In this article, an equivalent circuit approach has been used to study the bifrequency generation... more In this article, an equivalent circuit approach has been used to study the bifrequency generation by the azimuthally partitioned axially periodic metal disk-loaded coaxial structure. Considering the effect of all harmonics present within the structure and using an equivalent circuit approach, the expression of the equivalent series inductance per unit length and equivalent shunt capacitance per unit length has been obtained for this equivalent transmission line. In addition, with the help of computed equivalent series induction and equivalent shunt capacitance, expressions for the dispersion relation, phase velocity, and characteristic impedance have been obtained. The maximum possible frequency difference (i.e., bandwidth) between the modes (i.e., resonating frequency) and its region of operation have also been analytically computed. Finally, the parametric studies have been performed to find out the effect of structural parameter variation on dispersion behavior. In order to validate the numerical analysis, the structure has been first simulated with the help of CST microwave studio, and then, the analytically obtained results (such as dispersion behavior and phase velocity) have been compared with the results obtained from simulation. The comparison of results shows that the relative error is below than 5%, which shows a good agreement between them.
Journal of Electromagnetic Waves and Applications, 2020
The side-coupled cavity (SCC) structure is widely used in Linac, and also finds its application i... more The side-coupled cavity (SCC) structure is widely used in Linac, and also finds its application in the high-power microwave tubes. The SCC structure operating under the slow-wave regime, for the π /2 mode in transverse magnetic mode operation, has been electromagnetically analyzed using field-matching technique for the dispersion and interaction impedance characteristics. Furthermore, the effect of different structural parameters on the dispersion and interaction characteristics has been studied. To validate the developed dispersion and interaction relation, the SCC is simulated using commercially available electromagnetic simulation tools. The results obtained through the developed analytical expression are compared with the simulated results, and it is found to be in agreement within 3%. This analysis will help the design engineer to select the approximate accurate parameters before performing the simulation or experimental design. Also, it helps to develop a better understanding about the SCC's behavior with respect to structural parameter before the simulation.
ABSTRACT Authentication is the process of verifying a user's credentials when they are re... more ABSTRACT Authentication is the process of verifying a user's credentials when they are requesting services from any secure system. A simple authentication only involves a username and password, which can be easily deciphered. Hacking technologies have become more diversified and advanced, security and authenti-cation have become unable to rely on ID and password-based authentication alone. Single-factor authentication using an ID and password has been found to be vul-nerable to malware attacks, replay attacks, offline brute force attacks, key logger trojans, dictionary attacks and shoulder surfing. Adding a strong factor will reduce the chances of the user's identification from being hacked. This paper proposes a new multifactor authentication scheme, which combines with hard token, pass-word and biometric token with watermark image. Compared with the previous schemes this scheme has higher security in remote authentication and lower communication complexity.
ABSTRACT Security of information is a major concern now a days in the world. Cryptography plays a... more ABSTRACT Security of information is a major concern now a days in the world. Cryptography plays a major role in ensuring the safety of the information that is being transferred over the internet or any unsecure medium. Prime Numbers are very important aspect of any Cryptographic System and play a major role in ensuring the safety of the concerned Cryptographic System. Currently there are various algorithms used for checking that a particular number is a prime or not. Few of the commonly used algorithms are Divisibility Test, Fermat Test, and Chinese Primality Test etc. This paper proposes an enhancement in the Divisibility Primality Testing algorithm that reduces the number of comparisons to be made and thus enhancing the performance of the algorithm. In addition to this the pseudo code and implementation code of the improved algorithm are provided in detail. An analysis and comparison of the existing algorithm and the enhanced algorithm is also presented in the given paper.
2012 International Conference on ICT Convergence (ICTC), 2012
ABSTRACT Cloud computing is the most demanded advanced technology throughout the world. It is one... more ABSTRACT Cloud computing is the most demanded advanced technology throughout the world. It is one of the most significant topic whose application is being researched in today's time. One of the prominent services offered in cloud computing is the cloud storage. With the cloud storage, data is stored on multiple third party servers, rather than on the dedicated server used in traditional networked data storage. All data stored on multiple third party servers is not cared by the user and no one knows where exactly data saved. It is cared by the cloud storage provider that claims that they can protect the data but no one believes them. Data stored over cloud and flow through network in the plain text format is security threat. This paper proposes a method that allows user to store and access the data securely from the cloud storage. It also guarantees that no one except the authenticated user can access the data neither the cloud storage provider. This method ensures the security and privacy of data stored on cloud. A further advantage of this method is that if there is security breach at the cloud provider, the user's data will continue to be secure since all data is encrypted. Users also need not to worry about cloud providers gaining access to their data illegally.
