Rough Trend Research Articles

Surface Roughness-Induced Spectral Degradation of Multi-Spaceborne Solar Diffusers Due to Space Radiation Exposure

Solar diffusers (SDs) have often been used as the onboard calibrators for the radiometric calibration of reflective solar band imaging sensors. After being spaceborne, the reflectance of SDs is observed to degrade with spectral dependence due to exposure to solar UV and energetic particle radiation. Long-term spectral reflectance data of SDs onboard multiple LEO imaging sensors, such as the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Visible Infrared Imaging Radiometer Suite (VIIRS) on SNPP, are analyzed. The reflectance of SDs on these three instruments degrades faster for the shorter wavelength (0.4– $0.6~\mu \text{m}$ ) bands than the longer wavelength bands. The Surface Roughness-induced Rayleigh Scattering (SRRS) model is applied to simulate the SD degradation on these instruments, and the growth of the surface roughness parameter of the SDs is derived. It is determined that the change of surface roughness scale length is ~tens of nanometers. To show the consistency of roughness growth rates among the SDs on Terra/Aqua MODIS and SNPP VIIRS instruments, the functional dependences of the growth rates are characterized according to the SD exposure time and the stage of surface roughness. It is also found that the flattening or reverse in the growth trend of the surface roughness for these three SDs occurred around the same interval between October 2013 and October 2015. The confirmation of the applicability of SRRS model with the long-term spectral reflectance data from three independent spaceborne SDs facilitates a better understanding of the origin and physical processes of the SD degradation.

Measurement of financial efficiency and productivity of Turkish Public Universities by using non-parametric methods

Purpose The purpose of this paper is to measure the financial efficiency and productivity of 23 public universities founded in 1992 in Turkey over the period between 2004 and 2013. The results obtained will provide managerial information and act as a guide to public universities’ administrations, in using their resources more effectively. Design/methodology/approach Data envelopment analysis is applied to assess the relative financial efficiency of these universities, while Malmquist total factor productivity index is used to measure the total factor productivity change concerning financial inputs of the universities. Findings The number of financially efficient universities and the number of universities showing an increase in their productivity according to their financial inputs change annually and both of them display a rough trend over the years. A decrease of about 5 percent in the financial productivity of the universities is observed which stems from a technological recession. Therefore, public universities in Turkey are not able to develop effective policies to diversify, increase and use their financial resources. Originality/value When the lack of studies within the literature measuring the financial efficiency of higher education institutions is taken into account, this study can fill a gap in this area. The analyses conducted here distinguish from existing studies on this subject with regards to the extent and diversity of financial data set and the measurement of both efficiency and productivity change of universities considering financial inputs concurrently.

Analytical Investigation of the Micro Groove Surface Topography by Micro-Milling.

Micro-milling is an emerging processing technology for machining micro- and high-precision three dimensional parts that require the use of various materials (with sizes ranging from tens of micrometers to a few millimeters) in the field of advanced manufacturing. Therefore, it can be applied to manufacture the micro parts, but new challenges are raised about parts with high surface quality. Herein, both surface formation and micro machined surface roughness models are studied, with the aim of solving complicated problems regarding the quality of surface finish when micro-milling metallic materials. From a theoretical point of view, the first model for surface formation processes considering the strain gradient plasticity theory was built in the area around the cutting edge, and the minimum uncut chip thickness equation was derived. The model accounts for the properties of the work material in tertiary and quaternary zones on the minimum chip thickness. A second model for micro machined surface roughness based on the relationship of kinematics between cutting process and cutter edge was also developed, which takes the influences of tool run out into account. Both proposed models were introduced to analyze the tendency of surface roughness for micro grooves. Both models were also used to justify experimental results. The results show that the developed surface roughness model could be useful in predicting both roughness parameters and trends as a function of cutting parameters.

