bluuebunny/crossref_metadata_2025 huggingface dataset:
Long‐term evaluation of an EHC injection permeable reactive barrier in a sulfate‐rich, high‐flow aquifer
Authors: Molin Josephine , Valkenburg John , Seech Alan , Oesterreich Ryan , Son Jennifer
Published: June 2019

Permeable reactive barriers (PRBs) have traditionally been constructed via trenching backfilled with granular, long‐lasting materials. Over the last decade, direct push injection PRBs with fine‐grained injectable reagents have gained popularity as a more cost‐efficient and less‐invasive approach compared to trenching. A direct push injection PRB was installed in 2005 to intercept a 2,500 feet (760 meter) long carbon tetrachloride (CT) groundwater plume at a site in Kansas. The PRB was constructed by injecting EHC® in situ chemical reduction reagent slurry into a line of direct push injection points. EHC is composed of slow‐release plant‐derived organic carbon plus microscale zero‐valent iron (ZVI) particles, specifically formulated for injection applications. This project was the first full‐scale application of EHC into a flow‐through reactive zone and provided valuable information about substrate longevity and PRB performance over time. Groundwater velocity at the site is high (1.8 feet per day) and sulfate‐rich (~120 milligrams per liter), potentially affecting the rate of substrate consumption and the PRB reactive life. CT removal rates peaked 16 months after PRB installation with >99% removal observed. Two years post‐installation removal rates decreased to approximately 95% and have since stabilized at that level for the 12 years of monitoring data available after injection. Geochemical data indicate that the organic carbon component of EHC was mostly consumed after 2 years; however, reducing conditions and a high degree of chloromethane treatment were maintained for several years after total organic carbon concentrations returned to background. Redox conditions are slowly reverting and have returned close to background conditions after 12 years, indicating that the PRB may be nearing the end of its reactive life. Direct measurements of iron have not been performed, but stoichiometric demand calculations suggest that the ZVI component of EHC may, in theory, last for up to 33 years. However, the ZVI component by itself would not be expected to support the level of treatment observed after the organic carbon substrate had been depleted. A longevity of up to 5 years was originally estimated for the EHC PRB based on the maximum expected longevity of the organic carbon substrate. While the organic carbon was consumed faster than expected, the PRB has continued to support a high degree of chloromethane treatment for a significantly longer time period of over 12 years. Recycling of biomass and the contribution from a reduced iron sulfide mineral zone are discussed as possible explanations for the sustained reducing conditions and continued chloromethane treatment.
An Excellent Modifier: Carbon Quantum Dots for Highly Efficient Carbon‐Electrode‐Based Methylammonium Lead Iodide Solar Cells
Authors: Han Jianhua , Zhou Yu , Yin Xuewen , Nan Hui , Tai Meiqian , Gu Youchen , Li Jianbao , Oron Dan , Lin Hong
Published: June 2019

Low‐temperature paintable carbon‐electrode‐based perovskite solar cells (LC‐PSCs) are developed predominantly due to several significant advantages of carbon electrodes: they do not require a hole transport layer (HTL) and are low‐cost, easy to fabricate on a large scale, and possess high ambient stability. The most critical hindrance to the photovoltaic performance of LC‐PSCs is the inferior contact between the perovskite and carbon layers. Herein, carbon quantum dots (CQDs) as interface modifiers between the perovskite layer and carbon electrode are applied, which can facilitate hole injection into the carbon electrode, thus improving the photovoltaic performance of LC‐PSCs. Meanwhile, the crystalline properties and hole mobility of the perovskite layer are improved significantly, and defect states in the perovskite layer are passivated following the embedding of CQDs. Finally, a champion efficiency of 13.3% in LC‐PSCs based on perovskite‐CQDs hybrid films without HTL is achieved for an active area of 1 cm2, which represents a 24.3% improvement over the pristine device. Furthermore, LC‐PSC devices maintain more than 95% of their initial efficiency under demanding conditions (humidity >40%, 1000 h). This work opens up a promising pathway to improve the photovoltaic performance of LC‐PSCs and potentially also of other thin‐film solar cells.
FIMP dark matter candidate(s) in a B − L model with inverse seesaw mechanism
Authors: Abdallah Waleed , Choubey Sandhya , Khan Sarif
Published: June 2019

