Simultaneous determination of three curcuminoids in Curcuma longa L.by high performance liquid chromatography coupled with electrochemical detection

A novel method for analysis of three active components curcumin, demethoxycurcumin and bisdemethoxycurcumin in Curcuma longa L. was developed by HPLC coupled with electrochemical detection. Three curcuminoids were well separated on a C18 column and detected with high sensitivity. A mobile phase containing acetonitrile and 10 mM Na2HPO4-H3PO4 （pH 5.0） （50：50, v/v） was used. Good linearity was obtained in the range of 0.208-41.6, 0.197-39.4, and 0.227-114μM for curcumin, demethoxycurcumin and bisdemethoxycurcumin respectively. The limit of detection reached up to 10 ？ 8 M, which was lower than that by UV detection. The relative standard deviations （RSDs） ranged from 1.06%to 1.88%for intra-day precision and from 4.30%to 5.79%for inter-day precision, respectively. The proposed method has been applied in real herb sample and recoveries ranging from 86.3%to 111%were obtained.

Numerical Simulation and Performance Assessment of a Nanoparticle Enhanced Vapour Compression Refrigeration System

Cooling in industrial production and refrigeration of perishable and non- perishable products is common practice throughout the world. Research studies have been conducted both experimentally and numerically to simulate Vapor Compression Refrigeration System (VCRS) and its performance respectively, however, experimental procedure often seems to be expensive and time-consuming to carry out due to the function of many variables. This study was therefore designed to numerically simulate the performance assessment of a nanoparticle enhanced VCRS. A numerical model of a vapor compression refrigeration system was developed using standard refrigeration equations on each of the major components of the refrigeration system such as compressor, evaporator, condenser and expansion valve. The model was then simulated on a MATLAB platform with a CoolProp installed packages via Python under two different simulation cases. In the first case, the mass fractions were varied for CuO, TiO2 and Al2O3 nanoparticles while their densities remained constant and a reversed condition was investigated for the second case. The results showed that both the refrigerating effect and the Coefficient Of Performance (COP) of the system increase as both the mass fraction and density of all the nanoparticles increases. It also shows that the compressor work decreases as both the mass fraction and density of all the nanoparticles were increased. On comparing the computational and numerical analysis results, the study established no significant difference in terms of COP and the use of nanoparticles were found to have improved the COP of the system.

Public Transit Performance Evaluation Using Data Envelopment Analysis and Possibilities of Enhancement

This study evaluates the operational performance of all routes of Sajha Bus Yatayat operating inside Kathmandu valley using Data Envelopment Analysis (DEA) in terms of efficiency and effectiveness score. This approach allows us to access the relative performance of transit system in absence of historical data and research to compare with. To explore the possibility of enhancing the performance, scenarios were created for relatively underperforming routes and long route problem by changing the most important input variable and output variables accordingly with regression model where it was relevant. Partial Least Squares (PLS) regression was used to determine the most influential input variables to the output variables. DEA was conducted to access the performance of all routes under these scenarios. Underperforming routes except the longest route under the first set of scenarios, emerge to be better performing efficiently without considerable negative deviation in effectiveness. The result of second set of scenarios for long route problem suggests that the longest route’s performance can be enhanced significantly upon proper route alignment. Scenarios development and evaluation can help lead transit companies to explore the strategies to facilitate operational performance enhancement.

Modeling and verifying So S performance requirements of C4ISR systems

System-of-systems （SOS） engineering involves a com- plex process of refining high-level SoS requirements into more detailed systems requirements and assessing the extent to which the performances of to-be systems may possibly satisfy SoS capa- bility objectives. The key issue is how to model such requirements to automate the process of analysis and assessment. This paper suggests a meta-model that defines both functional and non- functional features of SoS requirements for command and control, communication, computer, intelligence, surveillance reconnais- sance （C41SR） systems. A domain-specific modeling language is defined by extending unified modeling language （UML） con- structed of class and association with fuzzy theory in order to model the fuzzy concepts of performance requirements. An effi- ciency evaluation function is introduced, based on Bezier curves, to predict the effectiveness of systems. An algorithm is presented to transform domain models in fuzzy UML into a requirements ontology in description logic （DL） so that requirements verification can be automated with a popular DL reasoner such as Pellet.