Ultra-smooth and hydrophobic nitrogen-incorporated ultranano-crystalline diamond film growth in C-H-O-N gas phase system via microwave plasma CVD

The ultra-smooth surface and hydrophobic nitrogen-incorporated ultra-nano-crystalline diamond (N-UNCD) was directly synthesized by equilibrating the etching effect of OH radical and growth promotion of CN and CH in the 5% CH4 added H2 plasma environment with additional feeding of constant 0.16% O2 and from 0.3% to 3.3% N2 contents. The initially decreasing and then increasing trend of surface roughness, i.e., from as-grown appearance with pits to smooth and then to worm-like surface, was resulted from the offset and even suppressive effect on OH etched holes by the faster growth rate that under the help of more N2 promoted chemical groups of CH and CN. In addition, chemical composition, i.e., the large amount of sp2 phases (sp2/sp3 ratio up to 1.399) and H termination of N-UNCD surface (proportion was 75.54 ± 3.8%), played an another enhancing function for repelling water (contact angle from 81.3° to 93.8°) although the surface roughness decreased to smoothest of 1.36 nm in Root-Mean-Square (RMS) in the presence of N2 addition from 0.3% to 1%. However, continuing adding N2 to 3.3%, the formed surface (RMS 8.98 nm) with worm-like ultra-nano diamond crystallites together with higher H reconstructed sp2 contents (sp2/sp3 ratio rose to 1.478) further boosted the hydrophobicity, at which the contact angle was finally increased to 110.2°. Therefore, in C-H-O-N gas system, ultra-smooth and uniform N-UNCD surface with excellent hydrophobicity can be obtained by a one-step method without any post-treatment.

Applications of Digital Image Correlation (DIC) and the Strain Gage Method for Measuring Dynamic Mode I Fracture Parameters of the White Marble Specimen

Digital image correlation (DIC) and the strain gage method are both widely used in characterizing the fracture mechanisms of materials. However, the quantitative comparisons of rock fracture parameters between the two methods have been studied insufficiently. In this paper, dynamic three-point bending impact tests were performed on white marble specimens using DIC and the strain gage method simultaneously. The complete cracking process was recorded by two high-speed cameras situated on either side of the specimen. The crack propagation velocities were obtained and the dynamic stress intensity factors (DSIFs) were calculated by both methods for analysis and comparison. The experimental results show that the crack propagation velocities almost remain constant during the cracking process, and the evolutions of strain values recorded by gages are consistent with the modified strain variations obtained theoretically. DSIFs calculated by DIC show good agreement with the results obtained from strain gages #1 to #4, while the size effect and the multiple stress waves interfere with the strain signals sensed in strain gage #5, causing a relatively larger deviation in the DSIF. In addition, the complete fracture process (including the variations in successive displacement and strain fields) can be obtained by the DIC method, while a rough changing trend in the DSIF can be given by the strain gage method with a limited number of strain gages.

Bearing fault diagnosis under time-varying rotational speed via the fault characteristic order (FCO) index based demodulation and the stepwise resampling in the fault phase angle (FPA) domain

Time–frequency representation (TFR) based order tracking algorithm can help to realize rolling bearing fault diagnosis under time-varying rotational speed without using a tachometer. Among this TFR based algorithm, however, two important steps, determining the optimal resonance band and realizing the TFR based resampling with high accuracy, are not well addressed. As such, a new criterion called fault characteristic order index (FCOindex) is designed to select the optimal filter band to enhance the fault-related components under time-varying rotational speed, and a new stepwise resampling algorithm is proposed based on the fine instantaneous fault characteristic frequency (IFCF) trend extracted from the STFT and CWT based envelope TFRs. The proposed algorithm contains five main steps: (a) Band-pass filtering the raw signal with several specially designed filter bands, (b) Constructing the FCOindex as the criterion and selecting the filter band with the highest FCOindex as the optimal filter band, (c) extracting the fine IFCF trend from the CWT based envelope TFR of the filter signal and the STFT based rough IFCF trend, (d) resampling the filter signal with the fine IFCF trend using a new stepwise resampling algorithm, and (e) realizing the fault detection using the FCO spectrum. The effectiveness of the proposed method has been validated using the simulated and experimental signals.