Abstract

The non-thermal dark matter (DM) production via the so-called freeze-in mechanism provides a simple alternative to the standard thermal WIMP scenario. In this work, we consider a popular U(1)
B−L
extension of the standard model (SM) in the context of inverse seesaw mechanism which has at least one (fermionic) FIMP DM candidate. Due to the added ℤ2 symmetry, a SM gauge singlet fermion, with mass of order keV, is stable and can be a warm DM candidate. Also, the same ℤ2 symmetry helps the lightest right-handed neutrino, with mass of order GeV, to be a stable or long-lived particle by making a corresponding Yukawa coupling very small. This provides a possibility of a two component DM scenario as well. Firstly, in the absence of a GeV DM component (i.e., without tuning its corresponding Yukawa coupling to be very small), we consider only a keV DM as a single component DM, which is produced by the freeze-in mechanism via the decay of the extra Z
′ gauge boson associated to U(1)
B−L
and can consistently explain the DM relic density measurements. In contrast with most of the existing literature, we have found a reasonable DM production from the annihilation processes. After numerically studying the DM production, we show the dependence of the DM relic density as a function of its relevant free parameters. We use these results to obtain the parameter space regions that are compatible with the DM relic density bound. Secondly, we study a two component DM scenario and emphasize that the current DM relic density bound can be satisfied for a wide range of parameter space.
Vanishing OPE coefficients in 4d $$ \mathcal{N}=2 $$ SCFTs
Authors: Agarwal Prarit , Lee Sungjay , Song Jaewon
Published: June 2019

Abstract

We compute the superconformal characters of various short multiplets in 4d

$$ \mathcal{N}=2 $$

N
=
2

superconformal algebra, from which selection rules for operator products are obtained. Combining with the superconformal index, we show that a particular short multiplet appearing in the n-fold product of stress-tensor multiplet is absent in the (A
1
, A
2n
) Argyres-Douglas (AD) theory. This implies that certain operator product expansion (OPE) coefficients involving this multiplet vanish whenever the central charge c is identical to that of the AD theory. Similarly, by considering the n-th power of the current multiplet, we show that a particular short multiplet and OPE coefficients vanish for a class of AD theories with ADE flavor symmetry. We also consider the generalized AD theory of type (A

k−1
, A

n−1) for coprime k, n and compute its Macdonald index using the associated W -algebra under a mild assumption. This allows us to show that a number of short multiplets and OPE coefficients vanish in this theory. We also provide a Mathematica file along with this paper, where we implement the algorithm by Cordova-Dumitrescu-Intriligator to compute the spectrum of 4d

$$ \mathcal{N}=2 $$

N
=
2

superconformal multiplets as well as their superconformal character.
The role of information provision in economic evaluations of non-invasive prenatal testing: a systematic review
Authors: John Nikita M. , Wright Stuart J. , Gavan Sean P. , Vass Caroline M.
Published: June 2019

Background

Technological progress has led to changes in the antenatal screening programmes, most significantly the introduction of non-invasive prenatal testing (NIPT). The availability of a new type of testing changes the type of information that the parent(s) require before, during and after screening to mitigate anxiety about the testing process and results.

Objectives

To identify the extent to which economic evaluations of NIPT have accounted for the need to provide information alongside testing and the associated costs and health outcomes of information provision.

Methods

A systematic review of economic evaluations of NIPTs (up to February 2018) was conducted. Medline, Embase, CINAHL and PsychINFO were searched using an electronic search strategy combining a published economic search filter (from NHS economic evaluations database) with terms related to NIPT and screening-related technologies. Data were extracted using the Consolidated Health Economic Evaluation Reporting Standards framework and the results were summarised as part of a narrative synthesis.

Results

A total of 12 economic evaluations were identified. The majority of evaluations (n = 10; 83.3%) involved cost effectiveness analysis. Only four studies (33.3%) included the cost of providing information about NIPT in their economic evaluation. Two studies considered the impact of test results on parents’ quality of life by allowing utility decrements for different outcomes. Some studies suggested that the challenges of valuing information prohibited their inclusion in an economic evaluation.

Conclusion

Economic evaluations of NIPTs need to account for the costs and outcomes associated with information provision, otherwise estimates of cost effectiveness may prove inaccurate.
Two Dimensional Visualization of Optic Chiasma in Fetus
Authors: Desai Purvi , Deshpande Shalmali Mohan , Chauhan Keshvi , Chauhan Binodini , Jhawar Manisha
Published: June 2019

The purpose of this study is to investigate methods to visualize and measure the fetal optic chiasma (OC) using transabdominal and/or transvaginal two-dimensional (2D) ultrasound in the coronal plane. The role of analyzing optic chiasma cannot be down scaled in prognosticating septo-optic dysplasia (SOD) and agenesis of septum pellucidum. This is a retrospective study of 117 random cases referred for various indications. The gestational age of the fetuses included in the study was between 19 and 37 weeks. The OC was visualized and measured in the 2D coronal plane with color Doppler by transabdominal and/or transvaginal routes. There were 97 normal low risk cases and 19 abnormal cases in the study. We conclude that it is possible to locate and measure OC width by transabdominal and transvaginal scans from 19 week onwards. It is possible to get equally good views by both, transabdominal and transvaginal routes.
Research Strategies on New Prefabricated Technology for Underground Metro Stations
Authors: Yang Xiuren , Huang Meiqun , Lin Fang
Published: June 2019

