Change in Grain-Size Composition of Lignite under Cyclic Freezing-Thawing and Wetting-Drying

The paper presents the change in grain-size composition of lignite under cyclic freezing-thawing (FTC) and wetting-drying (WDC). The article shows that in the spring and autumn periods the lignites can be subjected to repeated freezing-thawing and wetting-drying, which determines the possibility of changing their grain-size composition and structure. Experimental studies in laboratory conditions on the influence of cyclic freezing-thawing (FTC) and wetting-drying (WDC) on the quality indicators of lignites have been carried out, their granulometric (fractional) composition has been studied. Freezing-thawing cycle conditions are as follows (FTC): minimum exposure temperature: -20°C;maximum: +5°C;relative humidity: 30%;number of processing cycles: 3. Wetting-drying cycles are as follows (WDC): drying temperatures are +20, +40, +60, +80°C, drying time 90 minutes, the coals are further subjected to rain (soaking) for a period of water saturation to humidity of 30% - 40% and dry again. The number of wetting-drying cycles is 3 times. The tests have revealed the destructive effects of FTC and WDC on the samples of lower metamorphic grade coal, and the cycles of wet-dry lead to the much higher yield of fine sizes (-6+0;-13+0 mm) than the cycles of freeze-thaw. Furthermore, it is found that the increase in the yield of fines depends on the heating temperature: coal disintegration proceeds more intensively at a higher temperature of drying.

Moderate wetting and drying increases rice yield and reduces water use, grain arsenic level, and methane emission

To meet the major challenge of increasing rice production to feed a growing population under increasing water scarcity,many water-saving regimes have been introduced in irrigated rice,such as an aerobic rice system,non-flooded mulching cultivation,and alternate wetting and drying(AWD).These regimes could substantially enhance water use efficiency(WUE) by reducing irrigation water.However,such enhancements greatly compromise grain yield.Recent work has shown that moderate AWD,in which photosynthesis is not severely inhibited and plants can rehydrate overnight during the soil drying period,or plants are rewatered at a soil water potential of-10 to-15 k Pa,or midday leaf potential is approximately-0.60 to-0.80 MPa,or the water table is maintained at 10 to 15 cm below the soil surface,could increase not only WUE but also grain yield.Increases in grain yield WUE under moderate AWD are due mainly to reduced redundant vegetative growth;improved canopy structure and root growth;elevated hormonal levels,in particular increases in abscisic acid levels during soil drying and cytokinin levels during rewatering;and enhanced carbon remobilization from vegetative tissues to grain.Moderate AWD could also improve rice quality,including reductions in grain arsenic accumulation,and reduce methane emissions from paddies.Adoption of moderate AWD with an appropriate nitrogen application rate may exert a synergistic effect on grain yield and result in higher WUE and nitrogen use efficiency.Further research is needed to understand root–soil interaction and evaluate the long-term effects of moderate AWD on sustainable agriculture.

Grain yield and water use efficiency of super rice under soil water deficit and alternate wetting and drying irrigation

This study investigated if super rice could better cope with soil water deficit and if it could have better yield performance and water use efficiency （WUE） under alternate wetting and drying （AWD） irrigation than check rice. Two super rice cultivars and two elite check rice cultivars were grown in pots with three soil moisture levels, well watered （WW）, moderate water deficit （MWD） and severe water deficit （SWD）. Two cultivars, each for super rice and check rice, were grown in field with three irrigation regimes, alternate wetting and moderate drying （AWMD）, alternate wetting and severe drying （AWSD） and conventional irrigation （CI）. Compared with that under WW, grain yield was significantly decreased under MWD and SWD treatments, with less reduction for super rice than for check rice. Super rice had higher percentage of productive tillers, deeper root distribution, higher root oxidation activity, and greater aboveground biomass production at mid and late growth stages than check rice, especially under WMD and WSD. Compared with CI,AWMD increased, whereasAWSD decreased grain yield, with more increase or less decrease for super rice than for check rice. Both MWD and SWD treatments and eitherAWMD orAWSD regime significantly increased WUE compared with WW treatment or CI regime, with more increase for super rice than for check rice. The results suggest that super rice has a stronger ability to cope with soil water deficit and holds greater promising to increase both grain yield and WUE by adoption of moderate AWD irrigation.

