Short circuit transfer involves bridging between the consumable electrode and the weld pool, associated with variations of electrical parameters which characterize the change of molten metal bridge state and are very ...Short circuit transfer involves bridging between the consumable electrode and the weld pool, associated with variations of electrical parameters which characterize the change of molten metal bridge state and are very important for the control of .spatter. In this paper, electrical process parameters and short circuit transfer images were simultaneously recorded with a LabView-based synchronous sensing and visualizing system. The arc^bridge resistance and derivatives of welding current, arc voltage and arc resistance at various instants were calculated by means of offline analysis of the welding current, arc voltage and droplet images. Parameters and their feature values indicating the onset of short circuit and the oncoming necking-down of molten metal bridge were determined. Using the calculated feature values, bridge-state-feedback control for .short circuit transfer was realized with a spatter rate less than 0. 25%.展开更多
The increase in natural gas reserves makes methane a significant hydrocarbon feedstock. However, thedirect catalytic conversion of methane into liquid fuels and useful chemicals remains a great challenge,and many stud...The increase in natural gas reserves makes methane a significant hydrocarbon feedstock. However, thedirect catalytic conversion of methane into liquid fuels and useful chemicals remains a great challenge,and many studies have been devoted to this field in the past decades. Electrocatalysis is considered asan important alternative approach for the direct conversion of methane into value-added chemicals, al-though many other innovative methods have been developed. This review highlights recent advances inelectrocatalytic conversion of methane to ethylene and methanol, two important chemicals. The electro-catalytic systems efficient for methane conversions are summarized with an emphasis on catalysts andelectrolytes. The effects of reaction conditions such as the temperature and the acid-base property of thereaction medium are also discussed,展开更多
The single fault and multiple fault detections for multiple-valued logic circuits are studied in this paper. Firstly, it is shown that the cardinality of optimal single fault test set for fanout-free m-valued circuits...The single fault and multiple fault detections for multiple-valued logic circuits are studied in this paper. Firstly, it is shown that the cardinality of optimal single fault test set for fanout-free m-valued circuits with n primary inputs is not more than n + 1, for linear tree circuits is two, and for multiplication modulo circuits is two if n is an odd number or if n is an even number and m ＞ 3, where the optimal test set of a circuit has minimal number of test vectors. Secondly,it is indicated that the cardinality of optimal multiple fault test set for linear tree circuits with n primary inputs is 1 + [n/(m - 1)], for multiplication modulo circuits is n+ 1, for fanout-free circuits that consist of 2-input linear tree circuits and 2-input multiplication modulo circuits is not greater than n+ 1, where [x] denotes the smallest integer greater than or equal to x. Finally,the single fault location approaches of linear tree circuits and multiplication modulo circuits are presented, and all faults in the two types of circuits can be located by using a test set with n + 1 vectors.展开更多
This paper proposes a simplification method for realization of current-mode multivalued CMOS circuits. The key of this method is to find a cover on the K-map for a given multivalued function, which fits to the realiza...This paper proposes a simplification method for realization of current-mode multivalued CMOS circuits. The key of this method is to find a cover on the K-map for a given multivalued function, which fits to the realization of current-mode CMOS circuits. The design example shows that the design presented in this paper is better than the design proposed by G. W. Dueck et al. (1987).展开更多
Many factors were found to have effects on the conversion coatings for AZ31 alloy, alloy the most important one in producing high quality conversion coatings is found to be the control of the pH value. The influence o...Many factors were found to have effects on the conversion coatings for AZ31 alloy, alloy the most important one in producing high quality conversion coatings is found to be the control of the pH value. The influence of pH value on the conversion coating including color, thickness, adhesion and surface morphology was studied. The performance of conversion coating was examined by cross cut test, SEM method and salt immersion. The results show that the variation of pH value causes surface treatment process unstably. The conversion coating can obtain as pH value ranging from 3.0 to 5.0, while it presents dark, thick and bad adhesion under lower pH value. The conversion coatings have good combination of thickness and adhesion when pH value ranging from 4.0 to 4.5, and it exhibits a good corrosion resistance.展开更多
基金This work is supported by Shandong Natural Science Foundation （ Key Project） under contract No. ZR2010EZ005.
