To solve the problem of freezing damage in cold-region tunnels, this study proposed a rubber airbag interlayered composite lining system, and tested its performance of buffering, pressure adjustment, ...waterproofing, and heat preservation by simulating a low-temperature environment in an artificial freezing chamber. The experiment results show that the frost-heaving force exerted on the lining can always be lower than 1.69 kPa by constantly adjusting the airbag pressure, and the maximum frost-heaving force can reach 28.25 kPa without the airbag. In addition, the airbag also has good waterproof performance. Finally, the airbag can significantly improve the temperature field of the surrounding rock and reduce the freezing depth (6.75 cm < 17.25 cm). The insulation effect of the airbag is positively correlated with its thickness and negatively correlated with the thermal conductivity of the filling gas. The insulation effect of CO
is better than that of air. The rubber airbag interlayered composite lining system provides a new scheme for freezing damage control in cold-region tunnels.
Air entraining admixtures (AEAs) are surfactant-based solutions and powders that are used to stabilize air voids in cement paste that protect concrete against frost damage. After reviewing the ...chemical and structural features of AEA that govern their performance, we discuss: (i) how they establish a stabilizing shell around air voids, (ii) methods for quantifying the distribution of voids after mixing and after hardening, (iii) mechanisms by which voids protect against frost damage, (iv) effects of AEA on other properties of wet and hardened concrete, and (v) interactions of AEA with other chemical and supplementary cementitious materials.
Climate change may both exacerbate the vulnerabilities and open up new opportunities for farming in the Northeastern USA. Among the opportunities are double-cropping and new crop options that may ...come with warmer temperatures and a longer frost-free period. However, prolonged periods of spring rains in recent years have delayed planting and offset the potentially beneficial longer frost-free period. Water management will be a serious challenge for Northeast farmers in the future, with projections for increased frequency of heavy rainfall events, as well as projections for more frequent summer water deficits than this historically humid region has experienced in the past. Adaptations to increase resilience to such changes include expanded irrigation capacity, modernized water monitoring and irrigation scheduling, farm drainage systems that collect excess rain into ponds for use as a water source during dry periods, and improved soil water holding capacity and drainage. Among the greatest vulnerabilities over the next several decades for the economically important perennial fruit crop industry of the region is an extended period of spring frost risk associated with warmer winter and early spring temperatures. Improved real-time frost warning systems, careful site selection for new plantings, and use of misting, wind machine, or other frost protection measures will be important adaptation strategies. Increased weed and pest pressure associated with longer growing seasons and warmer winters is another increasingly important challenge. Pro-active development of non-chemical control strategies, improved regional monitoring, and rapid-response plans for targeted control of invasive weeds and pests will be necessary.
Tensiometry measurements reveal the behavior of air-entraining agents (AEA) in solutions that isolate features of the pore solution that control the impact on the surface tension of four anionic ...commercial AEAs. The degree to which each surfactant is affected by ionic strength and calcium coagulation is related to its molecular structure and critical micelle concentration.
At the concentration recommended by the AEA manufacturer for use in concrete, two of the AEAs show no reduction in surface tension when exposed to a synthetic pore solution, but show strong interaction with Ca2+ ions. This suggests that some AEAs rely more on surface tension reduction to stabilize bubbles and others rely primarily on calcium interaction. AEAs that self-associate more easily (and interact with calcium more strongly) offer better frost protection for mortars at lower AEA concentrations, which is the focus of a future publication.
•A dynamic model for cold hardiness estimation was developed for three representative cherry cultivars.•Equation coefficients of cultivar-specific models were determined.•LT10, LT50, and LT90 values ...were estimated using a logistic function.•Hardiness is highly dependent on the variations in maximum temperature.•The sensitivity of the parameters for each cultivar and for the three lethal temperatures was simulated.
Plants go through a physiological process of cold hardening to limit the damage, caused by low temperatures at the end of fall and winter. Under a variable climate, plants may be less or more cold hardened and hence more or less susceptible to the effects of an unexpected temperature drop. Seasonal patterns were estimated for three cherry cultivars that vary in freezing tolerance. Measures were taken during fall, winter and early spring for four consecutive seasons. The objective of the study was to develop an empirical dynamic cold hardiness model applicable to three cherry cultivars. The data used to develop the model came from cold hardiness measurements collected for cherry bud hardiness of Bing, Chelan, and Sweetheart during four consecutive seasons (2012–2015) consolidated from the 1st of October through April 30th per each season. Three quantitative lethal temperatures LT10, LT50 and LT90 of bud freezing were estimated from fitted sigmoid curves using a logistic function. Correlations and auto-correlations between lethal observed temperatures and air temperatures (maximum, minimum and average) were calculated. A nonlinear model then was fitted including the lethal temperature of the two days prior to freezing, the accumulative day for the studied period and the maximum temperature. Equation coefficients of cultivar-specific models were determined for each cultivar. Cold hardiness predictions were compared to actual observations for each cultivar and the confidence limits and uncertainty were derived. The model allowed for comparisons of cold hardening and de-hardening between the studied cultivars and between seasons. The information generated by the model can be valuable for frost protection management.
