An in situ set up for the detection of CO2 from catalytic CO oxidation by using planar laser-induced fluorescence

We report the first experiment carried out on an in situ setup, which allows for detection of CO(2) from catalytic CO oxidation close to a model catalyst under realistic reaction conditions by the means of planar laser-induced fluorescence (PLIF) in the mid-infrared spectral range. The onset of the catalytic reaction as a function of temperature was followed by PLIF in a steady state flow reactor. After taking into account the self-absorption of CO(2), a good agreement between the detected CO(2) fluorescence signal and the CO(2) mass spectrometry signal was shown. The observed difference to previously measured onset temperatures for the catalytic ignition is discussed and the potential impact of IR-PLIF as a detection technique in catalysis is outlined.     

Cavity ring-down spectroscopy with an automated control feedback system for investigating nitrate radical surface chemistry reactions

Nitrate radical (NO(3) (●)) surface chemistry of indoor environments has not been well studied due to the difficulty in generating and maintaining NO(3) (●) at low concentrations for long term exposures. This article presents the Surface Chemistry Reactant Air Delivery and Experiment System (SCRADES), a novel feedback controlled system developed to deliver nitrate radicals at specified concentrations (50-500 ppt, ±30 ppt) and flow rates (500-2000 ml min(-1)) to a variety of indoor surfaces to initiate reaction chemistry for periods of up to 72 h. The system uses a cavity ring-down spectrometer (CRDS), with a detection limit of 1.7 ppt, to measure the concentration of NO(3) (●) supplied to a 24 l experiment chamber. Nitrate radicals are introduced via thermal decomposition of N(2)O(5) and diluted with clean dry air until the desired concentration is achieved. Additionally, this article addresses details concerning NO(3) (●) loss through the system, consistency of the NO(3) (●) concentration delivered, and stability of the CRDS cavity over long exposure durations (72 h).     

纯铜表面渗铝-内氧化磨损性能研究

为了提高纯铜表面的耐磨性,利用纯铜渗铝-内氧化工艺制备了A12O3/Cu表面复合层,分析了表层的组织结构,测试了显微硬度,并进行了黏着磨损、固定磨料磨损试验。结果表明：利用纯铜渗铝-内氧化工艺能够获得弥散分布的A12O3/Cu表面复合层,其表层显微硬度、耐磨性较纯铜有较大的提高,渗铝量增大,渗铝-内氧化试样的显微硬度、耐磨性也相应提高,但不是线性关系。     

An LIF characterization of supersonic BO (X2Σ+) and CN (X2Σ+) radical sources for crossed beam studies

Various ablation sources generating supersonic boron monoxide (BO; X(2)Σ(+)) radical beams utilizing oxygen (O(2)), carbon dioxide (CO(2)), methanol (CH(3)OH), and water (H(2)O) as seeding gases were characterized in a crossed molecular beams setup by mass resolved time-of-flight spectroscopy and spectroscopically via laser induced fluorescence. Intensities of the sources as well as rovibrational energy distributions were analyzed. The molecular oxygen source was found to produce excessive amount of an unwanted BO(2) byproduct. Internal vibrational energy of boron monoxide generated in the water and methanol sources was too high to be considered for the study of dynamics of ground state radicals. The best combination of intensity, purity, and low internal energy was found in the carbon dioxide source to generate boron monoxide. We successfully tested the boron monoxide (BO; X(2)Σ(+)) radical beam source in crossed beams reactions with acetylene (C(2)H(2)) and ethylene (C(2)H(4)). The source was also compared with supersonic beams of the isoelectronic cyano (CN; X(2)Σ(+)) radical.     

