AIM：To assess the pattern of ocular manifestation and associated factors among human immunodeficiency virus（HIV）/acquired immunodeficiency syndrome（AIDS） patients on highly active antiretroviral therapy（HAART） ...AIM：To assess the pattern of ocular manifestation and associated factors among human immunodeficiency virus（HIV）/acquired immunodeficiency syndrome（AIDS） patients on highly active antiretroviral therapy（HAART） at Hawassa University Referral Hospital, Southern Ethiopia. METHODS：A cross sectional study was conducted from January 2014 to April 2015. After obtaining informed written consent, 240 adult HIV/AIDS patients on HAART were randomly selected regardless of their ophthalmic symptoms, WHO status or CD4 count. Data were collected using structured questionnaires and ophthalmologic clinical examination. Data were entered and analyzed using SPSS version 20.0 software. RESULTS：The mean duration of HAART was 62.5mo. The prevalence of HIV related ocular manifestation was 14.2%. Seborrheic blepharitis（5%） was the most common ocular manifestation, followed by squamoid conjunctival growth（3.8%）. The rate of ocular manifestation was significantly higher among study participants who had CD4＋ count 〈200 cells/μL（AOR=3.83; 95%CI：1.315-11.153）, low duration of HAART（AOR=3.0; 95%CI：1.305-6.891） and who had primary school education [odds ratio（OR） =2.8; 95%CI：1.105-7.099]. Prevalence of visual impairment and blindness was 10.9% and 5.8%, respectively.CONCLUSION：HAART may be the reason for the decline in the prevalence of ocular manifestation in HIV/AIDS patients in the study area. Ophthalmologic screening of HIV/AIDS patients, especially those with CD4 counts of 〈200/μL cells and in the first five years of HAART followup is recommended to reduce visual impairment and/or blindness.展开更多
Ethiopian coffee price is highly fluctuated and has significant effect on the economy of the country. Conducting a research on forecasting coffee price has theoretical and practical importance.This study aims at forec...Ethiopian coffee price is highly fluctuated and has significant effect on the economy of the country. Conducting a research on forecasting coffee price has theoretical and practical importance.This study aims at forecasting the coffee price in Ethiopia. We used daily closed price data of Ethiopian coffee recorded in the period 25 June 2008 to 5 January 2017 obtained from Ethiopia commodity exchange（ECX） market to analyse coffee prices fluctuation. Here, the nature of coffee price is non-stationary and we apply the Kalman filtering algorithm on a single linear state space model to estimate and forecast an optimal value of coffee price. The performance of the algorithm for estimating and forecasting the coffee price is evaluated by using root mean square error（RMSE）. Based on the linear state space model and the Kalman filtering algorithm, the root mean square error（RMSE） is 0.000016375, which is small enough, and it indicates that the algorithm performs well.展开更多
This study aims to assess the impact of monospecific Tectona grandis forest plantation on the soil mite abundance and diversity. To achieve these objectives, two sites situated in Ivory Coast were investigated. The fi...This study aims to assess the impact of monospecific Tectona grandis forest plantation on the soil mite abundance and diversity. To achieve these objectives, two sites situated in Ivory Coast were investigated. The first, a primary forest was characterized by a very weak human activities whereas the second, a teak plantation was characterized by a high disturbance performed during the planting. After extracting, sorted and description, 116 mite species were described in the two sites. Mite densities were lower in teak plantation and also higher in the litter and decreased to the depth in both sites. Species richness re- corded in teak plantation （52 species） was significantly lower compared to primary forest （98 species）. The same trend was ob- served for Oribatida but not for Gamasida. The lower Oribatida （5 vs. 17） and higher Oribatida （24 vs. 41） were recorded respec- tively in teak plantation and primary forest. Mite Shannon index and evenness were significantly different between sites. High Jaccard index values and the appearance of exclusive species in both habitats showed that the sites are very distinct. Total number of species recorded corresponded to 58%-63% of the total number of species estimated by ACE and Chao 1＆2 estimators, indi- cating that the sampling effort was not sufficient. Mite abundance and diversity varied depending on the characteristics of habi- tats. Chemical element （Corn, Ctot, Ntot, and SOM） values were lower in teak plantation （disturbed habitat） and significantly dif- ferent to primary forest in the topsoil. Apart from litter height, soil depth, pH and C/N ratio, others variables were strongly corre- lated to mite abundance and diversity [Current Zoology 59 （5）： 633-643, 2013].展开更多
