An air to water bridge: air sampling and analysis using tetraglyme

A water-soluble organic liquid is shown to scrub a wide variety of volatile organic compounds from air and gas streams. Gas pulled through impingers containing chilled tetraglyme (an organic solvent utilized in USEPA methods 3050A and 8240) is found to efficiently trap volatile Priority Pollutant, Hazardous Substance List and other organic species. A portion of the tetraglyme is subsequently dispersed into water and analyzed using conventional water analysis methodology. Practical quantitation limits of 100 ppbv have been demonstrated, and a potential to achieve lower limits of detection is clear. The method offers advantages over canister, adsorption tube, or Tedlar bag air-sampling techniques. Attributes include broad applicability, preservation of sample integrity ("plating out" of analytes is eliminated), freedom from water vapor interference, ready inclusion into water analysis methodology, simplicity, and low cost. Environmental laboratories with ordinary water/volatile organic analysis equipment are enabled to perform air-monitoring analyses without specialized hardware or expertise.     

Circulating particle flow and air bubble behavior at various superficial air velocities in two-dimensional gas–solid fluidized beds

Circulating particle flow and behavior of air bubbles in a two-dimensional gas-solid fluidized bed of various superficial air velocities are investigated by recording videos of movement of a plastic pellet put into the fluidized bed and rising air bubbles using a video camera. The movement velocity of the plastic pellet and properties of the air bubbles such as the bubble rising velocity and the bubble distribution coefficient, which shows the proportion of the bubbles erupting at the center of the bed surface, are measured by analyzing the videos. It is found that the plastic pellet moves following the circulating particle flow; the particles rise up at the center of a column and fall down near the side walls, and that the movement velocity increases with the superficial air velocity. The bubble rising velocity, the apparent erupting bubble size and the bubble distribution coefficient increase, and the bubble eruption frequency slightly decreases, with the superficial air velocity. These results indicate that the circulating particle flow is generated by the rising air bubbles. In particular, the fact that the air bubbles rise at the center of the column and coalesce with other bubbles is closely related to the generation of the circulating particle flow.     

全固态Li-O_2(air)电池研究进展

锂空气电池[Li-O_2(air)]具有极高的能量密度,引起了越来越多的关注。全固态Li-O_2(air)电池使用不易燃的无机固体锂离子导体材料作为电池电解质,大大提高了电池的安全性能。研发具有高离子电导率、高稳定性的固体电解质对全固态Li-O_2(air)电池的发展起到极大的推动作用。此外,研发高性能正极催化剂、采取合理的技术手段提高电极/固体电解质界面性能也是全固态Li-O_2(air)电池面临的挑战。分别从正极、负极、固体电解质以及电极/电解质界面等方面对全固态Li-O_2(air)电池进行综述。     

STUDEROn—air3000数字调音台在音频网络系统中的应用

介绍STUDER On-air3000数字调音台组建的音频网络传输方案中包含的MADI技术、On-air3000的基本构成,探讨On-air3000引入以太网技术的独立式系统应用,以及在音频网络系统中的应用。     

Macromolecule analysis based on electrophoretic mobility in air: globular proteins

Globular proteins ranging in molecular mass from 5.7 to 669 kDa were separated and analyzed using an aerosol technique based on the electrophoretic mobility of singly-charged molecular ions in air. The ions were produced by electrospraying and drying 100-nm-diameter droplets of a liquid suspension of the proteins, using ionized air to remove the droplet charge due to the spray process. The electrophoretic mobility was measured using a modified commercial continuous-flow differential mobility analyzer operated near atmospheric pressure. An unmodified commercial condensation particle counter was used for detection. The concentrations analyzed ranged from 0.02 to 200 μg of protein/mL of buffer, with a liquid sample flow rate of approximately 50 nL/min. Sampling time of 3 min was used for each complete distribution measured. The electrophoretic mobilities measured were determined entirely from air flow rates, apparatus geometry, and applied potentials. Results were expressed as electrophoretic mobility equivalent diameters using a Millikan formula.     

Spectral characteristics of optical discharge in a high-speed methane–air jet

Results of gasdynamic and spectroscopic investigations of optical discharge in the subsupersonic flow of a homogeneous fuel–air (CH₄ + air) mixtures are presented. The combustion was initiated and maintained by optical discharge created using a CO₂ laser. The laser radiation propagated across the flow and was focused by a lens on the axis of the supersonic jet (M = 2). Emission-spectroscopy techniques provided data on the composition of radiating combustion products and the intensity of components emitted in the region of optical discharge. Patterns of Toepler’s visualization of the flow structure in the schlieren scheme are presented. The images were monitored by a high-speed video camera operating at an exposure time of 1.5 μs and a frame frequency of 1000 s^–1.     

Ni–Cu alloy for diffusion bonding cermet/steel in air

Microstructural and mechanical evaluation for joints obtained by static and dynamic diffusion bonding of a 90MnCrV8 high strength steel coated with WC–Co, using a Ni–Cu alloy as interlayer, are shown in the present work. In all joints different reacted zones generated during the bonding process can be distinguished by means of scanning electron microscopy and dispersive X-ray spectrometry. The maximum tensile strength obtained using dynamic diffusion bonding process confirms a very promising technology for industrial applications.     

