Effect of microcracking on the deformation of ice

1992 ◽  
Vol 29 (1) ◽  
pp. 143-150 ◽  
Author(s):  
Ian J. Jordaan ◽  
Barry M. Stone ◽  
Richard F. McKenna ◽  
Mark K. Fuglem
Keyword(s):  
Strain Rate ◽  
Field Experiments ◽  
Constant Strain Rate ◽  
Creep Damage ◽  
Future Research ◽  
Strain Response ◽  
Short Term ◽  
Large Fluctuations ◽  
Response To Stress ◽  
Stress States

Tests in the field and full-scale experience with arctic structures show that the crushing of ice is accompanied by large fluctuations in load. Field experiments show that, in addition to variations of load in time, significant spatial variations across the contact surface also occur. The deformation is observed to take place in a thin layer of damaged ice, which appears near the structure or indenter surface. It is important to model the deformation and strength of ice in this zone. Various aspects of modelling are discussed in the paper, in particular, measures of damage and the relation to the deformation of ice. The relevance of various components of deformation (elastic, viscous, delayed elastic) is outlined, and two mathematical formulations for the deformation are discussed. The behaviour was investigated by a series of tests at constant strain rate as well as tests in which the strain response to stress of damaged and undamaged ice was measured. The creep rate in damaged ice is shown to be significantly enhanced, even for short-term loading. Comparisons of theory and experiment are given for constant strain-rate tests. The models have been calibrated to the experimental data described in the paper. It is a matter for future research to generalize the models to all damage levels and stress states. Key words : creep, damage, deformation, ice, microcracking, visco-elasticity.

scholarly journals Staying Home, Staying Alive: Campus Food Pantry Student Clients’ Experiences During the COVID-19 Pandemic

2021 ◽  
pp. 193672442110356
Author(s):  
Elmira Jangjou
Keyword(s):  
Coping Strategies ◽  
Thematic Analysis ◽  
Future Research ◽  
Postsecondary Students ◽  
Structured Interviews ◽  
Short Term ◽  
Income Loss ◽  
Food Pantry ◽  
Global Pandemic ◽  
Seeking Help

In response to students’ food insecurity, a number of colleges and universities have taken action and established campus food pantries as part of their intervention plans. However, many of these pantries ceased operation due to COVID-19 campus shutdowns. The purpose of this study is to illustrate the short-term impacts of the COVID-19 pandemic on postsecondary students, who use a university-provided food pantry. Drawing from semi-structured interviews with 12 participants, the thematic analysis explored the initial coping strategies these students used to endure the pandemic. Findings revealed that many students experienced the immediate effects of the pandemic in the form of income loss, self-isolation, anxiety, and appetite change. Although the pandemic interrupted these students’ journeys to continue their studies and become independent in various ways, the affected students implemented various coping strategies, including seeking help from family or friends, using available resources, cooking at home, and even trying to save money. However, considering that the targeted population in this study was already at risk because of their basic needs insecurity, these postsecondary students require extra attention from their higher education institutions in the case of emergencies, such as a global pandemic. In addition to its timely and relevant findings, this study provides important avenues for future research and intervention efforts.

scholarly journals Catchment water quality in the year preceding and immediately following restoration of a drained afforested blanket bog

2021 ◽  
Author(s):  
Paul P. J. Gaffney ◽  
Mark H. Hancock ◽  
Mark A. Taggart ◽  
Roxane Andersen
Keyword(s):  
Water Quality ◽  
Nutrient Release ◽  
Pass Rate ◽  
Future Research ◽  
Negative Effects ◽  
Short Term ◽  
Peatland Restoration ◽  
Blanket Bog ◽  
Quality Threshold ◽  
Policy Incentives