Influence of Seed Priming on Performance and Water Productivity of Direct Seeded Rice in Alternating Wetting and Drying

Direct seeded rice is promising alternative to traditional transplanting, but requires appropriate crop and water management to maintain yield performance and achieve high water productivity. Present study evaluated the effect of seed priming and irrigation on crop establishment, tillering, agronomic traits, paddy yield, grain quality and water productivity of direct seeded rice in alternate wetting and drying （DSR-AWD） in comparison with direct seeded rice at field capacity （DSR- FC）. Seed priming treatments were osmo-priming with KCI （2.2%）, CaCI2 （2.2%） and moringa leaf extracts （MLE, 3.3%） including hydro-priming as control. Among the treatments, seed osmo-primed with MLE emerged earlier and had higher final emergence, followed by osmo-priming with CaCI2. Tillering emergence rate and number of tillers per plant were the highest for seed priming with CaCI2 in DSR- AWD. Total productive and non-productive tillers, panicle length, biological and grain yields, harvest index were highest for seed priming with MLE or CaCI2 in DSR-AWD. Similarly, grain quality, estimated in terms of normal grains, abortive and chalky grains, was also the highest in DSR-AWD with MLE osmo-priming. Benefit cost ratio and water productivity was also the highest in DSR-AWD for seed priming with MLE. In conclusion, seed priming with MLE or CaCI2 can be successfully employed to improve the direct seeded rice performance when practiced with alternate wetting and drying irrigation.

Modeling the effect of wetting on the mechanical behavior of crushable granular materials

It is well known that the compressibility of crushable granular materials increases with the moisture content,due to the decrease of particle strength in a humid environment.An existing approach to take into account the effect of grain breakage in constitutive modeling consists in linking the evolution of the grain size distribution to the plastic work.But how the material humidity can affect this relationship is not clear,and experimental evidence is quite scarce.Based on compression tests on dry and saturated crushable sand recently reported by the present authors,a new non-linear relationship is proposed between the amount of particle breakage and the plastic work.The expression contains two parameters:(1)a material constant dependent on the grain characteristics and(2)a constant depending on the wetting condition(in this study,dry or saturated).A key finding is that the relationship does not depend on the stress path and,for a given wetting condition,only one set of parameters is necessary to reproduce the results of isotropic,oedometric,and triaxial compression tests.The relationship has been introduced into an elastoplastic constitutive model based on the critical state concept with a double yield surface for plastic sliding and compression.The breakage ratio is introduced into the expression of the elastic stiffness,the critical state line and the hardening compression pressure.Incremental stress-strain computations with the model allow the plastic work to be calculated and,therefore,the evolution of particle crushing can be predicted through the proposed non-linear relationship and reintroduced into the constitutive equations.Accurate predictions of the experimental results in terms of both stress-strain relationships and breakage ratio were obtained.

干湿循环作用下堆石料宏细观力学特性的离散元模拟研究

堆石料的物理力学特性在干湿循环作用下会发生明显劣化。基于堆石料颗粒三维扫描结果,建立了宽粒径范围的堆石料颗粒模板库。考虑干湿循环对颗粒强度、颗粒间接触模量和摩擦系数的影响,提出了一种考虑堆石颗粒干湿循环劣化的颗粒破碎模拟方案。在此基础上,采用FDM-DEM耦合方法对不同干湿循环作用下的堆石料试样进行一系列三轴压缩试验,讨论了在三轴压缩条件下干湿循环对堆石料宏细观力学特性的影响规律。结果表明:堆石料的初始模量和峰值强度随着干湿循环次数N的增加而呈非线性降低,干湿循环对体变曲线在初始阶段的剪缩和加载后期的剪胀有抑制作用,当N增大至某一值时,干湿循环对堆石料的宏观变形和强度的影响逐渐不明显。干湿循环次数越大,试样内部平均配位数越大,接触滑移比越大,试样内部的偏组构呈非线性减小,即各向异性程度在逐渐减小,这说明干湿循环对试样内部的各向异性发展有抑制作用。

