Mollisols are common in South America. They cover about 8.87 × 107ha, 1.3 × 107ha and 4.3 × 106ha in Argentina, Uruguay and Southern Brazil respectively, which is 11.5% of the world total. Most of South...Mollisols are common in South America. They cover about 8.87 × 107ha, 1.3 × 107ha and 4.3 × 106ha in Argentina, Uruguay and Southern Brazil respectively, which is 11.5% of the world total. Most of South American Mollisols were developed on Pleistocene and Holocene sediments and lie within the limits of the temperate zone, though the extreme north is bordering subtropical and the extreme south is within a cold-temperate zone. All suborders of Mollisols occur in Argentina, the most extensive being Udolls followed by Ustolls, whereas only Udolls, Aquolls and Albolls occur in Uruguay. Vertisols in Uruguay have many properties similar to Mollisols, and the occurrence of Vertisols is strongly associated with Mollisols. The Pampean Mollisols are a significant component of the global breadbasket of modem times. The main Argentine crops are wheat, corn, sorghum, barmy, soybeans and sunflower, while Mollisols in Uruguay remain mostly dedicated to cattle and sheep grazing though crop production has been increasing very rapidly in the last decade. Throughout South America, research has shown that Mollisols are experiencing losses of soil organic matter and nutrients, and degradation of physical properties after long cropping periods, resulting in soil scientists calling for increased conservation practices to reduce future losses and a deterioration of soil quality, and thus a more sustainable agriculture in the region.展开更多
The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Offici...The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Officials） design method. The main objective of this study was to compare flexible pavement design using 1993 AASHTO design guide and MEPDG. Five newly built Superior PERforming Asphalt PAVEments （Superpave）, designed using the 1993 AASHTO Design Guide, were selected as test sections for the design simulation study. Deflection data were collected approximately 8 to 10 weeks after construction using FWD （falling weight deflectometer）. The FWD deflection data were used to back-calculate the pavement layer moduli using three different back-calculation programs. The existing pavement structures were analyzed for a 10-year analysis period. The maximum numbers of years the existing pavement structures will be in a serviceable condition as well as the minimum thicknesses of different layers to serve for 10-years were also determined. Effects of changing subgrade modulus, target distress, and reliability were also investigated. The MEPDG design analysis shows that the 1993 AASHTO Guide-designed flexible pavements do not show the distresses currently observed in Kansas for the 10-year design period. The MEPDG design simulation shows that the thinner the pavement sections, the higher the permanent deformation. The existing pavement structures can serve for more than 20 years as per the MEPDG design analysis if the default failure criteria and nationally-calibrated models are used.展开更多
The formation mechanism of the discharge spot at a bottom of a lead wire in a fluorescent lamp at end-of-life is investigated. When the lamp at end-of life is ignited by applying high voltage, glow-like discharge is f...The formation mechanism of the discharge spot at a bottom of a lead wire in a fluorescent lamp at end-of-life is investigated. When the lamp at end-of life is ignited by applying high voltage, glow-like discharge is formed on the surface of the lead wire. A few seconds later, a bright spot is formed at the bottom 0fthe lead-wire. Then the stem glass on which the lead-wires are mounted begins to melt. High electric field is formed between the surface of the lead-wire and the stem glass surrounding the lead wire. Then discharge spot will be formed at the contact portion of the lead wire to the stem glass by this high electric field. To prevent discharge spot formation at the bottom of the lead wire, the metal ring is set to encircle the lead wire and is connected to the lead wire potential through a resistor. By this configuration, discharge spot formation is effectively suppressed. The mechanism for preventing hot discharge spot formation by the metal ring is discussed.展开更多
In coping with the global financial crisis, all levels of the Chinese government and foreign trade firms have not only created new practices but have also changed their goal from transforming the growth pattern of for...In coping with the global financial crisis, all levels of the Chinese government and foreign trade firms have not only created new practices but have also changed their goal from transforming the growth pattern of foreign trade to transforming the development pattern of joreign trade. China＇s experience shows that economic instruments such as Net Barter Terms of Trade （NBTT） and the smile curve theory have limitations when it comes to interpreting foreign trade. If used improperly, scientific theories often lead to.fallacies. Transjbrming the development pattern of China＇s .foreign trade requires the following changes： national income distribution, foreign trade competition, market exploration, and resource utilization. We advise that competent authorities create a reasonable and operational system of assessment indicators.展开更多
