Journal articles: 'Dead air'

1

Verbeck, J. Q. J. C., G. I. M. Worm, H. Futselaar, and J. C. van Dijk. "Combined air-water flush in dead-end ultrafiltration." Water Supply 1, no. 5-6 (June 1, 2001): 393–402. http://dx.doi.org/10.2166/ws.2001.0139.

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Dead-end ultrafiltration has proven itself as a technique for reclamation of backwash water of sand filters and as a pre-treatment step for spiral wound reverse osmosis. A direct result of dead-end filtration is a decreased flux caused by the accumulation of material in the membrane pores and on the membrane surface. Different cleaning techniques are used to remove this accumulated material. Recently a new technique has been introduced, the AirFlush. This technique makes use of air to create higher turbulence as compared to a water flush. At Delft University of Technology research has started into the fundamentals of the combined air- and water-flush. First a series of experiments has been carried out to determine the different flow patterns, followed by experiments to determine which air- and water-velocities give the best cleaning. Finally head loss experiments have been done to get information about the energy dissipated in the system. The results of the head loss experiments have been compared to the theoretical head loss calculated with the theory of heterogeneous two-phase flow.

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HOGUE, CHERYL. "AIR POLLUTION CLEAR SKIES PLAN ALL BUT DEAD." Chemical & Engineering News 83, no. 11 (March 14, 2005): 10. http://dx.doi.org/10.1021/cen-v083n011.p010.

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3

Sheikh-Omar, A., and B. Oh. "Prolapsed proventriculus in dead chicks after air shipment." Veterinary Record 117, no. 6 (August 10, 1985): 134–35. http://dx.doi.org/10.1136/vr.117.6.134.

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4

Zhang, Qing Feng. "Optimal Control of Air Traffic Networks." Advanced Materials Research 945-949 (June 2014): 3300–3303. http://dx.doi.org/10.4028/www.scientific.net/amr.945-949.3300.

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This article will focus on the study of the dynamic dead reckoning algorithm .Dead reckoning technology is the basis for high- traffic and high -density complex airspace management , air traffic is an important component of automated decision-making system . In airspace management , all of the traffic management strategies can be generated by the aircraft 's forecast track . Depending on the precise spatial location and route on expected over time , dead reckoning implementation will significantly reduce the uncertainty in the future of aircraft flight paths , which makes the airspace and airport resources are efficiently used , the safety of an aircraft in the airspace the problem is further protection.

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Govorukhin, Yuri, Victor Krivolapov, Dmitry Paleev, and Vyacheslav Portola. "Numerical Studies of the Aerodynamic Features of Dead-end Entries with Side Junction." E3S Web of Conferences 174 (2020): 01057. http://dx.doi.org/10.1051/e3sconf/202017401057.

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Investigations of aerodynamic processes occurring in dead-end short entriesaired by turbulent diffusion have been performed. The numerical simulation of the processes of air movement through the entry, flow stalling at the junction with the dead-end entry (for side junction), and the formation of vortices at the dead end have been carried out. The study has been done for a wide range of air flows submitted for computation of air consumption and for various geometric parameters of the dead-end entry. The sizes of the vortex structures and the flow rates in the dead endshave been determined. Based on the results of processing the simulation data, we obtained graphs of the dependences between the length of the ventilated zone of the dead end and its height and width.

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6

KEMPEN, PAUL MARTIN. "Minimizing Dead Space, Air Embolism, and Needle-Stick Risk." Anesthesiology 70, no. 6 (June 1, 1989): 1034. http://dx.doi.org/10.1097/00000542-198906000-00040.

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7

Renata, Duffková. "Difference in Canopy and Air Temperature as an Indicator of Grassland Water Stress." Soil and Water Research 1, No. 4 (January 7, 2013): 127–38. http://dx.doi.org/10.17221/6514-swr.

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In 2003–2005 in conditions of the moderately warm region of the Třeboň Basin (Czech Republic) the difference between canopy temperature (Tc) and air temperature at 2 m (Ta) was tested as an indicator of grassland water stress. To evaluate water stress ten-minute averages of temperature difference Tc–Ta were chosen recorded on days without rainfall with intensive solar radiation from 11.00 to 14.00 CET. Water stress in the zone of the major portion of root biomass (0–0.2 m) in the peak growing season (minimum presence of dead plant residues) documented by a sudden increase in temperature difference, its value 5–12°C and unfavourable canopy temperatures due to overheating (> 30°C) was indicated after high values of suction pressure approaching the wilting point (1300 kPa) were reached. High variability of temperature difference in the conditions of sufficient supply of water to plants was explained by the amount of dead plant residues in canopy, value of vapour pressure deficit (VPD), actual evapotranspiration rate (ETA) and soil moisture content. At the beginning of the growing season (presence of dead plant residues and voids) we proved moderately strong negative linear correlations of Tc–Ta with VPD and Tc–Ta with ETA rate and moderately strong positive linear correlations of ETA rate with VPD. In the period of intensive growth (the coverage of dead plant residues and voids lower than 10%) moderately strong linear correlations of Tc–Ta with VPD and multiple linear correlations of Tc–Ta with VPD and soil moisture content at a depth of 0.10–0.40 m were demonstrated.

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Su, Joseph Z., and George P. Crampton. "An Experimental Examination of Dead Air Space for Smoke Alarms." Fire Technology 45, no. 1 (February 7, 2008): 97–115. http://dx.doi.org/10.1007/s10694-008-0043-y.

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9

Möller, Winfried, Sheng Feng, Ulrike Domanski, Karl-Josef Franke, Gülnaz Celik, Peter Bartenstein, Sven Becker, et al. "Nasal high flow reduces dead space." Journal of Applied Physiology 122, no. 1 (January 1, 2017): 191–97. http://dx.doi.org/10.1152/japplphysiol.00584.2016.

