PUBLIC BLOCKCHAIN SCALABILITY: ADVANCEMENTS, CHALLENGES AND THE FUTURE

In the last decade, blockchain has emerged as one of the most influential innovations in software architecture and technology. Ideally, blockchains are designed to be architecturally and politically decentralized, similar to the Internet. But recently, public and permissionless blockchains such as Bitcoin and Ethereum have faced stumbling blocks in the form of scalability. Both Bitcoin and Ethereum process fewer than 20 transactions per second, which is significantly lower than their centralized counterpart such as VISA that can process approximately 1,700 transactions per second. In realizing this hindrance in the wide range adoption of blockchains for building advanced and large scalable systems, the blockchain community has proposed first- and second-layer scaling solutions including Segregated Witness (Segwit), Sharding, and two-way pegged sidechains. Although these proposals are innovative, they still suffer from the blockchain trilemma of scalability, security, and decentralization. Moreover, at this time, little is known or discussed regarding factors related to design choices, feasibility, limitations and other issues in adopting the various first- and second-layer scaling solutions in public and permissionless blockchains. Hence, this thesis provides the first comprehensive review of the state-of-the-art first- and second-layer scaling solutions for public and permissionless blockchains, identifying current advancements and analyzing their impact from various viewpoints, highlighting their limitations and discussing possible remedies for the overall improvement of the blockchain domain

Theoretical and experimental analysis of the thermoacoustic refrigeration

The thermoacoustic theory is studied in detail and its application to refrigeration is analyzed. This new refrigerator which uses resonant high amplitude sound in inert gases to pump heat will be described. It will be seen that without any moving parts, except the driver (speaker diaphragm), this refrigerator is as efficient as other refrigeration systems. An experiment is designed with all the major parts manufactured and fabricated in the lab. The results of the experiments are seriously effected due to the leakage of helium. Detailed recommendations are made which will help prevent similar design problems. In addition, numerical simulation was performed using a FORTRAN program to examine the variation of various parameters with frequency and acoustic pressure

Numaerical Solution of Three Dimensionsl Conjugate Heat Transfer in a Microchannel Heat Sink and CFD Analysis

In electronic equipments, thermal management is indispensable for its longevity and hence, it is one of the important topics of current research. The dissipation of heat is necessary for the proper functioning of these instruments. The heat is generated by the resistance encountered by electric current. This has been further hastened by the continued miniaturization of electronic systems which causes increase in the amount of heat generation per unit volume by many folds. Unless proper cooling arrangement is designed, the operating temperature exceeds permissible limit. As a consequence, chances of failure get increased. Increasing circuit density is driving advanced cooling systems for the next generation microprocessors. Micro-Channel heat exchangers (MHE) in silicon substrates are one method that is receiving considerable attention. These very fine channels in the heat exchanger provide greatly enhanced convective heat transfer rate and have been shown to be able to meet the demands of the cooling challenge for the microprocessors for many generations to come. This work focused on laminar flow (Re < 200) within rectangular micro-channel with hydraulic diameter 86μm for single-phase liquid flow. The influence of the thermophysical properties of the fluid on the flow and heat transfer, are investigated by evaluating thermo-physical properties at a reference bulk temperature. The micro-heat sink model consists of a 10 mm long silicon substrate, with rectangular micro-channels,57μm wide and 180μm deep, fabricated along the entire length. Water at 293k is taken as working fluid. The results indicate that thermo-physical properties of the liquid can significantly influence both the flow and heat transfer in the micro-channel. Assumption of hydrodynamic, fully developed laminar flow is valid here on basis of Langhaar’s equation. The local heat transfer coefficient and averaged Nusselt number is calculated and plotted for pressure drop of 50kpa, 30kpa and 10kpa. The result is verified for heat flux 50w/cm2, 90w/cm2 and 150w/cm . A three-dimensional Computational Fluid Dynamics (CFD) model was built using the commercial package, GAMBIT-FLUENT, to investigate the conjugate fluid flow and heat transfer phenomen

A non-sequential phase detector for low jitter clock recovery applications

Master of ScienceDepartment of Electrical and Computer EngineeringAndrew RysClock and data recovery (CDR) circuits form the backbone of high speed receivers. These receivers are used in various applications such as chip to chip interconnects, optical communications and backplane routing. The received data in CDR circuits are potentially noisy and asynchronous, i.e. they are not accompanied by a clock. The CDR circuit has to generate a clock from the data and then retime the data. The CDR circuit that recovers the clock and retimes the data has to remove the jitter that is accumulated during its transport through channels due to inter symbol interference (ISI). There are stringent jitter specifications defined by various communication standards that must be addressed by CDR circuits. These make the design of CDR circuits more difficult for system designers as well the circuit designer. Many parameters have to be taken into consideration while designing a CDR circuit. The problem becomes even more interesting as there are various tradeoffs in the design. As speeds of communications increase, the maximum allowable jitter decreases. Jitter in CDR circuits arises due to a lot of factors and is also dependent on the method used for clock and data recovery. In CDR circuits that use phase locked loops to recover the clock and retime the data, jitter may be caused by the metastability of sequential elements used in phase detectors. Jitter is also caused by the phase noise of the VCO used in the PLL. In CDR circuits that use the delay locked loop to recover the clock and data, jitter may be caused by the metastability of sequential elements in phase detectors as well as the quality of reference clock that is used to re-time the data. Additional effects that can cause jitter in CDR circuits include the use of spread spectrum clocking, delta sigma noise shaping performance, etc. In this thesis a non-sequential linear phase detector has been proposed which does not use any sequential elements to avoid metastability issues in phase detectors. The output jitter in a CDR circuit that uses the proposed phase detector is measured and compared to a Hogge Phase Detector [5]

