Spectral analysis of an acoustic respiratory signal with a view to developing an apnoea monitor

The movement of air through the air passages during normal respiration generates an acoustic signal which can be detected from the surface of the body at suitable sites with the aid of a microphone applied to the skin. The spectral characteristics of these sounds were analysed to see if they could be differentiated from other sources of sound. During normal respiration the other major source of sound was that transmitted from the heart, and this could be filtered out with a band pass filter. A prototype apnoea monitor was built which utilised these sound signals as an indicator of respiration and underwent preliminary testing. Although such acoustic signals have the potential to indicate respiration, and cardiac sounds can be effectively filtered, further work would be required to recognise and reject other extraneous sources of sound interfering with the respiratory signal.     

等离子熔炼炉及其应用

本文根据文献资料，介绍等离子熔炼炉的基本结构特点、类型和应用，并介绍用于高纯钛合金熔炼的等离子冷床熔炼炉以及美国Lectrotherm公司发明的一种等离子炬与直接电弧电极相结合的冷床熔炼技术。     

Power increase of plasma heating systems by CO2 addition into the furnace atmosphere: Investigations in view of the plasma ladle furnace

For certain steel grades the treatment in conventional ladle furnaces equipped with graphite electrodes may not be advisable because of the risk of carbon pick-up. In these cases metallic plasma torch systems operated with argon as plasma gas may be preferable. However, the maximum active power available from a 3 torch AC argon plasma system is at present limited to about 4 MW. Tests were carried out with 200 kg heats in a pilot furnace equipped with 2 AC argon plasma torches to investigate the arc voltage increase by adding CO₂ to the furnace atmosphere. With 20% CO₂, the voltage of a 30 cm arc was raised from 100 to 173 V. The transfer rate of oxygen from the CO₂ in the atmosphere via the plasma arc to the steel melt was measured by means of steel and off-gas analyses. After formation of a slag layer, about 10% of the oxygen supply injected into the furnace as CO₂ was transferred to the melt. The measured values concerning power increase and oxygen transfer were extrapolated to ladle capacities of 50 to 150 t and 3-torch 12 kA AC plasma heating systems. In a furnace atmosphere containing 60% CO₂, the active power available from a plasma system would be 10 MW as compared to 3.5 MW in pure argon. The oxygen transfer rates proved to be relatively small due to the low gas flow rates of such systems and to the low mass transfer efficiency. The addition of 40% CO₂ would raise the power to heat 110 t of steel at a heating rate of 3 K/min, while the oxygen level would increase within 30 min by less than 10 ppm. The specific CO₂ demand would in that case be 0.12 m³(STP)/t.     

对采用变压器组的大型矿热炉操作方式的探讨

通过理论和实际数据,对采用单相变压器组的大型矿热电炉生产中遇到的问题给予解释,并针对大型矿热炉的操作方式提出相应的改进措施。     

Patterns of calcification in coronary artery disease. A statistical analysis of intravascular ultrasound and coronary angiography in 1155 lesions

BACKGROUND: Target lesion calcium is a marker for significant coronary artery disease and a determinant of the success of transcatheter therapy. METHODS AND RESULTS: Eleven hundred fifty-five native vessel target lesions in 1117 patients were studied by intravascular ultrasound (IVUS) and coronary angiography. The presence, magnitude, location, and distribution of IVUS calcium were analyzed and compared with the detection and classification (none/mild, moderate, and severe) by angiography. Angiography detected calcium in 440 of 1155 lesions (38%): 306 (26%) moderate calcium and 134 (12%) severe. IVUS detected lesion calcium in 841 of 1155 (73%, P < .0001 versus angiography). The mean arc of lesion calcium measured 115 +/- 110 degrees; the mean length measured 3.5 +/- 3.7 mm. Target lesion calcium was only superficial in 48%, only deep in 28%, and both superficial and deep in 24%. The mean arc of superficial calcium measured 85 +/- 108 degrees; the mean length measured 2.4 +/- 3.4 mm. Three hundred seventy-three of 1155 reference segments (32%) contained calcium (P < .0001 compared with lesion site). The mean arc of reference calcium measured 42 +/- 80 degrees; the mean length measured 1.7 +/- 3.6 mm. Only 44 (4%) had reference calcium in the absence of lesion calcium. Angiographic detection and classification of calcium depended on arcs, lengths, location, and distribution of lesion and reference segment calcium. By discriminant analysis, the classification function for predicting angiographic calcium included the arc of target lesion calcium, the arc of superficial calcium, the length of reference segment calcium, and the location of calcium within the lesion. This model correctly predicted the angiographic detection of calcification in 74.4% of lesions and the angiographic classification (none/moderate/severe) of calcium in 62.8% of lesions. CONCLUSIONS: IVUS detected calcium in > 70% of lesions, significantly more often than standard angiography. Although angiography is moderately sensitive for the detection of extensive lesion calcium (sensitivity, 60% and 85% for three- and four-quadrant calcium, respectively), it is less sensitive for the presence of milder degrees.     