Standard Operating Procedure of Houttuynia cordata Thunb.Plastic Greenhouse Cultivation

This standard operating procedure stipulated the natural condition of pro- ducing area, cultivation technique, disease and pest control, harvest, quality stan- dard, packaging, transportation and storage of H. cordata, in order to provide a ba- sis for the standard cultivation of H. cordata.

谷物及其制品中11种真菌毒素污染水平的测定与分析

建立了超高效液相色谱-串联质谱技术同时检测谷物及其制品中11种真菌毒素的方法。样品经84%乙腈水溶液振荡提取,离心、氮吹,复溶,选择0.1%甲酸水-甲醇为流动相梯度洗脱目标化合物,以反相色谱柱进行分离,采用电喷雾离子源正离子模式和多反应监测模式进行质谱分析。结果表明,11种真菌毒素在一定浓度范围内线性关系良好,方法检出限为0.1~2.0μg·kg^(-1),定量限为0.4~6.0μg·kg^(-1)。在三个添加水平下,平均回收率为94.5%~111.7%,相对标准偏差为0.85%~8.98%。应用本方法对小麦、玉米、大米、小麦粉等790批次典型谷物及其制品中11种真菌毒素污染水平进行研究,其中182批次谷物样品中检出真菌毒素,检出率为29%,具有一定的地域性和季节性;小麦粉有1批次样品检出玉米赤霉烯酮,检出率低于小麦样品的。

APPLICATION OF WAVE LETS TO OPTIMAL SHOCK AND IMPACT ISOLATION

The limiting performa nce analysis is used to study the optimal shock and impact isolation of mechanic al systems. The use of wavelets to approximate time-domain control functions is investigated. The formulation for numerical computation is developed. Numerical examples include the optimal shock isolation of a SDOF system and the optimal i mpact isolation of a MDOF system. Computational results show that compactly supp orted wavelets can represent abrupt changes in control functions better than tri gonometric series and considerably increase computational efficiency.

NONPARAMETRIC POLYSPECTRAL ESTIMATORS FOR k-TH-ORDER (ALMOST) CYCLOSTATIONARY COMPLEX PROCESSES

Higher-order almost cyclostationary complex processes are complex random signals with almost periodically time-varying statistics, which is important to the research of non-Gaussian signals in information system. In tins paper, smoothed polyperiodograms are proposed for related to cyclic polyspectral estimation and are shown to be consistent and asymptotically complex normal. Asymptotic covariance expressions are derived along with their computable forms.

Saving Energy for Wireless Transmission:An Important Revelation from Shannon Formula

The reduction of power consumption is important for wireless communications and networks.To develop the energy-saving technologies for future wireless transmissions and networks,this paper presents two basic study points:1)The multiple events are merged into a single event;2)the high-order mode is changed to the low-order mode.For this rea⁃son,we seek that multiple events in wireless transmission links are fused into a single event from Shannon formulas.We also analyze the relationship between the information modula⁃tion and the error correction,and give a fusion structure of error-corrected modulation.The energy-saving performance of the error-corrected modulation method is further analyzed through comparison with the traditional methods of modulation plus error correction.The re⁃sults of numerical analysis demonstrate the wireless energy saving methods for wireless sys⁃tems based on Shannon formulas are the achievable efficient schemes.

考虑材料时变性的服役中小跨径桥梁横向地震响应分析

构件材料性能会随服役时间的增加而退化,并导致桥梁结构抗震性能存在时变性。为探讨不同服役期下中小跨径桥梁抗震性能变化规律,以3跨预应力混凝土连续桥梁为例,通过分析材料力学性能指标时变性,量化不同服役期构件力学分析模型参数,并考虑桥墩、挡块及支座等构件力学性能退化,采用OpenSees软件建立桥梁有限元分析模型。基于非线性时程分析结果,揭示服役中小跨径桥梁横桥向地震响应时变性。研究结果表明,随着服役时间的增加,材料力学性能发生退化,使中小跨径桥梁各构件抗震能力下降;相同水平地震作用下,中小跨径桥梁主梁及挡块位移响应随服役时间的增加而降低,而桥墩损伤程度加剧,构件震害程度与不考虑构件力学性能时变性时相差较大,其中板式橡胶支座刚度及摩擦系数时变性是关键。因此,在服役中小跨径桥梁抗震分析中,有必要同时考虑桥墩、挡块及支座力学性能退化。

