Distributed voltage-driven demand response: flexibility, stability and value assessment

The need for operating reserve from energy storage, demand reduction (DR) etc. is expected to increase signifcantly in future low-carbon Great Britain (GB) power system with high penetration of non-synchronous renewable generation. One way to provide the reserve is to use power electronic compensators (PECs) for point-of-load voltage control (PVC) to exploit the voltage dependence of loads. This thesis focuses on the quantifcation of DR capability from PVC in the domestic sector using high-resolution stochastic demand models and generic distribution networks in GB. The effectiveness of utilising PVC in contributing to frequency regulation is analysed and demonstrated through time domain simulations. The techno-economic feasibility of such technology is evaluated considering the investment cost of the PEC deployment as well as the economic and environmental benefts of using PVC. The payback period varies between 0.3 to 6.7 years for different future scenarios considering a range of converter price. It is demonstrated that PVC could effectively complement battery energy storage system towards enhanced frequency response provision in future GB power system. For practical application of PVC for flexible demand and voltage regulation in future distribution networks/microgrids, it is important to investigate the overall small signal stability of the system. In this thesis, the linearised state space model of a distribution network/isolated microgrid with converter-interfaced distributed generators (CDGs) working in grid following mode along with loads with PVC is developed. The stability performance is revealed through both modal analysis and time domain simulations. It is shown that multiple loads with PVC for voltage regulation in distribution networks are not likely to threaten the small signal stability of the system. In the case of a microgrid, the introduction of PVC is shown to have marginal impact on the low frequency modes associated with the droop control of the CDGs. However, there is a trade-off when choosing the droop gain of the loads with PVC. Lower droop gains could ensure better frequency regulation in face of intermittent renewables but at the expense of a lower stability margin for an oscillation mode at a frequency slightly higher than 20Hz.Open Acces

Application of Bayesian classification with singular value decomposition method in genome-wide association studies

To analyze multiple single-nucleotide polymorphisms simultaneously when the number of markers is much larger than the number of studied individuals, as is the situation we have in genome-wide association studies (GWAS), we developed the iterative Bayesian variable selection method and successfully applied it to the simulated rheumatoid arthritis data provided by the Genetic Analysis Workshop 15 (GAW15). One drawback for applying our iterative Bayesian variable selection method is the relatively long running time required for evaluation of GWAS data. To improve computing speed, we recently developed a Bayesian classification with singular value decomposition (BCSVD) method. We have applied the BCSVD method here to the rheumatoid arthritis data distributed by GAW16 Problem 1 and demonstrated that the BCSVD method works well for analyzing GWAS data

Left atrial appendage filling defect in exclusive early-phase scanning of dual-phase cardiac computed tomography: an indicator for elevated thromboembolic risk

Background: Dual-phase cardiac computed tomography (CCT) has been applied to detect left atrial appendage (LAA) thrombosis, which is characterized as the presence of left atrial appendage filling defects (LAADF) in both early- and delayed-phase scanning. However, the clinical implication of LAAFD in exclusive early-phase scanning (LAAFD-EEpS) of CCT in patients with atrial fibrillation (AF) is unclear. Methods: The baseline clinical data and dual-phase CCT findings in 1183 AF patients (62.1 ± 11.6 years, 59.9% male) was collected and analyzed. A further analysis of CCT and transesophageal echocardiography (TEE) data (within 5 days) in a subgroup of 687 patients was performed. LAAFD-EEpS was defined as LAAFD present in early-phase and absent in delayed-phase scanning of dual-phase CCT. Results: A total of 133 (11.2%) patients were detected with LAAFD-EEpS. Patients with LAAFD-EEpS had a higher prevalence of ischemic stroke or transient ischemic attack (TIA) (p < 0.001) and a higher predefined thromboembolic risk (p < 0.001). In multivariate analysis, a history of ischemic stroke or TIA was independently associated with LAAFD-EEpS (odds ratio [OR] 11.412, 95% confidence interval [CI] 6.561–19.851, p < 0.001). When spontaneous echo contrast in TEE was used as the reference standard, the sensitivity, specificity, positive predictive value, and negative predictive value of LAAFD-EEpS was 77.0% (95% CI 66.5–87.6%), 89.0% (95% CI 86.5–91.4%), 40.5% (95% CI 31.6–49.5%), 97.5% (96.3–98.8%), respectively. Conclusions: In AF patients, LAAFD-EEpS is not an uncommon finding in dual-phase CCT scanning, and is associated with elevated thromboembolic risk