N含量对硼钢35MnB末端淬火性能的影响

35MnB钢由40 t EAF-LF-VD-180 mm×180 mm连铸的电弧炉流程和100 t BOF-LF-RH-200 mm×200mm连铸转炉流程冶炼。35MnB钢技术协议要求J19 HRC值为33～41。试验结果表明,电弧炉流程生产的35MnB钢J19HRC值为25～28,转炉流程生产的35MnB钢末端淬火试验J19HRC值为36～41。对比分析了电弧炉流程和转炉流程生产的35MnB钢的末端淬火性能。分析得出,电弧炉流程生产的35MnB钢中的平均N含量高达(80～90)×10^-6、转炉流程为(45～50)×10^-6,电炉钢中高N含量影响了B对提高钢材淬透性的作用,为了保证钢材末端淬火性能,应控制钢中N含量≤50×10^-6。     

矿渣棉生产发展现状的综述

介绍了矿渣棉的应用和具体工艺。长纤维矿渣棉、普通矿渣棉和酚醛树脂矿渣棉制品均可用于热力设备和管道,但不同矿渣棉是在不同条件下实现保温的,矿渣棉吸声板可广泛用于建筑、工程装饰等方面。原料融制工艺有冲天炉熔制、池窑熔制、电弧炉的熔制;纤维成型工艺有喷吹法、离心法、离心吹制。最后说明了发展矿渣棉的必要性。     

有源电力滤波器对电弧炉的电能质量改善

通过将电弧炉的非线性时变电阻模型、波动性模型以及混沌模型线性叠加,在多个原有电弧炉模型的基础上建立了可以根据实际情况和个人需求进行任意调节的综合电弧炉模型,此模型通过参数设计可以表现出电弧炉各方面的特性,通过调节还能够突出表现电弧炉某一方面的特点。应用有源电力滤波器,对所提出的综合电弧炉模型进行了谐波抑制等电能质量方面的改善。应用matalb软件进行了仿真,结果表明理想有源电力滤波器基本可以保证电弧炉不对电网电能质量造成任何影响。     

New algorithm for controlling electric arc furnaces using their vibrational and acoustic characteristics

The processes occurring in arc discharges are analyzed as the sources of acoustic radiation in an electric arc furnace (EAF). Acoustic vibrations are shown to transform into mechanical vibrations in the furnace laboratory. The shielding of the acoustic energy fluxes onto water-cooled wall panels by a charge is experimentally studied. It is shown that the rate of charge melting and the depth of submergence of arc discharges in the slag and metal melt can be monitored by measuring the vibrational characteristics of furnaces and using them in a universal industrial process-control system, which was developed for EAFs.     

直流电弧炉稳弧装置控制特点与C型滤波器特性分析

阐述了直流电弧炉采用稳弧装置的原理、组成、控制特点,并与交流电弧炉所用SVC补偿装置作比较。稳弧装置除TCR型SVC外还包括装设在35kV母线上3次、5次、7次、11次兼高通滤波器。对各滤波器组的特点作了阐述,从而对直流电弧炉稳弧装置形成一个完整概念。     

Power Delivery from the Arc in AC Electric Arc Furnaces with Different Gas Atmospheres

The amount of heat supplied to the electric arc furnace affects the melting rate. Power delivery in a three‐phase EAF is influenced not only by the electric parameters such as arc length and voltage but also by thermal properties of the gases that form the plasma in the arc region. Application of the Channel Arc Model (CAM) suggests that power delivery is enhanced with long‐arc, maximum tap operation and plasma gases with high heat capacity. It is also suggested that foaming improves power delivery due to the presence of gases with high heat capacity.     