兆瓦级高速永磁同步电机偏心状态下电机性能及转子振动特性分析

在电机运行过程中,气隙偏心是一种常见的故障状态,会危害到电机的安全可靠运行,而该问题在大容量高速永磁同步电机中更为严重。因此,本文以一台兆瓦级高速永磁同步电动机为例,研究了气隙偏心对电机电磁性能以及其引发的不平衡磁拉力对转子振动特性的影响。首先,推导了静、动以及混合偏心状态下的不平衡磁拉力表达式。然后,建立了各偏心状态下的电机有限元模型,定量分析了不同偏心程度所引发的不平衡磁拉力变化情况。在此基础上,计算了电机转子系统的动力响应,详细讨论了各种偏心对转子系统轴心轨迹和电磁性能的影响。结果表明,不同偏心状态下不平衡磁拉力存在明显差异,在混合偏心时动偏心会削弱静偏心对转子振动的影响,偏心将增加气隙磁密的偶次谐波且增大转矩脉动。

科普短视频脚本专业性与修辞特征对传播绩效的影响:独立作用与交互机制检验

发现和识别科普短视频传播绩效的影响因素,对科普短视频脚本设计优化、促进科普知识传播均具有重要意义。提取18个健康知识科普抖音号近1年发布的4378个短视频解说脚本与它们的点赞数、收藏数、转发数与评论数,采用文本挖掘与回归分析等方法,考察专业性与强、弱两类修辞短语应用比例对科普短视频传播绩效的独立与交互影响,并借助中介效应检验模型讨论了点赞的形成机理。结果发现:专业性对点赞数、收藏数与转发数呈现倒U型影响,但对评论数是负向影响;强修辞短语的使用能促进点赞数、转发数和评论数,但过多使用强修辞短语有时会抑制专业性内容的接受度;点赞数分为直接性点赞数与转发数带来的间接性点赞数,而前者与专业性为负相关关系。

微缝吸声板吸声性能探讨

为了研究微缝吸声板的几何参数对其吸声性能的影响,以微孔吸声板理论为基础,设计制作了微缝吸声板,对微缝吸声板进行阻抗管试验并与仿真模拟结果进行对比分析,仿真结果与试验结果基本一致。通过仿真不同几何参数下微缝吸声板的相对声阻抗,计算得出吸声系数进行对比,结果表明,当缝宽和膜厚相对增加时,微缝吸声板的吸声峰值和吸声带宽均略有减小。

枯草芽孢杆菌DC-1产维生素K_(2)的发酵条件优化

为提高微生物发酵法生产维生素K_(2)的产量和多样性,对枯草芽孢杆菌DC-1的发酵条件进行优化。采用单因素试验对其发酵条件包括碳源、氮源和无机盐进行初步优化,通过Plackett-Burman(PB)试验筛选出对DC-1产维生素K_(2)具有显著性影响的因素,应用响应面Box-Behnken设计优化获得DC-1的最优发酵条件。结果表明,DC-1产维生素K_(2)的最优发酵条件为甘油添加量36.5 g/L、糖蜜添加量31.8 g/L、黄豆粉添加量32.5 g/L、KH2PO_(4)浓度0.3 g/100 mL、K_(2)HPO_(4)·3H_(2)O浓度0.8 g/100 mL、Mg SO_(4)·7H_(2)O浓度0.7 g/100 mL、Na Cl浓度0.5 g/100 mL。在该条件下,MK-7产量达到94.66 mg/L,比初始发酵条件提高了48.04%;同时菌株DC-1产维生素K_(2)的多样性增加,经液相色谱-质谱联用(liquid chromatograph mass spectrometer,LC-MS)鉴定能同时产5种MK同系物,分别为MK-2、MK-3、MK-4和MK-7,其中一个类似物未能在高分辨率质谱中找到,根据保留时间推测其为MK-5或MK-6,可为维生素K_(2)的工业化生产和探索维生素K_(2)同系物的生物活性奠定基础。

