First-order Components Research Articles

Analysis of differences in vegetation phenology cycle of abandoned farmland, using harmonic analysis of time-series vegetation indices data: the case of Gwangyang City, South Korea

ABSTRACT Globally, countries have experienced substantial increases in farmland abandonment. Although vegetation phenology is a key factor for the classification of land use, understanding of the phenological change of abandoned farmland is lacking. Using harmonic analysis of NDVI and NDWI extracted from Landsat imagery, this study investigates the distinctive phenological characteristics of abandoned farmland, which contrasts with that of three other agricultural types (paddy, agricultural field, orchard) in the study site of Gwangyang City in Jeollanam Province, South Korea. The results suggest that abandoned farmland has higher overall greenness coverage and overall water content in vegetation than the other uses. In terms of both indices, abandoned farmlands changed with relatively less fluctuation than those of other uses, suggesting the existence of constant and unmanaged vegetation from ecological succession, which differs from crop fields that undergo cultivation procedures. The significant harmonic components differed among agricultural types and vegetation indices. In paddy, NDVI was explained with multiple, higher-order harmonic components, while in other types only first-order components met the 5% statistical significance level. With NDWI, land types were more clearly discernible, because of the different cultivation procedures involving water: wet-field method (paddy), dryland farming (orchard, agricultural field), and no cultivation (abandoned farmland). The analysis confirms that harmonic analysis could be useful in discerning abandoned farmland among areas of active agricultural use and shows that the statistical significance of harmonic terms can be employed as indicators of different agricultural types. The observed pattern of the geographic distribution of abandoned farmland has policy implications for the promotion of sustainable reuse of marginal farmland.

Assessment of Stress Raiser Factor Using Finite Element Solvers

The stress raisers factor around circular holes in a plate exposed to uniform tensile load at the edges has been studied using Finite Element Analysis solvers. The effect of mesh quality on stress raisers factor, the maximum Von Mises stresses, the computing time, and the percentage error has been examined. 4 Node Quadrilateral Element and 8 Node Quadrilateral Element were utilized respectively as first-order component (4NQE) and higher-order component (8NQE) to assess the maximum Von Mises stress and the numerical stress raiser factor (Kn) at various mesh sizes. The maximum Von Mises stress and the stress raiser factor were determined using the following finite element solvers: ABAQUS, ANSYS, CATIA, STRAND 7, ALGOR, COSMOS/M, and FEMAP. The estimations of the numerical stress raiser factor (Kn) were compared with the theoretical stress raiser factor (Kt). There were discrepancies observed between the maximum Von Mises stresses of the FEA solvers.

Vortex-induced vibration of bridge decks: Describing function-based model

A describing function (DF)-based model is introduced for the simulation of vortex-induced vibration (VIV) of bridge decks. Similar to the linear frequency response function, the DF is the complex ratio of the first-order component of the nonlinear output to the harmonic input. The DF can be either identified using the forced vibration technique or based on the VIV nonlinear response time history. An iterative procedure is accordingly developed to predict the VIV response with the DF-based model, and an equivalent-damping-ratio-based simplified method is further proposed to efficiently obtain the limit cycle oscillation (LCO) amplitude of VIV. It is demonstrated that the conventional van der Pol-type model is equivalent to a special case of the DF-based model for VIV. Three case studies involving various cross-sections are utilized to validate the simulation accuracy and efficiency of the proposed DF-based model for typical features at VIV lock-in such as LCO and hysteresis phenomena. The vertical VIVs can be well captured by the DF-based model, while its capability of simulating the torsional VIVs requires further improvement. Furthermore, the predictive capability of DF-based model for vertical VIVs of bridge decks within a wide range of mass-damping conditions is highlighted.

Frequency coupling characteristics of electromagnetic oscillation in grid‐connected converters

Under certain conditions, grid-connected voltage source converter (VSC) may result in electromagnetic oscillations. Many coupling components with different frequencies could be observed in converter outputs when oscillation happens. The characteristics and mechanism of frequency coupling phenomenon in oscillations of VSC are studied. The magnitude relationship between first-order components in the three-phase domain is drawn by impedance model. The two first-order components will result in higher-order components due to the non-linearity of VSC controller. There are mainly three coupling paths in a controller: phase-locked loop, DC voltage fluctuation and overmodulation. The coupling mechanism and frequency distribution characteristics are investigated in this study. Theoretical results are validated by simulations with PSCAD/EMTDC.

