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.

A thermal stress loading technique for large-sized hot dry rock mechanical tests

Testing of large-sized specimens is becoming increasingly important in deep underground rock mechanics and engineering.In traditional mechanical loading,stresses on large-sized specimens are achieved by large host frames and hydraulic pumps,which could lead to great investment.Low-cost testing machines clearly always have great appeal.In this study,a new approach is proposed using thermal expansion stress to load rock specimens,which may be particularly suitable for tests of deep hot dry rock with high temperatures.This is a different technical route from traditional mechanical loading through hydraulic pressure.For the rock mechanics test system of hot dry rock that already has an investment in heating systems,this technology may reduce the cost of the loading subsystem by fully utilizing the temperature changes.This paper presents the basic principle and a typical design of this technical solution.Preliminary feasibility analysis is then conducted based on numerical simulations.Although some technical details still need to be resolved,the feasibility of this loading approach has been preliminarily confirmed.

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.

A STUDY OF PARTITIONING Q VECTOR ON BACKGROUND CONDITIONS OF A TORRENTIAL RAINFALL OVER SHANGHAI,CHINA ON 25 AUGUST 2008

A rainfall that occurred during 0200–1400 Beijing Standard Time(BST)25 August 2008 shows the rapid development of a convective system,a short life span,and a record rate of 117.5 mm h-1for Xujiahui station since 1872.To study this torrential rainfall process,the partitioning method of Q vector is developed,in which a moist Q vector is first separated into a dry ageostrophic Q vector(DQ)and a diabatic-heating component.The dry ageostrophic Q vector is further partitioned along isothermal lines in the natural coordinate to identify different scale forcing in adiabatic atmosphere,and the large-scale and convective condensational heating in non-uniform saturated atmosphere,convective condensational heating, and Laplace of diabatic heating that includes radiative heating and other heating and cooling processes,are calculated to study the forcing from diabatic heating.The effects of the environmental conditions on the development of the rainfall processes are diagnosed by performing the partitioning of Q vector based on 6-hourly NCEP/NCAR Final Analysis(FNL)data with the horizontal resolution of 1°×1°.The results include the following:(1)a low-pressure inverted trough associated with the landfall of Typhoon Nuri (2008),a strong southwesterly jet along the western side of the subtropical high,and an eastward-propagating westerly low-pressure trough provide favorable synoptic conditions for the development of torrential rainfall;(2)the analysis of DQ vector showed that the upward motions forced by the convergence of DQ vector in the lower troposphere(1000–600 hPa)favor the development of torrential rainfall.When DQ vector converges in the upper troposphere(500–100 hPa),upward motions in the whole air column intensify significantly to accelerate the development of torrential rainfall;(3)the partitioning analysis of DQ vector reveals that large-scale forcing persistently favors the development of torrential rainfall whereas the mesoscale forcing speeds up the torrential rainfall;(4)the calculations of large-scale condensational heating in non-uniform saturated atmosphere,convective condensational heating, and Laplace of diabatic heating showed that the forcing related to diabatic heating has the positive feedback on the convective development,and such positive feedback decays and dissipates when the convective system propagates eastward and weakens.

Biogenic Amines Profile of Serbian Traditional Sausage in Relation to Raw Material and Production Conditions

Petrovska klobasa is a traditional dry fermented sausage produced in the Autonomous Province of Vojvodina. Formation of nine hiogenic amines was determined in three sausage groups produced from hot deboned （A1） and cold meat （B1, B3） during drying and ripening in traditional room （A1, B1） and in industrial ripening chamber （B3）. Dansyl chloride derived amines were analysed by high-performance liquid chromatography with diode-array detector （HPLC-DAD） on Eclipse XDB-C18 column. Histamine, the most important amine from food safety point of view, was not found in any of the analyzed samples. Serotonin and spermidine were also not detected in any samples, while spermin was determined in all analyzed samples. At the end of drying, phenylethylamine was the predominant amine in A1 sausage group （51.6 mg/kg）, and tryptamine in B1 （38.1 mg/kg） and B3 （28.7 mg/kg） sausage groups. At the end of ripening, tryptamine was the predominant biogenic amine in all sausage groups （133, 121 and 39.8 mg/kg in A1, B1 and B3 groups, respectively）. Total level of biogenic amines in all investigated sausages did not exceed 174 mg/kg at the end of drying and 238 mg/kg at the end of ripening period. Tryptamine and cadaverine may be used as indicators of total biogenic amines for sausages produced in traditional and indusrial conditions from hot deboned and cold meat.

