bluuebunny/crossref_metadata_2025 huggingface dataset:
Curcumin-Mediated Degradation of S-Phase Kinase Protein 2 Induces Cytotoxic Effects in Human Papillomavirus-Positive and Negative Squamous Carcinoma Cells
Authors: Khan Abdul Q. , Siveen Kodappully S. , Prabhu Kirti S. , Kuttikrishnan Shilpa , Akhtar Sabah , Shaar Abdullah , Raza Afsheen , Mraiche Fatima , Dermime Said , Uddin Shahab
Published: October 2018

S-phase kinase-associated protein2 (Skp2), a proto-oncoprotein, plays an important role in development and progression of human malignancies. Skp2 is frequently overexpressed in many human malignancies. It targets cell cycle progression through ubiquitin mediated degradation of G1-checkpoint CDK inhibitors—p21 (CDKN1A) and p27 (CDKN1B). We investigated the role of Skp2 and its ubiquitin-proteasome pathway in head and neck squamous cell carcinoma (HNSCC) using a panel of cell lines with and without human papillomavirus (HPV+, HPV−). Treatment of HNSCC cell lines with curcumin, a natural compound isolated from rhizomes of the plant Curcuma longa, or transfection of small interfering RNA of Skp2, causes down-regulation of Skp2 with concomitant accumulation of p21 and p27 in HPV+, HPV− cells. Furthermore curcumin inhibits cell viability and induces apoptosis in a dose-dependent manner. Treatment of HPV+ and HPV− cells with curcumin induced apoptosis via mitochondrial pathway and activation of caspases. In addition, treatment of HPV+ and HPV− cell lines with curcumin down-regulated the expression of XIAP, cIAP1, and cIAP2. Interestingly, co-treatment of HNSCC cells with curcumin and cisplatin potentiated inhibition of cell viability and apoptotic effects. Altogether, these data suggest an important function for curcumin, acting as a suppressor of oncoprotein Skp2 in squamous cell carcinoma cells in both HPV+ and HPV− cells; raise the possibility that this agent may have a future therapeutic role in squamous cell carcinoma.
Cover Time in Edge-Uniform Stochastically-Evolving Graphs
Authors: Lamprou Ioannis , Martin Russell , Spirakis Paul
Published: October 2018

We define a general model of stochastically-evolving graphs, namely the edge-uniform stochastically-evolving graphs. In this model, each possible edge of an underlying general static graph evolves independently being either alive or dead at each discrete time step of evolution following a (Markovian) stochastic rule. The stochastic rule is identical for each possible edge and may depend on the past k ≥ 0 observations of the edge’s state. We examine two kinds of random walks for a single agent taking place in such a dynamic graph: (i) The Random Walk with a Delay (RWD), where at each step, the agent chooses (uniformly at random) an incident possible edge, i.e., an incident edge in the underlying static graph, and then, it waits till the edge becomes alive to traverse it. (ii) The more natural Random Walk on what is Available (RWA), where the agent only looks at alive incident edges at each time step and traverses one of them uniformly at random. Our study is on bounding the cover time, i.e., the expected time until each node is visited at least once by the agent. For RWD, we provide a first upper bound for the cases k = 0 , 1 by correlating RWD with a simple random walk on a static graph. Moreover, we present a modified electrical network theory capturing the k = 0 case. For RWA, we derive some first bounds for the case k = 0 , by reducing RWA to an RWD-equivalent walk with a modified delay. Further, we also provide a framework that is shown to compute the exact value of the cover time for a general family of stochastically-evolving graphs in exponential time. Finally, we conduct experiments on the cover time of RWA in edge-uniform graphs and compare the experimental findings with our theoretical bounds.
SLoPCloud: An Efficient Solution for Locality Problem in Peer-to-Peer Cloud Systems
Authors: Gharib Mohammed , Malekimajd Marzieh , Movaghar Ali
Published: October 2018

Peer-to-Peer (P2P) cloud systems are becoming more popular due to the high computational capability, scalability, reliability, and efficient data sharing. However, sending and receiving a massive amount of data causes huge network traffic leading to significant communication delays. In P2P systems, a considerable amount of the mentioned traffic and delay is owing to the mismatch between the physical layer and the overlay layer, which is referred to as locality problem. To achieve higher performance and consequently resilience to failures, each peer has to make connections to geographically closer peers. To the best of our knowledge, locality problem is not considered in any well known P2P cloud system. However, considering this problem could enhance the overall network performance by shortening the response time and decreasing the overall network traffic. In this paper, we propose a novel, efficient, and general solution for locality problem in P2P cloud systems considering the round-trip-time (RTT). Furthermore, we suggest a flexible topology as the overlay graph to address the locality problem more effectively. Comprehensive simulation experiments are conducted to demonstrate the applicability of the proposed algorithm in most of the well-known P2P overlay networks while not introducing any serious overhead.
Image Reconstruction of Internal Defects in Wood Based on Segmented Propagation Rays of Stress Waves
Authors: Du Xiaochen , Li Jiajie , Feng Hailin , Chen Shengyong
Published: October 2018