Based on the first successful application of new prefabricated technology in underground metro stations on line 2 of the Changchun Metro in China, a comprehensive analysis and discussion on research strategies for new prefabricated technology for large underground structures is provided. This paper introduces the application status of prefabricated technology in underground engineering worldwide, illustrates the different characteristics of prefabricated technology applied to ground buildings and underground structures, puts forward the key technologies, and compares the major technical, economic, and social benefits achieved. The successful application of prefabricated technology for underground structures in Changchun Metro demonstrates the feasibility and great advantages of the new prefabricated technology for underground engineering.
Predictive model of cardiac arrest in smokers using machine learning technique based on Heart Rate Variability parameter
Authors: Shashikant R. , Chetankumar P.
Published: June 2019

Cardiac arrest is a severe heart anomaly that results in billions of annual casualties. Smoking is a specific hazard factor for cardiovascular pathology, including coronary heart disease, but data on smoking and heart death not earlier reviewed. The Heart Rate Variability (HRV) parameters used to predict cardiac arrest in smokers using machine learning technique in this paper. Machine learning is a method of computing experience based on automatic learning and enhances performances to increase prognosis. This study intends to compare the performance of logistical regression, decision tree, and random forest model to predict cardiac arrest in smokers. In this paper, a machine learning technique implemented on the dataset received from the data science research group MITU Skillogies Pune, India. To know the patient has a chance of cardiac arrest or not, developed three predictive models as 19 input feature of HRV indices and two output classes. These model evaluated based on their accuracy, precision, sensitivity, specificity, F1 score, and Area under the curve (AUC). The model of logistic regression has achieved an accuracy of 88.50%, precision of 83.11%, the sensitivity of 91.79%, the specificity of 86.03%, F1 score of 0.87, and AUC of 0.88. The decision tree model has arrived with an accuracy of 92.59%, precision of 97.29%, the sensitivity of 90.11%, the specificity of 97.38%, F1 score of 0.93, and AUC of 0.94. The model of the random forest has achieved an accuracy of 93.61%, precision of 94.59%, the sensitivity of 92.11%, the specificity of 95.03%, F1 score of 0.93 and AUC of 0.95. The random forest model achieved the best accuracy classification, followed by the decision tree, and logistic regression shows the lowest classification accuracy.
Successful Management of Two Patients with Intracranial Hemorrhage due to Carpet Viper (Echis ocellatus) Envenomation in a Limited-Resource Environment
Authors: Benjamin Jordan M. , Chippaux Jean-Philippe , Tamou-Sambo Bio , Akpakpa Olouchégoun Cardinal , Massougbodji Achille
Published: June 2019

The West African carpet viper ( Echis ocellatus) causes more deaths than any other snake in sub-Saharan Africa. Carpet viper envenomations are characterized by a venom-induced consumption coagulopathy and systemic bleeding syndrome, in addition to local symptoms of painful progressive swelling and tissue destruction. The highest mortality rate is seen in the final stages of the syndrome, which typically ends with fatal internal bleeding or hemorrhagic shock. We present 2 cases of E ocellatus envenomation with intracranial hemorrhage seen at a rural hospital in Bembèrèkè, Benin, and describe the successful management of these patients in a limited-resource setting. In one case the patient was treated with an ineffective Indian-made antivenom before evaluation by the authors and continued to deteriorate until she was treated with effective antivenom 10 d after the bite. In both cases lumbar puncture was performed for diagnostic or therapeutic purposes with good effect, and both patients made full recoveries without sequelae. These cases demonstrate the remarkable ability of high-quality antivenoms to reverse life-threatening envenomations even in the final stages of the hemorrhagic syndrome and illustrate the dangers posed by low-quality antivenoms that have flooded the market in the developing world.
Friction Blister by Climbing Harness: A Case Report
Authors: Adhikari Subarna , Dawadi Suvash , Upadhyay Jenisha
Published: June 2019

An experienced 24-y-old climber on Mount Everest presented to the Base Camp medical clinic with a friction blister on his right flank. The blister was filled with clear fluid and was located about 3 cm posterior and 3 cm superior to the highest point of the right iliac crest, the site where a climbing harness would support the climber while hanging. A diagnosis of friction blister caused by a climbing harness used while traversing between Camp 2 and Camp 3 of Mount Everest was made. The blister was managed with hydrocolloid dressing, and the patient resumed climbing after 1 wk. The lesion healed with scarring at 2 wk. Friction blisters of the feet are common in climbers wearing ill-fitting shoes, but friction blisters caused by climbing harnesses are unusual and have not been reported in the literature as far as the authors are aware. All existing guidelines for blister management pertain to blisters of the feet, and there are inconsistencies in recommendations made by various authors. This unusual case in an extreme environment provides a good learning opportunity.
Heat and Freshwater Transport by Mesoscale Eddies in the Southern Subpolar North Atlantic
Authors: Müller Vasco , Kieke Dagmar , Myers Paul G. , Pennelly Clark , Steinfeldt Reiner , Stendardo Ilaria
Published: June 2019