不同贮藏温度及包装条件对乌天麻干片挥发性气味的影响

采用电子鼻及吹扫捕集-气相色谱-质谱联用技术(purgeand trap-gaschromatography-massspectrometry,PT-GC-MS)分析3个贮藏温度(10、25、40℃)及4种包装条件(空气、N_(2)、CO_(2)、脱氧)对乌天麻干片的挥发性气味的影响。结果表明:在120 d的贮藏期内,不同温度及包装下的乌天麻干片挥发性气味存在一定的差异。温度是影响贮藏期乌天麻干片挥发性气味最主要的因素,低温更有利于保持乌天麻干片挥发性成分。其次是包装条件,在同一温度条件下,脱氧处理更有利于保持乌天麻干片的挥发性气味。随着贮藏时间的延长,不同温度及包装条件下,乌天麻干片中挥发性物质在种类和含量上均发生变化,在120 d贮藏期内,10℃脱氧处理组共检测出挥发性成分29种,总含量为214.52μg/g,醇类占总挥发性成分的54%;酯类占总挥发性成分的14%;烷烃类占总挥发性成分的10%;与对照组的挥发性成分最为接近。综上所述,10℃脱氧包装为乌天麻干片最佳贮藏条件,在该条件下贮藏,乌天麻干片的风味成分损失最小,可在较长贮藏期内有效保留乌天麻干片的风味成分。

切片厚度和护色处理对热风干燥雪花梨干品质的影响

采用热风干燥法制备雪花梨干。以色泽、硬度、弹性、咀嚼性、总酚、总黄酮、可溶性糖和感官评分为评价指标,考察切片厚度(3、4、5、6、7、8 mm)和护色处理(CaCl_(2)、NaCl、D-异抗坏血酸钠、柠檬酸溶液浸泡、热烫)对梨干品质的影响,并以Z-score(Z值)综合模型进行评价,优选出适宜的切片厚度和护色处理。结果表明:随着切片厚度的增加,梨干的颜色变深,硬度、弹性和咀嚼性增大,总酚和总黄酮含量降低,可溶性糖含量增加;Z-score综合模型评价结果显示,切片厚度为4 mm时,Z值总和最高。护色处理均能改善梨干色泽,提高总酚和总黄酮含量,但可溶性糖含量降低。D-异抗坏血酸钠处理组梨干的亮度值(L^(*))最高,红绿值(a^(*))和蓝黄值(b^(*))最低,色差值(ΔE)最小;CaCl_(2)处理提高了梨干的硬度;热烫处理降低了梨干的弹性和咀嚼性。Z-score综合模型评价结果显示,以0.8 g/100 mL D-异抗坏血酸钠溶液浸泡护色的Z值总和最高。综上,热风干燥制备雪花梨干的厚度和护色条件为:切片厚度4 mm、0.8 g/100 mL D-异抗坏血酸钠溶液浸泡10 min。

适用于法庭科学毒物分析的干血斑检验体系的建立——以5种常见药(毒)物为例

干血斑技术能够方便地对血液样品中的违禁药物进行快速分析,在酒后驾驶检查、滥用药物检测、兴奋剂检测等毒物分析场景具有显著优势。然而在我国法庭科学毒物分析领域,因缺少标准化检验体系,其稳定性和可靠性未得到深入研究论证,限制了其在司法实践中的运用。本研究以甲基苯丙胺、利多卡因、氯胺酮、芬太尼和地西泮为典型药(毒)物,使用整个干血斑进行分析,建立了适用于法庭科学领域毒物分析的超高效液相色谱-串联质谱分析方法,形成了以干血斑样品制作、前处理、分析、储存和效用性评价为主要内容的检验体系,并为干血斑中其他药(毒)物的分析方法开发提供参考。结果表明,干血斑中利多卡因和芬太尼在0.5~100 ng/mL内线性关系良好,甲基苯丙胺、氯胺酮、地西泮在2~100 ng/mL内线性关系良好,方法检出限为0.2~0.5 ng/mL。干血斑中5种目标物可以在60天内保持稳定,目标物测定含量与理论值的偏差在15%以内。干血斑中5种目标物的测量结果与全血一致,没有显著的系统误差和比例误差,芬太尼、地西泮、氯胺酮、利多卡因和甲基苯丙胺的测量浓度的相对偏差分别为4.44%、3.50%、7.66%、5.10%和5.25%。干血斑样品前处理方法简单,样品用量小,能够实现血液样品保存的轻量化和规范化且与全血样品具有高度定量一致性,可为公安实践工作中分析、保存血液检材提供新方案。

