Freezing Conditions Research Articles

Lattice Shrinkage of 2D-COFs under Electron Beam Irradiation

Over the past two decades, covalent organic frameworks (COFs) have become the most widely studied porous crystalline materials. Their specific physical and chemical properties are determined by the arrangement of atoms (crystal structure). Therefore, the determination of their structure is arguably the most important characterization step for COFs. Although single-crystal X-ray diffraction is the most widely used method for structure determination, confirmation of the structure of COFs is limited to lattice fringes in transmission electron microscopy (TEM) because of their small crystal size (nanocrystals) or poor crystal quality. At present, many two-dimensional COFs (2D-COFs) have clear powder X-ray diffraction (PXRD) patterns, but specific lattice fringes are not available for all 2D-COFs. This severely hinders the development of the COF field. Here, we discovered the lattice shrinkage behavior of COFs under electron beam irradiation by comparing the lattice fringes of 2D-COFs under different conditions. By comparing the lattice fringes of a 1,3,5-tris-(4-aminophenyl)triazine-1,3,5-tris-(4-formylphenyl)triazine covalent organic framework (TAPT-TFPT COF) at room temperature and under liquid nitrogen freezing conditions, we found that the lattice fringes are in good agreement with the PXRD and the theoretical values of the COF (2.213 nm) under freezing conditions. However, the lattice fringe spacing is only 1.656 nm at room temperature. The discovery not only provides new insights into the TEM characterization of COFs, but also further expands the range of crystalline COF materials.

Effects of different plant proteins on the quality and characteristics of heat induced egg white protein gel under freezing conditions

Eggs white is rich in protein, whose gel property is one of the most important functional characteristics during processing. The purpose of this study was to reveal the effect of different plant proteins (2% (w/w), 2.5% (w/w), 3% (w/w)) on the quality of heat induced egg white protein (EWP) gel after freezing. Gels were prepared by adding 2.5% soy protein isolates (SPI) or pea protein isolates (PPI), and then were frozen for 14 days. Compared with the control group (EWP without adding any plant proteins), the hardness, chewiness and gumminess of SPI-EWP gel were increased by 58.23%, 71.11% and 66.35%, respectively, which was better than PPI-EWP. The thawing loss rate of SPI-EWP and PPI-EWP gel decreased by 16.8% and 13.0%, respectively, and the centrifugal loss rate decreased by 13.2% and 11.8%, respectively. The addition of plant proteins resulted in a decrease in the proton signal intensity of the T23 peak. Hydrogen proton imaging and rheology results showed that water content of gels added with plant proteins after freezing was higher than control group and showed better viscoelasticity (SPI was better than PPI). The results of intermolecular forces indicated that with the increase of plant protein, the ionic bonds decreased, the contribution of disulfide bonds significantly increased (p < 0.05). Fourier Transform Infrared Spectroscopy (FTIR) indicated that the α-helix content decreased, β-sheet increased. In brief, this study provides valuable reference for the development and application of plant protein to improve the quality of egg white protein in food industry.

Mode of formation of cryogenic cave carbonates: Experimental evidence from an Alpine ice cave

Coarsely crystalline carbonates that formed cryogenically in caves (CCCcoarse for short) are important paleoenvironmental archives that provide evidence of former perennial ice deposits in currently ice-free caves and allow the timing of the past freezing conditions close to 0 °C in the subsurface to be determined. Despite their significance, the mode of formation of these deposits has never been observed in statu nascendi.We conducted a series of freezing experiments in an Alpine ice cave to test the conceptual model of CCCcoarse formation in freezing pools of water in perennial ice deposits. Our results document a number of features associated with the freezing of such confined water bodies, including ice bulging, cracking and episodic expulsion of water. These observations help explain the degassing of carbon dioxide required to maintain carbonate precipitation in these semi-closed pockets of slowly freezing water. Our experiments yielded a range of morphological types of cryogenic calcite crystals and aggregates comparable to those reported from CCCcoarse from currently ice-free caves elsewhere. The experimentally grown crystals also exhibit the same depleted O isotope composition characteristic of natural carbonates interpreted as being formed subaqueously in a semi-closed pools subject to freezing. The main difference to naturally formed CCCcoarse is their smaller crystal size, reflecting the comparably short freezing time of our experiments of less than two weeks.This study confirms the conceptual model explaining the formation of CCCcoarse in localized pools in ice and calls for a revision of the currently existing classification scheme for cryogenic cave carbonates.

