In Opportunistic Networks most of Internet''s basic assumptions do not hold true. Due to sparse density of nodes and frequent changes in network topology, an endto- end contemporaneous path may not exist. However, sporadic links emerging from coarse-grained mobility of nodes can be construed over a period of time, as presence of a complete path between a pair of nodes. Nodes hold a packet in permanent storage until an appropriate communication opportunity arises, which can help in further forwarding of the packet. In order to avoid packet loss, multiple copies of a single message are generally sent within the network, independently making their way to eventual destination. This design decision poses extra burden over network resources, and unnecessary utilization may result in degrading performance in resource-stringent environments. Hence, there is need to reduce this extra overhead, by determining e ective next-hop utility of nodes, and to better utilize network capacity with real time comprehension of dynamic network characteristic. Heterogeneity of nodes, in terms of capabilities or mobility patterns poses several challenges in de ning a utility function thatts all. Moreover, multi-hop routing protocols generally assume altruistic behavior of nodes. However, this assumption is not always true, as by agreeing to forward messages a node is contributing its resources such as memory, processing power, energy etc. Non-cooperative behavior may reduce e ective node density and can be devastating in opportunistic environments, where intermediary hops are required to share custody of messages. We target these issues in this thesis. In order to addressrst problem, we present a \Multi-Attribute Routing Scheme" (MARS) based on \Simple Multi-Attribute Rating Technique" (SMART) that collects samples of important information about a node''s di erent characteristics. This stochastic picture of a node behavior is then e ectively employed in calculatvii ing its next-hoptness. We also devise a method based on learning rules of neural networks to dynamically determine relative importance of each dimension. Hence, estimations based on an optimized combination of multiple parameters help in taking wiser decisions in relay nodes selection with inherent advantage of e cient utilization of network capacity. In second part of thesis, we analyze the aspect of nodes cooperation in challenged networks. We propose a novel framework to stimulate cooperation among nodes, which is deployed as an overlay to assist Destination-Dependent (DD) utility-based schemes. We envision that such an assistance mechanism to stimulate cooperation among nodes have the potential to help with practical deployments of DD utility schemes in real scenarios a icted with sel sh nodes.
آہ سید صاحب! علم و اخلاق کی دنیا اجڑ گئی رفتی واز رفتینِِ تو عالمے تاریک شد تو مگر شمعی چو رفتی بزم برہم ساختی آہ گذشتہ مہینہ ۲۲؍ نومبر کی رات کو کراچی ریڈیو اسٹیشن سے یہ جانکاہ خبر بجلی بن کر گری کہ حضرت الاستاذ مولانا سید سلیمان ندوی رحمتہ اﷲ علیہ نے ۲۲ اور ۲۳ کی درمیانی شب کو ساڑھے سات بجے اس جہاں فانی کو الوداع کہا، یہ خبر وابستگانِ دامنِ سلیمانی کے لیے ایسی ناگہانی اور ہوش ربا تھی کہ کچھ دیر تک سمجھ میں نہ آتا تھا کہ کیا ہوگیا، مگر مشیت الٰہی پوری ہو کر رہی اور بالآخر یقین کرنا پڑا کہ اس مسیحا نفس نے بھی جان جان آفرین کے سپرد کردی، جو عمر بھر اپنی زبان و قلم سے مردہ دلوں میں روح حیات پھونکتا رہا، اور امراضِ ملت کا وہ ماہر طبیب اٹھ گیا، جس نے اس کے ناتواں جسم میں نئی طاقت و توانائی پیدا کی، وہ چشمۂ فیض خشک ہوگیا جس کی آبیاری سے دین و ملت کا چمن سیراب تھا وہ شیخ کامل اُٹھ گیا، جس نے دلوں کی دنیا منور کی، وہ شمع خاموش ہوگئی، جو نصف صدی تک علم و فن کی ہر مجلس میں ضیا بار رہی، وہ تاجدار رخصت ہوگیا، جس کا سکہ علم و فن کی پوری اقلیم میں رواں تھا، اسلامی علوم کا وہ امام و مجدد اٹھ گیا، جس نے اُن کو نئی زندگی بخشی، مذہب اسلام کا وہ متکلم اور اسلامی تاریخ و تمدن کا وہ محقق اٹھ گیا، جس نے ان کو اُن کی اصل شکل اور نئے لباس میں جلوہ گر کیا، پیغام محمدی کا وہ شارح و ترجمان خاموش ہوگیا، جس نے اپنی بصیرت سے اُس کے اسرار و حکم بے نقاب کئے، اور اس کی ذات جامع الصفات پر علوم کی جامعیت...