风干肉不同条件贮藏品质研究

目的:探究风干肉的加工优化方案及不同条件贮藏对风干肉品质的影响。方法:以风干肉猪肉为研究对象,探究不同包装方式、不同贮藏温度对风干肉贮藏特性的影响。结果:随着贮藏时间的延长,不同包装方式下的风干肉的过氧化值(Peroxidation Value,POV)和菌落总数呈现上升趋势,pH值先降低后升高。与普通包装相比,气调包装和真空包装可以较好地保持风干肉的质量,其中真空包装的风干肉贮藏时间更长。4℃贮藏的风干肉品质变化较为缓慢,25℃和40℃贮藏的风干肉品质变化加快,其中40℃贮藏的风干肉保质期最短。结论:风干肉采用真空包装在4℃下贮藏有利于保障风干肉的品质。

Prevalence and risk factors of dry eye disease in young and middle-aged office employee:a Xi’an Study

AIM:To estimate the prevalence of and risk factors for dry eye disease(DED)in young and middle-aged office employee in Xi’an.METHODS:This cross-sectional study of the prevalence of and risk factors for DED investigated 486 young and middle-aged Chinese office employee in Xi’an.DED symptoms and potential risk factors were assessed using the ocular surface disease index combined with a risk factors questionnaire,and tear function was evaluated using the tear film break-up time and Schirmer’s test.Possible risk factors for DED were estimated by binary Logistic regression analysis.RESULTS:DED was diagnosed in 100 females and 96 males,giving a prevalence of 40.3%[95%confidence interval(CI)=36.0%-44.7%].The multivariate binary Logistic regression model indicated that the possible risk factors for DED were being female(OR=1.592,95%CI=1.034-2.451,P=0.035),being aged≥40 y(OR=1.593,95%CI=1.034-2.454,P=0.035),using a VDT daily for>6 h(OR=1.990,95%CI=1.334-2.971,P=0.001),the presence of central air conditioning(OR=1.548,95%CI=1.053-2.276,P=0.026),and self-reported dryness of the mouth and nose(OR=1.589,95%CI=1.071-2.357,P=0.021).CONCLUSION:There is a high prevalence of clinically diagnosed DED in young and middle-aged video displayterminal(VDT)users.Interventions against the modifiable risk factors should be taken to prevent the occurrence and development of DED in this population.

Analysis and Modeling of Wangqing Oil Shale Drying Characteristics in a Novel Fluidized Bed Dryer with Asynchronous Rotating Air Distributor

In order to replace the conventional distributor, a novel asynchronous rotating air distributor, which can optimize the drying ability of fluidized bed and strengthen the drying performance of oil shale particles, is creatively designed in this study. The rotating speed of the asynchronous rotating air distributor with an embedded center disk and an encircling disk is regulated to achieve the different air supply conditions. The impacts of different drying conditions on the drying characteristic of Wangqing oil shale particles are studied with the help of electronic scales. The dynamics of experimental data is analyzed with 9 common drying models. The results indicate that the particles distribution in fluidized bed can be improved and the drying time can be reduced by decreasing the rotating speed of the embedded center disk and increasing the rotating speed of the encircling disk. The drying process of oil shale particles involves a rising drying rate period, a constant drying rate period and a falling drying rate period. Regulating the air distributor rotating speed reasonably will accelerate the shift of particles from the rising drying rate period to the falling drying rate period directly. The two-term model fits properly the oil shale particles drying simulation among 9 drying models at different air supply conditions. Yet the air absorbed in the particles' pores is diffused along with the moisture evaporation, and a small amount of moisture remains on the wall of fluidized bed in each experiment, thus, the values of drying simulation are less than the experimental values.

