Preliminary Examination of A New Post-Column Photolysis-Molybdate Reaction Detection System for the Determination of Organophosphorus Compounds By High Performance Liquid Chromatography

Abstract

High-performance liquid chromatographic detection of UV-chromophore-deficient organophosphorus compounds has been aided by a new post-column photolysis-molybdate procedure. In the new procedure, a methanolic, acidified molybdate reagent is added to the eluent just prior to a photolysis chamber consisting of crocheted Teflon tubing wrapped around a mercury-discharge lamp. Organophosphorus compounds are photolyzed to orthophosphate, which in turn reacts with molybdate to form 12-molybdophosphoric acid (12-MPA). The 12-MPA is reduced photolytically to a molybdenum-blue species that absorbs at 735 nm. Because a photoinitiator (such as peroxydisulfate) is not needed, only one reagent pump is required. A limit of detection of about 10 ppb was indicated for a diphosphonate.     

Sampling Efficiency of the Tsi Aerodynamic Particle Sizer

Abstract

The Aerodynamic Particle Sizer (APS) has been tested and used in a variety of laboratory and field situations for indoor air quality research of both industrial and livestock buildings. The APS is capable of providing rapid, real-time measurement of particle size distribution. However, no literature was found in which the sampling efficiency of the APS was addressed. This paper presents a method to evaluate the sampling efficiency of the APS, considering both the aspiration efficiency and the penetration efficiency. Six tests were conducted and measurements were taken by a cascade impact sampler and the APS simultaneously. The results obtained by the APS were compared with the results of the cascade impact sampler.     

Analytic approach to analyzing the performance of membrane dehumidification by pervaporation

As life quality has been greatly improved recently, the importance of humidity control has increased. Various kinds of humidifiers and dehumidifiers have been developed and utilized widely in our daily lives and industrial processes. In this work, we focused on dehumidification facilitated by a pervaporation system that employs a nonporous membrane. The system mainly consists of two parallel chambers separated by the membrane and a vacuum pump that constantly drives moisture removal. The membrane-pump couple sets out a vapor concentration gradient across the membrane to permeate water vapors from the feed chamber of ambient wet air to the low-pressure permeate. The experiments were performed in a constant temperature and humidity chamber to supply the constant concentration of vapor to the feed chamber. We measured the outlet humidity and the water vapor transport rate, the mass of vapor permeated through the membrane, under various experimental conditions of different feed flow rates and feed chamber heights. As the flow rate increases, the outlet humidity is decreased, whereas the water vapor transport rate is increased. However, they are independent of the height in our experiment range. Combining the mass transport theory of the membrane and volume conservation of an infinitesimal control volume, we have established theories of the outlet humidity and the water vapor transport rate. The experimental data points are entirely consistent with our theory curves. Comparing the experimental results to the theories, we also have derived the membrane coefficient.

     

Control of Piezo Actuated Structures using Interval Method

Abstract

A Fast output sampling feedback controller is designed and implemented for vibration control of piezoelectric actuated beam structure using an interval method. Uncertainties which are assumed in the model, are identified through on line recursive least square parameter estimation. The control and identification process is done by using Simulink modeling software and a dSPACE DS 1104 controller board.     

Instrumentation to Study The Thermal Decomposition of Organic Compounds

ABSTRACT

Newly developed instrumentation allows the thermal decomposition of organic compounds to be studied by a technique known as Organic Particulate Analysis; the technique enables one to measure the temperature at which particulates are emitted from heated organic substances.

The new procedure has been applied to malonic acids, diazonium compounds and metal actylacetonates; particulate matter has been observed in the temperature range 85°-160°C for these organic compounds. No direct correlation of organoparticulation temperatures with literature melting points or decomposition temperatures has been found; in some instances the values are higher than literature values whereas in other instances, the values are much lower.     

An On-Stream Sampling Stirred-Flow Reaction Assembly

SUMMARY

During the course of kinetic studies in this laboratory, various designs of continuous-flow reactors have been advanced [1] in order to use the significant simplification of the rate equations, as derived by Harris [2], for a kinetic process. This communication reports the performance of a new assembly, recently designed in our laboratory, which combines on-stream sampling and modern chromatographic techniques with the principles of stirred flow, to attain the Harris conditions for the measurement of reaction rates.     

