This study investigated whether the pouring ladle's outlet shape could reduce the porosity of aluminum alloy casting products and whether it could be applied to mass production of automotive brackets based on comp...This study investigated whether the pouring ladle's outlet shape could reduce the porosity of aluminum alloy casting products and whether it could be applied to mass production of automotive brackets based on computer simulations and experiment.The filling behaviors of the melt were simulated to compare the flow characteristics of the molten metal poured from the conventional ladle and the proposed ladle.Results show that for the conventional ladle,the pouring metal is V-shaped,while it is relatively circular and poured at a more constant rate in the proposed ladle.CT scans reveal that the proposed ladle reduces the porosity of the cast product.The proposed ladle resulted in an average of 30 fewer pores,a 299.56 mm3 smaller average total pore volume,and a 0.041% lower difference in average porosity.It is concludes that the proposed ladle can be used in the gravity casting process.By changing the ladle outlet shape can reduce the casting failure rate of massproduced automobile bracket.展开更多
The botnet is the network of compromised computers that have fallen under the control of hackers after being infected by malicious programs such as trojan viruses. The compromised machines are mobilized to perform var...The botnet is the network of compromised computers that have fallen under the control of hackers after being infected by malicious programs such as trojan viruses. The compromised machines are mobilized to perform various attacks including mass spamming, distributed denial of service （DDoS） and additional trojans. This is becoming one of the most serious threats to the Internet infrastructure at present. We introduce a method to uncover compromised machines and characterize their behaviors using large email logs. We report various spain campaign variants with different characteristics and introduce a statistical method to combine them. We also report the long-term evolution patterns of the spare campaigns.展开更多
基金supported by the National Research Foundation of Korea(NRF)(2015R1A5A1037668)the Ministry of Trade,Industry and Energy(Grant N0002310)
文摘This study investigated whether the pouring ladle's outlet shape could reduce the porosity of aluminum alloy casting products and whether it could be applied to mass production of automotive brackets based on computer simulations and experiment.The filling behaviors of the melt were simulated to compare the flow characteristics of the molten metal poured from the conventional ladle and the proposed ladle.Results show that for the conventional ladle,the pouring metal is V-shaped,while it is relatively circular and poured at a more constant rate in the proposed ladle.CT scans reveal that the proposed ladle reduces the porosity of the cast product.The proposed ladle resulted in an average of 30 fewer pores,a 299.56 mm3 smaller average total pore volume,and a 0.041% lower difference in average porosity.It is concludes that the proposed ladle can be used in the gravity casting process.By changing the ladle outlet shape can reduce the casting failure rate of massproduced automobile bracket.
基金supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Education,Science and Technology (MEST) of Korea under Grant No. 2012R1A2A2A01014729
文摘The botnet is the network of compromised computers that have fallen under the control of hackers after being infected by malicious programs such as trojan viruses. The compromised machines are mobilized to perform various attacks including mass spamming, distributed denial of service （DDoS） and additional trojans. This is becoming one of the most serious threats to the Internet infrastructure at present. We introduce a method to uncover compromised machines and characterize their behaviors using large email logs. We report various spain campaign variants with different characteristics and introduce a statistical method to combine them. We also report the long-term evolution patterns of the spare campaigns.