In order to detect the size and shape of defects inside wood, an image reconstruction method based on segmented propagation rays of stress waves is proposed. The method uses sensors to obtain the stress wave velocity data by hanging around the timber equally, visualizes those data, and reconstructs the image of internal defects with the visualized propagation rays. The basis of the algorithm is precisely segmenting the rays to benefit the spatial interpolation. First, a ray segmentation algorithm using the elliptical neighborhood technique is proposed, which can be used to segment the rays and estimate the velocity values of segmented rays by the nearby original rays using elliptical zones. Second, a spatial interpolation algorithm utilizing a segmented ellipse according to the segmented rays is also proposed, which can be used to estimate the velocity value of a grid cell by the segmented ellipses corresponding to the nearby segmented rays. Then, the image of the internal defect inside the wood is reconstructed. Both simulation and experimental data were used to evaluate the proposed method, and the area and shape of the imaging results were analyzed. The comparison results show that the proposed method can produce high quality reconstructions with clear edges and high accuracy.
Large-Scale Modeling of Absorbing Aerosols and Their Semi-Direct Effects
Authors: Tegen Ina , Heinold Bernd
Published: October 2018

Radiative effects of absorbing black carbon and mineral dust aerosols are estimated from global aerosol climate model simulations with fixed sea surface temperatures as a boundary condition. Semi-direct effects are approximated as the residual between the total direct radiative effect and the instantaneous direct radiative effect of the simulated absorbing aerosol species. No distinction is made for aerosols from natural and anthropogenic sources. Results for global average are highly uncertain due to high model variability, but consistent with previous estimates. The global average results for black carbon aerosol semi-direct effects are small due to cancellation of regionally positive or negative effects, and may be positive or negative overall, depending on the model setup. The presence of mineral dust aerosol above dark surfaces and below a layer containing black carbon aerosol may enhance the reflectivity and act to enhance the positive radiative effect of black carbon aerosol. When mineral dust is absent the semi-direct effect at the top-of-atmosphere of black carbon aerosol from both anthropogenic and natural sources is −0.03 Wm−2, while averaging to +0.09 Wm−2 if dust is included.
Novel Approaches for Solving the Capacity Fade Problem during Operation of a Vanadium Redox Flow Battery
Authors: Bhattarai Arjun , Ghimire Purna C. , Whitehead Adam , Schweiss Rüdiger , Scherer Günther G. , Wai Nyunt , Hng Huey Hoon
Published: October 2018

The vanadium redox flow battery (VRFB) is one of the most mature and commercially available electrochemical technologies for large-scale energy storage applications. The VRFB has unique advantages, such as separation of power and energy capacity, long lifetime (>20 years), stable performance under deep discharge cycling, few safety issues and easy recyclability. Despite these benefits, practical VRFB operation suffers from electrolyte imbalance, which is primarily due to the transfer of water and vanadium ions through the ion-exchange membranes. This can cause a cumulative capacity loss if the electrolytes are not rebalanced. In commercial systems, periodic complete or partial remixing of electrolyte is performed using a by-pass line. However, frequent mixing impacts the usable energy and requires extra hardware. To address this problem, research has focused on developing new membranes with higher selectivity and minimal crossover. In contrast, this study presents two alternative concepts to minimize capacity fade that would be of great practical benefit and are easy to implement: (1) introducing a hydraulic shunt between the electrolyte tanks and (2) having stacks containing both anion and cation exchange membranes. It will be shown that the hydraulic shunt is effective in passively resolving the continuous capacity loss without detrimentally influencing the energy efficiency. Similarly, the combination of anion and cation exchange membranes reduced the net electrolyte flux, reducing capacity loss. Both approaches work efficiently and passively to reduce capacity fade during operation of a flow battery system.
From the Field to the Bottle—An Integrated Strategy for Wine Authenticity
Authors: Pereira Leonor , Gomes Sónia , Barrias Sara , Gomes Elisa , Baleiras-Couto Margarida , Fernandes José , Martins-Lopes Paula
Published: October 2018

The wine sector is one of the most economically important agro-food businesses. The wine market value is largely associated to terroir, in some cases resulting in highly expensive wines that attract fraudulent practices. The existent wine traceability system has some limitations that can be overcome with the development of new technological approaches that can tackle this problem with several means. This review aims to call attention to the problem and to present several strategies that can assure a more reliable and authentic wine system, identifying existent technologies developed for the sector, which can be incorporated into the current traceability system.
Neuromodulation for Pelvic and Urogenital Pain
Authors: Roy Holly , Offiah Ifeoma , Dua Anu
Published: October 2018

Chronic pain affecting the pelvic and urogenital area is a major clinical problem with heterogeneous etiology, affecting both male and female patients and severely compromising quality of life. In cases where pharmacotherapy is ineffective, neuromodulation is proving to be a potential avenue to enhance analgesic outcomes. However, clinicians who frequently see patients with pelvic pain are not traditionally trained in a range of neuromodulation techniques. The aim of this overview is to describe major types of pelvic and urogenital pain syndromes and the neuromodulation approaches that have been trialed, including peripheral nerve stimulation, dorsal root ganglion stimulation, spinal cord stimulation, and brain stimulation techniques. Our conclusion is that neuromodulation, particularly of the peripheral nerves, may provide benefits for patients with pelvic pain. However, larger prospective randomized studies with carefully selected patient groups are required to establish efficacy and determine which patients are likely to achieve the best outcomes.
Gap Junction Intercellular Communication Positively Regulates Cisplatin Toxicity by Inducing DNA Damage through Bystander Signaling
Authors: Arora Sanjeevani , Heyza Joshua R. , Chalfin Elaine C. , Ruch Randall J. , Patrick Steve M.
Published: October 2018

