Contract-theoretic Approach for Delay Constrained Offloading in Vehicular Edge Computing Networks

Mobile Networks and Applications - Mobile Edge Computing (MEC) is a promising solution to improve vehicular services through offloading computation to cloud servers in close proximity to mobile...     

Reductive debromination of polybrominated diphenyl ethers in anaerobic sediment and a biomimetic system

Because of the bioaccumulation of penta- and tetrapolybrominated diphenyl ether (PBDE) flame retardants in biota,the environmental biotransformation of decabromodiphenyl ether (BDE-209) is of interest. BDE-209 accounts for more than 80% by mass of PBDE production and is the dominant PBDE in sediments. Most sediments are anaerobic and reports of microbial reductive dehalogenation of hydrophobic persistent organohalogen pollutants are numerous. Reductive debromination of BDE-209 in the environment could provide a significant source of lesser-brominated PBDEs to biota. Moreover, a recent study showed that BDE-209 debrominates in sewage sludge, and another demonstrated that some halorespiring bacteria will debrominate BDE-209. To determine whether reductive debromination of BDE-209 occurs in sediments, parallel experiments were conducted using anaerobic sediment microcosms and a cosolvent-enhanced biomimetic system. In the biomimetic system, reductive debromination occurred at rates corresponding to bromine substitution levels with a BDE-209 half-life of only 18 s compared with a halflife of almost 60 days for 2,2',4,4'-tetrabromodiphenyl ether. In sediment, the measured debromination half-life of BDE-209 was well over a decade and was in good agreement with the predicted value obtained from the biomimetic experiment. Product congeners were predominantly double para-substituted. BDE-209 debrominated in sediment with a corresponding increase in nona-, octa-, hepta-, and hexa-PBDEs. Nine new PBDE congeners appeared in sediment from reductive debromination. Given the very large BDE-209 burden already in sediments globally, it is important to determine whether this transformation is a significant source of lesser-brominated PBDEs to the environment.     

影响热轧板带精轧机工作辊寿命的因素分析

介绍了鞍钢热轧板带精轧机工作辊工作状况,对影响轧辊使用寿命的主要因素进行了分析,提出了具体改进措施,如在轧制过程中确保充足的冷却水量、投入热轧油、选择适宜的轧辊存放温度等。实施后减少了轧辊磨损量和轧辊剥落,降低了轧辊断裂出现几率,提高了工作辊使用寿命。     

涤纶毛条生产中毛粒的形成原因及其控制措施

讨论了涤纶毛条生产过程中纺丝、拉伸、卷曲、制条等工艺参数及设备条件对毛粒的影响。为了减少毛粒,采用了合理的纺丝和制条工艺,并对后纺设备进行适当改造。涤纶毛条中的毛粒得到了有效控制,从而生产出优质涤纶毛条产品。     

用于频率综合的电荷泵锁相环电路设计

在阐述了锁相环频率综合的工作原理、分析和设计方法的基础上,结合环路稳定性和相位噪声两方面因素对锁相环电路进行了建模及分析。采用安捷伦公司的ADS软件对锁相环进行了系统设计及仿真,并采用Cadence公司的Spectre-RF系列软件进行了锁相环具体电路设计和仿真。采用该方案设计的锁相环输出频率范围18.15 23 GHz,相位噪声-90 dBc/Hz,锁定时间小于5μs。     

深圳市抛石填海区物探方法研究

在深圳某抛石填海区,由于存在较厚的淤泥层,而且在淤泥层中大量的分布着大小不均的石块,在物探作业的时候,往往难以探测到淤泥下面的基岩面,本文基于以上情况,通过对几种常规的物探方法的对比,从理论到实践,从中找到了最优的勘探方法,为以后从事此类工程的物探工作者提供一些借鉴。     

用气液色谱研究1,3—丙二醇体系的盐效应

用色谱法了不同温度下，低碳醇，水在含盐（乙酸钾、硫氰酸钾、硫氰酸钠）１，３－丙二醇中无限稀释活度系数，醇、水的相对挥发度及含盐溶剂的选择度。     

The characteristic curvature (Cc) definition and its use in assessing Cc for single ionic surfactants

The hydrophilic–lipophilic-difference (HLD) is a set of empirical equations that correlate the formulation conditions at phase inversion (HLD = 0). Based on partition studies for nonionic surfactants, the HLD can be interpreted as a normalized chemical potential difference between the surfactant dissolved in water and oil. The net-average curvature (NAC) model extrapolates this interpretation into a curvature form that has been used to fit and predict the phase behavior of surfactant-oil–water (SOW) systems. The curvature interpretation led to renaming the HLD surfactant parameter, sigma (σ), as the characteristic curvature (Cc). This work tests the validity of the curvature interpretation of the HLD, and the Cc concept, for single ionic surfactants and the use of this concept as a method to assess the Cc without the use of reference surfactants or alcohols. To this end, the net curvature of six anionic and two cationic surfactants was evaluated from solubilization data at the characteristic condition of 25°C, no added cosolvent, in the presence of an oil mixture with equivalent alkane carbon number (EACN) of zero, and as a function of salinity. These studies showed that the original HLD equation for ionic surfactant could not be interpreted as chemical potential or curvature because a salinity prefactor (coefficient) “bi” was missing. The revised equation, HLD_bi = bi∙ln(S)-k_bi∙EACN+Cc_bi -a_Tbi∙(T-25°C), could now be interpreted as a curvature expression, and it was demonstrated that Cc could be obtained from curvature using the expression Cc = Cc_bi/bi. This single surfactant method produces uncertainties that, for most surfactants, ranged from 0.2 to 1 Cc units, similar to the uncertainty obtained with the conventional method of Cc determination using mixtures of test and reference surfactants.     

超临界水连续合成纳米氧化锌及其光催化性能

采用超临界水连续合成法制备了纳米氧化锌颗粒并对其光催化性能进行了研究。当反应温度为 385 ℃, 反应压力为25 MPa, 反应时间为40 s, 反应物Zn₂⁺和OH^-的浓度分别为0.075、0.3 mol/L时, 获得了粒径为30 nm的球形纳米氧化锌。以甲基橙溶液为光催化模型物,在紫外光照射下,所制备的纳米氧化锌对甲基橙的降解率可达到100%,并且纳米氧化锌的浓度和分散性对光催化效率有显著影响。     

纳米耐磨涂料的国内外研究概况

概述了国内外纳米耐磨涂料的研究情况.介绍了一些最新产品,并就纳米耐磨涂料的应用前景进行了展望.