AbstractThe restoration of drained afforested peatlands, through drain blocking and tree removal, is increasing in response to peatland restoration targets and policy incentives. In the short term, these intensive restoration operations may affect receiving watercourses and the biota that depend upon them. This study assessed the immediate effect of ‘forest-to-bog’ restoration by measuring stream and river water quality for a 15 month period pre- and post-restoration, in the Flow Country peatlands of northern Scotland. We found that the chemistry of streams draining restoration areas differed from that of control streams following restoration, with phosphate concentrations significantly higher (1.7–6.2 fold, mean 4.4) in restoration streams compared to the pre-restoration period. This led to a decrease in the pass rate (from 100 to 75%) for the target “good” quality threshold (based on EU Water Framework Directive guidelines) in rivers in this immediate post-restoration period, when compared to unaffected river baseline sites (which fell from 100 to 90% post-restoration). While overall increases in turbidity, dissolved organic carbon, iron, potassium and manganese were not significant post-restoration, they exhibited an exaggerated seasonal cycle, peaking in summer months in restoration streams. We attribute these relatively limited, minor short-term impacts to the fact that relatively small percentages of the catchment area (3–23%), in our study catchments were felled, and that drain blocking and silt traps, put in place as part of restoration management, were likely effective in mitigating negative effects. Looking ahead, we suggest that future research should investigate longer term water quality effects and compare different ways of potentially controlling nutrient release.

scholarly journals Multiple Pedestrians and Vehicles Tracking in Aerial Imagery Using a Convolutional Neural Network

2021 ◽  
Vol 13 (10) ◽  
pp. 1953
Author(s):  
Seyed Majid Azimi ◽  
Maximilian Kraus ◽  
Reza Bahmanyar ◽  
Peter Reinartz
Keyword(s):  
Neural Network ◽  
Deep Learning ◽  
Convolutional Neural Network ◽  
Object Tracking ◽  
Short Term Memory ◽  
Aerial Imagery ◽  
Future Research ◽  
Short Term ◽  
Term Memory ◽  
Long Short Term Memory

In this paper, we address various challenges in multi-pedestrian and vehicle tracking in high-resolution aerial imagery by intensive evaluation of a number of traditional and Deep Learning based Single- and Multi-Object Tracking methods. We also describe our proposed Deep Learning based Multi-Object Tracking method AerialMPTNet that fuses appearance, temporal, and graphical information using a Siamese Neural Network, a Long Short-Term Memory, and a Graph Convolutional Neural Network module for more accurate and stable tracking. Moreover, we investigate the influence of the Squeeze-and-Excitation layers and Online Hard Example Mining on the performance of AerialMPTNet. To the best of our knowledge, we are the first to use these two for regression-based Multi-Object Tracking. Additionally, we studied and compared the L1 and Huber loss functions. In our experiments, we extensively evaluate AerialMPTNet on three aerial Multi-Object Tracking datasets, namely AerialMPT and KIT AIS pedestrian and vehicle datasets. Qualitative and quantitative results show that AerialMPTNet outperforms all previous methods for the pedestrian datasets and achieves competitive results for the vehicle dataset. In addition, Long Short-Term Memory and Graph Convolutional Neural Network modules enhance the tracking performance. Moreover, using Squeeze-and-Excitation and Online Hard Example Mining significantly helps for some cases while degrades the results for other cases. In addition, according to the results, L1 yields better results with respect to Huber loss for most of the scenarios. The presented results provide a deep insight into challenges and opportunities of the aerial Multi-Object Tracking domain, paving the way for future research.

scholarly journals The Effectiveness of the Ecological Forest Rangers Policy in Southwest China

Forests ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 746
Author(s):  
Yifan Wang ◽  
Dengju Wang ◽  
Rong Zhao
Keyword(s):  
Poverty Alleviation ◽  
Southwest China ◽  
Rural Poverty ◽  
Ecological Effect ◽  
Income Growth ◽  
Future Research ◽  
Linkage Mechanism ◽  
Short Term ◽  
Forest Protection