Induction and maintenance immunosuppression protocols with or without long-term steroid therapy i... more Induction and maintenance immunosuppression protocols with or without long-term steroid therapy in kidney transplant recipients are variable and are transplant center-specific. The aim of this prospective randomized pilot study was to compare 5-year outcomes in kidney recipients maintained on 4 different calcineurin inhibitor (CNI)-based immunosuppression protocols without long-term steroid therapy. Two hundred consenting patients who received kidney transplants between June 2000 and October 2004 were enrolled in 4 immunosuppression protocol groups, with 50 patients in each group: cyclosporine (CSA)/mycophenolate mofetil (MMF), CSA/sirolimus (SRL), tacrolimus (TAC)/MMF, and TAC/SRL. Induction therapy was done with basiliximab and methylprednisolone. Steroids were withdrawn on post-transplant day 2, and long-term steroid therapy was not used. Demographic characteristics among the four groups were comparable; approximately 50% of the recipients were African American and > or =80% o...
Sixteen healthy young adults (ages 18-32) and 16 healthy older adults (ages 67-81) completed a de... more Sixteen healthy young adults (ages 18-32) and 16 healthy older adults (ages 67-81) completed a delayed response task in which they saw the following visual sequence: memory stimuli (2 abstract shapes; 3,000 ms), a blank delay (5,000 ms), a probe stimulus of variable duration (one abstract shape; 125, 250, 500, 1,000, or 2,000 ms), and a mask (500 ms). Subjects decided whether the probe stimulus matched either of the memory stimuli; they were instructed to respond during the mask, placing greater emphasis on speed than accuracy. The authors used D. L. Hintzman & T. Curran's (1994) 3-parameter compound bounded exponential model of speed-accuracy tradeoff to describe changes in discriminability associated with total processing time. Group-level analysis revealed a higher rate parameter and a higher asymptote parameter for the young adult group, but no difference across groups in x-intercept. Proxy measures of cognitive reserve (Y. Stern et al., 2005) predicted the rate parameter value, particularly in older adults. Results suggest that in working memory, aging impairs both the maximum capacity for discriminability and the rate of information accumulation, but not the temporal threshold for discriminability.
Immune parameters that predict long-term graft outcome and allow for individualization of immunos... more Immune parameters that predict long-term graft outcome and allow for individualization of immunosuppression are very important. In an effort to better define these parameters, a whole blood assay was developed to measure increases in iATP synthesis by CD4ϩ cells in response to stimulation with a mitogen Phytohemagglutinin (PHA) (ImmuKnow™, Cylex Inc.) which yields a rapid assessment of the early events in T cell activation without the requirement of long-term culture. We have applied this assay to test previously frozen peripheral blood lymphocytes (PBLs). Our goal was to measure the iATP levels (ng/ml) generated subsequent to PHA stimulation of PBLs from lung (LNG) recips procured pretransplant (pretx) to determine if these levels correlated with clinical events such as acute rejection (AR-diagnosed by transbronchial biopsy using ISHLT criteria). Briefly, frozen PBLs were thawed and cultured overnight with PHA. The CD4ϩ cells were magnetically selected and lysed. The light produced by luciferin and luciferase in the presence of the released iATP was measured in a luminometer and converted to ng/ml. We tested cells obtained pretx from 34 LNG recips with or without AR (Table). The results fell into two distinct groupings, High (Ͼ300 ATP ng/ml) and Low (Ͻ300 ATP ng/ml). The High group represented 33% (8/24) of recips that developed AR grade 2 or higher within 6mo posttx. The Low group included 20% (2/10) of recips who developed AR grade 2 or higher within 6mo. The negative predictive value was 80% for predicting those at low risk for developing AR. These preliminary results suggest that LNG recips who develop AR will do so within 6mo posttx. In addition, LNG recips with pretx values Ͼ300 ATP ng/ml are at increased risk for developing AR.