罗丹明6G-Co^2＋ -KI-H2O2光度法测定抗氧化剂清除羟自由基的能力

建立了一种基于罗丹明6G（Rh6G）-Co^2＋ -KI-H2O2反应体系的检测抗氧化剂清除羟自由基能力的光度分析新方法。在HAc-NaAc缓冲溶液中，Co^2＋与H2O2反应，产生的羟自由基与过量的KI反应，生成的L与Rh6G络合，使体系的吸光度值降低，根据△A527，值的变化可间接测得羟自由基的生成量。抗氧化剂的加入可抑制吸光度值降低，从而间接测定其清除羟自由基的能力。考察了抗坏血酸、硫脲、没食子酸等几种常见抗氧化剂清除羟自由基的能力，结果为：没食子酸〉硫脲〉抗坏血酸。比较了Mn^2＋，Co^2＋，Fe^2＋离子与H2O2反应时羟自由基的产生量。测定了几种蔬菜和水果的羟自由基清除能力，结果表明，苹果和芹菜具有较高的羟自由基清除效率。     

The influence of oxidation on the tribological performance of diester lubricant

The oxidative degradation test of di‐2‐ethylhexyl sebacate (DEHS) was carried out by a sealed stainless steel reactor. Fourier transform infrared spectroscopy and gas chromatography–mass spectrometry (GC–MS) were utilised to characterise the chemical composition and molecular structure of the oxidation products. The results revealed that 2‐ethyl‐1‐hexanol and mono(2‐ethylhexyl)sebacate were major degradation products in the liquid phase. Tribological behaviour was measured using a four‐ball tester. Scanning electron microscopy was employed to investigate the morphologies of the worn surface. Tribological results showed that anti‐wear and friction‐reducing performances of DEHS were highly dependent on the chemical composition of the oxidation products generated during the test. The hydroperoxides formed during the initial oxidation process could deteriorate lubrication properties of DEHS. However, certain amount of highly polar degradation products (acids and alcohols) generated could significantly improve the friction‐reducing performance of DEHS by the formation of boundary adsorption films on the rubbing surfaces. Copyright © 2013 John Wiley & Sons, Ltd.     

Flow pattern and hydraulic performance of the REDAC Gross Pollutant Trap

This paper discusses the flow pattern and hydraulic performance of a Gross Pollutant Trap (GPT), designed and patented by River Engineering and Drainage Research Centre (REDAC) at Universiti Sains Malaysia. Stormwater problems have become more severe due to the increase in urbanization. The increase in the amount of impervious surface in urban areas produces more stormwater runoff, that is carried to the receiving bodies of water. The higher runoff volume also carries more pollutants (gross pollutants, sediments, and nutrients) from the contributing catchment area. Coarse sediments transported by stormwater runoff have negative effects on the receiving body of water and the aquatic environment by covering up aquatic habitats and clogging waterways. One of the challenges in designing a GPT for urban stormwater drainage is providing effective trapping without hindering the hydraulic function of the channel, thus, avoiding overspill or flooding. The current study presents a GPT design to meet these specific requirements of trapping efficiency and hydraulic function. The current GPT overcame the common problem of overspilling of gross pollutants in GPT by the introduction of additional overspill compartments that can handle excessive runoff and improve pollutant trapping in higher flow conditions. In laboratory testing, the prototype GPT was capable of achieving good trapping efficiency (over 80% for gross pollutants and over 60% for coarse sediments) without causing any overspill.     

INFLUENCE OF MACHINING PARAMETERS ON THE WHITE LAYER FORMATION PROCESS AND ITS CHARACTERISTICS IN TURNING OF HARDENED STEEL