大豆秸和稻草对甜玉米秸秆和湿啤酒糟混合青贮的影响

甜玉米(Zea mays var.rugosa)秸秆和湿啤酒糟含水量较高,青贮可有效解决其不易贮藏的问题。通过设置甜玉米秸秆单贮、湿啤酒糟单贮、两者不同比例(3∶1和4∶1)混合青贮以及分别添加大豆(Glycine max)秸和稻(Oryza sativa)草将混合青贮的含水量调节为60%和70%,共12个处理,探究混合比例及含水量对其混合青贮发酵品质及有氧稳定性的影响。结果表明:甜玉米秸秆单贮发酵品质良好,湿啤酒糟单贮发酵品质较差,二者按3∶1混贮后显著提高了乳酸及乙酸含量(P<0.05),4∶1混贮后显著提高了乳酸含量(P<0.05),但4∶1混贮后好氧细菌及酵母数量较3∶1高;与甜玉米秸秆单贮相比,添加大豆秸显著提高了混合青贮料的有氧稳定性(P<0.05),有氧暴露7 d后的pH值仍接近4.2,添加大豆秸将含水量调节为60%显著降低了NH3-N含量(P<0.05);添加稻草的所有处理均显著降低了NH3-N含量(P<0.05)。综上,甜玉米秸秆与湿啤酒糟按3︰1的比例混合,并添加大豆秸将含水量调节为60%,其发酵品质好,有氧暴露7 d有氧稳定性也较好。

不同灌溉模式对籼粳杂交稻甬优1540产量与水分利用效率的影响

旨在探讨不同灌溉模式对籼粳杂交稻甬优1540产量与水分利用效率的影响,并阐明其相关生理基础。本研究以甬优1540为材料,设置了3种灌溉模式,即长淹灌溉(continuous flooding,CF)、轻度干湿交替灌溉(alternate wetting and moderate drying, AWMD)以及重度干湿交替灌溉(alternate wetting and severe drying, AWSD)。研究结果表明,与CF相比, AWMD与AWSD均能显著提高水分利用效率,增幅分别为22.6%~25.6%与18.2%~23.1%;AWMD可以显著提高水稻产量,增幅为8.6%~10.0%,而AWSD则显著降低水稻产量,降幅为6.0%~7.5%。与CF相比, AWMD显著降低了拔节期水稻的茎蘖数、地上部干物质重、叶面积指数、移栽至齐穗期的光合势以及移栽至拔节期的作物生长速率,但显著提高了茎蘖成穗率、拔节至齐穗期的作物生长速率、主要生育期水稻根长密度、深根比、比根长、根系总吸收表面积与活跃吸收表面积,以及灌浆后2次土壤复水期的剑叶净光合速率、根系氧化力、根系与叶片中玉米素和玉米素核苷(Z+ZR)含量、籽粒中蔗糖-淀粉代谢途径关键酶活性等指标。以上结果表明, AWMD可以协同提高甬优1540产量与水分利用效率,优化根-冠生长发育特征,提高灌浆期植株生理活性,实现高产与水分高效利用,为本研究最佳水分管理模式。