Epidemiologic evidence suggests that cognitive reserve (CR) mitigates the effects of aging on cog... more Epidemiologic evidence suggests that cognitive reserve (CR) mitigates the effects of aging on cognitive function. The goal of this study was to see whether a common neural mechanism for CR could be demonstrated in brain imaging data acquired during the performance of 2 tasks with differing cognitive processing demands. Young and elder subjects were scanned with functional magnetic resonance imaging (fMRI) while performing a delayed item response task that used either letters (40 young, 18 old) or shapes (24 young, 21 old). Difficulty or load was manipulated by varying the number of stimuli that were presented for encoding. Load-dependent fMRI signal corresponding to each trial component (stimulus presentation, retention delay, and probe) and task (letter or shape) was regressed onto 2 putative CR variables. Canonical variates analysis was applied to the resulting maps of regression coefficients, separately for each trial component, to summarize the imaging data-CR relationships. There was a latent brain pattern noted in the stimulus presentation phase that manifested similar relationships between load-related encoding activation and CR variables across the letter and shape tasks in the young but not the elder age group. This spatial pattern could represent a general neural instantiation of CR that is affected by the aging process.
The extent of task-related fMRI activation can vary as a function of task difficulty. Also the ef... more The extent of task-related fMRI activation can vary as a function of task difficulty. Also the efficiency or capacity of the brain networks underlying task performance can change with aging. We asked whether the expression of a network underlying task performance would differ as a function of task demand in old and young individuals. 26 younger and 23 older healthy adults performed a delayed item recognition task that used the response signal method to parametrically manipulate the extrinsic difficulty of the task by imposing five different deadlines for recognition response. Both age groups showed a speed-accuracy trade-off, but the younger group achieved greater discriminability at the longer deadlines. We identified a spatial pattern of fMRI activation during the probe phase whose expression increased as the response deadline shortened and the task became more difficult. This pattern was expressed to a greater degree by the old group at the long deadlines, when the task was easiest. By contrast, this pattern was expressed to a greater degree by the younger group at the short deadlines, when the task was hardest. This suggests reduced efficiency and capacity of this network in older subjects. These findings suggest that neuroimaging studies comparing task-related activation across groups with different cognitive abilities must be interpreted in light of the relative difficulty of the task for each group.
Three competing models of cognitive aging (neural compensation, capacity limitations, neural inef... more Three competing models of cognitive aging (neural compensation, capacity limitations, neural inefficiency) were examined in relation to working memory for novel non-verbal material. To accomplish this goal young (n = 25) and old (n = 25) participants performed a delayed item recognition (DIR) task while being scanned with bold fMRI. The stimuli in the DIR task consisted of computer-generated closed-curve shapes with each shape presented only once in the testing conditions of each participant. This ensured that both the novelty and appearance of the shapes maximized visual demands and limited the extent of phonologic processing. Behaviorally, as expected, the old participants were slower and less accurate compared to the young participants. Spatial patterns of brain activation that corresponded to load-dependent (stimulus set size ranged from 1 to 3) fMRI signal during the three phases of the DIR task (memory set presentation, retention delay, probe presentation) were evaluated in both age groups. Support for neural compensation and capacity limitation was evident in retention delay and the probe phase, respectively. Data were inconsistent with the neural inefficiency model. The process specific support for the theories we examined is consistent with a large corpus of research showing that the substrates underlying the encoding, retention and probe phases are different. That is, cognitive aging theories can be specific to the neural networks/regions underlying the different phases of working memory. Delineating how these theories work in concert can increase knowledge of age-related effects on working memory.
This functional neuroimaging (fMRI) study examined the neural networks (spatial patterns of covar... more This functional neuroimaging (fMRI) study examined the neural networks (spatial patterns of covarying neural activity) associated with the speed-accuracy tradeoff (SAT) in younger adults. The response signal method was used to systematically increase probe duration (125, 250, 500, 1,000 2,000 ms) in a nonverbal delayed-item recognition task. A covariance-based multivariate approach identified three networks that varied with probe duration-indicating that the SAT is driven by three distributed neural networks.
