Divergent evolution of terrestrial locomotor abilities in extant Crocodylia

Extant Crocodylia are exceptional because they employ almost the full range of quadrupedal footfall patterns (“gaits”) used by mammals; including asymmetrical gaits such as galloping and bounding. Perhaps this capacity evolved in stem Crocodylomorpha, during the Triassic when taxa were smaller, terrestrial, and long-legged. However, confusion about which Crocodylia use asymmetrical gaits and why persists, impeding reconstructions of locomotor evolution. Our experimental gait analysis of locomotor kinematics across 42 individuals from 15 species of Crocodylia obtained 184 data points for a wide velocity range (0.15–4.35 ms−1). Our results suggest either that asymmetrical gaits are ancestral for Crocodylia and lost in the alligator lineage, or that asymmetrical gaits evolved within Crocodylia at the base of the crocodile line. Regardless, we recorded usage of asymmetrical gaits in 7 species of Crocodyloidea (crocodiles); including novel documentation of these behaviours in 5 species (3 critically endangered). Larger Crocodylia use relatively less extreme gait kinematics consistent with steeply decreasing athletic ability with size. We found differences between asymmetrical and symmetrical gaits in Crocodylia: asymmetrical gaits involved greater size-normalized stride frequencies and smaller duty factors (relative ground contact times), consistent with increased mechanical demands. Remarkably, these gaits did not differ in maximal velocities obtained: whether in Alligatoroidea or Crocodyloidea, trotting or bounding achieved similar velocities, revealing that the alligator lineage is capable of hitherto unappreciated extreme locomotor performance despite a lack of asymmetrical gait usage. Hence asymmetrical gaits have benefits other than velocity capacity that explain their prevalence in Crocodyloidea and absence in Alligatoroidea—and their broader evolution

Application of pseudo-derivative feedback (PDF) algorithm in ship contol

SIGLEAvailable from British Library Document Supply Centre- DSC:DX93149 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Risk-averse probabilistic framework for scheduling of virtual power plants considering demand response and uncertainties

In this paper, a risk-based stochastic framework is presented for short-term energy and reserve scheduling of a virtual power plant (VPP) considering demand response (DR) participation. The VPP comprises several dispatchable generation units, battery energy storage systems (BESSs), wind power units, and flexible loads. The proposed scheduling framework is formulated as a risk-constrained stochastic program to maximize the VPP's profit considering uncertainties of loads, wind energy and electricity prices as well as N-1 contingencies. The proposed model considers both supply and demand-sides capability for providing and deploying reserves in order to optimize the use of resources while satisfying N-1 security and other constraints. Moreover, the effect of risk-aversion on decision making of the VPP in the offering/bidding power and required reserve services is investigated by implementing conditional value-at-risk (CVaR) in the optimization model. The proposed scheme is implemented on a test VPP and the energy and reserve scheduling with and without DR participants is addressed in detail through a numerical study. Moreover, the effects of the operator's risk-averse behavior on the VPP energy and reserve management and its security indices are investigated

Flexible stochastic scheduling of microgrids with islanding operations complemented by optimal offering strategies

This paper presents a stochastic framework for optimal scheduling of microgrids (MGs) considering unscheduled islanding events, initiated by disturbances in the main grid. This scheduling approach considers different uncertainties and determines the day-ahead schedule of the resources considering emergency operations. The proposed strategy attempts to effectively manage demand and supply side resources to mitigate the effects of uncertainties in both normal and emergency operations. The prevailing uncertainties associated with renewable power generations, demand and electricity prices as well as uncertainties of islanding duration are addressed in the presented framework. The objective is to maximize the expected profit of the operator over the scheduling horizon, while restricting the risk of mandatory load shedding imposed by uncertain parameters within an acceptable level. According to the proposed strategy, an efficient probabilistic index is obtained from generation reserve margin (GRM) in islanded mode, and applied to create a proper offering price signal to coordinate responsive loads with renewable generations providing more reliable operations. The effectiveness of the proposed strategy in terms of economy and reliability is investigated via a comparison with other methods. Extensive numerical results illustrate that the proposed offering price strategy can improve the MG's operation from both reliability and economic aspects