The Influence of Molecular Oxygen on Wear Protection by Surface-Active Compounds

Four-ball wear experiments were performed with zinc di-n-oc-tyldithiophosphate (ZDP), bis [N,N′-dihexyl(dithiocarbamato-s,s′)] nickel (II) (NiDTC) and tetraoctylthioperoxydiphosphate (TPDP) dissolved in a synthetic hydrocarbon base stock. The experiments were conducted both under air and under nitrogen atmospheres. The reactivities of these compounds towards peroxy radicals were evaluated by measuring the uptake of oxygen during peroxy radical titration experiments.

Atmospheric oxygen profoundly influenced metal wear protection by ZDP. This was reflected in the wear rate, wear asymmetry, production of soluble iron, and in the composition of the surface layers produced on the metal. Oxygen had little effect on results with TPDP. The NiDTC exhibited oxygen sensitivity intermediate to tile other additives. The influence of oxygen on the wear behavior of these compounds was paralleled by their relative reactivities toward peroxy radicals.

Ancillary experiments showed that the activation of ZDP as a highly effective antiwear agent cannot be unambiguously ascribed to peroxy radical reactions. An initial electron transfer step is suggested as an alternate working hypothesis to account for the experimental results.     

Computerized Circuit for the Precise Measurement of Rapid Temperature Changes

ABSTRACT

A computerized thermistor circuit is described which uses a pulsed technique for the measurement of rapid temperature changes. Tests are detailed which demonstrate the speed (5 kHz sampling rate), precision (±0.002 °K/sample), and utility of the instrument. Software outines for calibration of the circuit and for data acquisition are described briefly.     

Oscosurvismeter,A New Instrument for Osmotic Pressure,Conductance, Viscosity,and Surface Tension Measurements of Liquid Solutions of Chemical Substances

Abstract

The Oscosurvismeter is made of borosil glass material for measuring osmotic pressure (π), specific conductance (κ), viscosity (η), and surface tension (γ) of solutions. Solutions of different strengths are taken in two cells/compartments, partitioned by a semi‐permeable membrane (SPM). A concentration gradient makes the solvent move towards the concentrated solution to establish an equilibrium; this measures osmotic pressure (π). The Oscosurvismeter saves time and materials, and enhances accuracy and precision in measurements; the instrument consists of six parts: (1) survismeter; (2) osmometer; (3) electrode; (4) metallic clamp; (5) semipermeable membrane (SPM); and (6) high potential metallic springs. High accuracy data are noted with the instrument.     

Conformational dynamics of single molecules visualized in real time by scanning force microscopy: macromolecular mobility on a substrate surface in different vapours

We describe a technique to visualize and effect in real time motion and conformational transitions of single macromolecules. Two steps are involved. First, scanning force microscopy (SFM) was applied to detect in situ conformational transitions of single polymer molecules adsorbed on a substrate surface. Secondly, these changes were induced by controlled variations of environmental conditions in a microscope environmental chamber. In particular, we have revealed that exposure of a substrate with adsorbed macromolecules to vapours of different nature was able to increase molecular mobility and to stimulate conformational transitions of the polymer chains on the surface. Realization of SFM observation in a variable vapour environment was not as difficult as in liquid media. Variations of the vapour composition affected the oscillation dynamics of the cantilever with the scanning probe only to a small extent, and did not impede continuation of the scanning procedure. In fact, the characteristic times of the observed conformational changes were large enough (minutes to dozens of minutes) for sampling images repeatedly. Although recording of an SFM image was slow and required several minutes, we were able to visualize step‐by‐step the successive stages of the slow conformational transformation of the macromolecules adhering to the substrate, i.e. to investigate a molecular response to the environment changes in real time. Here, we studied the reversible collapse–decollapse transitions of cylindrical poly(methacrylate)‐graft‐poly(n‐butyl acrylate) brush‐like macromolecules exposed to different vapours. Single macromolecules on mica tended to assume a compacted globular conformation when exposed to the vapour of compounds, which due to their amphiphilic nature adsorb on mica and lower the surface energy of the substrate (e.g. alcohols). By contrast, the macromolecules adopted extended two‐dimensional worm‐like conformations in the vapours of compounds having high values of surface tension (such as water). In our opinion, the reason for the observed tendency was a competition in spreading on the substrate surface between the macromolecules and the co‐adsorbed vapour molecules. If the brush‐like macromolecules succeeded in the spreading, they acquired an extended conformation. Otherwise they collapsed to globuli in order to reduce the surface area per macromolecule. Thus, the enhanced mobility of synthetic macromolecules on a substrate observed in a vapour environment in combination with the possibility to manipulate the macromolecular conformation via changes in a vapour phase and the ability to visualize the transitions of the macromolecules individually, provides challenging prospects for SFM studies on the dynamics of single molecules under applied external stimuli.     