In this article, an equivalent circuit approach has been used to study the bifrequency generation... more In this article, an equivalent circuit approach has been used to study the bifrequency generation by the azimuthally partitioned axially periodic metal disk-loaded coaxial structure. Considering the effect of all harmonics present within the structure and using an equivalent circuit approach, the expression of the equivalent series inductance per unit length and equivalent shunt capacitance per unit length has been obtained for this equivalent transmission line. In addition, with the help of computed equivalent series induction and equivalent shunt capacitance, expressions for the dispersion relation, phase velocity, and characteristic impedance have been obtained. The maximum possible frequency difference (i.e., bandwidth) between the modes (i.e., resonating frequency) and its region of operation have also been analytically computed. Finally, the parametric studies have been performed to find out the effect of structural parameter variation on dispersion behavior. In order to validate the numerical analysis, the structure has been first simulated with the help of CST microwave studio, and then, the analytically obtained results (such as dispersion behavior and phase velocity) have been compared with the results obtained from simulation. The comparison of results shows that the relative error is below than 5%, which shows a good agreement between them.
Journal of Electromagnetic Waves and Applications, 2020
The side-coupled cavity (SCC) structure is widely used in Linac, and also finds its application i... more The side-coupled cavity (SCC) structure is widely used in Linac, and also finds its application in the high-power microwave tubes. The SCC structure operating under the slow-wave regime, for the π /2 mode in transverse magnetic mode operation, has been electromagnetically analyzed using field-matching technique for the dispersion and interaction impedance characteristics. Furthermore, the effect of different structural parameters on the dispersion and interaction characteristics has been studied. To validate the developed dispersion and interaction relation, the SCC is simulated using commercially available electromagnetic simulation tools. The results obtained through the developed analytical expression are compared with the simulated results, and it is found to be in agreement within 3%. This analysis will help the design engineer to select the approximate accurate parameters before performing the simulation or experimental design. Also, it helps to develop a better understanding about the SCC's behavior with respect to structural parameter before the simulation.
ABSTRACT Authentication is the process of verifying a user's credentials when they are re... more ABSTRACT Authentication is the process of verifying a user's credentials when they are requesting services from any secure system. A simple authentication only involves a username and password, which can be easily deciphered. Hacking technologies have become more diversified and advanced, security and authenti-cation have become unable to rely on ID and password-based authentication alone. Single-factor authentication using an ID and password has been found to be vul-nerable to malware attacks, replay attacks, offline brute force attacks, key logger trojans, dictionary attacks and shoulder surfing. Adding a strong factor will reduce the chances of the user's identification from being hacked. This paper proposes a new multifactor authentication scheme, which combines with hard token, pass-word and biometric token with watermark image. Compared with the previous schemes this scheme has higher security in remote authentication and lower communication complexity.
ABSTRACT Security of information is a major concern now a days in the world. Cryptography plays a... more ABSTRACT Security of information is a major concern now a days in the world. Cryptography plays a major role in ensuring the safety of the information that is being transferred over the internet or any unsecure medium. Prime Numbers are very important aspect of any Cryptographic System and play a major role in ensuring the safety of the concerned Cryptographic System. Currently there are various algorithms used for checking that a particular number is a prime or not. Few of the commonly used algorithms are Divisibility Test, Fermat Test, and Chinese Primality Test etc. This paper proposes an enhancement in the Divisibility Primality Testing algorithm that reduces the number of comparisons to be made and thus enhancing the performance of the algorithm. In addition to this the pseudo code and implementation code of the improved algorithm are provided in detail. An analysis and comparison of the existing algorithm and the enhanced algorithm is also presented in the given paper.
2012 International Conference on ICT Convergence (ICTC), 2012
ABSTRACT Cloud computing is the most demanded advanced technology throughout the world. It is one... more ABSTRACT Cloud computing is the most demanded advanced technology throughout the world. It is one of the most significant topic whose application is being researched in today's time. One of the prominent services offered in cloud computing is the cloud storage. With the cloud storage, data is stored on multiple third party servers, rather than on the dedicated server used in traditional networked data storage. All data stored on multiple third party servers is not cared by the user and no one knows where exactly data saved. It is cared by the cloud storage provider that claims that they can protect the data but no one believes them. Data stored over cloud and flow through network in the plain text format is security threat. This paper proposes a method that allows user to store and access the data securely from the cloud storage. It also guarantees that no one except the authenticated user can access the data neither the cloud storage provider. This method ensures the security and privacy of data stored on cloud. A further advantage of this method is that if there is security breach at the cloud provider, the user's data will continue to be secure since all data is encrypted. Users also need not to worry about cloud providers gaining access to their data illegally.