酒糟蛋白替代豆粕对九斤黄鸡生长性能、血清生化和免疫指标的影响

[目的]研究不同比例的湿磨预处理去壳酱香型酒糟蛋白(wet milling pretreated and dehulled-moutai distiller's grains, WDMDG)替代豆粕对九斤黄鸡生长性能、血清生化和免疫指标的影响,为WDMDG替代豆粕提供科学依据。[方法]选取1日龄健康九斤黄公雏450只,随机分为3组,每组设3个重复,每个重复50只鸡,对照组饲喂基础日粮,试验Ⅰ和试验Ⅱ组分别在基础日粮中添加5%、8%WDMDG等营养替代豆粕,试验为期26 d,分别测定九斤黄鸡平均日增质量、平均日采食量、料重比和死淘率,并对九斤黄鸡血清中总蛋白、白蛋白、尿素氮含量、谷丙转氨酶和谷草转氨酶活力和IgG、IgA、lgM水平进行测定。[结果]与对照组相比,试验Ⅰ和试验Ⅱ组九斤黄鸡的各项生产性能均没有显著差异,试验Ⅰ和试验Ⅱ组鸡血清中尿素氮含量分别提高了4.88%(P>0.05)和19.51%(P<0.05),各组鸡血清中总蛋白、白蛋白含量、谷草转氨酶和谷丙转氨酶活力及IgG、IgA和IgM水平差异均不显著。[结论]在九斤黄鸡日粮中采用5%WDMDG等营养替代基础日粮中部分豆粕,对其日增质量、料重比、死淘率、血清生化指标和免疫指标均无显著负面影响。

机械润粮工艺对酱香型白酒生产的影响

该实验在保持与传统润粮工艺用水量及水温一致的情况下,建立了机械润粮法,以下沙、造沙和轮次生产为例,探究机械润粮对酱香型白酒生产的影响。结果表明,与传统润粮工艺相比,机械润粮工艺酒醅中的酸度、还原糖、淀粉、水分含量等指标均无显著性差异(P>0.05);两种不同润粮工艺生产1~7轮次基酒总酸、总酯含量和变化趋势较为一致,二等酒比例均在90%左右,机械润粮工艺生产基酒产能及大回酒比例略优于传统润粮工艺。机械润粮可控性高、节约劳动力,安全系数高,可在酱香型白酒酿造润粮环节推广应用,同时也为酱香型白酒机械化、智能化酿造提供支撑。

干湿循环对不同粒径堆石颗粒破碎强度的影响研究

高心墙堆石坝在运行期库水位变化可达60 m以上,库水位变动范围内的堆石体受干湿循环作用易产生较大的后期变形,会导致坝顶出现纵向裂缝,影响高心墙堆石坝的安全稳定运行。干湿循环对堆石料长期劣化变形的影响已有大量的试验研究,然而干湿循环对不同粒径筑坝堆石颗粒破碎强度的影响研究相对较少。对不同粒径的板岩堆石颗粒进行了干湿循环作用后的单颗粒破碎试验,结果表明,板岩颗粒的荷载-位移曲线及其对应破碎模式可以分为4类,颗粒破碎时对应的峰值荷载和破碎强度均值随循环次数的增加而逐渐减小。不同粒径和循环次数下板岩颗粒的破碎强度均服从Weibull分布,特征破碎强度与循环次数间呈幂指数关系,表明板岩颗粒力学性质的劣化速度逐渐减慢。不同循环次数下板岩颗粒的特征破碎强度均有较为明显的尺寸效应,尺寸效应与循环次数呈负相关关系。

冻融干湿循环条件下粒径及盐分对土壤粗颗粒风化速率的影响

【目的】探究冻融干湿循环条件下,土壤粒径及盐分对土壤粗颗粒风化速率的影响。【方法】以土壤粗颗粒(灰绿板岩)为研究对象,设置粒径(10、20、30mm)、盐分浓度(3、6、10g/L及蒸馏水作对照)两因素,开展冻融干湿循环随机试验,分析不同循环次数下土壤粗颗粒风化速率的变化规律。【结果】(1)在水盐溶液处理下土壤粗颗粒风化速率均比单纯水处理大,10g/L盐分处理下的土壤粗颗粒风化速率大于其他处理。在20~60次冻融干湿循环之间,10 mm土壤粗颗粒的风化速率随盐分浓度的增加而增大。(2)土壤粗颗粒风化速率随粒径的增大呈减小趋势,且10 mm的土壤粗颗粒风化速率大约是30 mm的2倍。(3)土壤粗颗粒风化速率随冻融干湿循环次数的增大而增大,A1B4(10 mm 10 g/L)组合下的土壤粗颗粒风化速率最大。【结论】在冻融干湿循环影响下,小粒径的土壤粗颗粒风化速率大于大粒径,且水盐作用对土壤粗颗粒风化速率的影响大于单纯水作用。