It is well known that no criterion about seismic design for risers is available, and relevant research has not been reported. A comprehensive study of riser dynamics during earthquakes is performed in this paper. A dy...It is well known that no criterion about seismic design for risers is available, and relevant research has not been reported. A comprehensive study of riser dynamics during earthquakes is performed in this paper. A dynamic model for seismic analysis of risers is developed in accordance with the working environment of the risers and the influence of inertia force of the pipelines. The dynamic equations for the developed model are derived and resolved on the basis of the energy theory of beams. Numerical simulation for an engineering project in the Bohai Oil Field, China shows that the fundamental frequency of the riser plays the major role in the seismic responses, and for platforms in shallow water in Bohai Bay, the risers demonstrate a much lower stress response due to prominent differences between the riser frequency and the earthquake wave frequency. The presented model and its corresponding method for seismic analysis are practical and important for riser design resistant to earthquake waves.展开更多
The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire sola...The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire solar system. In a majority of asteroids, the disk-integrated photometry measurement constitutes the primary source of the above knowledge. In the present paper, newly observed photometric data and existing data on（585） Bilkis are analyzed based on a Lommel-Seeliger ellipsoid model. With a Markov chain Monte Carlo（MCMC） method, we have determined the spin parameters（period, pole orientation）and shape（b/a, c/a） of（585） Bilkis and their uncertainties. As a result, we obtained a rotational period of 8.5738209 h with an uncertainty of 9×10^-7h, and derived a pole of（136.46°, 29.0°） in the ecliptic frame of J2000.0 with uncertainties of 0.67°and 1.1°in longitude and latitude respectively. We also derived triaxial ratios b/a and c/a of（585） Bilkis as 0.736 and 0.70 with uncertainties of 0.003 and 0.03 respectively.展开更多
Our knowledge of the solar system encourages us to believe that we might expect exomoons to be present around some known exoplanets. With present hardware and existing optical astronomy methods, we do not expect to be...Our knowledge of the solar system encourages us to believe that we might expect exomoons to be present around some known exoplanets. With present hardware and existing optical astronomy methods, we do not expect to be able to find exomoons for at least 10 years, and even then, it will be a hard task to detect them. Using data from the Exoplanet Orbit Database（EOD） we find stars with Jovian exoplanets within 50 light years. Most of them will be fully accessible by the new radio telescope, the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, under construction which is now in the test phase. We suggest radio astronomy based methods to search for possible exomoons around two exoplanets.展开更多
A single set of 5 bird tracks was discovered in the Tianjialou Formation (Barremian-Albian) of Junan County, Shandong Province, China. After careful study we infer that it is a new type of bird tracks, and a new ichno...A single set of 5 bird tracks was discovered in the Tianjialou Formation (Barremian-Albian) of Junan County, Shandong Province, China. After careful study we infer that it is a new type of bird tracks, and a new ichnoge- nus was erected and the name Shandongornipes was given. The characteristics of the new bird track are as follows: Moderately large tetradactyl footprints with well-developed hallux impression. Track width (about 5.8 cm) almost equal to track length (excluding hallux); total length of track (in- cluding hallux) 8.7 cm. The digit impressions are slender, with distal ends showing long sharp claw marks. Hallux pos- teriorly-directed, and hallux impressions well-developed. Digits II, III and IV point anteriorly, exhibiting mesaxonic asymmetry: divarication angle between II and III much lar- ger than that of III and IV, the former ranging from 91° to 118°, and the latter less than 30°. Divarication between digits II and IV ranging from 128° to 142°. Without web structures. Digital pads recognizable, usually at least three in digits III and IV, but sometimes only two due to preservation. The trackway shows slight positive (inward) rotation of feet. The bird tracks occur in association with abundant dinosaur tracks, and are believed to have formed in flood plain environments.展开更多
A fourth-order relaxation scheme is derived and applied to hyperbolic systems of conservation laws in one and two space dimensions. The scheme is based on a fourthorder central weighted essentially nonoscillatory （CW...A fourth-order relaxation scheme is derived and applied to hyperbolic systems of conservation laws in one and two space dimensions. The scheme is based on a fourthorder central weighted essentially nonoscillatory （CWENO） reconstruction for one-dimensional cases, which is generalized to two-dimensional cases by the dimension-by-dimension approach. The large stability domain Runge-Kutta-type solver ROCK4 is used for time integration. The resulting method requires neither the use of Riemann solvers nor the computation of Jacobians and therefore it enjoys the main advantage of the relaxation schemes. The high accuracy and high-resolution properties of the present method are demonstrated in one- and two-dimensional numerical experiments.展开更多