Induction and maintenance immunosuppression protocols with or without long-term steroid therapy i... more Induction and maintenance immunosuppression protocols with or without long-term steroid therapy in kidney transplant recipients are variable and are transplant center-specific. The aim of this prospective randomized pilot study was to compare 5-year outcomes in kidney recipients maintained on 4 different calcineurin inhibitor (CNI)-based immunosuppression protocols without long-term steroid therapy. Two hundred consenting patients who received kidney transplants between June 2000 and October 2004 were enrolled in 4 immunosuppression protocol groups, with 50 patients in each group: cyclosporine (CSA)/mycophenolate mofetil (MMF), CSA/sirolimus (SRL), tacrolimus (TAC)/MMF, and TAC/SRL. Induction therapy was done with basiliximab and methylprednisolone. Steroids were withdrawn on post-transplant day 2, and long-term steroid therapy was not used. Demographic characteristics among the four groups were comparable; approximately 50% of the recipients were African American and > or =80% o...
Sixteen healthy young adults (ages 18-32) and 16 healthy older adults (ages 67-81) completed a de... more Sixteen healthy young adults (ages 18-32) and 16 healthy older adults (ages 67-81) completed a delayed response task in which they saw the following visual sequence: memory stimuli (2 abstract shapes; 3,000 ms), a blank delay (5,000 ms), a probe stimulus of variable duration (one abstract shape; 125, 250, 500, 1,000, or 2,000 ms), and a mask (500 ms). Subjects decided whether the probe stimulus matched either of the memory stimuli; they were instructed to respond during the mask, placing greater emphasis on speed than accuracy. The authors used D. L. Hintzman & T. Curran's (1994) 3-parameter compound bounded exponential model of speed-accuracy tradeoff to describe changes in discriminability associated with total processing time. Group-level analysis revealed a higher rate parameter and a higher asymptote parameter for the young adult group, but no difference across groups in x-intercept. Proxy measures of cognitive reserve (Y. Stern et al., 2005) predicted the rate parameter value, particularly in older adults. Results suggest that in working memory, aging impairs both the maximum capacity for discriminability and the rate of information accumulation, but not the temporal threshold for discriminability.
Immune parameters that predict long-term graft outcome and allow for individualization of immunos... more Immune parameters that predict long-term graft outcome and allow for individualization of immunosuppression are very important. In an effort to better define these parameters, a whole blood assay was developed to measure increases in iATP synthesis by CD4ϩ cells in response to stimulation with a mitogen Phytohemagglutinin (PHA) (ImmuKnow™, Cylex Inc.) which yields a rapid assessment of the early events in T cell activation without the requirement of long-term culture. We have applied this assay to test previously frozen peripheral blood lymphocytes (PBLs). Our goal was to measure the iATP levels (ng/ml) generated subsequent to PHA stimulation of PBLs from lung (LNG) recips procured pretransplant (pretx) to determine if these levels correlated with clinical events such as acute rejection (AR-diagnosed by transbronchial biopsy using ISHLT criteria). Briefly, frozen PBLs were thawed and cultured overnight with PHA. The CD4ϩ cells were magnetically selected and lysed. The light produced by luciferin and luciferase in the presence of the released iATP was measured in a luminometer and converted to ng/ml. We tested cells obtained pretx from 34 LNG recips with or without AR (Table). The results fell into two distinct groupings, High (Ͼ300 ATP ng/ml) and Low (Ͻ300 ATP ng/ml). The High group represented 33% (8/24) of recips that developed AR grade 2 or higher within 6mo posttx. The Low group included 20% (2/10) of recips who developed AR grade 2 or higher within 6mo. The negative predictive value was 80% for predicting those at low risk for developing AR. These preliminary results suggest that LNG recips who develop AR will do so within 6mo posttx. In addition, LNG recips with pretx values Ͼ300 ATP ng/ml are at increased risk for developing AR.