Does intermediate spreading-rate oceanic crust result from episodic transition between magmatic and magma-dominated, faulting-enhanced spreading?—The Costa Rica Rift example

Ocean-bottom seismograph and multichannel streamer wide-angle seismic data are jointly analysed and compared with reflection images, bathymetric maps and potential field data, to reveal the detailed structure of layer 2 of the oceanic crust formed at the intermediate spreading Costa Rica Rift (CRR). Separate modelling of each wide-angle data set independently reveals a gradual increase in P-wave velocity with distance (hence crustal age) from the ridge axis, with a model derived from their joint inversion, in turn, displaying a pattern of shorter-wavelength structural complexity in addition to a background flow-line trend. Normalizing against a ridge-located reference velocity–depth model reveals that, off-axis, velocity perturbations are correlated with trends in basement roughness and uplift; regions of rougher and uplifted basement correlate with slower layer 2 velocity, <0.5 km s−1 faster than at the ridge axis, and thinner sediment cover, while smoother basement and locations where sediment cover forms a continuous seal over the oceanic basement, are mirrored by regions of relatively higher velocity, 1.0–1.4 km s−1 faster than at the CRR. These velocity variations are interpreted to reflect periodic changes in the degree of magma supply to the ridge axis. Using a combination of global and shipboard magnetic data, we derive a spreading history model for the CRR which shows that, for the past 5 Ma, spreading has been asymmetric. Comparing the seismic model structure with variations in full spreading rate over this period, reveals a correlation between periods of slower spreading and slower layer 2 velocity, basement roughness and uplift, and faster spreading, higher velocity and smoother basement structure. Zones of slower velocity also correlate with lows in the residual mantle Bouguer anomaly, interpreted as most likely reflecting corresponding regions of lower density in the lower crust or upper lithospheric mantle. Using ODP borehole 504B as ground-truth, we show that periods of faster spreading are associated with phases of magmatic accretion, interspersed by phases of increased asymmetric tectonic extension that likely facilitates fluid flow to the deeper crust and results in metamorphic alteration, manifest as the modelled density anomalies. Overall, our study shows that the mode of CRR crustal formation is sensitive to relatively small changes in full spreading rate within the range of 50–72 mm yr−1, that tips the balance between magmatic and magma-dominated crustal formation and/or tectonic stretching, as characterized by significant variation in the fabric and physical properties of layer 2. We further hypothesize that this inherited structure has a direct influence on the subsequent evolution of the crust through secondary alteration. We conclude that descriptive phrases like ‘ocean crust formed at an intermediate-spreading rate’ should no longer be used to describe an actual crustal formation process or resulting crustal structure as, over the full range of intermediate spreading rates, a fine tipping-point dictates an episodic transition between primarily magmatic accretion and magma-dominated crustal formation coupled with enhanced faulting, with their asymmetry recorded in either ridge flank.

Numerical study on lubrication performance of engine main bearing with rough surface considering axial movement of crankshaft

In actual operation of an engine, the crankshaft will move along the axis direction of engine main bearings under the combined influence of various influencing factors. Considering the axial movement and crankshaft deformation, a new lubrication model of engine main bearings with rough surface was built based on the average Reynolds equation. The influence of axial movement of deformed crankshaft on performance of main bearing with rough surface was studied. In this study, the axial movement law of deformed crankshaft is measured through experiment, and the finite element method was applied to solve the tilting of crankshaft in the bearing bore resulted from the crankshaft deformation. The results show that the axial movement of deformed crankshaft has a significant impact on performance of main bearing with rough surface. No matter whether or not the surface roughness is considered, the journal center trajectories of main bearings are unclosed three-dimensional space curve due to the axial movement of deformed crankshaft. The influence level of the axial movement of deformed crankshaft on lubrication characteristics of main bearings is directly related to the surface roughness. The influence trend and level of the surface roughness on lubrication characteristics of main bearings are obviously changed when considering the axial movement of crankshaft.

Early hMSC morphology and proliferation on model polyelectrolyte multilayers.