Thermodynamic processes of a system involving a floe and a small lead in the central Arctic were investigated during the ice-camp period of the third Chinese National Arctic Research Expedition from 20 to 28 August, 2...Thermodynamic processes of a system involving a floe and a small lead in the central Arctic were investigated during the ice-camp period of the third Chinese National Arctic Research Expedition from 20 to 28 August, 2008. The measurements included surface air temperatures above the floe, spectral albedo of the lead, seawater temperatures in the lead and under the ice cover, and the lateral and bottom mass balance of the floe. The surface air temperature at 1.15 m remained below 0~Cthroughout the observation period and sea ice had commenced its annual cycle of growth in response to autumn cooling during the study. The surface of the lead was frozen by 23 August, after which the spectral albedo of the thin-ice-covered lead in the band of 320-950 nm was 0.46 -0.03, the seawater temperatures both in the lead and under the ice cover, as well as the vertical seawater-temperature gradient in the lead decreased gradually, and the oceanic heat under the ice was maintained at a low level approaching 0 W/m2. By the end of the measurement, the thickness of the investigated floe had reached its annual minimum, while the lateral of the floe was still in the melting phase, with a mean melting rate of 1.0±0.3 cm/d during the measurement, responding to an equivalent latent heat flux of 21 ±6 W/m2. The lateral melting of the floe had made a more significant contribution to the sea-ice mass balance than the surface and bottom melting in the end of August.展开更多
The small angle X-ray scattering of organically modified MSU-X silica prepared by co-condensation of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) show negative deviation from Debye’s theory due to the ...The small angle X-ray scattering of organically modified MSU-X silica prepared by co-condensation of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) show negative deviation from Debye’s theory due to the existence of the organic interface layer. By exerting correction of the scattering negative deviation, Debye relation may be recovered, and the average wall thickness of the material may be evaluated.展开更多
We describe the general structure of the well known S255IR high mass star forming region, as revealed by our recent ALMA observations. The data indicate a physical relation exists between the major clumps SMA1 and SMA...We describe the general structure of the well known S255IR high mass star forming region, as revealed by our recent ALMA observations. The data indicate a physical relation exists between the major clumps SMA1 and SMA2. The driving source of the extended high velocity, well collimated bipolar outflow, is not the most pronounced disk-like SMA1 clump harboring a 20M⊙ young star （S255 NIRS3）, as was assumed earlier. Apparently, it is the less evolved SMA2 clump, which drives the outflow and contains a compact rotating structure （probably a disk）. At the same time, the SMA 1 clump drives another outflow, with a larger opening angle. The molecular line data do not show an outflow from the SMA3 clump （NIRS 1）, which was suggested by IR studies of this region.展开更多
The boiling behavior of the liquid nitrogen (LN2) under the transient high heat flux urgently needs to be researched systematically. In this paper, the high power short pulse duration laser was used to heat the satura...The boiling behavior of the liquid nitrogen (LN2) under the transient high heat flux urgently needs to be researched systematically. In this paper, the high power short pulse duration laser was used to heat the saturated LN2 rapidly, and the high-speed photography aided by the spark light system was employed to take series of photos which displayed the process of LN2's boiling behavior under such conditions. Also, a special temperature measuring system was applied to record the temperature variation of the heating surface. The experiments indicated that an explosive boiling happened within LN2 by the laser heating, and a conventional boiling followed up after the newly-defined changeover time. By analyzing the temperature variation of the heating surface, it is found that the latent heat released by the crack of the bubbles in the bubble cluster induced by the explosive boiling is an important factor that greatly influences the boiling heat transfer mechanism.展开更多
