Tolerable ranges of fluid shear for early life-stage fishes: implications for safe fish passage at hydropower and irrigation infrastructure

2019 ◽  
Vol 70 (11) ◽  
pp. 1503 ◽  
Author(s):  
Anna Navarro ◽  
Craig A. Boys ◽  
Wayne Robinson ◽  
Lee J. Baumgartner ◽  
Brett Miller ◽  
...  
Keyword(s):  
Strain Rate ◽  
Larval Fish ◽  
Early Stage ◽  
Life Stage ◽  
Early Life Stage ◽  
Fish Passage ◽  
Strain Rates ◽  
Fluid Shear ◽  
Murray Cod ◽  
Irrigation Infrastructure

Egg and larval fish drifting downstream are likely to encounter river infrastructure leading to mortality. Elevated fluid shear is one likely cause. To confirm this and determine tolerable strain rates resulting from fluid shear, egg and larvae of three Australian species were exposed to a high-velocity, submerged jet in a laboratory flume. Mortality was modelled over a broad range of strain rates, allowing critical thresholds to be estimated. Eggs were very susceptible to mortality at low strain rates and 100% of golden and silver perch died once strain rate exceeded 629 and 148s–1 respectively. Larvae were less vulnerable than eggs, but mortality increased at higher strain rates and at younger ages. Most ages of larvae will be protected if strain rate does not exceed 600s–1, although a lower guideline of less than 400s–1 may be needed in areas where very early stage Murray cod larvae drift. Golden perch and silver perch were not susceptible to shear once maturity reached ~25 days post-hatch (nearing juvenile metamorphosis). The thresholds described here will prove useful when refining design and operational guidelines for hydropower and irrigation infrastructure to improve fish survival.

Nucleic Acid, Protein Content, and Growth of Larval Fish Sublethally Exposed to Various Toxicants

1984 ◽  
Vol 41 (1) ◽  
pp. 141-150 ◽  
Author(s):  
Mace G. Barron ◽  
Ira R. Adelman
Keyword(s):  
Nucleic Acid ◽  
Protein Content ◽  
Larval Fish ◽  
Life Stage ◽  
Pimephales Promelas ◽  
Early Life Stage ◽  
Toxicant Exposure ◽  
Growth Measurement ◽  
Log Linear ◽  
Macromolecular Content

Larval fathead minnows (Pimephales promelas) were exposed for 96 h to several concentrations of benzophenone, ethyl acetate, hexavalent chromium, hydrogen cyanide, or p-cresol. The range of "safe" concentrations determined from 96-h macromolecular content (RNA, DNA, and protein) and growth was within or very near the range of "safe" concentrations determined by concomitant longer term exposure (28- to 32-d early life stage toxicity test). RNA, DNA, and protein content per larva and RNA/DNA ratio were sensitive to toxicant stress and followed a log-linear dose response. Larval RNA content appeared to be the 96-h measurement most responsive to toxicant exposure. A disruption of nucleic acid and protein metabolism apparently occurred within 96 h of sublethal toxicant exposure and resulted in (1) decreased rates of mitosis, (2) reduced protein synthesis, and (3) reduced growth. Measurement of growth and macromolecular content after a 96-h larval exposure provided a physiologically relevant measurement of toxicity that was predictive of longer term sublethal toxicity.

Hot Compressive Behavior of Ti-3.0Al-3.7Cr-2.0Fe Titanium Alloy at Different Strain Rates

2012 ◽  
Vol 560-561 ◽  
pp. 1072-1077
Author(s):  
Guo Wang ◽  
Song Xiao Hui ◽  
Wen Jun Ye
Keyword(s):  
Titanium Alloy ◽  
Flow Stress ◽  
Strain Rate ◽  
Early Stage ◽  
True Strain ◽  
Stable State ◽  
Constitutive Relationship ◽  
Test Machine ◽  
Strain Rates ◽  
Temperature Range

The characteristics of hot compression deformation of Ti-3.0Al-3.7Cr-2.0Fe titanium alloy have been studied by Gleeble−1500D thermal simulated test machine in the strain rates range 0.01～10s−1 and temperature range 800～950°C. The true stress-true strain curves show that the peak flow stress decrease with increase temperature and decrease strain rate. At the temperature range in the article, there is a distinct peak in the flow stress in the early stage deformation followed by a stable state at high strains. The variation of flow stress with temperature and strain rate follows the standard kinetic rate equation and the apparent activation energy is estimated to be about 214.22KJ•mol-1. The constitutive relationship of Ti-3.0Al-3.7Cr-2.0Fe alloy is obtained on the base of Arrhenius equation at the experimental conditions.

