Stability of Particle size Improved Roadbed in Permafrost

Roadbed stability, including thermal and strength stability, is the ability of roadbed to adapt to pavement settlement, slurry effusion, shear slide and haunching up of the roadbed resulting from moving vehicles and many natural influences. Thermal stability is the sensitivity of the thermal state of the roadbed to the external environmental condition. It is the key point of the roadbed stability in permafrost. Research concerning roadbed thermal stability in permafrost is analyzed, and the judgment principle of thermal stability is discussed. The regular change of the ground temperature and deformation of particle size improved roadbeds are analyzed by studying field observation data of the particle size improved roadbed after two freezing and thawing cycles. We conclude that the particle size improved roadbed can raise the upper limit of frozen soil. Based on the judgment principle, the particle size improved roadbed is regarded as a new type of stable structure.     

Three-dimensional Random Damage Prediction Model of Concrete Caused by Freeze-thaw

In order to effectively assess the damage of concrete in freeze-thaw condition, prediction model for concrete frost damage is presented based on damage mechanical theory and the experimental test. The degeneration of tension strength of air-entraining concrete is tested after freezing and thawing. Provided with the fact that the degeneration of concrete is an interior damage evolving process, freezing and thawing damage accumulation of concrete is analyzed based on the discrete grid with probability of stochastic method. And Three-dimensional multi-parameters Weibull distribution model about concrete damage evolutions is presented. Parameters are estimated based on gradient method, and the mathematical model is verified according to the tested data. Corresponding algorithm is designed and programming is completed by C + + programming language to establish concrete durability prediction model under freeze-thaw conditions. It is indicated that the damage of concrete develops in nonlinear way as the freezing and thawing increases.     

Analysis on the Temperature-control Effect of the Particle Improved Roadbed in Qinghai-Tibet Railway

Based on the observerd ground-temperature data of the particle improved roadbed in Beiluhe test site of Qinghai-Tibet railway, the characteristics of the ground temperature to the particle improved roadbed and its temperature-control effect are analyzed ,and compared with other frozen soil protecting means. The result indicated that the ground temperature of the particle improved roadbed changes with the seasons,and its characteristics present as a sinusoidal curve. Compared with the normal roadbed, the paticle improved roadbed has cooling roadbed and the effect of protecting frozen soil in mean annual ground temperature. Compared with the normal duct-ventilation embankment, the cooling effect of the particle improved roadbed in cold season is less than that of the duct-ventilation roadbed,and the thermal shield effect is better than that of the particle improved roadbed in warm season. The ground temperature curve has the better tendency of the frozen soil protection. It is an active means of frozen soil protecton.     

Frost Heave Tests for the Bedding Materials of Face Rockfill Dam in Pushihe, P. R. China

To insure the safe performance of rockfill dam faces in cold seasons, frost tests were carried out at a consistent empirical freezing speed of 20mm/day to study the frost susceptibility of the bedding materials. The influence of gradation, fine particle content, water content, and surcharge of the bedding material on frost heaving were obtained. When fine particle content was below 12%, there was no or only weak frost heaving. Frost increased linearly as fine particle content rose. When the fine particle content was fixed, the linear relationship between the water content and the frost heaving changed with the gradations. Typical water content of 7.5%, fine particle content of 12%, and concrete face density of 59g/cm3 are suggested for the bedding material to avoid frost damage.     

Evaluation of Maize Germplasm for Tolerance to Low Temperature Stress under Field and Laboratory Conditions

Sixty-four inbred lines of maize ( Zea mays L.) were evaluated for their tolerance to low temperature stress in three experiments at Punjab Agricultural University, Ludhiana. All the 64 inbred lines were evaluated under laboratory conditions. Forty-four of these were also studied under field conditions. In the laboratory test the materials were exposed for four hours to 1, 0, −1, −2, −3 and −3.5°C on six successive nights. Significant genotypic differences were observed for freezing injury in laboratory test and for frost and non-freezing (yellowing) injuries in field evaluation. Expression of frost injury under field condition and freezing injury in laboratory test at −2, −3 and −3.5 °C showed positive correlation in one experiment. The range and mean square for freezing injury of inbred lines were the largest either at −3 or at −3.5°C. The correlation of yellowing with frost injury in field and freezing injury in laboratory at −3 and 3.5°C was not significant suggesting the lack of association between yellowing and frost/freezing injury.     

