Royal Society Open Science Engineering
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Royal Society Open Science RSS feed -- recent Engineering articles2054-5703Royal Society Open Science<![CDATA[Characterization and Pb(II) removal potential of corn straw- and municipal sludge-derived biochars]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/9/170402?rss=1
Corn straw- and municipal sludge-derived biochars (CS-BC and MS-BC, respectively) were used to remove Pb(II) from aqueous solutions. Despite being pyrolysed at the same temperature (723 K), MS-BC showed higher porosity and hydrophobicity than CS-BC. The optimum biochar loading and pH values allowing efficient Pb(II) removal (greater than 80%) were 0.2 g l^{–1} and 7.0, respectively. The presence of PO_{4}^{3–} (greater than 0.01 mol l^{–1}) significantly affected the adsorptive performance of Pb(II) on the biochar samples. The adsorption data fitted well to a pseudo-second-order kinetic model and a Langmuir model, and the maximum Pb(II) adsorption capacities were 352 and 387 mg g^{–1} for CS-BC and MS-BC, respectively. The main mechanisms involved in the adsorption of Pb(II) on biochar were electrostatic attraction and surface complexation. When comparing both biochars, CS-BC showed better cost-effectiveness for the removal of Pb(II) from aqueous solutions.
]]>2017-09-20T00:10:02-07:00info:doi/10.1098/rsos.170402hwp:master-id:royopensci;rsos.1704022017-09-20Engineering49170402170402<![CDATA[Adaptive recursive algorithm for optimal weighted suprathreshold stochastic resonance]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/9/160889?rss=1
Suprathreshold stochastic resonance (SSR) is a distinct form of stochastic resonance, which occurs in multilevel parallel threshold arrays with no requirements on signal strength. In the generic SSR model, an optimal weighted decoding scheme shows its superiority in minimizing the mean square error (MSE). In this study, we extend the proposed optimal weighted decoding scheme to more general input characteristics by combining a Kalman filter and a least mean square (LMS) recursive algorithm, wherein the weighted coefficients can be adaptively adjusted so as to minimize the MSE without complete knowledge of input statistics. We demonstrate that the optimal weighted decoding scheme based on the Kalman–LMS recursive algorithm is able to robustly decode the outputs from the system in which SSR is observed, even for complex situations where the signal and noise vary over time.
]]>2017-09-13T00:09:19-07:00info:doi/10.1098/rsos.160889hwp:master-id:royopensci;rsos.1608892017-09-13Engineering49160889160889<![CDATA[Performance improvement of miniaturized ZnO nanowire accelerometer fabricated by refresh hydrothermal synthesis]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/9/170557?rss=1
Miniaturized accelerometers are necessary for evaluating the performance of small devices, such as haptics, robotics and simulators. In this study, we fabricated miniaturized accelerometers using well-aligned ZnO nanowires. The layer of ZnO nanowires is used for active piezoelectric layer of the accelerometer, and copper was chosen as a head mass. Seedless and refresh hydrothermal synthesis methods were conducted to grow ZnO nanowires on the copper substrate and the effect of ZnO nanowire length on the accelerometer performance was investigated. The refresh hydrothermal synthesis exhibits longer ZnO nanowires, 12 µm, than the seedless hydrothermal synthesis, 6 µm. Performance of the fabricated accelerometers was verified by comparing with a commercial accelerometer. The sensitivity of the fabricated accelerometer by the refresh hydrothermal synthesis is shown to be 37.7 pA g^{–1}, which is about 30 times larger than the previous result.
]]>2017-09-13T00:09:19-07:00info:doi/10.1098/rsos.170557hwp:master-id:royopensci;rsos.1705572017-09-13Engineering49170557170557<![CDATA[Influence of solvents in the preparation of cobalt sulfide for supercapacitors]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/9/170427?rss=1
In this study, cobalt sulfide (CoS) electrodes are synthesized using various solvents such as water, ethanol and a combination of the two via a facile chemical bath deposition method on Ni foam. The crystalline nature, chemical states and surface morphology of the prepared CoS nanoparticles are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transition electron microscopy. The electrochemical properties of CoS electrodes are also evaluated using cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. When used as an electrode for a supercapacitor, CoS prepared with ethanol as a solvent exhibits a capacitance of 41.36 F g^{–1} at 1.5 A g^{–1}, which is significantly better than that prepared using water and water/ethanol-based solvents (31.66 and 18.94 F g^{–1} at 1.5 A g^{–1}, respectively). This superior capacitance is attributed to the ideal surface morphology of the solvent, which allows for easy diffusion of electrolyte ions into the inner region of the electrode. High electrical conduction enables a high rate capability. These results suggest that CoS nanoparticles are highly promising for energy storage applications as well as photocatalysis, electrocatalysis, water splitting and solar cells, among others. These results show that CoS is a promising positive electrode material for practical supercapacitors.
