Analyzing the coexistence of DSRC and Wi-Fi networks using the Poisson line Cox process

Vehicular networks can aid in traffic monitoring, autonomous driving, and car accidents prevention. Yet, the deployment of these networks has been delayed due to the limited spectrum, especially for the case of unlicensed operations. To handle this issue, the Federal Communications Commission (FCC) proposed to permit Wi-Fi devices to operate in the 5.9 GHz band allocated to the intelligent transportation system (ITS). In a recent work, we analyzed the impact of the coexistence of dedicated short range communications (DSRC) and Wi-Fi on future DSRC network deployments by developing a stochastic geometry analytical model that considers a dynamic medium access probability (MAP) of DSRC nodes which uses carrier sense multiple access with collision avoidance (CSMA/CA). This previous work was based on the standard 2D homogeneous Poisson Point Process (PPP) model. In this work, we model the roads using the more applicable but more complex Poisson line process (PLP) Cox point process. We generate performance metrics represented through coverage probability and area system throughput, and we compare these results to our earlier work. The importance of this work is two-fold. First, it allows a further understanding of the impact of DSRC-Wi-Fi coexistence on future DSRC network deployments, and second, it highlights the effectiveness of the PLP in modeling the distribution of vehicles in an area by producing more accurate performance results.     

单斜ZnP2负极材料的锂化机理及性能

过渡金属磷化物电位低且比容量高, 是有发展前景的锂离子电池(LIBs)负极材料. 其中, ZnP₂属于双活性负极材料, Zn与P都能与Li⁺发生反应, 储Li⁺性能更具有竞争力. 但是, 对于ZnP₂的锂化机理及产物尚不明确. 采用第一性原理计算和电化学测试方法研究了ZnP₂的电子性质和电化学性能, 通过理论计算和实验测试相结合阐述了ZnP₂的锂化机制. 首先, 以密度泛函理论(DFT)计算揭示了ZnP₂的锂化机理、Li⁺扩散路径、势垒和理论比容量(1477 mAh/g). 其次, 通过直流电弧等离子体法及固相烧结法合成ZnP₂, 并测试其首圈放电曲线, 显示放电容量为1439 mAh/g, 与理论计算结果相近. 此外, 薄膜X射线衍射(XRD)检测最终产物成分为LiZn和Li₃P, 与DFT计算结果一致.     

Tutorial review on validation of liquid chromatography–mass spectrometry methods: Part II

This is the part II of a tutorial review intending to give an overview of the state of the art of method validation in liquid chromatography mass spectrometry (LC–MS) and discuss specific issues that arise with MS (and MS–MS) detection in LC (as opposed to the “conventional” detectors). The Part II starts with briefly introducing the main quantitation methods and then addresses the performance related to quantification: linearity of signal, sensitivity, precision, trueness, accuracy, stability and measurement uncertainty. The last section is devoted to practical considerations in validation. With every performance characteristic its essence and terminology are addressed, the current status of treating it is reviewed and recommendations are given, how to handle it, specifically in the case of LC–MS methods.     

On pre-exit joint occupation times for spectrally negative Lévy processes

We adopt a new approach to find Laplace transforms of joint occupation times over disjoint intervals for spectrally negative Lévy processes. The Laplace transforms are expressed in terms of scale functions.     

氮气吹扫和费托合成的脉冲过程以提高α-烯烃的选择性

费托合成可以将煤炭或者生物质气化得到的合成气转化为α-烯烃等重要的化工产品。研究将费托合成和氮气吹扫操作组合成一脉冲过程,在稳定的操作状态下保证费托合成和氮气吹扫交替进行。在传统的费托合成条件下(反应气速为2 000 h^-1,温度为497 K, 压力为 2.0 MPa, 氢碳体积比为2.0)考察了Fe-Co催化剂在脉冲过程中费托合成的活性和选择性。结果表明,N₂吹扫温度和压力分别为517 K和0.2 MPa下的费托合成的C₃烯烷比是未脉冲的相同反应条件下的九倍左右。同时,反应过程中CH₄的选择性和CO的转化率有所下降。在此基础上,通过间歇反应在固定床反应器中进行该脉冲过程,实验结果表明,利用脉冲操作在费托反应中可以获得更高的烯烃选择性。     

一种一致性排序标度方法

针对层次分析法判断矩阵一致性问题,提出了一种新的排序标度方法,证明了采用新方法形成的判断矩阵具有一致性,最后通过实例运用说明了此方法的可行性和有效性.     