The freezing characteristics of wheat at ear emergence

Wheat is occasionally exposed to freezing temperatures during ear emergence and can suffer severe frost damage. Few studies have attempted to understand the characteristics of freezing and frost damage to wheat during late development stages.

It was clearly shown that wheat appears to have an inherent frost resistance to temperatures down to −5 °C but is extensively damaged below this temperature. Acclimation, whilst increasing the frost resistance of winter wheat in a vegetative state was incapable of increasing frost resistance of plants at ear emergence. It is proposed that the ability to upregulate frost resistance is lost once vernalisation requirement is fulfilled.

Culms and ears of wheat were able to escape frost damage at temperatures below −5 °C by supercooling even to as low as −15 °C and evidence collected by infrared thermography suggested that individual culms on a plant froze as independent units during freezing with little or no cross ice-nucleation strategies to protect wheat from frost damage in the field appear to revolve around avoiding ice nucleation.     

原状黄土冻融过程抗剪强度劣化机理试验分析

通过对西安Q₃原状黄土在封闭系统冻融作用下的电镜扫描和直剪试验,研究了冻融作用对原状黄土微观结构和强度的影响。试验表明：冻融过程中原状黄土微观结构发生显著变化,大颗粒集粒数量明显减少,小粒径土颗粒所占比重增加,孔隙面积比增加。进一步基于损伤力学理论,得到微观结构冻融损伤度随冻融次数增加呈指数增加趋势,反映出冻融作用一定程度上破坏黄土体的结构强度,但多次冻融后黄土体结构强度趋于稳定的残余强度。冻融过程土样表面结构发生破坏,且含水率越高,土体表面特征破坏越严重。粘聚力随冻融次数增加呈指数衰减趋势,且含水率越高,粘聚力衰减幅值和速率越小;粘聚力随含水率增加表现出线性衰减特征,且冻融后粘聚力与含水率的变化规律近似重合;内摩擦角无明显规律性变化。粘聚强度冻融损伤系数随冻融次数增加呈指数增加趋势,随含水率升高有增大趋势。基于试验数据规律性,进一步提出了原状黄土粘聚强度劣化模型,该模型经试验验证可较好描述原状黄土粘聚强度劣化规律。     

北方果树霜冻害远程监控与报警系统初步研究与实现

为提高北方果树防霜冻害管理水平,基于物联网架构,设计实现了北方果树霜冻害监测与报警系统。该系统结合实时获取果树生长环境数据,及果树霜冻害发生规律和专家知识库,为用户提供远程果树环境信息分析和霜冻害智能诊断服务。同时为满足不同生产条件需求,结合用户需求和环境状况,提供自动报警。根据用户随时随地获取信息的需求,基于多种网络技术等(如Internet、android等移动互联网),开发了可用于PC终端、移动终端(如智能手机、平板电脑等)多平台管理模式。通过提供现场综合远程实时监控、数据采集、网络传输、数据管理分析及报警预警等功能,系统实现了对果树生长的全方位多功能的远程监控与综合管理,有效提高了果树防霜冻害监控管理水平。     

电阻抗图谱法与电导法测定枣树枝条抗寒性的相关性

选育抗寒性强的品种是避免枣树受到低温气候伤害的最有效方法,因而,探寻测定枣树抗寒性的合适方法非常重要。以7个品种枣树1年生枝条为材料,利用电导率(EL)法和电阻抗图谱(EIS)法测定其抗寒性。研究了低温胁迫下枣树枝条EIS参数（单分布电路元素电阻率r、r₁;胞外电阻率r_e;胞内电阻率r_i;弛豫时间τ;弛豫时间分布系数ψ）的变化,并对比分析了2种方法测定枣树抗寒性结果的相关性,以期确定快速测定枣树抗寒性的最佳参数。结果表明：在低温胁迫下,随着处理温度的降低,枣树枝条的各EIS参数均减小。通过EIS参数胞外电阻率r_e和弛豫时间τ拟合估算的抗寒性与EL法测定的抗寒性呈显著正相关,相关系数分别为0.840和0.879。结果表明冷冻处理后EIS参数r_e和τ可以作为测定枣树抗寒性的参数。采用EIS法测定抗寒性省时、不需要温育、不破坏植株,具有更大的优越性。     