文摘Short circuit transfer involves bridging between the consumable electrode and the weld pool, associated with variations of electrical parameters which characterize the change of molten metal bridge state and are very important for the control of .spatter. In this paper, electrical process parameters and short circuit transfer images were simultaneously recorded with a LabView-based synchronous sensing and visualizing system. The arc^bridge resistance and derivatives of welding current, arc voltage and arc resistance at various instants were calculated by means of offline analysis of the welding current, arc voltage and droplet images. Parameters and their feature values indicating the onset of short circuit and the oncoming necking-down of molten metal bridge were determined. Using the calculated feature values, bridge-state-feedback control for .short circuit transfer was realized with a spatter rate less than 0. 25%.
基金supported by the SINOPEC(No.415069)the National Natural Science Foundation of China (Nos.21690082,91545203 and 21503176)
文摘The increase in natural gas reserves makes methane a significant hydrocarbon feedstock. However, thedirect catalytic conversion of methane into liquid fuels and useful chemicals remains a great challenge,and many studies have been devoted to this field in the past decades. Electrocatalysis is considered asan important alternative approach for the direct conversion of methane into value-added chemicals, al-though many other innovative methods have been developed. This review highlights recent advances inelectrocatalytic conversion of methane to ethylene and methanol, two important chemicals. The electro-catalytic systems efficient for methane conversions are summarized with an emphasis on catalysts andelectrolytes. The effects of reaction conditions such as the temperature and the acid-base property of thereaction medium are also discussed,
基金Supported by the National Natural Science Foundation of China (No.60006002) Education Department of Guangdong Province of China (No. Z02019)
文摘The single fault and multiple fault detections for multiple-valued logic circuits are studied in this paper. Firstly, it is shown that the cardinality of optimal single fault test set for fanout-free m-valued circuits with n primary inputs is not more than n + 1, for linear tree circuits is two, and for multiplication modulo circuits is two if n is an odd number or if n is an even number and m ＞ 3, where the optimal test set of a circuit has minimal number of test vectors. Secondly,it is indicated that the cardinality of optimal multiple fault test set for linear tree circuits with n primary inputs is 1 + [n/(m - 1)], for multiplication modulo circuits is n+ 1, for fanout-free circuits that consist of 2-input linear tree circuits and 2-input multiplication modulo circuits is not greater than n+ 1, where [x] denotes the smallest integer greater than or equal to x. Finally,the single fault location approaches of linear tree circuits and multiplication modulo circuits are presented, and all faults in the two types of circuits can be located by using a test set with n + 1 vectors.
基金Supported by the National Natural Science Foundation of China
文摘This paper proposes a simplification method for realization of current-mode multivalued CMOS circuits. The key of this method is to find a cover on the K-map for a given multivalued function, which fits to the realization of current-mode CMOS circuits. The design example shows that the design presented in this paper is better than the design proposed by G. W. Dueck et al. (1987).
基金Project(BK2006543) supported by the Nature Science Foundation of Jiangsu Province, Chinaproject (2005KJA13) supported by the CHALCO S&T Foundation
文摘Many factors were found to have effects on the conversion coatings for AZ31 alloy, alloy the most important one in producing high quality conversion coatings is found to be the control of the pH value. The influence of pH value on the conversion coating including color, thickness, adhesion and surface morphology was studied. The performance of conversion coating was examined by cross cut test, SEM method and salt immersion. The results show that the variation of pH value causes surface treatment process unstably. The conversion coating can obtain as pH value ranging from 3.0 to 5.0, while it presents dark, thick and bad adhesion under lower pH value. The conversion coatings have good combination of thickness and adhesion when pH value ranging from 4.0 to 4.5, and it exhibits a good corrosion resistance.
