Optimization of processing variables during heat treatment of oak (Quercus mongolica) wood

The properties of oak heat treated at temperatures of 160–220 °C, oxygen concentrations of 2–10 %, steam pressures of 0.1–0.4 MPa and treatment time of 2–4 h were investigated. Although modulus of elasticity (MOE), modulus of rupture (MOR) and equilibrium moisture content (EMC) of the heat-treated wood (HTW) were reduced, the value of $ \Updelta E^{*} $ was increased, and the dimensional stability [anti-swelling efficiency in radial (ASE-R), anti-humidity efficiency (AHE)] was improved considerably. Six regression equations (temperature, oxygen concentration, steam pressure and time as functions of MOE, MOR, ASE-R, AHE, EMC and $ \Updelta E^{*} $ ) were developed for the estimation and a nonlinear programming model was derived with operation research theory to obtain the most desirable HTW properties under some production constraints.     

鲁北丹河下游洪水决口扇沉积岩芯粒度特征与沉积过程重建

洪水沉积物粒度是反演洪水特征及过程的关键参数,也是识别古洪水沉积层的重要前提和依据.通过对山东北部丹河2018年洪水淹没区考察,取得21cm长无扰动沉积物短钻DH2,室内进行粒度分析,并对实验结果进行组分拟合,获得如下主要结论:1)DH2钻孔粒度整体较细,以细粉砂为主;2)洪水决口扇沉积层与下伏土壤层相比,沉积物粒度整...     

中国农业绿色发展政策主题与发文机构网络演进研究——基于1982—2022年政策文本的实证分析

“绿色”是新时代农业发展的主方向,为厘清农业绿色发展政策演进的核心特征和逻辑,本研究运用政策文献计量方法对我国改革开放以来中央层面农业绿色发展政策的聚焦主题、发文机构网络及其阶段性变化进行分析。结果表明:1)从政策主题看,政策理念由“兼顾绿色”转向“绿色驱动”,政策内容由“问题导向”转向“战略布局”;2)从发文机构网络看,政策主体由“松散-低度合作”转向“集中-高度合作”。中国农业绿色发展政策目标和政策措施不断完善,但政策目标仍需进一步细化,政策措施效果有待提升。未来农业绿色发展政策应保持中长期稳定性,推进因区施策,强化对薄弱环节的政策支持和政策实施中的部门协调。     

番石榴叶挥发油的抗菌性及优化提取研究

分别由酸疮痂链霉菌（Streptomyces acidiscabies, SA）、茄科雷尔氏菌（Ralstonia solanacearum, RS）和胡萝卜软腐欧文氏菌（Erwinia carotovora subsp. carotovora Borgey, ECCB）引起的植物疮痂病、青枯病、软腐病是农作物生产中常见多发的细菌病害。番石榴叶挥发油由多种活性物质组成,具有广谱抗微生物活性。本研究旨在提取并配置番石榴叶挥发油抗菌液,针对酸疮痂链霉菌、茄科雷尔氏菌、胡萝卜软腐欧文氏菌等3种病原菌进行挥发油的抗性研究,为农作物病害生物防治储备资源。采用添加锂盐结合微波辅助水蒸馏法提取番石榴叶挥发油,通过滤纸片扩散法和最小抑制浓度（MIC）评价了番石榴叶挥发油对3种供试菌株的抗菌效果,单因素结合响应面试验优化提取工艺,采用气相色谱-质谱联用技术（GC-MS）测定番石榴叶挥发油的化学成分。结果表明：番石榴叶挥发油对酸疮痂链霉菌、茄科雷尔氏菌、胡萝卜软腐欧文氏菌均表现出良好的抑制效果,抑菌圈直径范围为20.57～23.24 mm,抑菌率均达到60%以上,MIC值分别为3.13、1.56、3.13...     

浅谈吹填砂处理技术的优势及发展

吹填砂作为一种特殊的路基处理理论与处理技术,经过几十年的工程实践及理论研究,早已进入大面积应用、实施的阶段,成为目前加固软土地基的一个行之有效的、常规使用方法。该文结合工程实例,论述了应用吹填砂处理技术加固软土地基达到的良好实际效果。     

Dietary myo‐inositol requirements of juvenile hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂)

