Thermal–moisture dynamics and thermal stability of active layer in response to wet/dry conditions in the central region of the Qinghai–Tibet Plateau,China

The amount of rainfall varies unevenly in different regions of the Qinghai-Tibet Plateau, with some regions becoming wetter and others drier. Precipitation has an important impact on the process of surface energy balance and the energy-water transfer within soils. To clarify the thermal-moisture dynamics and thermal stability of the active layer in permafrost regions under wet/dry conditions, the verified water-vapour-heat coupling model was used. Changes in the surface energy balance, energy-water transfer within the soil, and thickness of the active layer were quantitatively analyzed. The results demonstrate that rainfall changes significantly affect the Bowen ratio, which in turn affects surface energy exchange. Under wet/dry conditions, there is a positive correlation between rainfall and liquid water flux under the hydraulic gradient;water vapour migration is the main form under the temperature gradient, which indicates that the influence of water vapour migration on thermalmoisture dynamics of the active layer cannot be neglected. Concurrently, regardless of wet or dry conditions,disturbance of the heat transport by conduction caused by rainfall is stronger than that of convection by liquid water. In addition, when rainfall decreases by 1.5 times(212 mm) and increases by 1.5 times(477 mm), the thickness of the active layer increases by 0.12 m and decreases by 0.21 m, respectively. The results show that dry conditions are not conducive to the preservation of frozen soil;however, wet conditions are conducive to the preservation of frozen soil, although there is a threshold value. When this threshold value is exceeded, rainfall is unfavourable for the development of frozen soil.

Changes in terrestrial surface dry and wet conditions on the Loess Plateau(China) during the last half century

This paper, using a revised Penman-Monteith model, computed the terrestrial surface humidity index of the Loess Plateau （China） based on climatic factors of monthly mean temperature, maximum temperature, minimum temperature, relative humidity, precipitation, wind speed and sunshine duration observed on the plateau from 1961 to 2008. The temporal-spatial distribution, anomaly distribution and sub-regional temporal variations of the terrestrial surface dry and wet conditions were analyzed as well. The results showed a decreasing trend in the annual average surface humidity from the southeast to the northwest in the research anna. Over the period of 1961-2008, an aridification tendency appeared sharply in the central interior region of the Loess Plateau, and less sharply in the middle part of the region. The border region showed the weakest tendency ol; aridification. It is clear that aridification diffused in all directions from the interior region. The spatial anomaly distribution of the terrestrial surface dry and wet conditions on the Loess Plateau can be divided into three key areas： the southern, western and eastern regions. The terrestrial annual humidity index displayed a significantly descending trend and showed remarkable abrupt changes from wet to dry in the years 1967, 1977 and 1979. In the above mentioned three key areas for dry and wet conditions, the terrestrial annual humidity index exhibited a fluctuation period of 3-4 years, while in the southern region, a fluctuation period of 7-8 years existed at the same time.

Asymmetric Drying and Wetting Trends in Eastern and Western China

As an important factor that directly affects agricultural production, the social economy, and policy implementation,observed changes in dry/wet conditions have become a matter of widespread concern. However, previous research has mainly focused on the long-term linear changes of dry/wet conditions, while the detection and evolution of the non-linear trends related to dry/wet changes have received less attention. The non-linear trends of the annual aridity index, obtained by the Ensemble Empirical Mode Decomposition(EEMD) method, reveal that changes in dry/wet conditions in China are asymmetric and can be characterized by contrasting features in both time and space in China. Spatially, most areas in western China have experienced transitions from drying to wetting, while opposite changes have occurred in most areas of eastern China. Temporally, the transitions occurred earlier in western China compared to eastern China. Research into the asymmetric spatial characteristics of dry/wet conditions compensates for the inadequacies of previous studies, which focused solely on temporal evolution;at the same time, it remedies the inadequacies of traditional research on linear trends over centennial timescales. Analyzing the non-linear trend also provides for a more comprehensive understanding of the drying/wetting changes in China.

Effects of Subsoiling on Some Soil Physical Properties and Wheat Yield in a Dry Land Ecological Condition