Stress Corrosion of Concrete Exposed to the Action of Freezing-thawing Cycles

Through the method of accelerated freezing-thawing and room-temperature corrosion, the stress corrosion of three kinds of concretes subjected to 5.0%MgSO4(in mass)solution was studied. The considered concretes include High Strength Concrete(HSC), High-Volume Mineral Admixture Concrete(HVMAC) and High Durable Concrete(HDC) added with high-volume mineral admixture, air-entraining agent, superplasticizer, fibers and expansion agent. The results showed that the relative dynamic elastic modulus of concrete went through strengthen and deterioration stages subjected to stress corrosion, whether the room temperature or freezing and thawing conditions. The length of time of these two stages are closely related with the experimental temperature. Freezing and thawing action significantly accelerated the process of sulphate stress corrosion damage. Under the action of freezing and thawing, stress corrosion strengthening the period length of HSC shorter 96%, deterioration section of the length of time shorter 88%, compared with the length of time at the corresponding room temperature. Deterioration section of the length of time of HVMAC is reduced by 98%, while the HDC reduced by 71%. The effect of freezing and thawing, HDC freezing-thawing cycles when the stress corrosion damage occurred were longer 1.5 times and 13 times than the HSC and HVMAC. Thus in the cold regions, HDC showed more resistance to sulfate stress corrosion.     

提高西门塔尔牛冷冻精液使用效果的研究

为提高西门塔尔牛冷冻精液的使用效果,从筛选稀释液配方、选择最佳解冻温度与解冻后保存温度三个方面进行了研究。实验结果表明：（1）通过比较三种冷冻精液保存稀释液对冷冻后精子活力的影响,表明稀释液Ⅲ和稀释液Ⅱ的保存效果均极显著优于稀释液Ⅰ的保存效果（P<0.01）,稀释液Ⅲ与稀释液Ⅱ间的保存效果差异不显著（P>0.05）（2）将牛细管冻精在不同温度、不同时间下进行解冻,解冻后精子活率随解冻温度升高（40℃~65℃）而升高,但高温下（80℃）解冻精子活率低于解冻温度为（40℃~65℃）（3）在两个温度范围进行精液解冻后保存试验,结果以（0℃~5℃）范围解冻后保存效果较好。     

Plant damage after freezing, and the frost resistance of varieties from the facultative and winter wheat observation nurseries

In the first experiments, studies were made on the survival % of fourwinter wheat varieties with good frost resistance and two with poor frostresistance, and on the degree of plant damage after freezing at –14 ^°C and –16 ^°C under phytotron conditions. In the secondexperiment the frost resistance of the varieties included in the 9^thFacultative and Winter Wheat Observation Nurseries (FAWWON) wasdetermined after freezing in the phytotron at – 15 ^°C. The scoresgave a good reflection of the variety ranking determined on the basis ofsurvival % and of the different effects of the two freezing temperatures. Onthe basis of the scores, the plants were divided into two groups for eachtreatment and each variety: plants which suffered frost damage (a score of2–3), and plants which suffered no frost damage (a score of 4–5).Twenty plants from each group were raised to maturity in pots. Theyield parameters of plants damaged by freezing at – 14 ^°C werereduced to a lesser extent than those frozen at –16 ^°C. Of the eightparameters tested, the reduction in the number of ears per plant andconsequently in the number of grains in the side ears, the grain mass andthe total grain yield, gave the clearest indication of the extent of plantdamage. The results of the second experiment indicated that in some casesthe frost resistance of the varieties could be predicted from the wheatproduction zone (e.g. varieties from Eastern Europe and Nebraska haveexcellent frost resistance), while in other zones winter hardiness and frostresistance depended rather on the country or on the breeding location.     