Improvement of integrator backstepping control for ships with concise robust control and nonlinear decoration

Course-keeping control through normal integrator backstepping method has defects of introducing many adjustment parameters and not considering the energy cost of actuator. In order to enhance the performance of integrator backstepping controller, a control law formed by closed-loop gain-shaping algorithm is adopted to replace the linear terms in the original control law. The energy cost is reduced by nonlinear decoration of sine function to the controller output, and the steering interval is lengthened according to the analyzation of full-scale sea trail data from training vessel Yukun. To decrease overshoot, the desired course is filtered by a first-order inertial component. Then a performance index is proposed to verify the performance of each control strategy combination. Simulation results show that the proposed controller has good robustness to the perturbation of steering mechanisms and ship model in rough sea states. At the same time, mean rudder angle is decreased by 17.3%, so energy consumption is reduced. The algorithm proposed in this paper has good theoretical analysis, satisfactory robustness with less parameters, reasonable steering frequency and remarkable energy saving effect.

Understanding consumers’ willingness to use ride-sharing services: The roles of perceived value and perceived risk

In order to popularise the sustainable transport innovation of ride-sharing, it is critical for service providers and policymakers to understand the factors affecting ride-sharing willingness of potential users. This research explores the drivers of non-users’ willingness to use ride-sharing services from the perspectives of perceived value and perceived risk, where perceived value and perceived risk are both conceptualised as formative second-order constructs constituted by their first-order value components and risk components. The data was collected in China through an online questionnaire from 378 respondents who had never used a ride-sharing platform. Partial least squares structural equation modelling (PLS-SEM) is used to verify the research model and hypotheses. The empirical results reveal that perceived value is positively associated with consumer willingness to participate in ride-sharing, but perceived risk is negatively related to consumers’ ride-sharing intention. Contrary to expectations, perceived risk positively moderates the effect of perceived value on consumers’ ride-sharing intention. This study contributes to a deeper understanding of the effects of consumers’ value perception and risk perception on their acceptance of internet-based ride-sharing services. Measures to promote ride-sharing include maximising consumers’ value of ride-sharing and their perception of value as well as reducing potential risks in ride-sharing process.

A Sub-Regional Extraction Method of Common Mode Components from IGS and CMONOC Stations in China

There is always a need to extract more accurate regional common mode component (CMC) series from coordinate time series of Global Positioning System (GPS) stations, which would be of great benefit to describe the deformation features of the Earth’s surface with more reliability. For this purpose, this paper combines all 11 International Global Navigation Satellite System (GNSS) Service (IGS) stations in China with over 70 stations selected from the Crustal Movement Observation Network of China (CMONOC) to compute CMC series of IGS stations by using a principal component analysis (PCA) method under cases of one whole region and eight sub-regions. The comparison results show that the percentage of first-order principal component (PC1) in North, East and Up components increase by 10.8%, 16.1% and 25.1%, respectively, after dividing the whole China region into eight sub-regions. Meanwhile, Root Mean Square (RMS) reduction rates of residual series that have removed CMC also improve obviously after partitioning. In addition, we compute displacements of these IGS stations caused by environmental loadings (including atmospheric pressure loading, non-tidal oceanic loading and hydrological loading) to analyze their contributions to the non-linear variation in GPS coordinate time series. The comparison result shows that the method we raise, PCA filtering in sub-regions, performs better than the environmental loading corrections (ELCs) in improving the signal-to-noise ratio (SNR) of GPS coordinate time series. This paper raises new criteria for selecting appropriate CMONOC stations around IGS stations when computing sub-regional CMC, involving three criteria of interstation distance, geology and self-condition of stations themselves. According to experiments, these criteria are implemental and effective in selecting suitable stations, by which to extract sub-regional CMC with higher accuracy.