On the basis of studying the standard TCP retransmission mechanism, this paper proposes a method to adopt the theory of adaptive filtering in the field for the estimation of round trip time （RTT）. Then this method i...On the basis of studying the standard TCP retransmission mechanism, this paper proposes a method to adopt the theory of adaptive filtering in the field for the estimation of round trip time （RTT）. Then this method is embedded in TCP for estimation of RTT, and defined as RTT-AF TCP. In the schemes with Only-TCP flow and with TCP and UDP flow fighting for the link, the experiment results were made and analyzed by using the standard TCP and the RTT-AF TCP. The experimental results show higher throughput and lower loss rate of packets by using RTT-AF TCP for data transmission, and achieve excellent effect.展开更多
In the field of aerospace, minimum and seal of equipments cause the increase in the thermal loading sharply. Due to the lack of driving force, the performance of conventional condenser deteriorates greatly under the s...In the field of aerospace, minimum and seal of equipments cause the increase in the thermal loading sharply. Due to the lack of driving force, the performance of conventional condenser deteriorates greatly under the small gravity environment, which leads to reduction in the service life of equipments. In this study, a passive condenser, developed on basis of the phase separation concept,is utilized to improve the performance of the condensation heat transfer under the small gravity environment. As a result of the limitation of experiments, the mechanisms of heat transfer enhancement of the phase separation condenser tube are revealed through numerical simulation based on the volume-of-fluid(VOF) method. The following conclusions could be obtained:(1) A novel phase distribution of ‘‘gas near the tube wall and liquid in the tube core'' is formed. The thin liquid film is indeed created after the flow pattern modulation by inserting mesh cylinder.(2)The condensation quantity for single bubble in the annular region increases about 16 times greater than that in the bare tube region in the case of Jl= 0.0574 m/s and Jg= 0.0229 m/s.(3) Gas volume fraction affects the parameters of liquid film thickness, bubble length and liquid bridge length. The increase in the gas volume fraction results in the decrease in the evaluation index from21.56 to 12.82. The evaluation index is defined as the ratio of the condensation quantities per unit tube length of the annular region and the bare tube region.展开更多
基金Under the auspices of Bureau of International Cooperation Grant,Chinese Academy of Sciences(No.GJHZ0949)Harbin Bureau of Science and Technology for Outstanding Scientist(No.2010RFXYN044)+3 种基金National University of Mar del Plata(No.AGR-336/10)National Institute of Agricultural Technology(No.AERN-022411)National Agency for the Promotion of Science and Technology(No.PAE-PICT2007n°18)Department of Renewable Natural Resourses,Ministry of Livestock,Agriculture and Fisheries of Uruguay(No.TCP/URU/3301)
文摘Mollisols are common in South America. They cover about 8.87 × 107ha, 1.3 × 107ha and 4.3 × 106ha in Argentina, Uruguay and Southern Brazil respectively, which is 11.5% of the world total. Most of South American Mollisols were developed on Pleistocene and Holocene sediments and lie within the limits of the temperate zone, though the extreme north is bordering subtropical and the extreme south is within a cold-temperate zone. All suborders of Mollisols occur in Argentina, the most extensive being Udolls followed by Ustolls, whereas only Udolls, Aquolls and Albolls occur in Uruguay. Vertisols in Uruguay have many properties similar to Mollisols, and the occurrence of Vertisols is strongly associated with Mollisols. The Pampean Mollisols are a significant component of the global breadbasket of modem times. The main Argentine crops are wheat, corn, sorghum, barmy, soybeans and sunflower, while Mollisols in Uruguay remain mostly dedicated to cattle and sheep grazing though crop production has been increasing very rapidly in the last decade. Throughout South America, research has shown that Mollisols are experiencing losses of soil organic matter and nutrients, and degradation of physical properties after long cropping periods, resulting in soil scientists calling for increased conservation practices to reduce future losses and a deterioration of soil quality, and thus a more sustainable agriculture in the region.