Use of chlorophyll fluorescence to evaluate the cold acclimation and freezing tolerance of winter and spring oats

The efficiency of the excitation capture by open Photosystem II (PSII) reaction centres was measured by the F_v/F_m ratios in a collection of winter and spring oats in order to assess the effects of hardening and freezing on the functionality of PSII and also the suitability of a chlorophyll fluorescence‐based method to screen oat cultivars for frost tolerance. A significant reversible decrease in F_v/F_m was found in all genotypes during acclimation to low, non‐freezing temperatures. F_v/F_m analysis appears to be an attractive test for the evaluation of frost tolerance in oats, being rapid, non‐invasive and capable of monitoring a trait related to a crucial stage in the acquisition of frost tolerance. It is more sensitive and precise than other standard methods and highly correlated with field‐evaluated frost damage. The measurements made during recovery 1 or 2 days after stress when the visual symptoms are not yet expressed, were especially advantageous because of the large variability in genotype response. The r‐values (close to 0.8) were reduced due to the non‐standard behaviour of the winter cultivar ‘Aintree’. The cold acclimation response of this genotype has been analysed in detail and the limits of artificial freezing tests are discussed.     

苦瓜多糖的测定方法研究

为开发和利用苦瓜多糖,选用苯酚硫酸法和蒽酮硫酸法测定苦瓜多糖的含量;比较不同成熟度苦瓜中多糖的含量差别;比较冻融法制备的苦瓜汁粉及苦瓜渣粉中多糖含量。结果显示,对同一种样品利用苯酚硫酸法和蒽酮硫酸法测定,测定结果分别为28.00%和29.25%,苯酚硫酸法测定结果更为准确合理,可作为苦瓜中多糖含量测定的首选方法;测定不同成熟度苦瓜的多糖含量,发现苦瓜成熟度越高,多糖含量越低,说明苦瓜生理成熟阶段,苦瓜多糖是重要的呼吸基质之一;利用冻融法制备的苦瓜汁粉多糖含量为31.25%,苦瓜渣粉多糖含量为28.64%,说明冻融法获得的苦瓜汁没有起到完全分离苦瓜多糖的作用。     

Genome-wide association study for frost tolerance in rapeseed/canola (Brassica napus) under simulating freezing conditions

Rapeseed/canola seedlings can be easily damaged by spring frost, which can rupture the cells and kill the plant. Genetic variations for frost tolerance have known to exist within rapeseed/canola gene pool. A genome-wide association study (GWAS) was conducted using 231 diverged rapeseed/canola germplasm to find the significant markers of the freezing tolerance traits. The genotypes were obtained from 21 countries and comprised of spring, winter and semi-winter growth types. The genotypes were evaluated in plant growth chamber under simulated freezing conditions. Highly significant genotypic variation was observed for the freezing tolerance. The best three freezing tolerant germplasms (Rubin, KSU-10, and AR91004) were winter type, while the four most freezing susceptible germplasms (Polo Canada, Prota, Drakkar, and BO-63) were all spring type. No geographical or growth habit type clusters were identified by structure analysis in this mixed population. One QTL was identified that was located on chromosome A02. Six freezing/abiotic stress tolerance genes have been identified in this study.     

