From ensemble electrochemistry to nanoparticle-impact electrochemistry: Altered reaction process and possible applications

Nanoparticle-impact electrochemistry (NIE) is an electroanalytical method based on the stochastic collisions of individual nanoparticles onto an inert ultramicroelectrode. In this article, we overview different characteristics of NIE-based reactions from their ensemble counterpart, that is, enhanced mass transport, intermittent working mode, and reduced reaction time scale. A particular interest is focused on the survey of the resulting changes in the reaction process regarding enhanced reaction efficiency and rate, altered selectivity, and improved catalyst stability. A summary of the application prospect of NIE is followed, and existing challenges are provided.     

Crisis curves in nonlinear business cycles

Intermittent behavior of economic dynamics is studied by a nonlinear model of business cycles when two of its control parameters, amplitude and frequency of a periodic exogenous driving force, are changed. This study points out how similar wanted situations may be reached by changing any of both parameters, and it gives a deeper understanding of what happens in actual economic data when some control parameters are changed at the same time.     

Research on the fault diagnosis technology of intermittent connection failure belonging to FPGA solder-joints in BGA package

A new method to detect intermittent faults in FPGA (field programmable gate array) of BGA (ball grid array) packages is presented. Inject proper current into measured IO port via sensor circuit, the intermittent faults will arouse impedance of the solder-joint to change intermittently, the voltage of solder-joint will also change intermittently, the fault information can be obtained through regulating the voltage signal. Compared with current monitoring method based on degradation model, this scheme is more reliable and accurate. It can prevent the catastrophic faults caused by failure of the FPGA solder-joints effectively, as well as economize the maintenance cost.     

尿中痕量碲测定的萃取-氢化物发生原子荧光光谱法

建立了萃取－断续流动氢化物发生原子荧光光谱法测定尿中碲的分析方法。研究了仪器工作条件和试剂对碲原子荧光强度的影响、最佳条件的选择、碲在二乙基二硫代氨基甲酸盐（ＤＤＴＣ）－ＣＣＬ４体系中的萃取行为及碲（Ⅳ）的还原;探讨了共存离子对碲测定的干扰及消除方法。方法检出限（３σ）Ｏ ０．２１ＵＧ／Ｌ,相对标准偏差为１．２４％,回收率为９２％～９９％。     

Scale-up of counter-current chromatography: Demonstration of predictable isocratic and quasi-continuous operating modes from the test tube to pilot/process scale

Predictable scale-up from test tube derived distribution ratios and analytical-scale sample loading optimisation is demonstrated using a model sample system of benzyl alcohol and p-cresol in a heptane:ethyl acetate:methanol:water phase system with the new 18 L Maxi counter-current chromatography centrifuge. The versatility of having a liquid stationary phase with its high loading capacity and flexible operating modes is demonstrated at two different scales by separating and concentrating target compounds using a mixture of caffeine, vanillin, naringenin and carvone using a quasi-continuous technique called intermittent counter-current extraction.     

双曲柄式160摄影机在战略靶场中的应用

文章叙述了靶场经纬仪中使用摄影机的类型与特点;指出更新的双曲柄式160摄影机具有技术性能高,操作方便,可靠性好等特点。经受了多种工作考验,为多种试验提供了高精度测量数据,最后给出了几种摄影机应用情况对照表。     

Active control of intermittent noise in a room

I.IntroductionThereverberantnoisesmaybereducedwithanactivenoisecontrol(ANC)systcmformedbyacornermicrophonc-amplifier-1oudspcakersystemina.oom.lllThismeth-odbascdonthenormalmodccancelingprincip1chasalreadybeenclarifiedbothinthco-ryandexperimcnts,andthclimitationandpotcntialityofitsapp1icationalsodiscussedinapreviouspaper.Thediscussionsinthepastlimitedmost1ytothesteadyconditionofnoiscfield,andthisisextendedtothetransientcondihoninthcprcsentwork,viz.thein-llucnceofthecornerANCsystemwhenthenois…     

Using the liquid nature of the stationary phase. VI. Theoretical study of multi-dual mode countercurrent chromatography

Countercurrent chromatography (CCC) is a separation technique using a biphasic liquid system and centrifugal forces to maintain a support-free liquid stationary phase. Either one of the two phases can be the liquid stationary phase. It is even possible to switch the phase role during the separation. The dual-mode method is revisited recalling its theoretical background. The multi-dual mode (MDM) CCC method was introduced to enhance the resolution power of a CCC column. The theoretical study of the MDM method is validated by modeling the separation of two solutes. The basic hypothesis is that the forward step (partial classical elution) is followed by a backward step that returns the less retained solute to the column head. The equations show that the most important parameter to maximize resolution is not the number of MDM steps but the total volume of liquid phases used to elute the solutes. The model is validated calculating correctly the peak position of previously published MDM experiments.     

Improved kinetics of ethanol oxidation on Pd catalysts supported on tungsten carbides/carbon nanotubes

Pd nanoparticles on tungsten carbides modified multiwalled carbon nanotubes (Pd-WC/MWCNT) catalysts have been prepared by an intermittent microwave heating (IMH) technique for the first time. The Pd-WC/MWCNT catalysts are evaluated and show an improved kinetics for the ethanol oxidation. It is recognized that the significant increase in the catalytic activity for ethanol oxidation on Pd-WC/MWCNT is attributed to both the synergistic effect between Pd nanoparticles and the WC support and the structure effect of the MWCNT. This type catalyst can be universally used as the oxygen reduction catalyst in fuel cells and sensors both in alkaline and acidic solutions.     

Determination of mercury by intermittent flow electrochemical cold vapor generation coupled to atomic fluorescence spectrometry

A novel method for determination of mercury was developed using an intermittent flow electrochemical cold vapor generation coupled to atomic fluorescence spectrometry (IF-ECVG-AFS). The mercury vapor was generated on the surface of glassy carbon cathode in the flow cell. The operating conditions for the electrochemical generation of mercury vapor were investigated in detail, and the interferences from various ions were evaluated. Under the optimized conditions, no evident memory effects of mercury were observed. The calibration curve was linear up to 5 μg L⁻¹ Hg at 0.54 A cm⁻². A detection limit of 1.2 ng L⁻¹ Hg and a relative standard deviation of 1.8% for 1 μg L⁻¹ Hg were obtained. The accuracy of method was verified by the determination of mercury in the certified reference human hair. The ECVG avoided the use of reductants, thereby greatly reducing the contamination sources. In addition, the manifold of IF-ECVG-AFS was simple and amenable to automation.