•A new portable wind machine (PM) was evaluated for frost control: first report.•The performance of Stationary (SM) and PMs were tested under different frost conditions.•The PM is less effective than ...the SM in terms of temperature increase and coverage.•The narrow angle of action, the impeller height and the power of PM are its main limiting factors in the frost control effectiveness.
Frosts are one of the most harmful weather events, causing recurrent and great damage in agriculture. Active control methods, such as wind machines, must be implemented to reduce the impact on crops. A new portable wind machine (PM) has been marketed for use in frost control; however, there are no reports on its effectiveness or its performance relative to a stationary wind machine (SM). Thus, the aim of this work was (i) to evaluate and compare the effectiveness on the temperature modification between the SM and PM in different operating configurations; (ii) to study the spatial and vertical temperature variation produced for both machines in several thermal inversion conditions, and (iii) to characterize the airflow pattern generated by the propellers. The evaluation was done on 12 nights with frost during winter and spring in two seasons in a pear orchard. Maximum airflow speed and spatial and vertical temperature profile measurements around the machines were equally distributed and evaluated at the same time. All frost events were characterized by clear skies, low drift and strong and moderate thermal inversion; therefore, beneficial conditions to operate the machines for optimal frost control performance were expected. The PM is not as effective as SM to remove cold air from the surface, not only showing a lower stability and coverage, spatially and vertically, but also achieving a less temperature increase. In the best operational configuration, the SM achieves temperature increase equivalent to 30% and 50% of the inversion strength (measured between 1.5 and 15 m) over of 5.3 ha and 2.7 ha, respectively, whereas the PM achieves similar temperature increases over 3.0 ha and 0.6 ha, respectively. The narrow angle of operation of PM, about 26°, is an important limiting factor in the effectiveness of frost control, so it must be operated with the minimum rotation time. Additionally, the lower height of the PM (8 m) influences the range of the wind gust, especially when facing the rows, and works with colder air of the strata, in comparison with the 13.7 m of the SM. The microclimatic conditions, intra and inter-frost, are highly variable, making it difficult in the case of the PM to implement a correct recommended operating configuration, position and rotation mainly, without a previous site-specific study.
•A canopy protection cyber-physical system (CPCPS) was developed for smart management of frost damage.•The angle of heaters used to protect the orchard was auto-adjusted based on a real-time wind ...direction in the CPCPS.•A set of sensors were used to measure real-time air temperature in the canopy to determine heating schedules for the CPCPS.•The CPCPS increased the percentage of protected time by 198.8 % and 111.9 % in two field tests compared to the non-CPCPS.
Frost events have resulted in huge economic losses in agriculture. Apple flower buds are susceptible to being damaged by cold weather in early spring, leading to reduced apple production. Applying heat is one of the most effective methods to prevent apple flower bud damage. However, growers generally determine when and how to apply heat in orchards based on their experiences and available labor force, leading to either insufficient heating or energy waste. In this study, a frost protection cyber-physical system (CPCPS) was developed to make heating decisions based on real-time ambient temperature and wind direction data. The CPCPS consisted of a real-time temperature sensing system, an angle auto-adjusted heater, and an unmanned ground vehicle (UGV) to move the heating system. The results show that the CPCPS improved protection performance during the field tests. Compared to the non-CPCPS, the CPCPS increased the percentages of canopy protected time by 198.8 % and 111.9 % in two low-temperature field tests. The outcome of the study can be beneficial for enhancing protection performance of canopies in apple orchards.
In recent years, the Alaskan Region of the Federal Aviation Administration (FAA) reported performance issues with some flexible airport pavements. The issues were attributed to changes in the thermal ...regime of the permafrost layers resulting from a warming trend. The poor pavement performance was also caused by such factors as improper design and construction. The FAA Airport Technology Research and Development Branch selected three runways with an asphalt surface from three airports in Alaska and reviewed the pavement failures, design, and construction histories to determine the causes and contributing factors of flexible pavement performance issues. The goal was to determine if and where modifications to FAA guidance concerning design and construction in frost and permafrost zones were needed. This paper focuses on identifying frost and permafrost issues at the airports, identifying the design criteria used at the airports, and determining how closely the design criteria and construction practices followed FAA guidance. The work also recreates the pavement design for each runway, following FAA guidance in effect at the time of the design. Researchers identified areas of the FAA frost and permafrost design criteria that are silent or subject to conflicting interpretation. The paper provides recommendations for possible improvements to current FAA guidance with respect to frost and permafrost design, based on findings from the design reviews. The recommendations target Advisory Circulars 150/5320-6G and 150/5270-10H and are intended to address the design- and construction-related issues.
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