A new data set of temperature and salinity fields reconstructed from satellite altimetry data between January 1993 and April 2014 is combined with satellite observations of mesoscale eddies in the subpolar North Atlantic between 40°N–55°N and 43°W–20.5°W. The data set is used to calculate the meridional heat and freshwater transports related to the propagation of eddies crossing 47°N, a latitude close to the boundary between the subpolar and the subtropical gyres. The largest heat and freshwater transports by eddies are observed in the western part of the Newfoundland Basin. Around 35–45% of the heat and freshwater transports by eddies across 47°N stem from individual isolated eddies with large thermohaline signatures. Northward moving cold and fresh cyclonic eddies carrying subpolar water from the Western Boundary Current make a considerable contribution to the overall heat and freshwater transport by eddies crossing 47°N. While the transport by individual eddies is negligible compared to the transport by the mean flow in this region, it can have a notable influence on the temporal variability. The analysis is repeated for a model simulation with 1/12° horizontal resolution for the period 2002–2013. The observed results are well reproduced in the model simulation; in particular, the modeled number of eddies crossing 47°N, the spatial distribution, and the associated heat and freshwater transports across this latitude are consistent with the observations.
Constraining the Large‐Scale Analysis of a Regional Rapid‐Update‐Cycle System for Short‐Term Convective Precipitation Forecasting
Authors: Tang Xiaowen , Sun Juanzhen , Zhang Ying , Tong Wenxue
Published: June 2019

This study examines the impact of a large‐scale constraint (LSC) on the large‐scale analysis and precipitation forecast of convective weather systems in a regional rapid‐update‐cycle system. The LSC is imposed by assimilating Global Forecast System forecast fields as bogus observations with a scale selection scheme. The scale selection is achieved by skipping data points of Global Forecast System forecast fields in the horizontal and vertical directions. It is shown that the LSC is able to modify the large‐scale component of the analysis fields while leaving the small‐scale component mostly intact compared with a control experiment without the constraint. The effects of the LSC on precipitation forecast are verified and analyzed using nine convective cases in the Rocky Mountain Front Range and its east plains. The results show that the LSC is effective in improving the precipitation forecast of different cases. However, the cases with weak large‐scale forcing show greater improvements than those with strong large‐scale forcing. Further analyses on the dynamic and thermodynamic variables indicate that the use of the LSC is able to construct a favorable environment for the initiation and development of convection in the case of weak large‐scale forcing, which leads to significant improvement of convective precipitation forecasting when radar observations are assimilated.
Ultraprecise Clock Will Facilitate Space Exploration
Authors: Kornei Katherine
Published: June 2019

NASA’s Deep Space Atomic Clock, slated to launch later this month for a demonstration flight, will help spacecraft more efficiently navigate the solar system.
An Investigation of VLF Transmitter Wave Power in the Inner Radiation Belt and Slot Region
Authors: Meredith Nigel P. , Horne Richard B. , Clilverd Mark A. , Ross Johnathan P. J.
Published: June 2019

Signals from man‐made Very Low Frequency (VLF) transmitters, used for communications with submarines, can leak into space and contribute to the dynamics of energetic electrons in the inner radiation belt and slot region. In this study we use ∼5 years of plasma wave data from the Van Allen Probe A satellite to construct new models of the observed wave power from VLF transmitters both as a function of L* and magnetic local time and geographic location. Average power peaks primarily on the nightside of the Earth for the VLF transmitters at low geographic latitudes. At higher latitudes the peak average power extends further in magnetic local time due to more extensive periods of nighttime in the winter months. Nighttime power is typically orders of magnitude more than that observed near noon, implying that loss rates from a given VLF transmitter will also maximize in this region. The observed power from any given VLF transmitter is tightly confined in longitude, with the nightside peak power typically falling by a factor of 10 within 10° longitude of the location of the peak signal. We show that the total average wave power from all VLF transmitters lies in the range 3–9 pT2 in the region 1.3<L*<3.0, with approximately 50% of this power emanating from three VLF transmitters, NWC, NAA, and DHO38.
Spatial Mapping of Fracture Aperture Changes With Shear Displacement Using X‐ray Computerized Tomography
Authors: Wenning Quinn C. , Madonna Claudio , Kurotori Takeshi , Pini Ronny
Published: June 2019