Heritability patterns in hand osteoarthritis: the role of osteophytes

Abstract Introduction The objective of the present study was to assess heritability of clinical and radiographic features of hand osteoarthritis (OA) in affected patients and their siblings. Methods A convenience sample of patients with clinical and radiographic hand OA and their siblings were evaluated by examination and radiography. Radiographs were scored for hand OA features by radiographic atlas. The heritability of hand OA phenotypes was assessed for clinical and radiographic measures based on anatomic locations and radiographic characteristics. Phenotypic data were transformed to reduce non-normality, if necessary. A variance components approach was used to calculate heritability. Results One hundred and thirty-six probands with hand OA and their sibling(s) were enrolled. By anatomic location, the highest heritability was seen with involvement of the first interphalangeal joint (h 2 = 0.63, P = 0.00004), the first carpometacarpal joint (h 2 = 0.38, P = 0.01), the distal interphalangeal joints (h 2 = 0.36, P = 0.02), and the proximal interphalangeal joints (h 2 = 0.30, P = 0.03) with osteophytes. The number and severity of joints with osteophyte involvement was heritable overall (h 2 = 0.38, P = 0.008 for number and h 2 = 0.35, P = 0.01 for severity) and for all interphalangeal joints (h 2 = 0.42, P = 0.004 and h 2 = 0.33, P = 0.02). The severity of carpometacarpal joint involvement was also heritable (h 2 = 0.53, P = 0.0006). Similar results were obtained when the analysis was limited to the Caucasian sample. Conclusions In a population with clinical and radiographic hand OA and their siblings, the presence of osteophytes was the most sensitive biomarker for hand OA heritability. Significant heritability was detected for anatomic phenotypes by joint location, severity of joint involvement with osteophytes as well as for overall number and degree of hand OA involvement. These findings are in agreement with the strong genetic predisposition for hand OA reported by others. The results support phenotyping based on severity of osteophytes and a joint-specific approach. More specific phenotypes may hold greater promise in the study of genetics in hand OA

Application of Bayesian regression with singular value decomposition method in association studies for sequence data

Genetic association studies usually involve a large number of single-nucleotide polymorphisms (SNPs) (k) and a relative small sample size (n), which produces the situation that k is much greater than n. Because conventional statistical approaches are unable to deal with multiple SNPs simultaneously when k is much greater than n, single-SNP association studies have been used to identify genes involved in a disease’s pathophysiology, which causes a multiple testing problem. To evaluate the contribution of multiple SNPs simultaneously to disease traits when k is much greater than n, we developed the Bayesian regression with singular value decomposition (BRSVD) method. The method reduces the dimension of the design matrix from k to n by applying singular value decomposition to the design matrix. We evaluated the model using a Markov chain Monte Carlo simulation with Gibbs sampler constructed from the posterior densities driven by conjugate prior densities. Permutation was incorporated to generate empirical p-values. We applied the BRSVD method to the sequence data provided by Genetic Analysis Workshop 17 and found that the BRSVD method is a practical method that can be used to analyze sequence data in comparison to the single-SNP association test and the penalized regression method

Amino-functionalized macroporous silica for efficient tryptic digestion in acidic solutions

Amino-functionalized macroporous silica foam (NH2-MOSF) has been developed as a host reactor to realize highly efficient proteolysis in acidic solutions where normal tryptic reactions cannot occur. The digestion protocol consists simply of adding the functionalized NH2-MOSF into the protein and trypsin solutions without altering the bulk pH or preloading the enzymes on the materials. With this protocol, digestion of sample fractions from LC can be efficiently realized in the acidic solutions directly. Digestion of a protein fraction extracted from rat liver tissue after LC separation was performed to illustrate this principle, where 103 proteins were successfully identified at pH 3 after 1.5 h of tryptic digestion

Early-start antiplatelet therapy after operation in patients with spontaneous intracerebral hemorrhage and high risk of ischemic events (E-start):Protocol for a multi-centered, prospective, open-label, blinded endpoint randomized controlled trial

BACKGROUND: For severe spontaneous intracerebral hemorrhage (sSICH) patients with high risk of ischemic events, the incidence of postoperative major cardiovascular/cerebrovascular and peripheral vascular events (MACCPE) is notable. Although antiplatelet therapy is a potential way to benefit these patients, the severe hemorrhagic complications, e.g., intracranial re-hemorrhage, is a barrier for early starting antiplatelet therapy. OBJECTIVES: This randomized controlled trial aims to identify the benefit and safety of early starting antiplatelet therapy after operation for sSICH patients with high risk of ischemic events. METHODS: This study is a multicenter, prospective, randomized, open-label, blinded-endpoint trial. We will enroll 250 sSICH patients with a high risk of ischemic events (including cerebral infarcts, transient ischemic attack, myocardial infarction, pulmonary embolism, and deep venous thrombosis). The participants will be randomized in a 1:1 manner to early-start group (start antiplatelet therapy at 3 days after operation) and normal-start group (start antiplatelet therapy at 30 days after operation). The early-start group will receive aspirin 100 mg daily. The control group will not receive antithrombotic therapy until 30 days after operation. The efficacy endpoint is the incidence of MACCPE, and the safety endpoint is the incidence of intracranial re-hemorrhage. DISCUSSION: The Early-Start antiplatelet therapy after operation in patients with spontaneous intracerebral hemorrhage trial (E-start) is the first randomized trial about early start antiplatelet therapy for operated sSICH patients with a high risk of ischemic events. This study will provide a new strategy and evidence for postoperative management in the future. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, identifier NCT04820972; Available at: https://clinicaltrials.gov/ct2/show/NCT04820972?term=NCT04820972&draw=2&rank=1. Chinese Clinical Trial Registry, identifier ChiCTR2100044560; Available at: http://www.chictr.org.cn/showproj.aspx?proj=123277