Growing Up Nonprofit: Predictors of Early-Stage Nonprofit Formalization

2021 ◽  
pp. 089976402110142
Author(s):  
Elizabeth A. M. Searing ◽  
Jesse D. Lecy
Keyword(s):  
Early Stage ◽  
Life Stage ◽  
Early Life Stage ◽  
Fixed Cost ◽  
Growing Up ◽  
Entry And Exit ◽  
Organizational Life ◽  
Organizational Life Cycle ◽  
Start Up ◽  
Equity Ratio

The nonprofit organizational life cycle literature has traditionally focused on the entry and exit processes; the intermediate organizational life stages between these bookends have received less attention. Almost half of all nonprofits at any given time operate in an early life stage with less than US$100,000 in revenue, minimal overhead spending, and no paid managers. This study examines the process by which nonprofits leave the small, informal, startup phase and begin the next life stage characterized by growth and formalization. We identify financial and organizational characteristics that predict whether the nonprofit will successfully transition out of the early and informal life stage. We find that investments in professional fundraising and access to government funds are predictive of the transition out of the start-up phase, while traditional financial predictors such as revenue concentration, equity ratio, fixed cost ratios, and the accumulation of unrestricted assets have modest to no effects.

The effects of strain and strain rate on residual microstructures in copper

1986 ◽  
Vol 44 ◽  
pp. 420-421
Author(s):  
M. F. Stevens ◽  
P. S. Follansbee
Keyword(s):  
Strain Rate ◽  
Applied Stress ◽  
Threshold Stress ◽  
Rate Sensitivity ◽  
Viscous Drag ◽  
Strain Rates ◽  
Strain And Strain Rate ◽  
Threshold Strength ◽  
Mechanism Transition ◽  
Intrinsic Strength

The strain rate sensitivity of a variety of materials is known to increase rapidly at strain rates exceeding ∼103 sec-1. This transition has most often in the past been attributed to a transition from thermally activated guide to viscous drag control. An important condition for imposition of dislocation drag effects is that the applied stress, σ, must be on the order of or greater than the threshold stress, which is the flow stress at OK. From Fig. 1, it can be seen for OFE Cu that the ratio of the applied stress to threshold stress remains constant even at strain rates as high as 104 sec-1 suggesting that there is not a mechanism transition but that the intrinsic strength is increasing, since the threshold strength is a mechanical measure of intrinsic strength. These measurements were made at constant strain levels of 0.2, wnich is not a guarantee of constant microstructure. The increase in threshold stress at higher strain rates is a strong indication that the microstructural evolution is a function of strain rate and that the dependence becomes stronger at high strain rates.

scholarly journals A Review on Mechanical Properties of Natural Fibre Reinforced Polymer Composites under Various Strain Rates

2021 ◽  
Vol 5 (5) ◽  
pp. 130
Author(s):  
Tan Ke Khieng ◽  
Sujan Debnath ◽  
Ernest Ting Chaw Liang ◽  
Mahmood Anwar ◽  
Alokesh Pramanik ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Polymer Composites ◽  
Stress Transfer ◽  
Natural Fibre ◽  
Transfer Efficiency ◽  
Strain Rates ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Fibre Matrix