]]>2017-09-06T00:09:21-07:00info:doi/10.1098/rsos.170427hwp:master-id:royopensci;rsos.1704272017-09-06Engineering49170427170427<![CDATA[Investigating the impact of feedback update interval on the efficacy of restorative brain-computer interfaces]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/8/170660?rss=1
Restorative brain–computer interfaces (BCIs) have been proposed to enhance stroke rehabilitation. Restorative BCIs are able to close the sensorimotor loop by rewarding motor imagery (MI) with sensory feedback. Despite the promising results from early studies, reaching clinically significant outcomes in a timely fashion is yet to be achieved. This lack of efficacy may be due to suboptimal feedback provision. To the best of our knowledge, the optimal feedback update interval (FUI) during MI remains unexplored. There is evidence that sensory feedback disinhibits the motor cortex. Thus, in this study, we explore how shorter than usual FUIs affect behavioural and neurophysiological measures following BCI training for stroke patients using a single-case proof-of-principle study design. The action research arm test was used as the primary behavioural measure and showed a clinically significant increase (36%) over the course of training. The neurophysiological measures including motor evoked potentials and maximum voluntary contraction showed distinctive changes in early and late phases of BCI training. Thus, this preliminary study may pave the way for running larger studies to further investigate the effect of FUI magnitude on the efficacy of restorative BCIs. It may also elucidate the role of early and late phases of motor learning along the course of BCI training.
]]>2017-08-30T00:09:44-07:00info:doi/10.1098/rsos.170660hwp:master-id:royopensci;rsos.1706602017-08-30Engineering48170660170660<![CDATA[Non-contact incipient fault diagnosis method of fixed-axis gearbox based on CEEMDAN]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/8/170616?rss=1
Gearbox plays most essential role in the modern machinery for transmitting the required torque along with motion and contributes to wide range of applications. Any failure in gearbox components affects the productivity and efficiency of the system. Most machine breakdowns related to gears are a result of improper operating conditions and loading, hence lead to failure of the whole mechanism. Ensemble Empirical Mode Decomposition (EEMD) comprises advancement and valuable addition in Empirical Mode Decomposition (EMD) and has been widely used in fault detection of rotating machines. However, intrinsic mode functions (IMFs) produced by EEMD often carry the residual noise. Also, the produced IMFs are different in number due to addition of white Gaussian noise, which leads to final averaging problem. To alleviate these drawbacks, Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) was previously presented. This paper describes and presents the implementation of CEEMDAN for fault diagnosis of simulated local defects using sound signals in a fixed-axis gearbox. Statistical parameters are extracted from decomposed sound signals for different simulated faults. Results show the effectiveness of CEEMDAN over EEMD in order to obtain more accurate IMFs and fault severity.
]]>2017-08-23T00:09:45-07:00info:doi/10.1098/rsos.170616hwp:master-id:royopensci;rsos.1706162017-08-23Engineering48170616170616<![CDATA[Annulus fibrosus functional extrafibrillar and fibrous mechanical behaviour: experimental and computational characterisation]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/8/170807?rss=1
The development of current surgical treatments for intervertebral disc damage could benefit from virtual environment accounting for population variations. For such models to be reliable, a relevant description of the mechanical properties of the different tissues and their role in the functional mechanics of the disc is of major importance. The aims of this work were first to assess the physiological hoop strain in the annulus fibrosus in fresh conditions (n = 5) in order to extract a functional behaviour of the extrafibrillar matrix; then to reverse-engineer the annulus fibrosus fibrillar behaviour (n = 6). This was achieved by performing both direct and global controlled calibration of material parameters, accounting for the whole process of experimental design and in silico model methodology. Direct-controlled models are specimen-specific models representing controlled experimental conditions that can be replicated and directly comparing measurements. Validation was performed on another six specimens and a sensitivity study was performed. Hoop strains were measured as 17 ± 3% after 10 min relaxation and 21 ± 4% after 20–25 min relaxation, with no significant difference between the two measurements. The extrafibrillar matrix functional moduli were measured as 1.5 ± 0.7 MPa. Fibre-related material parameters showed large variability, with a variance above 0.28. Direct-controlled calibration and validation provides confidence that the model development methodology can capture the measurable variation within the population of tested specimens.