In order to evaluate the effect of subsoiling on the soil physical properties and wheat yield in dry land conditions, this research was conducted in Mamassani area of Fars province in Iran. The experiment was laid down in the form of a complete block experimental design with four treatments and four replications for three years. Treatments included： （1） conventional tillage without using subsoiler which was control treatment （So）; （2） using subsoiler with the shank space of 40 cm which was equal to the subsoiling depth （SO; （3） using subsoiler with the shank space of 60 cm which was 1.5 times of the subsoiling depth （S2）; and （4） using subsoiler with the shank space of 80 cm which was 2 times of the subsoiling depth （S3）. Subsoiling depth was set at 40 cm which was the lower limit of the hard pan depth in the soil. Soil cone index, soil bulk density, soil moisture content, wheat yield, and yield components were measured in this study and SAS software was used to analyze the collected data. Results showed that subsoiling decreased the soil bulk density and cone index, and increased water retention of the soil. Results also revealed that applying subsoiler increased wheat yield and yield components in our dry land conditions. Since subsoiling improved soil physical conditions and increases wheat yield, applying subsoiler in such a dry land conditions is therefore recommended. Results of this study also showed that subsoiling with the shank space of 40 cm and 60 cm had better performance compared to the shank space of 80 cm. On the other hand, shank space of 40 cm reduced the subsoiler effective working width and consequently effective field capacity. Therefore, subsoiler with a shank space of 60 cm is recommended for application in dry land soils of our type.

新型土壤改良剂对冬小麦生长及养分吸收的影响

通过对冬小麦施加一种以秸秆为主要原料研制的新型土壤改良剂(简称PJG),采用田间试验,探讨其对冬小麦生长、产量、各生长期养分含量及氮、磷累积吸收量的影响。结果表明:施加PJG土壤改良剂能提高小麦地上部各生长期干物质累积量,单施可提高8.4%,与氮肥配施可提高37.8%;可增加植株地上部各器官中氮、磷含量及其累积吸收量,但对钾素影响不大。施加1 500 kg/hm2的PJG改良剂,能较对照增产1.90%,与氮肥配施效果更佳,最高增产9.96%。综合考虑,应用PJG土壤改良剂时应与适量的氮肥配施,对作物的生长和产量的提高效果更佳。

不同土壤调理剂对韭菜酸性土壤的改良效果

为解决蔬菜基地土壤酸性化问题,恢复土壤的生产力,通过在韭菜酸性土壤上追施不同调理剂的小区试验,研究了BGA土壤调理剂、"田师傅"土壤调理剂和生石灰对土壤理化性质和韭菜生长发育的影响,评价不同土壤调理剂的施用效果。结果表明,调理剂对土壤pH的提高效果为生石灰>田师傅>BGA。BGA提高了土壤有效磷、有效钾和有机质含量,弥补了酸性土壤中钙、镁和硼的缺乏;田师傅调理剂能疏松土壤,使土质黝黑,提高有效氮、磷和钾含量;生石灰处理能提高有效氮和磷含量,降低有效钾含量。3种调理剂对防治韭菜干尖效果明显,提高了韭菜株高、茎粗、叶长叶宽,从而显著提高韭菜的产量,但对光合指标和品质影响不大。因此,3种调理剂都可在韭菜酸性土壤上推广应用。

环境工况对家用空调器性能的影响

通过试验的方法定量研究了环境工况对制冷系统性能的影响,得出了相应的试验曲线,并根据试验结果分析了室内湿球温度及室外干球温度的变化影响空调性能的规律。

R417A热泵空调换热器的温度分布特性

对一台以R417A为工质的热泵型房间空调换热器在不同室外干、湿球温度工况下的温度分布情况进行了试验研究和分析。通过对管翅式换热器温度分布规律的研究,找出其换热特性,在对试验结果进行综合分析的基础上,提出了优化设计建议。

Correlation Analyses between Ultraviolet Radiation, Global Solar Radiation, and Metrological Variables and the COVID-19 Cases in Arid Climate

The transmission of infectious diseases is influenced by several meteorological factors. In this study, the influence of several such factors in the transmission of COVID-19 (from 26 March 2020 to 29 July 2021) in the arid weather of Riyadh, Saudi Arabia was investigated using the Spearman and Kendall rank tests. The factors considered were the average, maximum, and minimum values of air temperatures, air pressure, wind speed, relative humidity, absolute humidity, dew point temperatures, and the average values of the global solar radiation and ultraviolet radiation at bands A and B. The data on meteorological factors were obtained from the King Abdulaziz City for Science and Technology (KACST) weather station, whereas the data on the daily COVID-19 cases were obtained from the official webpage of the Saudi Arabian Ministry of Health (MOH). The results revealed that air temperature (average, minimum, and maximum) average and maximum wind speed, maximum dew point temperature, global solar radiation, and ultraviolet radiation at A and B bands are positively associated with the daily number of COVID-19 cases reported in Riyadh. However, relative humidity, atmospheric pressure (averages, minimum, and maximum) is anti-correlated with the number of daily COVID-19 cases, while absolute humidity exerts no influence. These results are in total agreement with some of the previously established studies and are either contradicted partly or totally with others conducted at several locations around the world. The results could help not only epidemiologists understand the behavior of COVID-19 against meteorological variables but also national and international organizations and healthcare policymakers devise control strategies to combat the virus.