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Recent studies show that nasal high flow (NHF) therapy can support ventilation in patients with acute or chronic respiratory disorders. Clearance of dead space has been suggested as being the key mechanism of respiratory support with NHF therapy. The hypothesis of this study was that NHF in a dose-dependent manner can clear dead space of the upper airways from expired air and decrease rebreathing. The randomized crossover study involved 10 volunteers using scintigraphy with 81mKrypton (81mKr) gas during a breath-holding maneuver with closed mouth and in 3 nasally breathing tracheotomized patients by volumetric capnography and oximetry through sampling CO2 and O2 in the trachea and measuring the inspired volume with inductance plethysmography following NHF rates of 15, 30, and 45 l/min. The scintigraphy revealed a decrease in 81mKr gas clearance half-time with an increase of NHF in the nasal cavities [Pearson’s correlation coefficient cc = −0.55, P < 0.01], the pharynx (cc = −0.41, P < 0.01), and the trachea (cc = −0.51, P < 0.01). Clearance rates in nasal cavities derived from time constants and MRI-measured volumes were 40.6 ± 12.3 (SD), 52.5 ± 17.7, and 72.9 ± 21.3 ml/s during NHF (15, 30, and 45 l/min, respectively). Measurement of inspired gases in the trachea showed an NHF-dependent decrease of inspired CO2 that correlated with an increase of inspired O2 (cc = −0.77, P < 0.05). NHF clears the upper airways of expired air, which reduces dead space by a decrease of rebreathing making ventilation more efficient. The dead space clearance is flow and time dependent, and it may extend below the soft palate. NEW & NOTEWORTHY Clearance of expired air in upper airways by nasal high flow (NHF) can be extended below the soft palate and de facto causes a reduction of dead space. Using scintigraphy, the authors found a relationship between NHF, time, and clearance. Direct measurement of CO2 and O2 in the trachea confirmed a reduction of rebreathing, providing the actual data on inspired gases, and this can be used for the assessment of other forms of respiratory support.

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10

Wang, Shu Fang, Zhi Yong Yang, and Ming Hai Li. "Research on Dead-End Tunneling Ventilation Control System." Advanced Materials Research 516-517 (May 2012): 1188–91. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.1188.

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On the basis of analysis of ventilation requirement and CO concentration distribution character in dead-end tunneling, this paper designed the ventilation equipment layout. Furthermore, a control strategy which includes normal ventilation mode and gun smoke discharging mode is established. In view of expert experience and numerical simulation results dead-end tunneling, fuzzy control is adopted to deal with this problem. Control rules principle is described in detail. Applying direct torque speed adjustment mode, an experimental system is designed and implemented. Partial experimental results show that gun smoke emission process is fast in order to increase efficiency, while normal ventilation mode is adjustable air flow for energy conservation.

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11

Kaminski, John E., Peter H. Dernoeden, and Michael A. Fidanza. "Environmental Monitoring and Exploratory Development of a Predictive Model for Dead Spot of Creeping Bentgrass." Plant Disease 91, no. 5 (May 2007): 565–73. http://dx.doi.org/10.1094/pdis-91-5-0565.

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Dead spot of creeping bentgrass is incited by Ophiosphaerella agrostis. The objectives of this 3-year field study were to: (i) elucidate environmental conditions associated with the expression of dead spot symptoms, (ii) develop a model to assist in predicting the appearance of dead spot symptoms and epidemics in creeping bentgrass, and (iii) elucidate the association between ascospore release and the appearance of new dead spot symptoms. Environmental parameters measured included relative humidity (RH), air (AT) and soil (ST) temperatures, solar irradiance (SOL), precipitation and irrigation (RAIN), and leaf wetness duration (LWD). Dead spot symptoms generally did not occur at temperatures (air or soil) below 15°C. Two descriptive models were developed that predicted the appearance of dead spot symptoms with an accuracy of 74 to 80%. Between 1 May and 31 October 2000 to 2002, the appearance of new dead spot infection centers was most accurately predicted (80%) by the single parameter of STMean ≥ 20°C. In years with severe levels of dead spot, the occurrence of major infection events was predicted on 37 of 40 days (93%). A combination of elevated air (ATMax ≥ 27°C) and soil (STMean ≥ 18°C) temperatures, low relative humidity (RHMean ≤ 80%), shortened periods of leaf wetness (LWD ≤ 14 h), and high levels of solar radiation (SOLMean ≥ 230 W m−2) were associated with the development of major dead spot epidemics. Ascospore discharge and the appearance of new infection centers occurred in a cyclic pattern that peaked about every 12 days. New infection centers appeared 3 to 10 days after the release of a large number of ascospores.

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12

Kennedy, M., S. Siriphannon, S. van Hoof, and J. Schippers. "Improving the performance of dead-end ultrafiltration systems: comparing air and water flushing." Water Supply 1, no. 5-6 (June 1, 2001): 97–106. http://dx.doi.org/10.2166/ws.2001.0104.

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A cleaning protocol that effectively removes fouling from hollow fiber UF systems without excessive use of chemicals, product water or (long) down time is needed. Cross flushing with UF feed water has been reported to increase the net flux of hollow fiber systems by reducing the frequency of backwashing, the consumption of permeate and the system down time. In this study, the flux restoration achieved in a vertical and horizontal UF system employing an intermittent water and water/air cross flush were compared. The flux restoration in the vertical UF system was not improved by the addition of air to the water flush and a maximum flux restoration of 82% was achieved, irrespective of the presence of air. Similarly, in a horizontal ultrafiltration system, a maximum flux restoration of 82% was also achieved with a water flush (v = 1.63 m/s). However, the addition of air to the water flush decreased the flux restoration to 40% at the highest water/air ratio (33% air). Low flux restoration in the horizontal system was attributed to residual air in the module after cross flushing. Flushing with water alone (v = 1.63 m/s) yielded a wall shear stress of 16 Pa compared with 130 Pa and 279 Pa in the liquid film surrounding the air slugs in the horizontal and vertical UF system, respectively, with a water/air ratio of 2:1. Despite the high shear force on the cake layer accumulated when air was added to the system, the maximum flux restoration was 82% both with and without air. This was attributed to the fact that it was the filtration mechanism and not the shear force on the cake layer that limited flux restoration during cross flushing. To improve the flux restoration that can be achieved by the cross flushing process, the filtration mechanism must be manipulated to minimize blocking filtration and induce cake filtration from the beginning of each filtration cycle.

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13

Clayton, Wilson S. "Effects of pore scale dead-end air fingers on relative permeabilities for air sparging in soils." Water Resources Research 35, no. 10 (October 1999): 2909–19. http://dx.doi.org/10.1029/1999wr900202.

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14

Saito, Hitoshi, Kazuhiro Nagatake, Hideki Komatsu, Yukihiro Takeshita, Yoshihiko Matsui, Kiyohito Katsumata, and Masayuki Sakaki. "Development of 72/84kV Dry Air Insulated Dead Tank Type VCB." IEEJ Transactions on Power and Energy 129, no. 2 (2009): 353–60. http://dx.doi.org/10.1541/ieejpes.129.353.

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15

Bull, Michael. "No Dead Air! The iPod and the Culture of Mobile Listening." Leisure Studies 24, no. 4 (January 2005): 343–55. http://dx.doi.org/10.1080/0261436052000330447.