A 3 kW radio frequency (RF) magnetron-sputtering unit was used to producezirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlYbond coat layer by cathodic arc deposition. The ...A 3 kW radio frequency (RF) magnetron-sputtering unit was used to producezirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlYbond coat layer by cathodic arc deposition. The NiCrAlY coating surface was shot-peened, and theresidual stress in the bond coat layer and the effects of heat treatment on the residual stress arepresented. After shot peening porosities and microgaps disappear in the NiCrAlY bond coat, the wholedepth profile is residual compressive stress. Coarseness tests show that the roughness value (Rz)decreases from 16.4 to 3.3 mu m. The microstructure and phase composition of the coatings wereinvestigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results showthat the/ NiCrAlY bond coat is composed of gamma and Cr phases, and the A1_2O_3 scales are formednear the interface between the ZrO_2 ceramic layer and the NiCrAlY bond coat. No degradationoccurred to RF sputtered ceramic coatings after oxidating at 1150 deg C for 100 h, heating at 1150deg C for 5 min and then air-cooling for 500 thermal cycles.展开更多
文摘AIM：To assess the pattern of ocular manifestation and associated factors among human immunodeficiency virus（HIV）/acquired immunodeficiency syndrome（AIDS） patients on highly active antiretroviral therapy（HAART） at Hawassa University Referral Hospital, Southern Ethiopia. METHODS：A cross sectional study was conducted from January 2014 to April 2015. After obtaining informed written consent, 240 adult HIV/AIDS patients on HAART were randomly selected regardless of their ophthalmic symptoms, WHO status or CD4 count. Data were collected using structured questionnaires and ophthalmologic clinical examination. Data were entered and analyzed using SPSS version 20.0 software. RESULTS：The mean duration of HAART was 62.5mo. The prevalence of HIV related ocular manifestation was 14.2%. Seborrheic blepharitis（5%） was the most common ocular manifestation, followed by squamoid conjunctival growth（3.8%）. The rate of ocular manifestation was significantly higher among study participants who had CD4＋ count 〈200 cells/μL（AOR=3.83; 95%CI：1.315-11.153）, low duration of HAART（AOR=3.0; 95%CI：1.305-6.891） and who had primary school education [odds ratio（OR） =2.8; 95%CI：1.105-7.099]. Prevalence of visual impairment and blindness was 10.9% and 5.8%, respectively.CONCLUSION：HAART may be the reason for the decline in the prevalence of ocular manifestation in HIV/AIDS patients in the study area. Ophthalmologic screening of HIV/AIDS patients, especially those with CD4 counts of 〈200/μL cells and in the first five years of HAART followup is recommended to reduce visual impairment and/or blindness.
文摘Ethiopian coffee price is highly fluctuated and has significant effect on the economy of the country. Conducting a research on forecasting coffee price has theoretical and practical importance.This study aims at forecasting the coffee price in Ethiopia. We used daily closed price data of Ethiopian coffee recorded in the period 25 June 2008 to 5 January 2017 obtained from Ethiopia commodity exchange（ECX） market to analyse coffee prices fluctuation. Here, the nature of coffee price is non-stationary and we apply the Kalman filtering algorithm on a single linear state space model to estimate and forecast an optimal value of coffee price. The performance of the algorithm for estimating and forecasting the coffee price is evaluated by using root mean square error（RMSE）. Based on the linear state space model and the Kalman filtering algorithm, the root mean square error（RMSE） is 0.000016375, which is small enough, and it indicates that the algorithm performs well.
文摘This study aims to assess the impact of monospecific Tectona grandis forest plantation on the soil mite abundance and diversity. To achieve these objectives, two sites situated in Ivory Coast were investigated. The first, a primary forest was characterized by a very weak human activities whereas the second, a teak plantation was characterized by a high disturbance performed during the planting. After extracting, sorted and description, 116 mite species were described in the two sites. Mite densities were lower in teak plantation and also higher in the litter and decreased to the depth in both sites. Species richness re- corded in teak plantation （52 species） was significantly lower compared to primary forest （98 species）. The same trend was ob- served for Oribatida but not for Gamasida. The lower Oribatida （5 vs. 17） and higher Oribatida （24 vs. 41） were recorded respec- tively in teak plantation and primary forest. Mite Shannon index and evenness were significantly different between sites. High Jaccard index values and the appearance of exclusive species in both habitats showed that the sites are very distinct. Total number of species recorded corresponded to 58%-63% of the total number of species estimated by ACE and Chao 1＆2 estimators, indi- cating that the sampling effort was not sufficient. Mite abundance and diversity varied depending on the characteristics of habi- tats. Chemical element （Corn, Ctot, Ntot, and SOM） values were lower in teak plantation （disturbed habitat） and significantly dif- ferent to primary forest in the topsoil. Apart from litter height, soil depth, pH and C/N ratio, others variables were strongly corre- lated to mite abundance and diversity [Current Zoology 59 （5）： 633-643, 2013].