The radiation-induced bystander effect (RIBE) can increase cellular toxicity in a gap junction dependent manner in unirradiated bystander cells. Recent reports have suggested that cisplatin toxicity can also be mediated by functional gap junction intercellular communication (GJIC). In this study using lung and ovarian cancer cell lines, we showed that cisplatin cytotoxicity is mediated by cellular density. This effect is ablated when GJA1 or Connexin 43 (Cx43) is targeted, a gap junction gene and protein, respectively, leading to cisplatin resistance but only at high or gap junction forming density. We also observed that the cisplatin-mediated bystander effect was elicited as DNA Double Strand Breaks (DSBs) with positive H2AX Ser139 phosphorylation (γH2AX) formation, an indicator of DNA DSBs. These DSBs are not observed when gap junction formation is prevented. We next showed that cisplatin is not the “death” signal traversing the gap junctions by utilizing the cisplatin-GG intrastrand adduct specific antibody. Finally, we also showed that cells deficient in the structure-specific DNA endonuclease ERCC1-ERCC4 (ERCC1-XPF), an important mediator of cisplatin resistance, further sensitized when treated with cisplatin in the presence of gap junction forming density. Taken together, these results demonstrate the positive effect of GJIC on increasing cisplatin cytotoxicity.
Trimetallic Ni-Based Catalysts over Gadolinia-Doped Ceria for Green Fuel Production
Authors: Frontera Patrizia , Macario Anastasia , Malara Angela , Santangelo Saveria , Triolo Claudia , Crea Fortunato , Antonucci Pierluigi
Published: October 2018

The present work concerns the characterization of trimetallic nickel catalysts, NiMoRe (Nickel/Molybdenum/Rhenium), NiMoCu (Nickel/Molybdenum/Copper) and NiMoCo (Nickel/Molybdenum/Cobalt), supported on gadolinia-doped ceria and the evaluation of their catalytic performance in the auto-thermal reforming of ethanol to hydrogen. Catalysts have been prepared by wet impregnation and characterized by XRD, SEM-EDX, TG-DSC, TEM, CHNS, H2-TPR and micro-Raman spectroscopy. The resistance of Ni-alloy catalysts to the carbon deposition and sulfur poisoning has been studied. All catalysts show a similar behavior in the auto-thermal reforming reaction: 100% of ethanol conversion and high selectivity to syngas products, up to 77 vol.%. At 800 °C the coke deposition is very low (less than 0.34 wt%). Sulfur content affects the selectivity and the activity of the catalysts, especially towards the coke formation: high sulfur content promotes the ethylene formation, therefore the amount of coke deposited on spent catalyst increases. NiMoCu seems to be the trimetallic catalyst less sensitive to this aspect.
Exploring the Processing of Tubular Chromite- and Zirconia-Based Oxygen Transport Membranes
Authors: Haugen Astri , Aguilera Lev , Kwok Kawai , Molla Tesfaye , Andersen Kjeld , Pirou Stéven , Kaiser Andreas , Hendriksen Peter , Kiebach Ragnar
Published: October 2018

Tubular oxygen transport membranes (OTMs) that can be directly integrated in high temperature processes have a large potential to reduce CO2 emissions. However, the challenging processing of these multilayered tubes, combined with strict material stability requirements, has so far hindered such a direct integration. We have investigated if a porous support based on (Y2O3)0.03(ZrO2)0.97 (3YSZ) with a dense composite oxygen membrane consisting of (Y2O3)0.01(Sc2O3)0.10(ZrO2)0.89 (10Sc1YSZ) as an ionic conductor and LaCr0.85Cu0.10Ni0.05O3−δ (LCCN) as an electronic conductor could be fabricated as a tubular component, since these materials would provide outstanding chemical and mechanical stability. Tubular components were made by extrusion, dip coating, and co-sintering, and their chemical and mechanical integrity was evaluated. Sufficient gas permeability (≥10−14 m2) and mechanical strength (≥50 MPa) were achieved with extruded 3YSZ porous support tubes. The high co-sintering temperature required to densify the 10ScYSZ/LCCN membrane on the porous support, however, causes challenges related to the evaporation of chromium from the membrane. This chemical degradation caused loss of the LCCN electronic conducting phase and the formation of secondary lanthanum zirconate compounds and fractures. LCCN is therefore not suitable as the electronic conductor in a tubular OTM, unless means to lower the sintering temperature and reduce the chromium evaporation are found that are applicable to the large-scale fabrication of tubular components.
Empirical Kinetic Modelling of the Effect of l-Ascorbic Acid on the Cu(II)-Induced Oxidation of Quercetin
Authors: Bobolaki Nikoletta , Photiades Angelos , Grigorakis Spyros , Makris Dimitris P.
Published: October 2018