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16

Dupont, T., P. Leclaire, O. Sicot, X. L. Gong, and R. Panneton. "Acoustic properties of air-saturated porous materials containing dead-end porosity." Journal of Applied Physics 110, no. 9 (November 2011): 094903. http://dx.doi.org/10.1063/1.3646556.

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17

Saito, Hitoshi, Kazuhiro Nagatake, Hideki Komatsu, Yukihiro Takeshita, Yoshihiko Matsui, Kiyohito Katsumata, and Masayuki Sakaki. "Development of 72/84-kV dry air-insulated dead tank VCB." Electrical Engineering in Japan 177, no. 1 (June 17, 2011): 1–10. http://dx.doi.org/10.1002/eej.21145.

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18

Ayliffe, Alec. "The Development of Airborne Dead Reckoning. Part II: After 1940 – Staying On Track." Journal of Navigation 54, no. 3 (September 2001): 463–76. http://dx.doi.org/10.1017/s0373463301001461.

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The History of Air Navigation Group commissioned the author to provide a brief account of airborne DR development by discussing both the methods and the equipment used in the air. This second and final part covers the period after 1940 which saw the automation of DR techniques from the Air Position Indicator of the 1940s to the Flight Management Systems in current use.

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19

García-Díaz, Manuel, Carlos Sierra, Celia Miguel-González, and Bruno Pereiras. "A Discussion on the Effective Ventilation Distance in Dead-End Tunnels." Energies 12, no. 17 (August 30, 2019): 3352. http://dx.doi.org/10.3390/en12173352.

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Forcing ventilation is the most widely used system to remove noxious gases from a working face during tunnel construction. This system creates a region near the face (dead zone), in which ventilation takes place by natural diffusion, rather than being directly swept by the air current. Despite the extensive use of this system, there is still a lack of parametrical studies discerning the main parameters affecting its formation as well as a correlation indicating their interrelation. With this aim in mind, computational fluid dynamics (CFDs) models were used to define the dead zone based on the airflow field patterns. The formation of counter vortices, which although maintain the movement of air hinder its renewal, allowed us to discuss the old paradigm of defining the dead zone as a very low air velocity zone. Moreover, further simulations using a model of air mixed with NO2 offered an idea of NO2 concentrations over time and distance to the face, allowing us to derive at a more realistic equation for the effective distance. The results given here confirm the degree of conservativism of present-day regulations and may assist engineers to improve ventilation efficiency in tunnels by modifying the duct end-to-face distance.

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20

Zhang, Qing Feng. "New Approach for Modeling of Air Traffic Flow." Advanced Materials Research 945-949 (June 2014): 3275–78. http://dx.doi.org/10.4028/www.scientific.net/amr.945-949.3275.

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Firstly, from the strategic level flow prediction and tactical traffic flow prediction analysis of two methods of flight flow forecast, put forward by the combination method of strategic level forecast, the dead reckoning for the tactical traffic flow prediction. According to the characteristics of dynamic air traffic flow prediction, inference algorithm for aircraft trajectory conjecture by great circle track and isometric track, so as to realize the dynamic traffic prediction. Basic factors that error in in-depth study on track, according to the actual situation of Guangzhou area control center control operation, analyzes and summarizes the influence of dead reckoning uncertainty factors, proposes an equiangular track improved predictive models, and flight data is validated using actual controllers in Guangzhou, the results show that the prediction accuracy of the improved model significant improvement.

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21

Gonçalves, Filipe, and Miguel Cavique. "F-Gas regulation-Possible solutions for the retrofit dead end." MATEC Web of Conferences 178 (2018): 09023. http://dx.doi.org/10.1051/matecconf/201817809023.

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The EU F-gas regulation of 2006 and the recast of 2014 are forcing the market to reduce the use of refrigerants with high global warming potential (GWP). As a result, the production of hydrofluorocarbon (HFC) refrigerants with higher GWP decreased, making the prices of all HFC gases to increase. Any maintenance problem in a refrigeration system asks to evaluate the retrofitting of the gas making necessary to know the expected behaviour of the system. This paper aims to discuss the gases that can substitute the now-a-days HFCs, and the impact the retrofit will cause in a real air-conditioning systems. Many studies on retrofit address the behaviour of the refrigeration cycle, but usually, do not take into account the behaviour of the system as a whole. This paper models a water-to-water air-conditioning system taking into consideration the evaporator and condenser heat exchangers, the refrigeration cycle, the air-conditioning loop and the heat exchanger to the acclimatized area. Moreover, the paper studies the performance of the system when subjected to high condensing temperatures. The paper concludes that all possible retrofit solutions need to use flammable gases that make the refrigeration power of the equipment to reduce.

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22

Seo, Woojin, and Kwang-Ryul Baek. "Indoor Dead Reckoning Localization Using Ultrasonic Anemometer with IMU." Journal of Sensors 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/3542354.

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Dead reckoning is an important aspect of estimating the instantaneous position of a mobile robot. An inertial measurement unit (IMU) is generally used for dead reckoning because it measures triaxis acceleration and triaxis angular velocities in order to estimate the position of the mobile robot. Positioning with inertial data is reasonable for a short period of time. However, the velocity, position, and attitude errors increase over time. Much research has been conducted in ways to reduce these errors. To position a mobile robot, an absolute positioning method can be combined with dead reckoning. The performance of a combined positioning method can be improved based on improvement in dead reckoning. In this paper, an ultrasonic anemometer is used to improve the performance of dead reckoning when indoors. A new approach to the equation of an ultrasonic anemometer is proposed. The ultrasonic anemometer prevents divergence of the mobile robot’s velocity. To position a mobile robot indoors, the ultrasonic anemometer measures the relative movement of air while the robot moves through static air. Velocity data from the ultrasonic anemometer and the acceleration and angular velocity data from the IMU are combined via Kalman filter. Finally we show that the proposed method has the performance with a positioning method using encoders on a good floor condition.

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23

Libert, Xavier, Camille Chasseur, Ann Packeu, Fabrice Bureau, Nancy H. Roosens, and Sigrid C. J. De Keersmaecker. "Exploiting the Advantages of Molecular Tools for the Monitoring of Fungal Indoor Air Contamination: First Detection of Exophiala jeanselmei in Indoor Air of Air-Conditioned Offices." Microorganisms 7, no. 12 (December 10, 2019): 674. http://dx.doi.org/10.3390/microorganisms7120674.