Experimental and Theoretical Study of the Influence of Saline Soils on Frozen Wall Formation

This paper examines the impact of salinity on the thermophysical properties of soils during artificial freezing. It focuses on analyzing heat and mass transfer in saline soils for constructing a frozen wall around a mineshaft at a potash salt deposit. The presence of salts in the groundwater near the contact point with water-protective strata is common in these deposits. Experimental studies were conducted on clay, chalk, and sand to understand the effect of salinity on the freezing temperature, unfrozen water content, specific heat capacity, and thermal conductivity of wet soil. These findings were used to simulate heat and mass transfer in saline soils using a one-dimensional model. The technique of circumferential averaging was introduced to account for the thermal impact of freeze pipes. The results indicate that higher soil salinity leads to a faster decrease in soil temperature under freezing conditions, although this dependence is weak for clay. This study also revealed that an increase in initial salinity results in a reduction in the thickness of the frozen wall. It was found that, for chalk and sand, there exists a range of initial salinity during which the frozen wall’s thickness is almost independent of the initial salinity.

Investigation of freezing temperature and time to improve resistant starch content and quality of pure mung bean starch vermicelli

Mung bean vermicelli is one of the commonly consumed styles of noodles because of its convenience in Asian countries as well as being a good source of resistant starch (RS). It was hypothesized that suitable freezing conditions could produce mung bean vermicelli with a greater RS content and good cooking quality compared to the commercially available product. Therefore, this study investigated the optimum freezing conditions to increase the RS content in mung bean vermicelli. After extrusion, boiling, and cooling, the drained vermicelli was incubated at 4 C for 1 h 30 min before using different freezing conditions by varying the processing temperature (-5, -10, -15, or -20 C) and time (6, 12, 18, or 20 h for each temperature).The highest RS content was observed in dried mung bean vermicelli (12.83% at -10 C for 18 h; V1018), whereas the commercial vermicelli had the lowest RS content (9.73%). The cooking time, water absorption, volume increase, and resistant starch content of cooked V1018 were higher with values of 12.69 min, 502.97%, 19.13% and 7.32%, respectively, than those of the commercial vermicelli (8.56 min, 347.34%, 15.19% and 5.58%, respectively). Furthermore, the cooking loss, tensile strength, and elasticity of V1018 were 1.08%, 0.0101 N, and 11.96 mm, respectively, which were lower than for the commercial vermicelli (1.96%, 1.16-folds, and 2.16-folds, respectively). The color of dried V1018 vermicelli had more lightness, redness, and yellowness, while the cooked V1018 vermicelli had more lightness, greenness, and blueness than the respective commercial products. Hence, incubating at 4 C for 1 h 30 min, followed by freezing at -10 C for 18 h was recommended to produce pure mung bean starch vermicelli with a high resistant starch content and good quality

Burr formation mechanism and morphological transformation in grinding of nickel-based superalloy honeycomb cores under ice freezing and MQL conditions