BGA土壤调理剂对木薯生长、产量及品质的影响

以木薯品种‘南植199’为试验材料,研究不同用量BGA土壤调理剂对木薯生长、产量及品质的影响。结果表明:施用280 kg/667 m2的BGA土壤调理剂和BGA 120 kg/667 m2与复合肥(15-15-15)27 kg/667 m2混施2种方式,均能有效促进木薯植株生长,显著提高鲜薯产量;BGA 120 kg/667 m2与复合肥(15-15-15)27 kg/667 m2混施,对木薯干物率和淀粉含量提高有显著效果。综合木薯生长情况、产量和品质等综合性状,以BGA 120 kg/667 m2与复合肥(15-15-15)27 kg/667 m2混施效果最佳。

基于性能曲面特性的干湿球温度允差等级划分

在试验结果的基础上,分析制冷量和能效比随干湿球温度的变化特性。用赤池信息量准则(Akaike information criterion,AIC)选取制冷量和能效比最优拟合三维曲面方程,求解制冷量和能效比随干湿球温度变化的梯度极值区间,以两者梯度极值区间内干湿球温度允差范围的并集为A级、现行干湿球温度允差为C级,以各级最大(最小)能效比变化率相等原则,对允差进行三级非线性划分。实例表明随着允差等级的升高,能效比最大变化率由5.19%缩减至1.04%,分级允差能够更加准确地判别房间空调器的能效等级,并给国家标准的修订提供参考。

环境干湿球温度对空调器性能影响的试验研究

在一款整机型号为KFR-90WT1-520的某品牌空调器上,进行了环境干湿球温度对空调器性能影响的试验,得出了相应的试验结果与试验曲线。结果表明,空调器的性能受室外干球温度和室内湿球温度的影响,室内侧湿球温度和室外侧干球温度的变化对空调器运行性能影响较大,而室内侧干球温度和室外侧湿球温度的影响则稍小。

云南干热河谷区木薯应用BGA土壤调理剂初报

为研究BGA土壤调理剂对云南干热河谷区木薯生长的作用,以木薯品种华南205为试验对象,开展了不同用量BGA土壤调理剂对该区域木薯的影响研究。研究结果表明,BGA土壤调理剂能够促进木薯生长,在云南干热河谷区,对华南205木薯,综合其生长情况、产量和品质等性状,一次性施用1 200 kg/hm^2BGA土壤调理剂是最佳的处理。

BGA土壤调理剂对旱作马铃薯产量与品质的影响

为了探讨BGA土壤调理剂施入对马铃薯产量和品质的影响,进行了BGA土壤调理剂、PF施肥和CK（对照）处理比较研究。结果表明：BGA土壤调理剂的施入可使马铃薯的生殖生长阶段提前5 d左右,延迟了马铃薯的成熟时期。BGA土壤调理剂处理后马铃薯不同生育时期的株高比CK增加19.99%~46.78%,冠幅比CK增加21.17%~24.26%,马铃薯产量较CK增产了47.6%,虽然产量较PF降低了12.8%,但商品薯产量相差不大,因此也就避免了马铃薯增产不增收的现象发生;BGA土壤调理剂施入后,延迟了马铃薯的成熟期,造成马铃薯的品质下降,但与生育期相差不大的PF相比,马铃薯的干物质、粗蛋白、总糖和还原糖含量都有所提高。

Wear Performance of Laser Surface Hardened GCr15 Steel

In order to assess the new tribological properties of laser surface hardened GCr15 steel, the wear resistance between specimens treated with laser and those of conventionally hardened under dry sliding conditions was compared. The change of wear mechanisms in laser hardened GCr15 resulted in a distinct difference in wear rates. The results showed that quenched zones not only had sufficient depth of hardening and higher hardness, but had more retained austenite and finer carbides because of a higher degree of carbide dissolution. Laser surface hardened GCr15 steel specimens exhibited superior wear resistance to their conventionally hardened specimens due to the effects of the microstructure hardening, high hardness and toughness. The wear mechanism for both the laser quenched layer and conventionally hardened layer was highly similar, generally involving adhesive, material transfer, wear-induced oxidation and plowing. When conventionally hardened block specimens rubbed against the laser hardened specimens, the surface of conventionally hardened block specimens was polished. The microstructural thermal stability was increased after laser surface treatment.