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Today, indoor air pollution is considered a public health issue. Among the impacting pollutants, indoor airborne fungi are increasingly highlighted. Most of the monitoring protocols are culture-based, but these are unable to detect the uncultivable and/or dead fraction or species suppressed by fast-growing fungi, even though this fraction could impact health. Among the contaminants suspected to be part of this fraction, Exophiala jeanselmei is an interesting case study. Known to be pathogenic, this black yeast grows in humid environments such as air-conditioning systems, where it has been previously detected using classical culture-based methods. However, until now, this fungus was never detected in indoor air in contact with these air-conditioning systems. This study shows the first detection of E. jeanselmei in indoor air collected from offices in contact with contaminated air-conditioning reservoirs. While its presence in indoor air could not be demonstrated with culture-based methods, it was found by real-time PCR and massive parallel sequencing. The latter also allowed obtaining a broader view on the fungal diversity in the tested samples. Similar approaches were applied on water samples collected from the conditioning reservoirs to trace the source of contamination. The comparison of results obtained with both methods confirmed that the molecular tools could improve indoor air monitoring, especially of dead and/or uncultivable contaminants or when competition between species could occur.

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24

Branny, M., M. Jaszczur, W. Wodziak, and J. Szmyd. "Experimental and numerical analysis of air flow in a dead-end channel." Journal of Physics: Conference Series 745 (September 2016): 032045. http://dx.doi.org/10.1088/1742-6596/745/3/032045.

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25

Rocha, Vilson de Souza, Ajax de Sousa Ferreira, Bruna Nogueira Leite, Carla Coelho Ferreira, Karla Gabrielle Dutra Pinto, Sara Cruz Pinheiro, and Sônia Maria Figueiredo Albertino. "Dead Cover and Agronomic Characteristics of Cowpea." Journal of Agricultural Science 12, no. 10 (September 15, 2020): 175. http://dx.doi.org/10.5539/jas.v12n10p175.

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Dead cover, or mulch, consisting of plant residues, plays an important role for the success of diverse agricultural crops, working as an insulating layer protecting the soil from daytime temperature variations and maintaining the soil moist and rich in organic matter. Cowpea is a source of proteins, carbohydrates, vitamins and minerals. Its importance in the North, Northeast and Midwest regions of the country is associated with economic and social aspects, since it is an important food for low-income populations, supplying their nutritional needs. This study was carried out under greenhouse conditions in Manaus, state of Amazonas, with the purpose of assessing the effect of different dead covers on the agronomic characteristics of cowpea cultivars. It consisted of a completely randomized design in a 4 × 4 factorial arrangement. The treatments comprised four cowpea cultivars (BRS Caldeirão, BRS Tumucumaque, BRS Guariba and BRS Tracuateua) and three species of cover plants (Brachiaria decumbens, Brachiaria ruziziensis and Mucuna pruriens) and one control treatment, without soil cover, in a total of 16 treatments, with four replications and two plants per experimental unit. Analysis of variance was applied to the data, and the means were compared by the Scott-Knott’s test at 5% probability level. The following characteristics were examined: number of pods per plant, pod length, number of seeds per pod, weight of shoot dry matter, and grain yield. Mulching provided better results for all characteristics assessed in the four cultivars when compared to the control. BRS Caldeirão is the recommended cultivar for the state of Amazonas and the other regions with similar edaphoclimatic characteristics (high air temperature, rainfall, air humidity, and low-fertility tropical soils) because it exhibited the greatest number of pods per plant, number of seeds per pod, shoot dry matter, and the highest average grain yield (Freire Filho et al., 2011; Souza et al., 2016).

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Yin, Zhao Lei, Zhe Wang, Chen Le Sun, and Tong Zhang. "Effect of Ignition Timing and Excess Air Ratio on Combustion Characteristic of Linear Engine." Advanced Materials Research 724-725 (August 2013): 1340–43. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.1340.

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Based on the linear engine prototype designed by the studying team, the combustion characteristic of the linear engine in certain revolution is investigated experimentally. The effect of ignition timing and excess air ratio on combustion characteristic of the linear engine is studied based on cycle-by-cycle control technique. The result shows that the ignition timing has effect on the combustion characteristic of linear engines in certain revolution. Advancing the ignition timing from 1.0mm BTDC (before the top dead center) to 3.0mm BTDC, the peak cylinder pressure increases, the interval between peak cylinder pressure timing and the top dead center reduces, the IMEP (indicated mean effective pressure) is down, the instantaneous heat release rises and the total heat release decreases. The excess air ratio has apparently effect on combustion characteristic of linear engines in certain revolution. Reducing the excess air ratio from 1.45 to 1.35, the peak cylinder pressure increases, the peak cylinder pressure timing is closer to the top dead center, the instantaneous heat release and the total heat release are larger.

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Nehorai, Roni, Nadav Lensky, Steve Brenner, and Itamar Lensky. "The Dynamics of the Skin Temperature of the Dead Sea." Advances in Meteorology 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/296714.

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We explored the dynamics of the temperature of the skin layer of the Dead Sea surface by means of in situ meteorological and hydrographic measurements from a buoy located near the center of the lake. The skin temperature is most highly correlated to air temperature (0.93–0.98) in all seasons. The skin temperature is much less correlated to the bulk surface water temperature in the summer (0.80), when the lake is thermally stratified, and uncorrelated in the winter, when the Dead Sea is vertically mixed. Low correlations were found between the skin temperature and the solar radiation and wind speed in all seasons. The skin, with its low thermal inertia, responds immediately to the atmospheric forcing. Heat fluxes across the sea surface are also presented. The high correlation of skin temperature to air temperature with minimal time lag is a result of the nearly immediate response of the thin skin layer to the surface heat fluxes, primarily the sensible heat flux.

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ITOMI, Muneji, Daiwa SATOH, Yutaka TABE, and Takemi CHIKAHISA. "D201 Effect of Air Flow Conditions on Water Transport in Air-Breathing PEMFC with Dead-End Hydrogen Flow." Proceedings of the National Symposium on Power and Energy Systems 2012.17 (2012): 339–40. http://dx.doi.org/10.1299/jsmepes.2012.17.339.

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29

Powell, F. L., and S. C. Hempleman. "Sources of carbon dioxide in penguin air sacs." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 248, no. 6 (June 1, 1985): R748—R752. http://dx.doi.org/10.1152/ajpregu.1985.248.6.r748.