Micro- and nanostructured materials via ultrasonic spray pyrolysis

Micro- and nanostructured materials have become an important area in the materials society due to their unique physical and chemical properties. Numerous materials with nano- and microstructures have been synthesized, such as porous, core- shell, and hierarchical structures. Great emphasis has been put on the use of facile and environmental benign synthetic approaches to produce structured materials in a controllable manner. As a simple and industrially scalable technique, ultrasonic spray pyrolysis (USP) is a powerful synthetic tool especially for application-based materials due to the scalability of this technique and the environmentally friendly nature of many of the common precursors and templating methods. More importantly, the structure and composition of USP product can be readily controlled through using appropriate precursors and reaction conditions. In this dissertation, two examples of USP synthesis will be discussed: the USP preparation of gold nanoparticles in porous carbon, and the USP preparation of porous metal oxide. Another example of using traditional synthetic method to produce fluorescent carbon nanoparticles will also be demonstrated. First, USP has been applied to produce gold nanoparticles encapsulated in porous carbon for catalysis application. Gold nanoparticles (NPs) have recently been found to be surprisingly active catalysts for reactions like low temperature oxidation of CO and epoxidation of alkenes. The reactivity of gold nanoparticles, however, is difficult to exploit because of sintering. Encapsulated structures with porous supports prevent agglomeration, but prior synthetic methodologies using sacrificial templates increase complexity, cost, and waste. Using a one-step and template-free USP approach, gold NPswere encapsulated in situ in a highly porous carbon support, thus preventing sintering while still permitting accessibility to the catalytic gold surface. The surface catalytic activity of these Au/C particles for a benchmark reaction (the reduction of 4-nitrophenol) is extremely high compared with other reports in literature. In addition, in contrast to previously reported gold catalysts which only work for hydrophilic nitroaromatics, the USP Au/C exhibits good catalytic activity for both hydrophilic and hydrophobic nitroaromatics due to the presence of both hydrophilic and hydrophobic functional groups on the carbon matrix, making it a versatile catalyst with broad potential applications. Hollow iron oxide microspheres with high surface area can also be produced using USP. Nano- and microstructured iron oxides are intriguing materials owing to their high surface area, unique structures, and applications in lithium-ion batteries and biomedicine. Iron oxide structures have been synthesized mainly using colloidal synthesis, hydrothermal synthesis and sol-gel approach, which are usually cumbersome with multiple steps and the use of expensive templates, therefore are difficult to be scaled up for mass production. The iron oxides produced usually have relatively low surface areas (<100 m2/g) when compared with other materials like metals, carbons and polymers. By employing a novel precursor, a mildly energetic iron complex that can decompose into large amount of gas, hollow magnetite microspheres with high surface area have been successfully prepared via the one-step USP synthesis. The combination of “steam-iron” process with USP technique leads to surprisingly high crystallinity and purity of magnetite. These hollow Fe3O4 microspheres have been shown to maintain high lithium storage capacity. Besides the USP technique, other synthetic approaches were also applied to the preparation of nanomaterials. Specifically, fluorescent carbon nanoparticles were synthesized from pyrrole monomers by combining microemulsion polymerization and surface functionalization. The as-prepared carbon dots show strong intrinsic fluorescence with the quantum yield 1.2%, which can be increased to 12% after PEGylation. These carbon dots can be easily internalized in cells as bioimaging agents and still show bright photoluminescence after laser irradiation for several hours. Other fluorescence characteristics (e.g., photoluminescence lifetime) of these carbon dots are further studied to understand the fluorescence mechanism

Studies on Equalization Strategy of Battery Management System for Electric Vehicle

Battery management system is one of the key technologies strengthening practical utilization and industrialization of electric vehicles. As an integral part of the battery management system, equalization system played an important role in development of electric vehicles. Based on the analysis of the key technologies of electric vehicle and the development trend of battery management system, a systematic method for bi-directional equalization of lithium ion battery pack is presented in this paper. The basic principle utilizes a Flyback Converter with a multiwinding transformer. Equalization with voltage is employed to balance the cell voltage of battery pack. In order to ensure the accuracy requirements of the cell voltage, a voltage measurement scheme based on analog multiplexers using photoelectric relay was adopted in this unit to detect the voltage of battery one by one. Experimental results show that the proposed battery equalization scheme can not only enhance the uniformity of power battery pack, but also improve the life of the battery as a whole