Intertidal macroalgae experience continual alternation of photosynthesis between aquatic state at high tide and aerial state at low tide. The comparative photosynthetic responses to inorganic carbon were investigated...Intertidal macroalgae experience continual alternation of photosynthesis between aquatic state at high tide and aerial state at low tide. The comparative photosynthetic responses to inorganic carbon were investigated in the common intertidal macroalga Ulva lactuca L. along the coast of Shantou between aquatic and aerial state. The inorganic carbon dissolved in seawater at present could fully (at 10 ℃ or 20 ℃) or nearly (at 30 ℃) saturate the aquatic photosynthesis of U. lactuca . However, the aerial photosynthesis was limited by current ambient atmospheric CO 2 level, and such a limitation was more severe at higher temperature (20-30 ℃) than at lower temperature (10 ℃). The carbon_saturated maximal photosynthesis of U. lactuca under aerial state was much greater than that under aquatic state at 10 ℃ and 20 ℃, while the maximal photosynthesis under both states was similar at 30 ℃. The aerial values of K m (CO 2) for photosynthesis were higher than the aquatic values. On the contrary, the values of apparent photosynthetic CO 2 conductance under aerial state were considerably lower than that under aquatic state. It was concluded that the increase of atmospheric CO 2 would enhance the primary productivity of U. lactuca through stimulating the photosynthesis under aerial state during low tide.展开更多
This paper proposes a new channel access algorithm based on channel occupancy time （COT） fairness to guarantee fairness and improve the aggregate throughput of 802.11b multi-rate WLANs. In the algorithm, the COT is ...This paper proposes a new channel access algorithm based on channel occupancy time （COT） fairness to guarantee fairness and improve the aggregate throughput of 802.11b multi-rate WLANs. In the algorithm, the COT is used as fairness index to analyze the fairness of WLANs instead of the channel access probability （CAP） used in the distributed coordination function （DCF）. The standard COT is given by access point （AP） and broadcasted to all wireless stations. The AP and wireless stations in the WLAN can achieve COT-based fairness by adjusting their packet length, sending the multiple back-to-back packets at one time, or giving up an opportunity to access the channel. Analysis and simulations show that our algorithm can provide COT-fairness. Compared with the CAP-based algorithm, the proposed algorithm leads to improvements in aggregate throughput of IEEE 802. lib multi-rate WLANs.展开更多
This paper introduces a new idea of controlling cavitation around a hydrofoil through a passive cavitation controller called artificial cavitation bubble generator （ACG）. Cyclic processes, namely, growth and implosi...This paper introduces a new idea of controlling cavitation around a hydrofoil through a passive cavitation controller called artificial cavitation bubble generator （ACG）. Cyclic processes, namely, growth and implosion of bubbles around an immersed body, are the main reasons for the destruction and erosion of the said body. This paper aims to create a condition in which the cavitation bubbles reach a steady-state situation and prevent the occurrence of the cyclic processes. For this purpose, the ACG is placed on the surface of an immersed body, in particular, the suction surface of a 2D hydrofoil. A simulation was performed with an implicit finite volume scheme based on a SIMPLE algorithm associated with the multiphase and cavitation model. The modified k-ε RNG turbulence model equipped with a modification of the turbulent viscosity was applied to overcome the turbulence closure problem. Numerical simulation of water flow over the hydrofoil equipped with the ACG shows that a low-pressure recirculation area is produced behind the ACG and artificially generates stationary cavitation bubbles. The location, shape, and size of this ACG are the crucial parameters in creating a proper control. Results show that the cavitation bubble is controlled well with a well-designed ACG.展开更多