潮湿细粒煤炭筛分抗堵机理及参数优化研究

深部筛分是实现潮湿细粒煤高效分级的重要途径,但会出现筛面堵塞的问题,刚柔耦合弹性筛分方法被用于克服堵塞。探究了进料速率和物料含水率对筛分性能的影响及相关机理,对3 mm湿细粒煤进行刚柔耦合弹性筛分与刚性筛分对比实验,进一步明确了筛分过程中颗粒的空间分布规律。当外部含水率为11.31%时,筛分效率达到83.15%,总错配物率为6.40%,有效提高了潮湿细粒煤的筛分性能。

基于仿生蛾眼结构制备减反射微晶玻璃

目的采用湿法刻蚀制备减反射微晶玻璃,分析晶化时间对透过率、反射率和形貌的影响。方法通过熔融法制备得到基础玻璃,调整晶化时间制备得到一系列不同晶粒尺寸(12.2~27.4nm)的微晶玻璃,将制备得到的基础玻璃及不同晶粒尺寸的微晶玻璃放置在配制好的5%(质量分数)HF、2%(质量分数)SiO_(2)、1.5%(质量分数)BaSO_(4)、2%(质量分数)羧甲基纤维素钠、89.5%(质量分数)H_(2)O的刻蚀液中,在25℃条件下,以40 kHz的超声频率双面蚀刻60 min,通过分光光度计测试刻蚀前后样品的透过率和反射率,利用扫描电子显微镜对刻蚀前后样品的表面和断面形貌进行表征。结果基础玻璃在500℃核化230 min,665℃晶化135 min后,制备得到微晶玻璃的晶粒尺寸约为25.1 nm,进一步经过湿法刻蚀后,刻蚀深度约为150 nm,蛾眼玻璃透过率最高为98.02%。结论微晶玻璃经过湿法刻蚀后增透效果明显,对X射线衍射(XRD)、掠入射X射线衍射(GIXRD)、扫描电子显微镜(SEM)的测试结果进行分析可知,微晶玻璃中存在晶体相和残余玻璃相,经过酸蚀处理后,表面能形成以透锂长石晶体和二硅酸锂晶体均匀分布的蛾眼结构,晶体尺寸为12.2~27.4 nm的微晶玻璃进行湿法刻蚀后透过率分布在95.99%~98.02%。

高填方粗粒土干湿循环及蠕变特性三轴试验研究

白鹤滩水电站库区蓄水后,其高填方场地将长期经历水位升降,对于场地的变形和稳定来说十分不利。依托于白鹤滩水电站库区移民安置区消落带高填方场地稳定性研究项目,通过大型常规三轴剪切试验和蠕变试验分析了粗粒土在干湿循环作用和饱水条件下的应力应变关系、剪切形态特征、长期强度、变形规律等,得到主要结论如下:①粗粒土的强度随着干湿循环次数的增加逐渐降低;②干湿循环次数n≤3时,粗粒土试样先剪缩后剪胀,n>3时,粗粒土只有剪缩变形;③粗粒土的峰值偏应力随着干湿循环次数的增加逐渐降低,围压越高干湿循环作用对粗粒土抗剪强度损伤劣化的影响越大;④粗粒土的长期强度较剪切破坏强度有所降低,在低围压下降幅较小,一般情况下可达到剪切破坏强度的80%甚至更高,在高围压下由于颗粒破碎严重粗粒土的长期强度损伤较大。