气候变化对不同产区苹果安全越冬的可能影响

为科学评估气候变化对中国产区苹果安全越冬的影响,结合现有成果提出了分别表征果树初冬低温伤害风险、冬季持续性低温伤害风险、冬季极端低温危害风险和脱驯化期的低温伤害风险4个农业气象指标,利用1961—2015年中国苹果主产区的气象资料,分黄土高原、环渤海湾、黄河故道、西南高地和新疆5个产区,评估了气候变化对苹果安全越冬的可能影响。结果表明：苹果产区越冬期升温明显,霜冻日数和极端低温事件发生频次显著减少。初冬首次低温与初霜日间隔缩短导致渤海湾北部产区、黄河故道及北疆苹果的初冬低温伤害风险增加。越冬期持续性低温伤害风险和极端低温危害风险总体降低,特别是中高纬度表现明显,而黄土高原和新疆产区的极端低温事件发生的不确定性较大。同时黄土高原、辽宁、川西和北疆等产区苹果脱驯化期的低温伤害风险有所增加。总体上,苹果深度休眠期的冬季极端低温和持续性低温冻害风险有所降低,而初冬和脱驯化期低温冻害风险显著增加。     

Frost resistance of 'Chinese Spring'/'Cheyenne' chromosome substitution lines under short- and long-day hardening conditions

Investigations were carried out under phytotronic conditions to study the effect of daylength on the frost resistance of a ‘Chinese Spring’/‘Cheyenne’ chromosome substitution series. The frost resistance of the 5A, 7A, 4B, 5B, 1D and 5D lines was significantly better when raised and hardened with long-day (16 h) rather than short-day (8h) illumination. The frost resistance-increasing effect of daylength could be demonstrated after freezing lines 5A and 5D at both - 10°C and -12°C. An increase in the duration of illumination in the course of preliminary growth and hardening promoted the development of a higher level of frost resistance. This positive effect was most pronounced for chromosome substitution lines, where the frost resistance was significantly better than that of ‘Chinese Spring’ even with normal daylengths.     

Vegetative Performance of Tropical Highland Maize (Zea mays L.) in the Field

An attempt has been made to work out a simple and reliable method of fast frost resistance evaluation of winter oilseed rape using in vitro cultures. In winter rape cv. Górczański, there was investigated cold acclimation ability of hypocotyle sections from 5-days old seedlings and also of callus tissue formed on these sections after subsequent 4 weeks growth on induction medium. It has been found that hypocotyle sections are unable to cold-acclimate. Winter rape calli acclimated well and optimum conditions for acclimation is fortnight's growth at +2°C. Exposure to light during hardening was not necessary for acquiring maximum resistance. On five winter rape cultivars freezing tests were performed using the best cold acclimation conditions. The differences in resistance between hypocotyle sections did not match the differences in field survival or frost resistance of whole plants. As distinct from hypocotyle sections callus tissue appeared to be suitable for evaluation of frost resistance. However, to ensure the objectiveness of assessment in this method is not so easy. The testing temperature must be chosen carefully, because the results can be reliable only at sufficiently low temperature. For correct estimation of the frost resistance level, it is possible to use both the decrease of triphenyltetrazolium chloride reduction rate during freezing and the increase of callus dry weight during 14 days after freezing.
(Abbreviations: BAP — 6-Benzylaminopurine; 2,4-D — 2,4-dichlorophenoxyacetic acid; LT50 — temperature at which 50 % of the plants (or plant material) has been frost killed; MS(0.5;2) — Moorashige and Skoog Basic Medium with addition of 0.5 mg 2.4-D and 2 mg BAP; PPFD — photosynthetic photon flux density; TTC — 2,3,5 triphenyltetrazolium chloride)     

河套灌区籽用葫芦终霜冻指标研究

为了完善当地气象灾害指标,更好地开展籽用葫芦春霜冻气象服务,本研究选用籽用葫芦‘(丰产一号)’幼苗为试验材料,利用MSX-2F人工模拟霜箱系统模拟自然降温过程,通过测定幼苗的叶温记录植株冻伤、冻死情况,结合荧光参数值,综合确定河套灌区籽用葫芦终霜冻指标。结果表明：(1)籽用葫芦幼苗全部冻死的最低温度为≤-4℃;(2)籽用葫芦幼苗结冰点的范围为-0.2~-2.8℃之间,过冷却点的范围为-1.5~-4.5℃之间;(3)苗龄越大的籽用葫芦幼苗,耐受冻害的能力越强;(4)籽用葫芦幼苗轻霜冻地表温度指标为-1℃,重霜冻地表温度指标为-3℃。