This study aimed at investigating the effect of l-ascorbic acid on the Cu2+-induced oxidation of quercetin, within a pH range from 6.7 to 8.3 and temperatures varying from 53 to 87 °C. Initial examinations showed that quercetin degradation obeyed apparent first-order kinetics and it was significantly affected by temperature. Modelling of the effect of l-ascorbic acid by implementing response surface methodology suggested that l-ascorbic acid did not impact quercetin oxidation significantly (p < 0.05) and led to an empirical kinetic model based on temperature (T) and pH. Liquid chromatography–diode array–mass spectrometry analyses revealed the presence of typical quercetin degradation and oxidation products, including protocatechuic acid and 2-(hydroxybenzoyl)-2-hydroxybenzofuran-3(2H)-one. It was concluded that the formation of l-ascorbyl or other radicals (superoxide anion) may be involved in quercetin oxidation and this fact merits further attention to illuminate the possible beneficial or adverse nutritional consequences of such reactions in foods.
Evaluating Design Strategies for Nearly Zero Energy Buildings in the Middle East and North Africa Regions
Authors: Al-Saeed Yahya Wisam , Ahmed Abdullahi
Published: October 2018

There is international pressure for countries to reduce greenhouse gas emissions, which are blamed as the main cause of climate change. The countries in the Middle East and North Africa (MENA) region heavily rely on fossil fuel as the main energy source for buildings. The concept of nearly zero energy buildings (nZEB) has been defined and standardized for some developed countries. While most of the developing countries located in the MENA region with hot and tropical climate lack building energy efficiency standards. With pressure to improve energy and environmental performance of buildings, nZEB buildings are expected to grow over the coming years and employing these buildings in the MENA region can reduce building energy consumption and CO2 emissions. Therefore, the paper focuses on: (a) reviewing the current established nZEB standards and definitions for countries in the hot and warm climate of Europe, (b) investigate the primary energy consumption for current existing buildings in the MENA region, and (c) establishing a standard for nZEB and positive energy buildings in kWh/m2/year for the MENA region using a building simulation platform represented using Autodesk Insight 360. The result of the simulation reveals high energy use intensity for existing buildings in the MENA region. By improving building fabric and applying solar photovoltaics (PV) in the base model, significant reductions in primary energy consumption was achieved. Further design improvements, such as increasing the airtightness and using high efficiency solar PV, also contributed to positive energy buildings that produce more energy than they consume.
When to Initiate Weight Loss Medications in the NAFLD Population
Authors: Yoo Eric R. , Sallam Sandy , Perumpail Brandon J. , Iqbal Umair , Shah Neha D. , Kwong Waiyee , Cholankeril George , Kim Donghee , Ahmed Aijaz
Published: October 2018

Nonalcoholic fatty liver disease (NAFLD) is characterized by histological evidence of hepatic steatosis, lobular inflammation, ballooning degeneration and hepatic fibrosis in the absence of significant alcohol use and other known causes of chronic liver diseases. NAFLD is subdivided into nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH). NAFL is generally benign but can progress to NASH, which carries a higher risk of adverse outcomes including cirrhosis, end-stage liver disease, hepatocellular carcinoma and death if liver transplantation is not pursued in a timely fashion. Currently, lifestyle modifications including healthy diet and increased physical activity/exercise culminating in weight loss of 5% to >10% is the cornerstone of treatment intervention for patients with NAFLD. Patients with NAFLD who fail to obtain this goal despite the help of dietitians and regimented exercise programs are left in a purgatory state and remain at risk of developing NASH-related advance fibrosis. For such patients with NAFLD who are overweight and obese, healthcare providers should consider a trial of FDA-approved anti-obesity medications as adjunct therapy to provide further preventative and therapeutic options as an effort to reduce the risk of NAFLD-related disease progression.
Prevention of Progression in Myopia: A Systematic Review
Authors: Vagge Aldo , Ferro Desideri Lorenzo , Nucci Paolo , Serafino Massimiliano , Giannaccare Giuseppe , Traverso Carlo E.
Published: October 2018

The prevalence of myopia has increased worldwide in recent decades and now is endemic over the entire industrial world. This increase is mainly caused by changes in lifestyle and behavior. In particular, the amount of outdoor activities and near work would display an important role in the pathogenesis of the disease. Several strategies have been reported as effective. Spectacles and contact lenses have shown only slight results in the prevention of myopia and similarly ortokerathology should not be considered as a first-line strategy, given the high risk of infectious keratitis and the relatively low compliance for the patients. Thus, to date, atropine ophthalmic drops seem to be the most effective treatment for slowing the progression of myopia, although the exact mechanism of the effect of treatment is still uncertain. In particular, low-dose atropine (0.01%) was proven to be an effective and safe treatment in the long term due to the lowest rebound effect with negligible side effects.
New Equilibrium Ensembles for Isolated Quantum Systems
Authors: Anza Fabio
Published: October 2018

The unitary dynamics of isolated quantum systems does not allow a pure state to thermalize. Because of that, if an isolated quantum system equilibrates, it will do so to the predictions of the so-called “diagonal ensemble” ρ DE . Building on the intuition provided by Jaynes’ maximum entropy principle, in this paper we present a novel technique to generate progressively better approximations to ρ DE . As an example, we write down a hierarchical set of ensembles which can be used to describe the equilibrium physics of small isolated quantum systems, going beyond the “thermal ansatz” of Gibbs ensembles.
Multi-Objective Evolutionary Instance Selection for Regression Tasks
Authors: Kordos Mirosław , Łapa Krystian
Published: October 2018