Polyelectrolyte multilayers (PEMs) are a category of materials commonly used as coatings on surfaces that interact with cells. The properties of PEMs have been established to be controlled by not only polyelectrolyte choice, but by the identity of the initially applied (bottom) layer. In this work, 5-bilayer PEMs consisting of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) were coated on gold-sputtered quartz substrates with different first layer materials. A final poly-l-lysine (PLL) layer was added to all PEMs to provide identical top layers conducive to cell growth. As in previous work, initial layer selection affected PEM roughness. All coated surfaces, including the PLL-only control, showed increased dispersive surface energy but decreased polar surface energy, as compared to uncoated surfaces. When human mesenchymal stem cells (hMSCs) were cultured on these surfaces, analysis through lateral cell imaging for the first 90 min and fluorescent staining after 1 day showed improved attachment on surfaces with a PDADMAC bottom layer. However, after 4 days, a higher cell density was observed on the PLL-only and uncoated control surfaces, indicating that the PEMs negatively affected hMSC proliferation. Both the long and short time period results did not correlate to any of the roughness and surface energy trends, indicating more complex interactions between the cells and the surface relating to charge distribution and functional group density.

Investigating the Effect of Cutting Parameters of Ti–6Al–4V on Surface Roughness Based on a SPH Cutting Model

This work establishes a 2D numerical model to simulate the cutting process of workpieces made of Ti–6Al–4V, by applying an improved Smoothed Particle Hydrodynamics algorithm together with a modified constitutive model based on the Johnson–Cook model known as Hyperbolic Tangent (TANH). The location information of the surface particles obtained by the SPH cutting model are used to evaluate the variation trend of surface roughness with different parameters. Parameters that affect the surface roughness are investigated in detail by using the Taguchi method and the SPH cutting model. The present work provides an efficient and cost-effective approach to determine the optimal parameters for cutting processes for Ti–6AL–4V workpieces, through computer simulations in virtual environments, instead of expensive and time-consuming cutting experiments using actual workpieces.

Statistical characteristics and logarithmic EWMA control method of bearing raceway's surface roughness by superfinishing

The bearing raceway is the main working surface of the bearing and good surface integrity is required. Since superfinishing is an important method for achieving high surface quality, it is usually used as the last processing to play a very essential part in improving the surface integrity of bearing raceway. In this paper, we proposed a superfinishing surface quality control method, by which we could determine whether there were systematic factors that caused surface quality anomalies by measuring and analysing the roughness data without directly measuring process parameters and environmental indicators. Firstly, we verified through experiment that the surface roughness by superfinishing did not obey the normal distribution but obeyed the logarithmic normal distribution. We interpreted this statistic characteristics by the mechanism of the relationship between roughness and random factors in the superfinishing. Then, according to above findings, and considering the possible trend of surface roughness during continuous processing, we designed a logarithmic exponentially weighted moving average (EWMA) method to test the surface roughness and judge whether it was under control. Finally, the effectiveness of this surface quality control method in superfinishing was verified by applying it to the actual bearing raceway outer ring machining.

Characterization of the nature of shear-induced agglomerates as hard and soft in chemical mechanical polishing slurries

The nature of agglomerates either hard or soft could determine the kind of defects created during the chemical mechanical planarization/polishing process. To understand the nature of shear-induced agglomerates, the silica slurry at different pH is subjected to high shear rate and time to form agglomerates. Subsequently, these stressed slurry samples are subjected to low shear rates 100–1000 s−1 for time 100–1000 s, corresponding to the conditions for which de-agglomeration is observed. Based on the comparison of percentage de-agglomeration in stressed versus as-received slurries, it is qualitatively shown that agglomerates formed due to shear-induced agglomeration in basic pH slurries are soft agglomerates, whereas those formed in neutral and acidic pH slurries are hard agglomerates. Also, between neutral and acidic pH slurries, shear-induced agglomerates in acidic pH slurry are relatively strongly held than the ones that are formed in neutral pH slurries. Subsequently, the nature of agglomerates was compared to defectivity and surface roughness trend of BD1 low-k wafers in silica slurries at different pH from the previous work.

Smoothed particle hydrodynamics simulation and experimental analysis of SiC ceramic grinding mechanism

Crack induced surface/subsurface damage in SiC ceramic grinding limits the industrial application. A single-grain scratching simulation based on the smoothed particle hydrodynamics (SPH) has been used to analyze the SiC grinding mechanism, including the material removal process, scratching speed effect on crack propagation, ground surface roughness, and scratching force. The simulation results showed that the material removal process went through the pure ductile mode, brittle assisted ductile mode, and brittle mode with the increase of the depth of cut. The critical depth of cut for ductile-brittle transition was about 0.35 µm based on the change of ground surface crack condition, surface roughness, and maximum scratching force. Increasing the scratching speed promoted the transformation of deep and narrow longitudinal crack in the subsurface into the shallow and wide transverse crack on the surface, which improved the surface quality. The SPH simulation results were indirectly validated by the cylindrical grinding experiments in terms of the critical single grain depth of cut for ductile-brittle transition, and the trend of ground surface roughness and grinding forces.