The shearing of fractures can be a significant source of permeability change by altering the distribution of void space within the fracture itself. Common methods to estimate the effects of shearing on properties, such as aperture, roughness, and connectivity, are incapable of providing these observations in situ. Laboratory protocols are needed that enable measurements of the spatial structure of the fracture aperture field in the medium, noninvasively. Here, we investigate changes in rough‐walled Brazilian‐induced tensile fracture aperture distribution with progressive shear displacement in Westerly granite and Carrara marble using a novel X‐ray transparent core holder. The so‐called calibration‐free missing attenuation method is applied to reconstruct highly resolved (submillimeter) fracture aperture maps as a function of displacement (0 to 5.75 mm) in induced fractures. We observe that shearing increases the core‐averaged fracture aperture and significantly broadens the distribution of local values, mostly toward higher apertures. These effects are particularly strong in Westerly granite and may be the result of the higher initial roughness of its fracture surfaces. Also, while the correlation length of the aperture field increases in both parallel and perpendicular directions, significant anisotropy is developed in both samples with the progression of shearing. The results on Westerly granite provide a direct indication that fracture aperture remains largely unaffected until 1 mm of displacement is achieved, which is important when estimating permeability enhancement due to natural and induced shear displacement in faults.
N2O Emissions From Two Agroecosystems: High Spatial Variability and Long Pulses Observed Using Static Chambers and the Flux‐Gradient Technique
Authors: Waldo Sarah , Russell Eric S. , Kostyanovsky Kirill , Pressley Shelley N. , O'Keeffe Patrick T. , Huggins David R. , Stöckle Claudio O. , Pan William L. , Lamb Brian K.
Published: June 2019

With the addition of nitrogen (N), agricultural soils are the main anthropogenic source of N2O, but high spatial and temporal variabilities make N2O emissions difficult to characterize at the field scale. This study used flux‐gradient measurements to continuously monitor N2O emissions at two agricultural fields under different management regimes in the inland Pacific Northwest of Washington State, USA. Automated 16‐chamber arrays were also deployed at each site; chamber monitoring results aided the interpretation of the flux gradient results. The cumulative emissions over the six‐month (1 April–30 September) monitoring period were 2.4 ± 0.7 and 2.1 ± 2 kg N2O‐N/ha at the no‐till and conventional till sites, respectively. At both sites, maximum N2O emissions occurred following the first rainfall event after N fertilization, and both sites had monthlong emission pulses. The no‐till site had a larger N2O emission factor than the Intergovernmental Panel on Climate Change Tier 1 emission factor of 1% of the N input, while the conventional‐till site's emission factor was close to 1% of the N input. However, these emission factors are likely conservative. We estimate that the global warming potential of the N2O emissions at these sites is larger than that of the no‐till conversion carbon uptake. We recommend the use of chambers to investigate spatiotemporal controls as a complementary method to micrometeorological monitoring, especially in systems with high variability. Continued monitoring coupled with the use of models is necessary to investigate how changing management and environmental conditions will affect N2O emissions.
Role of Proinflammatory Cytokines in Feedback Modulation of Circadian Clock Gene Rhythms by Saturated Fatty Acids
Authors: Kim Sam-Moon , Neuendorff Nichole , Earnest David J.
Published: June 2019

Proinflammatory signaling cascades have been implicated in the mechanism by which high fat diet (HFD) and saturated fatty acids (SFA) modulate fundamental circadian properties of peripheral clocks. Because the cytokines TNFα and IL-6 are key signals in HFD- and SFA-induced proinflammatory responses that ultimately lead to systemic insulin resistance, the present study examined the roles of these cytokines in the feedback modulation of peripheral circadian clocks by the proinflammatory SFA, palmitate. IL-6 and TNFα secretion in Bmal1-dLuc fibroblast cultures was increased during palmitate treatment although the time course and amplitude of the inductive response differed between these cytokines. Similar to the time-dependent phase shifts observed in response to palmitate, treatment with IL-6 or with the low dose (0.1 ng/ml) of TNFα at hour 12 (i.e., after forskolin synchronization) induced phase advances of fibroblast Bmal1-dLuc rhythms. In complementary experiments, treatment with neutralizing antibodies against these proinflammatory cytokines or their receptors to inhibit of IL-6- or TNFα-mediated signaling repressed palmitate-induced phase shifts of the fibroblast clock. These studies suggest that TNFα, IL-6 and other proinflammatory cytokines may mediate the feedback modulation of peripheral circadian clocks by SFA-induced inflammatory signaling.
Pyrroloindoline cyclization in tryptophan-containing cyclodipeptides mediated by an unprecedented indole C3 methyltransferase from Streptomyces sp. HPH0547
Authors: Li Hongxia , Qiu Yan , Guo Canxiong , Han Meng , Zhou Yuyang , Feng Yue , Luo Shizhong , Tong Yigang , Zheng Guojun , Zhu Shaozhou
Published: June 2019

The first indole C3 methyltransferase reported to catalyze pyrroloindoline cyclization in cyclic dipeptides, providing a feasible method to access diverse alkaloids.
Photo-switched magnetic coupling in spin-crossover complexes
Authors: Sun Hui-Ying , Meng Yin-Shan , Liu Tao
Published: June 2019

This feature article summarizes the recent progress in the magnetically coupled spin-crossover (SCO) complexes. The photo-switched molecular nanomagnet property, long range magnetic ordering, and the perspectives of SCO complexes are also presented.
Ionic-surfactants-based thermotropic liquid crystals
Authors: Huang Zhaohui , Qi Ping , Liu Yihan , Chai Chunxiao , Wang Yitong , Song Aixin , Hao Jingcheng
Published: June 2019