The purpose of instance selection is to reduce the data size while preserving as much useful information stored in the data as possible and detecting and removing the erroneous and redundant information. In this work, we analyze instance selection in regression tasks and apply the NSGA-II multi-objective evolutionary algorithm to direct the search for the optimal subset of the training dataset and the k-NN algorithm for evaluating the solutions during the selection process. A key advantage of the method is obtaining a pool of solutions situated on the Pareto front, where each of them is the best for certain RMSE-compression balance. We discuss different parameters of the process and their influence on the results and put special efforts to reducing the computational complexity of our approach. The experimental evaluation proves that the proposed method achieves good performance in terms of minimization of prediction error and minimization of dataset size.
Entropy Power, Autoregressive Models, and Mutual Information
Authors: Gibson Jerry
Published: October 2018

Autoregressive processes play a major role in speech processing (linear prediction), seismic signal processing, biological signal processing, and many other applications. We consider the quantity defined by Shannon in 1948, the entropy rate power, and show that the log ratio of entropy powers equals the difference in the differential entropy of the two processes. Furthermore, we use the log ratio of entropy powers to analyze the change in mutual information as the model order is increased for autoregressive processes. We examine when we can substitute the minimum mean squared prediction error for the entropy power in the log ratio of entropy powers, thus greatly simplifying the calculations to obtain the differential entropy and the change in mutual information and therefore increasing the utility of the approach. Applications to speech processing and coding are given and potential applications to seismic signal processing, EEG classification, and ECG classification are described.
Minimum Description Length Codes Are Critical
Authors: Cubero Ryan John , Marsili Matteo , Roudi Yasser
Published: October 2018

In the Minimum Description Length (MDL) principle, learning from the data is equivalent to an optimal coding problem. We show that the codes that achieve optimal compression in MDL are critical in a very precise sense. First, when they are taken as generative models of samples, they generate samples with broad empirical distributions and with a high value of the relevance, defined as the entropy of the empirical frequencies. These results are derived for different statistical models (Dirichlet model, independent and pairwise dependent spin models, and restricted Boltzmann machines). Second, MDL codes sit precisely at a second order phase transition point where the symmetry between the sampled outcomes is spontaneously broken. The order parameter controlling the phase transition is the coding cost of the samples. The phase transition is a manifestation of the optimality of MDL codes, and it arises because codes that achieve a higher compression do not exist. These results suggest a clear interpretation of the widespread occurrence of statistical criticality as a characterization of samples which are maximally informative on the underlying generative process.
Optimal Modeled Six-Phase Space Vector Pulse Width Modulation Method for Stator Voltage Harmonic Suppression
Authors: Luo Qiwu , Zheng Jian , Sun Yichuang , Yang Lijun
Published: October 2018

Dual Y shift 30° six-phase motors are expected to be extensively applied in high-power yet energy-effective fields, and a harmonic-suppressing control strategy plays a vital role in extending their prominent features of low losses and ultra-quiet operation. Aiming at the suppression of harmonic voltages, this paper proposes a six-phase space vector pulse width modulation method based on an optimization model, namely OM-SVPWM. First, four adjacent large vectors are employed in each of 12 sectors on a fundamental sub-plane. Second, the optimization model is constructed to intelligently determine activation durations of the four vectors, where its objective function aims to minimize the synthesis result on a harmonic sub-plane, and its constraint condition is that the synthesis result on the fundamental sub-plane satisfies a reference vector. Finally, to meet the real-time requirement, optimum solutions are obtained by using general central path following algorithm (GCPFA). Simulation and experiment results prove that, the OM-SVPWM performs around 37% better than a state-of-the-art competitive SVPWM in terms of harmonics suppression, which promise the proposed OM-SVPWM conforms to the energy-effective direction in actual engineering applications.
Coupled Harmonic Admittance Identification Based on Least Square Estimation
Authors: Li Yaqiong , Deng Zhanfeng , Wang Tongxun , Zhao Guoliang , Zhou Shengjun
Published: October 2018

Norton equivalent circuit is a commonly used model in estimating harmonic current emissions of harmonic sources. It however cannot reflect the mutual coupling relationships among voltage and current in different harmonic orders. This paper proposes a new method to identify parameters in a coupled harmonic admittance model. The proposed method is conducted using voltage and current measurements and is based on least square estimation technique. The effectiveness of the method is verified through time-domain simulations for a grid-connected converter and also through field data obtained from a ±800 kV converter station. The experimental results showed that the proposed method presents higher accuracy in terms of harmonic current emission estimation compared with three Norton-base methods.
Experimental Study on Hydrate Formation and Flow Characteristics with High Water Cuts
Authors: Zhou Shidong , Chen Xiaokang , He Chengyuan , Wang Shuli , Zhao Shuhua , Lv Xiaofang
Published: October 2018

The rapid increasing amount of produced water in the deep-water and ultra-deep-water fields, especially those at their later development stages, increases the risk of the occurrence of hydrates plugging. In order to prevent and remediate the hydrates risks, it is important to understand the hydrate formation, slurry flow, and plugging characteristics and mechanisms under high water cuts conditions. In this paper, experiments with high water cuts ranging from 60–100% were conducted using a high pressure flow loop with observation windows. The whole processes of the hydrate formation, slurry flow and plugging is visually seen and recorded, and has been discussed and explained in detail in this paper. Moreover, it is found that the increasing water cuts shorten the induction time, but increase the volume fraction of hydrates. As the water cuts increase, the flow time of the hydrate slurry decreases, which serves as a critical parameter for the safe operation of the pipeline. In addition, different hypothetical mechanisms have been proposed for the medium and high water cuts conditions. We believe that this research can provide theoretical support for the safe transportation of oil and gas development in the high water cut oilfield.
Application of Subcritical Water to Dechlorinate Polyvinyl Chloride Electric Wires
Authors: Soler Aurora , Conesa Juan , Ortuño Nuria
Published: October 2018