Goethite is a metals-rich residue that occurs during zinc production. The feasibility of metal recovery from goethite has been demonstrated, but is not economically viable on an industrial scale. Therefore, goethite i...Goethite is a metals-rich residue that occurs during zinc production. The feasibility of metal recovery from goethite has been demonstrated, but is not economically viable on an industrial scale. Therefore, goethite is landfilled with considerable economic costs and environmental risks. The goal of this study is to evaluate the environmental performance of a new valorization strategy for goethite residues from zinc production, with the aims of： ① recovering the valuable zinc contained in the goethite and ② avoiding the landfilling of goethite by producing a clean byproduct. The presented goethite valoriza- tion strategy consists of a sequence of two processes： ① plasma fuming and ② inorganic polymerization of the fumed slag. Plasma fuming recovers the valuable metals by fuming the goethite. The metals-flee fumed slag undergoes a process of inorganic polymerization to form inorganic polymers, that can be used as a novel building material, as an alternative to ordinary Portland cement （OPC）-based concrete. Life- cycle assessment （LCA） is used to compare the environmental performance of the inorganic polymer with the environmental performances of equivalent OPC-based concrete. The LCA results show the tradeoff between the environmental burdens of the fuming process and inorganic polymerization versus the environmental benefits of metal recovery, OPC concrete substitution, and the avoidance of goethite land- filling. The goethite-based inorganic polymers production shows better performances in several environ- mental impact categories, thanks to the avoided landfilling of goethite. However, in other environmental impact categories, such as global warming, the goethite valorization is strongly affected by the high-energy requirements of the plasma-fuming process, which represent the environmental hotspots of the proposed goethite recycling scheme. The key elements toward the sustainability of goethite valorization have been identified, and include the use of a clean electric mix, more effective control of the fumed gas emissions, and a reduced use of fumed slag through increased efficiency of the inorganic polymerization process.展开更多
Amorphous silicon films are prepared at lower temperature of 350 ℃ by new catalytic chemical vapor deposition method.In the method,material gases (SiH 4 and H 2) are decomposed by catalytic reaction at given temper...Amorphous silicon films are prepared at lower temperature of 350 ℃ by new catalytic chemical vapor deposition method.In the method,material gases (SiH 4 and H 2) are decomposed by catalytic reaction at given temperature,so a-Si films are deposited on substrates.It is found that a-Si films with high quality can be obtain,such as high photosensitivity of 10 6,low spin density of 2.5×10 16 cm -3 .展开更多
The hydrocarbons and other organic compounds generated through abiogenic or inorganic processes are closely related to two science subjects, i.e., energy resources and life＇s origin and evolution. ＂The earth＇s prim...The hydrocarbons and other organic compounds generated through abiogenic or inorganic processes are closely related to two science subjects, i.e., energy resources and life＇s origin and evolution. ＂The earth＇s primordial abiogenic hydrocarbon theory＂ and ＂the serpentinization of abiogenic hydrocarbon theory＂ are the two mainstream theories in the field of related studies. Ser- pentinizafion generally occurs in slow expanding mid-ocean ridges and continental ophiolites tectonic environment, etc. The abiogenic hydrocarbons and other organic compounds formed through the serpentinization of ultramafic rocks provide energy and raw materials to support chemosynthetic microbial communities, which probably was the most important hydration reac- tion for the origin and early evolution of life. The superposition of biological and abiological processes creates big challenge to the identification of the abiogenic organic materials in serpentinite-hosted ecosystem. Whether abiotic （inorganic） process can form oil and gas resource is a difficult question that has been explored continuously by scientific community for more than a century but has not yet been solved. However, some important progress has been made. The prospecting practice of abiogenic hydrocarbons in commercial gases from the Songliao Basin, China, provides an important example for exploring abiogenic natural gas resources.展开更多
Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-c...Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-catalyst and solvent. The interaction between thiamine hydrochloride(VB_1-Cl) and substrates(CO_2 and propylene oxide) was proven by ultraviolet-visible spectroscopy and ~1H nuclear magnetic resonance analysis, and it is deduced that the synergistic action among multi-functional groups(hydroxyl, halide anion and amine) is a favorable factor for cycloaddition reaction. A series of VB_1/GO aerogels were facilely prepared through the addition of aqueous VB_1 derivatives to a suspension of GO in ethanol at room temperature. It was found that the aerogel generated through the interaction of VB_1-Cl with GO shows catalytic activity and stability higher than those of VB_1-Cl. It is because the electrostatic interaction between GO and VB_1-Cl enhances the nucleophilicity and leaving ability of anion. The effects of reaction temperature, catalyst loading, CO_2 pressure and reaction time on CO_2 cycloaddition to propylene oxide were thoroughly studied.展开更多
文摘Intertidal macroalgae experience continual alternation of photosynthesis between aquatic state at high tide and aerial state at low tide. The comparative photosynthetic responses to inorganic carbon were investigated in the common intertidal macroalga Ulva lactuca L. along the coast of Shantou between aquatic and aerial state. The inorganic carbon dissolved in seawater at present could fully (at 10 ℃ or 20 ℃) or nearly (at 30 ℃) saturate the aquatic photosynthesis of U. lactuca . However, the aerial photosynthesis was limited by current ambient atmospheric CO 2 level, and such a limitation was more severe at higher temperature (20-30 ℃) than at lower temperature (10 ℃). The carbon_saturated maximal photosynthesis of U. lactuca under aerial state was much greater than that under aquatic state at 10 ℃ and 20 ℃, while the maximal photosynthesis under both states was similar at 30 ℃. The aerial values of K m (CO 2) for photosynthesis were higher than the aquatic values. On the contrary, the values of apparent photosynthetic CO 2 conductance under aerial state were considerably lower than that under aquatic state. It was concluded that the increase of atmospheric CO 2 would enhance the primary productivity of U. lactuca through stimulating the photosynthesis under aerial state during low tide.
基金Supported by National Natural Science Foundation of China (No.60472078 and No.90604013) .
文摘This paper proposes a new channel access algorithm based on channel occupancy time （COT） fairness to guarantee fairness and improve the aggregate throughput of 802.11b multi-rate WLANs. In the algorithm, the COT is used as fairness index to analyze the fairness of WLANs instead of the channel access probability （CAP） used in the distributed coordination function （DCF）. The standard COT is given by access point （AP） and broadcasted to all wireless stations. The AP and wireless stations in the WLAN can achieve COT-based fairness by adjusting their packet length, sending the multiple back-to-back packets at one time, or giving up an opportunity to access the channel. Analysis and simulations show that our algorithm can provide COT-fairness. Compared with the CAP-based algorithm, the proposed algorithm leads to improvements in aggregate throughput of IEEE 802. lib multi-rate WLANs.
文摘This paper introduces a new idea of controlling cavitation around a hydrofoil through a passive cavitation controller called artificial cavitation bubble generator （ACG）. Cyclic processes, namely, growth and implosion of bubbles around an immersed body, are the main reasons for the destruction and erosion of the said body. This paper aims to create a condition in which the cavitation bubbles reach a steady-state situation and prevent the occurrence of the cyclic processes. For this purpose, the ACG is placed on the surface of an immersed body, in particular, the suction surface of a 2D hydrofoil. A simulation was performed with an implicit finite volume scheme based on a SIMPLE algorithm associated with the multiphase and cavitation model. The modified k-ε RNG turbulence model equipped with a modification of the turbulent viscosity was applied to overcome the turbulence closure problem. Numerical simulation of water flow over the hydrofoil equipped with the ACG shows that a low-pressure recirculation area is produced behind the ACG and artificially generates stationary cavitation bubbles. The location, shape, and size of this ACG are the crucial parameters in creating a proper control. Results show that the cavitation bubble is controlled well with a well-designed ACG.
