Effect of hot-air drying on flavour compounds of bell peppers (Capsicum annuum)

The influence of hot-air drying on the composition of both volatile and non-volatile flavour compounds of different Dutch bell pepper cultivars was investigated. Contents of glucose, fructose, ascorbic, citric, and oxalic acid decreased significantly after drying, while the levels of sucrose, malic, fumaric, and cis-aconitic acid increased. Glucose, fructose and ascorbic acid probably participate in Maillard reactions during heating. Different effects of drying could be distinguished on the composition of volatile compounds. The majority of these compounds evaporated during drying. Some compounds were partly retained in the dried bell peppers, whereas others disappeared completely. Gas chromatography-sniffing port analysis revealed that compounds with mainly “fresh” odour notes like lettuce/grassy/green bell pepper ((Z-2-3-hexenal), fruity/almond ((E)-2-hexenal), fruity (octanal), lettuce/green bell pepper ((Z)-3-hexenol), and grassy/green bell pepper ((Z)-2-hexenal) decreased or disappeared after drying. Another group of compounds increased or were formed during drying, like 4-octen-3-one, (E)-2-heptenal, (E)-2-octenal, (E,Z)- and (E,E)-2,4-heptadienal, decanal, and (E)-2-nonenal; most are known as autoxidation products of unsatu-rated fatty acids. The increased levels of 2-methylpropionic and 2- and 3-methylbutyric acid, 2-metlhylpropanal, and 2- and 3-methylbutanal seemed to be due to Strecker degradation. Gas chromatography-sniffing port analysis showed that the latter three compounds had distinct cacao, sweaty, and spicy odour characteristics.     

绵核桃剥壳机的研究设计

本文首先根据有关资料对核桃品种进行了分类，提纲 棉桃机械剥壳取仁和重要性。提出 齿盘－－齿板式主最优设计参数，并研制了绵核桃剥壳机对性能的初步考核表明，剥壳率９０５以上，高路仁率７０％－９０％，其中一路仁率３０－４０％。     

基于改进K-means聚类的变压器异常状态识别模型

针对投运时间不长的变压器数据中有极大部分是正常数据的情况,为了有效利用变压器历史正常数据识别变压器是否异常,本文提出了基于改进K-means聚类的变压器异常状态识别模型。针对变压器绝大部分运行数据为正常数据、正常数据逐渐按一定的趋势变化以及异常状态数据变化急剧等特点,基于历史正常数据与K-means算法建立变压器异常状态识别模型;根据对正常数据聚类的结果确定用于识别新数据的各个阈值;通过计算新数据到各聚类中心的距离并与各阈值对比确认变压器是否异常。针对传统K-means算法的缺点,对K-means算法进行基于密度与距离选择K值与初始聚类中心的改进,使K-means算法有稳定的K值与聚类中心,聚类过程更加快速、稳定、有效,从而使识别模型计算得到的阈值更可靠。实例分析表明,模型能有效对变压器的异常状态进行快速、准确的识别,为变压器状态评估提供一种新思路。     

超临界CO2萃取澳洲坚果花挥发油的化学组成分析

为了分析澳洲坚果花挥发油的化学组成和进一步开发利用澳洲坚果花提供科学依据,本文采用超临界CO2萃取技术提取澳洲坚果花中的挥发油,运用气相色谱-质谱（GC-MS）联用技术对其化学成分进行分离和鉴定,并用峰面积归一化法确定各组分的相对含量。结果表明：从澳洲坚果花挥发油中分离出50个色谱峰,鉴定了43个化合物,占总离子峰相对含量的87.09%。其主要由烯烃类（2.66%）、醇类（18.44%）、酚类（0.78%）、醛类（13.91%）、酮类（3.60%）、酯类（7.20%）、酸类（21.74%）及氧化物类（9.54%）等化合物组成。其化学成分主要有苯乙醇（8.75%）、4-羟基苯甲醛（6.88%）、反-吡喃型芳樟醇氧化物（6.25%）、苯乙酸（5.94%）、α-苄基苯乙醇（4.22%）、苯甲醇（3.75%）、桂酸（2.19%）、苯乙酸乙酯（1.72%）、芳樟醇（1.25%）等。     

保护层开采上覆煤层变形特性数值模拟

基于岩石破裂损伤理论和有限元计算方法,利用RFPA应用系统模拟分析了保护层开采过程中,被保护层层厚变形规律、煤层水平变形特征和保护层与被保护层之间的相对层间距对被保护层保护效果的影响,认为随着保护层采煤工作面向前推进,被保护层垂直变形呈现 “M”型分布;卸压区煤层水平变形呈现拉抻和挤压状态,增加该区域煤体机械破坏,有利于被保护层次生裂隙的发育;相对层间距对被保护层卸压变形产生较大影响,相对层间距愈大,其变形量减小,不利于煤层离层裂隙和破断裂隙的产生.对数值模拟结果与现场实际测定结果进行对比分析,两者基本吻合.     

