Investigation of drilling performance and penetration mechanism using passive vibration assisted rotary drilling technology

Drilling performance is an essential goal in the petroleum and mining industry. Drilling Rate of Penetration (ROP) is influenced by the operating parameter: torque, Weight on Bit (WOB), fluid flow rate, Revolution per Minute (rpm), rock related parameters (rock type, rock homogeneousness, rock anisotropy orientation), and mechanical parameters (bit type, configuration of the Bottom Hole Assembly (BHA)). The Drilling Technology Laboratory (DTL) at Memorial University of Newfoundland has incorporated the passive Vibration Assisted Rotational Drilling Technology (pVARD) as a drilling tool. This tool includes three parts within a compliant part, a part that dampens and a torque transmitting unit that is inside the BHA of the drill string. This tool utilizes the natural vibrations of the drilling process to increase drilling efficiency and rate of penetration. In this thesis, laboratory and field drilling tests have been conducted by first and second generation pVARD tools respectively which could play a positive role in improving drilling penetration rate through modified bit-rock compliance from conventional drilling. This research aims to develop a fundamental guideline for rock strength measurement and to interlink mechanical tests for the purpose of evaluating drilling performance. The compressive rock strength has an inverse relationship with drilling efficiency. The average Unconfined Compressive Strength (UCS) and Indirect Tensile Strength (ITS) of the granite were obtained to be 168.4 MPa and 16.3 MPa respectively by the mechanical loading frame in the laboratory parameters following American Society for Testing and Materials (ASTM) standard. The pVARD operational details are important for optimal configuration and best drilling results. The study focused on designing pVARD to be consistent with a Large Drilling Simulator (LDS) selecting optimal Belleville springs. Compression tests and numerical studies have been carried out using a mechanical frame and simulation analysis respectively, for different Belleville Spring stacking scenarios. Mechanical and simulation studies with details of pre-planned drilling experiments can provide important guidelines for optimizing pVARD basics. The hysteresis effect analysis of LDS-pVARD springs also provided a coherent idea of energy dissipation during the cycle test. Depending on the rock type and drilling parameters can provide pre-settings and configurations of pVARD for optimal drilling performance. Finally, this dissertation focuses on the effects of vibration on the performance of a diamond coring bit when drilling on hard rock with a first-generation small lab scale vibration tool pVARD. Thereafter, Drill off Tests (DOTs) have been performed using a Small Drilling Simulator (SDS) with axial vibrations on the drill string in laboratory conditions. The vibration properties have been adjusted to various settings of spring compliance and dampening (rubber) material. The results of the evaluation of the experimental data show that the ROP increased by a maximum of 28% keeping WOB within the operational limits. The results and knowledge obtained from this study will help to design third generation pVARD tools

Physico-chemical properties and toxicological effects on plant and algal models of carbon nanosheets from a nettle fibre clone.

peer reviewedCarbon nanosheets are two-dimensional nanostructured materials that have applications as energy storage devices, electrochemical sensors, sample supports, filtration membranes, thanks to their high porosity and surface area. Here, for the first time, carbon nanosheets have been prepared from the stems and leaves of a nettle fibre clone, by using a cheap and straight-forward procedure that can be easily scaled up. The nanomaterial shows interesting physical parameters, namely interconnectivity of pores, graphitization, surface area and pore width. These characteristics are similar to those described for the nanomaterials obtained from other fibre crops. However, the advantage of nettle over other plants is its fast growth and easy propagation of homogeneous material using stem cuttings. This last aspect guarantees homogeneity of the starting raw material, a feature that is sought-after to get a nanomaterial with homogeneous and reproducible properties. To evaluate the potential toxic effects if released in the environment, an assessment of the impact on plant reproduction performance and microalgal growth has been carried out by using tobacco pollen cells and the green microalga Pseudokirchneriella subcapitata. No inhibitory effects on pollen germination are recorded, while algal growth inhibition is observed at higher concentrations of leaf carbon nanosheets with lower graphitization degree