文摘Goethite is a metals-rich residue that occurs during zinc production. The feasibility of metal recovery from goethite has been demonstrated, but is not economically viable on an industrial scale. Therefore, goethite is landfilled with considerable economic costs and environmental risks. The goal of this study is to evaluate the environmental performance of a new valorization strategy for goethite residues from zinc production, with the aims of： ① recovering the valuable zinc contained in the goethite and ② avoiding the landfilling of goethite by producing a clean byproduct. The presented goethite valoriza- tion strategy consists of a sequence of two processes： ① plasma fuming and ② inorganic polymerization of the fumed slag. Plasma fuming recovers the valuable metals by fuming the goethite. The metals-flee fumed slag undergoes a process of inorganic polymerization to form inorganic polymers, that can be used as a novel building material, as an alternative to ordinary Portland cement （OPC）-based concrete. Life- cycle assessment （LCA） is used to compare the environmental performance of the inorganic polymer with the environmental performances of equivalent OPC-based concrete. The LCA results show the tradeoff between the environmental burdens of the fuming process and inorganic polymerization versus the environmental benefits of metal recovery, OPC concrete substitution, and the avoidance of goethite land- filling. The goethite-based inorganic polymers production shows better performances in several environ- mental impact categories, thanks to the avoided landfilling of goethite. However, in other environmental impact categories, such as global warming, the goethite valorization is strongly affected by the high-energy requirements of the plasma-fuming process, which represent the environmental hotspots of the proposed goethite recycling scheme. The key elements toward the sustainability of goethite valorization have been identified, and include the use of a clean electric mix, more effective control of the fumed gas emissions, and a reduced use of fumed slag through increased efficiency of the inorganic polymerization process.
文摘Amorphous silicon films are prepared at lower temperature of 350 ℃ by new catalytic chemical vapor deposition method.In the method,material gases (SiH 4 and H 2) are decomposed by catalytic reaction at given temperature,so a-Si films are deposited on substrates.It is found that a-Si films with high quality can be obtain,such as high photosensitivity of 10 6,low spin density of 2.5×10 16 cm -3 .
基金supported by National Natural Science Foundation of China (Grant Nos. 41172133, 41272146, 41103022)
文摘The hydrocarbons and other organic compounds generated through abiogenic or inorganic processes are closely related to two science subjects, i.e., energy resources and life＇s origin and evolution. ＂The earth＇s primordial abiogenic hydrocarbon theory＂ and ＂the serpentinization of abiogenic hydrocarbon theory＂ are the two mainstream theories in the field of related studies. Ser- pentinizafion generally occurs in slow expanding mid-ocean ridges and continental ophiolites tectonic environment, etc. The abiogenic hydrocarbons and other organic compounds formed through the serpentinization of ultramafic rocks provide energy and raw materials to support chemosynthetic microbial communities, which probably was the most important hydration reac- tion for the origin and early evolution of life. The superposition of biological and abiological processes creates big challenge to the identification of the abiogenic organic materials in serpentinite-hosted ecosystem. Whether abiotic （inorganic） process can form oil and gas resource is a difficult question that has been explored continuously by scientific community for more than a century but has not yet been solved. However, some important progress has been made. The prospecting practice of abiogenic hydrocarbons in commercial gases from the Songliao Basin, China, provides an important example for exploring abiogenic natural gas resources.
文摘Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-catalyst and solvent. The interaction between thiamine hydrochloride(VB_1-Cl) and substrates(CO_2 and propylene oxide) was proven by ultraviolet-visible spectroscopy and ~1H nuclear magnetic resonance analysis, and it is deduced that the synergistic action among multi-functional groups(hydroxyl, halide anion and amine) is a favorable factor for cycloaddition reaction. A series of VB_1/GO aerogels were facilely prepared through the addition of aqueous VB_1 derivatives to a suspension of GO in ethanol at room temperature. It was found that the aerogel generated through the interaction of VB_1-Cl with GO shows catalytic activity and stability higher than those of VB_1-Cl. It is because the electrostatic interaction between GO and VB_1-Cl enhances the nucleophilicity and leaving ability of anion. The effects of reaction temperature, catalyst loading, CO_2 pressure and reaction time on CO_2 cycloaddition to propylene oxide were thoroughly studied.