密相栓流湿颗粒气力输送数值模拟

鉴于目前对于湿颗粒密相气力输送的研究缺乏成熟的体系与结论,本文探究了湿颗粒密相气力输送的流动机理与流动形态,为气力输送的优化设计提供理论支持。研究采用计算流体力学(computational fluid dynamics,CFD)和离散元法(discrete element method,DEM)双向耦合的数值模拟方法,对水平管道中干湿颗粒料栓的运动形式和颗粒运动轨迹进行了分析,深入研究了颗粒含水率对输送流型、输送效率以及输送压降的影响。结果表明,同等气速下,湿颗粒可以形成段塞流,而干颗粒先是段塞流,随后料栓被气体击穿演变为沙丘流,最后成为管底流;随着气体速度的增大,单位长度的水平管道压降数值呈现先降低后增长的趋势,在质量流率0.5 kg/s、含水率5%的工况下,输送速度为9 m/s时管道压降数值最低,为最佳经济速度值;湿颗粒的压力曲线一直处于波动较大的不稳定状态,当两个监测点位于段塞外部时,轴向压差几乎为零,而当两个监测点位于段塞内部时,轴向压差可以达到-600 Pa。通过对湿颗粒输送时的压降变化进行分析和监测,可及时发现设备故障的迹象,预警可能的问题并采取预防措施,避免设备损坏和生产中断。

木纹纸原纸的生产技术

木纹纸是一种低定量的装饰纸,原纸的质量对后续的加工起到至关重要的作用。通过调节合适的pH值以及纸张最佳的吸收性提高了客户的上机性能,低打浆度打浆、低紧度的生产工艺更能有效地抑制纸张的收缩性,从而使得套印更加准确。

干湿谷物混合干燥工艺与干燥参数的研究

研究了干湿谷物混合干燥工艺与传统干燥工艺的性能差异;研究了缓苏过程中干湿谷物的水分传递规律及各干燥参数对干湿谷物混合干燥的影响,建立了干燥参数与干燥性能的数学模型。用非线性约束优化方法找出最佳干燥工艺与干燥参数。

结实期干湿交替灌溉对稻米品质及籽粒中一些酶活性的影响

在土培池和大田试验条件下,观察了结实期干湿交替灌溉对武育粳3号(粳稻)和扬稻6号(籼稻)米质和籽粒中淀粉合成关键酶活性的影响以及它们之间的关系。与对照(保持水层)相比,轻干-湿交替灌溉(土壤干至土壤水势为-25kPa时复水)增加了结实率和粒重,降低了垩白粒率和垩白度,提高了淀粉的最高黏度和崩解值,减小了热浆黏度、最终黏度和消减值。重干-湿交替灌溉(土壤干至土壤水势为-50kPa时复水)的结果则相反,两品种结果趋势一致。轻干-湿交替灌溉增加了籽粒中蔗糖合成酶(SuS)、腺苷二磷酸葡萄糖焦磷酸化酶(AGP)、淀粉合成酶(StS)和淀粉分支酶(SBE)活性,重干-湿交替灌溉则降低了上述各酶的活性。不同灌溉方式对籽粒中酸性转化酶(AIV)活性影响较小。SuS、AGP、StS和SBE活性与粒重、最高黏度、崩解值呈显著正相关,与垩白度和消减值呈显著负相关。上述结果说明结实期轻干-湿交替灌溉可以改善稻米品质,SuS、AGP、StS和SBE在籽粒形成中起重要作用。

粗粒料三轴湿化颗粒破碎试验研究

颗粒破碎是引起粗粒料湿化变形的重要因素,有必要对其进行深入研究。利用改进的应力控制三轴仪,对坝的粗粒料进行不同围压和湿化应力水平下保持应力水平不变的三轴湿化变形试验,同时对湿化前后的试样进行颗粒分析试验。依据试验结果,分析湿化颗粒破碎的原因,得到湿化变形量及Hardin的颗粒破碎指标表示的颗粒破碎量。对粗粒料湿化变形和湿化颗粒破碎试验结果的分析表明:湿化变形与围压及湿化应力水平有关;湿化引起颗粒破碎,对颗粒级配曲线有较大的影响,湿化前后级配曲线的颗粒累积百分比的差值随粒径呈驼峰状分布,驼峰位于25%含量粒径左右;湿化引起的颗粒破碎使得级配曲线的曲率系数、不均匀系数和60%含量粒径减小;湿化颗粒破碎随着围压和湿化应力水平的增加而增加;湿化变形与湿化颗粒破碎之间有很好的相关性,湿化轴变与湿化颗粒破碎近似成线性关系;湿化变形的基本规律可以根据湿化颗粒破碎规律加以解释。