Nickel-based superalloy honeycomb core (NBSHC) is extensively used in aerospace field due to the light weight, high specific strength and high temperature resistance. The burrs of NBSHC are extremely prone to be formed during machining and the insufficient welding strength or false welding between NBSHC and skin is generated because of the large or unreasonable burr morphology, resulting in premature failure of the parts. In this work, a novel method of ice freezing combining with minimum quantity lubrication (MQL) was proposed to grind NBSHC to improve the burr morphology and size. The burr formation mechanisms of NBSHC under ice freezing and MQL conditions were revealed by single abrasive particle grinding cell wall and verified by grinding experiments. The grinding force, burr morphology transformation mechanisms and size were investigated in-detail by experiments combining with FEM results. The results indicated that MQL and ice freezing decreased the plastic flow property of material by reducing the temperature and friction of NBSHC, thereby promoting the transformation of burr size from large into micro, and the burr shape from long strip into block. Decreasing grinding depth can also improve the burr morphology by decreasing the volume of plastic flow material. The improving effects of full of ice freezing were better than MQL for NBSHC grinding. The machining efficiency under full of ice combining with MQL was 3 times of that under quasi-dry grinding. These findings are significant for improving the machining quality and exploring the burr morphology transformation of NBSHC.

Effect of Different Chloride Salts on the Transport of Water, Heat, and Solutes in Sandy Soil under Freezing Conditions

Effect of Different Chloride Salts on the Transport of Water, Heat, and Solutes in Sandy Soil under Freezing Conditions

Observation on the ice crystal formation process of large yellow croaker (Pseudosciaena crocea) and the effect of multiple cryoprotectants pre-soaking treatments on frozen quality

By observing the formation behavior of ice crystals, the quality of food products under different freezing conditions can be intuitively judged. In this paper, large yellow croaker was taken as the research object, and a novel cryomicroscopic system was developed to directly observe the structure of ice crystals during the freezing process. The cryoprotective effects of 4% sucrose +4% sorbitol (SU + SO), 4% xylo-oligosaccharide (XO), 4% xylo-oligosaccharide + 0.3% tetrasodium pyrophosphate (XO + TSPP) and 0.2% antifreeze protein (AFP) at different freezing temperatures were investigated. And the evaluation indicators, such as cell deformation degree, equivalent diameters, roundness, elongation and fractal dimension were introduced to quantify the damage of ice crystals to muscle tissues and fibers. The results indicate that reducing the freezing temperature and adding cryoprotectants can improve the quality of large yellow croaker. AFP has the best cryoprotective effect, with a reduction in cell deformation degree of 54.78% and 67.83% compared to the Control group at −5 °C and −20 °C, respectively. SU + SO and XO have the equivalent antifreeze effect, which is slightly inferior to XO + TSPP. In addition, physical parameters of large yellow croaker samples were measured to verify the influence of ice crystal structure on product quality. Therefore, direct observation of the ice crystal formation process and evaluation of ice crystal structure can accurately reflect the quality of frozen products, which is of great significance for the development of refrigeration and preservation technology.

Slope stability analysis model for the frost-susceptible soil based on thermal-hydro-mechanical coupling

Slope stability analysis has been performed through various analysis methods ranging from general limit equilibrium methods, such as those proposed by Janbu, Bishop, and Fellenius, to finite element methods. Using these methods, analyzing the slope stability considering the change in soil stiffness due to the freezing or thawing conditions resulting from temperature changes is infeasible. Therefore, considering this shortcoming, a thermal-hydro-mechanical slope stability analysis model (THM-SSA model) is proposed for slope stability analysis. The main feature considered in the THM-SSA model was the slope of the critical state line based on the load angle. Additionally, this model could calculate the local factor of safety (LFS) for the slope based on the isotropic tensile strength of the unfrozen soil and the changes in it after being subjected to repeated freeze–thaw cycles. To verify the proposed THM-SSA model, the stress–strain results were compared with those of the experimental triaxial compression tests that were conducted under different temperatures of the frozen soil with a corresponding number of freeze–thaw cycles. Based on this, a simulation of slope stability analysis was performed as demonstration, and using the verified THM-SSA model, the LFS was calculated according to the freeze–thaw cycles of the slope.

Development of an instrument-free and low-cost ELISA dot-blot test to detect antibodies against SARS-CoV-2.