To achieve the dual goal of poverty alleviation and ecological restoration, the policy of ecological forest rangers (EFRs) was implemented in rural poverty-stricken areas in China, where local residents commonly depend on nearby forest resources for livelihoods. This study aimed to analyze the short-term and long-term effectiveness of the EFRs policy in China mainly in poverty alleviation and income growth, with a brief discussion on the ecological effect of the policy. A questionnaire survey was conducted in four counties in the Karst rocky desertification region in southwest China. By combing through the early literature on REDD+, community forestry, leasehold forestry, etc., this paper summarizes the experience and lessons of similar community forest management models, aiming to explain the unsustainability of EFRs policy from the perspective of forest tenure and governance. The findings of the effectiveness analysis of EFRs policy in the four poverty-stricken counties reflect different degrees of effect in rural households with different income levels. We believe that the EFRs policy has played important roles in short-term regional poverty alleviation while its potential for long-term income growth has not been stimulated. For the amendment of EFRs policy, we put forward the following points: (1) It is necessary to redesign the selection and recruitment mechanism, as well as the exit mechanism of EFRs adapting to the local conditions. (2) It is advisable to further improve the local assessment and monitoring system of forest protection quality of EFRs and optimize the establishment of benefit linkage mechanism between protection effectiveness and EFRs remuneration. (3) The EFRs remuneration standards should be dynamically raised to assure the active participation of EFRs in forest protection. Furthermore, there is a need for one more effective integration model of forest protection and rural livelihoods improvement, which is considered as a potential future research direction.

An Experimental Study on the Effect of Prior Plastic Straining on Creep Behavior of 304 Stainless Steel

1993 ◽  
Vol 115 (2) ◽  
pp. 200-203 ◽  
Author(s):  
Z. Xia ◽  
F. Ellyin
Keyword(s):  
Stainless Steel ◽  
Plastic Strain ◽  
Strain Rate ◽  
Creep Behavior ◽  
Test Procedure ◽  
Constant Strain Rate ◽  
304 Stainless Steel ◽  
Creep Model ◽  
Plastic Strain Rate ◽  
Creep Tests

Constant strain-rate plastic straining followed by creep tests were conducted to investigate the effect of prior plastic straining on the subsequent creep behavior of 304 stainless steel at room temperature. The effects of plastic strain and plastic strain-rate were delineated by a specially designed test procedure, and it is found that both factors have a strong influence on the subsequent creep deformation. A creep model combining the two factors is then developed. The predictions of the model are in good agreement with the test results.

scholarly journals Review of Trimester-Specific Gestational Weight Gain and Childhood Adiposity

2014 ◽  
Vol 34 (1) ◽  
pp. 48-53
Author(s):  
K Thapa
Keyword(s):  
Weight Gain ◽  
Childhood Obesity ◽  
Gestational Weight Gain ◽  
Future Research ◽  
Institute Of Medicine ◽  
Short Term ◽  
Global Epidemic ◽  
Targeted Interventions ◽  
Gestational Weight ◽  
Childhood Adiposity

Childhood obesity is a global epidemic and a major public health challenge. There has been increasing evidence that intrauterine exposures, such as alcohol, smoking, and maternal nutritional status, may affect both the long and short term health consequences of the mother and offspring. Childhood adiposity may be affected by the mother’s pre-pregnancy weight and her weight gain during pregnancy. Consequently, interventions may need to start before conception of the child to prevent childhood obesity. In 2009, the Institute of Medicine updated its gestational weight gain recommendations by incorporating rates of gestational weight gain in the second and third trimesters based on the mother’s pre-pregnancy Body Mass Index. There is extensive research on the association between total gestational weight gain and short-term offspring adiposity. However, this review focuses on the association between trimester-specific gestational weight gain and childhood adiposity for singleton pregnancies with respect to the Institute of Medicine’s newly defined weight gain recommendations as very few studies have examined the association between the gestational weight gain during each trimester and childhood adiposity. Identifying the trimester that is most associated with childhood adiposity may help in the development of targeted interventions, guide physician’s nutritional and weight-gain recommendations for child-bearing mothers, and direct future research. DOI: http://dx.doi.org/10.3126/jnps.v34i1.8429   J Nepal Paediatr Soc 2014;34(1):48-53