Electrochemical deposition of silver and copper from a deep eutectic solvent studied using time-resolved neutron reflectivity

Here, we describe new developments in the study of electrodeposition processes with time-resolved dynamic neutron reflectivity (NR) methods to achieve insights into the differences between growth of metal films using a range of electrochemical control functions. We show that the temporal resolution has increased from 1 to 2 h per data set (in our previous studies) to approximately 8 min. We have studied the electrochemical deposition of copper and silver as thin-film metals onto a gold electrode substrate from a deep eutectic solvent using potentiodynamic (PD), potentiostatic (PS) and galvanostatic (GS) electrochemical control functions. In particular, we have utilised novel developments in neutron reflectivity methods to acquire real-time data for the growing metal films. Event mode capture of neutron scattering events, as a function of momentum transfer vector, Q, during electrochemical growth has enabled time-resolved measurement of the neutron reflectivity, R(Q), profiles of the growing metal films. Subsequent fitting and iterative optimisation of the R(Q,t) data reveals the thickness, roughness and relative density (spatially resolved solvent content) of the metal film during growth. These data show that the different electrochemical growth methodologies exhibit different trends in thickness, roughness and solvation. Silver films show an increasing roughness trend with time but these trends are largely independent of growth method. In contrast, the roughness of copper films, grown under similar conditions, shows a strong dependency on growth method with PS methods producing smoothest films. These conclusions are confirmed by ex-situ AFM measurements. The fitted NR data show that the Cu and Ag films contain between 5 and 10% volume fraction solvent. Furthermore, we have explored different NR data fitting methodologies in order to process the large numbers of data sets produced. Gratifyingly, the different methodologies and starting conditions yield a very consistent picture of metal film growth.

Forecast of Non-Equal Interval Track Irregularity Based on Improved Grey Model and PSO-SVM

Effective forecasting of track irregularity development trend is critical to the railway maintenance and management. In China, track irregularity is commonly evaluated via an index called track quality index (TQI). According to the trend and random of the TQI development, a hybrid forecasting method composed of the improved grey model (GM(1,1)) and a particle swarm optimization support vector machine (PSO-SVM) is proposed in this paper. First, a non-equal interval sequence is transformed into an equal interval sequence, and an improved GM(1,1) based on the compound trapezoid quadrature formula is proposed to estimate the short-term rough trend of the TQI. Then, PSO-SVM is adopted to correct the rough results and obtain an accurate TQI trend. Numerical experiment results show that the proposed forecast method outperforms the track irregularity trend component and the grey nonlinear periodic correction method and the non-equal interval weighted grey model and neural networks in terms of relative error.

Choroidal Thickness In and Outside of Vascular Arcade in Healthy Eyes Using Spectral-Domain Optical Coherence Tomography.

To study the distribution of choroidal thickness (CT) in and outside of the vascular arcade, as well as at the fovea in healthy eyes using spectral-domain optical coherence tomography (OCT). Seventy healthy eyes were examined with OCT to obtain nine horizontal lines in and outside of the vascular arcade. Nine points including the central point of the line were chosen in 0.5-mm intervals to calculate CT. CT was measured at a total of 81 points in each patient to construct a map of CT distribution. Average subfoveal CT showed a significant relationship with age (P < 0.001) and axial length (P = 0.001). In all nine horizontal lines, CT showed a rough trend of being thickest at a particular point and decreasing thereafter. The aspect of CT distribution was different among the nine horizontal lines (P < 0.001), and the near superotemporal line displayed the thickest choroid among the lines. The difference of the trend between temporal vertical lines was significant as well (P < 0.001). The CT generally decreased with age, but it decreased much faster in old age than in relatively younger people. CT displayed large variations among different points in and outside of the vascular arcade. The thickest choroid was located at the point superior to the fovea, not the fovea itself. Such physiological variations should be considered when interpreting pathologic changes of the choroid.