Most laboratory tests to detect the presence of anti-SARS-CoV-2 antibodies use enzyme-linked immunosorbent assays (ELISA) or chemiluminescence immunoassays (CLIA); however, equipment for these immunoassays is unavailable in many areas of low- and middle-income countries. Rapid lateral flow immunoassay (LFIA) tests are an equipment-free option, but their high price may make them less suitable for conducting seroprevalence surveys. Here, we describe a simple dual antigen ELISA dot-blot test to detect anti-SARS-CoV-2 IgG antibodies with high sensitivity (94-98%) and specificity (92-100%), compared to commercially available ELISA and CLIA options. Additionally, this ELISA dot-blot test can be completed in one hour using minimal laboratory equipment. Importantly, this immunoassay is significantly more affordable than most LFIA tests available on the global market. The dot-blot strips may be stored for up to 7 days under freezing conditions. This ELISA dot-blot test is a cost-effective option for conducting seroprevalence screenings in areas lacking ELISA or CLIA facilities, compared to LFIA tests.

Grey relativity correlations between the pore structures and compressive strength of aeolian sand concrete undergoing carbonation and freeze-thaw cycles

In this study, the compressive strength of aeolian sand concrete (ASC) was predicted using pore structure parameters and pore structure types under the conditions of a complex environment. The relationships between the pore structures and the compressive strength of the ASC undergoing carbonation and freeze-thaw coupling actions were examined. Full ASC with a 100% replacement rate of aeolian sand (AS) was used in this study’s experiments. The microstructure characteristics of the ASC were analyzed using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). At the same time, the correlation degrees of the pore structures and compressive strength were examined using a grey relativity analysis method. A GM (1, 3) prediction model of the ASC compressive strength under different carbonization times was established. The model showed that the effects of the carbonization and freeze-thaw cycles (FTCs) on the pore structures and the compressive strength of the ASC were different. According to the grey relativity analysis results, the bound fluid saturation and harmless pore ratios had the greatest impacts on the compressive strength of the ASC. The model established based on those factors had the ability to accurately predict the compressive strength of the ASC under the conditions of a carbonation-salt freezing and thawing environment.

Stability of pesticide residues in citrus fruits during storage

Introduction. Storage of selected samples before transportation to the laboratory and immediately before analysis is an important component in the process of product quality control and evaluation.&#x0D; Purpose of the work was to evaluate the degradation of pesticide active substances in real samples of citrus fruit left for long periods of storage in deep freezing conditions.&#x0D; Materials and methods. High-performance liquid chromatography with triple quadrupole mass detector (HPLC-MS/MS) was used to identify and quantify pesticide active substances. According to the method of analysis MUK 4.1.3657–20, cryogenic grinding of samples was carried out in a cutter using dry ice. Sample preparation was carried out using the QuEChERS technology. To extract analytes from a homogenized sample acetonitrile was used in the presence of salts containing citrate buffer, followed by purification of the extract by SPE.&#x0D; Results. In the studied samples of citrus, the analytes showed stability. Thirty months after storage of samples in deep freezing conditions (temperature not higher than –20 °C), the identified levels of active ingredients of the pesticides imazalil, pyrimethanil and prochloraz did not change by more than 20% compared to the previously detected concentrations. Insignificant amounts of imidacloprid, thiabendazole and pyriproxyfen, as well as traces of azoxystrobin and trifloxystrobin, detected in the study of samples, were also found in samples after long-term storage. &#x0D; Limitation. The study is limited to the study of the stability of individual active substances found in real samples of citrus fruits intended for sale to the consumer.&#x0D; Conclusion. Proper storage of samples should ensure the preservation of the levels of active substances in the samples and exclude their change due to various processes (volatilization, enzymatic and hydrolytic decomposition, etc.), which requires the performance of preliminary experimental studies to assess their stability. The work showed the stability of residual quantities of imazalil, pyrimethanil, prochloraz, imidacloprid, thiabendazole, and pyriproxyfen in citrus fruit matrices under storage conditions in a freezer at not more than –20 °C for 30 months.

Effects of frozen storage conditions and freezing rate on the stability of coagulation proteins in human plasma.