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CO2 tensions in the caudal air sacs of birds cannot be quantitatively predicted by current models of avian respiration, mainly because the contribution of neopulmonic parabronchial gas exchange has not been determined. To overcome this problem we studied penguins that have purely paleopulmonic lungs. Three penguins were anesthetized, intubated, and ventilated at a constant respiratory rate and different tidal volumes (VT). PO2 and PCO2 were measured in arterial blood and end-expired, mixed-expired, interclavicular air sac, and caudal thoracic air sac gas. Interclavicular air sac and end-expired gas had similar compositions. Caudal thoracic air sac gas was intermediate in composition to end-expired and inspired gas, and its PCO2 was 1.5–3.5 times greater than the value predicted from reinhaled dead space. This difference between measured and predicted caudal thoracic air sac PCO2 increased with VT but showed no relationship to changes in dead space-to-VT ratio. The difference is not explained by stratification or diffusive gas exchange across air sac walls. The results can be explained by postulating that inspired gas passes over exchange surfaces on its path to caudal air sacs. This is unexpected in the purely paleopulmonic lungs of penguins and suggests that airflow may not be caudocranial in all paleopulmonic parabronchi.

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30

Ayliffe, Alec. "The Development of Airborne Dead Reckoning. Part I: Before 1940 – Finding The Wind." Journal of Navigation 54, no. 2 (May 2001): 223–33. http://dx.doi.org/10.1017/s0373463301001199.

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The History of Air Navigation Group commissioned the author to provide a brief account of airborne DR development by discussing both the methods and the equipment used in the air. This first part covers the period before 1940. The split is arbitrary, although it is obvious from a British perspective that military events around that date had a major impact on the pace of navigation development. However, it is equally obvious that airborne DR developed alongside a worldwide technical and intellectual revolution. This aspect of the story is abstract and involves some conjecture, so the paper takes it for granted and concentrates instead on practical matters. Accounts of air navigators' experiences as well as material on DR theory and descriptions of DR equipment in navigation manuals, journals and various surviving research documents have been used as the source material.

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Dutta, S. P. S., D. Slathia, D. Slathia, and Chandbala K. "Incidences of winter fish kill in subtropical Surinsar Lake (Ramsar Site) in Shivalik hills of Jammu (J&K)." Environment Conservation Journal 15, no. 3 (December 20, 2014): 35–40. http://dx.doi.org/10.36953/ecj.2014.15305.

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Mass mortality of fish was observed in the morning on 02-02-2011 in winter monomictic Surinsar lake, Jammu and has been reported. Maximum count of dead fish was shared by Puntius spp. (P. ticto, P. conchonius and P. sophore). Other dead fishes of family Cyprinidae include Rasbora rasbora, Esomus danrica and Cyprinus carpio communis. A few dead specimens of air breathing Heteropneustes fossilis and Channa punctatus were also seen. In the present paper, possible causes of fish kill have been described.

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32

Goriup, Paul D. "Acidic air Pollution and birds in Europe." Oryx 23, no. 2 (April 1989): 82–86. http://dx.doi.org/10.1017/s0030605300022742.

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Evidence from a survey conducted by the European Continental Section of the International Council for Bird Preservation (ICBP-ECS) suggests that birds have not served as such good early warning indicators of ecological damage from acid precipitation as they have for damage from organochlorine pesticide use. Only a few highly specialized species have been badly affected, and then long after the impact was observed in other organisms. Some birds have even benefited from the superabundance of dead and decaying standing timber.

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33

Xie, Ailiang, Fiona Rankin, Ruth Rutherford, and T. Douglas Bradley. "Effects of inhaled CO2 and added dead space on idiopathic central sleep apnea." Journal of Applied Physiology 82, no. 3 (March 1, 1997): 918–26. http://dx.doi.org/10.1152/jappl.1997.82.3.918.

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Xie, Ailiang, Fiona Rankin, Ruth Rutherford, and T. Douglas Bradley. Effects of inhaled CO2 and added dead space on idiopathic central sleep apnea. J. Appl. Physiol. 82(3): 918–926, 1997.—We hypothesized that reductions in arterial [Formula: see text]([Formula: see text]) below the apnea threshold play a key role in the pathogenesis of idiopathic central sleep apnea syndrome (ICSAS). If so, we reasoned that raising[Formula: see text] would abolish apneas in these patients. Accordingly, patients with ICSAS were studied overnight on four occasions during which the fraction of end-tidal CO2 and transcutaneous[Formula: see text] were measured: during room air breathing ( N1), alternating room air and CO2 breathing ( N2), CO2 breathing all night ( N3), and addition of dead space via a face mask all night ( N4). Central apneas were invariably preceded by reductions in fraction of end-tidal CO2. Both administration of a CO2-enriched gas mixture and addition of dead space induced 1- to 3-Torr increases in transcutaneous [Formula: see text], which virtually eliminated apneas and hypopneas; they decreased from 43.7 ± 7.3 apneas and hypopneas/h on N1 to 5.8 ± 0.9 apneas and hypopneas/h during N3( P < 0.005), from 43.8 ± 6.9 apneas and hypopneas/h during room air breathing to 5.9 ± 2.5 apneas and hypopneas/h of sleep during CO2 inhalation during N2 ( P< 0.01), and to 11.6% of the room air level while the patients were breathing through added dead space during N4 ( P< 0.005). Because raising[Formula: see text] through two different means virtually eliminated central sleep apneas, we conclude that central apneas during sleep in ICSA are due to reductions in[Formula: see text] below the apnea threshold.

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Świeboda, Maria, and Andrzej Kalemba. "The bark of Scots pine (Pinus sylvestis L.) as a biological indicator of atmospheric air pollution." Acta Societatis Botanicorum Poloniae 48, no. 4 (2015): 539–49. http://dx.doi.org/10.5586/asbp.1979.045.

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In dead bark layer 0f Scots pines (Pinus sylvestris L.) exposed to the emission of aluminium works and the electric power plant "Skawina" as well as of chemical plants in Cracow, pH was determined and the content of F, S, Mg, Na, P, K, and Ca. The F content in the dead pine bark varied from 0.018 to 0.386 mg/g, and that of sulphur from 1.00 to 3.83 mg/g. A significant correlation was demonstrated between pH, and fluorine and calcium content in the bark. On the other hand, sulphur content was dependent on the amount of Na, K and Ca. For demonstrating contamination of the surface bark layer a test was applied consisting in evaluation of the germinating and development capacity of seeds. Fluorine content in pine dead bark layer reflects the F concentration in atmospheric air, it may, therefore, serve as indicator of the degree of air pollution with fluorine compounds.