辐射与对流耦合空调系统及室内环境对比分析

辐射板与干式风机盘管耦合是一种新型的末端形式,本文基于温湿度独立控制改进了这种空调系统。该系统有效地解决夏热冬冷地区全天负荷波动较大辐射空调供冷不足的弊端而且避免了能源的冗余浪费。通过CFD软件模拟对比分析了三种典型空调系统和该耦合空调系统下的室内温度和气流组织情况,由此确认了该耦合空调系统在工程实际应用的可行性和优越性。

Optimization of drying conditions and components to reduce wall sticking during spray drying of infant formula milk

Wall sticking,which greatly reduces productivity and product quality,has been a big challenge of spray drying.Structure of drying tower and atomizer,as well as drying conditions are the main influencing factors.This research explored the possibility to reduce wall sticking by optimizing drying conditions and components to obtain higher recovery rate of powdered infant formula milk(PIFM).Response surface experimental results indicated that inlet air temperature(T),feed concentration(C),feeding speed(S),as well as interaction term of TC and quadratic terms of C^(2) and S^(2) had significant influences on recovery rate for determined milk formula.According to mixture experiments at optimized drying conditions,whey protein(P),fat(F)and lactose(L)contents,as well as interaction term FL had significant effects on recovery rate.Positive effects were observed for F and L contents on recovery rate,while negative effects were observed for P and FL.Under the optimized drying condition of 136℃,19.80%and 4.07 mL/min,respectively,for T,C and S,the maximum recovery rate of 58.98%was obtained for PIFM with P,F and L content of 18%,31%and 51%,respectively.Wall sticking phenomena could be reduced by optimizing drying conditions and mildly adjusting components of infant formula milk.

Sliding wear behaviors of Nomex fabric/phenolic composite under dry and water-bathed sliding conditions

A Nomex fabric/phenolic composite was prepared,and its tribological properties were evaluated under dry and water‐bathed sliding conditions by a pin‐on‐disk tribometer.The resulting size of the friction coefficient for the Nomex fabric/phenolic composite in the study occurred in the following order:dry sliding condition>distilled water‐bathed sliding condition>sea water‐bathed sliding condition.The fabric composite’s wear rate from high to low was as follows:distilled water‐bathed sliding condition>sea water‐bathed sliding condition>dry sliding condition.Under water‐bathed sliding conditions,penetration of water into the cracks accelerated the composite’s invalidation process,resulting in a higher wear rate.We also found that the extent of corrosion and transfer film formed on the counterpart pin significantly influenced the wear rate of the Nomex fabric composite.Discussion of the Nomex fabric composite’s wear mechanisms under the sliding conditions investigated is provided on the basis of the characterization results.

跨临界CO_(2)蒸气压缩式制冷与热泵技术综述

CO_(2)跨临界制冷循环模式因环境友好性、高温制热性、低环境温度适应性、全工况范围高效性等众多优势成为制冷领域中最热门的研究课题之一。本文分别讨论了跨临界CO_(2)制冷或热泵技术在车辆空调、建筑采暖与热水供应、烘干产业、商超冷链等行业中的发展现状,总结并预测了跨临界CO_(2)技术的未来发展趋势。CO_(2)制冷技术在车辆热管理领域发展前景广阔,制热能力明显优于采用R134a、R407C、R1234yf等制冷剂的方案,但制冷性能及整车综合热管理技术还有待进一步研究提升;在建筑采暖与热水供应领域,跨临界CO_(2)技术的开发已较为完备,针对不同的温度需求有不同的结构优化方案,下一步研究将主要针对现有成熟技术的产业化而开展;烘干产业中的跨临界CO_(2)技术正在快速进步的过程中,虽然分布式小型烘干设备的新能源化改造任重道远,但节能与环保优势显著的跨临界CO_(2)技术仍具备优异的推广前景;跨临界CO_(2)技术在商超冷链中的Booster技术已较为成熟,优良的节能环保优势也进一步将该技术推向冰雪场馆制冷领域,在该领域中跨临界CO_(2)技术的冷热综合应用将是下一阶段的主要研究方向。喷射器、涡流管、膨胀机等压力能回收技术的深入研究是提升系统能效的重要方法,而智能控制技术是跨临界CO_(2)系统实时性能优化的必要保障,这两方面将成为下一阶段跨临界CO_(2)技术研究的主要任务。

Corrosion Behavior of Weathering Test Steel for Bridge Under the Neutral Wet/Dry Alternate Condition

The corrosion behaviors of the high-performance weathering test steel for bridge and the reference (09CuPCrNi-A) were symmetrically studied under 3.5% NaCl neutral wet/dry alternate condition,revealing their dynamics line tendency of primary corrosion and the rusting flow in the simulative marine atmosphere environment.By observing the corrosion evolution of surface microstructures and composition by the scanning electronic microscope (SEM) and the energy dispersive spectrometer (EDS) at the different stages,the corrosion mechanism was further discussed in details.