Ionic surfactants can be combined with various functional groups through electrostatic interaction, resulting in a series of thermotropic liquid crystals (TLCs).
Switchable nanoparticle for programmed gene-chem delivery with enhanced neuronal recovery and CT imaging for neurodegenerative disease treatment
Authors: Liu Linying , Li Yan , Liu Ruiyuan , Shen Qi , Li Yanhui , Shi Zhuyan , Shen Jie , Ji Weihong , Zhang Xin
Published: June 2019

A designed polymer–gold nanoparticle programmatically co-delivers genes and chemical drugs with precise conversions between the delivery pathway and specific diseased cells.
Power allocation based on SEP minimisation in three‐user two‐way channel
Authors: Jin Xianglan
Published: June 2019

A three‐user two‐way channel in which three users exchange their messages through a two‐way communication is considered by applying the physical‐layer network coding and the superposition coding. The equivalent squared minimum distance (ESMD) is derived as a criterion for power allocation by analysing the average symbol error probability (SEP). Optimal and suboptimal power allocations are proposed based on the ESMD maximisation under total power constraint. Inspired by the result, a proportional power allocation is proposed under per‐node power constraint. This scheme improves SEP at high signal‐to‐noise ratio (SNR) and consumes significantly less power. The average power consumption for each node is mathematically derived as a closed form. Furthermore, a compensation algorithm is introduced, which saves power and simultaneously achieves remarkable SEP improvement over entire SNR range. The numerical simulations over Rayleigh fading channels confirm the superiority of the proposed algorithms.
Design and analysis of a pulse capacitor charge power supply system based on novel brushless field assisted induction generator with flux control capability
Authors: Moradi CheshmehBeigi Hassan , Hamed Bibak Seyed , Karami Ehsan
Published: June 2019

This study presents design and analysis of a pulse capacitor charge power supply (CCPS) system by employing a novel brushless field assisted induction generator (BFAIG). Unlike the conventional induction generators, in the proposed configuration of this study, in addition to the phase windings, the stator utilises an assisted DC field coil, which is responsible for production of controllable flux inside the machine. As the main salient feature of including the DC field coil which increases controllability of the flux, providing a regulated terminal voltage in a very wide range appropriate for CCPS applications can be pointed out. In addition, due to the lack of brush and winding on the rotor in the proposed BFAIG, stability, long life and high reliability can be addressed as appropriate characteristics of this structure. Moreover, in this study, analytical design of the proposed BFAIG is presented and two‐dimensional magnetic‐field distribution is performed by using MagNet CAD package to verify the design procedure. On the basis of obtained results from electromagnetic‐field analysis, a CCPS is simulated and studied. The simulation results confirm the performance and efficiency of the presented CCPS.
Design of linear voice coil motor with semi‐closed structure
Authors: Luo Ciyong , Lin Zhonglan , Sun Jun
Published: June 2019

A Halbach permanent magnet (PM) tubular linear voice coil motor (LVCM) with a semi‐closed structure is developed to enhance the thrust density in this study. Generally, the end of conventional LVCM is open and suffers from the considerable end reluctance. The usage of Halbach array in LVCM makes this problem more prominent although it improves the air‐gap flux density greatly. The flux at the end of LVCM can be guided to improve the air‐gap flux density. Therefore, this study aims to constrain and direct the magnetic field at the end of a Halbach PM LVCM by using a ferromagnetic auxiliary yoke to construct a semi‐closed structure. Magnetic equivalent circuit method is utilised to analyse the effect of the auxiliary yoke on air‐gap flux density. Besides, finite element analysis is used to analyse the magnetic circuit and design the parameters of LVCM. The semi‐closed tubular LVCM topology is manufactured and the effectiveness of this topology is validated by experimental measurements. Results show that the thrust density of LVCM is improved effectively by using an auxiliary yoke at the end.
Online coherency identification and stability condition for large interconnected power systems using an unsupervised data mining technique
Authors: Barocio Emilio , Korba Petr , Sattinger Walter , Segundo Sevilla Felix Rafael
Published: June 2019

Identification of coherent generators and the determination of the stability system condition in large interconnected power system is one of the key steps to carry out different control system strategies to avoid a partial or complete blackout of a power system. However, the oscillatory trends, the larger amount data available and the non‐linear dynamic behaviour of the frequency measurements often mislead the appropriate knowledge of the actual coherent groups, making wide‐area coherency monitoring a challenging task. This paper presents a novel online unsupervised data mining technique to identify coherent groups, to detect the power system disturbance event and determine status stability condition of the system. The innovative part of the proposed approach resides on combining traditional plain algorithms such as singular value decomposition (SVD) and K‐means for clustering together with new concept based on clustering slopes. The proposed combination provides an added value to other applications relying on similar algorithms available in the literature. To validate the effectiveness of the proposed method, two case studies are presented, where data is extracted from the large and comprehensive initial dynamic model of ENTSO‐E and the results compared to other alternative methods available in the literature.
Hybrid data‐driven approach for truck travel time imputation
Authors: Karimpour Abolfazl , Ariannezhad Amin , Wu Yao‐Jan
Published: June 2019

