InAsSb light-emitting diodes for the detection of CO2 (λ=4.3 μm)

The main characteristics of room-temperature light-emitting diodes (λ=4.3 μm) based on InAsSbP/InAsSb/InAsSbP III–V semiconductor heterostructures with a variable-gap buffer layer are reported. An optical power P=0.85 mW was achieved with a pulse length of ∼5 μs and 1 kHz repetition frequency. Conditions for maximizing the power of the light-emitting diodes are indicated. An example is given of the use of these diodes to detect carbon dioxide using the 4.3 μm fundamental absorption band. Pis’ma Zh. Tekh. Fiz. 24, 34–41 (August 12, 1998)     

UV Raman spectral intensities of E. coli and other bacteria excited at 228.9, 244.0, and 248.2 nm

Resonance Raman spectral intensities per average bacterial cell have been measured quantitatively for Gram-negative Escherichia coli, Citrobacter freundii, and Enterobacter aerogenes, as well as Gram-positive Bacillus subtilis and Staphylococcus epidermidis. Spectra have been obtained from cultures in the lag, log, and stationary growth phases excited in turn by 228.9, 244.0, and 248.2 nm light. Although Raman spectral peak positions (cm(-1)) excited by a given wavelength are very similar for all five bacterial species, the organisms are characterized by significantly different spectral intensity values. Intensity changes are associated with growth phase changes in all of the species as well. A comparison of measured with estimated average intensities has been made for spectra of log-phase E. coli. It is possible to compare measured intensities with intensities estimated for log-phase E. coli on the basis of the knowledge of its known average cellular molecular composition. A significant degree of hypochromism is observed in E. coli nucleic acid spectra. In contrast, strong average hyperchromism characterizes all aromatic amino acid peaks belonging to the same E. coli cells. Results suggest that knowledge of spectral intensity values will enhance significantly the capability to identify bacteria by means of their UV resonance Raman spectra.     

Emissivity of steels and alloys in the spectral region 2–13 μm

The spectral emissivity of steels and alloys in the temperature range 700–900°K is experimentally studied.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 50, No. 4, pp. 620–625, April, 1986.     

Numerical study of spectral intensity of emission and absorption of the CO2 and CO molecules under vibrationally nonequilibrium conditions

Numerical calculations are performed of the spectral intensity of emission and absorption of the 4.3- and 2.7-m bands of CO₂ and of the 4.7-m band of CO under conditions of nonequilibrium excitation of the vibrational degrees of freedom.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 5, pp. 805–813, May, 1982.     

通过控制二氧化碳含量来实现节能和优化空气质量

"需求控制通风"(DCV)是近年新兴的一种通风控制策略.它通过对室内外二氧化碳浓度差的控制,为工程设计和业主解决了一个难题:如何在节省能源开支的同时又优化空气质量?本文主要通过与传统通风系统作比较,介绍需求控制通风系统的基本原理,优点及应用.同时,还介绍需求控制通风系统的安装及使用的一些问题.     

Leung-Griffiths model for the thermodynamic properties of mixtures of CO2 and C2H6 near the gas-liquid critical line

Leung and Griffiths have proposed a fundamental thermodynamic equation for a binary mixture near the critical line and have successfully applied it to the mixture of He³ and He⁴ in which the critical line is a nearly linear function of composition. We have used a Leung-Griffiths type equation of state to describe the thermodynamic properties of the mixture of carbon dioxide and ethane. The critical line of this mixture is, unlike that of He³ and He⁴, a nonlinear function of composition, and the azeotropic line extends to the critical line. Comparison of the predictions of the equation to experimental data shows a good agreement for the mixture of CO₂ and C₂H₆.     

Two-tone frequency-modulation spectroscopy for quantitative measurements of gaseous species: theoretical, numerical, and experimental investigation of line shapes

The capability of retrieving spectral information from line shapes recorded by two-tone frequency-modulation spectroscopy (TTFMS) is investigated. A TTFMS theory accounting for dispersion and nonlinear distortion of diode laser frequency modulation response is presented. The adequacy of the theory for a detailed modeling of line shapes recorded with high resolution is examined. An extensive error analysis of line parameters (i.e., width, intensity, and line center) retrieved by a nonlinear least-squares fitting procedure is made. Plots of residual errors with characteristic signatures that are due to incorrectly assigned modulation parameters and choice of line profile are presented. In least-squares fits to experimental oxygen data with a Voigt profile influence from collisional(Dicke) narrowing is clearly exhibited, and when we used a collisionally narrowed line profile deviations of the model were reduced to less than 0.2%. We demonstrate that accurate quantitative measurements by TTFMS over a wide range of concentrations, temperatures, and pressures are possible.     