Polyvinyl chloride (PVC) electric wires were subjected to dechlorination in subcritical water at three different temperatures in a high-pressure reactor. About 2.09, 73.08, and 95.96 wt % of chlorine in PVC wires was removed during dechlorination at 200 °C, 250 °C, and 300 °C, respectively. The solid residues were analyzed and characterized by thermogravimetry, at three different heating rates (5 °C, 10 °C, and 20 °C/min) in inert and oxidizing atmosphere. With the purpose of studying the emission of chlorinated pollutants, pyrolysis experiments at 850 °C were also performed in a laboratory-scale reactor with the dechlorinated materials, as well as with the original PVC electric wire. Polycyclic aromatic hydrocarbons (PAH) formation increased, but chlorobenzenes (ClBz) and chlorophenols (ClPh) formation decreased as the temperature of dechlorination increased; naphthalene was the most abundant PAH and monochlorobenzene and monochlorinated phenols (3-+4-) were the most abundant chlorinated compounds.
Impacts of the Base-Level Cycle on Pore Structure of Mouth Bar Sand Bars: A Case Study of the Paleogene Kongdian Formation, Bohai Bay Basin, China
Authors: Wang Xixin , Hou Jiagen , Liu Yuming , Ji Ling , Sun Jian , Gong Xun
Published: October 2018

The pore structure of rocks can affect fluid migration and the remaining hydrocarbon distribution. To understand the impacts of the base-level cycle on the pore structure of mouth bar sand bodies in a continental rift lacustrine basin, the pore structure of the mouth bar sand bodies in the ZVC (ZV4 + ZV5) of the Guan195 area was studied using pressure-controlled mercury injection (PMI), casting sheet image and scanning electron microscopy (SEM). The results show that three types of pores exist in ZVC, including intergranular pores, dissolution pores, and micro fractures. The porosity is generally between 1.57% and 44.6%, with a mean value of 19.05%. The permeability is between 0.06 μm2 and 3611 μm2, with a mean value of 137.56 μm2. The pore structure heterogeneity of a single mouth bar sand body in the early stage of the falling period of short-term base-level is stronger than that in the late stage. During the falling process of the middle-term base level, the pore structure heterogeneity of a late single mouth bar sand body is weaker than that of an early single mouth bar sand body. In the long-term base-level cycle, the pore structure heterogeneity of mouth bar sand bodies becomes weaker with the falling of the base-level.
Electromagnetic Transient-Transient Stability Analysis Hybrid Real-Time Simulation Method of Variable Area of Interest
Authors: Zhang Bingda , Nie Shipei , Jin Zhao
Published: October 2018

To make the object of electromagnetic transient (EMT) simulation flexible to change, the authors propose using the method of electromagnetic transient-transient stability analysis (TSA) hybrid real-time simulation of the variable area of interest. The area where the fault is to be set, or where the operation takes place, is defined as the area of interest. The simulation object is divided into multiple sub-networks. The EMT simulation range is determined according to the voltage drop depth at the boundary of the adjacent sub-network caused by the three-phase short-circuit fault at the boundary of an area of interest. The Norton equivalent is obtained by using the sub-network as a basic unit. The electromagnetic sub-network forms its own Norton equivalent on the TSA side by means of the Norton equivalent admittance of its TSA model. Based on this, the overall framework of hybrid real-time simulation of the variable area of interest is constructed. The fundamental phasor prediction and Norton equivalent current source prediction are adopted to reduce the interface error. The performance of the proposed method in terms of feasibility, flexibility, and effectiveness have been verified by the simulation studies on the IEEE 118-bus system.
Multifield Calculation and Analysis of Excitation Winding Interturn Short Circuit Fault in Turbo-Generator
Authors: Ma Minghan , Li Yonggang , Wu Yucai , Dong Chenchen
Published: October 2018

Excitation winding interturn short circuit (EWISC) is a common fault in turbo-generators. Once the fault occurs, if not handled in time, it will result in significant security risks to the power system. Using the multifield characteristics of fault generators for a comprehensive diagnosis can make the diagnostic results more accurate and credible. In this paper, taking a TA-1100-78 type, two pole pairs turbo-generator as the research object, the two-dimensional finite element electromagnetic model of stator/rotor and the three-dimensional finite element heat transfer model of rotor were established. The electromagnetic field, temperature field, and stress field of the generator were simulated and analyzed. At the same time, the air gap magnetic field, three-dimensional temperature field, and stress field distribution of the rotor were calculated for EWISC faults in different fault degrees and positions. The results showed that the EWISC fault weakened the air gap magnetic field and caused unbalanced electromagnetic distribution. At the same time, it caused a distortion of the rotor temperature field, resulting in an unbalanced distribution of the temperature field. The stress field was affected by the distortion of temperature field, and the local thermal stress increased but did not exceed the yield limit of the material. Restorable elastic deformation occurred when the rotor was heated, which caused the thermal bending of the rotor. The method adopted in this paper can provide a reference for the calculation of multiphysical field after a generator fault. It is also pointed out that the thermal unbalance influence should not be neglected in the study of generator vibration characteristics.
Thermodynamic Modeling of CO2-N2-O2-Brine-Carbonates in Conditions from Surface to High Temperature and Pressure
Authors: Li Jun , Ahmed Raheel , Li Xiaochun
Published: October 2018