TRIBOLOGICAL ACTION AND OPTIMAL PERFORMANCE: RESEARCH ACTIVITIES REGARDING MQL MACHINING FLUIDS

ABSTRACT

As an optimal fluid for MQL machining, this paper introduces some synthetic polyol esters having the high biodegradability, excellent oxidation stability and satisfactory cutting performance. The fundamental investigation demonstrates synthetic esters possess the preferable adsorption ability on to the freshly cut metal surfaces and this ability can be enhanced by surrounding oxygen. This may result in effective lubricating film formation and is probably in close connection with their satisfactory MQL cutting performance. A multifunctional fluid, which is applicable to both machining and other lubricating parts of machine tools, is further developed based on the synthetic ester for MQL machining.     

Rapid Isothermal Gas Chromatography‐Mass Spectrometry Method for Validating a Small Ion Mobility Spectrometer Sensor

Abstract

A fast and reproducible isothermal gas chromatographic‐mass spectrometric method for validating a small ion mobility spectrometer (IMS) sensor for detection of gaseous volatile organic compounds (VOCs) is presented. This method utilizes an automated cyclic valving (CV) sampling technique coupled to a gas chromatograph‐mass spectrometer (GC/MS) in selected ion monitoring (SIM) mode (CV/GC/MS/SIM). The sampling time is considerably reduced by operating the GC isothermally at 300°C. This approach provides rapid measurements with 15 times more data points than the conventional GC/MS methods in which the column temperature is ramped, then cooled before the next sample can be injected. With the mass spectrometer operated in SIM mode, pre‐selected ions that represent the primary quantitation and secondary ions of toluene and a BTX (benzene, toluene, o‐, m‐, and p‐xylene) mixture were monitored and their corresponding breakthrough curves for flow through partially saturated soil columns were generated. The small variation in measured steady state mean concentrations (SSMC) from run to run demonstrates the reproducibility of this new method. A comparison of the transient concentration profiles of toluene from a BTX mixture and toluene alone obtained under identical test conditions shows a linear correlation with R²=0.997. This result suggests that the new method can be used to analyze and quantify some mixtures of co‐eluting gaseous analytes.     

Performance of a Dual Sample Introduction System with Conventional Concentric Nebulizers for Simultaneous Determination of Hydride and Non-Hydride Forming Elements by ICP-OES

Abstract

A dual sample introduction system that combines the benefits of nebulization and vapour generation in a single device is described. It consists of two commercial conventional concentric nebulizers coupled to a modified cyclonic chamber. The effect(s) of the solvent load produced by the amount of liquid carried for the system by the two nebulizer assemblies is investigated. Better sensitivities, similar precision and DL's (with the exception of hydride forming elements) were obtained compared with those obtained with the system working in single mode. Long term stability was less than 7% with the dual mode, being 2% and 6% for the non-hydride and hydride forming elements, respectively, in the single mode operation. DL's obtained are of the same order of magnitude as those reported by several authors, with the exception of Se whose conditions were in compromise with the optimal reached for the rest of the elements. Accuracy of the dual system was proved by analyzing NIST 1648, urban particulate matter, with satisfactory results.     

A Lab‐Built Hydride Generation Nebulizer for AAS

Abstract

A nebulizer for the hydride generation atomic‐absorption spectrophotometry of As and Se, and Hg vapor generation is described, in which the gas flow, the reductant, and the sample are connected separately through three concentric channels. The sample and the reducing agent flow separately till they reach the air flow. The generated species are then mixed with the air carrier gas and transported into the flame of an AA spectrometer. Optimization of flame type, acid, and reductant concentrations was carried out. Interference of transition metals on the analytes' signals was minimized using EDTA. Good linear analytical range and short term stability are obtained.     

Incompressible and Analytical Study on a Basic Model of a Complex Journal Gas Bearing

ABSTRACT

A basic analytical model of a hybrid journal gas bearing was set up completely for investigating the coupling between aerodynamics and aerostatics in a hybrid gas bearing under incompressible conditions, and for further improving its performance, under incompressible conditions. In this analytical model, the load-carrying capacity function is composed of five items. Apparently, there are pressure coupling and structure coupling between aerodynamics and aerostatics and when the groove distribution coefficient is 0.36, it is approximately maximum. However, this type of hybrid gas bearing structure can not be used when the pressure ratio is less than 1.

