Self-Powered, Highly Sensitive, High Speed Photodetection Using ITO/WSe2/SnSe2 Vertical Heterojunction

Two dimensional transition metal di-chalcogenides (TMDCs) are promising candidates for ultra-low intensity photodetection. However, the performance of these photodetectors is usually limited by ambience induced rapid performance degradation and long lived charge trapping induced slow response with a large persistent photocurrent when the light source is switched off. Here we demonstrate an indium tin oxide (ITO)/WSe$_2$/SnSe$_2$ based vertical double heterojunction photoconductive device where the photo-excited hole is confined in the double barrier quantum well, whereas the photo-excited electron can be transferred to either the ITO or the SnSe$_2$ layer in a controlled manner. The intrinsically short transit time of the photoelectrons in the vertical double heterojunction helps us to achieve high responsivity in excess of $1100$ A/W and fast transient response time on the order of $10$ $\mu$s. A large built-in field in the WSe$_2$ sandwich layer results in photodetection at zero external bias allowing a self-powered operation mode. The encapsulation from top and bottom protects the photo-active WSe$_2$ layer from ambience induced detrimental effects and substrate induced trapping effects helping us to achieve repeatable characteristics over many cycles

Performance Evaluation of Scheduling Algorithms for Real Time Cloud Computing Systems

Cloud computing shares data and oers services transparently among its users. With the increase in number of users of cloud the tasks to be scheduled increases. The performance of cloud depends on the task scheduling algorithms used in the scheduling components or brokering components. Scheduling of tasks on cloud computing systems is one of the research problem, Where the matching of machines and completion time of the tasks are considered. Tasks matching of machines problem is that, assume number of active hosts are Y, number of VMs in each host are Z. Maximum number of possible Virtual Machines(VMs) to schedule a single task is (y*z). If we need to schedule X tasks, number of possibilities are (y *z)^x. So scheduling of tasks is NP Hard problem. NP Hard means this scheduling of tasks on VMs not having polynomial time complexity, but it may have algorithm for verifying solution. Fault-tolerance becomes an important key to establish dependability in cloud computing system. In task scheduling, if task not completed in it's deadline ,then it is one type of fault in scheduling of tasks. In this thesis this type of faults are taken and try to overcome it. In this thesis we present a non-preemptive scheduling algorithm, By inserting the ideal time for postponing the task by ensuring the other task will completes its execution with in the deadline. In simulation the proposed algorithm maximizes the prot of 25%, throughput of 25% and minimizes the penalty of 20% over EDF

Experimental Study of Cooperative Communication Using Software Defined Radios

The aim of this thesis is to implement and test a real time wireless communication environment. Cooperative Communication is one of the methods by which a reliable communication can be obtained. This is performed using a Software Defined Radio. The received output is compared with the actual signal that is transmitted over the wireless channel. The wireless communications are often hindered by the noisy environments and make the system unreliable. The interference from neighboring nodes also poses a major disadvantage. There is a necessity to improve the performance of the system where the neighbor nodes can work in coordination with the sender. The intermediate nodes (also called as relay stations) cooperate in a distributed manner to prevent loss of bandwidth usag

Development and Evaluation of Brain Tumor Targeted Liposome Delivery System for Paclitaxel

Primary brain tumors are a relatively common cause of cancer-related deaths. High-grade gliomas are the most common type of primary brain cancer, and the affected patients have a median survival of less than 1 year. Almost all malignant gliomas are incurable with the present standards of healthcare. Currently accepted therapeutic adjuvants to surgery, such as radiotherapy and chemotherapy, provide only a minor improvement in the disease course and life expectancy for patients diagnosed with malignant gliomas. Often, chemotherapy has failed to make any significant impact on the prognosis of disease because of significant local and systemic toxicity, problems with transport of the drug across the blood brain barrier (BBB), and a high degree of chemoresistance demonstrated by tumor cells. Newer targeted delivery systems with more specificity for gliomas, improved safety profiles, and an enhanced ability to permeate through the BBB are actively under development as the next generation glioma therapies. Blood brain barrier and vascular endothelial cells in and around glioma brain tumors highly express certain receptors such as transferrin for iron transport into brain tumors respectively. To explore the potential of this tumor induced expression of transferrin receptors for targeting drug carriers, in this study, I have developed and characterized liposome carriers containing paclitaxel, for targeted delivery to the glioma brain tumors. A liposome drug delivery system specifically aimed at glioma tumors was designed in this study. Liposomes composed of egg phosphotidylchole (EPC), hydrogenated soybean phosphatidylcholine (HSPC), cholesterol, distearoyl phosphoethanolamine-PEG-2000 conjugate (DSPE-PEG) and DSPE-PEG-biotin were prepared by the lipid film hydration and extrusion process. Transferrin (Tf) with affinity for transferrin receptors over-expressed on blood brain barrier and glioma tumor vasculature were coupled to the distal end of poly ethylene glycol coated long circulating liposomes. The liposome delivery system was characterized in terms of size, lamellarity, ligand density, and drug loading properties. The effect of lipid concentration and type in the formulation on paclitaxel loading in the liposomes was studied. Functional properties of the delivery system were evaluated for, i) in vivo blood circulation time using blood sampling method and also using a novel intravital microscopic method, ii) Selective tumor localization in both flank and intracranial glioma models, and iii) anti-tumor efficacy in mouse flank and intracranial glioma tumors. Further, in order to improve physical and chemical stability of the delivery system and hence enhance its shelf life, a lyophilized formulation and process were developed. Light scattering and electron microscopic observations of the formulations revealed presence of small unilamellar liposomes of about 133 nm in diameter. High performance gel filtration chromatography determinations of ligand coupling to the liposome surface indicated that about 72% of the transferrins were conjugated with biotin groups on the liposome surface. Optimized liposome formulation with 100 mM lipid concentration, 1:33 drug-to-lipid ratio, 5 mol% cholesterol, 5 mol% DSPE-PEG, and 0.01 mol% DSPE-PEG-biotin content yielded 1.3 ± 0.2 mg/mL liposomal paclitaxel with 97.2 ± 3% of the drug being entrapped in the liposomes. These liposomes released no significant amount of the encapsulated drug over 72 hrs at 37°C. Targeted liposomes showed significantly higher rate and extent of tumor accumulation in glioma flank tumors in vivo compared to non-targeted liposomes. Targeted liposomes also possessed long circulating properties with a T1/2 of about 9 hrs in mice. This increased circulation longevity, attributed to steric stabilization effects of PEG, enhanced target accumulation. Near infrared fluorescence imaging demonstrated that these liposomes accumulated selectively in flank tumors with tumor targeting index of 10.59 ± 1.08. Paclitaxel incorporated into the targeted liposomes delayed tumor growth by 7.7 days in 5 doses of 2 mg/Kg body weight. However, no significant tumor growth retardation was observed when paclitaxel was administered in free form (Cremophor EL solubilized form) at similar dose. A process and formulation were developed for freeze-drying the targeted liposome delivery system. Liposome formulations stabilized with 15% sucrose outside the liposomes were able to maintain particle size distribution and drug loading close to initial upon freeze-drying and rehydration. A stable and effective targeted liposome delivery system was developed for paclitaxel to take this drug selectively to glioma brain tumors. This targeted delivery system could potentially improve therapeutic benefits of anticancer drugs with and increase safety when compared to existing solution dosage forms