基金supported by the National Natural Science Foundation of China (granted number 50979113)funded by the National 863 Program of China (granted number 2006AA09A105)
文摘It is well known that no criterion about seismic design for risers is available, and relevant research has not been reported. A comprehensive study of riser dynamics during earthquakes is performed in this paper. A dynamic model for seismic analysis of risers is developed in accordance with the working environment of the risers and the influence of inertia force of the pipelines. The dynamic equations for the developed model are derived and resolved on the basis of the energy theory of beams. Numerical simulation for an engineering project in the Bohai Oil Field, China shows that the fundamental frequency of the riser plays the major role in the seismic responses, and for platforms in shallow water in Bohai Bay, the risers demonstrate a much lower stress response due to prominent differences between the riser frequency and the earthquake wave frequency. The presented model and its corresponding method for seismic analysis are practical and important for riser design resistant to earthquake waves.
基金funded by the National Natural Science Foundation of China(Grant Nos.11073051 and 11473066)supported,in part,by the Academy of Finland(Project 1257966)
文摘The basic physical parameters of asteroids, such as spin parameters, shape and scattering parameters, can provide us with information on the formation and evolution of both the asteroids themselves and the entire solar system. In a majority of asteroids, the disk-integrated photometry measurement constitutes the primary source of the above knowledge. In the present paper, newly observed photometric data and existing data on（585） Bilkis are analyzed based on a Lommel-Seeliger ellipsoid model. With a Markov chain Monte Carlo（MCMC） method, we have determined the spin parameters（period, pole orientation）and shape（b/a, c/a） of（585） Bilkis and their uncertainties. As a result, we obtained a rotational period of 8.5738209 h with an uncertainty of 9×10^-7h, and derived a pole of（136.46°, 29.0°） in the ecliptic frame of J2000.0 with uncertainties of 0.67°and 1.1°in longitude and latitude respectively. We also derived triaxial ratios b/a and c/a of（585） Bilkis as 0.736 and 0.70 with uncertainties of 0.003 and 0.03 respectively.
基金supported by the Ministry of Education and Science of the Republic of Serbia through the project:176021‘Visible and Invisible Matter in Nearby Galaxies:Theory and Observations’
文摘Our knowledge of the solar system encourages us to believe that we might expect exomoons to be present around some known exoplanets. With present hardware and existing optical astronomy methods, we do not expect to be able to find exomoons for at least 10 years, and even then, it will be a hard task to detect them. Using data from the Exoplanet Orbit Database（EOD） we find stars with Jovian exoplanets within 50 light years. Most of them will be fully accessible by the new radio telescope, the Five-hundred-meter Aperture Spherical radio Telescope（FAST）, under construction which is now in the test phase. We suggest radio astronomy based methods to search for possible exomoons around two exoplanets.
文摘A single set of 5 bird tracks was discovered in the Tianjialou Formation (Barremian-Albian) of Junan County, Shandong Province, China. After careful study we infer that it is a new type of bird tracks, and a new ichnoge- nus was erected and the name Shandongornipes was given. The characteristics of the new bird track are as follows: Moderately large tetradactyl footprints with well-developed hallux impression. Track width (about 5.8 cm) almost equal to track length (excluding hallux); total length of track (in- cluding hallux) 8.7 cm. The digit impressions are slender, with distal ends showing long sharp claw marks. Hallux pos- teriorly-directed, and hallux impressions well-developed. Digits II, III and IV point anteriorly, exhibiting mesaxonic asymmetry: divarication angle between II and III much lar- ger than that of III and IV, the former ranging from 91° to 118°, and the latter less than 30°. Divarication between digits II and IV ranging from 128° to 142°. Without web structures. Digital pads recognizable, usually at least three in digits III and IV, but sometimes only two due to preservation. The trackway shows slight positive (inward) rotation of feet. The bird tracks occur in association with abundant dinosaur tracks, and are believed to have formed in flood plain environments.
基金the National Natural Science Foundation of China (60134010)The English text was polished by Yunming Chen.
文摘A fourth-order relaxation scheme is derived and applied to hyperbolic systems of conservation laws in one and two space dimensions. The scheme is based on a fourthorder central weighted essentially nonoscillatory （CWENO） reconstruction for one-dimensional cases, which is generalized to two-dimensional cases by the dimension-by-dimension approach. The large stability domain Runge-Kutta-type solver ROCK4 is used for time integration. The resulting method requires neither the use of Riemann solvers nor the computation of Jacobians and therefore it enjoys the main advantage of the relaxation schemes. The high accuracy and high-resolution properties of the present method are demonstrated in one- and two-dimensional numerical experiments.
