The Experts below are selected from a list of 9246 Experts worldwide ranked by ideXlab platform
David M. Mcclung - One of the best experts on this subject based on the ideXlab platform.
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Snow avalanche Runout from two Canadian mountain ranges
Annals of Glaciology, 2017Co-Authors: D.j. Nixon, David M. McclungAbstract:Field measurements on maximum Runout from two different mountain ranges in Canada are presented and compared: the Coast Mountains in British Columbia and the Rocky Mountains. We include a statistical analysis of topographic terrain parameters such as starting zone catchment area, horizontal reach, vertical drop and relevant slope angles. Following McClung and Mears (1991), we derived a dimensionless parameter which is a measure of Runout for each avalanche and we found that the Runout ratios (defined below) for a given mountain range obey a Gumbel distribution consistent with previous results. In addition, we found that the Runout ratios for both mountain ranges have a length-scale dependence which is potentially very important for land-use planning procedures: the mean value of the Runout ratio decreases significantly as the horizontal reach increases. Together with data from other mountain ranges, our results show that path length effects will have to be incorporated when using statistical prediction methods for engineering zoning purposes. The Runout ratio is defined as the quotient of two lengths, Δx/Xβ, where Δ is the horizontal distance from the 10° point to the maximum Runout position, and Xβ is the horizontal distance from the start position to the point where slope angle first declines to 10°.
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Extreme avalanche Runout: a comparison of empirical models
Canadian Geotechnical Journal, 2001Co-Authors: David M. McclungAbstract:The prediction of snow avalanche Runout distances and the probability of exceeding the predicted positions is the first and most important step required before making decisions about placement of facilities or control structures in snow avalanche prone terrain. There are two main prediction methods for calculating Runout distances: (1) procedures linked to the selection of friction coefficients in avalanche dynamic models, and (2) empirical, statistical prediction based on terrain parameters for a set of extreme Runout distances for the mountain range in question. Within the second method there are presently two competing empirical approaches to prediction: (i) ordinary least squares regression analysis related to angles measured for the path profile in question, and (ii) extreme value prediction of Runout based on a Gumbel distribution of a dimensionless terrain parameter. In this paper a comparison of the two empirical methods with emphasis on the slope steepness in the Runout zone is provided. The comp...
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Extreme avalanche Runout in space and time
Canadian Geotechnical Journal, 2000Co-Authors: David M. McclungAbstract:The distribution of avalanche Runout varies in space and time for individual avalanche paths and from mountain range to mountain range. In this paper, such variations are considered based on the assumption (supported by data worldwide) that the spatial distribution of extreme avalanche Runout follows a Gumbel distribution and that the arrival rate of avalanches can be modelled as a Poisson process. The input required is a set of extreme avalanche Runout distances for the mountain range and a knowledge of avalanche frequency at the beginning of the Runout zone for the path in question. Such information allows theoretical estimation of the effective return period as a function of position, which is very important in zoning applications. In addition, general expressions are derived to relate Gumbel parameters for different mountain ranges to a frequency index to explore general frequency implications from one mountain range to another. The estimated Gumbel parameters imply consistent relationships for expect...
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Characteristics and Prediction of High-Frequency Avalanche Runout
Arctic and alpine research, 1997Co-Authors: Mike J. Smith, David M. McclungAbstract:In this paper, we present field data and analysis relating avalanche terrain variables and avalanche Runout for 46 high-frequency avalanche paths. Most previous studies of this nature have been concerned with the location of extreme Runout for return periods of order 100 yr. In our study, we focus on extreme Runout avalanche paths where return periods are much less than 100 yr and we compare the results with previous data collections. Our analysis shows that high-frequency avalanche paths are, on average, steeper and shorter than their low frequency counterparts. Our analysis also indicates that the dimensionless measure of avalanche extreme Runout, the Runout ratio, approximates a Gumbel distribution, consistent with previous results. The calculation of a nonexceedance probability, using the Gumbel distribution, is recommended for the prediction of extreme Runout in land-use planning exercises for zones effected by high frequency avalanches.
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Extreme value prediction of snow avalanche Runout
Cold Regions Science and Technology, 1991Co-Authors: David M. Mcclung, Arthur I. MearsAbstract:Abstract Avalanche Runout distances have traditionally been calculated by selecting friction coefficients and then using them in an avalanche dynamics model. Uncertainties about the mechanical properties of flowing snow and its interaction with terrain make this method speculative. Here, an alternative simple method of predicting Runout based on terrain variables is documented. By fitting Runout data from five mountain ranges to extreme value distributions, we are able to show how (and why) extreme value parameters vary with terrain properties of different ranges. The method is shown to be applicable to small and truncated data sets which makes it attractive for use in situations where detailed information on avalanche Runout is limited.
