Experimental characterisation of fatigue damage in single Z-pins

Z-pins have been shown to significantly improve delamination resistance and impact strength of carbon fibre reinforced (CFRP) composites. In this paper, an experimental investigation of the influence of different fatigue parameters (mean opening/sliding displacement, amplitude, frequency, number of cycles) on the through-thickness reinforcement (TTR) is presented. For mode I, it is shown that the degradation on pin behaviour during fatigue is mostly affected by the applied displacement amplitude. The degradation is primarily caused by surface wear. Due to the brittleness of the Z-pins, mode II fatigue does not have a significant effect for very small sliding displacements. Exceeding a critical displacement causes the pin to rupture within the very first cycles

Winter Elk Distribution and the Risk Of Brucellosis Transmission from Elk to Livestock in the Northern Greater Yellowstone Ecosystem

Predicting spatio-temporal variations in elk (Cervus elaphus) distributions is necessary to forecast the risk of brucellosis transmission from elk to livestock within the Greater Yellowstone Ecosystem (GYE). Using Global Positioning System (GPS) data collected from 49 telemetry-collared female elk during 2005-2006, we developed predictive resource selection function models for the brucellosis transmission risk period. To determine applicability of predictive models across the larger GYE landscape, we validated predictive models internally, as well as externally at two additional elk ranges within the GYE using 63 telemetry-collared cow elk during 2002-2009. Finally, we integrated extrapolated resource selection function maps and domestic livestock distributions to forecast elk to domestic livestock brucellosis transmission risk. We found elk distributions varied spatially and temporally during the risk period and predictive accuracy was highest in the study area where the model was developed. Predictive accuracy of extrapolated resource selection function maps was lower in other study areas indicating that risk models developed in one portion of the GYE are not as accurate in other portions of the GYE. Relative to the other areas included in this study, the Madison Valley and northern Paradise Valley areas were predicted to have the highest risk of elk to livestock transmission risk. Predictions regarding spatio-temporal variations in transmission risk may be used to prioritize management actions aimed at reducing the potential for brucellosis transmission risk, for example hazing to reduce elk-livestock commingling or producer management of livestock distribution

The Effects of Changes in Elk Archery Regulations on Elk Hunter Effort and Harvest, 2004-2010

We evaluated the effects of changes in elk archery hunting seasons in eastern Montana on hunter numbers, days, and densities and elk harvest. We compared 2 time periods (2004-2007 and 2008-2010) and grouped hunting districts (HDs) into 1 of 4 season types. The 4 season types were limited permits in the Missouri Breaks (7 HDs), limited permits in non-breaks HDs (22 HDs), adjacent HDs were in close proximity to the limited permit HDs that we hypothesized might receive additional hunters displaced from the two more restrictive archery permit areas (22 HDs), and our pseudo-control season type included the rest of the HDs in the state (110 HDs). It appeared, from a statewide perspective, that changing the archery regulations to limited permits in 27 HDs didn’t cause a statistically significant hunter shift to the 22 HDs identified as areas hunters would likely select if restrictions forced them to choose a new area. The only significant changes in hunter numbers and days were decreases in nonresident hunter numbers and days in the Missouri River Breaks HDs. Although the decrease in non-resident use may have had an economic impact in the local area; statewide, there was no change in non-resident use. Pseudo-control HDs showed decreases or no change in harvest response variables. Therefore, the significant harvest increases and/or lack of significant harvest declines in the limited permit areas might be interpreted as a relative success since most of these hunting districts are above population objectives for elk

Effects of Hunter Access on Hunting Season Elk Distributions in the Missouri River Breaks