An optimal linear combination model to accelerate PPP convergence using multi-frequency multi-GNSS measurements

We propose an optimal ionospheric-free linear combination (LC) model for dual- and triple-frequency PPP which can accelerate carrier phase ambiguity and decrease the position solution convergence time. To reduce computational complexity, a near-optimal LC model for triple-frequency PPP is also proposed. The uncombined observation (UC) model estimating ionospheric delay gives the best performance, because all information contained within the observations are kept. The proposed optimal and near-optimal LC models are compared with the UC model, using both simulated and real data from five GNSS stations in Australia over 30 consecutive days in 2017. We determine a necessary and sufficient condition for a combination operator matrix which can eliminate the first-order ionospheric component to obtain the optimal LC model for dual- and triple-frequency PPP. Numerical results show that the proposed LC model is identical to the UC model. In addition, the proposed near-optimal LC model even outperforms the current LC models. Ambiguity resolution (AR) is faster and positioning accuracy is improved using the optimal triple-frequency LC model compared to using the optimal dual-frequency LC model. An average time-to-first-fix of 10 min with a fixing success rate of 95% can be achieved with triple-frequency AR.

The component structure of the scales for the assessment of positive and negative symptoms in first-episode psychosis and its dependence on variations in analytic methods

A secondary analysis was undertaken on Scales for the Assessment of Positive and Negative Symptoms (SAPS/SANS) data from 345 first-episode psychosis (FEP) patients gathered in the West London FEP study. The purpose of this study was to determine: (i) the component structure of these measures in FEP (primary analyses), and (ii) the dependence of any findings in these primary analyses on variations in analytic methods. Symptom ratings were exposed to data reduction methods and the effects of the following manipulations ascertained: (i) level of analysis (individual symptom vs. global symptom severity ratings), (ii) extraction method (principal component vs. exploratory factor analysis) and (iii) retention method (scree test vs. Kaiser criterion). Whilst global ratings level analysis rendered the classic triad of psychotic syndromes (positive, negative and disorganisation), symptom level analyses revealed a hierarchical structure, with 11 first-order components subsumed by three second-order components, which also mapped on to this syndrome triad. These results were robust across data reduction but not component retention methods, suggesting that discrepancies in the literature regarding the component structure of the SAPS/SANS partly reflect the level of analysis and component retention method used. Further, they support a hierarchical symptom model, the implications of which are discussed.

Analysis of Combustion Stability Based on the Negative Pressure Characteristic of Furnace

Under the low load and flexible peaking operation mode, it is very important to maintain the stable of the thermal power unit. To study the combustion characteristics of the unit under steady condition. We take a 600WM thermal power unit for example to illustrate the mechanism of the influence of combustion stability on the furnace negative pressure. The correlation coefficient method was used to analyze the relationship between related factors and negative pressure fluctuations. After eliminating the disturbance factors, the negative pressure fluctuation caused by combustion was studied. Combining the negative pressure power spectral density with the load and first-order components of the load, we establish a two-tuples combustion model. Two indicators of combustion-order and symmetry-order were established to evaluate the furnace combustion stability. Extracting the operating characteristics of two-tuples model during stable combustion and unsteady combustion. We found that the combustion-order when the combustion is stable is smaller than the combustion-order when the combustion is not stable, and the symmetry-order tends to be stable, and the symmetry of the two-tuples distribution is good. The combustion characteristics have guiding significance for the determination of the subsequent operational stability control strategy.

Optimal-arrangement-based four-scanning-heads error separation technique for self-calibration of angle encoders

Conventional methods for the calibration of angle encoders typically only consider the graduation error of the encoder’s circular scale. However, the radial motion of the circular scale during its rotation, due to its eccentricity and the axis of rotation radial error motion, can also introduce noticeable errors to the angle measurement in most practical applications. Based on the analysis of the influence of radial motion, an optimal-arrangement-based four-scanning-heads error separation technique for in situ self-calibration of angle encoders is presented. This Fourier-based technique uses the basic self-calibration model to measure the first-order Fourier component of the encoder error which includes the contribution of eccentricity. Meanwhile, the separation technique is utilized to separate the residual Fourier components of the graduation error from the measurement deviation due to radial error motion. The effect of the scanning heads’ angular position errors on the calibration results is discussed. Optimal arrangements of the four heads are achieved to avoid the suppression of the Fourier components, and reduce the propagation of errors. Numerical results and experimental comparisons demonstrate the effectiveness of the proposed method. Moreover, this technique can also be used for measuring the spindle radial error motion for some users.