The Concept of Collective Ijtihad and Introduction to Prominent Institutions in the Muslim World for resolving contemporary jurisprudential issues is a burning issue these days. Ijtihad is the effort made by the mujtahid in seeking knowledge of the ahkam (rules) of the Shariah through interpretation. It is a known fact the ahkam specifically and explicitly prescribed in the Holy Quran and Sunnah are limited, and as human society evolves, new problems come to the fore. This is the responsibility of mujtahid to present solution of the problems in the light of the rules and principles prescribed in the Holy Quran and Sunnah. This endeavor can take place in three shapes, first by an individual effort of a mujtahid, second by a group of in the form of collective ijtihad while its more advanced shape is the consensus (ijma’a) of all the mujtahidin of the time. In this article all the three modes of ijtihad have been discussed and it has been concluded and suggested that the best option for resolving the issues faced by the Muslim Ummah is collective Ijtihad due its easy implementation. This also helps in avoiding many complications while seeking consensus (Ijma’a) in present day time. In this article a list of the problems have been given which need immediate attention of the Muslim scholars, while in the last part introduction of some prominent institutions of the Muslim World have been given with elaboration of their objectives.
Electroceramics are necessary component in modern technologies of many kinds. In this regard, barium meta-titanate (BaTiO3 or BT) based materials with ABO3 perovskite structure are potential candidates for applications in electronic devices because of their piezoelectric, ferroelectric and optical properties. Barium titanate based materials have attracted significant interest; due to their wide spread applications in wireless communication, space and defense. Barium titanate based ferroelectric materials are suitable for these applications due to their electric field dependent permittivity (εr) and low dielectric loss (tan δ) above Curie temperature (Tc). Ferroelectric materials generally have high dielectric losses, which is due to piezoelectric grain resonance and domain wall motion. It is known that Tc and dielectric properties of BaTiO3 can be systematically changed by chemical substitution at A or B-site by a wide variety of isovalent and aliovalent dopants. The effect of small additives and dopants on the dielectric properties of BaTiO3 based ceramics fabricated by conventional solid state sintering route have been investigated in detail; however, little attention have been given to sol-gel processing of ceramics for dielectric applications. In the present study, the microstructure and dielectric properties of BaTiO3- based ceramics doped with Sr, La, Zr and Mn were investigated in detail. Various compositions [BaTiO3, Ba1-xSrxTiO3 (x = 0.25, 0.35, 0.45, 0.55, 0.65), Ba1-xLaxTi1- x/4O3 (x = 0.00, 0.015, 0.025, 0.035, 0.045, 0.055), Ba0.7Sr0.3Ti1-xZrxO3 (x = 0.02, 0.04, 0.06, 0.08, 0.1), (Ba0.5Sr0.5)Mnx(Ti0.95Fe0.05)1-xO3 (x = 0.00, 0.004, 0.006, 0.008, 0.01, 0.02)] with different stoichiometric ratios were synthesized by using modified sol-gel technique. The dielectric properties of the BaTiO3-based ceramics were studied by making different compositions by substituting the above elements to form solid xvii solutions. Thermal analysis (TG/DTA) was used to trace the synthesis temperature. The temperature range from 750 oC‒900 oC was found suitable for single phase formation of the BaTiO3-based ceramics processed via sol-gel route. The phase and microstructure of the final ceramics were investigated using Xray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Fourier transform infrared spectroscopy (FTIR) was used to investigate the water content and organic functional groups in calcined samples. The dielectric properties were investigated using LCR-meter and impedance analyzer. The tetragonal symmetry (P4mm) of the BaTiO3 ceramics was confirmed by the XRD studies. XRD studies confirmed the tetragonal crystal structure of the x = 0.00 – 0.035 compositions at room temperature of the Ba1-xLaxTi1-x/4O3 ceramic samples. A cubic symmetry (Pm3m) was observed for the x > 0.035 compositions around room temperature. Analysis of the XRD data confirmed the formation of tetragonal (P4mm) phase for all the Ba0.7Sr0.3Ti1-xZrxO3 samples at room temperature. Ceramic samples of the (Ba0.5Sr0.5)Mnx(Ti0.95Fe0.05)1-xO3 showed tetragonal (P4mm) perovskite structure. Microstructure analysis of the thermally etched surface showed a heterogeneous grain growth of the BaTiO3 ceramics. The microstructure investigation revealed that La and Mn substitution acted as growth inhibitor for the BaTiO3- ceramics. Samples doped with Sr and Zr resulted in large grains with a heterogeneous microstructure. Dielectric investigation confirmed that Tc was shifted to low temperatures for the samples doped with Sr, La and Zr, while no obvious changes in the Tc was detected for the samples doped with Mn. Moreover, samples doped with Mn and Zr revealed a diffused phase transition (DPT). The impedance studies confirmed both the grain and grain boundary contributions for the BaTiO3 ceramics. For Sr-doped samples, compositions with x = 0.25 and x = 0.45 showed one xviii semicircle in the capacitance range (≈ 3.4178 × 10-10 F and 5.2016 × 10-10 F, respectively), which was associated with the grain boundary contribution. The samples with x = 0.35, 0.55 and 0.65 showed two semicircles in low and high frequency regimes, which confirmed the bulk and grain boundary contributions to the conduction mechanism. The samples doped with La showed the grain boundary contributions, only. Similarly, Zr and Mn-doped compositions showed both grain boundary and bulk contributions in the conduction mechanisms for all the samples. The total resistance (RT) was observed to decrease with increasing temperature for the pure and Sr, La, Zr and Mn doped BaTiO3 based compositions showing a typical ceramic behaviour.