Pattern Generation for Walking on Slippery Terrains

In this paper, we extend state of the art Model Predictive Control (MPC) approaches to generate safe bipedal walking on slippery surfaces. In this setting, we formulate walking as a trade off between realizing a desired walking velocity and preserving robust foot-ground contact. Exploiting this formulation inside MPC, we show that safe walking on various flat terrains can be achieved by compromising three main attributes, i. e. walking velocity tracking, the Zero Moment Point (ZMP) modulation, and the Required Coefficient of Friction (RCoF) regulation. Simulation results show that increasing the walking velocity increases the possibility of slippage, while reducing the slippage possibility conflicts with reducing the tip-over possibility of the contact and vice versa.Comment: 6 pages, 7 figure

Waste and the Governance of Private and Public Property

Common law waste doctrine is often overlooked as antiquated and irrelevant. At best, waste doctrine is occasionally examined as a lens through which to evaluate evolutions in modern property theory. We argue here that waste doctrine is more than just a historical artifact. Rather, the principle embedded in waste doctrine underpins a great deal of property law generally, both common law and statutory, as well as the law governing oil and gas, water, and public trust resources. Seen for what it is, waste doctrine provides a fresh perspective on property, natural resources, and environmental law. In this Article, we excavate the old waste cases in multiple fields of property and natural resources law to make novel connections across these fields and demonstrate the doctrine\u27s continuing relevance for contemporary lawyers, legal theorists, and environmental advocates. The Article is unique in its articulation of a universal waste principle and its examination of how this principle facilitates communication and cooperative self-governance by and among owners of common property. It suggests that underenforcement of civil and administrative waste law in the context of common pool natural resources contributes to failures in modern law to respond to pressing environmental challenges

Acute influence of cigarette smoke in platelets, catecholamines and neurophysins in the normal conditions of daily life

Cigarette smoking is firmly linked to the occurrence of acute coronary events. In twenty-two healthy volunteers in normal conditions of daily life we studied the acute influence of smoking on the following parameters: beta-thromboglobulin, thromboxane B2, epinephrine, norepinephrine, estrogen-stimulated neurophysin, and nicotine-stimulated-neurophysin. Our results show that in our population and following our protocol, smoking did not induce platelet activation, thromboxane formation, catecholamine release or estrogen-stimulated-neurophysin secretion. However, smoking did provoke a significant increase of nicotine-stimulated-neurophysin (p<0.05) which reflects vasopressin increase and which might explain the high incidence of ischaemic accidents in cigarette smoking via the vasoactive properties of vasopressi

R134a And Its Low GWP Substitutes R1234yf And R1234ze(E) Flow Boiling Inside A 4mm Horizontal Smooth Tube

The substitution of HFC134a with low GWP refrigerants is one of the most important challenge for refrigeration and air conditioning. The possible substitutes include natural refrigerants, such as HC600 (Butane) and HC600a (Isobutane), and also synthetic refrigerants, such as HFO1234yf and HFO1234ze(E). The HC refrigerants exhibit very low GWP, 3 and 4 HC600a and HC600 respectively, good thermodynamic and transport properties, and pressure and volumetric performance very similar to HFC134a. The major drawback of HC refrigerants is their high flammability, being classified in class A3 according to ASHRAE classification. Also the HFO refrigerants present a mild flammability, being classified in class A2L. In fact, it is very difficult to found low GWP substitutes for traditional HFC refrigerants with no flammability, as a weak chemical stability and / or a big chemical reactivity are presuppositions for low GWP. Both HFO1234yf and HFO1234ze(E) seem to be very promising as substitute for HFC134a, showing a GWP lower than 1 together with pressure and volumetric properties closely near to those of HFC134a. This paper presents the comparative analysis of HFC134a HFO1234yf and HFO1234ze(E) during saturated flow boiling inside a 4 mm horizontal smooth tube: the effects of heat flux, refrigerant mass flux, mean vapour quality and saturation temperature (pressure) are investigated separately to rank the superposed effects of different heat transfer regimes (nucleate boiling or/and forced convection boiling). The experimental tests were carried out at three different saturation temperatures (10, 15, and 20 °C) at increasing vapour quality up to incipient dryout to evaluate the specific contribution of heat flux, refrigerant mass flux, mean vapour quality, and saturation temperature (pressure). The refrigerant mass flux ranges from 200 to 600 kg m-2s-1 and the heat flux from 15 to 30 kW m-2. The experimental measurements were reported in term of boiling heat transfer coefficients and frictional pressure drops. Heat transfer coefficients have a positive slope versus vapour quality and the slope increases with refrigerant mass flux and decreases with heat flux. Saturation temperature (pressure), refrigerant mass flux and mean vapour quality have a remarkable impact on the frictional pressure drop, whereas the effect of heat flux appears marginal or negligible. Convective boiling seems to be the prevailing heat transfer regime in present experimental tests. HFO1234ze(E) and HFO1234yf exhibit heat transfer coefficients and pressure drops similar to HFC134a. Present heat transfer coefficients and pressure drops were also compared against different correlations for refrigerant boiling inside tube. The universal correlation proposed by Kim and Mudawar (2014) and the Friedel (1979) correlation show the best performance in predicting heat transfer coefficients and pressure drops, respectively