INDUCED OSCILLATIONS GENERATED BY PROTECTIVE THRESHOLD POLICIES IN THE MANAGEMENT OF EXPLOITED POPULATIONS

Abstract Management and conservation of exploited populations have been a central issue in theoretical and empirical studies. In this work, it is shown that threshold policies can induce cyclic behavior in an otherwise exploited stable population as a consequence of the combination of harvest pressure and excessively protective threshold densities. Moreover, the dynamical outcomes generated by these extremely protective policies may vary according to the initial densities. These results may be of significant concern in conservation as well as in management of exploited population.     

On Mixed Pressure-Velocity Regularity Criteria to the Navier-stokes Equations in Lorentz Spaces,Part Ⅱ:The Non-slip Boundary Value Problem

This paper is a continuation of the authors recent work [Beir?o da Veiga, H.and Yang, J., On mixed pressure-velocity regularity criteria to the Navier-Stokes equations in Lorentz spaces, Chin. Ann. Math., 42(1), 2021, 1–16], in which mixed pressure-velocity criteria in Lorentz spaces for Leray-Hopf weak solutions of the three-dimensional NavierStokes equations, in the whole space R~3 and in the periodic torus T~3, are established. The purpose of the present work is to extend the result of mentio...     

A correlation of the isentropic exponents of real gases

In previous publications, three isentropic exponents, k_pv, k_Tv, k_pT, have been introduced, which when used in place of the classical isentropic exponent k = c_p/c_v in the ideal gas isentropic change equations, the latter can describe very accurately the isentropic change of real gases. The present work provides a general method for determining the values of k_pv, k_Tv, k_pT within the ranges of reduced pressure p_r = 0 to 10 and of reduced temperature T_r = 1 to 3.5, thus allowing the calculation of the isentropic flow of those real gases for which no detailed thermodynamic data are available. The accuracy obtained is limited only by the accuracy of the generalized Lee-Kesler equation of state, which is employed in the method developed.     

声场干涉结构相似度匹配的目标运动参数估计

针对水中运动声源定位问题,建立了一种基于声场干涉结构谱向量相似度匹配的目标运动参数估计方法。结合声场干涉结构水平纵向相关特性,利用目标辐射噪声LOFAR谱图中不同频率的谱值序列,基于两方位-两距离目标运动要素计算方法获取的目标距离解向量,构造声场干涉结构谱向量相似度匹配代价因子,实现目标运动参数估计。仿真数据与试验数据验证结果表明:在绘制的目标运动要素解算结果可视化分布图中可清晰呈现出目标初距、航向和速度结果。该算法实现过程简单、解算效率高,对目标方位误差有较好的鲁棒性。     

聚呲咯的研究

本文研究了不同电化学氧化聚合条件下所得聚吡咯的红外光谱,X射线光电子能谱、元素分析、X射线衍射图及扫描电子显微镜图等。对聚吡咯的电导性、电导率的依赖性、化学结构及结晶性等进行了讨论。     

Metabolic profiling of yeast culture using gas chromatography coupled with orthogonal acceleration accurate mass time-of-flight mass spectrometry: Application to biomarker discovery

Yeast and yeast cultures are frequently used as additives in diets of dairy cows. Beneficial effects from the inclusion of yeast culture in diets for dairy mammals have been reported, and the aim of this study was to develop a comprehensive analytical method for the accurate mass identification of the ‘global’ metabolites in order to differentiate a variety of yeasts at varying growth stages (Diamond V XP, Yea-Sacc and Levucell). Microwave-assisted derivatization for metabolic profiling is demonstrated through the analysis of differing yeast samples developed for cattle feed, which include a wide range of metabolites of interest covering a large range of compound classes. Accurate identification of the components was undertaken using GC-oa-ToFMS (gas chromatography-orthogonal acceleration-time-of-flight mass spectrometry), followed by principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) for data reduction and biomarker discovery. Semi-quantification (fold changes in relative peak areas) was reported for metabolites identified as possible discriminative biomarkers (p-value <0.05, fold change >2), including d-ribose (four fold decrease), myo-inositol (five fold increase), l-phenylalanine (three fold increase), glucopyranoside (two fold increase), fructose (three fold increase) and threitol (three fold increase) respectively.     

化妆品中挥发性有机溶剂的通用检测方法

以化妆品配方中常见及禁用的36种有机溶剂为研究模板,建立了化妆品中挥发性有机溶剂残留评价初筛知识库、确证知识库和定量方法。初筛知识库包括双柱保留指数知识库和NIST质谱库。双柱保留指数知识库以保留指数为定性指标,选择极性的VF-1301ms和非极性的DB-5ms两根色谱柱,用顶空气相色谱-质谱法考察了36种有机溶剂在两种色谱分离系统中的保留特性。利用NIST MS search 2.0作为检索工具,同时建立了36种挥发性有机溶剂的顶空气相色谱-质谱定量方法。样品经60 ℃、30 min静态顶空后以连接了VF-1301ms石英毛细管色谱柱的气相色谱-质谱仪检测,外标法定量。方法检出限为0.01~3.3 μg/g,加标回收率为60.77%~126.60%。该方法从通用性的角度,为化妆品中挥发性有机溶剂残留的筛查、鉴别和定量提供方法,部分解决了测定化妆品中挥发性有机溶剂时需要针对不同检测目标建立不同方法以及潜在溶剂存在备选筛查的问题。     

(-)-（3S, 6R）-3, 6-羟基-10-甲基十一酸及其三聚体的全合成

以廉价易得的异戊基溴为起始原料,以烯丙基二异松莰烷基硼烷参与的不对称烯丙基化反应和Yamaguchi酯化反应为关键步骤,实现了对(-)-(3S,6R)-3,6-二羟基-10-甲基十一酸(总收率27.5％)及其三聚体(总收率24.5％)的不对称全合成。     

高效液相色谱二氮杂冠醚键合相的合成及性能研究

本文报道在硅胶表面进行固－液相反应，合成硅胶键合二氮杂冠醚高效液相色谱固定相。采用有机元素分析、热分析、红外光谱、金属离子的络合容量测定等对键合材料进行鉴定和表征，并对其色谱性能进行了研究。