季也蒙毕赤酵母MCJ-1培养条件优化及其冻干菌粉的制备

康普茶是一种酸甜味发酵饮料,由酵母、糖和发酵茶制成。该研究以从康普茶混菌体系中筛选获得的季也蒙毕赤酵母(Pichia guilliermondii)MCJ-1为研究对象,采用单因素试验及响应面法优化菌株MCJ-1的培养条件,并制备其冻干菌粉。结果表明,菌株MCJ-1的最佳培养条件为:蔗糖25.00 g/L,氯化铵7.7 g/L,蛋白胨10.00 g/L,酵母浸粉5.00 g/L,培养温度30℃,初始pH值为6,转速200 r/min。在此优化培养条件下,菌体干质量为(5.06±0.22)mg/mL,比优化前提高了64.82%。菌粉制备中菌泥与保护剂的比例为1:1,保护剂甘油添加量为4.0%,可以获得存活率达(80.83±5.36)%的冻干菌粉。

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.

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.

Amorphous particle deposition and product quality under different conditions in a spray dryer

Deposition of amorphous particles, as a prevalent problem particularly in the spray drying of fruit and vegetable juices, is due to low-molecular-weight sugars and is strongly dependent on the condition of the particles upon collision with the dryer wall. This paper investigates the condition of the amorphous particles impacting the wall at different drying conditions with the aim of elucidating the deposition mechanism and physical phenomena in the drying chamber. A model sucrose-maltodextrin solution was used to represent the low-molecular-weight sugar. Particle deposits were collected on sampling plates placed inside the dryer for analyses of moisture content, particle rigidity (using SEM) and size distribution. Moisture content was adopted as a general indicator of stickiness. Product particles collected at the bottom of the experimental dryer were found to have higher moisture than particle deposits on samplers inside the dryer. Moisture content profile in the dryer shows that apart from the atomizer region, where particles are relatively wet, particle deposits at other regions exhibit similar lower moisture content. At the highest temperature adopted in the experiments, particles became rubbery suggesting liquid-bridge formation as the dominant deposition mechanism. Further analysis on particles size distribution reveals a particle segregation mechanism whereby smaller particles follow preferentially to the central air stream while larger particles tend to re-circulate in the chamber, as predicted in past CFD simulation. The findings from this work will form the basis and provide validating data for further modeling of wall deposition of amorphous particles in spray drying using CFD.

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.

不同复水条件对闽笋干质构特性的影响

目的:研究不同复水条件对闽笋干质构特性的影响。方法:采用预煮和热泡处理方式对闽笋干进行复水,通过质构仪测定分析不同热处理条件下闽笋干的硬度、弹性和咀嚼性的变化规律。结果:不同的热处理方式对笋干质构特性的影响有一定差异,在预煮20~60 min时,闽笋干的硬度和咀嚼性都显著降低(p <0.05),弹性则在预煮60 min时上升到0.88 g;经热泡处理后,闽笋干硬度呈先下降后上升的趋势,而弹性变化趋势与硬度相反。笋干在预煮60 min、热泡4 h条件下显示出最低的硬度和最高的弹性,咀嚼性基本维持在8 830左右,明显低于预煮组。相关性分析表明,硬度与咀嚼性呈显著正相关(p <0.01)。结论:笋干在预煮60 min、热泡4 h后具有良好的质构特性,能更好地反映笋干质地,可为笋干工业化复水研究以及烹调过程提供科学依据。

不同高温热泵干燥条件对龙眼干品质的影响

以龙眼为研究对象,考察了不同热泵干燥温度和干燥风速对龙眼干一般理化特性、色泽、质构和活性成分等品质的影响。结果表明:采用高温热泵干燥时,干燥温度越高,龙眼干的总酸含量越高,复水率越低;干燥风速相同时,龙眼干的pH值随着温度的升高而降低;龙眼干燥后总体色泽的变化主要在色泽的变暗及变黄,干燥温度的升高和干燥风速的增加都会导致龙眼色泽变化的增加;总体来说,不同高温热泵干燥条件下,龙眼干的弹性、回复性、硬度以及耐咀性的变化均不显著,干燥风速较低,龙眼干的黏性较大;当干燥温度为60℃时,龙眼干中保留的游离酚含量最高,不同干燥条件下,结合酚含量、多糖含量的差异不显著。