微波萃取-衍生化-气相色谱质谱联用法测定土壤中酚类化合物

土壤样品基质复杂且酚类化合物含量很低,未经衍生的酚在气相色谱中峰型和稳定性较差,灵敏度较低,应用衍生化的方法时流程复杂,耗时长。用二氯甲烷和正己烷混合溶剂(2∶1,V/V)作为溶剂,75 ℃微波20 min提取土壤中的酚类化合物,在提取液中加入pH>12的强碱性水,使得酚类化合物生成对应的盐溶于水,弃去有机相后,将得到的水相调节至pH<12,用二氯甲烷和乙酸乙酯混合溶剂(4∶1,V/V)萃取酚类化合物。提取液经五氟苄基溴衍生后采用气相色谱质谱联用法检测,内标法定量,建立了微波萃取-衍生化-气相色谱质谱联用法测定土壤中14种酚类化合物的方法。在最佳的衍生条件下,以10 g土壤样品计,方法中酚类化合物的检出限为0.002~0.006 mg/kg。按照实验方法测定土壤样品,加标回收率为73.2%～119%,结果的相对标准偏差(RSD,n=6)为3.0%～9.5%。方法简化了衍生化步骤,有效改善了各酚类化合物峰形,增强了检测的灵敏度和稳定性,可用于土壤中酚类化合物的测定。     

The Influence of Electrode Surface Mercury Film Deformation on the Breakdown Voltage of a Sub-Nanosecond Pulse Discharge Tube

A sub-nanosecond pulse discharge tube is a gas discharge tube which can generate a rapid high-voltage pulse of kilo-volts in amplitude and sub-nanoseconds in width. In this paper, the sub-nanosecond pulse discharge tube and its working principles are described. Because of the phenomenon that the deformation process of the mercury film on the electrode surface lags behind the charging process, the mercury film deformation process affects the dynamic breakdown voltage of the tube directly. The deformation of the mercury film is observed microscopically, and the dynamic breakdown voltage of the tube is messured using an oscillograph. The results show that all the parameters in the charging process, such as charging resistance, charging capacitance and DC power supply, affect the dynamic breakdown voltage of the tube. Based on these studies, the output pulse amplitude can be controlled continuously and individually by adjusting the power supply voltage. When the DC power supply is adjusted from 7 kV to 10 kV, the dynamic breakdown voltage ranges from 6.5 kV to 10 kV. According to our research, a kind of sub-nanosecond pulse generator is made, with a pulse width ranging from 0.5 ns to 2.5 ns, a rise time from 0.32 ns to 0.58 ns, and a pulse amplitude that is adjustable from 1.5 kV to 5 kV.     

中国南方志留系油气地质特征与勘探方向

中国南方志留系勘探程度较低,制约了对志留系自身油气成藏特点的研究和认识。从烃源岩的时空分布、优质烃源岩的发育环境、生烃史3个方面分析了中国南方上奥陶统-志留系的烃源条件;分析了志留系发育碎屑岩、碳酸盐岩两类储层的条件,对中国南方志留系油气成藏的基本特点进行了总结。该区上奥陶统-志留系优质烃源岩主要发育于上奥陶统五峰组和下志留统龙马溪组底部,以好-最好烃源岩为主,川东南-鄂西渝东区上奥陶统-下志留统烃源条件最好。上述两类储层均以低孔低渗-特低孔低渗为特征,其中,碎屑岩是主要的储集岩类。下志留统龙马溪组为优势盖层发育层位,是一套良好的区域性盖层。扬子区志留系泥岩具有较低孔隙度、较低渗透率、高突破压力、以超微孔为主的物性和孔隙结构特征,现今演化程度虽高,但仍具有良好的封盖能力。志留系天然气具油型气特征,并可能与储层中原油裂解成气有关,至少具有2期油气生成和运聚过程。结论认为：川东南-鄂西渝东区为志留系天然气勘探最有利区,江汉平原南部冲断褶皱区和下扬子海安地区则为勘探有利区。     

湍流射流点火对天然气发动机燃烧特性影响的试验研究

湍流射流点火（Turbulent Jet Ignition,TJI）是一种有效的燃烧增强技术,可提供更高的点火能量,使发动机稳定着火,且可以提高燃烧压力和燃烧速率,缩短燃烧持续期,是实现发动机稀薄燃烧的有效手段。基于一台带有预燃室的点燃式单缸试验机,开展了TJI模式下天然气发动机性能的试验研究。首先,研究了不同过量空气系数下TJI对天然气发动机动力性能、排放性能及燃烧特性的影响,并与火花塞点火（Spark Ignition,SI）模式进行对比;其次,在稀燃条件下分别探究了进气增压和预燃室喷氢对天然气发动机动力性、经济性及燃烧过程的优化作用。结果表明：TJI的使用可有效拓展天然气发动机的稀燃极限,且燃烧滞燃期和燃烧持续期均更短,放热率更高;过量空气系数1.5为甲烷TJI最佳稀燃工况,此时燃油消耗率最低,且可实现氮氧化物近零排放;此外,采用进气增压的方式可以提高TJI发动机在高负荷下的经济性;TJI模式下,相较于预燃室喷甲烷,预燃室喷氢气可进一步缩短滞燃期和燃烧持续期,提高放热率,达到提升TJI性能的效果。