Characteristics and Growing Stocks Volume of Forest Stand in Dry Temperate Forest of Chilas Gilgit-Baltistan

Chilas forest sub division in Diamer district, of Gilgit-Baltistan is located at northern regions of Pakistan. We estimated tree density, diameter, height and volume of the dominant tree species in four blocks (Thore, Chilas, Thak Niat and Gunar) of Chilas forest sub division. The tree density of deodar was maximum with average 26 tree·ha-1 and minimum was of Chalgoza 4 trees·ha-1. The maximum average height showed by the dominant species (Fir, Kail, Deodar, and Chilgoza) of the study area to be 20.40, 16.06, 12.24 and 12.12 m respectively. Moreover the average maximum volume attained by the Kail, Fir, Deodar and Chalgoza trees was 1.92, 1.57, 0.46 and 0.291 m3·tree-1 respectively. Regression analysis was carried out to determine the relationship between diameter (cm), height (m), tree density (trees·ha-1) and volume (m3·ha-1). The findings of the study will help the future scientific management of the forest for sustained yield. The study also provides information about the unexplored growing stock and structure of the forests. Additionally, this study will help to understand the patterns of tree species composition and diversity in the northern part of Pakistan with dry temperate climate.

Temporal Stability of Sward Dry Matter and Nitrogen Yield Patterns in a Temperate Grassland

The objectives of the present study were to examine the spatial patterns of sward dry matter (DM) and nitrogen (N) yields in a grass silage field at first, second, and third cuts over a 3-year period; quantify their temporal stabilities with temporal stability maps; and assess the potential for site-specific management in each pasture-growing period using classified management maps. At cut 1, the spatial patterns of DM and N yields proved to be well defined and temporally stable and were likely to be due to differences in the net N mineralization rates across the field during spring. In contrast, at cut 2, the patterns of DM production were patchy and temporally unstable. It was concluded that, in principle, a simple site-specific approach to N fertilization would be possible in this field during spring at cut 1. At later harvests, the rationale for a site-specific approach to fertilizer management was less clear with logistics appearing to be more complex and less feasible.

A Comparative Study of Different Drying Processes for a Deformable Saturated Porous Medium

Drying of a deformable saturated porous medium based on convective tempering is a novel method that can enhance energy efficiency and the quality of the dried product itself.In this experimental investigation,the performances of this specific technique are compared with those of a standard stationary drying process in terms of deformation,drying kinetics,moisture redistribution,and energy consumption.In particular,the response of a deformable saturated porous medium(Kaolin)is considered.The results are critically discussed pointing out advantages and drawbacks.

籼粳杂交稻变温-缓苏干燥工艺优化及蛋白结构研究

为提升稻谷干燥品质,本实验以籼粳杂交稻为对象,通过爆腰率、整精米率、能耗、干燥时间进行评价,结合单因素、响应面分析优化干燥工艺;同时采用差示扫描量热仪、傅里叶红外光谱、荧光光谱等技术手段,探究了变温-缓苏干燥对籼粳杂交稻蛋白结构及热特性的影响。结果显示:变温-缓苏干燥(变温区间30~60℃)在升温温度5℃、风速1 m/s、缓苏比0.6条件下可使稻谷始终保持在玻璃态,干燥后的爆腰率和整精米率比恒温组(60℃)分别降低79.89%和提高39.54%。在此条件下稻谷蛋白质发生极性减弱、分子间聚集现象,提高了蛋白质热稳定性,α-螺旋含量由16.21%提升至17.64%;扫描电镜结果表明,变温-缓苏干燥未对蛋白质表面结构造成明显影响。实验探究并验证了杂交稻谷变温-缓苏干燥机制,为杂交稻谷高品质干燥研究提供了理论和实践参考。

Influence of Material Condition on the Dry Sliding Wear Behavior of Spring Steels

During the past two decades, considerable efforts have been made in the development of high performance spring steels to meet the needs for weight and savings in the automotive industry. During the service the suspension system will be subjected to different environmental conditions, at the same time it has to sustain a variety of loads acting on it. Among all the wear of spring steel plays a vital role. In this experimental analysis an attempt has been made to investigate the performance of spring steel (EN-47 / SUP 10) under the dry sliding condition. The specimen preparation and the experimentations have been carried out according to the ASTM G99 standards. The effects of tempering and cryogenic treatments on the performance of the spring steel have also been determined. The results have revealed that the material condition has got a significant influence on the performance of the spring steel. In order to analyze the percentage contribution of different wear parameter and the material condition, the DOE and ANOVA have been made. The results have shown that the load (49.205%) has shown the highest influence and the material condition has shown 22.56% of contribution on wear behavior.