     

An experimental study on stability rating of impinging-jet injectors using air injection in a subscale chamber

Combustion instability rating is investigated experimentally in a subscale chamber with impinging-jet injectors. This study is focused on jet flow of both propellants of fuel and oxidizer without considering a chemical reaction. Air-injection tests using scaling techniques are proposed to predict acoustic instability in an actual full-scale combustion chamber of a rocket engine. In the present approach, a subscale chamber has been designed to have the same natural frequencies as those in a full-scale chamber, and air is injected into the subscale chamber instead of fuel and oxidizer and their flow rates are maintained. From the tests, damping factors are obtained as a function of a hydraulic parameter of jet flow. Based on the data, the instability map is drawn, where three acoustically unstable regions are presented. It is found that they coincide fundamentally with the results from hot-fire tests. Accordingly, as the first approximation, the proposed approach can be applied cost-effectively to the stability rating of jet injectors without losing essential features of acoustic instability when mixing of fuel and oxidizer jets is the dominant process in instability triggering.

     

The Lubricating Performance of an “in Situ” Process MoS2 Film in Air and in Liquids

The performance of a synthetic MoS₂ film, produced by electrodeposition of molybdic oxide followed by a temperature-pressure H₂S conversion to a molybdenum sulfide compound, is examined under extreme pressure conditions immersed in various fluids. Friction wear and EP characteristics, measured on various test machines, are compared to those of the fluids alone and also to conventional bonded films.

The fluids examined include: mineral oil, jet fuel, hydraulic fluid, silicone fluid.

The dry films include: burnished MoS₂ powder, MIL-L-8937 resin bonded film, MIL-L-8129 silicate bonded film and the synthetic “in situ” MoS₂ film.

The performance of the synthetic MoS₂ film on titanium and stainless steel is also examined.     

An experimental study on spray and combustion characteristics of LPG for application in direct-injection

As an alternative fuel that can be used in SI engines, LPG is a clean fuel with larger H/C ratio compared to gasoline, low CO₂ emission, and small amount of pollutants such as sulfur compounds. In the Spark-ignition (SI) engine, Direct injection (DI) technology can significantly increase the engine volumetric efficiency and decrease the need for a throttle valve. DI allows engine operation with the stratified charge, which enables a relatively higher combustion efficiency. Stratified charge can be supplied to nearby spark plugs to allow for overall lean combustion, which improves thermal efficiency and can cope with problems regarding emission regulations. In this study, a visualization experiment system that consists of visualization combustion chamber, air supply control system, emission control system, LPG fuel supply system, electronic control system and image data acquisition system was designed and manufactured. For all cases for which ignition was successful, flame propagation image was digitally recorded using ICCD camera, and the recorded flame propagation characteristics were examined. This study, in its results, is expected to make a contribution in terms of important data for the design and optimization of a Spark-ignited direct injection (SIDI) LPG engine.

     

Cryogenic drilling of aluminum-based printed circuit boards: a review and analysis

Abstract

An aluminum-based printed circuit board (Al-PCB) is a composite material comprising a copper layer, an insulating layer, and an aluminum base layer. In the drilling of Al-PCBs, exit burrs are formed because of the plastic deformation of the remnant aluminum under high drilling temperatures. In this work, a new method using cryogenic media is suggested to prevent exit burrs in Al-PCB drilling. The effects of cryogenic media, such as cold air, supercritical carbon dioxide solvent (scCO₂), and liquid nitrogen (LN₂), on the drilling temperature, chip removal, tool wear and exit burr formation were observed and analyzed. The Al-PCB drilling temperature could be effectively reduced when drilling with cold air, scCO₂ or LN₂. The chip removal and tool wear could be improved when drilling with cold air or LN₂. The exit burr formation when drilling with scCO₂ or LN₂ was greater than that when drilling under cooling and cold air conditions. A cold air matching composite wood backup board (MW-0.5) could effectively control the exit burr formation within 20?μm. This is the first study on the effects of three different cryogenic media on PCB drilling and is expected to provide a good reference for the cryogenic drilling of PCBs.     

A setup for studying the characteristics of 218Po transfer in air

An experimental setup and a technique for studying the characteristics of ²¹⁸Po transfer in air is described. The experimental technique is based on detecting α decays of ²¹⁸Po atoms that precipitate by diffusion on the surface of a semiconductor detector from a closed volume filled with air with an admixture of ²²²Rn. It is shown that, under conditions of electrostatic precipitation inside a radiometer chamber, a fraction of ²¹⁸Po atoms attach to coarse particles for which sedimentation may play an important role. The rates of attachment of free 218Po atoms to aerosols are obtained.