochemical (cell signalling). Their implications for biological analysis are categorically discussed. A new set of controls is proposed to properly evaluate the respective effects of s-µg culture conditions, along with a reporting matrix and potential strategies for addressing the current limitations of simulated microgravity devices as a platform for mechanobiology.
A review of investigations on the effect of drag-reducing agents in curved pipe flows is presented in this work. Proposed mechanisms of drag reduction, as well as factors that influence their effectiveness also received attention. In addition, this review outlined proposed friction factor and fluid flux models for flow of drag-reducing agents in curved pipes. It was shown in this report that significant drag reduction in curved pipes can be achieved using drag-reducing agents. Drag reduction by additives in curved pipes are generally lower than the corresponding drag reduction in straight pipes. It decreases with increase in curvature ratio and is more pronounced in the transition and turbulent flow regimes. Drag reduction depends strongly on the concentration of polymers and surfactants as well as the bubble fraction of micro-bubbles. It is also reported that drag reduction in curved pipes depends on other factors such as temperature and presence of dissolved salts. Maximum drag reduction asymptote differed between straight and curved pipes and between polymer and surfactant. Due to the limited studies in the area of drag reduction for gas-liquid flow in curved pipes no definite conclusion could be drawn on the effect of drag-reducing agents on such flows. A number of questions remain such as the mechanism of drag reduction in curved pipes and how drag-reducing agents interact with secondary flows. Hence, some research gaps have been identified with recommendations for areas of future researches.
For two processes of large importance, catalysis and biocatalysis, were reported zones without reactants, so called dead zone (DZ). They results from diffusional transport limitations, when apparent reaction order is between (-1..1). Formation of DZ reduces effectiveness of catalyst and influence packed bed reactor productivity. For simple reaction kinetic model, a DZ width inside a pellet can be calculated analytically solving appropriate differential mass balance model. However, generally the analytical solution is unknown and only with using numerical method the position of DZ can be established. The problem with DZ appearance belongs to problems with moving boundaries. Its solution requires application of special numerical procedure and relatively long CPU time. In this work it was proposed a simple, very fast numerical method for calculation of DZ position inside pellet. The method proposed combined with orthogonal collocation on finite elements can be applied for analysis of work of packed bed reactor.
Applications of transfer function to derivation of a high precision model of tracer flow in a commercial measurement system is presented. A transfer function concept makes easier development of models of complex systems and consequently allows for obtaining a model that matches in the best way a physical system. The method has an additional profit viz. the same numerical algorithm i.e. inverse Laplace transform can be employed to solve the model both on the stage of precise model development (boundary value problem) and to find real model parameters (inverse boundary value problem). As a result of concept application, a very precise model of commercial measurement instrument was developed and, next, it was employed to determination of axial dispersion coefficients for empty tube and packed bed. Presented method is precise in wide range of operating conditions and faster comparing to other methods previously described in literature. The paper shows that mathematical modelling can be exploited to enhance measurements for a commercial measurement instrument i.e unlock the full potential of the commercial measurement system with no equipment design changes. The method is also a fast alternative to computational fluid dynamics for high precision calculations.
The demand for electricity is increasing all over the world. In Bangladesh, there are many rural areas where the grid connection has not reached yet. In this paper, a performance evaluation was done with a solar-wind hybrid renewable energy system with diesel backup for a school located in a remote area, Baje Fulchari village in Gaibandha district, Bangladesh. For the proposed site, the load demand was considered 10.468 kWh/day for a normal working day (taken from a field survey) having peak demand of 3.3 kW. HOMER software was used for the simulation. The solar radiation and wind speed data were collected from NASA Surface meteorology and Solar Energy database. The NPC for the most economical system configuration is found USD 6,191 with a COE of 0.125 $/ kWh. Compared to the conventional power plants the proposed system can reduce the COE and GHG emission of about 29.85% and 69% respectively. The system evaluated in this work might be implemented in a school or any other location of similar load profile anywhere in the world having the same geographical and meteorological conditions.
Two filters using Defected Ground Structures have been proposed. First, a multiple frequency band stop filter utilizing a semi-H defect in the ground plane is presented. This structure is then prototyped on a Rogers 4350B substrate of overall size 45 mm $\times$ 15 mm, and external SMD capacitors have been employed to control the resonance of the circuit, for the stopband frequencies of 433 MHz, 700 MHz and 915 MHz. An equivalent circuit is also proposed for this multi-band design. The second filter is a combination of a band-stop and band-pass filter in one structure. The filter, operating with a controllable passband and stopband frequency is fabricated, on Rogers 4350B lossy substrate, to validate the EM and circuit simulation results. Two SMD capacitors have been loaded in the filter to control the pass band and stop band frequencies of the filter with a structure size of 20 mm x 20 mm. Furthermore, a novel equivalent circuit model encompassing the band-pass and band-stop frequency response of the DGS based filter is proposed.
In this paper, a novel beam steerable 2.4 GHz MIMO antenna array is proposed based on the Yagi-Uda principle. The antenna consists of two co-axially excited patch radiators with modified ground plane. A conducting strip with an integrated PIN diode is optimally placed between the patch radiators to act as a director or a reflector to steer the main beam by an angle of +/- 60◦. For all switching modes, the MIMO antenna demonstrates an average gain and efficiency of 5 dB and 92%, respectively, at the resonance frequency of 2.4 GHz. Reduced envelope correlation coefficient in one switching mode exhibited 17 dB improvement in mutual isolation. The simulated results agreed well with measured data. This simple, low-cost, efficient, and mutually isolated antenna array can be very useful in MIMO WLAN applications.
In the biopharmaceutical industry, Raman spectroscopy is now a proven PAT tool that enables in-line simultaneous monitoring of several CPPs and CQAs in real-time. However, as Raman monitoring requires multivariate modeling, variabilities unknown by models can impact the monitoring prediction accuracy. With the widespread use of Raman PAT tools, it is necessary to fix instrumental variability impacts, encountered for instance during a device replacement. In this work, we investigated the impact of instrumental variability between probes inside a multi-channel analyzer and between two analyzers, and explored solutions to correct them on model prediction errors in cell cultures. We found that the Kennard Stone Piecewise Direct Standardization (KS PDS) method enables to lower model prediction errors and that only one batch with the unknown device in the calibration dataset was sufficient to correct the prediction gap induced by instrumental variability. As a matter of fact, during device replacement a first cell culture monitoring can be performed with the KS PDS method. Then, the new data obtained can be inserted in the calibration dataset to integrate instrumental variability in the chemometric model. This methodology provides good multivariate calibration model prediction errors throughout the instrumental changes.
We present a numerical method for simulating 2D flow through a channel with deformable walls. The fluid is assumed to be incompressible and viscous. We consider the highly viscous regime, where fluid dynamics are described by the Stokes equations, and the less viscous regime described by the Navier-Stokes equations. The model is formulated as an immersed boundary problem, with the channel defined by compliant walls that are immersed in a larger computational fluid domain. The channel traverses through the computational domain, and the walls do not form a closed region. When the walls deviate from their equilibrium position, they exert singular forces on the underlying fluid. We compute the numerical solution to the model equations using the immersed interface method, which preserves sharp jumps in the solution and its derivatives. The immersed interface method typically requires a closed immersed interface, a condition that is not met by the present configuration. Thus, a contribution of the present work is the extension of the immersed interface method to immersed boundary problems with open interfaces. Numerical results indicate that this new method converges with second-order accuracy in both space and time, and can sharply capture discontinuities in the fluid solution.