Responses in gross primary production of Stipa krylovii and Allium polyrhizum to a temporal rainfall in a temperate grassland of Inner Mongolia, China

In the arid and semi-arid areas of China, rainfall and drought affect the growth and photosynthetic activities of plants.Gross primary productivity(GPP) is one of the most important indices that measure the photosynthetic ability of plants.This paper focused on the GPP of two representative grassland species(Stipa krylovii Roshev.and Allium polyrhizum Turcz.ex Regel) to demonstrate the effect of a temporal rainfall on the two species.Our research was conducted in a temperate grassland in New Barag Right Banner, Hulun Buir City, Inner Mongolia Autonomous Region of China, in a dry year 2015.We measured net ecosystem productivity(NEP) and ecosystem respiration flux(ER) using a transparent chamber system and monitored the photosynthetically active radiation(PAR), air and soil temperature and humidity simultaneously.Based on the measured values of NEP and ER, we calculated the GPP of the two species before and after the rainfall.The saturated GPP per aboveground biomass(GPPAGB) of A.polyrhizum remarkably increased from 0.033(±0.018) to 0.185(±0.055) μmol CO2/(gdw·s) by 5.6-fold and that of S.krylovii decreased from 0.068(±0.021) to 0.034(±0.011) μmol CO2/(gdw·s) by 0.5-fold on the 1st and 2nd d after a 9.1 mm rainfall event compared to the values before the rainfall at low temperatures below 35℃.However, on the 1st and 2nd d after the rainfall, both of the saturated GPPAGB values of S.krylovii and A.polyrhizum were significantly lower at high temperatures above 35℃(0.018(±0.007) and 0.110(±0.061) μmol CO2/(gdw·s), respectively) than at low temperatures below 35℃(0.034(±0.011) and 0.185(±0.055) μmol CO2/(gdw·s), respectively).The results showed that the GPP responses to the temporal rainfall differed between S.krylovii and A.polyrhizum and strongly negative influenced by temperature.The temporal rainfall seems to be more effective on the GPP of A.polyrhizum than S.krylovii.These differences might be related to the different physiological and structural features, the coexistence of the species and their species-specific survival strategies.

新型40.5kV/2500A干燥空气绝缘充气柜温升控制研究

采用干燥空气取代SF_(6)绝缘的中压充气柜,符合绿色环保发展方向,但空气的对流散热能力弱于SF_(6),这对充气柜的散热结构提出了更高要求。文中提出了一种采用纵向直线布置主回路的40.5 k V 2 500 A干燥空气绝缘充气柜总体结构,其具有主导电回路短、发热功率较低的特点。对该充气柜进行发热与散热分析、仿真和试验研究,发现采用常规结构气箱时,其内部空气温升达60 K左右,气箱内热量无法散到气箱外部是整体温升超标的主要因素。从增强对流散热和辐射散热方面对散热结构进行优化,重点设计了柜体侧板外表面的散热通道,优化后的方案通过了1.1×2 500 A温升试验,验证了设计和优化思路的可行性。

非调质钢加热过程的硫化物转变和形貌控制

非调质钢的要求高,除硫化物含量外,还需要控制其形貌、分布。对非调质钢硫化物高温形变机理进行了研究。结果表明,当钢加热时,钢中的硫化物随着温度的提高和保温时间的延长,开始发生形变,小的硫化物逐渐溶解到基体中,较大的硫化物发生延伸、溶解、断裂、球化等一系列的形貌转变,且钢奥氏体化后,硫化物变化更加明显。当加热温度达到1200℃时,形变更加活跃,随着保温时间延长,钢中长条形的硫化物断裂碎化加快,数量增多。

间歇干燥及缓苏对高水分稻谷干燥品质的影响

对高水分稻谷进行了间歇干燥,研究干燥段数和缓苏温度对稻谷干燥品质的影响,并应用隶属度分析法对干燥品质进行综合评价。结果表明,间歇干燥可缩短干燥时间,与连续干燥40℃缓苏组相比,4段60℃缓苏组的干燥时间缩短了26.36%。间歇干燥可显著地降低干燥后稻谷的爆腰率,提高整精米率。高温缓苏(50、60℃)时,缓苏温度对整精米率影响优于干燥段数。热风干燥后稻谷的脂肪酸值增加,发芽率降低。隶属度分析法得出优化后的干燥条件为:干燥段数为2段,缓苏温度为60℃,综合分为最大值0.80。