Linearity Comparison of Silicon Carrier-Depletion-Based Single, Dual-Parallel, and Dual-Series Mach–Zehnder Modulators

In this paper, a model is built to investigate the linearity of silicon carrier depletion based Mach–Zehnder modulators (MZMs). By approximating the nonlinear electro-optical response of a PN junction with a fourth-order polynomial, the model quantitatively calculates the modulation linearity of three different MZM configurations that have been widely used in analog optical links, i.e., single, dual-parallel, and dual-series MZMs, and qualitatively explains their respective operation mechanisms to suppress the third-order intermodulation distortion. The optimal operation condition of each configuration is derived to enhance the first-order harmonic component and suppress the nonlinear distortion. A fair comparison is performed between the three configurations in terms of their robustness, footprint, strength of the first-order harmonic component, stability, and tolerance against variations of driving RF power and control error, and so on. The result indicates that the dual-series MZM represents a reasonable tradeoff between these performance characteristics of interests.

Counterproductive hiring discrimination against women

PurposeMentioning car and motorcycle licences on a resume sends a signal of strong mobility, which should increase the chances of getting a job in congested traffic areas. The purpose of this paper is to examine whether this is the case for both women and men.Design/methodology/approachThe authors implement an experimental design in order to test for the existence of gender discrimination. The authors use the first-order stochastic dominance (FOSD) criterion and estimate components models.FindingsThe authors find that holding a motorcycle licence leads to a counterproductive selection of female candidates, since the highest commuting mobility meets the lowest hiring rate.Research limitations/implicationsThe methodology developed in the paper can be used for all correspondence test data.Originality/valueThe authors examine effects that have not been observed thus far in the literature, namely, the effects of gender crossed with the effects of the class of driving licence that is mentioned on the resume. The authors also advocate the use of the FOSD criterion to discrimination studies.

Tolerance to Morphine-Induced Inhibition of TTX-R Sodium Channels in Dorsal Root Ganglia Neurons Is Modulated by Gut-Derived Mediators

SummaryIn the clinical setting, analgesic tolerance is a primary driver of diminished pain control and opioid dose escalations. Integral to this process are primary afferent sensory neurons, the first-order components of nociceptive sensation. Here, we characterize the factors modulating morphine action and tolerance in mouse small diameter dorsal root ganglia (DRG) neurons. We demonstrate that acute morphine inactivates tetrodotoxin-resistant (TTX-R) Na+ channels in these cells. Chronic exposure resulted in tolerance to this effect, which was prevented by treatment with oral vancomycin. Using colonic supernatants, we further show that mediators in the gut microenvironment of mice with chronic morphine exposure can induce tolerance and hyperexcitability in naive DRG neurons. Tolerance (but not hyperexcitability) in this paradigm was mitigated by oral vancomycin treatment. These findings collectively suggest that gastrointestinal microbiota modulate the development of morphine tolerance (but not hyperexcitability) in nociceptive primary afferent neurons, through a mechanism involving TTX-R Na+ channels.

First- and second-order Raman scattering from MoTe2 single crystal

We report on Raman experiments performed on a MoTe2 single crystal. The system belongs to the wide family of transition metal dichalcogenides which includes several of the most interesting two-dimensional materials for both basic and applied physics. Measurements were performed in the standard basal plane configuration, by placing the ab plane of the crystal perpendicular to the wave vector k i of the incident beam to explore the in-plane vibrational modes, and in the edge plane configuration with k i perpendicular to the crystal c axis, thus mainly exciting out-of-plane modes. For both configurations we performed a polarization-dependent study of the first-order Raman components and detailed computation of the corresponding selection rules. We were thus able to provide a complete assignment of the observed first-order Raman peaks, in agreement with previous literature results. A thorough analysis of the second-order Raman bands, as observed in both basal and edge plane configurations, provides new information and allows a precise assignment of these spectral structures. In particular, we have observed and assigned Raman active modes of the M point of the Brillouin zone previously predicted by ab initio calculations but never previously measured.

Using a second-order bistatic cross-section of the ocean surface for bistatic shipborne HFSWR

ABSTRACTThe second-order radar cross section (RCS) of ocean surface is analytically derived for the case in which the radar transmitter is located inland and the receiving antenna is mounted on a shipborne platform. With our previously derived first-order RCS result, the total RCS of ocean surface is simulated for a variety of radar operating parameters and sea states. According to simulation results, it is seen that the relative effect on the second-order spectra due to the platform motion is much smaller than that on the first-order. For the conditions of the radar working with a high operating frequency or a high sea state, the increase of the second-order spectral energy may contaminate the first-order component severely. The obtained results may be useful for setting appropriate limits on the use of radar operating parameters or the bistatic site geometries, from which condition the ocean surface parameters can be effectively extracted from the radar data.