The Effects of Physical Ageing and of Prior Immersion on the Esc Behaviour of Polycarbonate in Ethanol

1993 ◽  
Vol 305 ◽  
Author(s):  
J. C. Arnold ◽  
A. R. Eccott
Keyword(s):  
Strain Rate ◽  
Immersion Time ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Strain Rates ◽  
Physical Ageing ◽  
Diffusion Effects ◽  
Craze Initiation ◽  
Comparison Of Tests

AbstractThe effects of physical ageing and prior immersion time on the ESC behaviour of polycarbonate in ethanol were studied. Constant strain rate tensile tests were performed at a range of strain rates for samples with ageing times varying from 100 hours to 3000 hours and for prior immersion times of between 1 hour and 500 hours. Comparison of tests performed in ethanol and in air gave a good indication of the point of craze initiation. The results showed that there was a reduction in strain to crazing as the strain rate decreased, apart from with the lowest strain rate used. A longer prior immersion time also promoted craze formation. Both of these results are attributable to diffusion effects. Physical ageing had little effect on the ESC behaviour, due to the large amounts of deformation encountered in this system.

A Synthesis of Knowns, Unknowns, and Policy Recommendations from the Sea Lamprey International Symposium

1980 ◽  
Vol 37 (11) ◽  
pp. 2202-2208 ◽  
Author(s):  
Carl J. Walters ◽  
George Spangler ◽  
W. J. Christie ◽  
Patrick J. Manion ◽  
James F. Kitchell
Keyword(s):  
International Symposium ◽  
Large Scale ◽  
Fishery Management ◽  
Field Experiments ◽  
Lake Trout ◽  
Sea Lamprey ◽  
Future Research ◽  
Fish Stock ◽  
Total Production ◽  
Pilot Studies

The Sea Lamprey International Symposium (SLIS) has provided a broad spectrum of facts and speculations for consideration in future research and management programs. Many aspects of the laboratory biology and field life history of the sea lamprey (Petromyzon marinus) are now well understood. There is little question that it can now be controlled by chemical larvicides, and perhaps in the future by more efficient integrated control programs. There is correlative evidence (wounds, scars, catch curves) that lamprey caused major mortalities in some fish species, and that control in conjunction with stocking has lead to remarkable recoveries of salmonid stocks in the Great Lakes. However, there are great gaps in understanding about just what the lamprey does under field conditions, and it is not yet possible to reject several hypotheses that assign lamprey a minimum or transient role in fish stock changes. Further studies on details of lamprey biology are, in themselves, unlikely to fill the gaps; one alternative is to conduct a large-scale field experiment involving cessation of lamprey control while holding other factors (fishing, stocking) as steady as possible. If it is decided to proceed with management on the assumption that lamprey are important, without the major field experiments to confirm it, then at least the following steps should be taken: (1) the chemical treatment program should be reviewed in detail, with a view to finding treatment schedules that will minimize frequency and dose rates for lampricide applications; (2) pilot studies on alternative control schemes (sterile male, attractants, barriers) should only be funded if they are statistically well designed (several replicate and control streams), and involve quantitative monitoring of lamprey spawning success and subsequent total production of transforming larvae; (3) the lake trout (Salvelinus namaycush) stocking program should be maintained at its present level, and should involve diverse genotypes rather than a few hatchery strains; (4) growth in the sport fisheries for lake trout should be curtailed, and commercial fisheries should not yet be permitted; (5) a multispecies harvesting policy should be designed that takes into account the buffering effect of each species on lamprey mortality suffered by others (i.e. should some species not be harvested at all, and viewed instead as buffers for more valuable species?); and (6) a program should be developed for restoring, by culture if necessary, native forage species in case the introduced smelt and alewife should collapse under pressure from fishing and prédation by the growing salmonid community.Key words: sea lamprey, proposed research, fishery management, mathematical models, population dynamics

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