A cascade MPC control structure for PMSM with speed ripple minimization

This paper addresses the problem of reducing the impact of periodic disturbances arising from the current sensor offset error on the speed control of a PMSM. The new results are based on a cascade model predictive control scheme with embedded disturbance model, where the per unit model is utilized to improve the numerical condition of the scheme. Results from an experimental application are given to support the design

Determination of pion distribution amplitudes from the electromagnetic form factor with the data-driven dispersion relation

We study the pion electromagnetic form factor in the modulus squared dispersion relation, and do the model independent extraction of the most important nonperturbative parameters in pion light-cone distribution amplitude. The motivation of this work is the recent measurement of timelike form factor in the resonant regions, which makes up the piece lacking solid QCD-based calculation. With the perturbative QCD calculation up to next-to-leading-order QCD corrections and twist four level of meson distribution amplitudes, we obtain the chiral mass of pion meson as $m_0^\pi(1 \, {\rm GeV}) = 1.31^{+0.27}_{-0.30} \, {\rm GeV}$. More accuracy measurement of the timelike form factor are desirable to help us to determine the lowest gegenbauer moments in pion distribution amplitudes with the data-driven dispersion relation method developed in this work.Comment: 9pages, 6 figures, 1 tabl

The optimal displacement of immiscible two-phase fluids in a pore doublet

The displacement of multiphase fluid flow in a pore doublet is a fundamental problem, and is also of importance in understanding of the transport mechanisms of multiphase flows in the porous media. During the displacement of immiscible two-phase fluids in the pore doublet, the transport process is not only influenced by the capillary and viscous forces, but also affected by the channel geometry. In this paper, we first present a mathematical model to describe the two-phase fluid displacement in the pore doublet where the effects of capillary force, viscous force and the geometric structure are included. Then we derive an analytical solution of the model for the first time, and find that the displacement process is dominated by the capillary number, the viscosity ratio and the radius ratio. Furthermore, we define the optimal displacement that the wetting fluids in two daughter channels break through the branches simultaneously (both of them have the same breakthrough time), and also obtain the critical capillary number corresponding to the optimal displacement, which is related to the radius ratio of two daughter channels and viscosity ratio of two immiscible fluids. Finally, it is worthy noting that the present analytical results on the displacement in the pore doublet can be used to explain and understand the phenomenon of preferential imbibition or preferential flow in porous media

Seeking for reliable double-hybrid density functionals without fitting parameters: The PBE0-2 functional

Without the use of any empirical fitting to experimental or high-level ab initio data, we present a double-hybrid density functional approximation for the exchange-correlation energy, combining the exact Hartree-Fock exchange and second-order Moller-Plesset (MP2) correlation with the Perdew-Burke-Ernzerhof (PBE) functional. This functional, denoted as PBE0-2, is shown to be accurate for a wide range of applications, when compared with other functionals and the ab initio MP2 method. The qualitative failures of conventional density functional approximations, such as self-interaction error and noncovalent interaction error, are significantly reduced by PBE0-2.Comment: accepted for publication in Chem. Phys. Lett., 5 pages, 5 figures, 1 table, supplementary material not include

Forecasting stock market volatility on Bursa Malaysia Plantation Index

This research applies the Bursa Malaysia Plantation Index to examine the most suitable forecasting model. The Plantation Index is studied because Malaysia is the world second largest in oil palm producer. Additionally, volatile crude palm oil price has resulted in the Plantation Index becoming more volatile as earnings of plantation companies depend heavily on crude palm oil prices. The forecasting techniques applied were random walk, moving average, simple regression and historical mean. The error in forecasting was measured by symmetric and asymmetric error statistics. The most suitable volatility forecasting technique for Bursa Malaysia Plantation Index was simple regression technique. The findings to a very large extent indicate that although there are different sophisticated forecasting technique, investor, managers and regulators could employ the less costly simple regression method to forecast oil palm related stocks and make their wise decision in investment, management and regulation in oil palm industry

Predictive Repetitive Control Based on Frequency Decomposition

Abstract-This paper develops a predictive repetitive control algorithm based on frequency decomposition. In particular,, the periodic reference signal is first represented using a frequency sampling filter model and then the coefficients of the model are analyzed to determine its dominant frequency components. Using the internal model control principle, the dominant frequency components are embedded in model used to obtain the predictive repetitive control algorithm such that the periodic reference is followed with zero steadystate error. The design framework here is based on predictive control using Laguerre functions and hence plant operational constraints are naturally incorporated in the design and its implementation. keyword Periodic set-point signal, periodic disturbance, predictive control, constrained control, optimization