This study was conducted to determine the optimal dietary myo‐inositol (MI) requirement of juvenile hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂). Fish with an initial average body weight of 28.28 ± 0.41 g were randomly divided into six groups with three repetitions in each group and fed the experimental diets with different graded MI concentrations (70.2, 130.0, 270.2, 443.0, 1,096.6 and 1997.3 mg/kg) three times per day for 12 weeks. The results showed that with the increase in dietary MI level from 70.2 mg/kg to 443.0 mg/kg, weight gain (WG) was increased significantly (p < .05); however, when the MI level was further increased, there was no significant difference in weight gain rate (WG) over time (p > .05). Specific growth rate (SGR) showed a similar trend. The feed conversion ratio (FCR), survival rate (SR), hepatosomatic index (HSI), viscerasomatic index (VSI) and condition factor (CF) were not affected by dietary MI supplementation (p > .05). Dietary MI did not affect whole‐body and muscle crude protein and ash content (p > .05), while dietary MI significantly affected the muscle and whole‐body crude lipid and moisture content (p < .05). Moreover, serum triglyceride (TG), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were decreased by increasing dietary MI levels. Total antioxidant capacity (T‐AOC), malonic dialdehyde (MDA) and superoxide dismutase (SOD) activities in the liver were also affected by the dietary MI (p < .05). In summary, this study indicated that the optimal dietary MI requirement for juvenile hybrid sturgeon (Acipenser baerii ♀ × A. schrenckii ♂) was 335.84 mg/kg and 590.65 mg/kg based on the maximum WG and liver MI accumulation indices respectively.     

油菜秸秆和鸡粪比例及含固率对其发酵产甲烷特性的影响

基于低含固率粪秸厌氧发酵工艺存在的缺点和多原料共发酵的优势,以碳素和氮素含量互补的油菜秸秆和鸡粪为原料,采用批次中温((37±1)℃)发酵工艺,研究了不同含固率和挥发性物质质量混合比对2种原料产甲烷效率的影响,并分析了产甲烷过程稳定性及动力学特性,以期为粪秸高效产甲烷提供优化工艺参数。结果表明,当油菜秸秆和鸡粪的混合比为90∶10、85∶15和80∶20时,物料产甲烷效率均具有显著的协同效应,其中混合比为90∶10的物料产甲烷效率最高(288.7 mL/g),分别比纯鸡粪和纯油菜秸秆高16.1%和30.4%;当TS≥15%时,不同混合比粪秸的物料甲烷产率和容积甲烷产率较TS≤10%时均显著降低;在TS=10%条件下,二者混合比例为90∶10的物料甲烷产率和容积甲烷产率均较高,分别为224.4 mL/g和0.50 mL/(mL·d);挥发性脂肪酸的大量积累和高浓度铵态氮分别是破坏高C/N和低C/N物料产甲烷稳定性的原因,VFA/TA和氨氮浓度是评价不同C/N物料产甲烷过程稳定性的重要指标。根据动力学特性结果,建议在粪秸高含固率连续产甲烷启动阶段,适宜的固体滞留时间设为14 d。上述结果为油菜秸秆和鸡粪混合发酵高效产甲烷及其发酵过程稳定性的控制具有指导意义。     

不同马铃薯品种干旱适应性与其钾素营养特性的关系

采用盆栽试验,通过对5个马铃薯品种(‘V7’、‘大西洋’、‘实验二号’、‘大丰八号’和‘京张三号’)、2个水分条件(保持80%~85%土壤最大田间持水量,3轮干旱-复水)和2个钾肥水平(0 kg·hm^-2和180 kg·hm^-2)的三因素裂区试验,研究不同马铃薯品种的干旱适应性与其钾素营养特性之间的关系。结果表明：各品种马铃薯的干旱适应能力表现为‘实验二号’>‘V7’>‘大丰八号’>‘大西洋’>‘京张三号’,且干旱适应性与钾素营养特性呈显著正相关关系。钾素利用效率、植株钾素吸收量、块茎钾素吸收量和钾素吸收效率对马铃薯干旱适应性的贡献度分别为28.44%、15.08%、14.01%和8.55%。正常水分条件和干旱处理下的马铃薯水分利用效率与钾素利用效率、植株钾素吸收量和块茎钾素吸收量均呈显著正相关关系(P＜0.05),且与钾素利用效率的相关性最强,在正常水分条件和干旱处理下相关系数分别为0.97和0.96,推测钾素利用能力强的马铃薯品种可通过提高水分利用效率增强其对干旱的适应能力。研究结果表明,‘实验二号’更适合在北方旱区推广种植。     

冬小麦推迟春季首次灌水后不同品种的产量及水分利用效率

１９９１～１９９３年研究表明，即使两年度均为小麦生育期降水较少年份，且冬、春降水很少，在相同灌水量条件下，首次灌水推迟至拔节期或稍后１０日左右，小麦仍可获得高产，并提高了水分利用效率；在减少供水７５ｍｍ情况下，仍可维持高产而水分利用效率进一步提高。总的来看，随着首次灌水推迟，水分利用总量降低，而水分利用效率却因产量和水分利用而协调变化。品种对首次灌水推迟的反应不同：高产中早熟和前期对水分胁迫适应性强的品种更适于高产节水栽培，可将春季首次灌水推迟至拔节后挑旗前；晚熟大穗大粒型品种不宜推迟春季首次灌水，以免减产。