Inflammatory mechanisms in ischemic stroke: therapeutic approaches

Acute ischemic stroke is the third leading cause of death in industrialized countries and the most frequent cause of permanent disability in adults worldwide. Despite advances in the understanding of the pathophysiology of cerebral ischemia, therapeutic options remain limited. Only recombinant tissue-plasminogen activator (rt-PA) for thrombolysis is currently approved for use in the treatment of this devastating disease. However, its use is limited by its short therapeutic window (three hours), complications derived essentially from the risk of hemorrhage, and the potential damage from reperfusion/ischemic injury. Two important pathophysiological mechanisms involved during ischemic stroke are oxidative stress and inflammation. Brain tissue is not well equipped with antioxidant defenses, so reactive oxygen species and other free radicals/oxidants, released by inflammatory cells, threaten tissue viability in the vicinity of the ischemic core. This review will discuss the molecular aspects of oxidative stress and inflammation in ischemic stroke and potential therapeutic strategies that target neuroinflammation and the innate immune system. Currently, little is known about endogenous counterregulatory immune mechanisms. However, recent studies showing that regulatory T cells are major cerebroprotective immunomodulators after stroke suggest that targeting the endogenous adaptive immune response may offer novel promising neuroprotectant therapies

2017 HRS/EHRA/ECAS/APHRS/SOLAECE expert consensus statement on catheter and surgical ablation of atrial fibrillation: executive summary.

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Search for top squark pair production in pp collisions at root s=13 TeV using single lepton events

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Search for supersymmetry in proton-proton collisions at 13 TeV using identified top quarks

A search for supersymmetry is presented based on proton-proton collision events containing identified hadronically decaying top quarks, no leptons, and an imbalance p(T)(miss) in transverse momentum. The data were collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 35.9 fb(-1). Search regions are defined in terms of the multiplicity of bottom quark jet and top quark candidates, the p(T)(miss) , the scalar sum of jet transverse momenta, and themT2 mass variable. No statistically significant excess of events is observed relative to the expectation from the standard model. Lower limits on the masses of supersymmetric particles are determined at 95% confidence level in the context of simplified models with top quark production. For a model with direct top squark pair production followed by the decay of each top squark to a top quark and a neutralino, top squark masses up to 1020 GeVand neutralino masses up to 430 GeVare excluded. For amodel with pair production of gluinos followed by the decay of each gluino to a top quark-antiquark pair and a neutralino, gluino masses up to 2040 GeVand neutralino masses up to 1150 GeVare excluded. These limits extend previous results.Peer reviewe

Search for resonances in the mass spectrum of muon pairs produced in association with b quark jets in proton-proton collisions at root 8 and 13 TeV

A search for resonances in the mass range 12-70 GeV produced in association with a b quark jet and a second jet, and decaying to a muon pair, is reported. The analysis is based on data from proton-proton collisions at center-of-mass energies of 8 and 13 TeV, collected with the CMS detector at the LHC and corresponding to integrated luminosities of 19.7 and 35.9 fb(-1), respectively. The search is carried out in two mutually exclusive event categories. Events in the first category are required to have a b quark jet in the central region (|| 2.4) and at least one jet in the forward region (|| > 2.4). Events in the second category are required to have two jets in the central region, at least one of which is identified as a b quark jet, no jets in the forward region, and low missing transverse momentum. An excess of events above the background near a dimuon mass of 28 GeV is observed in the 8 TeV data, corresponding to local significances of 4.2 and 2.9 standard deviations for the first and second event categories, respectively. A similar analysis conducted with the 13 TeV data results in a mild excess over the background in the first event category corresponding to a local significance of 2.0 standard deviations, while the second category results in a 1.4 standard deviation deficit. The fiducial cross section measurements and 95% confidence level upper limits on those for a resonance consistent with the 8 TeV excess are provided at both collision energies

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

Search for Evidence of the Type-III Seesaw Mechanism in Multilepton Final States in Proton-Proton Collisions at root s=13 TeV

Peer reviewe

Search for Higgsino pair production in pp collisions at root s=13 TeV in final states with large missing transverse momentum and two Higgs bosons decaying via H -> b(b)over bar

Results are reported from a search for new physics in 13 TeV proton-proton collisions in the final state with large missing transverse momentum and two Higgs bosons decaying via H -> b(b)over bar. The search uses a data sample accumulated by the CMS experiment at the LHC in 2016, corresponding to an integrated luminosity of 35.9 fb(-1). The search is motivated by models based on gauge-mediated supersymmetry breaking, which predict the electroweak production of a pair of Higgsinos, each of which can decay via a cascade process to a Higgs boson and an undetected lightest supersymmetric particle. The observed event yields in the signal regions are consistent with the standard model background expectation obtained from control regions in data. Higgsinos in the mass range 230-770 GeV are excluded at 95% confidence level in the context of a simplified model for the production and decay of approximately degenerate Higgsinos.Peer reviewe