基于马尔可夫决策过程的医疗检查预约优化模型

医技部门的医疗检查如电子计算机断层扫描（CT）、核磁共振成像设备（MRI）、X射线（X－rays）常常有如下三种病人类型：门诊病人、住院病人和急诊病人。针对不同病人类型的需求特点，运用马尔可夫决策过程原理和动态规划方法，建立了医疗检查设备的预约优化模型，并证明了模型的最优性质，得出了不同病人类型的最优预约策略。数值算例的结果表明：本文的预约策略不仅易于实施，而且，通过该模型获得的最大收益比按传统先来先预约的模式所获得的收益要大。     

Understanding the Structural Differences between Spherical and Rod‐Shaped Human Insulin Nanoparticles Produced by Supercritical Fluids Precipitation

In this study, the thermal denaturation mechanism and secondary structures of two types of human insulin nanoparticles produced by a process of solution‐enhanced dispersion by supercritical fluids using dimethyl sulfoxide (DMSO) and ethanol (EtOH) solutions of insulin are investigated using spectroscopic approaches and molecular dynamics calculations. First, the temperature‐dependent IR spectra of spherical and rod‐shaped insulin nanoparticles prepared from DMSO and EtOH solution, respectively, are analyzed using principal component analysis (PCA) and 2D correlation spectroscopy to obtain a deeper understanding of the molecular structures and thermal behavior of the two insulin particle shapes. All‐atom molecular dynamics (AAMD) calculations are performed to investigate the influence of the solvent molecules on the production of the insulin nanoparticles and to elucidate the geometric differences between the two types of nanoparticles. The results of the PCA, the 2D correlation spectroscopic analysis, and the AAMD calculations clearly reveal that the thermal denaturation mechanisms and the degrees of hydrogen bonding in the spherical and rod‐shaped insulin nanoparticles are different. The polarity of the solvent might not alter the structure or function of the insulin produced, but the solvent polarity does influence the synthesis of different shapes of insulin nanoparticles.     

Decolorization and mineralization of yellow 5 (E102) by UV/Fe2+/H2O2 process. Optimization of the operational conditions by response surface methodology

In this study, the optimization and implementation of a homogeneous photo-Fenton process for the decolorization and mineralization of a wastewater containing highly concentrated yellow 5 (E102) dye, resulting from an industry placed in the suburbs of Medellin (Colombia), is presented. Response surface methodology was applied as a tool for the optimization of operational conditions such as initial dyestuff concentration, H₂O₂ concentration, and UV-radiation power (number of lamps). The decolorization, degradation and mineralization efficiencies were used as response variables. The following conditions were found to be optimal for decolorization and mineralization of yellow 5: UV radiation of 365 nm (4 W, one lamp), dye concentration of 200 mg/L, Fe²⁺ concentration of 1.0 mM, H₂O₂ concentration of 1.75 mL/L, treatment time of 180 min, Fe²⁺ concentration of 1 mM and pH = 3. Under these conditions (180 min), the photo-Fenton process allowed us to reach ca. 100% of color dye degradation, 99% of COD degradation, and 85% of mineralization (TOC). The scavenging effect of the Cl^– anion on the photodegradation process was also confirmed.     

Direct electrochemical oxidation of a pesticide, 2,4-dichlorophenoxyacetic acid,at the surface of a graphite felt electrode: Biodegradability improvement

Pesticides’ biorecalcitrance can be related to the presence of a complex aromatic chains or of specific bonds, such as halogenated bonds, which are the most widespread. In order to treat this pollution at its source, namely in the case of highly concentrated solutions, selective processes, such as electrochemical processes, can appear especially relevant to avoid the possible generation of toxic degradation products and to improve biodegradability in view of a subsequent biological mineralization. 2,4-D was found to be electroactive in oxidation, but not in reduction, and the absence of hydroxyl radicals formation during the electrochemical step was demonstrated, showing that the pretreatment can be considered as a “direct” electrochemical process instead of an advanced electrochemical oxidation process. The presence of several degradation products in the oxidized effluent showed that the pretreatment was not as selective as expected. However, the relevance of the proposed combined process was confirmed since the overall mineralization yield was close to 93%.