稻谷等温干燥-缓苏过程数值模拟及优化

利用稻谷干燥热湿传递数学模型,对稻谷等温干燥-缓苏过程进行数值模拟,对比分析了缓苏条件下干燥稻谷籽粒内部水分分布变化规律。结果表明:与热风温度60℃下单纯干燥过程相比,缓苏降低了稻谷内部的水分梯度峰值,缩短了干燥时间,同时将籽粒干燥终了水分梯度降低接近50%。通过参数研究,发现缓苏温度、缓苏比和缓苏时间是缓苏过程的重要参数,并提出干燥-缓苏过程的优化机制,即在稻谷籽粒干燥缓苏过程初期设置短时缓苏、中期单纯干燥、后期长时缓苏,可有效地降低水分梯度过程最大值和终了值,缩短缓苏时间和减少次数。本研究为稻谷干燥缓苏提供了理论和技术支持。

干平整中工作辊与带钢表面粗糙度对摩擦系数影响的研究

针对干平整轧制过程中工作辊与带钢表面粗糙度对摩擦系数的影响仅能定性分析、不能满足生产需要的问题,经过大量的现场试验与理论研究,充分结合平整机组的设备与工艺特点,基于粗糙度的基本理论,根据干平整轧制过程中摩擦特点构造了反映工作辊及带钢表面粗糙度与摩擦系数之间一一对应关系的数学模型,提出了相应的模型计算策略,并将其应用到宝钢冷轧薄板厂1 220平整机组的生产实践,定量分析了工作辊及带钢表面粗糙度对摩擦系数的影响,有效地提高了轧制压力的预报精度与产品质量,取得了良好的使用效果,具有进一步推广应用价值。

稻谷干燥缓苏特性与裂纹产生规律研究

利用声发射系统监测稻谷籽粒热风干燥过程中微裂纹的形成和发展;对稻谷进行了不同条件的热风干燥-缓苏实验,分析了不同缓苏工艺对干燥特性及裂纹率的影响,并探究了现象产生的原因。结果表明:稻谷在干燥过程中一直有微裂纹产生或发展,缓苏工艺可有效抑制干燥后的稻谷籽粒产生宏观裂纹,降低净干燥时间;恒温干燥温度以40、45℃为宜;等温度干燥-缓苏条件下,干燥温度可提高到50℃,裂纹率增值合格;在低温干燥-高温缓苏工艺中,当缓苏温度比干燥温度高15℃时,干燥时间最短,产品裂纹率增值不超过3%,随缓苏温度提高,所需的缓苏时间越短。研究结果可为节能高效的稻谷干燥工艺研究提供借鉴。

胶体多孔介质的缓苏-间断干燥工艺研究

以胶体多孔介质胡萝卜切片为物料,以干燥后产品的含水量和β-胡萝卜素保留率为质量指标,研究了物料在静态干燥、动态干燥以及缓苏-间断工艺干燥处理时的产品质量变化规律.结果表明:动态干燥过程中,物料与加热介质的接触面积大,干燥速率较高;缓苏-间断工艺使物料中的剩余水分得以重新分布,消除了物料的表面硬化,可以更快地去除物料中的水分,且β-胡萝卜素的保留率最高.此研究结果可以有效地指导工业生产.

玉米籽粒缓苏干燥过程动力学分析

对玉米籽粒的缓苏干燥过程进行了理论分析,并假设玉米籽粒为轴对称结构、各向同性的均匀物质,建立了玉米籽粒的缓苏干燥数学模型,利用COMSOL Multiphysics模块进行了热质传递过程的模拟研究。结果表明,该模型可较好地模拟玉米籽粒的干燥过程。利用该模型模拟研究了不同干燥条件下玉米籽粒温度、干燥时间、缓苏时间、缓苏度的变化及其对干燥速度的影响。结果表明,玉米籽粒内外温度在3~5 min内即可达到热风温度,玉米籽粒内部最大水分梯度出现在热风干燥5~10 min后,不同干燥阶段不同初始含水率对缓苏度的影响很小,缓苏60 min水分梯度可以基本消除。利用该优化工艺参数对玉米籽粒交替进行热风干燥和缓苏干燥,可使总的热风干燥时间最少,实现节能目的。