Orbital Parameters of the Eclipsing Detached Kepler Binaries with Eccentric Orbits

Abstract We present precise values of the eccentricity and periastron angle of 529 detached, eccentric, eclipsing stars from the Kepler Eclipsing Binary catalog that were determined by modeling their long cadence data. The temperatures and relative radii of their components as well as their mass ratios were calculated based on approximate values of the empirical relations of MS stars. Around one-third of the secondary components were revealed to be very late dwarfs, some of them possible brown dwarf candidates. Most of our targets fall below the envelope P(1 − e 2)3/2 = 5 days. The (e, P) distribution of the known eccentric binaries exhibits a rough trend of increasing eccentricity with the period. The prolonged and continuous Kepler observations allowed us to identify 60 new highly eccentric targets with e &gt; 0.5.

TSEM-based contour analysis as a tool for the quantification of the profile roughness of silica shells on polystyrene core particles

Core-shell (CS) particles with a polymeric core and a silica shell play an important role in the materials and (bio)analytical sciences. Besides the establishment of reliable synthesis procedures, comprehensive particle characterization is essential for batch-to-batch reproducibility and objective performance assessment across architectures, protocols, and laboratories. Particle characterization with respect to size, size distribution, shell thickness and texture, surface area and roughness or materials composition is commonly conducted with different analytical methods, often on different samples. Our approach uses a dual-mode TSEM/SEM set-up with an EDX detector to obtain a complementary data set with sufficient statistical confidence of one and the same sample on a single instrument. Our protocol reveals information about size, size distribution and shell thickness of the various particles employed from overview images, while an increased field of view (FOV) and high-resolution EDX analysis yields detailed information on shell texture and elemental composition. An image analysis tool was developed to derive and quantify the profile roughness of CS particles from individual beads. Comparison with surface roughness data from AFM showed a similar trend in roughness across the series of particles. Reliable classification into smooth and rough is proposed and roughness changes within different particle batches were tracked systematically.

Evaluating the impact of ballast undercutting on the roughness of track geometry over different subgrade conditions

The progressive degradation of railway ballast is often cited as a primary factor that contributes to the development of track roughness, while ballast renewal (undercutting) attempts to manage its long-term development. Soft subgrades have been shown to strongly influence track geometry and are a contributing factor that has not been considered during conventional track maintenance. This study evaluated the impact of undercutting on long-term trends in track geometry roughness, and what impact softer subgrades had on the effectiveness of undercutting. A combined 6.90 km of Class II–IV heavy-haul track in Western Canada (undercut in 2010 and 2011) formed the basis for this analysis. Annual traffic on these sections typically totals 50 million gross tonnes. Long-term trends in the track crosslevel, alignment, and surface roughness after ballast renewal were derived from 50 track geometry surveys carried out over a five-year period (2010–2015). The results showed that undercutting significantly reduced track roughness over sand, silt, clay, or till subgrades; however, it was often ineffective when used over soft organic subgrades. Thus, while ballast degradation is the primary cause of track roughness in segments constructed on mineral subgrades, it is not a mechanism that results in track geometry roughness over soft organic soils.

Laser Direct-Part Marking of Data Matrix Barcodes on the Surface of Metal Alloy Material

The influences of laser processing parameters on the symbol contrast and surface roughness of Data Matrix barcodes were studied by single factor experiments using a Q-switched lamp pumped Nd:YAG laser. The orthogonal experiments were carried out to further study the relationship between laser parameters and surface roughness. Multivariate nonlinear regression analyses were performed based on the orthogonal experimental results and a mathematical relationship between parameters and surface roughness was established. The results show that the change trend of surface roughness is similar to symbol contrast with the increase of laser parameters. Both the average power and two different overlaps are important factors affecting the surface roughness and symbol contrast. But the current intensity has an insignificant impact on the surface roughness. The developed regression model can be used to predict the roughness of Data Matrix barcodes. This study can improve industrial application of laser direct part marking technology on titanium alloy substrates.