Disentangling of incomplete fusion dynamics at low energies ≈ 4-6 MeV/A

An experiment has been performed for the measurements of forward recoil range distributions (FRRDs) of evaporation residues (ERs) using 16O beam on the target 148Nd to explore the incomplete fusion (ICF) dynamics at low projectile energy ≈ 4-6 MeV/A. In the present work, FRRDs of ERs 159,158Er(xn), 160g,159Ho(pxn), 157,155Dy(αxn) and 155Tb(αpxn) have been measured. The measured FRRDs of ERs have been compared with their theoretical mean ranges, calculated using code SRIM. These present results obtained from FRRDs measurements show that full and partial linear momentum transfer components are involved. This indicates that the ERs populated through α-emission channels are not only produced via complete fusion, but also through incomplete fusion dynamics. The present analysis indicates that the incomplete fusion contribution increases with projectile energy. This increment in incomplete fusion contribution is due to the increase in breakup probability of projectile 16O into 12C + 4He/ α with projectile energy

Disentangling of incomplete fusion dynamics at low energies ≈ 4-6 MeV/A

371-375An experiment has been performed for the measurements of forward recoil range distributions (FRRDs) of evaporation residues (ERs) using 16O beam on the target 148Nd to explore the incomplete fusion (ICF) dynamics at low projectile energy ≈ 4-6 MeV/A. In the present work, FRRDs of ERs 159,158Er(xn), 160g,159Ho(pxn), 157,155Dy(αxn) and 155Tb(αpxn) have been measured. The measured FRRDs of ERs have been compared with their theoretical mean ranges, calculated using code SRIM. These present results obtained from FRRDs measurements show that full and partial linear momentum transfer components are involved. This indicates that the ERs populated through α-emission channels are not only produced via complete fusion, but also through incomplete fusion dynamics. The present analysis indicates that the incomplete fusion contribution increases with projectile energy. This increment in incomplete fusion contribution is due to the increase in breakup probability of projectile 16O into 12C + 4He/ α with projectile energy

Prolonged In Vivo Retention of a Cathepsin D Targeted Optical Contrast Agent in a Mouse Model of Alzheimer\u27s Disease.

BACKGROUND: Cathepsin D (CatD) is a lysosomal protease that is elevated early in Alzheimer\u27s disease (AD). We have previously developed a Targeted contrast agent (CA) to detect CatD activity in vivo, consisting of a magnetic resonance imaging/fluorescent moiety linked to a cell penetrating peptide (CPP) by means of a CatD cleavage site and have demonstrated its uptake in the brain of an AD mouse model. OBJECTIVE: The purpose of this study was to characterize the in vivo retention of a near infra-red fluorescent dye labeled version of this CA. METHODS: Six adult C57Bl/6 wild-type mice and six adult 5XFAD transgenic AD mice were studied using a small animal imaging system at five and twelve months of age using our novel Targeted CA, or two different control CAs; a Non-Targeted (lacking the CatD cleavage site) and a Non-Penetrating (lacking the CPP). Following intravenous CA administration, the optical signal was recorded within the brain and uptake and washout curves were measured and fitted to a one-phase exponential decay curve. RESULTS: In all wild-type and 5XFAD mice, the washout of the Targeted CA that included a CPP domain was significantly slower than the washout of the Non-Penetrating and Non-Targeted CA. Furthermore, the washout of the CatD Targeted CA was significantly slower in the 5XFAD mice compared to the age matched wild-type controls (p \u3c  0.05) at 5 and 12 months of age. Control CAs showed no differences in washout. CONCLUSIONS: The prolonged retention of the CatD targeted CA in 5XFAD mice suggests this agent may be useful for AD detection

Effect of projectile breakup in the system 19F + 154Sm

386-391An attempt was made to understand the role of various entrance channel parameters on incomplete fusion dynamics by the measurements of excitation functions of evaporation residues populated via complete and incomplete fusion dynamics in the system 19F + 154Sm at projectile energy &asymp; 4-6 MeV/A. The stacked foil activation technique followed by offline gamma ray spectrometry was employed in these measurements. The measured excitation functions of various evaporation residues populated have been analyzed within the framework of statistical model code PACE-4. It has been observed that the measured excitation functions of xn and pxn emission channels agree well with the theoretical predictions of PACE-4. On the other hand, the measured excitation functions of &alpha;-emission channels have been found significantly enhanced over their theoretical predictions. This enhancement may be attributed to the incomplete fusion of the projectile 19F as the calculations for incomplete fusion are not included in statistical model calculations. The incomplete fusion fraction has been deduced from the present measurements. Further, a systematic study has also been performed, which shows that the incomplete fusion increases significantly with entrance channel mass asymmetry at low projectile energy, differently for different projectiles

Effect of projectile breakup in the system 19F + 154Sm

An attempt was made to understand the role of various entrance channel parameters on incomplete fusion dynamics by the measurements of excitation functions of evaporation residues populated via complete and incomplete fusion dynamics in the system 19F + 154Sm at projectile energy ≈ 4-6 MeV/A. The stacked foil activation technique followed by offline gamma ray spectrometry was employed in these measurements. The measured excitation functions of various evaporation residues populated have been analyzed within the framework of statistical model code PACE-4. It has been observed that the measured excitation functions of xn and pxn emission channels agree well with the theoretical predictions of PACE-4. On the other hand, the measured excitation functions of α-emission channels have been found significantly enhanced over their theoretical predictions. This enhancement may be attributed to the incomplete fusion of the projectile 19F as the calculations for incomplete fusion are not included in statistical model calculations. The incomplete fusion fraction has been deduced from the present measurements. Further, a systematic study has also been performed, which shows that the incomplete fusion increases significantly with entrance channel mass asymmetry at low projectile energy, differently for different projectiles