This article contains results of experimental research activities of white layer formation (WLF) and its characteristics during a process of turning hardened steels (THS), which have been carried out in laboratories of DD Cimos TMD Ai Grada?ac. WLF. Characteristics during the THS process were analyzed from the aspects of influence caused by machining parameters as well as tool flank wear width. Experimental tests of tool wear have been performed. The tool used in experimental tool wear was ceramic cutting insert CNGA 120408T, catalogue mark IN22 Al2O3-TiCN. In accordance with achieved results, value of tool flank wear 220 µm has been set as the criterion of wear. In accordance with defined wear criterion, determination of level and type of influence that machining parameters have on WLF and its characteristics were carried out in accordance with planned experimental methodology. Experiments have shown that cutting speed and tool flank wear width (for all other machining conditions unchanged) can be used for control of WLF and its characteristics. Structural changes in surface layer of the working piece, during the cutting process of hardened material, except for the WLF are also presented through a transition zone, e.g., dark layer, which has lower hardness than the initial material. Hard WL can take over a protection role for a machined surface from abrasive actions, while softened zone (dark layer) can take over a function of WL solder with the initial material. Analysis of achieved results points to a possibility of controlling the WLF and its characteristics, and therefore a possibility of using WL in a positive context. The basis for the above mentioned is the effect of additional plastic deformation of WL (APDWL), which occurs only under certain machining conditions. The effect seen, if follows WLF, results in decrease of machined surface roughness compared to its expected value. Accordingly there is a possibility for identification of WL on a machined surface by measuring the roughness parameters without previous metallographic preparation of samples.     

草地蝗虫吸捕机吹吸式吸嘴的设计

针对原草地蝗虫吸捕机采用直吸式吸嘴，吸捕率低。以度蝗虫在吸嘴内壁上撞击、破碎等问题，在对原直吸式吸嘴，特别是在对吹吸气流进行理论分析的基础上，结合蝗虫在吸捕时的跳跃躲避特性以度对蝗虫悬浮速度的实验测定，设计了吹吸式吸嘴，并对吹吸式吸嘴与直吸式吸嘴进行了对比试验。试验表明：（1）吹吸式吸嘴可将吸口气流速度从原来直吸的20m／s降低为现在的14m／s，可减轻后续设备的负荷。（2）与具有相同吸口气流速度的直吸式吸嘴相比，其轴向、径向吸捕距离分别延长到115～2倍。负压吸捕区增大到2～3倍，能够对更大范围内的蝗虫进行有效吸捕，提高吸捕率。（3）获得了影响回旋气幕形成各主要因素的合理参数，为草地蝗虫吸捕机的设计与改进提供了理论依据。     

Structural characteristics and mechanism of action of antioxidant anticorrosive additives for perfluoropolyalkylether fluids

The combination energies of perfluoropolyalkyletherphenylamide (PFPEA) with perfluoropolyalkylether oxygen radicals (R_fO) and with Fe atoms have been calculated by quantum chemical methods. The values are ‐417.33 and ‐105.02 kJ/mol, respectively. The structural characteristics and the mechanism of action of an antioxidant anticorrosive additive have been explored. It was found that the highest occupied molecular orbital (HOMO) of the additive is a π molecular orbital and it has the properties of a typical electron donor. The HOMO of the PFPEA additive reacts with the lowest unoccupied molecular orbital (LUMO) of an Fe atom and forms a coordinate bond and chemically adsorbed film on the metal surface. The film inhibits catalytic degradation and protects the metal surface. The additive is also capable of accepting the electron of R_fO. The R_fO radical combines automatically with the C₇ atom of the benzene ring to terminate the R_fO decomposition reaction. The PFPEA additive has been synthesized and analysed by UV and IR. Measurement of antioxidant anticorrosive properties indicates that, in the presence of the synthesised additive, the weight loss of a perfluoropolyether lubricant is reduced by about 7 times and the degradation temperature is increased by about 19°C compared with the base oil without the additive. The experimental results are consistent with the conclusions from the theoretical study.     

A comparative study of adaptation algorithms for nonlinear system identification based on second order Volterra and bilinear polynomial filters

Nonlinear filtering techniques have recently become very popular in the field of signal processing. In this study we have considered the modeling of nonlinear systems using adaptive nonlinear Volterra filters and bilinear polynomial filters. The performance evaluation of these nonlinear filter models for the problem of nonlinear system identification has been carried out for several random input excitations and for measurement noise corrupted output signals. The coefficients of the two candidate filter models for are designed using several well known adaptive algorithms, such as least mean squares (LMS), recursive least squares (RLS), least mean p-norm (LMP), normalized LMP (NLMP), least mean absolute deviation (LMAD) and normalized LMAD (NLMAD) algorithms. Detailed simulation studies have been carried out for comparative analysis of Volterra model and bilinear polynomial filter, using these candidate adaptation algorithms, for system identification tasks and the superior solutions are determined.     