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35

Leclaire, P., O. Umnova, T. Dupont, and R. Panneton. "Acoustical properties of air-saturated porous material with periodically distributed dead-end pores." Journal of the Acoustical Society of America 137, no. 4 (April 2015): 1772–82. http://dx.doi.org/10.1121/1.4916712.

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36

Wehner, Katja, Michael Heethoff, and Adrian Brückner. "Seasonal fluctuation of oribatid mite communities in forest microhabitats." PeerJ 6 (June 4, 2018): e4863. http://dx.doi.org/10.7717/peerj.4863.

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Oribatid mites are abundant and diverse decomposers in almost all terrestrial microhabitats, especially in temperate forests. Although their functional importance in the decomposition system in these forests has been investigated, spatio-temporal patterns of oribatid mite communities inhabiting different microhabitats have largely been neglected. Therefore, we (i) investigated seasonal fluctuation (monthly over one year) in oribatid-mite community structure and specificity to three microhabitats (moss, dead wood and litter) and (ii) analyzed the influence of air temperature and overall air humidity on seasonal community changes. In total, 57,398 adult oribatid mite individuals were collected. Total abundance, species richness and diversity differed among microhabitats. Seasonal changes were most pronounced in moss and least in litter. While overall air humidity had no influence on species distribution and community changes, air temperature positively influenced species richness and diversity, again most pronounced in moss. The calculated environmental temperature occurrence niche showed that 35% of adult oribatid mite species occurred at higher air temperatures. Furthermore, interaction/bipartite networks were more generalized—i.e., species were more equally distributed among moss, dead wood and litter—when ambient air temperatures were higher. This pattern is probably due to the dispersal ability of adult oribatid mites, i.e., species enter a dispersal mode only at higher air temperatures.

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37

Zagoruyko, Mikhail Gennadievich, and Sergey Anatolyevich Pavlov. "Fill ventilation of heated corn grain." Agrarian Scientific Journal, no. 9 (September 24, 2020): 74–77. http://dx.doi.org/10.28983/asj.y2020i9pp74-77.

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The grain masses of the first and subsequent batches, the equivalent coefficient of the dead gap of the air distribution system are calculated, the expressions for calculating the air flow for these batches and the experimental data on the change in moisture and temperature of the grain over time are given.

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38

White, Benjamin Leonardo Alves, and Maria Flaviane Almeida Silva. "ESTIMATING FINE DEAD FUEL MOISTURE CONTENT UNDER EQUATORIAL CLIMATE CONDITIONS." FLORESTA 51, no. 3 (June 22, 2021): 696. http://dx.doi.org/10.5380/rf.v51i3.72389.

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The measurement of the fine dead fuel moisture content (FDFMC) is extremely important for forest fire prevention and suppression activities, as it has a great influence on the ignition probability and fire behavior. The Fine Fuel Moisture Code (FFMC) from the Fire Weather Index (FWI), is one of the most used models to estimate the FDFMC. Nevertheless, studies that assess the efficiency of this model in Brazil or in low latitude regions are rare. The present study aimed to evaluate the efficiency of the FFMC in an equatorial climate area and to develop a new model capable of estimating the FDFMC with greater precision. For this purpose, 861 random samples of fine dead fuel had their moisture content determined through oven drying. The obtained values were compared with those estimated by the FFMC and correlated with meteorological parameters to build a regression model. The results obtained show that the FDFMC was overestimated by the FFMC. The independent variables with the greatest influence on the FDFMC were, in decreasing order of significance: air relative humidity, air temperature, amount of rainfall in the last 24 hours and number of days without rainfall. The developed model presented good statistical parameters (r2 = 0.86; p <0.0001; RMSE = 0.22) and can be used, in areas with similar characteristics of the study area, to estimate the daily fire risk and to determine ideal conditions for prescribed burns.

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Rossa, Carlos G., and Paulo M. Fernandes. "Fuel-related fire-behaviour relationships for mixed live and dead fuels burned in the laboratory." Canadian Journal of Forest Research 47, no. 7 (July 2017): 883–89. http://dx.doi.org/10.1139/cjfr-2016-0457.

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A laboratory experimental program addressing fire spread in fuel beds composed of dead foliage litter and vertically placed quasi-live branches, representative of many natural fuel complexes, was carried out for either still-air or wind conditions. Fuel-bed characteristics, fire spread rate, flame geometry, and fuel consumption were assessed and empirical models for estimating several parameters were developed. Weighted fuel moisture content (18%–163%) provided good estimates of fire-behaviour characteristics and accounted for most of the variation in still-air and wind-driven spread rate (0.1–1.3 m·min−1). When predicting still-air fire spread rate, fuel height was the most relevant fuel-bed structural parameter and fuel type had significant influence, whereas for wind-driven spread, the effect of foliar fuel-bed density was dominant and fuel type became irrelevant. Flame length (0.4–2.2 m) increased from still-air to wind-assisted (8 km·h−1) fire spread, but its height remained constant. The fraction of total fuel load and mean woody fuel diameter consumed by fire were reasonably predicted from weighted fuel moisture content alone, but predictions for the latter variable improved substantially by adding foliar fuel load.

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Boyle, Sean P., Rachel Dillon, Jacqueline D. Litzgus, and David Lesbarrères. "Desiccation of herpetofauna on roadway exclusion fencing." Canadian Field-Naturalist 133, no. 1 (September 20, 2019): 43–48. http://dx.doi.org/10.22621/cfn.v133i1.2076.

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Significant advances have been made to minimize the detrimental effects of roads on wildlife, but little is known about unintended negative consequences of mitigation strategies. Here, we present observations of adverse effects on herpetofauna of exclusion fencing at Presqu’ile Provincial Park, Ontario. A total of 15 individuals (one salamander, nine anurans, and five snakes) were found dead on unburied fencing, apparent victims of desiccation and/or heat exposure. Air temperatures did not differ between days when dead herpetofauna were and were not found on the fence; however, the fence surface was significantly warmer than the air. Our study shows that fence temperature and design may hinder animals escaping from the road to cooler refugia, and we discuss possible solutions.

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VYTChIKOV, Yuriy Serafimovich, and Mikhail Evgen'evich SAPAREV. "INVESTIGATION OF DEAD AIR SPACE HEAT-SHIELD PERFORMANCE WITH SCREEN HEAT INSULATION IN ENCLOSURE STRUCTURES." Urban construction and architecture 4, no. 1 (March 15, 2014): 98–102. http://dx.doi.org/10.17673/vestnik.2014.01.17.