Zonal rate model for axial and radial flow membrane chromatography. Part I: Knowledge transfer across operating conditions and scales

The zonal rate model (ZRM) has previously been applied for analyzing the performance of axial flow membrane chromatography capsules by independently determining the impacts of flow and binding related non-idealities on measured breakthrough curves. In the present study, the ZRM is extended to radial flow configurations, which are commonly used at larger scales. The axial flow XT5 capsule and the radial flow XT140 capsule from Pall are rigorously analyzed under binding and non-binding conditions with bovine serum albumin (BSA) as test molecule. The binding data of this molecule is much better reproduced by the spreading model, which hypothesizes different binding orientations, than by the well-known Langmuir model. Moreover, a revised cleaning protocol with NaCl instead of NaOH and minimizing the storage time has been identified as most critical for quantitatively reproducing the measured breakthrough curves. The internal geometry of both capsules is visualized by magnetic resonance imaging (MRI). The flow in the external hold-up volumes of the XT140 capsule was found to be more homogeneous as in the previously studied XT5 capsule. An attempt for model-based scale-up was apparently impeded by irregular pleat structures in the used XT140 capsule, which might lead to local variations in the linear velocity through the membrane stack. However, the presented approach is universal and can be applied to different capsules. The ZRM is shown to potentially help save valuable material and time, as the experiments required for model calibration are much cheaper than the predicted large-scale experiment at binding conditions. Biotechnol. Bioeng. 2013; 110: 1129–1141. © 2012 Wiley Periodicals, Inc

Short-term reliability and economic evaluation of resilient microgrids under incentive-based demand response programs

In this paper, a flexibility oriented stochastic scheduling framework is presented to evaluate short-term reliability and economic of islanded microgrids (MGs) under different incentive-based DR (IBDR) programs. A multi-period islanding constraint is considered to prepare the MG for a resilient response once a disturbance occurs in the main grid. Also, a multi-segment optimal power flow (OPF) approach is used to model the IBDR actions and reserve resources. Moreover, uncertainties associated with electricity prices, loads, renewable generation, calls for reserve as well as uncertainties of islanding duration of the MG are considered. The ultimate goal of the MG operator is to maximize its expected profit under a certain level of security and reliability in conjunction with the minimization of energy procurement costs of customers. The MG's economy and reliability indices are studied considering normal operation and resilient condition based on appliances characteristics, customers’ and operator's behaviors. The proposed model can effectively manage MGs operation in both normal and resilient conditions in order to improve economic and reliability indices. Numerical results demonstrate that by implementing IBDR, in cases of normal and resilient operation, the expected profit of the MG operator increases about 4% and 2.7% and reliability indicator improved 60% and 56%, respectively

A versatile system for neuromuscular stimulation and recording in the mouse model using a lightweight magnetically coupled headmount

Neural stimulation and recording in rodents are common methods to better understand the nervous system and improve the quality of life of individuals who are suffering from neurological disorders (e.g., epilepsy), as well as for permanent reduction of chronic pain in patients with neuropathic pain and spinal-cord injury. This method requires a neural interface (e.g., a headmount) to couple the implanted neural device with instrumentation system. The size and the total weight of such headmounts should be designed in a way to minimize its effect on the movement of the animal. This is a crucial factor in gait, kinematic, and behavioral neuroscience studies of freely moving mice. Here we introduce a lightweight ‘snap-in’ electro-magnetic headmount that is extremely small, and uses strong neodymium magnetics to enable a reliable connection without sacrificing the lightweight of the device. Additionally, the headmount requires minimal surgical intervention during the implantation, resulting in minimal tissue damage. The device has demonstrated itself to be robust, and successfully provided direct electrical stimulation of nerve and electrical muscle stimulation and recording, as well as powering implanted LEDs for optogenetic use scenarios