]]>2017-08-23T00:09:45-07:00info:doi/10.1098/rsos.170807hwp:master-id:royopensci;rsos.1708072017-08-23Engineering48170807170807<![CDATA[Object recognition and localization from 3D point clouds by maximum-likelihood estimation]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/8/160693?rss=1
We present an algorithm based on maximum-likelihood analysis for the automated recognition of objects, and estimation of their pose, from 3D point clouds. Surfaces segmented from depth images are used as the features, unlike ‘interest point’-based algorithms which normally discard such data. Compared to the 6D Hough transform, it has negligible memory requirements, and is computationally efficient compared to iterative closest point algorithms. The same method is applicable to both the initial recognition/pose estimation problem as well as subsequent pose refinement through appropriate choice of the dispersion of the probability density functions. This single unified approach therefore avoids the usual requirement for different algorithms for these two tasks. In addition to the theoretical description, a simple 2 degrees of freedom (d.f.) example is given, followed by a full 6 d.f. analysis of 3D point cloud data from a cluttered scene acquired by a projected fringe-based scanner, which demonstrated an RMS alignment error as low as 0.3 mm.
]]>2017-08-16T00:08:56-07:00info:doi/10.1098/rsos.160693hwp:master-id:royopensci;rsos.1606932017-08-16Engineering48160693160693<![CDATA[A generalized solution procedure for in-plane free vibration of rectangular plates and annular sectorial plates]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/8/170484?rss=1
A generalized solution procedure is developed for in-plane free vibration of rectangular and annular sectorial plates with general boundary conditions. For the annular sectorial plate, the introduction of a logarithmic radial variable simplifies the basic theory and the expression of the total energy. The coordinates, geometric parameters and potential energy for the two different shapes are organized in a unified framework such that a generalized solving procedure becomes feasible. By using the improved Fourier–Ritz approach, the admissible functions are formulated in trigonometric form, which allows the explicit assembly of global mass and stiffness matrices for both rectangular and annular sectorial plates, thereby making the method computationally effective, especially when analysing annular sectorial plates. Moreover, the improved Fourier expansion eliminates the potential discontinuity of the original normal and tangential displacement functions and their derivatives in the entire domain, and accelerates the convergence. The generalized Fourier–Ritz approach for both shapes has the characteristics of generality, accuracy and efficiency. These features are demonstrated via a few numerical examples.
]]>2017-08-16T00:08:56-07:00info:doi/10.1098/rsos.170484hwp:master-id:royopensci;rsos.1704842017-08-16Engineering48170484170484<![CDATA[Biophysical properties of the human finger for touch comprehension: influences of ageing and gender]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/8/170321?rss=1
The human finger plays an extremely important role in tactile perception, but little is known about how age and gender affect its biophysical properties and their role in tactile perception. We combined studies on contact characteristics, mechanical properties and surface topography to understand age and gender effects on the human finger. The values obtained regarding contact characteristics (i.e. adhesive force) were significantly higher for women than for men. As for mechanical properties (i.e. Young's modulus E), a significant and positive correlation with age was observed and found to be higher for women. A positive correlation was observed between age and the arithmetic mean of surface roughness for men. However, an inverse age effect was highlighted for women. The age and gender effects obtained have never been reported previously in the literature. These results open new perspectives for understanding the weakening of tactile perception across ages and how it differs between men and women.
]]>2017-08-09T00:08:48-07:00info:doi/10.1098/rsos.170321hwp:master-id:royopensci;rsos.1703212017-08-09Engineering48170321170321<![CDATA[The effects of geometric uncertainties on computational modelling of knee biomechanics]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/8/170670?rss=1
The geometry of the articular components of the knee is an important factor in predicting joint mechanics in computational models. There are a number of uncertainties in the definition of the geometry of cartilage and meniscus, and evaluating the effects of these uncertainties is fundamental to understanding the level of reliability of the models. In this study, the sensitivity of knee mechanics to geometric uncertainties was investigated by comparing polynomial-based and image-based knee models and varying the size of meniscus. The results suggested that the geometric uncertainties in cartilage and meniscus resulting from the resolution of MRI and the accuracy of segmentation caused considerable effects on the predicted knee mechanics. Moreover, even if the mathematical geometric descriptors can be very close to the imaged-based articular surfaces, the detailed contact pressure distribution produced by the mathematical geometric descriptors was not the same as that of the image-based model. However, the trends predicted by the models based on mathematical geometric descriptors were similar to those of the imaged-based models.
