Air Borne Research Articles

Pattern of Hexa-Valent Chromium in Air Borne Respirable Dust Generated at Various Workplaces in Opencast Chromite Mines

The paper presents a study into air borne respirable dust (ARD) concentration at various workplaces in two open cast chromite mines of Sukinda chromite belt, India. One of these mines is mechanised and the other one is semi-mechanised. The study has been conducted in three phases and ARD concentration has been measured at various workplaces in both the mines. Apart from the determination of ARD concentration, the dust samples collected on filter papers were analysed for hexa-valent chromium by colorimetric method and Cr(VI) direct absorption measurement. In addition, the particle size ranges in ARD have been determined by using cascade impactor fitted onto high volume samplers and laser guided particle size analyser. The paper finally presents a comparison between ARD concentration vis-à-vis the presence of hexa-valent chromium concentration in collected samples of both mechanised and semi-mechanised mines.

Land mine detection by time reversal acousto-seismic method

We present a concept and results of a pilot study on land mine detection based on the use of time reversal acoustics (TRA). TRA provides a possibility of highly effective concentrating of seismic wave energy in time and space in complex heterogeneous media. TRA focusing of seismic waves on a land mine increases the detection abilities of conventional linear and nonlinear acousto-seismic methods. Such factors as medium inhomogeneities, presence of reflecting boundaries, which could critically limit conventional acoustic approaches, do not affect TRA based method. The TRA mine detection system comprises several air borne or seismic sources and a noncontact (laser vibrometer) device for remote measurements of the surface vibration. The TRA system focuses a seismic wave at a surface point where the vibration is measured. The focusing point is scanned across the search area. The amplitude and frequency dependence of the signal from the seismic wave focusing point and nonlinear acoustic effects are analyzed to assess probability of the mine presence. Preliminary experiments confirmed high focusing ability of the TRA seismo-acoustic system in complex conditions (a laboratory tank with sand) and demonstrated a significant increase in the surface vibration in the presence of mine imitator. [Work supported by DoD grant.]

Microwave Technology for Treatment of Fume Hood Exhaust

CHA Corporation installed a fume hood adsorber (scrubber) unit onto an operating fume hood and microwave regeneration system in the Safety and Risk Management Building at the Advanced Technology Park in Bozeman, Montana. The microwave-based fume hood exhaust purification process is designed to capture hazardous air pollutants in the fume hood exhaust using granular activated carbon (GAC) and natural zeolite, and subsequently either recover or destroy desorbed pollutants by microwave energy during regeneration of the saturated adsorbents. Onsite testing of this prototype microwave system was conducted using a variety of air borne pollutants including toluene, ethyl acetate, methylene chloride and hydrochloric acid. Test results showed that microwave energy, at a frequency of 2,450 MHz, restored the original adsorption capacity of saturated GAC and saturated natural zeolite. The results also demonstrated that microwave-induced catalytic oxidation was capable of providing oxidation efficiencies greater than 99% with oxidation temperatures below 100°C.

Sensor for optically sensing air borne acoustic waves

The present invention relates to an optical sensor of air borne acoustic waves. The sensor comprises means for producing mutually coherent optical sampling and reference beams, which may be combined to form an intermediate frequency carrier, the sampling beam being exposed to the acoustic field, in which acoustic wave induced density variations occur. These density variations produce a variation in the index of refraction and thereupon a phase modulation of the sampling beam. This phase modulation may be recovered by an optical detector and a phase detector as an electrical signal representative of the acoustic signal. The invention has application to security systems.

Aerobiology, biodiversity and chemistry of plant trichomes in the tropics at Bodh Gaya, India – a biopollutant and the suspected human allergen

Aerobiology, diversity and chemistry of some air borne plant trichomes were studied at Magadh University campus, Bodh Gaya, India between September 1995 and August 1996. Thirty-three morphotypes of trichomes were tapped using a Gravity Air sampler. The different types of trichomes showed pronounced seasonality in their distribution pattern. The simple non-septate trichomes of grasses were predominant throughout the year. The other commonly observed trichomes were comparable to that of Chrysanthemum, Tridax, Solanum, Amaranthus and Martynia. Trichomes. The Shannon diversity index of trichomes fluctuated widely (1.063–2.867) during different months of the year. This suggests that seasonality had definite bearing on the composition of aerobiota. Relative humidity was found to play greater role in the case of a number of morphotypes (67%), diversity index (50%) and species richness (61%) but in the case of index of dominance (62%), rainfall played a greater role at P < 0.01 level. The trichomes of a few selected plant species, the pollen grains of which are reported allergens, were chemically analysed by collecting them in bulk. They were found to be fairly rich in their total protein (9.58 to 93.60 mg/g) and carbohydrate (10.0 to 20.20 mg/g) contents.

Analysis of main bearing force and cylinder block vibration related to engine air borne noise

Analysis of main bearing force and cylinder block vibration related to engine air borne noise

Hot particles in industrial waste and mining tailings

Industrial waste was studied concerning its radioactive pollution. Using known properties of the solid state nuclear track detector CR-39 we found among a high concentration of more or less homogeneously distributed single α-tracks discrete spots of very high enrichments of α-particles created by so called hot particles. We will report about the α-activity, the concentration of hot particles and about their ability to be air borne.