Nitrogen (N2) and oxygen (O2) are important impurities obtained from carbon dioxide (CO2) capture procedures. Thermodynamic modeling of CO2-N2-O2-brine-minerals is important work for understanding the geochemical change of CO2 geologic storage with impurities. In this work, a thermodynamic model of the CO2-N2-O2-brine-carbonate system is established using the “fugacity-activity” method, i.e., gas fugacity coefficients are calculated using a cubic model and activity coefficients are calculated using the Pitzer model. The model can calculate the properties at an equilibrium state of the CO2-N2-O2-brine-carbonate system in terms of gas solubilities, mineral solubilities, H2O solubility in gas-rich phase, species concentrations in each phase, pH and alkalinity. The experimental data of this system can be well reproduced by the presented model, as validated by careful comparisons in conditions from surface to high temperature and pressure. The model established in this work is suitable for CO2 geologic storage simulation with N2 or O2 present as impurities.
A Harmonic Compensation Strategy in a Grid-Connected Photovoltaic System Using Zero-Sequence Control
Authors: Naderipour Amirreza , Abdul-Malek Zulkurnain , Miveh Mohammad Reza , Hadidian Moghaddam Mohammad Jafar , Kalam Akhtar , Gandoman Foad. H.
Published: October 2018

Mitigation of harmonics for a grid-connected inverter is an important element to stabilize the control and the quality of current injected into the grid. This paper deals with the control method of a three-phase Grid-Connected Inverter (GCI) Photovoltaic (PV) system, which is based on the zero-sequence current adjuster. The proposed method is capable of removing the harmonic current and voltage without using any active and passive filters and without the knowledge of the microgrid topology and also impedances of distribution bands and loading conditions. This concept is adopted for the control of a Distributed Generator (DG) in the form of grid-connected inverter. The proposed control can be applied to the grid connected inverter of the PV. The fast dynamic response, simple design, stability, and fast transient response are the new main features of the proposed design. This paper also analyzes the circuit configuration effects on the grid connected inverter capability. The proposed control is used to demonstrate the improved stability and performance.
Biogas and Ethanol from Wheat Grain or Straw: Is There a Trade-Off between Climate Impact, Avoidance of iLUC and Production Cost?
Authors: Lantz Mikael , Prade Thomas , Ahlgren Serina , Björnsson Lovisa
Published: October 2018

Current EU policy calls for decreased emissions of greenhouse gases (GHG) by i.e., replacing fossil fuel in the transportation sector with sustainable biofuels. To avoid indirect land use change (iLUC), the EU at the same time strives to limit the use of crops and to increase the use of residues. In this study we compare climate impact and production cost for biogas and ethanol based on wheat grain and straw, respectively, in a Swedish context. The economic competitiveness for ethanol from straw vs. grain is evaluated based on the mandatory emission reduction for fossil vehicle fuels implemented since July 2018 in Sweden. The result of this study clearly shows that biogas and ethanol from straw have the lowest GHG emissions regardless of the calculation method used, although biofuels from grain also fulfill EU GHG reduction criteria even when suggested iLUC factors are included. It was also shown that the cost of producing straw-based biofuels was higher, thus there is a trade-off between climate impact and costs. The GHG reduction mandate adopted in Sweden partly compensates for this, but is not enough to make ethanol from straw competitive from an economic perspective.
Optimal Operation Modes of Virtual Power Plants Based on Typical Scenarios Considering Output Evaluation Criteria
Authors: Luo Jingjing , Gao Yajing , Yang Wenhai , Yang Yongchun , Zhao Zheng , Tian Shiyu
Published: October 2018

Stimulated by the severe energy crisis and the increasing awareness about the need for environmental protection, the efficient use of renewable energy has become a hot topic. The virtual power plant (VPP) is an effective way of integrating distributed energy systems (DES) by effectively deploying them in power grid dispatching or electricity trading. In this paper, the operating mode of the VPP with penetration of wind power, solar power and energy storage is investigated. Firstly, the grid-connection requirements of VPP according to the current wind and solar photovoltaic (PV) grid-connection requirements, and analyzed its profitability are examined. Secondly, under several typical scenarios grouped by a self-organization map (SOM) clustering algorithm using the VPP’s output data, a profit optimization model is established as a guideline for the VPP’s optimal operation. Based on this model, case studies are performed and the results indicate that this model is both feasible and effective.
Numerical Investigation of Terrain-Induced Turbulence in Complex Terrain by Large-Eddy Simulation (LES) Technique
Authors: Uchida Takanori
Published: October 2018

