Magnitude Of Slippage Research Articles

Modeling and Analysis of Inter-Panel Slipping for the Design of Rolled Gossamer Arrays

Abstract Many deployable satellite systems benefit from having low mass and high surface area, which has led to the proliferation of gossamer structures in space-based applications. Gossamer structures are characterized by lightweight, low-stiffness membranes, which can flex and roll to compactly stow. An effect of rolling a gossamer structure is that there is a tangential separation along adjacent panels as they roll, resulting in relative motion between panels. To aid designers in predicting and accommodating this motion, a method for modeling the slippage between adjacent panels that occurs while rolling is presented. This analytical slippage model and algorithm is a function of (1) the number of panels, (2) the thickness of each panel, (3) the length of each panel, and (4) the minimum bend radius of the material. It is shown that the thickness and length have a positive correlation with increased slippage, whereas the number of panels and minimum bend radius have a negative correlation with increased slippage. This model allows designers to predict both the magnitude of slippage that occurs where panels meet, as well as the relative range of slippage that occurs within the whole pattern. With these predictions, an appropriate strategy can be selected for accommodating this motion.

Asymmetric ‘Newmark' sliding caused by motions containing severe ‘directivity' and ‘fling' pulses

Sliding of a rigid mass supported on an inclined, seismically shaking plane serves as a conceptual and computational model for a variety of problems in geotechnical earthquake engineering. A series of parametric analyses are presented in the paper using as excitation numerous near-fault-recorded severe ground motions and idealised wavelets, bearing the effects of ‘forward-directivity' and ‘fling-step'. Using as key parameters the angle β of the sloping plane (mimicking the sliding surface), as well as the frequency content, intensity, nature and polarity of the excitation, the paper aims at developing a deeper insight into the mechanics of the asymmetric sliding process and the role of key parameters of the excitation. It is shown that ‘directivity' and ‘fling' affected motions containing long-period acceleration pulses and large velocity steps, are particularly ‘destructive' for the examined systems. The amount of accumulating slip on a steep slope is particularly sensitive to reversal of the polarity of excitation. With some special ground motions, in particular (such as the Sakarya and Yarimca accelerograms, both recorded 3 km from the surface expression of the North Anatolian Fault that ruptured in the 1999 Kocaeli earthquake), what might at first glance appear elusively as ‘small details' in the record may turn out to exert a profound influence on the magnitude of slippage – far outweighing the effects of peak acceleration, peak velocity and Arias intensity. The results are compiled in both dimensionless and dimensional charts, and compared with classical charts from the literature. Finally, it is shown that no convincingly robust correlation could exist between accumulated slip and the Arias intensity of excitation.

SLIPPAGE AND THE CHOICE OF MARKET OR LIMIT ORDERS IN FUTURES TRADING

AbstractRetail futures traders face uncertainty regarding the price they will obtain when trading. This price “surprise,” known as slippage, can be substantial. Using unique data from an introducing brokerage for Chicago Board of Trade (CBOT) wheat, corn, and soybean futures contracts, we quantify time‐to‐clear and the magnitude of slippage. We then identify factors that affect these trade quality measures. Finally, we analyze individual trader choice between market and limit orders and find that the likelihood of placing limit orders, where regulations protect traders from slippage, is greater when order and market characteristic indicate that adverse slippage is likely.

Experimental Investigation and Flow Modeling of Slippage Induced by Additives in Polyolefins in a Modular Co-rotating Twin Screw Extruder

Abstract Experimental and simulation studies of flow of a slipping polymer melt in a co-rotating twin screw extruder are presented. The experiments involve a wide range of polyolefins (polyethylene, isotactic polypropylene, isotactic polybutene-1, isotactic poly 4 methylpentene-1, and a cyclopolyolefin) with an octadecanoic acid additive. Mooney's capillary method is used to prove the occurrence and magnitude of slippage. In the twin screw extruder experiments, the die pressure is reduced for the compounds with octadecanoic acid compared to the neat polyolefins. Screw characteristic curves ( Q vs . dp dx ) were determined experimentally for both the polyolefin compounds and the neat polyolefins. These were found to be rather close. We modeled flow of a slipping non-Newtonian(power law) fluid in a screw channel and calculated screw characteristic curves. These were found to be close to our experimental observations.

Leksell Gamma Knife coordinate setting slippage: how often, how much?

The aim of this study was to determine the incidence and magnitude of coordinate setting slippage during gamma knife surgery (GKS). Thirty-six consecutive patients undergoing GKS with a Leksell unit between June and December 2000 had their coordinates (right and left x-, y-, and z-coordinates; 1548 coordinates; 258 isocenters) and gamma angles checked after the delivery of treatment to each isocenter to determine whether the coordinate settings had slipped and, if so, which settings and the magnitude of the slippage. Coordinate setting slippage during GKS with a Leksell unit does occur but is rare. The magnitude of such slippage is typically within the error of the stereotactic system and coordinate reading. The authors noted that coordinate setting slippage is significantly correlated with patient weight.