Insect drift over the northern Arabian sea in early summer

Air borne insects, mostly carried by wind currents, were trapped over the northern Arabian sea (16‡ to 20‡ N; 68‡ to 72‡ E), in the course of cruise No. 111, ORVSAGAR KANYA (March 14 to April 7, 1996). A total of 2,301 insects belonging to 8 different orders, 47 families and 173 species were trapped. Of these, Hymenoptera was represented by the largest number (1082), which was followed by Hemiptera (586), Diptera (552), Coleoptera (51), Neuroptera (10), Trichoptera (03), Lepidoptera (03) and Orthoptera (01). The trapped insects were mostly between 0.6 mm to over 11 mm long. The data was examined for α-diversity as well as for possible correlations between various parameters like the diversity index, size and number of insects trapped on one hand and the distance of the nearest land mass in wind direction, on the other.

Environmental Tobacco Smoke and Respirable Suspended Particle Exposures for Non-Smokers in Beijing

The study was centred in Beijing, People's Republic of China, and comprised housewives in one group, primarily for assessing exposures in the home, and office workers in a second group to assess the contribution of the workplace to overall exposure. Two hundred and fifty-three randomly selected non-smok ing subjects collected air samples near to their breathing zone by wearing per sonal monitors for 24 h. Samples collected were analysed for respirable sus pended particles (RSP), nicotine, 3-ethenylpyridine and environmental tobac co smoke (ETS) particles using ultraviolet absorbing particulate matter (UVPM), fluorescing particulate matter (FPM) and solanesol-related particu late matter (SolPM) measurements. Saliva cotinine analyses were also under taken to confirm the non-smoking status of the subjects, and a misclassifica tion rate of between 3.4 and 3.8% was estimated. RSP levels were the highest reported to date by these authors, with median 24-hour time-weighted average concentrations varying between 70 μg.m-3 for housewives living in non- smoking households and 114 μg.m -3 for office workers both living and work ing in smoking environments. High background levels of unidentified air borne fluorescing compounds in Beijing resulted in abnormally high FPM esti mates and precluded the use of this marker in the assessment of ETS exposure. The highest exposures to ETS particles (SolPM) and nicotine were estimated for office workers living and working in smoking environments. These sub jects would potentially inhale between 5 and 11 cigarette equivalents per year (CEs/y), based upon median exposures, with the workplace contributing approximately 40% of this exposure. The most highly exposed subjects in this study, based upon 90th percentile exposures, would potentially inhale between 32 and 46 CEs/y.

Dynamic modelling of a synchronous linear motor with permanent magnet excitation and solid yokes

A three‐axes synchronous torque motor with permanent magnet excitation and solid stator and rotor yoke is used to adjust an air borne telescope and to eliminate oscillations. Hence the motor is part of a complex mechanical system and has to be included in the structural analysis. For this reason the attempt is made to simulate the nonlinear behavior of the motor by a dynamic model considering the eddy current fields and the magnetization characteristic of the iron.

Evolution der akustischen Kommunikation (Phylogenese)

The evolutionary transition from mammal like reptiles to mammals is accompanied by two major phylogenetic changes that affected the development of acoustic communication: First, changes in the jaw joint freed the later middle ear ossicles from participating in the feeding apparatus and thereby creating a functional middle ear. This functional middle ear is a basic requirement for perceiving air borne sound and was of fundamental importance for small nocturnal mammals to survive in a world dominated by dinosaurs. Second, a major increase of the neocortex occurred. This increase of the neocortex induced significant changes in the basic anatomy of the central sensory, but affected them in different ways. A topographic somatosensory representation of the body surface in terms of a highly ordered map only exists in the neocortex and has no precursor in other brain structures, and thus has most likely been established in the context the development of the neocortex. The dominating sensory system of the mammal-like reptiles, the visual system, has been fundamentally chang-ed: The primary visual center, the tectum opticum in the midbrain, has been replaced by a new neocortical center, the visual cortex. In contrast, in the auditory system the original basic subcortical integration center, the inferior colliculus has been preserved. The inferior colliculus has multiple connections to premotor and motor centers as well as to centers of major importance for motivation and mental status. Higher centers of auditory processing of speech and semantic information have been established behind the inferior colliculus but did not replace it. This conservation of the direct connection of a subcortical integration center with centers of motivational control that in turn can affect the neocortex might be the reason for the successful use of music and familiar voices as treatment in persistent-vegetative-state-rehabilitation.