干燥温度及缓苏操作对稻谷爆腰的影响

设置不同初始含水率、干燥温度、缓苏温度及缓苏时间,对稻谷进行薄层干燥;进而获取干燥操作参数对稻谷爆腰率的影响,为改善稻谷碾磨品质提供参考。试验结果表明:当初始含水率在24%左右时,缓苏技术对干燥后稻谷爆腰率影响显著;干燥温度应控制在50℃～60℃,缓苏温度应保持在60℃～70℃,缓苏时间制定在120 min～160 min,干燥后稻谷爆腰率增幅明显降低。

降温缓苏多级顺流粮食干燥工艺的模拟研究

针对现实多级顺流粮食干燥机在结构及使用上的缺陷,依据粮粒在降温过程中内部水分扩散方程的相关理论,提出一种降温缓苏与顺流加热干燥相结合的降温缓苏多级顺流干燥工艺,并进行了该干燥工艺与理想型多级顺流干燥工艺的模拟对比试验,证明这种新干燥工艺具有更容易保证粮食品质,节能高效的优越性。

缓苏在粮食干燥中的研究进展

干燥处理是保证粮食安全的重要手段,提高粮食干燥能力及干燥质量是我国粮食产后亟待解决的关键问题。缓苏作为粮食加工、储藏和流通过程中重要环节,兼有节约能耗和提高产品品质的双重特点。本文对缓苏操作进行了详细分类,系统阐述了在粮食干燥过程中缓苏操作参数的优化方法及对粮食品质和能耗的影响,提出目前国内外在粮食干燥研究领域所存在的问题,并对其应用前景作了客观分析。

玉米多段干燥出机粮含水率与干燥过程温度关系的试验研究

本文提出了粮食多段干燥过程排粮速度、各段温度的检测与统计计算方法。根据玉米四段干燥过程粮层通过干燥段2与缓苏段2及干燥段3与缓苏段3的温度差值,将玉米干燥温度变化特征分为:缓苏段温度平衡型,缓苏段温度上升型,缓苏段温度下降型以及6种复合型。利用谷物表面温度为空气温度、颗粒内温度由内向外逐渐升高、水分在颗粒内部解吸附并汽化沿毛细通道逸出颗粒表面的模型和多孔介质内在压力梯度作用下沿毛细通道流动的水分传输机理解释了产生这种温度变化差异的原因,即近表皮层水分逸出阻力主要取决于玉米颗粒表皮层的致密性,而远离表皮层水分选出取决于表皮层与毛细通道阻力的作用之和。通过比较℃以上与0℃以下入机粮温样本温度特征类型占总样本量百分比,提出冷冻后玉米颗粒干燥时,表皮层致密性受到破坏,易于干燥过程水分的选出。给出了利用玉米干燥过程温度和干燥时间预测各类型玉米样本出机含水率的方法。本文研究成果对于指导干燥过程操作和实现干燥过程出机含水率的智能控制具有重要意义。

不同缓苏条件对稻谷爆腰率影响的研究

研究了干燥时间、缓苏温度及缓苏时间对稻谷爆腰率的影响。结果表明,干燥时间越长,干燥后72h爆腰率越高。缓苏可有效地抑制稻谷爆腰率,干燥50 min后,40℃、60℃、80℃三种缓苏温度都可有效抑制爆腰率,使爆腰率降低88.6%。干燥90min后,稻谷水分含量为14.5%,40℃缓苏后爆腰率仍达到了76%,80℃缓苏后爆腰率仅为8%,可见高温缓苏抑制效果更佳。缓苏温度越高,缓苏效果越好,提高缓苏温度可缩短缓苏时间。稻谷干燥时间延长,应相应地提高缓苏温度,增加缓苏时间。

基于多品质指标的响应面试验优化稻谷流化床干燥工艺

为优化稻谷流化床干燥工艺,采用三因素三水平Box-Behnken响应面分析法,研究干燥温度、降水幅度、缓苏时间对稻谷流化床干燥降水速率和干燥稻谷爆腰增率、垩白粒率、脂肪酸值、硬度、黏着性等品质指标的影响。结果表明:随着干燥温度和降水幅度水平的增加,稻谷降水速率、爆腰增率、垩白粒率和米饭硬度增加,脂肪酸值和米饭黏着性降低;随着缓苏时间延长,稻谷降水速率、爆腰增率、脂肪酸值和米饭硬度降低,米饭黏着性增加。而在较低的干燥温度条件下,缓苏时间延长,稻谷的爆腰增率和垩白粒率降低并不明显。Box-Behnken响应面分析法优化的流化床最优干燥参数为降水幅度2.50%(干基)、干燥温度45℃、缓苏时间3 h,此时隶属度综合分达最大值0.75。验证实验结果与拟合值无显著性差异(P<0.05),优化结果可靠有效。