添加剂对电诱导GaN晶片化学机械抛光的影响

为研究添加剂对氮化镓(GaN)晶片化学机械抛光(CMP)材料去除率的影响,采用直流电源对n型GaN晶片进行电化学刻蚀,利用X射线光电子能谱(XPS)和原子力显微镜(AFM)研究电诱导辅助下GaN晶片CMP过程中,对苯二甲酸(PTA)和H 2O 2对其材料去除的影响。结果表明:在添加电流的条件下,随着H 2O 2体积分数增大,GaN材料去除率先升高后降低;随着PTA浓度的增加,GaN材料去除率先增加后减少;在H 2O 2体积分数为4%,PTA浓度为10 mmol/L条件下,GaN晶片的化学机械抛光材料去除率最高,为693.77 nm/h,抛光后GaN晶片表面粗糙度为0.674 nm;通过XPS分析,电诱导后GaN晶片表面的Ga 2O 3含量增加,表明电流作用促进了GaN材料表面的氧化腐蚀作用,进而提高了其CMP材料去除速率。     

基于SVR的非线性系统故障诊断研究

针对非线性系统辨识建模和故障诊断难的问题,利用回归型支持向量机(support vector regression,SVR)分别设计了非线性系统的辨识建模系统和故障诊断系统,最后以某一非线性系统为例进行了仿真试验研究,建立了该非线性系统的SVR辨识模型,在此基础上进行了三种典型故障的诊断试验,仿真试验结果验证了该方法的有效性和先进性。     

KSNP+ reactor vessel head drop analysis for a 5.5M free fall

The KSNP⁺ RV closure head drop analysis was carried out to assess the reactor core coolability in case of the RV closure head drop accident during the refueling operation. The analysis consists of a number of different RV head drop scenarios as the postulated accident events during refueling that include a concentric head drop case and three different cases of laterally offset head drop cases. The analysis was initiated due to the adoption of the IHA (Integrated Head Assembly) in the KSNP⁺ reactor design, which increases the weight of the RV closure head assembly. Four different analysis models were developed that correspond to the RV head drop analysis scenarios. An in-house dynamic analysis code was used for the RV head drop analysis. The entire reactor internals and fuel assemblies are modeled by using lumped masses and spring elements. Because of the extreme load exerted by RV head drop, most members experience stresses that are beyond the elastic limits. A separate elastic—plastic analysis for some members was carried out and the resulting load-deflection curve was used as the stiffness of the element. The effect of water above the reactor vessel in the refueling pool was ignored for the conservative estimation of the analysis. The analysis shows that the concentric head drop is the most severe case of loading condition. It also reveals that the local deformation of some reactor internals and the fuel assemblies is occurred; however the primary membrane stresses are within the bound of allowable stress limits. Consequently the reactor core remains in coolable state.     

A Semi-Automatic Batch Reactor for the Study of Vegetable Oil Hydrogenation

Abstract

A semi-automatic installation is described for carrying out studies related to the characterization of hydrogenation catalysts, mechanisms, and reactions. It consists of the installation of a reactor vessel for liquid substrates (having a capacity of up to 3 dm³), with an emulsifying mechanical agitator whose movement is transmitted by means of a magnetic coupler. Thermal handling and control is carried out by means of a solid aluminum thermostatic oven. With independent internal controlled heating, it is possible to determine caloric capacity. The instrument is shown, as are the results obtained from follow-up of soybean oil hydrogenation using a commercial Ni-SiO₂ catalyst. Aspects related to the hydrogenation reaction mechanism are shown and a simple and rapid method to obtain kinetic data from this reaction is suggested.     