Attenuation of fluid borne noise from hydraulic piston pumps

In many hydraulic systems, fluid borne noise is generated during operation due to the effects of the hydraulic piston pump. This fluid borne noise is transmitted to various structures of the hydraulic system which emit vibrations that create the largest portion of the system air borne noise. In the subject invention, an apparatus is provided for the attenuation of fluid borne noise. The apparatus includes a sensor arrangement operative to sense operating system parameters and deliver signals representative thereof to a microprocessor, a porting arrangement within the hydraulic piston pump that includes a secondary port, a fluid chamber, and first and second passageways interconnecting the secondary port, the fluid chamber, and a discharge passage. The microprocessor receives the signals from the sensor arrangement and directs electrical command signals to an electrically controlled valve mechanism disposed in the first and second passageways. The microprocessor and the valve mechanism operate to control fluid flow between the discharge passage, the fluid chamber, and the secondary port. By pressurizing fluid in the fluid chamber which in turn pre-pressurizes the piston port through the secondary port prior to the piston port entering the discharge passage, the flow required to pressurize the piston port prior to the piston port entering the discharge passage is spread over a larger range of piston port rotation.

Effects of airborne dust collected from Kuwait on human erythrocytes

Abstract Air borne dust as deposited on air conditioner's filter was collected from most polluted regions of Kuwait and for comparison also from Dubai. Kuwait dust samples were found to contain high concentrations of Ni, Mn and Pb and a number of organic compounds different from the oil samples collected from the oil pool in the oil fields. Toxicity evaluation against human erythrocytes showed strong hemolytic nature of the dust. Treatment of erythrocytes with the dust exhibited peroxidative damage of the membrane. The dust collected from Dubai was innocuous. The present data suggest that erythrocyte damaging potential of the dust can be used as a marker of toxicity and provide information about the dissipation of toxic factors from airborne dust with time.

A comparative study of the slurry erosion and free-fall particle erosion of aluminium

A study has been performed of the erosion of aluminium by silica sand particles at a velocity of 4.5 m s −1, both air borne and in the form of a water-borne slurry. Measurements made under similar experimental conditions show that slurry erosion proceeds at a rate several times that of air-borne erosion, the ratio of the two rates depending strongly on the angle of impact. Sand particles become embedded in the metal surface during air-borne particle erosion, forming a composite layer of metal and silica, and provide the major cause of the difference in wear rate. The embedded particles give rise to surface hardening and a significant reduction in the erosion rate. Embedment of erodent particles was not observed during slurry erosion. Lubrication of the impacting interfaces by water appears to have minimal effect on the wear of aluminium by slurry erosion.

A study on the effect of the soil texture on passive microwave remote sensing

Consideration of soil moisture in terms of percentage of field capacity of the soils for the minimization of textural dependence of microwave emission of soils has been studied by several investigators using experimental data (air borne, field and laboratory experiments) and also theoretical procedures. Their conslusions seem to be not in agreement with each other, thus giving way for further investigations into the problem. To derive information on the choice of parameter through which the textural dependence of microwave emission can be minimized, three test sites have been selected with different soil textures and emission characteristics of these soils are calculated using theoretical approaches. The results of the analysis indicate that the minimal textural dependence is seen on microwave emission when the soil moisture is expressed in terms of volumetric moisture content (mv) reduced by the amount of transition moisture (Wt).

Polyurethane Foams for Sound and Vibration Dampening in Automotive Applications

The paper discusses polyurethane foams which reduce structural borne and air borne noise to provide driving comfort.

A Coloured Snow Episode on the Swedish West Coast, January 1987 a Quantitative and Qualitative Study of Air Borne Particles

A Coloured Snow Episode on the Swedish West Coast, January 1987 a Quantitative and Qualitative Study of Air Borne Particles

About Damping Mechanisms for Disk Shaped Tools

Disk shaped tools like circular saw blades and cut off grinding wheels have low axial stiffness, can easily be excited by dynamic bending forces or displacements and are powerful radiation sources of air borne noise. Damping is a practical mean to reduce sound levels. Two different dissipative systems have been introduced: sandwich systems with metal-polymere-metal layers and metal-to-metal systems. The high damping effect of the 3-layer-disks follows from the deformation energy of the polymere material. It could be proved that in metal-to-metal systems the fluid damping of the gas enclosed between the two parts is dominant. Apart from the damping mechanism there is an upper bound for the loss factor which is given by radiation of the near field. For the investigated wheels this limit was of the order of 0.01 above which no marked noise reduction can be achieved.

Die klinische Bedeutung der Konduktanz und Suszeptanz bei 220 und 660 Hz

The tympanometric measurement of conductance and susceptance is useful for getting separated informations about mass, stiffness, and friction of the middle ear structures. From clinical view such a method has to facilitate the preoperative diagnosis in not clarified cases of air borne hearing loss like otosclerosis, stapes-fracture or incus-luxation. In these cases we measured conductance and susceptance by probe-tone-frequencies of 220 and 660 Hz. The preoperative results are compared with the intraoperative diagnosis.

How buildings affect the local climate

Big new developments with large individual apartment blocks still feature in the housing work of many countries in eastern Europe. This article briefly reviews wind tunnel investigations in Hungary which show, inter alia, that the resulting ‘heat island’ can create a poorly ventilated zone above the centre of the development, and that very long facades are vulnerable to air borne pollution. The author is a senior research officer at ETI, the Hungarian Institute for Building Science.