基金supported by the National Natural Science Foundation of China (Grant no. 40930848)the Norwegian Research Council (AMORA, 193592/S30)+1 种基金the China Postdoctoral Science Foundation (Grant no. 20100470400)the International Cooperation Project of the Chinese Arctic and Antarctic Administration, SOA (Grant no. IC2010007)
文摘Thermodynamic processes of a system involving a floe and a small lead in the central Arctic were investigated during the ice-camp period of the third Chinese National Arctic Research Expedition from 20 to 28 August, 2008. The measurements included surface air temperatures above the floe, spectral albedo of the lead, seawater temperatures in the lead and under the ice cover, and the lateral and bottom mass balance of the floe. The surface air temperature at 1.15 m remained below 0~Cthroughout the observation period and sea ice had commenced its annual cycle of growth in response to autumn cooling during the study. The surface of the lead was frozen by 23 August, after which the spectral albedo of the thin-ice-covered lead in the band of 320-950 nm was 0.46 -0.03, the seawater temperatures both in the lead and under the ice cover, as well as the vertical seawater-temperature gradient in the lead decreased gradually, and the oceanic heat under the ice was maintained at a low level approaching 0 W/m2. By the end of the measurement, the thickness of the investigated floe had reached its annual minimum, while the lateral of the floe was still in the melting phase, with a mean melting rate of 1.0±0.3 cm/d during the measurement, responding to an equivalent latent heat flux of 21 ±6 W/m2. The lateral melting of the floe had made a more significant contribution to the sea-ice mass balance than the surface and bottom melting in the end of August.
文摘The small angle X-ray scattering of organically modified MSU-X silica prepared by co-condensation of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) show negative deviation from Debye’s theory due to the existence of the organic interface layer. By exerting correction of the scattering negative deviation, Debye relation may be recovered, and the average wall thickness of the material may be evaluated.
基金supported by the Russian Foundation for Basic Research(Grant No.15–02–06098)during the preparation of the observations and initial data reductionthe Russian Science Foundation(Grant No.17–12–01256)during the spectral data analysissupport from the European Research Council under the Horizon 2020 Framework Program via the ERC Consolidator Grant CSF-648505
文摘We describe the general structure of the well known S255IR high mass star forming region, as revealed by our recent ALMA observations. The data indicate a physical relation exists between the major clumps SMA1 and SMA2. The driving source of the extended high velocity, well collimated bipolar outflow, is not the most pronounced disk-like SMA1 clump harboring a 20M⊙ young star （S255 NIRS3）, as was assumed earlier. Apparently, it is the less evolved SMA2 clump, which drives the outflow and contains a compact rotating structure （probably a disk）. At the same time, the SMA 1 clump drives another outflow, with a larger opening angle. The molecular line data do not show an outflow from the SMA3 clump （NIRS 1）, which was suggested by IR studies of this region.
文摘The boiling behavior of the liquid nitrogen (LN2) under the transient high heat flux urgently needs to be researched systematically. In this paper, the high power short pulse duration laser was used to heat the saturated LN2 rapidly, and the high-speed photography aided by the spark light system was employed to take series of photos which displayed the process of LN2's boiling behavior under such conditions. Also, a special temperature measuring system was applied to record the temperature variation of the heating surface. The experiments indicated that an explosive boiling happened within LN2 by the laser heating, and a conventional boiling followed up after the newly-defined changeover time. By analyzing the temperature variation of the heating surface, it is found that the latent heat released by the crack of the bubbles in the bubble cluster induced by the explosive boiling is an important factor that greatly influences the boiling heat transfer mechanism.
文摘A 3 kW radio frequency (RF) magnetron-sputtering unit was used to producezirconia ceramic coatings on hollow turbine blades and vanes, which had been deposited a NiCrAlYbond coat layer by cathodic arc deposition. The NiCrAlY coating surface was shot-peened, and theresidual stress in the bond coat layer and the effects of heat treatment on the residual stress arepresented. After shot peening porosities and microgaps disappear in the NiCrAlY bond coat, the wholedepth profile is residual compressive stress. Coarseness tests show that the roughness value (Rz)decreases from 16.4 to 3.3 mu m. The microstructure and phase composition of the coatings wereinvestigated using electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results showthat the/ NiCrAlY bond coat is composed of gamma and Cr phases, and the A1_2O_3 scales are formednear the interface between the ZrO_2 ceramic layer and the NiCrAlY bond coat. No degradationoccurred to RF sputtered ceramic coatings after oxidating at 1150 deg C for 100 h, heating at 1150deg C for 5 min and then air-cooling for 500 thermal cycles.