Quantitative analysis of transient surface reactions on planar catalyst with time-resolved time-of-flight mass spectrometry

A procedure for the quantitative analysis of transient surface catalytic reactions in millisecond time resolution has been studied constructing a specially designed apparatus employing (1) pulsed-gas valves for the injection of reactant molecules onto catalysts and (2) a time-of-flight mass spectrometer (TOF-MS) to detect every reaction product simultaneously. For a better understanding of the catalytic activity and selectivity for products quantitatively, a procedure for measuring an amount of reactant molecules injected onto catalyst surface and calibrating the intensity of mass signal were proposed and implemented. We tested the applicability of this procedure for the quantitative analysis of products of NO+H(2) reaction on Pt-Al(2)O(3) catalysts (a planar catalyst: Pt-Al(2)O(3)Si substrates inserted into a micro-tube-reactor with SiC balls). Although the surface area of the planar catalyst was very small, the mass signal intensities of the reaction products were found to be sufficient for the above procedure. We measured the fragmentation patterns and the inherent sensitivity factors in the TOF-MS using the mixture of the internal standard gas Ar and the N-containing gases. The relative sensitivity factors for NH(3), N(2), NO, and N(2)O and the relative intensities of fragment peaks to the molecular ion peak of H(2)O and N(2)O were estimated. The procedure constructed here has enabled us to analyze the transient consecutive secondary catalytic reactions as well as primary reactions based on the formation rate of product molecules per millisecond instead of the mass signal intensities of the reaction products.     

Study of high-efficiency electrical discharge machining-induced ablation machining of titanium alloy TC4 using a multi-function electrode

Aimed at overcoming the low efficiency of electrical discharge machining (EDM), and taking advantage of the characteristic that most metals can burn in oxygen, a new high-efficiency process is put forward: EDM-induced ablation machining (EDM-IAM) using multi-function electrode technology. EDM-IAM injects oxygen and dielectric fluid into the processing area through a dedicated channel of a multi-function electrode. The chemical energy caused by the reaction of metal and oxygen can much improve the material removal efficiency. To study the factors affecting the efficiency of the process, the ablation machining of a titanium alloy (TC4) using a multi-function electrode was carried out; analysis of the worked surface was done with scanning electron microscopy, X-ray diffraction, and discharge waveforms. The results show that the substances of the worked surface are mainly TiO, TiO_1.2, TiO₂, and smaller amounts of Ti₃O and other titanium oxides. Violent oxidation combustion reaction occurs during the ablation machining process. The processing efficiency of ablation machining can reach 347.7 mm³/min, which is 58.7 times that of normal EDM for the same processing conditions. The main reasons for the high material removal rate are the higher utilization rate of electric spark discharge energy, consumption of material by ablation, melting effect of combustion heat on the workpiece material, and forced chip removal effect by local explosion.     

Creep behavior of Alloy 617 in high temperature air and helium environments–effect of oxidation damage

The creep behavior of a nickel-base superalloy, Alloy 617, which is considered as a candidate material for the very high temperature gas cooled reactor, was studied. Creep rupture tests were carried out at 800°C, 900°C and 1000°C in static and flowing helium environments as well as in air. Creep rupture life in static helium was longer than that in air, while it was shorter in flowing helium environments. Microstructure observation of the creep tested specimens showed that the shorter creep rupture life in flowing helium was associated with the thicker oxide layer, greater decarburization depth, and deeper internal oxidation happened during the creep tests. The degree of such oxidation damage was quantified for the creep tested specimens and correlated with the creep rupture life in different environments.     

反应堆压力容器金属O形环密封性能研究

采用MSC .Marc软件 ,对反应堆压力容器双道金属O形密封环进行弹塑性大应变接触分析 ,给出在不同压紧量下的回弹量 ,并与试验结果进行比较。     

异种陶瓷材料微波连接的研究

采用微波加热方法与常规加热方法对ＺｒＯ２增韧Ａｌ２Ｏ３（ＺＴＡ）、Ｙ２Ｏ３稳定的四方相ＺｒＯ２（Ｙ－ＴＺＰ）进行连接试验,结果表明,利用微波加热可以顺利实现异种陶瓷之间的连接。与常规方法相比,微波加热可以快速完成连接过程,被连接陶瓷材料之间界面的结合状态良好,连接强度更高。