]]>2017-08-09T00:08:48-07:00info:doi/10.1098/rsos.170670hwp:master-id:royopensci;rsos.1706702017-08-09Engineering48170670170670<![CDATA[Building information modelling review with potential applications in tunnel engineering of China]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/8/170174?rss=1
Building information modelling (BIM) can be applied to tunnel engineering to address a number of problems, including complex structure, extensive design, long construction cycle and increased security risks. To promote the development of tunnel engineering in China, this paper combines actual cases, including the Xingu mountain tunnel and the Shigu Mountain tunnel, to systematically analyse BIM applications in tunnel engineering in China. The results indicate that BIM technology in tunnel engineering is currently mainly applied during the design stage rather than during construction and operation stages. The application of BIM technology in tunnel engineering covers many problems, such as a lack of standards, incompatibility of different software, disorganized management, complex combination with GIS (Geographic Information System), low utilization rate and poor awareness. In this study, through summary of related research results and engineering cases, suggestions are introduced and an outlook for the BIM application in tunnel engineering in China is presented, which provides guidance for design optimization, construction standards and later operation maintenance.
]]>2017-08-02T00:08:27-07:00info:doi/10.1098/rsos.170174hwp:master-id:royopensci;rsos.1701742017-08-02Engineering48170174170174<![CDATA[Waterjet and laser etching: the nonlinear inverse problem]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/7/161031?rss=1
In waterjet and laser milling, material is removed from a solid surface in a succession of layers to create a new shape, in a depth-controlled manner. The inverse problem consists of defining the control parameters, in particular, the two-dimensional beam path, to arrive at a prescribed freeform surface. Waterjet milling (WJM) and pulsed laser ablation (PLA) are studied in this paper, since a generic nonlinear material removal model is appropriate for both of these processes. The inverse problem is usually solved for this kind of process by simply controlling dwell time in proportion to the required depth of milling at a sequence of pixels on the surface. However, this approach is only valid when shallow surfaces are etched, since it does not take into account either the footprint of the beam or its overlapping on successive passes. A discrete adjoint algorithm is proposed in this paper to improve the solution. Nonlinear effects and non-straight passes are included in the optimization, while the calculation of the Jacobian matrix does not require large computation times. Several tests are performed to validate the proposed method and the results show that tracking error is reduced typically by a factor of two in comparison to the pixel-by-pixel approach and the classical raster path strategy with straight passes. The tracking error can be as low as 2–5% and 1–2% for WJM and PLA, respectively, depending on the complexity of the target surface.
]]>2017-07-05T00:08:12-07:00info:doi/10.1098/rsos.161031hwp:master-id:royopensci;rsos.1610312017-07-05Engineering47161031161031<![CDATA[A frequency quantum interpretation of the surface renewal model of mass transfer]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/7/170103?rss=1
The surface of a turbulent liquid is visualized as consisting of a large number of chaotic eddies or liquid elements. Assuming that surface elements of a particular age have renewal frequencies that are integral multiples of a fundamental frequency quantum, and further assuming that the renewal frequency distribution is of the Boltzmann type, performing a population balance for these elements leads to the Danckwerts surface age distribution. The basic quantum is what has been traditionally called the rate of surface renewal. The Higbie surface age distribution follows if the renewal frequency distribution of such elements is assumed to be continuous. Four age distributions, which reflect different start-up conditions of the absorption process, are then used to analyse transient physical gas absorption into a large volume of liquid, assuming negligible gas-side mass-transfer resistance. The first two are different versions of the Danckwerts model, the third one is based on the uniform and Higbie distributions, while the fourth one is a mixed distribution. For the four cases, theoretical expressions are derived for the rates of gas absorption and dissolved-gas transfer to the bulk liquid. Under transient conditions, these two rates are not equal and have an inverse relationship. However, with the progress of absorption towards steady state, they approach one another. Assuming steady-state conditions, the conventional one-parameter Danckwerts age distribution is generalized to a two-parameter age distribution. Like the two-parameter logarithmic normal distribution, this distribution can also capture the bell-shaped nature of the distribution of the ages of surface elements observed experimentally in air–sea gas and heat exchange. Estimates of the liquid-side mass-transfer coefficient made using these two distributions for the absorption of hydrogen and oxygen in water are very close to one another and are comparable to experimental values reported in the literature.
