Sulphur dioxide (SO 2 ) mixed with carrier gases was used as an alternative to SF 6 to protect molten magnesium alloys. The protection behavior of AZ91D alloy in a sealed melting furnace was investigated under the a...Sulphur dioxide (SO 2 ) mixed with carrier gases was used as an alternative to SF 6 to protect molten magnesium alloys. The protection behavior of AZ91D alloy in a sealed melting furnace was investigated under the atmosphere containing SO 2 with different mixed gases. The morphology and composition of the surface film were studied. The melt was well protected in an atmosphere of SO 2 and a proper amount of air, and was not protected properly in the other atmospheres. Based on the understanding of the protective effects of SO 2 in the sealed furnace, the protection mechanism of SO 2 -containing cover gases on molten AZ91D alloy was studied in an open melting furnace. The cover gas protected the melt by reacting with the melt to form a coherent protective film with a network structure on the melt surface. The film contains MgO and MgS. MgS increases the Pilling and Bedworth ratio of the surface film and enhances the protective capability of the films.展开更多
An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency...An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency and pulse on time were studied. The experiments were conducted based on a four-factor, five-level, central composite design matrix. The developed empirical relationship can be effectively used to predict the tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that pulse frequency has the greatest influence on tensile strength, followed by peak current, pulse on time and base current.展开更多
This paper presents an efficient way to preserve the volume of implicit surfaces generated by skeletons. Recursive subdivision is used to efficiently calculate the volume. The criterion for subdivision is obtained by ...This paper presents an efficient way to preserve the volume of implicit surfaces generated by skeletons. Recursive subdivision is used to efficiently calculate the volume. The criterion for subdivision is obtained by using the property of density functions and treating different types of skeletons respectively to get accurate minimum and maximum distances from a cube to a skeleton. Compared with the criterion generated by other ways such as using traditional Interval Analysis, Affine Arithmetic, or Lipschitz condition, our approach is much better both in speed and accuracy.展开更多
Cereal-based foods play an important role as a source of dietary energy and nutrients in human nutrition. The use of microorganisms by humans has a long tradition. Bread making is one of the oldest arts known to man. ...Cereal-based foods play an important role as a source of dietary energy and nutrients in human nutrition. The use of microorganisms by humans has a long tradition. Bread making is one of the oldest arts known to man. Today we know that lactic acid bacteria (LAB) and yeasts are prevailing organisms in carbohydrate-rich environments. They break down carbohydrates to mainly lactic acid, ethanol and CO2. The present study is to determine the effect of Lactobacillus bulgaricus alone and as a combination with yeast (Saccharomyces cerevisiae) using yeast as a control. In this work, different percentage of Lactobacillus bulgaricus were used to investigate how sourdough affect on the bread sensory characteristics such as volume, specific loaf volume, crust, grain, color crumb, aroma, taste, texture, pH of bread and extended shelf life of bread. Also different storage times were used to know it is affected on the shelf life and sensory characteristics of bread. The results suggest that use of sourdough in bread production is useful in improving sensory properties, decreasing fungal spoilage.展开更多
For the last two decades the world has undergone a population explosion which has been accompanied by a speeding up of urbanization and land use for industrial and agricultural products. These involve a vast increase ...For the last two decades the world has undergone a population explosion which has been accompanied by a speeding up of urbanization and land use for industrial and agricultural products. These involve a vast increase in the discharge of pollutants into very different receiving water bodies, and have had adverse effects on the various components of the environment. For a long time, human has concerned a little of the natural environment. It is obvious that this variation in surface temperature of the earth increases the level of sea due to snowmelt. So climate change is manifested by many phenomena: floods, droughts, fires, tornadoes, cyclones, earthquakes, volcanic eruptions, diseases etc.. The statement today is dramatic. Entire regions were devastated and many rivers and lakes have become polluted around the world. Pollution has it nature which is hard to be absorbed. Where did the different pollutants come from? What are the risks to the aquatic environment? To prevent and combat the general decline of these ecosystems, it is important to distinguish and determine the effects of different sources of pollution and any changes that may suffer the physical environment. The climate depends primarily on changes in earth orbit parameters, which affect the solar radiation received by the earth surface. Therefore, human participates strongly to these changes, for example, pollution is the main reason to argue the greenhouse effect, an increase of anthropogenic carbon dioxide (CO2) into the atmosphere, which promotes global warming to the planet. These modifications are already applied in order to ensure durable development in water resources by controlling discharges into streams to preserve water resources for future generations and to ensure reconciliation between man-climate and environment.展开更多
Micro plasma arc surface melting of 0Cr19Ni9 shielded metal arc welding joint with a micro plasma arc welder produced a thin surface melted layer with a refined microstructure. The surface treatment changed the anod...Micro plasma arc surface melting of 0Cr19Ni9 shielded metal arc welding joint with a micro plasma arc welder produced a thin surface melted layer with a refined microstructure. The surface treatment changed the anodic polarization behavior in 0.5 mol/L H 2SO 4 solution. The polarization tests showed that for the as welded joint both the heat affected zone and the weld metal decreased in resistance to corrosion compared with the as received parent material while for the micro plasma arc surface melted joint the corrosion resistance increased significantly. This increase in corrosion resistance is attributed to the rapid solidification of the melted layer. Rapid solidification of the melted layer refines its microstructure, decreases its microsegregation, and inhibits the precipitation of chromium carbides at the grain boundaries.展开更多
基金Project(2009AA03Z114)supported by the National High-tech Research and Development Program of ChinaProject(20090002110029)supported by the Specialized Research Fund for the Doctoral Program of Higher Education,China
文摘Sulphur dioxide (SO 2 ) mixed with carrier gases was used as an alternative to SF 6 to protect molten magnesium alloys. The protection behavior of AZ91D alloy in a sealed melting furnace was investigated under the atmosphere containing SO 2 with different mixed gases. The morphology and composition of the surface film were studied. The melt was well protected in an atmosphere of SO 2 and a proper amount of air, and was not protected properly in the other atmospheres. Based on the understanding of the protective effects of SO 2 in the sealed furnace, the protection mechanism of SO 2 -containing cover gases on molten AZ91D alloy was studied in an open melting furnace. The cover gas protected the melt by reacting with the melt to form a coherent protective film with a network structure on the melt surface. The film contains MgO and MgS. MgS increases the Pilling and Bedworth ratio of the surface film and enhances the protective capability of the films.