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Calculation methods and exploratory tests of dead air space heat-shield performance are viewed. Construction solutions of slabs, coverings, outside walls heat-insulated with screen heat insulation are proposed.

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42

Forster, H. V., L. G. Pan, G. E. Bisgard, C. Flynn, and R. E. Hoffer. "Effect of reducing anatomic dead space on arterial PCO2 during CO2 inhalation." Journal of Applied Physiology 61, no. 2 (August 1, 1986): 728–33. http://dx.doi.org/10.1152/jappl.1986.61.2.728.

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Carotid body-denervated (CBD) ponies have a less than normal increase in arterial PCO2 (PaCO2) when inspired CO2 (PICO2) is increased, even when pulmonary ventilation (VE) and breathing frequency (f) are normal. We studied six tracheostomized ponies to determine whether this change 1) might be due to increased alveolar ventilation (VA) secondary to a reduction in upper airway dead space (VD) or 2) is dependent on an upper airway sensory mechanism. Three normal and three chronic CBD ponies were studied while they were breathing room air and at 14, 28, and 42 Torr PICO2. While the ponies were breathing room air, physiological VD was 483 and 255 ml during nares breathing (NBr) and tracheostomy breathing (TBr), respectively. However, at elevated PICO2, mixed expired PCO2 often exceeded PaCO2; thus we were unable to calculate physiological VD using the Bohr equation. At all PICO2 in normal ponies, PaCO2 was approximately 0.3 Torr greater during NBr than during TBr (P less than 0.05). In CBD ponies this NBr-TBr difference was only evident while breathing room air and at 28 Torr PICO2. At each elevated PICO2 during both NBr and TBr, the increase in PaCO2 above control was always less in CBD ponies than in normal ponies (P less than 0.01). The VE-PaCO2, f-PaCO2, and tidal volume-PaCO2 relationships did not differ between NBr and TBr (P greater than 0.10) nor did they differ between normal and CBD ponies (P greater than 0.10). We conclude that the attenuated increase in PaCO2 during CO2 inhalation after CBD is not due to a relative increase in VA secondary to reducing upper airway VD.(ABSTRACT TRUNCATED AT 250 WORDS)

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Tsunashima, Hitoshi, Takehiko Fujioka, and Masato Abe. "Dynamics of the Mechanical Levitation Control System for Maglev Transport Vehicle (Effect of Guide Wheel Stiffness and Dead Zone Element)." Journal of Robotics and Mechatronics 7, no. 4 (August 20, 1995): 329–35. http://dx.doi.org/10.20965/jrm.1995.p0329.

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This paper describes the effect on ride quality and levitation performance of the guide wheel stiffness and the dead zone element of the permanent magnetic suspension system with the mechanical air gap controller. A vehicle dynamic model with the guide wheel stiffness is constructed and the stability criteria for the levitation is derived. The relation between the dynamic characteristics of the vehicle and control lever ratio is analyzed. Seventeen DOF full model simulation results, where nonlinear characteristics of magnet and primary spring are also considered, indicate that the levitation performance of the vehicle is largely affected by the dead zone in the mechanical air gap controller and that the deterioration of the levitation performance can be suppressed by a large control lever ratio.

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LEE, GERALD. "“I SEE DEAD PEOPLE”: AIR-RAID PHOBIA AND BRITAIN'S BEHAVIOR IN THE MUNICH CRISIS." Security Studies 13, no. 2 (December 30, 2003): 230–72. http://dx.doi.org/10.1080/09636410490521208.

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45

Fedde, M. R., R. E. Burger, J. Geiser, R. K. Gratz, J. A. Estavillo, and P. Scheid. "Effects of altering dead space volume on respiration and air sac gases in geese." Respiration Physiology 66, no. 2 (November 1986): 109–22. http://dx.doi.org/10.1016/0034-5687(86)90065-4.

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46

Pugh, P. J. A. "Have mites (Acarina: Arachnida) colonised Antarctica and the islands of the Southern Ocean via air currents?" Polar Record 39, no. 3 (June 26, 2003): 239–44. http://dx.doi.org/10.1017/s0032247403003097.

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Mites (Acarina: Arachnida) have not colonised Antarctica and the sub-Antarctic islands by ballooning on air currents. All acarine records from Pacific and Southern Ocean aerial plankton represent dead coastal (hemi)-edaphic species or phoretics dislodged from their flying insect hosts. The few sub-Antarctic records of mites capable of ‘ballooning’ on air currents are all verified as being attributed to anthropogenic introductions.

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Lowry, T. F., H. V. Forster, M. A. Forster, C. L. Murphy, A. G. Brice, and L. G. Pan. "Effect of increased inspired CO2 on respiratory dead space in ponies." Journal of Applied Physiology 70, no. 2 (February 1, 1991): 732–39. http://dx.doi.org/10.1152/jappl.1991.70.2.732.

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The objective of the present study was to determine the effect of elevated inspired CO2 on respiratory dead space (VD) of 12 normal, 8 carotid body-denervated (CBD), 7 hilar nerve-denervated (HND), and 6 CBD+HND ponies. The Fowler technique was used to determine VD on a breath-by-breath basis while the ponies breathed room air and inspired CO2 at 3 and 6%. During room air breathing, tidal volume (VT) and VD were greater in HND ponies than in normal and CBD ponies (P less than 0.05), and VT was less and VD/VT was greater after CBD than before CBD. For all groups. VD, VT, and breathing frequency (f) increased and VD/VT decreased significantly (P less than 0.01) with increasing inspired CO2. During CO2 breathing, VT and VD were higher (P less than 0.05) in the HND ponies than in all other groups, the decrease (P less than 0.05) in VD/VT was greatest in the CBD+HND group, and f was lower in the HND and HND+CBD than in the normal and CBD ponies. In addition, when inspired CO2 was increased from 0 to 6%, the decrease in VD/VT was greater and the increase in arterial PCO2 was less (P less than 0.05) after CBD than before CBD. For 70% of the ponies in all groups, VD increased linearly with increases in VT; for most of the remainder, VD tended to plateau at higher values of VT.

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48

Bhaskaran Anangapal, Hari. "Energy and exergy analysis of fuels." International Journal of Energy Sector Management 8, no. 3 (August 26, 2014): 330–40. http://dx.doi.org/10.1108/ijesm-04-2013-0012.