离子液体基磁性固相萃取-高效液相色谱法测定饮料中的合成色素

国家对合成色素使用量有严格限量标准,有效萃取和测定食品中合成色素对保障食品安全有重要意义。采用红外光谱、透射电镜和振动样品磁强计等对合成的聚合离子液体修饰的磁性纳米材料的结构、形貌和磁性进行了表征,将此磁性纳米材料作为磁性固相萃取(magnetic solid-phase extraction,MSPE)吸附剂,研究了其对4种合成色素(柠檬黄、日落黄、诱惑红和亮蓝)的萃取性能,结合MSPE与高效液相色谱技术,对影响萃取效率的吸附剂用量、吸附时间、解吸时间和盐的含量等参数进行了优化。研究结果表明:根据吸附剂对典型阴/阳离子型染料的吸附结果,推断4种合成色素的有效萃取归因于吸附剂与分析物之间存在的强静电引力以及π-π和疏水作用等多重作用;在吸附剂用量为10 mg、吸附时间为20 min、解吸剂为1 mL乙腈/盐酸(体积比9∶1)和解吸时间为10 s的优化萃取条件下,4种色素具有良好的线性(决定系数为0.9922~0.9975),检出限(S/N=3)和定量限(S/N=10)分别为1~3μg/L和2.5~10μg/L;该方法能成功用于碳酸饮料健力宝和菠萝啤中合成色素的测定,3个质量浓度下(日落黄、诱惑红和亮蓝均为25、100、250μg/L,柠檬黄为50、200、500μg/L)的加标回收率为71.4%~113.0%,相对标准偏差小于10.9%(n=3)。本研究为食品中合成色素的分析提供了一种很有前景的样品前处理方法。

结构参数对CO_(2)离心压缩机的性能影响分析

为研究各关键结构参数对CO_(2)离心压缩机性能的影响,针对某MW级压缩CO_(2)储能系统低压段中的一级进行了一维设计和三维数值模拟。基于该模型研究了叶片数、叶顶间隙、叶片出口安装角和叶轮出口相对宽度4种关键结构参数对压缩机性能的影响。研究结果表明:叶片出口安装角和叶顶间隙对离心压缩机性能的影响最大,其次是叶片数和叶轮出口相对宽度;增加叶片出口安装角度可显著提高压缩机的做功量及压比,但过大角度会使得流动损失增大而造成效率的降低;随着叶顶间隙的增大,泄漏流动会更加严重,从而影响压缩机的性能;减少叶片数量会减小叶片对流体的约束,更易产生流动分离;叶轮出口相对宽度与压缩机设计流量相关,过小的相对宽度会增大摩擦、泄漏等损失,进而影响压缩机性能及运行工况范围。

CaCl_(2)与BaCl_(2)复配对水泥浆抗负温劣化和硫酸盐侵蚀的试验研究

随着我国“西部大开发”和“一带一路”发展战略的深入推动,冻土区施工日渐增多,负温劣化和硫酸盐侵蚀对水泥浆性能的负面影响给工程建设带来了安全隐患。通过-20℃恒温无预养水泥浆水化试验,利用XRD、SEM、TG、CT和力学测试等手段对水泥浆水化产物、孔隙结构、力学性质等进行分析,综合评价了CaCl_(2)-BaCl_(2)复配使用对水泥浆在负温和硫酸盐环境下水化性能的影响。试验结果表明:相比于单一使用CaCl_(2),添加BaCl_(2)不仅可以促进水泥浆水化程度,还可与SO_(4)^(2-)反应,减少高硫型水化硫铝酸钙(又称钙矾石,AFt)的生成,提升水泥浆抗硫酸盐侵蚀能力;CaCl_(2)-BaCl_(2)复配使用时BaCl_(2)的合理掺量为10wt%~15wt%,此时水泥浆具有相对最优的水化产物、孔隙结构和力学性质,其抗负温劣化和抗硫酸盐侵蚀能力也得到了显著提高。该研究结果可为冻土区工程建设提供理论参考和技术借鉴。

