AA 6061-T6 aluminium alloy(Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high specific strength and good corrosion resistance.Compared with the fusion welding p...AA 6061-T6 aluminium alloy(Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high specific strength and good corrosion resistance.Compared with the fusion welding processes that are routinely used for joining structural aluminium alloys,friction stir welding(FSW) process is an emerging solid state joining process in which the material welded does not melt and recast.Joint strength is influenced by the grain size and tensile strength of the weld nugget region.Hence,an attempt was made to develop empirical relationships to predict grain size and tensile strength of friction stir welded AA 6061-T6 aluminium alloy joints.The empirical relationships are developed by response surface methodology(RSM) incorporating FSW tool and process parameters.A linear regression relationship was also established between grain size and tensile strength of the weld nugget of FSW joints.展开更多
Silicon carbide particulate （SiCp） reinforced cast aluminium （A1） based metal matrix composites （MMCs） have gained wide acceptance in the fabrication of light weight structures requiring high specific strength, ...Silicon carbide particulate （SiCp） reinforced cast aluminium （A1） based metal matrix composites （MMCs） have gained wide acceptance in the fabrication of light weight structures requiring high specific strength, high temperature capability and good wear resistance. Friction stir welding （FSW） process parameters play major role in deciding the performance of welded joints. The ultimate tensile strength, notch tensile strength and weld nugget hardness of friction stir butt welded joints of cast A1/SiCp MMCs （AA6061 with 20% （volume fraction） of SiCp） were investigated. The relationships between the FSW process parameters （rotational speed, welding speed and axial force） and the responses （ultimate tensile strength, notch tensile strength and weld nugget hardness） were established. The optimal welding parameters to maximize the mechanical properties were identified by using desirability approach. From this investigation, it is found that the joints fabricated with the tool rotational speed of 1370 r/min, welding speed of 88.9 mm/min, and axial force of 9.6 kN yield the maximum ultimate tensile strength, notch tensile strength and hardness of 265 MPa, 201 MPa and HV 114, respectively.展开更多
Super 304 H austenitic stainless steel with 3% of copper posses excellent creep strength and corrosion resistance, which is mainly used in heat exchanger tubing of the boiler. Heat exchangers are used in nuclear power...Super 304 H austenitic stainless steel with 3% of copper posses excellent creep strength and corrosion resistance, which is mainly used in heat exchanger tubing of the boiler. Heat exchangers are used in nuclear power plants and marine vehicles which are intended to operate in chloride rich offshore environment. Chloride stress corrosion cracking is the most likely life limiting failure with austenitic stainless steel tubing. Welding may worsen the stress corrosion cracking susceptibility of the material. Stress corrosion cracking susceptibility of Super 304 H parent metal and gas tungsten arc(GTA) welded joints were studied by constant load tests in 45% boiling Mg Cl2 solution. Stress corrosion cracking resistance of Super 304 H stainless steel was deteriorated by GTA welding due to the formation of susceptible microstructure in the HAZ of the weld joint and the residual stresses. The mechanism of cracking was found to be anodic path cracking, with transgranular nature of crack propagation. Linear relationships were derived to predict the time to failure by extrapolating the rate of steady state elongation.展开更多
Cloud computing becomes an important application development platform for processing user data with high security.Service providers are accustomed to providing storage centers outside the trusted location preferred by...Cloud computing becomes an important application development platform for processing user data with high security.Service providers are accustomed to providing storage centers outside the trusted location preferred by the data owner.Thus,ensuring the security and confidentiality of the data while processing in the centralized network is very difficult.The secured key transmission between the sender and the receiver in the network is a huge challenge in managing most of the sensitive data transmission among the cloud network.Intruders are very active over the network like real authenticated user to hack the personal sensitive data,such as bank balance,health data,personal data,and confidential documents over the cloud network.In this research,a secured key agreement between the sender and the receiver using Kerberos authentication protocol with fingerprint is proposed to ensure security in M-Healthcare.Conditions of patients are monitored using wireless sensor devices and are then transferred to the server.Kerberos protocol helps in avoiding unnecessary communication of authenticated data over the cloud network.Biometric security process is a procedure with the best security in most of the authentication field.Trust node is responsible in carrying data packets from the sender to the receiver in the cloud network.The Kerberos protocol is used in trust node to ensure security.Secured communication between the local health center and the healthcare server is ensured by using a fingerprint feature called minutiae form,which refers to the fingerprint image of both sender and receiver.The computational and communicational cost of the proposed system is lesser when compared with other existing authentication methods.展开更多
The Pleurotus florida is recognized as a medicinal and edible mushroom and the present study intends to reveal the active isomeric molecules from this mushroom.The P.florida was cultivated using different nutrient sup...The Pleurotus florida is recognized as a medicinal and edible mushroom and the present study intends to reveal the active isomeric molecules from this mushroom.The P.florida was cultivated using different nutrient supplements:groundnut husk,maize powder,horse gram powder and coconut oil-cake powder.Horse gram supplement showed the higher mushroom yield and henceit was used for the cultivation of P.florida.Methanolic extract of P.florida was found to be efficient in antioxidant activity among ethanol,aqueous,ethyl acetate and hexane extracts.The bioactive fraction 3-methoxy-4-hydroxy cinnamic acid(PF5)was isolated and purified from the methanolic extract of P.florida by column chromatography,thin layer chromatography(TLC)and gas chromatography-mass spectrum(GC-MS)and further it was characterized by Nuclear magnetic resonance(NMR).The PF5 was tested for its DPPH and reducing power assays,and the IC_(50) values were found to be 21.7μg/mL and 105μg/mL,respectively.We found that the cytotoxic effect of 3-methoxy-4-hydroxy cinnamic acid was tested against the lung cancer cell line using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT),sulphorodamine B(SRB)and trypan blue assays which exhibited a higher cytotoxic effect(CTC_(50),645μg/mL).These results suggested that 3-methoxy-4-hydroxy cinnamic acid from P.florida could be explored as a novel and potent natural antioxidant and cancer preventive agent,alternative to existing synthetic molecules.展开更多
文摘AA 6061-T6 aluminium alloy(Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high specific strength and good corrosion resistance.Compared with the fusion welding processes that are routinely used for joining structural aluminium alloys,friction stir welding(FSW) process is an emerging solid state joining process in which the material welded does not melt and recast.Joint strength is influenced by the grain size and tensile strength of the weld nugget region.Hence,an attempt was made to develop empirical relationships to predict grain size and tensile strength of friction stir welded AA 6061-T6 aluminium alloy joints.The empirical relationships are developed by response surface methodology(RSM) incorporating FSW tool and process parameters.A linear regression relationship was also established between grain size and tensile strength of the weld nugget of FSW joints.