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Purpose – The purpose of this study is to carry out energy and exergy analysis of fuels. Production of power and heat in industrialized countries is almost entirely based on combustion of fuels. Usually, combustion takes place in boilers or furnace; well-designed boilers have high thermal efficiencies of > 90 per cent. Even very high efficiencies, close to 100 per cent can be achieved depending on the applied fuel and boiler type. These high thermal efficiencies do suggest that combustion processes are highly optimized and do not need further improvements with regard to their thermodynamic performance. Second law (entropy or exergy) evaluations, however, shows that thermodynamic losses of boiler and furnaces are much larger than the thermal efficiencies do suggest. During combustion, air is predominantly used. When using air, the adiabatic combustion temperature depends only on the properties of fuel and air. The determining parameters for optimal fuel utilization are the fuel type, their composition and moisture content, the air temperature and air factor at combustion inlet. Design/methodology/approach – Following assumptions are made for the analysis: calculation on the basis of 100 kg of dry and ash free fuel entering the control volume; fuel entering the control volume at T0, P0 and reacting completely with air entering separately at T0, P0 to form CO2, SO2, N2 and H2O, which exit separately at T0, P0 (T0 = 298 K; P0 = 1 atm); all heat transfer occurs at temperature T0; and the chemical exergy of the ash has been ignored The availability change and the irreversibility for chemical reactions of hydrocarbon fuels were studied because fuel and dry air composed of O2 and N2 react to form products of combustion in the restricted dead state, and fuel and dry air composed of O2 and N2 react to form products of combustion which end up in the environmental (unrestricted) dead state. The difference between the above two statement, is the chemical availability of the product gases as they proceed from the restricted to the unrestricted dead state. These evaluations were made in terms of enthalpy and entropy values of the reacting species. T0 extend these concepts to the most general situation, it is considered a steady-state control volume where the fuels enters at the restricted dead state, the air (oxidant) is drawn from the environment, and the products are returned to the unrestricted dead state. Findings – It is evident from the analysis that an air factor of 1.10-1.20 is sufficient for liquid fuels, whereas solid fuels will require air factors of 1.15–1.3. When the temperatures of the products of combustion (Tp) are cooled down to that of T0, the maximum reversible work occurs. From the analysis, it is clear that the rather low combustion temperature and the need for cooling down the flue gases to extract the required heat are the main causes of the large exergy losses. The maximum second law efficiency also occurs when Tp is set equal to T0. The maximum second law efficiency per kilo mole of fuel is found to be 73 per cent, i.e. 73 per cent of the energy released by the cooling process could theoretically be converted into useful work. It is evident that reducing exergy losses of combustion is only useful if the heat transferred from the flue gas is used at high temperatures. Otherwise, a reduction of exergy loss of combustion will only increase the exergy loss of heat transfer to the power cycle or heat-absorbing process. The exergy loss of combustion can be reduced considerable by preheating combustion air. Higher preheat temperatures can be obtained by using the flue gas flow only for preheating air. The remainder of the flue gas flow can be used for heat transfer to a power cycle or heat-absorbing process. Even with very high air preheat temperatures, exergy losses of combustion are still > 20 per cent. The application of electrochemical conversion of fuel, as is realized in fuel cells, allows for much lower exergy loses for the reaction between fuel and air than thermal conversion. For industrial applications, electrochemical conversion is not yet available, but will be an interesting option for the future. Originality/value – The outcome of the study would certainly be an eye-opener for all the stakeholders in thermal power plants for considering the second law efficiency and to mitigate the irreversibilities.

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Kim, Jae-Hyun, Kyoung-Soo Cha, Sung-Woo Hwang, Soo-Gyung Lee, Min-Ro Park, Young-Doo Yoon, and Myung-Seop Lim. "Analysis of Effect of the Magnetization Distribution of Multi-Pole PM on SPMSM Performance Using Equivalent Magnetic Circuit Considering Dead Zone." Energies 14, no. 11 (June 3, 2021): 3279. http://dx.doi.org/10.3390/en14113279.

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In multi-pole permanent magnets (PMs) such a ring-type PMs, as multi-poles are magnetized in one segment, the ends of each pole are weakly magnetized, which is known as the dead zone. Thus, when analyzing characteristics of the motor with multi-pole PMs, accurate results can be obtained by considering the magnetization distribution. For this reason, this paper proposed an equivalent magnetic circuit (EMC) for external-rotor surface-mounted permanent magnet synchronous motors (SPMSMs) considering the dead zone to analyze the effects of the dead zone on the characteristics of the motor. As the magnetization in the dead zone gradually decreases toward the end of the pole, the magnetization distribution is assumed to have a trapezoidal shape. To describe the magnetization distribution, each pole was divided into several elements, and the equivalent residual magnetic flux density was applied to the elements of the dead zone. Finally, the validity of the proposed EMC was verified by comparing the back electro-motive force and air-gap magnetic flux density obtained by the EMC, finite-element analysis, and test.

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Li, Chi-Wang, Chun-Hao Chiu, Yu-Cheng Lee, Chia-Hao Chang, Yu-Hsun Lee, and Yi-Ming Chen. "Integration of ceramic membrane and compressed air-assisted solvent extraction (CASX) for metal recovery." Water Science and Technology 62, no. 6 (September 1, 2010): 1274–80. http://dx.doi.org/10.2166/wst.2010.851.

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In our previous publications, compressed air-assisted solvent extraction process (CASX) was developed and proved to be kinetically efficient process for metal removal. In the current study, CASX with a ceramic MF membrane integrated for separation of spent solvent was employed to remove and recover metal from wastewater. MF was operated either in crossflow mode or dead-end with intermittent flushing mode. Under crossflow mode, three distinct stages of flux vs. TMP (trans-membrane pressure) relationship were observed. In the first stage, flux increases with increasing TMP which is followed by the stage of stable flux with increasing TMP. After reaching a threshold TMP which is dependent of crossflow velocity, flux increases again with increasing TMP. At the last stage, solvent was pushed through membrane pores as indicated by increasing permeate COD. In dead-end with intermittent flushing mode, an intermittent flushing flow (2 min after a 10-min or a 30-min dead-end filtration) was incorporated to reduce membrane fouling by flush out MSAB accumulated on membrane surface. Effects of solvent concentration and composition were also investigated. Solvent concentrations ranging from 0.1 to 1% (w/w) have no adverse effect in terms of membrane fouling. However, solvent composition, i.e. D2EHPA/kerosene ratio, shows impact on membrane fouling. The type of metal extractants employed in CASX has significant impact on both membrane fouling and the quality of filtrate due to the differences in their viscosity and water solubility. Separation of MSAB was the limiting process controlling metal removal efficiency, and the removal efficiency of Cd(II) and Cr(VI) followed the same trend as that for COD.

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Journal articles on the topic 'Dead air'

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