Two-point bend studies of glass fibers

The principal objective of this research is to advance our understanding of how glass breaks. Glass, a material well known for its brittleness, has been used widely but within a frustrating limit of its strength. Generally, strength is not considered as an intrinsic property of glass, due to the difficulty of avoiding the presence of flaws on the sample surface. The fiber drawing system and two-point bending (TPB) equipment developed at Missouri S&T allow the fabrication of pristine glass fibers and failure strain measurements while minimizing the effects of strength limiting critical flaws. Several conditions affect the failure behavior of glasses, including glass composition, thermal history of melts and environmental conditions during the failure tests. Understanding how these conditions affect failure helps us understand how glass fails. In this dissertation, failure strains for many different silicate and borate glasses were measured under a variety of experimental conditions. Failure stresses for various silicate glasses were calculated using values of the nonlinear elastic moduli reported in the literature. Inert intrinsic strengths for alkali silicate glasses were related to the structure and corresponding bond strengths, and the dependence of the inert strengths on faceplate velocity is discussed. Inert failure strains were also obtained for sodium borate glasses. Up to ~40% failure strain was measured for vitreous B₂O₃. The addition of soda to boron oxide increases the dimensionality and connectivity of the glass structure and hence increases its resistance to deformation, as was observed in elasticity and brittleness measurements reported in the literature. The increase in deformation resistance produces lower failure strains, a behavior also seen for alkali silicate and aluminosilicate glasses where the reduction of non-bridging oxygen increases the structure stiffness and leads to lower inert failure strain. Fatigue effects on silicate glasses were studied by measuring the failure strains in water at different temperatures and at different loading rates, and in air with a range of relative humidities. The dominant fatigue reaction for cross-linked network glasses is bond hydrolysis, whereas for alkali modified depolymerized glasses is ion-exchange reaction between alkali ions and water species. The fatigue mechanism difference results in the difference in the humidity sensitivity of the reaction rate. The dominant fatigue reaction also changes at around 50% relative humidity --Abstract, page iv

Fast and efficient user pairing and power allocation algorithm for non-orthogonal multiple access in cellular networks

Non-orthogonal multiple access (NOMA) is emerging as a promising multiple access technology for the fifth generation cellular networks to address the fast growing mobile data traffic. It applies superposition coding in transmitters, allowing simultaneous allocation of the same frequency resource to multiple intra-cell users. Successive interference cancellation is used at the receivers to cancel intra-cell interference. User pairing and power allocation (UPPA) is a key design aspect of NOMA. Existing UPPA algorithms are mainly based on exhaustive search method with extensive computation complexity, which can severely affect the NOMA performance. A fast proportional fairness (PF) scheduling based UPPA algorithm is proposed to address the problem. The novel idea is to form user pairs around the users with the highest PF metrics with pre-configured fixed power allocation. Systemlevel simulation results show that the proposed algorithm is significantly faster (seven times faster for the scenario with 20 users) with a negligible throughput loss than the existing exhaustive search algorithm

Capacitive Properties and Structure of RuO₂-HfO₂ Films Prepared by Thermal Decomposition Method

Binary RuO2-HfO2 films on Ti substrates were prepared by a thermal decomposition method. cyclic voltammetric and charge/discharge properties of the RuO2-HfO2 electrodes were characterized. It was determined that the incorporation of HfO2 into RuO 2 greatly improved the capacitive properties of the material. The RuO2-HfO2 electrodes showed excellent cyclic stability, with no decay in charge capability during 1000 CV cycles in acidic solution. A nominal content of 50 mol% RuO2 and 50 mol% HfO2 gave the highest specific capacitance of 789.3 F/g (RuO2). The excellent capacitive properties and stability were related to the hydrous amorphous mixed-oxides formed in the film. This work proves that high capacitive performance of RuO2-based electrode materials can be obtained by thermal decomposition, even with the retained chloride in the film

Capacitive Properties and Structure of RuO₂-HfO₂ Films Prepared by Thermal Decomposition Method

Binary RuO2-HfO2 films on Ti substrates were prepared by a thermal decomposition method. cyclic voltammetric and charge/discharge properties of the RuO2-HfO2 electrodes were characterized. It was determined that the incorporation of HfO2 into RuO 2 greatly improved the capacitive properties of the material. The RuO2-HfO2 electrodes showed excellent cyclic stability, with no decay in charge capability during 1000 CV cycles in acidic solution. A nominal content of 50 mol% RuO2 and 50 mol% HfO2 gave the highest specific capacitance of 789.3 F/g (RuO2). The excellent capacitive properties and stability were related to the hydrous amorphous mixed-oxides formed in the film. This work proves that high capacitive performance of RuO2-based electrode materials can be obtained by thermal decomposition, even with the retained chloride in the film

Diffractive D_s production in charged current DIS

We present a perturbative QCD calculation of diffractive $D_s$ production in charged current deep inelastic scattering. In the two-gluon exchange model, we analyze the diffractive process \nu N \to \mu^- N \Ds, which may provide useful information for the gluon structure of nucleons and the diffraction mechanism in QCD. The cross section of diffractive $D_s$ production with \xBj=0.005-0.05 and $E_\nu=50$ Gev is found to be $2.7\times10^{-5}$ pb. In spite of this small cross section, the high luminosity available at the $\nu$-Factory in the future would lead to a sizable number of diffraction events.Comment: 6 pages, 5 eps figures, final version to appear in PL

Modelling the geographical spread of HIV among MSM in Guangdong, China: a metapopulation model considering the impact of pre-exposure prophylaxis