Degradation of coagulation proteins in frozen plasma may influence assay results. The aims of this study were to explore the changes in coagulation parameters in patient plasma and internal quality control (IQC) after different freezing and storage conditions during the short-term and long-term periods. Platelet poor plasma was prepared from citrated peripheral blood collected from a group of healthy donors. The plasma was pooled, frozen and stored in a variety of freezing and storage conditions. The changes were monitored using routine coagulation assays, as well as factor VIII (FVIII) and protein S (PS) assays. Plasma stored in liquid nitrogen (LN2) or in -80°C showed long-term stable values for routine tests for a period of over 12 months, and 6 months for FVIII. Interestingly, the activated partial thromboplastin time (aPTT) showed a temporary significant prolongation over the first two weeks. Plasma frozen and stored in -40°C is not viable for aPTT and FVIII testing, otherwise it can be used for other parameters for up to 4 months. PS showed a significant increase in all frozen samples. Freezing rate has a significant impact on plasma quality and the final storage temperature influences the long-term stability. The optimal storage conditions are ultra-low temperatures (LN2 or -80°C) and the highest freezing rate possible. However, frozen plasma is not viable for IQC of aPTT during a period of two weeks after freezing. This study is unique in its conception as a practical guide for the handling of frozen plasma samples in modern laboratory settings.

CB1R blockade unmasks TRPV1-mediated contextual fear generalization in female, but not male rats.

Increasing evidence suggests that the neurobiological processes that govern learning and memory can be different in males and females, but many of the specific mechanisms underlying these sex differences have not been fully defined. Here we investigated potential sex differences in endocannabinoid (eCB) modulation of Pavlovian fear conditioning and extinction, examining multiple defensive behaviors, including shock responsivity, conditioned freezing, and conditioned darting. We found that while systemic administration of drugs acting on eCB receptors did not influence the occurrence of darting, females that were classified as Darters responded differently to the drug administration than those classified as Non-darters. Most notably, CB1R antagonist AM251 produced an increase in cue-elicited freezing and context generalization selectively in female Non-darters that persisted across extinction and extinction retrieval tests but was prevented by co-administration of TRPV1R antagonist Capsazepine. To identify a potential synaptic mechanism for these sex differences, we next employed biochemical and neuroanatomical tracing techniques to quantify anandamide (AEA), TRPV1R, and perisomatic CB1R expression, focusing on the ventral hippocampus (vHip) given its known role in mediating contextual fear generalization. These assays identified sex-specific effects of both fear conditioning-elicited AEA release and vHip-BLA circuit structure. Together, our data support a model in which sexual dimorphism in vHip-BLA circuitry promotes a female-specific dependence on CB1Rs for context processing that is sensitive to TRPV1-mediated disruption when CB1Rs are blocked.

The role of avoidance in modulating single prolonged stress effects on emotional memory in male and female rats

The incidence of post traumatic stress disorder (PTSD) is greater in women than men, but mechanisms via which this difference manifests remain under explored. The single prolonged stress (SPS) rodent model of traumatic stress has been used to identify mechanisms through which traumatic stress leads to deficits in retaining extinction (a core PTSD symptom), but has been mostly utilized in male model systems. Recent studies have observed that SPS leads to changes in persistent fear memory in female rats, though these results are variable. This variability could be driven by changes in behavioral strategy in females during extinction, but this possibility has not been sufficiently explored. To address this, we examined the impact of SPS on freezing and avoidance (a core PTSD symptom) during extinction in male and female rats. In male rats, SPS enhanced acquisition of conditioned freezing, but did not enhance freezing during extinction training or testing. SPS also decreased avoidance during extinction training, but not extinction testing. In female rats, SPS had no impact on conditioned freezing. Avoidance was not observed in control rats, but emerged in SPS/female rats during extinction testing. Furthermore, avoidance was negatively correlated with freezing in female rats (high avoidance associated with lower freezing), but this relationship was disrupted with SPS. The results suggest that introducing avoidance during extinction negates SPS effects on extinction retention in male and female rats, control/female rats engage in avoidance to regulate fear expression, and this relationship is disrupted with SPS.