Super-high interlayer spacing of graphite oxide obtained by γ-ray irradiation in air

We produced a type of graphite oxide with the interlayer spacing of 2.09 nm by treating conventional graphite oxide with γ-rays at an absorbed dose of 200 kGy in air. The expansion of interlayer distance should be attributed to the increased amounts of topological defects and then the improved steric hindrance between interlayers. Due to the decomposition of water molecules in graphite oxide by γ-rays, the reductive species were produced so that graphite oxide was partially reduced. It is also speculated to be the main mechanisms for alteration of oxygen groups. The change of carbon chain structures and oxygen groups were further supported by X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. This simple and effective method of making graphite oxide with d-spacing of 2.09 nm by irradiating it in air is of interest not only for its easier intercalation and exfoliation than pristine one, but also for its potential to prepare graphene sheets with high percent of monolayers.     

Monolayer studies of sugar- and nucleoside-terminated dendrimers at the air–water interface

Sugar- and adenosine-terminated dendrimers, [1,2-o-Isopropylideneribosyl-(G₁-12acid), -(G₂-36acid)] and [Adenosyl-(G₁-12acid), -(G₂-36acid)], were synthesized using Newkome's dendrimer synthetic method. Langmuir and Langmuir–Blodgett (LB) monolayers of these dendrimers have been constructed and characterized at the air–water interface and on solid substrates by measuring surface pressure–molecular area (Π–A) isotherms, atomic force microscopy (AFM), ellipsometry and contact angle measurement. Π–A isotherms and AFM images showed that these dendrimers formed stable and homogeneous monolayers without aggregation on pure water surface. The first and second generation of sugar-terminated dendrimers show molecular areas of 647 and 1359 Ų, respectively. Ellipsometry measurement indicates that the thickness of both the first and the second generation of sugar-terminated dendrimers were about 10 Å. This reflects a flat orientation of both molecules at the air–water interface. On the other hand, the first generation of adenosine-terminated dendrimer shows an area of 105.6 Ų per molecule with a thickness of 16 Å, and for the second generation, the area was 738.4 Ų with a thickness of 27 Å. These results suggested that adenosine-terminated dendrimers maintain a spherical form at the air–water interface. It was found that small difference in the structure of thymine and uracil in the subphase critically affects the interaction of the molecules and conformation of the dendrimers at the interface.     

Human islet amyloid polypeptide at the air–aqueous interface: a Langmuir monolayer approach

Human islet amyloid polypeptide (hIAPP) is the source of the major component of the amyloid deposits found in the islets of Langerhans of around 95 per cent type 2 diabetic patients. The formation of aggregates and mature fibrils is thought to be responsible for the dysfunction and death of the insulin-producing pancreatic β-cells. Investigation on the conformation, orientation and self-assembly of the hIAPP at time zero could be beneficial for our understanding of its stability and aggregation process. To obtain these insights, the hIAPP at time zero was studied at the air–aqueous interface using the Langmuir monolayer technique. The properties of the hIAPP Langmuir monolayer at the air–aqueous interface on a NaCl subphase with pH 2.0, 5.6 and 9.0 were examined by surface pressure- and potential-area isotherms, UV–Vis absorption, fluorescence spectroscopy and Brewster angle microscopy. The conformational and orientational changes of the hIAPP Langmuir monolayer under different surface pressures were characterized by p-polarized infrared-reflection absorption spectroscopy, and the results did not show any prominent changes of conformation or orientation. The predominant secondary structure of the hIAPP at the air–aqueous interface was α-helix conformation, with a parallel orientation to the interface during compression. These results showed that the hIAPP Langmuir monolayer at the air–aqueous interface was stable, and no aggregate or domain of the hIAPP at the air–aqueous interface was observed during the time of experiments.     

Red@Black phosphorus core–shell heterostructure with superior air stability for high-rate and durable sodium-ion battery

Heterostructured electrodes have gained increasing attentions owing to the synergistic effects from individual building components and the unique interfaces. However, rational design and controllable fabrication of high areal capacity and durable phosphorus-based heterostructure anode for industry remains a critical challenge. Herein, a new red@black phosphorus core–shell heterostructure anchored on three-dimensional N-doped graphene (RP@BP/3DNG) has been prepared via a facile one-step solvothermal strategy. As demonstrated by experimental data and theoretical calculations, RP@BP/3DNG shows a superior high electronic conductivity and an extremely low Na⁺ diffusion barrier due to the build-in filed at the RP@BP heterointerface, thus RP@BP/3DNG delivers an ultra-high areal capacity of 3.46 mAh cm⁻² (1440.2 mAh/g at 0.05 A/g), impressive rate performance (521.3 mAh/g at 10.0 A/g) as well as unprecedented capacity retention rate of 89.3% after 1200 cycles at 10.0 A/g when evaluated as an anode for sodium ion batteries (SIBs). Furthermore, the internal electric field at the interfaces of RP@BP leads to the shift of electron cloud from BP to RP, which greatly suppresses the reaction activity of lone-pair electrons of BP atoms, and therefore RP@BP/3DNG shows much enhanced air stability. This work heralds a new insight for designing high-performance and stable P-based anodes for rechargeable batteries.     