柠条资源饲料化开发技术及在反刍动物生产中应用的研究进展

柠条是我国西北地区防风固沙、改善生态的重要豆科灌木,具有生物量大和抗逆性强等优点,富含木质纤维素、氨基酸、多酚及黄酮等物质,具备较高的营养价值和潜在利用价值。文章综述了柠条的营养特性、饲料化利用方式及饲用价值,总结了其在反刍动物中的饲喂效果,剖析了柠条饲料化利用难点及利用方式,同时,对柠条未来研究与开发方向进行了展望,为柠条非常规饲料资源的深入开发与利用提供参考。

超支化聚酰胺-胺类阻垢剂制备及性能研究

采用乙二胺(EDA)、二乙烯三胺(DETA)、和三乙烯四胺(TETA)为反应中心核,甲醇为溶剂,丙烯酸甲酯(MA)为原料,通过迈克尔加成和酰胺化反应,合成3种不同类型的超支化聚酰胺-胺[PAMAM(EDA/DETA/TETA)],后用羟基亚乙基二膦酸(HEDP)分别对其进行改性,制备出3种端膦酸基超支化聚酰胺-胺类型的阻垢剂[PAMAM(EDA/DETA/TETA)-H2PO_(3)],并对其阻垢性能和阻垢机理进行研究。结果表明:超支化聚酰胺-胺的阻垢率未达到标准,而改性后的端膦酸基超支化聚酰胺-胺具有优异的阻垢性能,其中在高矿度下加药浓度为500 mg·L^(-1),PAMAM(EDA)-H2PO_(3)对CaSO_(4)、CaCO_(3)垢的阻垢率分别达到98.5%和90.1%,而且还发现此类型的阻垢剂具有耐高温、pH值应用范围广、持续时间长等优点。再结合分散性能测试和垢样分析,发现其阻垢机理主要与支化分子结构、聚合物的高分散性和引入的官能团有关。

固相萃取/高效液相色谱-串联质谱法同时测定氟橡胶、氟树脂及其制品中多种全氟和多氟烷基化合物

基于固相萃取/高效液相色谱-串联质谱(HPLC-MS/MS)技术,建立了氟橡胶、氟树脂及其制品中37种全氟和多氟烷基化合物(PFASs)的定量分析方法和19种PFASs的定性分析方法。采用25 mmol·L^(-1)乙酸铵甲醇/乙腈(1∶1,体积比)溶液对氟橡胶类、氟树脂固体类和氟树脂纺织类样品进行超声振荡提取;采用四甲基叔丁基醚(MTBE)对氟树脂液体类样品进行超声振荡提取,提取液经Envi-carb和Oasis WAX柱固相萃取,并用甲醇和0.1%氨水甲醇洗脱。在10 mmol·L^(-1)乙酸铵溶液-乙腈流动相下采用Acquity UPLC BEH C18(2.1 mm×100 mm,1.7μm)色谱柱对目标化合物进行梯度洗脱分离,多反应监测模式(MRM)进行采集,内标法定量。结果表明,在5、10、20 ng·g^(-1)(氟橡胶类)和2.5、5、10 ng·g^(-1)(氟树脂类)加标水平下,氟橡胶类、氟树脂固体类、氟树脂纺织类和氟树脂液体类样品中37种PFASs的回收率分别为81.3%~109%、60.9%~111%、87.8%~125%和88.7%~140%;相对标准偏差(RSD)分别为1.4%~28%、1.5%~22%、1.8%~27%和1.4%~19%;检出限(LOD)分别为0.03~0.3 ng·g^(-1)、0.03~0.8 ng·g^(-1)、0.02~2 ng·g^(-1)和0.04~1 ng·g^(-1);定量下限(LOQ)分别为0.07~0.9 ng·g^(-1)、0.08~2 ng·g^(-1)、0.06~6 ng·g^(-1)和0.1~4 ng·g^(-1)。19种PFASs的回收率为0.300%~208%,适于半定量和定性分析。使用该方法测定10个氟橡胶和氟树脂样品,Σ_(37)PFASs含量为9.73~66.17 ng·g^(-1)。该方法操作简便、灵敏度高且定量准确,可为研究氟橡胶、氟树脂及其制品中PFASs的残留情况及完善我国出口贸易和国内履约执法监测提供技术支撑。