文摘An empirical relationship to predict tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy was developed. Incorporating process parameters such as peak current, base current, pulse frequency and pulse on time were studied. The experiments were conducted based on a four-factor, five-level, central composite design matrix. The developed empirical relationship can be effectively used to predict the tensile strength of pulsed current gas tungsten arc welded AZ31B magnesium alloy joints at 95% confidence level. The results indicate that pulse frequency has the greatest influence on tensile strength, followed by peak current, pulse on time and base current.
文摘This paper presents an efficient way to preserve the volume of implicit surfaces generated by skeletons. Recursive subdivision is used to efficiently calculate the volume. The criterion for subdivision is obtained by using the property of density functions and treating different types of skeletons respectively to get accurate minimum and maximum distances from a cube to a skeleton. Compared with the criterion generated by other ways such as using traditional Interval Analysis, Affine Arithmetic, or Lipschitz condition, our approach is much better both in speed and accuracy.
文摘Cereal-based foods play an important role as a source of dietary energy and nutrients in human nutrition. The use of microorganisms by humans has a long tradition. Bread making is one of the oldest arts known to man. Today we know that lactic acid bacteria (LAB) and yeasts are prevailing organisms in carbohydrate-rich environments. They break down carbohydrates to mainly lactic acid, ethanol and CO2. The present study is to determine the effect of Lactobacillus bulgaricus alone and as a combination with yeast (Saccharomyces cerevisiae) using yeast as a control. In this work, different percentage of Lactobacillus bulgaricus were used to investigate how sourdough affect on the bread sensory characteristics such as volume, specific loaf volume, crust, grain, color crumb, aroma, taste, texture, pH of bread and extended shelf life of bread. Also different storage times were used to know it is affected on the shelf life and sensory characteristics of bread. The results suggest that use of sourdough in bread production is useful in improving sensory properties, decreasing fungal spoilage.
文摘For the last two decades the world has undergone a population explosion which has been accompanied by a speeding up of urbanization and land use for industrial and agricultural products. These involve a vast increase in the discharge of pollutants into very different receiving water bodies, and have had adverse effects on the various components of the environment. For a long time, human has concerned a little of the natural environment. It is obvious that this variation in surface temperature of the earth increases the level of sea due to snowmelt. So climate change is manifested by many phenomena: floods, droughts, fires, tornadoes, cyclones, earthquakes, volcanic eruptions, diseases etc.. The statement today is dramatic. Entire regions were devastated and many rivers and lakes have become polluted around the world. Pollution has it nature which is hard to be absorbed. Where did the different pollutants come from? What are the risks to the aquatic environment? To prevent and combat the general decline of these ecosystems, it is important to distinguish and determine the effects of different sources of pollution and any changes that may suffer the physical environment. The climate depends primarily on changes in earth orbit parameters, which affect the solar radiation received by the earth surface. Therefore, human participates strongly to these changes, for example, pollution is the main reason to argue the greenhouse effect, an increase of anthropogenic carbon dioxide (CO2) into the atmosphere, which promotes global warming to the planet. These modifications are already applied in order to ensure durable development in water resources by controlling discharges into streams to preserve water resources for future generations and to ensure reconciliation between man-climate and environment.
文摘Micro plasma arc surface melting of 0Cr19Ni9 shielded metal arc welding joint with a micro plasma arc welder produced a thin surface melted layer with a refined microstructure. The surface treatment changed the anodic polarization behavior in 0.5 mol/L H 2SO 4 solution. The polarization tests showed that for the as welded joint both the heat affected zone and the weld metal decreased in resistance to corrosion compared with the as received parent material while for the micro plasma arc surface melted joint the corrosion resistance increased significantly. This increase in corrosion resistance is attributed to the rapid solidification of the melted layer. Rapid solidification of the melted layer refines its microstructure, decreases its microsegregation, and inhibits the precipitation of chromium carbides at the grain boundaries.