文摘The KDOT （Kansas Department of Transportation） is currently adopting MEPDG （mechanistic-empirical pavement design guide） to replace the 1993 AASHTO （American Association of State Highway and Transportation Officials） design method. The main objective of this study was to compare flexible pavement design using 1993 AASHTO design guide and MEPDG. Five newly built Superior PERforming Asphalt PAVEments （Superpave）, designed using the 1993 AASHTO Design Guide, were selected as test sections for the design simulation study. Deflection data were collected approximately 8 to 10 weeks after construction using FWD （falling weight deflectometer）. The FWD deflection data were used to back-calculate the pavement layer moduli using three different back-calculation programs. The existing pavement structures were analyzed for a 10-year analysis period. The maximum numbers of years the existing pavement structures will be in a serviceable condition as well as the minimum thicknesses of different layers to serve for 10-years were also determined. Effects of changing subgrade modulus, target distress, and reliability were also investigated. The MEPDG design analysis shows that the 1993 AASHTO Guide-designed flexible pavements do not show the distresses currently observed in Kansas for the 10-year design period. The MEPDG design simulation shows that the thinner the pavement sections, the higher the permanent deformation. The existing pavement structures can serve for more than 20 years as per the MEPDG design analysis if the default failure criteria and nationally-calibrated models are used.
文摘The formation mechanism of the discharge spot at a bottom of a lead wire in a fluorescent lamp at end-of-life is investigated. When the lamp at end-of life is ignited by applying high voltage, glow-like discharge is formed on the surface of the lead wire. A few seconds later, a bright spot is formed at the bottom 0fthe lead-wire. Then the stem glass on which the lead-wires are mounted begins to melt. High electric field is formed between the surface of the lead-wire and the stem glass surrounding the lead wire. Then discharge spot will be formed at the contact portion of the lead wire to the stem glass by this high electric field. To prevent discharge spot formation at the bottom of the lead wire, the metal ring is set to encircle the lead wire and is connected to the lead wire potential through a resistor. By this configuration, discharge spot formation is effectively suppressed. The mechanism for preventing hot discharge spot formation by the metal ring is discussed.
文摘In coping with the global financial crisis, all levels of the Chinese government and foreign trade firms have not only created new practices but have also changed their goal from transforming the growth pattern of foreign trade to transforming the development pattern of joreign trade. China＇s experience shows that economic instruments such as Net Barter Terms of Trade （NBTT） and the smile curve theory have limitations when it comes to interpreting foreign trade. If used improperly, scientific theories often lead to.fallacies. Transjbrming the development pattern of China＇s .foreign trade requires the following changes： national income distribution, foreign trade competition, market exploration, and resource utilization. We advise that competent authorities create a reasonable and operational system of assessment indicators.
基金Supported by the National Natural Science Foundation of China （No. 60775058） the Key Project of Ministry of Education of China （No. 107028）.
文摘On the basis of studying the standard TCP retransmission mechanism, this paper proposes a method to adopt the theory of adaptive filtering in the field for the estimation of round trip time （RTT）. Then this method is embedded in TCP for estimation of RTT, and defined as RTT-AF TCP. In the schemes with Only-TCP flow and with TCP and UDP flow fighting for the link, the experiment results were made and analyzed by using the standard TCP and the RTT-AF TCP. The experimental results show higher throughput and lower loss rate of packets by using RTT-AF TCP for data transmission, and achieve excellent effect.
基金supported by the National Natural Science Foundation of China(51476054 and 51506026)the Program for New Century Excellent Talents in University(NCET-13-0792)
文摘In the field of aerospace, minimum and seal of equipments cause the increase in the thermal loading sharply. Due to the lack of driving force, the performance of conventional condenser deteriorates greatly under the small gravity environment, which leads to reduction in the service life of equipments. In this study, a passive condenser, developed on basis of the phase separation concept,is utilized to improve the performance of the condensation heat transfer under the small gravity environment. As a result of the limitation of experiments, the mechanisms of heat transfer enhancement of the phase separation condenser tube are revealed through numerical simulation based on the volume-of-fluid(VOF) method. The following conclusions could be obtained:(1) A novel phase distribution of ‘‘gas near the tube wall and liquid in the tube core'' is formed. The thin liquid film is indeed created after the flow pattern modulation by inserting mesh cylinder.(2)The condensation quantity for single bubble in the annular region increases about 16 times greater than that in the bare tube region in the case of Jl= 0.0574 m/s and Jg= 0.0229 m/s.(3) Gas volume fraction affects the parameters of liquid film thickness, bubble length and liquid bridge length. The increase in the gas volume fraction results in the decrease in the evaluation index from21.56 to 12.82. The evaluation index is defined as the ratio of the condensation quantities per unit tube length of the annular region and the bare tube region.