Quantum electric-dipole liquid on a triangular lattice

Geometric frustrations and quantum mechanical fluctuations may prohibit the formation of long-range ordering even at the lowest temperature, and therefore liquid-like ground states could be expected. A good example is the quantum spin liquid in frustrated magnets that represents an exotic phase of matter and is attracting enormous interests. Geometric frustrations and quantum fluctuations can happen beyond magnetic systems. Here we propose that quantum electric-dipole liquids, analogs to quantum spin liquids, could emerge in frustrated dielectrics where antiferroelectrically coupled small electric dipoles reside on a triangular lattice. The quantum paraelectric hexaferrite BaFe12O19, in which small electric dipoles originated from the off-center displacement of Fe3+ in the FeO5 bipyramids constitute a two-dimensional triangular lattice, represents a promising candidate to generate the anticipated electric-dipole liquid. We present a series of experimental evidences, including dielectric permittivity, heat capacity, and thermal conductivity measured down to 66 mK, to reveal the existence of a nontrivial ground state in BaFe12O19, characterized by itinerant low-energy excitations with a small gap, to which we interpret as an exotic liquid-like quantum phase. The quantum electric-dipole liquids in frustrated dielectrics open up a fresh playground for fundamental physics and may find applications in quantum information and computation as well.Comment: 13 pages, 6 figure

Charmless two-body BB meson decays in perturbative QCD factorization approach

The perturbative QCD (PQCD) approach based on $k_T$ factorization has made a great achievement for the QCD calculation of the hadronic B decays. Regulating the endpoint divergence by the transverse momentum of quarks in the propagators, one can do the perturbation calculation for kinds of diagrams including the annihilation type diagrams. In this paper, we review the current status of PQCD factorization calculation of two-body charmless $B\to PP, PV, VV$ decays up to the next-to-leading order (NLO) QCD corrections. two new power suppressed terms in decaying amplitudes are also taken into account. By using the universal input (non-perturbative) parameters, we collected the branching ratios and ${\bf CP}$ asymmetry parameters for all the charmless two body $B$ decays, calculated in the PQCD approach up to the NLO, including some power suppressed terms in decaying amplitudes. The results are compared with the ones from QCD factorization approach, soft-collinear effective theory approach and the current experimental measurements. For most considered B meson decays, the PQCD results for branching ratios agree well with other approaches and the experimental data. The PQCD predictions for the ${\bf CP}$ asymmetry parameters for many of the decay channels do not agree with other approaches, but have a better agreement with the experimental data. The longstanding $K \pi$ puzzle about the pattern of the direct CP asymmetries of the penguin-dominated $B \to K \pi$ decays can be understood after the inclusion of the NLO contributions in PQCD. The NLO corrections and power suppressed terms play an important role in the color suppressed and pure annihilation type $B$ decay modes. These rare decays are more sensitive to different types of corrections, providing opportunity to examine the factorization approach with the more precise experimental measurements.Comment: 51 pages, 4 figures, 11 tables, references added, typos remove

Enhancing Project Integration Using Cloud-based Building Information Modelling: A Conceptual Model

Construction industry is a project-based endeavour in which its success heavily rests upon the intertwined collaborative gumptions rendered by each of the project team members throughout the project lifecycle. Optimisation of productivity have long been recognised as one of the toughest challenges faced in construction –frequently postulated by many as one of the most inefficient industries worldwide. Consequently, Building Information Modelling (BIM) has been introduced to ameliorate this shortfall, riding on its ability to better integrate the entire project team via a common platform, utilising Information and Communication Technology (ICT) as well as Internet of Things (IoT), or more specifically, through the ‘Cloud’ as is commonly coined. Nevertheless, its ability has yet to be fully utilised owing to the lack of awareness among construction stakeholders with regards to the array of benefits offered by this Cloud-based technology. In view of this, the authors aim to unmask the capabilities of Cloud-based BIM in enhancing project integration. To this end, a model has been conceptualised by reviewing extant literatures, with the concept of 4C’s (Communication, Coordination, Cooperation, Collaboration) adopted as its underlying theory. This conceptual model can be expected to impact the digitisation of project management, thereby optimising productivity and enhancing projects’ overall efficiency. This study also lays the groundwork for the better understanding and the future development of Cloud-based BIM and team integration in managing construction projects, both locally and internationally