Truck travel time data plays a critical role in freight performance measurement and is usually collected with probe‐vehicle technologies. However, due to low sampling rates, truck data usually suffers from missing values. The primary purpose of this study is to develop a hybrid model to accurately impute missing truck travel time data by leveraging multiple data sources. The proposed model imputes missing values by considering the interaction, similarity, and differences of the data as well as incorporating available historical information. The hybrid model achieves robust results by combining both probe vehicle and loop detector data to impute continuous missing truck travel time data in sparse datasets. The proposed model was used to impute missing truck travel time data in the National Performance Measures Research Dataset (NPMRDS). The imputation performance of the proposed model was compared with several popular imputation models including historical, spline interpolation, random forest, and bootstrapping EM. The results indicated that the proposed model was capable of imputing missing data in sparse datasets, notably when the data was missing continuously. With ∼13% mean‐absolute percentage error, the hybrid model outperformed other models in imputing an entire day of missing data.
Design of monofocal and bifocal lenses by new method and their application in high‐gain lens antenna based on chiral metamaterial
Authors: Hu Yanwen , Wang Yu , Xu Qiong , Yan Zhongming , Zhou Hongcheng , Zhou Wenying
Published: June 2019

A new method is proposed to design monofocal and bifocal lenses with the function of polarisation conversion based on chiral metamaterial (CMM). The phase distribution of lenses can be calculated more precise by the new numerical simulation method compared to the hyperbolic principle. The complete 360° transmission phase coverage at 1° phase intervals can be achieved by using the metallic split ring resonator and its two deformation structures. Monofocal lens can be realised by the hyperbolic method at microwave frequencies, but it is difficult to realise bifocal lens. The bifocal lens can be easily designed by the new method proposed in this study. The monofocal and bifocal high‐gain lens antennas are designed to verify the effectiveness of the new method. The performance of the single‐patch lens antenna designed by the new method is improved especially for its axial ratio, compared with the performance of the one designed by hyperbolic principle. The simulation peak gains of the two lens antennas designed by the new method are 18.1 and 18.7 dB at 9 GHz, respectively. The CMM‐based lens antennas are fabricated, and the measured results are in good agreement with the simulation results.
Auxiliary signal‐assisted droop‐based secondary frequency control of inverter‐based PV microgrids for improvement in power sharing and system stability
Authors: Firdaus Ayesha , Mishra Sukumar
Published: June 2019

This study proposes a modified decentralised droop controller for inverter‐based autonomous photovoltaics (PV) microgrids to address the problem of instability and slower power sharing between PV inverters. The proposed controller modifies the conventional droop mechanism in transient as well as in steady state by adding an auxiliary control signal in the power control loop of the inverters. The proposed approach offers three key benefits, i.e. improves active power sharing, enhances system stability and performs the secondary control action by nullifying the frequency deviation by using only one auxiliary signal in the control loop. The accuracy of the proposed modified droop controller is verified with the help of time‐domain simulations in MATLAB/SIMULINK. The results obtained show that the controller is able to improve the power sharing and stability of the microgrid as well as to restore frequency. The performance of the proposed control scheme is also validated by experimental results and small‐signal analysis.
Guidance control to capture a target using communication between the autonomous aerial vehicle and remote sensors
Authors: Kim Jonghoek
Published: June 2019

In this study, the authors introduce a three‐dimensional (3D) discrete‐time motion camouflage (MC) control to make an autonomous aerial vehicle (AAV) chase a manoeuvring target while not rotating the bearing line between the AAV and the target. This study handles a scenario in which the AAV can measure the target's position using remote sensors (e.g. ground‐based laser systems) only. Since there exists communication delay between the remote sensors and the AAV, time delay exists between the time instant when the target's position is measured and the time instant when the AAV applies controllers based on sensor measurements. Considering a scenario where the time delay is accessible, the authors develop a 3D MC control based on the time delay explicitly. They prove that as long as several assumptions are satisfied, the angular rate of bearing line is exactly zero at all sampling indexes while the distance between the target and the AAV monotonically decreases as time elapses. The effectiveness of the 3D discrete‐time MC control is verified utilising extensive MATLAB simulations.
Hybrid sensitivity‐correlation regularisation matrix for electrical impedance tomography
Authors: Borijindargoon Narong , Ng Boon Poh
Published: June 2019