Epidemiologic evidence suggests that cognitive reserve (CR) mitigates the effects of aging on cog... more Epidemiologic evidence suggests that cognitive reserve (CR) mitigates the effects of aging on cognitive function. The goal of this study was to see whether a common neural mechanism for CR could be demonstrated in brain imaging data acquired during the performance of 2 tasks with differing cognitive processing demands. Young and elder subjects were scanned with functional magnetic resonance imaging (fMRI) while performing a delayed item response task that used either letters (40 young, 18 old) or shapes (24 young, 21 old). Difficulty or load was manipulated by varying the number of stimuli that were presented for encoding. Load-dependent fMRI signal corresponding to each trial component (stimulus presentation, retention delay, and probe) and task (letter or shape) was regressed onto 2 putative CR variables. Canonical variates analysis was applied to the resulting maps of regression coefficients, separately for each trial component, to summarize the imaging data-CR relationships. There was a latent brain pattern noted in the stimulus presentation phase that manifested similar relationships between load-related encoding activation and CR variables across the letter and shape tasks in the young but not the elder age group. This spatial pattern could represent a general neural instantiation of CR that is affected by the aging process.
The extent of task-related fMRI activation can vary as a function of task difficulty. Also the ef... more The extent of task-related fMRI activation can vary as a function of task difficulty. Also the efficiency or capacity of the brain networks underlying task performance can change with aging. We asked whether the expression of a network underlying task performance would differ as a function of task demand in old and young individuals. 26 younger and 23 older healthy adults performed a delayed item recognition task that used the response signal method to parametrically manipulate the extrinsic difficulty of the task by imposing five different deadlines for recognition response. Both age groups showed a speed-accuracy trade-off, but the younger group achieved greater discriminability at the longer deadlines. We identified a spatial pattern of fMRI activation during the probe phase whose expression increased as the response deadline shortened and the task became more difficult. This pattern was expressed to a greater degree by the old group at the long deadlines, when the task was easiest. By contrast, this pattern was expressed to a greater degree by the younger group at the short deadlines, when the task was hardest. This suggests reduced efficiency and capacity of this network in older subjects. These findings suggest that neuroimaging studies comparing task-related activation across groups with different cognitive abilities must be interpreted in light of the relative difficulty of the task for each group.
Three competing models of cognitive aging (neural compensation, capacity limitations, neural inef... more Three competing models of cognitive aging (neural compensation, capacity limitations, neural inefficiency) were examined in relation to working memory for novel non-verbal material. To accomplish this goal young (n = 25) and old (n = 25) participants performed a delayed item recognition (DIR) task while being scanned with bold fMRI. The stimuli in the DIR task consisted of computer-generated closed-curve shapes with each shape presented only once in the testing conditions of each participant. This ensured that both the novelty and appearance of the shapes maximized visual demands and limited the extent of phonologic processing. Behaviorally, as expected, the old participants were slower and less accurate compared to the young participants. Spatial patterns of brain activation that corresponded to load-dependent (stimulus set size ranged from 1 to 3) fMRI signal during the three phases of the DIR task (memory set presentation, retention delay, probe presentation) were evaluated in both age groups. Support for neural compensation and capacity limitation was evident in retention delay and the probe phase, respectively. Data were inconsistent with the neural inefficiency model. The process specific support for the theories we examined is consistent with a large corpus of research showing that the substrates underlying the encoding, retention and probe phases are different. That is, cognitive aging theories can be specific to the neural networks/regions underlying the different phases of working memory. Delineating how these theories work in concert can increase knowledge of age-related effects on working memory.
This functional neuroimaging (fMRI) study examined the neural networks (spatial patterns of covar... more This functional neuroimaging (fMRI) study examined the neural networks (spatial patterns of covarying neural activity) associated with the speed-accuracy tradeoff (SAT) in younger adults. The response signal method was used to systematically increase probe duration (125, 250, 500, 1,000 2,000 ms) in a nonverbal delayed-item recognition task. A covariance-based multivariate approach identified three networks that varied with probe duration-indicating that the SAT is driven by three distributed neural networks.
Uploads
Papers by Arjun kumar