دراسة تأثير اضافة الزنجبيل المحلي كمضاد للنمو الميكروبي في لحم الدجاج المجمد

This study aimed to identify the effect of adding local ginger powder at a rate of 5, 7 and 10% and fresh local ginger at a rate of 7% on the numbers of pathogenic microbial in chicken meat discs manufactured in a laboratory and preserved under freezing conditions -12 °C for 15, 30 and 60 days. The bacteriological analysis conducted on the chicken frozen tablets included the total number of bacteria, coliform bacteria, Psychrotrophic bacteria, Staphylococcus aureus bacteria and numbers of fungi and yeasts. The results of bacteriological analysis indicated a decrease in most types of the numbers of pathogenic microbes in chicken meat discs preserved under freezing conditions at -12°C when adding concentrations of 5, 7 and 10% of ginger powder and fresh ginger at a rate of 7%. Where the inhibitory effect was on the total numbers of bacteria, coliform bacteria Psychrotrophic bacteria and Staphylococcus aureus bacteria, the number of fungi and yeasts at a concentration of 5% of dry ginger powder during the 15day storage period where a decrease was observed from 6.166, 4.873, 4.477, 5.493 and 4.814 log10 cfu/g to 5.985, 3.982, 2.229, 4.926 and 4.642 log10 cfu/g respectively. The resulted showed an increase in the frozen storage period to 30 days the microbial content had a significant effect at a significant level of P &lt; 0.05 as it was in the control treatment 5.655, 4.362, 5.638, 5.022 and 4.892 log10 cfu/g when adding dry ginger at a concentration of 5%, the numbers were 5.474, 3.741, 2.162, 4.527 and 5.031 log10 cfu/g respectively. It was observed that the total number of bacteria, coliform bacteria, Psychrotrophic bacteria, Staphylococcus aureus bacteria and numbers of fungi and yeasts increased in the control treatment at 60 day of frozen storage were 4.963, 4.537, 5.827, 4.676 and 4.472 log10 cfu/g, while when adding dry ginger at a concentration of 5%, inconstancy was seen in most of the pathogenic microbial numbers were 4.782, 3.692, 2.316, 3.746 and 4.738 log10 cfu/g respectively. The results also showed a decrease in most of the numbers of pathogenic bacteria by adding concentrations of 7 and 10% of dry ginger powder during 60 days on the total number of bacteria from 4.409 to 4.603log10 cfu/g and coliform bacteria from 3.978 to 3.833 log10cfu/g and Psychrotrophic bacteria from 2.116 to 1.151 log10cfu/g and Staphylococcus aureus bacteria from 4.424 and 3.967 log10 cfu/g and numbers of fungi and yeasts from 3.636 to 2.742 log10 cfu/g respectively. Also, the results showed that adding a concentration of 7% of fresh ginger during the storage period of 60 days had the highest inhibitory effect on the total numbers of bacteria, coliform bacteria Psychrotrophic bacteria and Staphylococcus aureus bacteria, the number of fungi and yeasts which recorded 4.084, 3.551, 1.962, 4.028 and 2.768 log10 cfu/g respectively compared to the control sample, which were 4.963, 4.537, 5.827, 4.472 and 4.676 log10 cfu/g respectively.

Corrosion inhibitors for enhanced strength, durability, and microstructure of coastal concrete structures