线位移测量装置在埋弧炉电极控制中的应用

详细介绍线位移测量装置的设计思想和实现方法,分析了在埋弧炉冶炼过程中线位移测量与电量测量同的时序关系,并讨论了该装置在生产过程中的指导作用,最后,强调指出电信号测量与工艺参数在埋弧炉控制中互相结合的重要性与必要性。     

Relationship between furnace voltage signatures and the operational parameters arc power,arc current,CO pressure,and electrode gap during vacuum arc melting INCONEL 718

Transfer of metal during vacuum arc remelting creates a signature on the voltage waveform called a drop short, and subsequent arc reignition sometimes creates a signature called an anode spike. The frequency of these events is used forin situ control of electrode gap and, at the present time, their use is limited to melting at conditions of constant current and CO pressure. Statistically designed experiments were conducted in a production melt shop to evaluate the influence of the independent variables arc power or current, CO pressure, and electrode gap on the frequency of these events. Approximately 5000 kg of INCONEL 718 alloy 0.406 m diameter electrodes were vacuum arc remelted into 0.457 m diameter ingots. The experimental results produced regression models which show a three way interaction of the independent variables to be the dominant term with increases in each independent variable producing a power-law reduction in frequency. The inverse nature of these relationships is created by the behavior of the cathode spots, system geometry, and unresolved physics. The models perform accurately at gaps <25 mm and exhibit considerable error at gaps >25 mm. Implications of the results are discussed from the standpoint of arc furnace control.     

Nitrogen Removal and Arc Voltage Increase in EAF Steelmaking by Methane Injection into the Arc

Methane injection into the arcs of electric arc furnaces has been shown on pilot scale to lead to a remarkable arc voltage increase at constant arc current and arc length. Recent investigations have been concerned with the associated metallurgical effects making use of a gas‐tight 150‐kg arc furnace operated with two AC plasma torches. A first test with bored graphite electrodes in this furnace confirmed the power increase observed during methane injection. The carburization slowly occurring when 6 % CH₄ were injected into the argon atmosphere of the furnace could be avoided by adding minor amounts of CO₂. A slag layer decreased mass transfer rates without noticeably affecting heat transfer. Manganese loss by evaporation was measured to investigate the influence of power increase and slag layers. From the results, an increase of 200 K was concluded for the melt surface temperature when CH₄ was added to pure argon. Methane injection into the arcs proved to accelerate nitrogen removal considerably. Starting with an intentionally high nitrogen content of about 200 ppm, the nitrogen removal rate was found to be slowest with pure argon plasma arcs, faster with 90 % Ar + 10 % H₂, and fastest with 95 % Ar + 5 % CH₄ reaching final contents of less than 20 ppm of nitrogen. Based on thermodynamic calculations, the denitrogenation reactions appear to take place via atomic nitrogen in pure argon plasma, via NH₃ in Ar + H₂ and via HCN in Ar + CH₄.     

Increasing the arc efficiency by the removal of arc electromagnetic blowing in electric arc furnaces: I. Effect of electromagnetic blowing and the slag height on the arc efficiency in an electric arc furnace

The effect of electromagnetic blowing and the slag layer height on the arc efficiency is analytically studied. An arc is blown from under an electrode toward the furnace walls under an electromagnetic force. The arc efficiency of a 100-t high-power electric arc furnace changes from 0.47 to 0.76 when the slag height increases from 0 to 550 mm.     

Analysis of Distribution of Nonmetallic Inclusions in Aluminum DC-Cast Billets and Slabs

Inclusion distribution was studied in commercial aluminum DC-cast billets and slabs using a newly developed deep-etching method. Analyses revealed a nonuniform distribution of nonmetallic inclusions across billet diameters and lengths, and also across slab thicknesses and widths. In as-cast billets, more inclusions were found at the beginning and end of the billet length; more were present near the cross-section center than near the surface. In slabs, inclusions were located mostly within 13 mm of the surface and in a band between the centerline and the surface. Few inclusions were found 60 to 100 mm from the slab surface or at the centerline. In addition, comparing slab quality after casting using three types of ceramic foam filters (CFFs; i.e., 30 ppi, 50 ppi, and 50 ppi + HF) revealed significant differences in inclusion size, number, and distribution. Casting slabs using a finer pore-size filter (50 ppi) reduced the number of non-metallic inclusions greatly. The inclusion distribution patterns observed in the solidified slabs are discussed in terms of melt flow during casting.     

