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Sohail Majid Zamani,Abolhassan Vafaei,A. A. Aghakouchak,Chandrakant Desai 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.2
Concentric bracings composed of three members arranged in y shaped geometry have been traditionally used to provide openings in braced bays. However, simultanous occurance of compression in three braces leads to instability and out of plane buckling of braces accompanied by low hysteretic energy absorption. In order to study the behavior of y-braced frames, a research program including experimental tests was conducted at BHRC† structural engineering laboratory. Quasi-static cyclic loading was applied to specimens including four full-scale two-bay frames with y-bracings of different cross sections and connection types.The bays are braced symmetrically to have a combination of tensile and compressive braces at all loading stages. The results show that out-of-plane buckling with single curvature in braces can be substituted by in plane, double curvature buckling through appropriate detailing of cross sections and connections.Thus, hysteretic energy dissipation of ybracing is remarkably improved due to spreading of plastic strains in braces. In this paper, seismic performance of y-braced frame specimens and a reference X-braced frame are also assessed by capacity spectrum method.
Urban Growth and Its Effect on Temperature Trends of Lahore City, Pakistan
Sohail Abbas,Mian Sabir Hussain,Sujeong Im,Seungho Lee,Safdar Ali Shirazi 건국대학교 기후연구소 2018 기후연구 Vol.13 No.3
The current study deals with the effect of urban growth and urbanization on temperature trends over Lahore city of Pakistan. This research was conducted using mean monthly temperature data for the period of 1950-2017. The urban population growth, urban expansion, the increase of vehicles and factories as well as the expansion of built up area have influenced on the change of temperature in Lahore city. The annual trends of temperatures have been analyzed, and their statistical significances are calculated by the linear regression method. It has been deduced that there is a close relation between temperature change and urban growth. The findings are as follows; the mean minimum temperature rises greater than the maximum temperature at urban station and rural station. However, the maximum temperature is not rising positively and thus significantly at both stations. The findings show the fact that mean minimum temperature increasing more quickly after the 1995 due to the increase of urban development in Lahore city in which the built up area has increased from 66 km² to 740 km² since 1950. A massive increase in the numbers of vehicles have also influenced on the change of temperature in the city. However, the mean maximum temperature at rural station of Lahore has significant effect during 1973-1997.
Survivability Analysis of MANET Routing Protocols under DOS Attacks
( Sohail Abbas ),( Muhammad Haqdad ),( Muhammad Zahid Khan ),( Haseeb Ur Rehman ),( Ajab Khan ),( Atta Ur Rehman Khan ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.9
The network capability to accomplish its functions in a timely fashion under failures and attacks is known as survivability. Ad hoc routing protocols have been studied and extended to various domains, such as Intelligent Transport Systems (ITSs), Unmanned Aerial Vehicles (UAVs), underwater acoustic networks, and Internet of Things (IoT) focusing on different aspects, such as security, QoS, energy. The existing solutions proposed in this domain incur substantial overhead and eventually become burden on the network, especially when there are fewer attacks or no attack at all. There is a need that the effectiveness of these routing protocols be analyzed in the presence of Denial of Service (DoS) attacks without any intrusion detection or prevention system. This will enable us to establish and identify the inherently stable routing protocols that are capable to survive longer in the presence of these attacks. This work presents a DoS attack case study to perform theoretical analysis of survivability on node and network level in the presence of DoS attacks. We evaluate the performance of reactive and proactive routing protocols and analyse their survivability. For experimentation, we use NS-2 simulator without detection or prevention capabilities. Results show that proactive protocols perform better in terms of throughput, overhead and packet drop.
( Sohail Ahmed ),( Malik Muhammad Asim ),( Nadeem Qaisar Mehmood ),( Mubashir Ali ),( Babar Shahzaad ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.2
To provide a guaranteed Quality of Service (QoS) to real-time traffic in High-Speed Downlink Packet Access (HSDPA) core network, we proposed an enhanced mechanism. For an enhanced QoS, a Class-Based Low Latency Fair Queueing (CBLLFQ) packet scheduling algorithm is introduced in this work. Packet classification, metering, queuing, and scheduling using differentiated services (DiffServ) environment was the points in focus. To classify different types of real-time voice and multimedia traffic, the QoS provisioning mechanisms use different DiffServ code points (DSCP).The proposed algorithm is based on traffic classes which efficiently require the guarantee of services and specified level of fairness. In CBLLFQ, a mapping criterion and an efficient queuing mechanism for voice, video and other traffic in separate queues are used. It is proved, that the algorithm enhances the throughput and fairness along with a reduction in the delay and packet loss factors for smooth and worst traffic conditions. The results calculated through simulation show that the proposed calculations meet the QoS prerequisites efficiently.