With the lightning speed of technological evolution, the demand for high performance yet sustainable natural fibres reinforced polymer composites (NFPCs) are rising. Especially a mechanically competent NFPCs under various loading conditions are growing day by day. However, the polymers mechanical properties are strain-rate dependent due to their viscoelastic nature. Especially for natural fibre reinforced polymer composites (NFPCs) which the involvement of filler has caused rather complex failure mechanisms under different strain rates. Moreover, some uneven micro-sized natural fibres such as bagasse, coir and wood were found often resulting in micro-cracks and voids formation in composites. This paper provides an overview of recent research on the mechanical properties of NFPCs under various loading conditions-different form (tensile, compression, bending) and different strain rates. The literature on characterisation techniques toward different strain rates, composite failure behaviours and current challenges are summarised which have led to the notion of future study trend. The strength of NFPCs is generally found grow proportionally with the strain rate up to a certain degree depending on the fibre-matrix stress-transfer efficiency. The failure modes such as embrittlement and fibre-matrix debonding were often encountered at higher strain rates. The natural filler properties, amount, sizes and polymer matrix types are found to be few key factors affecting the performances of composites under various strain rates whereby optimally adjust these factors could maximise the fibre-matrix stress-transfer efficiency and led to performance increases under various loading strain rates.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

scholarly journals Evaluation of Energy Absorption Capabilities of Polyethylene Foam under Impact Deformation

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3613
Author(s):  
Baohui Yang ◽  
Yangjie Zuo ◽  
Zhengping Chang
Keyword(s):  
Energy Absorption ◽  
Failure Modes ◽  
High Strain ◽  
Early Stage ◽  
High Energy ◽  
Test Method ◽  
Test Theory ◽  
Strain Rates ◽  
Impact Properties ◽  
The Impact

Foams are widely used in protective applications requiring high energy absorption under impact, and evaluating impact properties of foams is vital. Therefore, a novel test method based on a shock tube was developed to investigate the impact properties of closed-cell polyethylene (PE) foams at strain rates over 6000 s−1, and the test theory is presented. Based on the test method, the failure progress and final failure modes of PE foams are discussed. Moreover, energy absorption capabilities of PE foams were assessed under both quasi-static and high strain rate loading conditions. The results showed that the foam exhibited a nonuniform deformation along the specimen length under high strain rates. The energy absorption rate of PE foam increased with the increasing of strain rates. The specimen energy absorption varied linearly in the early stage and then increased rapidly, corresponding to a uniform compression process. However, in the shock wave deformation process, the energy absorption capacity of the foam maintained a good stability and exhibited the best energy absorption state when the speed was higher than 26 m/s. This stable energy absorption state disappeared until the speed was lower than 1.3 m/s. The loading speed exhibited an obvious influence on energy density.

scholarly journals Using Artificial Neural Networks to Predict Influences of Heterogeneity on Rock Strength at Different Strain Rates

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3042
Author(s):  
Sheng Jiang ◽  
Mansour Sharafisafa ◽  
Luming Shen
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Strain Rate ◽  
Network Model ◽  
Neural Network Model ◽  
Artificial Neural Network Model ◽  
Rock Strength ◽  
Strain Rates ◽  
Filling Material ◽  
Artificial Neural

Pre-existing cracks and associated filling materials cause the significant heterogeneity of natural rocks and rock masses. The induced heterogeneity changes the rock properties. This paper targets the gap in the existing literature regarding the adopting of artificial neural network approaches to efficiently and accurately predict the influences of heterogeneity on the strength of 3D-printed rocks at different strain rates. Herein, rock heterogeneity is reflected by different pre-existing crack and filling material configurations, quantitatively defined by the crack number, initial crack orientation with loading axis, crack tip distance, and crack offset distance. The artificial neural network model can be trained, validated, and tested by finite 42 quasi-static and 42 dynamic Brazilian disc experimental tests to establish the relationship between the rock strength and heterogeneous parameters at different strain rates. The artificial neural network architecture, including the hidden layer number and transfer functions, is optimized by the corresponding parametric study. Once trained, the proposed artificial neural network model generates an excellent prediction accuracy for influences of high dimensional heterogeneous parameters and strain rate on rock strength. The sensitivity analysis indicates that strain rate is the most important physical quantity affecting the strength of heterogeneous rock.

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