新型航空发动机前后冷气导管CO2激光焊研究

航空燃气涡轮发动机前后冷气导管是一薄壁零件,材质为Ｉｎｃｏｎｅｌ６２５高温合金。本文介绍了采用ＣＯ２激光进行焊接的工艺措施。结果表有,焊缝平整,均匀,热影响极小,焊缝强度σｂ达到母材的９６％。     

The radiation of alumina melt in the middle IR spectral region at solidification in the course of free cooling

The results are presented of radiation intensity measurements in the middle IR spectral region from 3 to 11 μm at cooling and solidification in ambient air for both “thick” layers several millimeters thick and “thin” layers several tenths of a millimeter thick of a pure aluminum oxide melt. In the former case, the melt was held in a powder bed of the same material; in the latter case, a pool with the melt was created on a ceramic surface. The results on different wavelengths are presented as time dependences of the infrared spectrometer signals, proportional to the intensity of radiation emitted by the melt. In addition, the data on the time dependence of the emissivity for thick melt layers at a solidification plateau are presented. On the basis of the obtained results and the results of previous investigations and radiative-conductive heat transfer calculations at cooling and solidification, it is shown that the intensity of emitted radiation at crystallization is defined not only by optical properties of a melt and a crystal, but depends also on the thickness and the temperature field of the melt before the start of cooling. An almost horizontal section on the solidification plateau is caused by the presence of an isothermal two-phase zone; however, with a melt thickness of several millimeters, such a section of different length is observed only in the range of wavelengths from 5 to 11 μm.     

Mechanical stress and thermal-elastic properties of oxide coatings for use in the deep-ultraviolet spectral region

Mechanical stress and the structures of SiO2, Al2O3, and HfO2 single oxide layers and of high-reflection multilayer coatings deposited by reactive evaporation, plasma ion-assisted deposition, and ion-beam sputtering have been studied. The stress was related to the microstructure and to the incorporation of water by means of infrared spectroscopy. From the slopes of measured stress-temperature curves of these coatings deposited onto two substrate materials (silicon and fused silica), the biaxial moduli and the thermal expansion coefficients of the films were estimated.     

Harnessing the Hybridization of a Metal-Organic Framework and Superbase-Derived Ionic Liquid for High-Performance Direct Air Capture of CO2

Direct air capture (DAC) of CO₂ has emerged as the most promising “negative carbon emission” technologies. Despite being state-of-the-art, sorbents deploying alkali hydroxides/amine solutions or amine-modified materials still suffer from unsolved high energy consumption and stability issues. In this work, composite sorbents are crafted by hybridizing a robust metal-organic framework (Ni-MOF) with superbase-derived ionic liquid (SIL), possessing well maintained crystallinity and chemical structures. The low-pressure (0.4 mbar) volumetric CO₂ capture assessment and a fixed-bed breakthrough examination with 400 ppm CO₂ gas flow reveal high-performance DAC of CO₂ (CO₂ uptake capacity of up to 0.58 mmol g⁻¹ at 298 K) and exceptional cycling stability. Operando spectroscopy analysis reveals the rapid (400 ppm) CO₂ capture kinetics and energy-efficient/fast CO₂ releasing behaviors. The theoretical calculation and small-angle X-ray scattering demonstrate that the confinement effect of the MOF cavity enhances the interaction strength of reactive sites in SIL with CO₂, indicating great efficacy of the hybridization. The achievements in this study showcase the exceptional capabilities of SIL-derived sorbents in carbon capture from ambient air in terms of rapid carbon capture kinetics, facile CO₂ releasing, and good cycling performance.     

An experimental investigation of the spectral composition of radiation behind the shock-wave front in a CO2-N2-Ar mixture

Experiments are performed to determine the spectral distribution of radiation in CO₂-N₂ and CO₂-N₂-Ar mixtures in a microwave discharge and behind the front of incident shock wave at velocities up to 7.5 km/s. It is demonstrated experimentally that the spectral region of vacuum ultraviolet makes a significant contribution to radiation.     

Computer Automation and Error Analysis of a CO2-Laser Long-Path Absorption System for Air Pollution Monitoring

A CO2-laser long-path absorption system for air pollution monitoring has been computer automated. Both the lasers and the electronic circuits are controlled by a computer. Real-time estimation of both systematic error and imprecision is used to select an optimum measurement strategy for each different pollution situation expected. The system has been used in a field experiment in the vicinity of a petrochemical industry where ethylene and vinyl chloride are produced. Ethylene concentrations from below 30 up to 400 ppb were monitored using path lengths of 500-2800 m. The concentrations of vinyl chloride were generally small (< 50 ppb). The systematic errors of the measurements were typically 5-10 percent and the imprecision 5-25 percent.     

Method of spectral compensation and its application in the ultraviolet for sulfur dioxide control with a gas-filter correlation instrument

Changes in structureless spectra that are due to the presence of interfering absorbers or light source instabilities, changes in the spectral transfer function of the optics, and changes in the detector's spectral responsivity degrade measurement accuracy. A method of compensating for changes in structureless spectra is developed for a gas-filter correlation instrument. It is shown that there are points in the spectrum where the effect of the interfering component's having a structureless spectrum on the measurement can be drastically reduced.