Performance Comparision between Capacitor Clamped and Hybrid Multi Level Inverters

The ability to operate at medium and high voltages with reduced dv/dt across the switches, multi level inverters has given more interest in industrial applications. For the realization of multilevel inverters conventionally various topologies have been proposed. In order to minimize switching elements, losses, size and cost, different hybrid structures have been introduced. In this paper the operation performance of traditional capacitor clamped (Flying Capacitor) and hybrid topology of five level multi level inverters are compared. The results reveal that the total harmonic distortion in the stator current, phase voltage and line voltage is less in hybrid topology than capacitor clamped topology. The simulation is done in MATLAB-Simulink

Seismic Lateral Earth Pressures on Retaining Structures

Various methods are available to estimate seismic earth pressures on soil retaining structures which cane be grouped to experimental, analytical and numerical methods. 1G model shaking table studies or high-g level centrifuge model shaking studies give some insight on the variation of seismic earth pressures along height of the retaining structure. In the simple analytical methods, M-O method based pseudo-static analysis is extensively used to evaluate seismic earth pressure variation and its probable resultant location. Pseudodynamic analysis method based analyses are also developed and are in progress for the same. Besides, these experimental and analytical methods, FEM or FDM based numerical simulations of the retaining structures provide much information on the seismic lateral earth pressure variation. In this paper, the methods available and the procedures to be followed to determine the lateral seismic earth pressures and their recent developments are summarized. Numerical simulations of seismic behavior of cantilever retaining walls was performed using FLAC and the results obtained regarding seismic earth pressures are discussed

microstructural and thermophysical properties of uo2-mo composite reactor fuels

Nuclear fuel performance under normal operating conditions and extreme accident conditions have studied using experimental procedures to investigate the microstructural and thermophysical properties of the fuel. Attention has been drawn to the catastrophic nuclear power station accident at the Fukushima Daiichi in Japan. After the reactor system's failure, efforts are focused on preventing the existing nuclear fuel, uranium dioxide (UO2), and zirconium (Zr), system from melting. Research is required to replace the fuel and clad system with a more robust system that can withstand accidents. With the recognition of associated risks with the current fuel, hence, developing an accident-tolerant fuel (ATF) became a major motivation for research. In this work, Molybdenum (Mo) has been deployed as an additive material in UO2 fuel due to its high thermal conductivity, high boiling point, high melting point, and low thermal neutron absorption cross-section. The nuclear reactor safety analysis showed that thermal conductivity is an essential property of fuel because it regulates fuel operating temperature and therefore influences the safety of reactor operation. Low thermal conductivity leads to the rapid meltdown at the core of the fuel pellet during the loss of coolant scenario. Apart from thermal conductivity, pellet microstructure and density also played an essential role in fission gas buildup and release, the accumulation of the fission gas in form of voids in the center of fuel pellets. Therefore, three major critical areas of focus have been identified in this research: i) Enhanced thermal conductivity of UO2-Mo composite fuel for high-temperature accident scenarios, ii) Evaluation of the pellet microstructure, grain size, texture, and grain boundary character distribution in UO2-Mo composites, and iii) Optimizing the high densification of the UO2-Mo composite fuel pellets. One of the limitations of the accident-tolerant fuel has the difficulty of processing dense pellets by the conventional sintering methods. Hence the fabricating of UO2-Mo composite fuels by spark plasma sintering (SPS) was proposed, and the effect of the sintering parameters on the density, microstructure, and thermal conductivity of UO2-Mo composite fuel have established. Finally, a composite fuel of UO2-Mo (micro and nano particles) has been manufactured with enhanced thermal conductivity