The prevalence of catastrophic structural member failure caused by steel corrosion in civil infrastructure underscores the importance of reducing reinforcement corrosion to enhance overall infrastructure costs, reliability, and sustainable development. The present research investigates the potential of corrosion inhibitors to enhance the durability and strength of concrete structures, with a focus on their long-term effectiveness in resisting corrosion in reinforced concrete structures. Multiple approaches such as inhibitors, repairing processes, and coatings have been explored to prevent concrete corrosion damage, with an emphasis on concrete corrosion performance in coastal and corrosive situations. This study investigates the effect of six different corrosion inhibitors (zinc oxide, magnesium oxide, urea, sodium nitrate, sodium molybdate, and diethyl ether) on the compressive strength and durability of concrete samples. The compressive strength is assessed using both destructive (28 days cube compressive strength) and non-destructive (Ultrasonic Pulse Velocity) test methods, while concrete durability is evaluated using the rapid chloride permeability test (RCPT). The compressive strength of the admixture incorporated samples are found to be higher than the control sample by almost 50% and above with excellent concrete quality. The RCPT values of inhibitor-incorporated samples are moderate and low with control samples having high permeability even in adverse conditions of freezing, thawing, and deicing. The samples incorporated with inhibitors also show less negative half-cell potential which is 1.43 times less than that of the control sample indicating the lesser probability of occurrence of corrosion. SEM imaging is also conducted to analyze the microstructure of each mix. The findings of this study highlight the importance of inhibitors in enhancing the durability of reinforced concrete structures.

Study of the Applicability of the Vyalov Long-Term Strength Prediction Equation under Freezing and Thawing Conditions

In order to determine the appropriate utilization conditions of the Vyalov long-term strength prediction equation, this study selected three soil samples from the loess region. These samples were subjected to varying numbers of freeze–thaw cycles, namely 0, 4, 6, 8, 10, 50, and 100 cycles. Subsequently, post-test soil samples underwent spherical template indenter press-in tests and grain size determinations. The experimental outcomes demonstrated that the Vyalov long-term strength prediction equation accurately reflected the long-term strength variations of frozen loess after 10 freeze–thaw cycles. A further analysis revealed that the stability of the soil samples’ grain composition played a vital role in ensuring the accuracy of the prediction equation. Notably, a highly significant positive correlation was observed between the silt content of the soil samples and the prediction equation parameter β. Moreover, employing the Vyalov long-term strength prediction equation after 10 freeze–thaw cycles yielded prediction results consistent with the freeze–thaw cycles–time analogy method for durations of 10, 20, and 30 years. This study is beneficial for the construction and operation of projects in loess areas.

Optimization of Winter Irrigation under Freeze–Thaw Conditions: A Case Study of the Yellow River Delta, China

Optimal winter irrigation may be an alternative method for controlling soil salinization under seasonal freezing and thawing conditions in the Yellow River Delta. However, few studies have focused on optimal winter irrigation based on the dynamics of soil water, heat, and salt during the freezing–thawing period in this region. Taking the seedling stage of winter wheat in the Yellow River Delta as the research object and using observation data of hydrothermal salt from the Shandong agricultural high-tech demonstration base from 17 October 2019 to 15 June 2021, a numerical simulation of the hydrothermal coupling process of freeze–thaw soil in the experimental area was carried out through the Simultaneous Heat and Water Model (SHAW). The simulation results of the model were evaluated according to the mean error (ME), root mean square error (RMSE), and Nash efficiency coefficient (NSE). The results showed that the SHAW can well simulate the soil moisture (SM), soil temperature, and soil salt during the growth of winter wheat in this region: the SM at the depth of 0–80 cm with an ME &lt; 0.038 cm3 cm−3, RMSE &lt; 0.064 cm3 cm−3, and NSE &gt; 0.669; the soil temperature with an ME &lt; 1.311 °C, RMSE &lt; 1.493 °C, and NSE &gt; 0.738; and the soil salinity with an ME &lt; 0.005 g kg−1, RMSE &lt; 0.014 g kg−1, and NSE &gt; 0.607. Moreover, the model was used to simulate the distribution of soil water and salt in the winter wheat seedling stage under different winter irrigation methods during wet, normal, and dry years. It was suggested that the appropriate winter irrigation amount was 80 mm in wet years and normal years and 100 mm in dry years, which could be beneficial to winter wheat growth during the seedling stage. These results provide a reference for irrigation optimization in the Yellow River Delta and other similar areas.

Prediction of Frost Heaving Stress in Saturated Sandstone in Unidirectional Freezing Conditions

Prediction of Frost Heaving Stress in Saturated Sandstone in Unidirectional Freezing Conditions