Increasing harvest of adult female elk (Cervus elaphus nelsoni) is the primary management tool for curtailing elk population growth and reducing elk populations. However, this tool is not effective when elk are located on private properties that restrict hunter access to elk during the hunting season. The purpose of this project was to evaluate the effects of hunter access and other landscape factors on elk resource selection during the archery and rifle hunting seasons in the Missouri River Breaks area. We sampled 46 adult female elk for 2-years in 2 adjacent populations: the Missouri River Breaks (MRB) population and the Larb Hills population. The MRB archery and rifle season elk population ranges were 97% accessible to hunters. Several large properties in the center of the Larb Hills range restricted or did not allow hunter access, and the archery and rifle season elk population ranges were 79% accessible to hunters. To quantify the effects of hunter access and other factors on elk selection of home ranges and elk selection of locations within their home range, we conducted a resource selection modeling exercise. Second-order population-level selection coefficients showed that elk in both MRB and Larb Hills selected home ranges in areas with no hunter access, and hunter access was the strongest predictor of second-order selection. Similarly, third-order population-level selection coefficients showed elk in both populations selected locations within their seasonal home range with no hunter access, and the strength of selection for locations with no hunter access was stronger in the archery season than the rifle season. However, individual models revealed that although third-order population-level selection for no hunter access was strong, only 43% of MRB elk selected for no hunter access during the archery season and 18% of elk selected for no hunter access during the rifle season. Additionally, the majority of all MRB elk locations (i.e., 68% of archery locations and 91% of rifle locations) occurred in areas accessible to hunters. In Larb Hills, individual models confirmed results of the population-level analysis, and 76% and 60% of elk selected for locations with no hunter access during the archery and rifle seasons. Even if hunter access is restricted or in a relatively small geographic area within an elk population range, elk refuge situations may have a disproportionate affect on elk distributions and prevent effective harvest of female elk to maintain elk populations at objective levels. Working cooperatively with stakeholders to minimize these situations is necessary for curtailing further elk population increases and maintaining a distribution of elk across public and private lands. If elk refuge situations cannot be resolved, stakeholders may need to choose between allowing some level of hunter access to harvest female elk or accepting higher numbers of elk, and associated property damage issues

Experimental investigation of the radial structure of energetic particle driven modes

Alfv\'en eigenmodes (AEs) and energetic particle modes (EPMs) are often excited by energetic particles (EPs) in tokamak plasmas. One of the main open questions concerning EP driven instabilities is the non-linear evolution of the mode structure. The aim of the present paper is to investigate the properties of beta-induced AEs (BAEs) and EP driven geodesic acoustic modes (EGAMs) observed in the ramp-up phase of off-axis NBI heated ASDEX Upgrade (AUG) discharges. This paper focuses on the changes in the mode structure of BAEs/EGAMs during the non-linear chirping phase. Our investigation has shown that in case of the observed down-chirping BAEs the changes in the radial structure are smaller than the uncertainty of our measurement. This behaviour is most probably the consequence of that BAEs are normal modes, thus their radial structure strongly depends on the background plasma parameters rather than on the EP distribution. In the case of rapidly upward chirping EGAMs the analysis consistently shows shrinkage of the mode structure. The proposed explanation is that the resonance in the velocity space moves towards more passing particles which have narrower orbit widths.Comment: submitted to Nuclear Fusio

Ethyleen na rooien van tulpen geeft zuur vrij spel

Vlak na het rooien van tulpen treedt stress op, waardoor de ethyleenproductie kan toenemen. Ethyleen kan weer zorgen voor meer zuur. In dit artikel staan de resultaten van PPO-onderzoek naar het optreden van deze stress, en naar het effect van het middel FreshStar

The impact of draping effects on the stiffness and failure behavior of unidirectional non-crimp fabric fiber reinforced composites

Unidirectional non-crimp fabrics (UD-NCF) are often used to exploit the lightweight potential of continuous fiber reinforced plastics (CoFRP). During the draping process, the UD-NCF fabric can undergo large deformations that alter the local fiber orientation, the local fiber volume content (FVC) and create local fiber waviness. Especially the FVC is affected and has a large impact on the mechanical properties. This impact, resulting from different deformation modes during draping, is in general not considered in composite design processes. To analyze the impact of different draping effects on the mechanical properties and the failure behavior of UD-NCF composites, experimental results of reference laminates are compared to the results of laminates with specifically induced draping effects, such as non-constant FVC and fiber waviness. Furthermore, an analytical model to predict the failure strengths of UD laminates with in-plane waviness is introduced. The resulting stiffness and strength values for different FVC or amplitude to wavelength configurations are presented and discussed. In addition, failure envelopes based on the PUCK failure criterion for each draping effect are derived, which show a clear specific impact on the mechanical properties. The findings suggest that each draping effect leads to a “new fabric” type. Additionally, analytical models are introduced and the experimental results are compared to the predictions. Results indicate that the models provide reliable predictions for each draping effect. Recommendations regarding necessary tests to consider each draping effect are presented. As a further prospect the resulting stiffness and strength values for each draping effect can be used for a more accurate prediction of the structural performance of CoFRP parts