]]>2017-07-05T00:08:12-07:00info:doi/10.1098/rsos.170103hwp:master-id:royopensci;rsos.1701032017-07-05Engineering47170103170103<![CDATA[Chromium oxide coatings with the potential for eliminating the risk of chromium ion release in orthopaedic implants]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/7/170218?rss=1
Chromium oxide coatings prepared by radiofrequency reactive magnetron sputtering on stainless steel substrates were exposed to Ringer's physiological solution and tested for their electrochemical corrosion stability using an open circuit potential measurement, potentiodynamic polarization, electrochemical impedance spectroscopy and Mott–Schottky analysis. The coatings were found to be predominantly Cr_{2}O_{3}, based on the observation of the dominance of A1g and E_{g} symmetric modes in our Raman spectroscopic investigation and the E_{u} vibrational modes in our Fourier transform infrared spectroscopic measurements on the coatings. We investigated for the presence of chromium ions in Ringer's solution after all of the above electrochemical tests using atomic absorption spectroscopy, without finding a trace of chromium ions at the ppm level for coatings tested under open circuit and at the lower potentials implants are likely to experience in the human body. The coatings were further exposed to Ringer's solution for one month and tested for adhesion strength changes, and we found that they retained substantial adhesion to the substrates. We expect this finding to be significant for future orthopaedic implants where chromium ion release is still a major challenge.
]]>2017-07-05T00:08:13-07:00info:doi/10.1098/rsos.170218hwp:master-id:royopensci;rsos.1702182017-07-05Engineering47170218170218<![CDATA[Terahertz time-domain spectroscopy of edible oils]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/6/170275?rss=1
Chemical degradation of edible oils has been studied using conventional spectroscopic methods spanning the spectrum from ultraviolet to mid-IR. However, the possibility of morphological changes of oil molecules that can be detected at terahertz frequencies is beginning to receive some attention. Furthermore, the rapidly decreasing cost of this technology and its capability for convenient, in situ measurement of material properties, raises the possibility of monitoring oil during cooking and processing at production facilities, and more generally within the food industry. In this paper, we test the hypothesis that oil undergoes chemical and physical changes when heated above the smoke point, which can be detected in the 0.05–2 THz spectral range, measured using the conventional terahertz time-domain spectroscopy technique. The measurements demonstrate a null result in that there is no significant change in the spectra of terahertz optical parameters after heating above the smoke point for 5 min.
]]>2017-06-28T00:08:13-07:00info:doi/10.1098/rsos.170275hwp:master-id:royopensci;rsos.1702752017-06-28Engineering46170275170275<![CDATA[Sticking to rough surfaces using functionally graded bio-inspired microfibres]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/6/161105?rss=1
Synthetic fibrillar adhesives inspired by nature, most commonly by the gecko lizard, have been shown to strongly and repeatedly attach to smooth surfaces. These adhesives, mostly of monolithic construction, perform on par with their natural analogues on smooth surfaces but exhibit far inferior adhesive performance on rough surfaces. In this paper, we report on the adhesive performance of functionally graded microfibrillar adhesives based on a microfibre with a divergent end and a thin soft distal layer on rough surfaces. Monolithic and functionally graded fibre arrays were fabricated from polyurethanes and their adhesive performance on surfaces of varying roughness were quantified from force–distance data obtained using a custom adhesion measurement system. Average pull-off stress declined significantly with increasing roughness for the monolithic fibre array, dropping from 77 kPa on the smoothest (54 nm RMS roughness) to 19 kPa on the roughest (408 nm RMS roughness) testing surface. In comparison, pull-off stresses of 81 kPa and 63 kPa were obtained on the same respective smooth and rough surfaces with a functionally graded fibre array, which represents a more than threefold increase in adhesion to the roughest adhering surface. These results show that functionally graded fibrillar adhesives perform similar on all the testing surfaces unlike monolithic arrays and show potential as repeatable and reusable rough surface adhesives.
]]>2017-06-07T00:07:57-07:00info:doi/10.1098/rsos.161105hwp:master-id:royopensci;rsos.1611052017-06-07Engineering46161105161105<![CDATA[On the formation of fold-type oscillation marks in the continuous casting of steel]]>
http://rsos.royalsocietypublishing.org/cgi/content/short/4/6/170062?rss=1
Asymptotic methods are employed to revisit an earlier model for oscillation-mark formation in the continuous casting of steel. A systematic non-dimensionalization of the governing equations, which was not carried out previously, leads to a model with 12 dimensionless parameters. Analysis is provided in the same parameter regime as for the earlier model, and surprisingly simple analytical solutions are found for the oscillation-mark profiles; these are found to agree reasonably well with the numerical solution in the earlier model and very well with fold-type oscillation marks that have been obtained in more recent experimental work. The benefits of this approach, when compared with time-consuming numerical simulations, are discussed in the context of auxiliary models for macrosegregation and thermomechanical stresses and strains.
]]>2017-06-07T04:09:43-07:00info:doi/10.1098/rsos.170062hwp:master-id:royopensci;rsos.1700622017-06-07Engineering46170062170062