文摘Silicon carbide particulate （SiCp） reinforced cast aluminium （A1） based metal matrix composites （MMCs） have gained wide acceptance in the fabrication of light weight structures requiring high specific strength, high temperature capability and good wear resistance. Friction stir welding （FSW） process parameters play major role in deciding the performance of welded joints. The ultimate tensile strength, notch tensile strength and weld nugget hardness of friction stir butt welded joints of cast A1/SiCp MMCs （AA6061 with 20% （volume fraction） of SiCp） were investigated. The relationships between the FSW process parameters （rotational speed, welding speed and axial force） and the responses （ultimate tensile strength, notch tensile strength and weld nugget hardness） were established. The optimal welding parameters to maximize the mechanical properties were identified by using desirability approach. From this investigation, it is found that the joints fabricated with the tool rotational speed of 1370 r/min, welding speed of 88.9 mm/min, and axial force of 9.6 kN yield the maximum ultimate tensile strength, notch tensile strength and hardness of 265 MPa, 201 MPa and HV 114, respectively.
文摘Super 304 H austenitic stainless steel with 3% of copper posses excellent creep strength and corrosion resistance, which is mainly used in heat exchanger tubing of the boiler. Heat exchangers are used in nuclear power plants and marine vehicles which are intended to operate in chloride rich offshore environment. Chloride stress corrosion cracking is the most likely life limiting failure with austenitic stainless steel tubing. Welding may worsen the stress corrosion cracking susceptibility of the material. Stress corrosion cracking susceptibility of Super 304 H parent metal and gas tungsten arc(GTA) welded joints were studied by constant load tests in 45% boiling Mg Cl2 solution. Stress corrosion cracking resistance of Super 304 H stainless steel was deteriorated by GTA welding due to the formation of susceptible microstructure in the HAZ of the weld joint and the residual stresses. The mechanism of cracking was found to be anodic path cracking, with transgranular nature of crack propagation. Linear relationships were derived to predict the time to failure by extrapolating the rate of steady state elongation.
文摘Cloud computing becomes an important application development platform for processing user data with high security.Service providers are accustomed to providing storage centers outside the trusted location preferred by the data owner.Thus,ensuring the security and confidentiality of the data while processing in the centralized network is very difficult.The secured key transmission between the sender and the receiver in the network is a huge challenge in managing most of the sensitive data transmission among the cloud network.Intruders are very active over the network like real authenticated user to hack the personal sensitive data,such as bank balance,health data,personal data,and confidential documents over the cloud network.In this research,a secured key agreement between the sender and the receiver using Kerberos authentication protocol with fingerprint is proposed to ensure security in M-Healthcare.Conditions of patients are monitored using wireless sensor devices and are then transferred to the server.Kerberos protocol helps in avoiding unnecessary communication of authenticated data over the cloud network.Biometric security process is a procedure with the best security in most of the authentication field.Trust node is responsible in carrying data packets from the sender to the receiver in the cloud network.The Kerberos protocol is used in trust node to ensure security.Secured communication between the local health center and the healthcare server is ensured by using a fingerprint feature called minutiae form,which refers to the fingerprint image of both sender and receiver.The computational and communicational cost of the proposed system is lesser when compared with other existing authentication methods.
文摘The Pleurotus florida is recognized as a medicinal and edible mushroom and the present study intends to reveal the active isomeric molecules from this mushroom.The P.florida was cultivated using different nutrient supplements:groundnut husk,maize powder,horse gram powder and coconut oil-cake powder.Horse gram supplement showed the higher mushroom yield and henceit was used for the cultivation of P.florida.Methanolic extract of P.florida was found to be efficient in antioxidant activity among ethanol,aqueous,ethyl acetate and hexane extracts.The bioactive fraction 3-methoxy-4-hydroxy cinnamic acid(PF5)was isolated and purified from the methanolic extract of P.florida by column chromatography,thin layer chromatography(TLC)and gas chromatography-mass spectrum(GC-MS)and further it was characterized by Nuclear magnetic resonance(NMR).The PF5 was tested for its DPPH and reducing power assays,and the IC_(50) values were found to be 21.7μg/mL and 105μg/mL,respectively.We found that the cytotoxic effect of 3-methoxy-4-hydroxy cinnamic acid was tested against the lung cancer cell line using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT),sulphorodamine B(SRB)and trypan blue assays which exhibited a higher cytotoxic effect(CTC_(50),645μg/mL).These results suggested that 3-methoxy-4-hydroxy cinnamic acid from P.florida could be explored as a novel and potent natural antioxidant and cancer preventive agent,alternative to existing synthetic molecules.