J. B. Aaron - One of the best experts on this subject based on the ideXlab platform.
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Rock avalanche Runout prediction using stochastic analysis of a regional dataset
Landslides, 2020Co-Authors: A. Mitchell, S. Mcdougall, N. Nolde, M.-a. Brideau, J. Whittall, J. B. AaronAbstract:Rock avalanches involve extremely rapid, flow-like movement of fragmented rock with extreme destructive potential. With increasing development pressures in mountainous regions, there is a need for simple, stochastic estimates of Runout distances to aid in hazard assessments and prioritize sites for more detailed investigation. To support the development of an empirical predictive tool, a systematic method was used to describe 49 rock avalanches in the Canadian Cordillera, which had been documented in the literature but not previously compiled into a regional inventory. These cases were described using measured or estimated numerical values for volume, fall height, Runout length, total impacted area and the ratio of total impacted area over Runout length (referred to as mean path width), and qualitative descriptions of the topographic confinement, substrate material and source geology. Linear regressions were fit to the data, with qualitative attributes treated as indicator variables. A strong relationship was found for Runout distance predicted from volume, fall height and lateral confinement. A second relationship was found for mean path width over Runout length predicted from volume. These relationships were converted to survival functions to estimate the Runout exceedance probability and the mean path width exceedance probability. These survival functions were implemented in a computer tool, called the Probabilistic Runout Estimator—Rock Avalanche (PRE-RA), which can be used to estimate spatial impact probability ranges for rock avalanche Runout. An application of this tool was demonstrated using two recent Canadian rock avalanches, which were not used in the dataset to estimate the statistical relationships.
Einat Aharonov - One of the best experts on this subject based on the ideXlab platform.
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Long Runout landslides: a solution from granular mechanics
Frontiers in Physics, 2015Co-Authors: Stanislav Parez, Einat AharonovAbstract:Large landslides exhibit surprisingly long Runout distances compared to a rigid body sliding from the same slope, and the mechanism of this phenomena has been studied for decades. This paper shows that the observed long Runouts can be explained quite simply via a granular pile flowing downhill, while collapsing and spreading, without the need for frictional weakening that has traditionally been suggested to cause long Runouts. Kinematics of the granular flow is divided into center of mass motion and spreading due to flattening of the flowing mass. We solve the center of mass motion analytically based on a frictional law valid for granular flow, and find that center of mass Runout is similar to that of a rigid body. Based on the shape of deposits observed in experiments with collapsing granular columns and numerical simulations of landslides, we derive a spreading length Rf~V^1∕3 . Spreading of a granular pile, leading to a deposit angle much lower than the angle of repose or the dynamic friction angle, is shown to be an important, often dominating, contribution to the total Runout distance. The combination of the predicted center of mass Runout and the spreading length gives the Runout distance in a very good match to natural landslides.
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Long Runout landslides: a solution from granular mechanics
Frontiers in Physics, 2015Co-Authors: Stanislav Parez, Einat AharonovAbstract:Large landslides exhibit surprisingly long Runout distances compared to a rigid body sliding from the same slope, and the mechanism of this phenomena has been studied for decades. This paper shows that the observed long Runouts can be explained quite simply via a granular pile flowing downhill, while collapsing and spreading, without the need for frictional weakening that has traditionally been suggested to cause long Runouts. Kinematics of the granular flow is divided into center of mass motion and spreading due to flattening of the flowing mass. We solve the center of mass motion analytically based on a frictional law valid for granular flow, and find that center of mass Runout is similar to that of a rigid body. Based on the shape of deposits observed in experiments with collapsing granular columns and numerical simulations of landslides, we derive a spreading length Rf~V^1/3. Spreading of a granular pile, leading to a deposit angle much lower than the angle of repose or the dynamic friction angle, is shown to be an important, often dominating, contribution to the total Runout distance, accounting for the long Runouts observed for natural landslides.
Han Ding - One of the best experts on this subject based on the ideXlab platform.
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mechanics and multi regenerative stability of variable pitch and variable helix milling tools considering Runout
International Journal of Machine Tools & Manufacture, 2017Co-Authors: Jinbo Niu, Ye Ding, Li-min Zhu, Han DingAbstract:Abstract Variable pitch and variable helix (VPVH) milling tools are usually utilized to mitigate regenerative chatter vibrations by destroying the vibration phases between adjacent teeth. But this chatter suppression mechanism may considerably be disturbed by the inevitable tool Runout, which could also change the phases, even to a larger extent. Thus the cutting performance of VPVH tools in terms of mechanics and dynamics should be re-evaluated by taking Runout into consideration. This paper firstly sets up the mechanistic model for VPVH tools and then presents a combined nonlinear optimization procedure to identify the cutting coefficients and Runout parameters. Secondly, the dynamic system of VPVH tools considering Runout is modeled by a periodic-coefficient delay differential equation with multiple underdetermined delays. Afterwards, the generalized Runge-Kutta (GRK) method is extended to tackle the Runout-induced multi-regenerative effects and thus to analyze the milling process stability. The accuracy and efficiency of the GRK method is validated using published numerical examples. A series of cutting experiments with a commercially available VPVH tool are performed to verify the presented mechanistic and dynamic models. It confirms that Runout cannot be neglected when evaluating the cutting performance of VPVH tools. Finally, the joint influences of Runout and pitch/helix angles on cutting forces and chatter stability of VPVH tools are discussed in detail based on the proposed approach.
Tae Jo Ko - One of the best experts on this subject based on the ideXlab platform.
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optimization of feedrate in a face milling operation using a surface roughness model
International Journal of Machine Tools & Manufacture, 2001Co-Authors: Dae Kyun Baek, Tae Jo KoAbstract:Optimization of feedrate is valuable in terms of providing high precision and efficient machining. The surface roughness is particularly sensitive to the feedrate and the Runout errors of the inserts in a face-milling operation. This paper analyzes the effects of the insert Runout errors and the variation of the feedrate on the surface roughness and the dimensional accuracy in a face-milling operation using a surface roughness model. The validity of the developed model was proved through cutting experiments, and the model was used to predict the machined surface roughness from the information of the insert Runouts and the cutting parameters. From the estimated surface roughness value, the optimal feedrate that gave a maximum material removal rate under the given surface roughness constraint could be selected by a bisection method.
