合成尿素用新型CO2原料气除氢催化剂的工业侧流试验

D-438 型合成尿素用CO₂除氢催化剂,虽用铁部分取代贵金属把作为其活性组份,其抗H₂S和CO等毒物性能却得到明显改善。工业装置高压侧流2400h试验结果表明,采用与 DH-2催化剂基本相同的操作条件,在CO₂原料气中总硫、CO和甲醇等毒物含量分别平均增高33%、~2倍和~30%的情况下,其反应沽性与DH-2相当,充分证明D-438催化剂在保持其较高除氢活性和稳定性的前提下,具有较DH-2和CN-101催化剂更好的抗硫化物中毒性能和耐CO含量波动的能力,是一种生产成本较低、抗干扰能力强、性能稳定的催化剂。目前,这一催化剂即将投入工业应用试验。     

表面中毒C207催化剂的曲节因子

采用N_2-CO_2气体稳态法测定了表面中毒C207催化剂的扩散通量,应用平行交联孔模型求得催化剂的曲节因子,按平均孔径计算的曲节因子δ_F:未中毒催化剂3.65,中毒催化剂2.99至3.11;按孔径分布计算的曲节因子δ:未中毒催化剂4.17,中毒催化剂3.45至3.71。     

硫对联醇工况的影响分析

本文在C207甲醇合成铜基催化剂H₂S、COS中毒失活动力学研究的基础上,定量比较了硫化氢、有机硫对铜基催化剂毒害的程度,理论计算和生产实践表明，采用“阶梯”提温的策略操作,在一定时间内可以减缓催化剂中毒失活对甲醉产量的影响。     

Electrolytic reduction of trichloroethylene and chloroform at a Pt- or Pd-coated ceramic cathode

Trichloroethylene (TCE) and chloroform (CF) were electrolytically dechlorinated in a two-compartment cell in which the working electrode (cathode) consisted of an Ebonex ceramic sheet plated with platinum (Pt) or palladium (Pd). The halogenated targets were not reduced using a cathode of untreated Ebonex. Under typical experimental conditions (e.g., cathode potentials E _C = –0.3 V to –1.4 V vs SHE, pH 7.0), transformations were first order in TCE and CF. Reaction kinetics were mass transport limited at E _C < –1.4 V. Transport-limited rate constants were 0.45 cm min^–1 for TCE reduction and 0.42 cm min^–1 for CF. The primary products of CF reduction were methane and hydrochloric acid. For TCE reduction, major products were ethane, ethylene and hydrochloric acid. Carbon and chlorine mass balances were within 5–10%. Current efficiencies ranged from nearly 100% at E _C = –0.5 V (both reactants) to 24.4% for TCE and 16.6% for CF at E _C = –1.4 V. Rate constants for TCE and CF transformations were inversely related to pH in the range 2 < pH < 11. Pt–Ebonex resisted sulfate and chloride poisoning. The Pd–Ebonex electrode quickly lost activity (50% loss in 5–10 min) in 0.1 M K₂SO₄ electrolyte (cathode potential, E _C = –1.15 to –1.4 V vs SHE).     

C3S在纯水和化学外加剂溶液中水化液相的研究

本文研究了C_3S在纯水和化学外加剂溶液中水化时,液相成分的变化规律。发现C_3S在纯水中水化可分为4个阶段,其中第Ⅱ阶段相当于水化诱导期,此阶段中C_3S的溶解速度R_0为常数。化学外加剂的存在并不改变C_3S的水化本质,但能缩短水化诱导期。化学外加剂对C_3S水化速度的影响主要取决于组成该外加剂的阴、阳离子的本质。本研究还通过实验证明了硅酸盐离子对Ca(OH)_2核晶过程的“毒化”作用,为C_3S延迟核晶水化理论提供了直接证据。     

失活甲醇合成铜基催化剂效率因子的正交配置解

本文建立了未中毒与孔口中毒情况下甲醇合成铜基催化剂效率因子的计算模型,用正交配置法计算了失活铜基催化剂在典型工业生产条件(5MPa Lurgi低压合成工艺、10MPa中压联醇工艺、25MPa石脑油制气高压合成工艺)下的效率因子。     