Damping Identification with Acceleration Measurements Based on Sensitivity Enhancement Method

The damping is important for forward and inverse structural dynamic analysis, and damping identification has become a hot issue in structural health monitoring recently. The dynamic responses of the structure can be measured in practice, and the structural parameter usually can be identified by inverse response sensitivity analysis. To reduce the measurement noise effect and enhance the effectiveness of the response sensitivity method, an enhanced sensitivity analysis method was proposed to identify the structural damping based on the Principal Component Analysis (PCA) method. The measured acceleration responses were analyzed by PCA method, and the updated analytical responses and the response sensitivities were projected into the subspace determined by the first‐order principal component. The projection equations were adopted to identify the parameters of damping model. The proposed damping identification method was numerically validated with a planar truss structure at first, and then the experimental study was conducted with a steel planar frame structure. It shows that the proposed method is effective in identifying the parameters of damping model with better accuracy compared with the conventional acceleration response sensitivity method, and it is also robust to the sensor placement and measurement noise.

“Ride” vs. “/baI/”: Examining networks that support word retrieval through semantic vs. phonemic cueing

“Ride” vs. “/baI/”: Examining networks that support word retrieval through semantic vs. phonemic cueing

More superimposition for contrast-modulated than luminance-modulated stimuli during binocular rivalry

Luminance-modulated noise (LM) and contrast-modulated noise (CM) gratings were presented with interocularly correlated, uncorrelated and anti-correlated binary noise to investigate their contributions to mixed percepts, specifically piecemeal and superimposition, during binocular rivalry. Stimuli were sine-wave gratings of 2 c/deg presented within 2 deg circular apertures. The LM stimulus contrast was 0.1 and the CM stimulus modulation depth was 1.0, equating to approximately 5 and 7 times detection threshold, respectively. Twelve 45 s trials, per noise configuration, were carried out. Fifteen participants with normal vision indicated via button presses whether an exclusive, piecemeal or superimposed percept was seen. For all noise conditions LM stimuli generated more exclusive visibility, and lower proportions of superimposition. CM stimuli led to greater proportions and longer periods of superimposition. For both stimulus types, correlated interocular noise generated more superimposition than did anti- or uncorrelated interocular noise. No significant effect of stimulus type (LM vs CM) or noise configuration (correlated, uncorrelated, anti-correlated) on piecemeal perception was found. Exclusive visibility was greater in proportion, and perceptual changes more numerous, during binocular rivalry for CM stimuli when interocular noise was not correlated. This suggests that mutual inhibition, initiated by non-correlated noise CM gratings, occurs between neurons processing luminance noise (first-order component), as well as those processing gratings (second-order component). Therefore, first- and second-order components can contribute to overall binocular rivalry responses. We suggest the addition of a new well to the current energy landscape model for binocular rivalry that takes superimposition into account.

Evaluation of brivaracetam efficacy as monotherapy in adult patients with focal seizures

Brivaracetam is a selective, high-affinity ligand for synaptic vesicle protein 2A, recently approved as adjunctive therapy in the treatment of focal (partial-onset) seizures in patients 16 years of age and older with epilepsy. The goal of the present analysis was to determine if the dose-response of brivaracetam as monotherapy would fall within the range associated with brivaracetam efficacy as adjunctive therapy.An existing brivaracetam population pharmacokinetic model consisting of first-order absorption, single compartment distribution, and first-order elimination components was extended by estimating the clearance changes due to co-administration of 12 widely prescribed AEDs. Data for the population pharmacokinetic analysis originated from three Phase III add-on trials and two terminated Phase III monotherapy trials.An existing population model of daily seizure rate versus brivaracetam daily average concentration was applied to the data from the three add-on trials. Simulations allowed the assessment of the combined impact of covariate effects on both the pharmacokinetics and the pharmacodynamics of brivaracetam, and indicated that in the absence of other AEDs, only marginal changes in the overall dose-response relationship would be expected. This suggests that brivaracetam can be used as monotherapy without dose modifications.