Modelling of a Stochastic Spatiotemporal Variable in Transport Domain

In this article, building on our previous work, we engage in spatiotemporal modelling of transport demand in the Montreal metropolitan area over the period of six years. We employ classical machine learning and regression models, which predict bike-sharing demand in the form of daily cumulative sums of bike trips for each considered docking station. Hourly estimates of demand are then determined by considering the statistical distribution of demand across individual hours of an average day. In order to capture seasonal and other regular variation of demand, longer-term distribution characteristics of bike trips, such as their average number falling on each day of the week, month of the year, etc., were also used as input attributes. We initially conjectured that weather would be an important source of irregular variation in bike-sharing demand, and subsequently included several available meteorological variables in our models. We validated our models by Hold-Out and 10-Fold Cross-Validation, with encouraging results.

Alone at work: Isolation, competition and co-dependency in flexibilised retail

Previous studies of flexibilisation through employer-controlled flexible scheduling and off-site isolated work have shown how such practices have detrimental effects on workers’ wellbeing. This qualitative study, set in Swedish retail, adds to previous findings by showing how flexible scheduling practices that include irregular variation of work hours and headcount have consequences also for worker interaction in the workplace. Even on-site work can be experienced as isolating if workers are ‘spread too thin’ in efforts to reduce labour costs. Set in two different retail settings, the study demonstrates and discusses how inter-employee competition and co-dependency are created, respectively. The authors also discuss how the flexibilisation described in this study reduced possibilities for face-to-face meetings and communication between co-workers, between workers and managers, and between workers and union representatives. Finally, it is discussed how the kind of flexibilisation described in this study coincides with defeatism and barriers to collective voice as well as action.

Kinetics of Forward Extraction of V(V) in V(V)-NO3- (H+, Na+)-TOA-Kerosene System using Single Drop Technique

The titled system has been investigated using a single drop technique and flux (F) method of data treatment. In calculating fluxes, the time for drop formation and coalescence (?t = 0.75 s) is considered. At lower concentration region of vanadium, V(V), the rate of V(V) transfer is directly proportional to its concentration. With the increase in [V(V)], slowly extractable V(V) species are formed gradually resulting in decrease in rate. Rate is directly proportional to the square root of [TOA]. It is reported that the most favorable extractable V(V) species exists in maximum amount at pH 2, and so, log F vs pH plots show a maximum at pH~2. The flux of V(V) transfer in most cases is found to be decreased with increasing [NO3-]. Reaction orders with respect to [V(V)], pH and [NO3-] have been attempted to be estimated, but in vein due to non-linearity of plots in most cases. Activation energies for the present system is ~ -12 kJ/mol. This is unexpected but explained. Due to irregular variation of the composition of extractable species with [V(V)], [H+]; as well as temperature; it is not possible to elucidate the value of rate constant (k) and mechanism in simple way.

Stress-induced surface characterization by wavelet and fractal analysis in Ga-doped ZnO thin films

ABSTRACTThe Ga-doped ZnO (GZO) were deposited by magnetron reactive sputtering on glass substrates at room temperature with different deposited times to obtain various thickness. The root-mean-square (RMS) roughness obtained from the atomic force microscopy (AFM) images is observed to shift linearly with the deposited time, the fractal geometry and multi-resolution signal decomposition (MRSD) based on wavelet transform were applied on the surface profiles and the results does not synchronously changes as the thickness, which is related to the profile’s frequency. The calculated compressive in-plane stress of highly c-axis oriented GZO films also shows an irregular variation as the increase of film thickness, what’s more, the in-plane stress and fractal dimension exhibit a polynomial relationship and the two parameters can be used for describing the surface morphology.

Torque ripple analysis for IPM AC motors

Purpose – The purpose of this paper is to investigate a new cause of torque ripple in interior permanent magnet (IPM) alternating current (AC) motors, which is common but has hardly been studied. The paper also proposes a new method to suppress the total torque ripple. Design/methodology/approach – Besides the well-known cogging torque and mutual torque ripple, a new ripple which exists in the reluctance torque is found. It is verified with both analytical model and finite element analysis. Also, a novel method is proposed to reduce the reluctance torque ripple, with experimental validation. Findings – It is usually said that the winding inductances of an IPM AC motor vary sinusoidally with the rotor position, thus, the d-axis and q-axis inductances are constant, whilst the reluctance torque is smooth. However, in most practical motors, the inductances vary irregularly, causing a significant ripple in the reluctance torque. Moreover, in machine design, it is always desirable to suppress the cogging torque as much as possible. However, in this paper, it is proved that the cogging torque can remain and be used to cancel the reluctance torque ripple. Originality/value – Torque ripple in the IPM AC motors is usually reduced by suppressing the cogging torque and making both back electromotive forces and currents sinusoidal. However, this paper reveals the new cause of the torque ripple due to the irregular variation of winding inductances. Moreover, the paper gives a new method to cancel the reluctance torque ripple with the cogging torque.

A COMPARABLE STUDY ON STRUCTURAL AND OPTICAL PROPERTIES OF Cu2ZnSnS4 AND Cu2ZnSnSe4 NANOCRYSTALLINES

In this study, single-kesterite-phase Cu 2 ZnSnS 4 (CZTS) and Cu 2 ZnSnSe 4 (CZTSe) nanocrystallines have been synthesized by a simple solvothermal route. Scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible (UV-vis) absorbance and Raman scattering spectroscopy were used to characterize the optical and micro-structure properties of the as-synthesized samples. The bandgap of CZTS could be tuned in a large range by incorporating a few Se atoms. Both the CZTS and CZTSe exhibited the similar temperature dependence of the Raman "A" modes, including a monotonic redshift in peak position and an irregular variation in peak linewidth. Such a behavior might be due to the cumulative effect of thermal expansion and small crystalline sizes.