Orthorhombic CoSe2 nanoparticles anchored in Ketjenblack as a bifunctional electrocatalyst for Zn‐air batteries

Avoiding agglomeration of nanoparticles and regulating the electronic properties are highly essential methods to improve the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of catalysts and enhance the cycle stability of rechargeable metal-air batteries. Herein, orthorhombic CoSe₂ nanoparticles anchored in acid-treated Ketjenblack (o-CoSe₂/AK) nanoparticles have been synthesized via a hydrothermal reaction and selenization treatment, and exhibit excellent ORR and OER performance (a half-wave potential of 0.84 V for ORR and an overpotential of 380 mV at 10 mA cm^?2 for OER). As a catalyst for a rechargeable Zn-air battery, it possesses a largest powder density of 122.0 mW cm^?2. Surprisingly, o-CoSe₂/AK has demonstrated outstanding stability and durability, especially superior to noble metals. The excellent bifunctional electrocatalytic performance is mainly ascribed to a large specific surface area, and metallic o-CoSe₂ nanoparticles with a high dispersion anchored in the AK substrate surface, regulating the electronic structure.

     

Characterization of lubricating oil effects on the performance of reciprocating compressors in air–water heat pumps

Lubricating oils play several key roles in compressors, such as lubrication of the parts exposed to friction, prevention of gas leakage at the compression chamber, and cooling of the pieces heated by friction. Oil viscosity and possibility of mixing with refrigerant are the significant factors that should be considered in choosing compatible lubricants. Generally, high viscosity lubricants reduce the efficiency and lubricants with low viscosity cause to direct contact between the metal parts in the compressor. In this study, an experimental procedure has been carried out to investigate the influences of oil circulation in the compressor working with R-404a refrigerant. Although this study has been devoted to a detailed attempt to identify the effects of oil viscosity on energy consumption, an innovative way to analyze this critical parameter has been carried out in parallel with other parameters including refrigerant charge amount, condenser water flow rate and air temperature in the evaporator. The sample oils selected for experiments are SL22, SL68 and SL220. The basic nature of the lubricants and their mixtures with refrigerant, COP value, compressor efficiency and exergetic efficiency of the system has been analyzed under different working conditions.     

Cooling mechanism of a solar assisted air conditioner: An investigation based on pressure–enthalpy chart

This paper reports a theoretical study of a conventional vapor compression air conditioner combined with a solar energy source. This system comprises two parts: the cooling mechanism and the solar heat source to operate it. Only the cooling machine part will be considered here, in which the refrigerant temperature leaving the immersed coil inside the storage tank can be calculated directly from the pressure–enthalpy diagram of the operating refrigerant. The investigation has been made using a new low global warming potential refrigerant that belongs to HFO family as an alternative to two high global warming potential refrigerants that belong to HFC family. These are R-1234ze(E) as an alternative to R-134a and R-410A. Comparisons between the classical vapor compression air conditioner and the solar assisted air conditioner and also between the selected refrigerants are investigated. The effects of the refrigerant temperature leaving the storage tank on the main performance parameters such as the coefficient of performance, the gain based on compression work, and the required condenser surface area are discussed.     

A new route to graphene starting from heavily ozonized fullerenes: Part 2—oxidation in air

Graphite oxide (GO) and heavily ozonized C₆₀ and C₇₀ fullerenes known as “fullerene ozopolymers” were studied by TGA-FTIR (Thermogravimetry coupled with FT-IR spectroscopy), DTG (Differential Thermogravimetry) and DTA (Differential Thermal Analysis) in air flow. It was found that GO burns at 70°C higher temperature than the fullerene ozopolymers. This different behavior toward the thermal oxidation of GO is due to the size of the oxidized and staked graphene layers which are expected to be significantly larger than those of the fullerene ozopolymers. Furthermore, the latter should necessarily have a buckybowl shaped structure which should favor their reactivity with oxygen.     

Virial coefficients of nitrogen,oxygen, and air at temperatures from 75 to 2500°k

The second and third virial coefficients are calculated for the (12-7, ) model pair potential. With their help the fourth virial coefficient is determined from the experimental data on p, , and T. The limit of applicability of the equation of state obtained is presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 51, No. 1, pp. 121–124, July, 1986.     

Repair of air–cooled turbine vanes of high–performance aircraft engines – problems and experience

Abstract

Air–cooled turbine vanes made from nickel– and cobalt–base superalloys undergo distortion, cracking, burning, and material degradation in operation. The complex geometry of the parts and the compositional and microstructural heterogeneity of cast alloys impose limitations on the selection of repair methods. Selective chemical stripping of the diffusion coatings; elimination of cracks and restoration of dimensions by joining processes involving both welding and brazing techniques; and formation of coatings by pack cementation are the major processes employed. These processes may give rise to defects that significantly diminish the integrity of the parts.

MST/104