Metal transfer during vacuum consumable arc remelting

An investigation was conducted to determine how metal is transferred during vacuum consumable arc remelting. The transfer mode was found to be dependent on arc length for the electrode sizes (0.10 to 0.20 m diam) and electrical parameters studied (1.9 to 3 kA and 25 V). At short arc lengths ≤0.03 m, metal transfer was found to occur when liquid metal spikes hanging from the cathode form a low resistance bridge (drop short) by touching the anode and then subsequently rupture. The formation and rupture of these molten metal bridges was confirmed with electrical resistance measurements. During the bridge lifetime (0.0003 to 0.020 s) the arc was extinguished and all of the electrical power was directed through the molten bridge. At long arc lengths (>0.1 m) the spikes separate before touching the anode. Experimental observations concerning the coalescence of molten material at the cathode tip were made and they were found to be in agreement with theories on liquid instabilities. A review of pertinent literature concerning vacuum arcs was conducted and this along with general information on vacuum consumable arc re-melting are included as background information.     

手指式竖炉电弧炉的应用

在电弧炉炼钢领域 ,德国FUCHS公司开发的手指式竖炉电弧近年受到了普遍的重视。介绍手指式竖炉电弧炉的特点 ,并展望了未来的发展趋势。     

Nondestructive evaluation of steels using acoustic and magnetic barkhausen signals—I. Effect of carbide precipitation and hardness

The effect of microstructures on acoustic and magnetic Barkhausen signals has been investigated in a quenched and tempered steel and spheroidized steels with various carbon contents. Many different features between the acoustic and magnetic Barkhausen signals were observed. A major peak of the acoustic Barkhausen signal was induced when a magnetic field was increased from zero to the saturation state. A minor peak of the acoustic signal and a single peak of the magnetic signal appeared during the decreasing field. It was found in all the steels that the peak value of the acoustic Barkhausen signal shows a linear dependence on the sweep rate of a magnetic field while that of the magnetic Barkhausen signal does a nonlinear one. The increasing tempering temperature which gives rise to a decrease in hardness and an increase in carbide size and spacing caused that acoustic and magnetic Barkhausen peak voltages to increase precipitously and gradually, respectively. In the spheroidized steels, the acoustic peak voltage monotonically decreased with increasing carbon content from 0.17 to 0.96 wt% and the magnetic peak voltage was greatest when the carbon content was 0.46 wt%. The source mechanisms of the two types of the Barkhausen signals which are affected by the nucleation and growth processes of domains in a magnetic field are discussed to explain the effect of the change in carbide precipitate morphology and hardness.     

30MVA直流电弧炉冶炼钛渣配碳比研究

工业生产中,为生产出合格的钛渣必须加入适量的碳作为还原剂,将高价氧化物还原为低价氧化物。云南某公司30 MVA大型密闭直流电弧炉(DC炉)生产运行过程中,通过控制无烟煤用量与钛精矿用量之比——配碳比(ratio of anthracite to ilmenite,简称AIR),使生产在输入能量一定、钛精矿成分稳定的条件下力求获得良好的产品品质。生产通过中空石墨电极将钛精矿和无烟煤加入DC炉内,熔炼温度控制为1973～2023 K;熔炼输入功率为15 MVA;入炉钛精矿粒度为0.1～0.33 mm;入炉无烟煤粒径为5～25 mm的比例大于85%。理论上熔炼还原1 t钛精矿,将会产出526 kg渣和368 kg金属铁,O/I比率约为89.4%,理论配碳比约为7.895%。通过生产物料衡算得出,一定熔炼周期内的AIR平均值为12.228%,O/I比率平均值为81.317%。在配碳量不足的情况下,钛精矿中的FeO易于离解出氧并与碳结合,使FeO还原反应优先于TiO2等氧化物,碳最大可能的消耗在FeO的还原上;配碳量越高,则碳将用于还原难还原的氧化物(如MgO,CaO,MnO等)上,使FeO的还原受到抑制。配碳比还会影响DC电炉熔渣流动性和挂渣层。试生产熔炼周期内,通过调整AIR,实现了钛渣中TiO2品质的提高,其含量可从82%提高到89%以上。