In the present study, field observation wind data from the time of the wind turbine blade damage accident on Shiratakiyama Wind Farm were analyzed in detail. In parallel, high-resolution large-eddy simulation (LES) turbulence simulations were performed in order to examine the model’s ability to numerically reproduce terrain-induced turbulence (turbulence intensity) under strong wind conditions (8.0–9.0 m/s at wind turbine hub height). Since the wind velocity and time acquired from the numerical simulation are dimensionless, they are converted to full scale. As a consequence, both the standard deviation of the horizontal wind speed (m/s) and turbulence intensity evaluated from the field observation and simulated wind data are successfully in close agreement. To investigate the cause of the wind turbine blade damage accident on Shiratakiyama Wind Farm, a power spectral analysis was performed on the fluctuating components of the observed time series data of wind speed (1 s average values) for a 10 min period (total of 600 data) by using a fast Fourier transform (FFT). It was suggested that the terrain-induced turbulence which caused the wind turbine blade damage accident on Shiratakiyama Wind Farm was attributable to rapid wind speed and direction fluctuations which were caused by vortex shedding from Tenjogadake (elevation: 691.1 m) located upstream of the wind farm.
Wineinformatics: Regression on the Grade and Price of Wines through Their Sensory Attributes
Authors: Palmer James , Chen Bernard
Published: October 2018

Wineinformatics is a field that uses machine-learning and data-mining techniques to glean useful information from wine. In this work, attributes extracted from a large dataset of over 100,000 wine reviews are used to make predictions on two variables: quality based on a “100-point scale”, and price per 750 mL bottle. These predictions were built using support vector regression. Several evaluation metrics were used for model evaluation. In addition, these regression models were compared to classification accuracies achieved in a prior work. When regression was used for classification, the results were somewhat poor; however, this was expected since the main purpose of the regression was not to classify the wines. Therefore, this paper also compares the advantages and disadvantages of both classification and regression. Regression models can successfully predict within a few points of the correct grade of a wine. On average, the model was only 1.6 points away from the actual grade and off by about $13 per bottle of wine. To the best of our knowledge, this is the first work to use a large-scale dataset of wine reviews to perform regression predictions on grade and price.
A Modified BA Anti-Collision Protocol for Coping with Capture Effect and Interference in RFID Systems
Authors: Hussein Isam A. , Jasim Basil H. , Ali Ramzy S.
Published: October 2018

Radio frequency identification (RFID) technology has widely been used in the last few years. Its applications focus on auto identification, tracking, and data capturing issues. However, RFID suffers from the main problem of tags collision when multiple tags simultaneously respond to the reader request. Many protocols were proposed to solve the collision problems with good identification efficiency and an acceptable time delay, such as the blocking anti-collision protocol (BA). Nevertheless, most of these protocols assumed that the RFID reader could decode the tag’s signal only when there was one tag responding to the reader request once each time. Hence, they ignored the phenomenon of the capture effect, which results in identifying the tag with the stronger signal as the multiple tags simultaneously respond. As a result, many tags will not be identified under the capture effect. Therefore, the purpose of this paper is to take the capture effect phenomenon into consideration in order to modify the blocking BA protocol to ensure a full read rate, i.e., identifying all the tags in the frame without losing any tag. Moreover, the modifications include distinguishing between collision and interference responses (for the period of staying tags) in the noisy environments, for the purpose of enhancing the efficiency of the identification. Finally, the simulation and analytical results show that our modifications and MBA protocol outperform the previous protocols in the same field, such as generalized query tree protocols (GQT1 and GQT2), general binary tree (GBT), and tweaked binary tree (TBT).
Slash-and-Burn Practices Decrease Arbuscular Mycorrhizal Fungi Abundance in Soil and the Roots of Didierea madagascariensis in the Dry Tropical Forest of Madagascar
Authors: Barraclough Alícia Donnellan , Olsson Pål Axel
Published: October 2018

Deforestation and the use of fire to clear land have drastic effects on ecosystem functioning and compromise essential ecosystem services, especially in low-income tropical countries such as Madagascar. We evaluated the effects of local slash-and-burn practices on soil nutrients and arbuscular mycorrhizal (AM) fungi abundance in a southwestern Madagascar forest. Nine sampling plot pairs were established along the border of a reserve within the Fiherenana–Manombo (pk-32) complex, where soil and seedling root samples of the endemic tree Didierea madagascariensis were taken. We analysed soil extractable PO43−, NH4+, and NO3− as well as total soil carbon and nitrogen. We analysed AM fungal abundance in soil and roots through fatty acid marker analysis (NLFA and PLFA 16:1ω5), spore extraction, and root staining. Slash-and-burn caused an increase in pH and doubled the plant available nutrients (from 7.4 to 13.1 µg PO43− g−1 and from 6.9 to 13.2 µg NO3− g−1). Total C and total N increased in deforested soil, from 0.6% to 0.84% and from 0.06% to 0.08%, respectively. There was a significant decline in AM fungi abundance in soil, with a decrease in soil NLFA 16:1ω5 from 0.2 to 0.12 nmol/g. AM fungi abundance in D. madagascariensis roots was also negatively affected and colonization decreased from 27.7% to 16.9% and NLFA 16:1ω5 decreased from 75.7 to 19 nmol/g. Together with hyphal network disruption, increased nutrient availability caused by burning is proposed as an explanation behind AM decline in soil and roots of D. madagascariensis. This is the first study to report the effects of slash-and-burn on AM symbiosis in Madagascar’s dry forests, with likely implications for other tropical and subtropical dryland forests worldwide where slash-and-burn is practiced.