掘进工作面炮烟中毒事故的事故树分析

应用事故树分析方法对掘进工作面炮烟中毒事故的原因进行了分析,通过计算事故树的最小割集、最小径集与基本事件的结构重要度,讨论并提出了预防掘进工作面炮烟中毒事故的措施。     

Inactivation of Palladium‐based Oxygen Scavenger System by Volatile Sulfur Compounds Present in the Headspace of Packaged Food

An oxygen scavenger based on a catalytic system with palladium (CSP) was recently developed to remove oxygen in food packagings. Although the CSP worked with various types of food, with some foods, an inhibition of the CSP was observed. Because such catalytic systems are susceptible to poisoning by sulfur‐containing compounds, the aim of this study was to understand the inactivation of palladium‐based catalysts in presence of foods containing volatile sulfur compounds (VSCs). To achieve this, the oxygen scavenging activity (OSA) of the CSP was evaluated in presence of selected food products. Afterwards, VSCs mainly present in these foods were exposed to the CSP, and the influence on the OSA was evaluated. Finally, headspace analysis was performed with the diluted VSCs and with the packaged food products using proton transfer reaction time‐of‐flight mass spectrometry. It was found that the catalytic activity of the CSP was inhibited when VSCs were present in the headspace in concentrations ranging between 10.8–36.0 ppbv (dimethyl sulfide, DMS), 1.2–7.2 ppbv (dimethyl disulfide), 0.7–0.9 ppbv (dimethyl trisulfide), 2.1–5.8 ppbv (methional) and 4.6–24.5 ppbv (furfuryl thiol). It was concluded that in packaged roast beef and cheese, DMS may be the compound mainly responsible for the inactivation of the CSP. In packagings containing ham, the key compounds were hydrogen sulfide and methanethiol; in peanuts, it was methanethiol; and in par‐baked buns, an accumulation of methional, DMS, butanethiol and methionol. When potato chips were packaged, it was demonstrated that when VSCs are present in low concentrations, oxygen can still be scavenged at a reduced OSA.     

面向视觉分类模型的投毒攻击

数据投毒攻击中的后门攻击方式的攻击者通过将带有隐藏触发器的样本插入训练集中来操纵训练数据的分布,从而使测试样本错误分类以达到改变模型行为和降低模型性能的目的。而现有触发器的弊端是样本无关性,即无论采用什么触发模式,不同有毒样本都包含相同触发器。因此将图像隐写技术与深度卷积对抗网络（DCGAN）结合,提出一种基于样本的攻击方法来根据灰度共生矩阵生成图像纹理特征图,利用图像隐写技术将目标标签字符嵌入纹理特征图中作为触发器,并将带有触发器的纹理特征图和干净样本拼接成中毒样本,再通过DCGAN生成大量带有触发器的假图。在训练集样本中将原中毒样本以及DCGAN生成的假图混合起来,最终达到投毒者注入少量的中毒样本后,在拥有较高的攻击率同时,保证触发器的有效性、可持续性和隐藏性的效果。实验结果表明,该方法避免了样本无关性的弊端,并且模型精确度达到93.78%,在30%的中毒样本比例下,数据预处理、剪枝防御以及AUROR防御方法对攻击成功率的影响达到最小,攻击成功率可达到56%左右。     

面向分割学习的数据投毒防御方法设计与实现

分割学习作为一种新型的分布式学习方法,可能受到投毒攻击的严重威胁。在分割学习中,训练场景涉及模型分割后的多端协作训练,与传统联邦学习的终端独立训练后同步模型的攻击场景不同,如何设计有效的防御方法,避免恶意客户端的集群性的投毒攻击是一大挑战。针对上述挑战,本文聚焦在分割学习中客户端投毒攻击对中间特征的影响进行相关考察;提出并实现了一种综合检测防御方法——客户端随机分组策略,通过各组学习指定标签的样本的分组策略以避免恶意客户端的集群攻击;提出了基于DBSCAN聚类算法的中间特征检测算法,用于识别投毒攻击的恶意客户端;提出了基于信任度的防御机制,对信任度低的客户端的网络进行重新初始化,以减小恶意客户端对神经网络的持续影响。实验结果表明,该方法可以降低恶意客户端对模型的影响,尤其是在对中间特征产生较大影响的投毒的防御上效果较好,为分割学习领域的安全防护提供了一种新的思路和实践方案。