Men who have sex with men (MSM) make up the majority of new human immunodeficiency virus (HIV) diagnoses among young people in China. Understanding HIV transmission dynamics among the MSM population is, therefore, crucial for the control and prevention of HIV infections, especially for some newly reported genotypes of HIV. This study presents a metapopulation model considering the impact of pre-exposure prophylaxis (PrEP) to investigate the geographical spread of a hypothetically new genotype of HIV among MSM in Guangdong, China. We use multiple data sources to construct this model to characterize the behavioural dynamics underlying the spread of HIV within and between 21 prefecture-level cities (i.e. Guangzhou, Shenzhen, Foshan, etc.) in Guangdong province: the online social network via a gay social networking app, the offline human mobility network via the Baidu mobility website, and self-reported sexual behaviours among MSM. Results show that PrEP initiation exponentially delays the occurrence of the virus for the rest of the cities transmitted from the initial outbreak city; hubs on the movement network, such as Guangzhou, Shenzhen, and Foshan are at a higher risk of 'earliest' exposure to the new HIV genotype; most cities acquire the virus directly from the initial outbreak city while others acquire the virus from cities that are not initial outbreak locations and have relatively high betweenness centralities, such as Guangzhou, Shenzhen and Shantou. This study provides insights in predicting the geographical spread of a new genotype of HIV among an MSM population from different regions and assessing the importance of prefecture-level cities in the control and prevention of HIV in Guangdong province. This article is part of the theme issue 'Data science approach to infectious disease surveillance'

Actively implementing an evidence-based feeding guideline for critically ill patients (NEED): a multicenter, cluster-randomized, controlled trial

Background: Previous cluster-randomized controlled trials evaluating the impact of implementing evidence-based guidelines for nutrition therapy in critical illness do not consistently demonstrate patient benefits. A large-scale, sufficiently powered study is therefore warranted to ascertain the effects of guideline implementation on patient-centered outcomes. Methods: We conducted a multicenter, cluster-randomized, parallel-controlled trial in intensive care units (ICUs) across China. We developed an evidence-based feeding guideline. ICUs randomly allocated to the guideline group formed a local "intervention team", which actively implemented the guideline using standardized educational materials, a graphical feeding protocol, and live online education outreach meetings conducted by members of the study management committee. ICUs assigned to the control group remained unaware of the guideline content. All ICUs enrolled patients who were expected to stay in the ICU longer than seven days. The primary outcome was all-cause mortality within 28 days of enrollment. Results: Forty-eight ICUs were randomized to the guideline group and 49 to the control group. From March 2018 to July 2019, the guideline ICUs enrolled 1399 patients, and the control ICUs enrolled 1373 patients. Implementation of the guideline resulted in significantly earlier EN initiation (1.20 vs. 1.55 mean days to initiation of EN; difference − 0.40 [95% CI − 0.71 to − 0.09]; P = 0.01) and delayed PN initiation (1.29 vs. 0.80 mean days to start of PN; difference 1.06 [95% CI 0.44 to 1.67]; P = 0.001). There was no significant difference in 28-day mortality (14.2% vs. 15.2%; difference − 1.6% [95% CI − 4.3% to 1.2%]; P = 0.42) between groups. Conclusions: In this large-scale, multicenter trial, active implementation of an evidence-based feeding guideline reduced the time to commencement of EN and overall PN use but did not translate to a reduction in mortality from critical illness. Trial registration: ISRCTN, ISRCTN12233792. Registered November 20th, 2017

Actively implementing an evidence-based feeding guideline for critically ill patients (NEED): a multicenter, cluster-randomized, controlled trial (vol 26, 46, 2022)

BackgroundPrevious cluster-randomized controlled trials evaluating the impact of implementing evidence-based guidelines for nutrition therapy in critical illness do not consistently demonstrate patient benefits. A large-scale, sufficiently powered study is therefore warranted to ascertain the effects of guideline implementation on patient-centered outcomes.MethodsWe conducted a multicenter, cluster-randomized, parallel-controlled trial in intensive care units (ICUs) across China. We developed an evidence-based feeding guideline. ICUs randomly allocated to the guideline group formed a local "intervention team", which actively implemented the guideline using standardized educational materials, a graphical feeding protocol, and live online education outreach meetings conducted by members of the study management committee. ICUs assigned to the control group remained unaware of the guideline content. All ICUs enrolled patients who were expected to stay in the ICU longer than seven days. The primary outcome was all-cause mortality within 28 days of enrollment.ResultsForty-eight ICUs were randomized to the guideline group and 49 to the control group. From March 2018 to July 2019, the guideline ICUs enrolled 1399 patients, and the control ICUs enrolled 1373 patients. Implementation of the guideline resulted in significantly earlier EN initiation (1.20 vs. 1.55 mean days to initiation of EN; difference - 0.40 [95% CI - 0.71 to - 0.09]; P = 0.01) and delayed PN initiation (1.29 vs. 0.80 mean days to start of PN; difference 1.06 [95% CI 0.44 to 1.67]; P = 0.001). There was no significant difference in 28-day mortality (14.2% vs. 15.2%; difference - 1.6% [95% CI - 4.3% to 1.2%]; P = 0.42) between groups.ConclusionsIn this large-scale, multicenter trial, active implementation of an evidence-based feeding guideline reduced the time to commencement of EN and overall PN use but did not translate to a reduction in mortality from critical illness.Trial registrationISRCTN, ISRCTN12233792 . Registered November 20th, 2017