Evolution in inter-firm governance along the transport biofuel value chain in maritime Silk Road countries

We investigate how value chain governance can evolve in the transport biofuel sector beyond logistics and operations optimization, drawing on cases of eighteen manufacturers in four Belt and Road countries. We find that key motivations for vertical integration include control of strategic factors such as security of supply and gaining access to the retail market, subject to inter-institutional and intra-organizational barriers. We contribute to a theory of governance mode selection by suggesting plural governance mode offers a key strategic choice under institutional constraints. In BRI countries, plural mode could be less disruptive when integrating value chains.ESRC-Cambridge Commonwealth Trust-Dorothy Hodgkin Postgraduate Awar

Eye movement pattern in face recognition is associated with cognitive decline in the elderly

Conference Theme: Mind, Technology, and SocietyThe present study investigated the relationship between eye movement pattern in face recognition and cognitive perform-ance during natural aging through modeling and comparing eye movement of young (18-24 years) and older (65-81 years) adults using Hidden Markov Model (HMM) based approach. Young adults recognized faces better than older adults, particularly when measured by the false alarm rate. Older adults’ recognition performance, on the other hand, correlated with their cognitive status assessed by the Montreal Cognitive Assessment (MoCA). Eye movement analysis with HMM revealed two different strategies, namely “analytic” and “holistic”. Participants using the analytic strategy had better recognition performance (particularly in the false alarm rate) than those using the holistic strategy. Significantly more young adults adopted the analytic strategy; whereas more older adults adopted the holistic strategy. Interestingly, older adults with lower cognitive status were associated with higher likelihood of using the holistic strategy. These results suggest an association between holistic eye movement patterns and cognitive decline in the elderly.postprin

Modeling of subharmonics and chaos in DC motor drives

In this paper, the nonlinear dynamics of both voltage-mode and current-mode controlled dc motor drive systems are presented. The investigation is based on the derivation of the discrete mappings that describe their system subharmonics and chaos in the continuous conduction mode of operation. It illustrates that different bifurcation diagrams can be obtained by using different modes of control while varying the same system parameters. A unified modeling approach for the period-1 and hence the period-p orbits as well as their stability analysis during both voltage-mode and current-mode of control is proposed and verified.published_or_final_versio

Dynamic bifurcation in dc drives

Dynamic bifurcation as well as chaotic behavior in a fixed-frequency current-mode controlled dc chopper-fed dc motor drive system is presented. The key is to derive an iterative map that describes the nonlinear dynamics of the system operating in the continuous conduction mode. It illustrates that different bifurcation diagrams can be obtained by varying different system parameters. Analytical modeling of period-1 and hence period-p orbits as well as their stability analysis using the characteristic multipliers are also presented. Hence, those stable ranges of various system parameters can be determined. Moreover, chaotic behavior is quantified by evaluating the Lyapunov exponents. The proposed approach is so general that it can readily be applied to other current-mode dc drives.published_or_final_versio

Analysis of chaos in current-mode-controlled dc drive systems

In this paper, chaotic behavior in current-mode-controlled dc drive systems has been analyzed. The key is to derive an iterative map that describes the nonlinear system dynamics. Analytical modeling of fundamental and subharmonic oscillations as well as their stability analysis are presented. The results show that the current-mode-controlled dc drive systems generally exhibit chaotic behavior. To avoid the occurrence of chaos, the stable ranges of various system parameters are determined. Both computer simulation and experimental measurement are given to verify the theoretical analysis.published_or_final_versio

Magnetic and luminescent properties of multifunctional GdF₃: Eu³⁺ nanoparticles

Author name used in this publication: H. L. W. Chan2009-2010 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Chaotic behavior in a simple DC drive

Remarkably complex behavior, namely chaotic behavior, in a simple dc chopper-fed dc motor drive system has been investigated. An iterative map that describes the nonlinear dynamics of the system operating in the continuous conduction mode is derived. It shows that different bifurcation diagrams can be obtained by varying different system parameters, and the system exhibits not only a typical period-doubling route to chaos but also the period-3 window. Analytical modeling of period-1 and hence period-p orbits as well as their stability analysis using the characteristic multipliers are presented. Thus, those stable ranges of various system parameters can be formulated, and hence the chaotic ranges can be determined. The theoretical results are verified by using both PSpice simulation and experimental measurement.published_or_final_versio

Breathers and 'black' rogue waves of coupled nonlinear Schrödinger equations with dispersion and nonlinearity of opposite signs

Breathers and rogue waves of special coupled nonlinear Schrödinger systems (the Manakov equations) are studied analytically. These systems model the orthogonal polarization modes in an optical fiber with randomly varying birefringence. Studies earlier in the literature had shown that rogue waves can occur in these Manakov systems with dispersion and nonlinearity of opposite signs, and that the criterion for the existence of rogue waves correlates closely with the onset of modulation instability. In the present work the Hirota bilinear transform is employed to calculate the breathers (pulsating modes), and rogue waves are obtained as a long wave limit of such breathers. In terms of wave profiles, a ‘black’ rogue wave (intensity dropping to zero) and the transition to a four-petal configuration are elucidated analytically. Sufficiently strong modulation instabilities of the background may overwhelm or mask the development of the rogue waves, and such thresholds are correlated to actual physical properties of optical fibers. Numerical simulations on the evolution of breathers are performed to verify the prediction of the analytical formulations.postprin

Subharmonics and chaos in switched reluctance motor drives

In this paper, the investigation of the nonlinear dynamics of an adjustable-speed switched reluctance motor (SRM) drive with voltage pulse width modulation (PWM) regulation is carried out. Nonlinear iterative mappings based on both nonlinear and approximately linear flux linkage models are derived, hence the corresponding subharmonic and chaotic behaviors are analyzed. Although both flux linkage models can produce similar results, the nonlinear one offers the merit of accuracy but with the sacrifice of computational time. Moreover, the bifurcation diagrams show that the system generally exhibits a period-doubling route to chaos.published_or_final_versio

Subharmonics and chaos in switched reluctance motor drives

In this paper, the investigation of the nonlinear dynamics of an adjustable speed switched reluctance motor (SRM) drive with voltage PWM regulation is carried out. The corresponding bifurcation diagrams and chaotic Poincare sections are presented. It shows that the system generally exhibits a period-doubling route to chaos.published_or_final_versio