In electrical impedance tomography, the primary task of image reconstruction process is to solve a discrete ill‐posed inverse problem. The estimated solution is commonly obtained under a regularisation framework so that the noise amplified solution, which occurs during the matrix inversion process, can be avoided. The regularisation framework aims at balancing the model‐data fitness while simultaneously constraining the solution space with additional prior (commonly prescribed through the regularisation matrix and solution‐norm). In this study, a relationship between two robust regularisation matrices namely Newton one‐step error reconstruction and fidelity‐embedded regularisation is explicitly highlighted in both spatial and singular value decomposition domains. A hybrid regularisation matrix which encompasses the two prior knowledge, non‐uniform sensitivity distribution and array response correlation, is then proposed as an alternative prior. Experimental results along with several evaluated performance parameters highlight the ability of the proposed prior to achieve a well‐balanced and robust performance.
Environmental feasibility of incorporation of electric taxis in South Africa
Authors: Singh Ranjay , Kumar Abhishek , Singh Arvind R. , Naidoo Raj , Bansal R. C. , Kumar Praveen
Published: June 2019

Public transport is very influential industry affecting our society due to its significant environmental and social impact. Policy makers have seen electric vehicle as a tool to reduce greenhouse gas emissions. Cleanliness of power from the electricity grid plays a vital role in environmental impact in the transition to electric vehicle. In countries like China, USA, India etc., majority of electricity generation is still dominated by fossil fuel fired generators. Thus, in some cases, the environmental impact of electric vehicle may be more adverse in comparison to conventional internal combustion engine vehicles (ICEV). This paper tries to study the environmental effect of incorporation of 100 Electric Vehicle taxies in Johannesburg (JNB), South Africa. Firstly, the current electricity generation scenario and vehicles standards of SA with its carbon emission is discussed. Secondly, it is shown that with the current generation mix the adoption of EV is not sustainable. Finally, penetration of Renewable Energy (RE) system at charging stations is proposed with Renewable Energy Fraction (REF) of 40% and 58% to make carbon mission from EV equivalent to Euro III and Euro V standards of petrol ICEV. The optimised size of RE system is found using the Electric System Cascade Analysis.
Smart coordination of battery energy storage systems for voltage control in distribution networks with high penetration of photovoltaics
Authors: Unigwe Obinna , Okekunle Dahunsi , Kiprakis Aristides
Published: June 2019

The use of battery energy storage systems (BESS) is one of the methods employed in solving the major challenge of overvoltage, experienced on low voltage (LV) distribution networks with high penetration of photovoltaics (PV). The overvoltage problem limits the penetration levels of PV into the LV network, and the benefits that could be gained. This paper presents a smart scheme for the coordination of multiple battery energy storage systems (BESS) in such networks. An approximate method was adopted for the evaluation of network voltage sensitivity, and the coordination algorithm was developed based upon this. Through the efficient selection, coordination and timing of charge and discharge operations of the BESS, the scheme maintains bus voltages within statutory ranges during both periods of high PV power generation and high network load demand. The scheme also prevents sudden voltage rise, which usually occurs in such networks immediately a BESS gets fully charged. Simulations were carried out on a real LV distribution network and results demonstrate the effectiveness of this approach.
Assessment of pulsating torque mitigation control strategy through tidal turbine emulation
Authors: Sousounis Marios Charilaos , Shek Jonathan K.H.
Published: June 2019

This article presents the modelling and assessment of a pulsating torque mitigation control strategy by using a tidal turbine emulator in a laboratory environment. Sudden changes and variability of the tidal flow velocity have the effect of creating pulsations on tidal current turbines. These pulsations have an adverse effect on tidal turbine fatigue and ultimate loading as well as the operation of the drivetrain. For the above reasons, a pulsating torque mitigation control strategy has been developed and tested which is based on modifying the reference maximum power point speed of the generator. This article presents the assessment of this pulsating torque mitigation control strategy in a laboratory setup. A 7 kW tidal current turbine is modelled in MATLAB/Simulink. The tidal turbine is emulated in the laboratory setup by using a torque‐controlled induction motor. Results show the effectiveness of the method in a laboratory environment, the ability of the generator to accelerate and decelerate based on the speed controller commands and the difference between the pulsating torque mitigation control strategy and maximum power point operation (MPPO). In addition, the experimental results are compared with a Simulink model which will show the accuracy of the modelling process.
Impact of large‐scale EV integration and fast chargers in a Norwegian LV grid
Authors: Lillebo Martin , Zaferanlouei Salman , Zecchino Antonio , Farahmand Hossein
Published: June 2019

Norway has implemented economic incentives over several years to encourage a transition from conventional vehicles to electric vehicles (EVs), and now has the largest share of EVs per capita in the world. In this study, the authors explore the impacts of increasing EV penetration levels in a Norwegian distribution grid, by using real power measurements obtained from household smart meters in load flow analyses. The implications of installing a fast charger in the grid have been assessed, and an optimal location for it is proposed, aiming at minimising both grid losses and voltage deviations. Moreover, the potential for reactive power injection to reduce the voltage deviations caused by fast chargers has been investigated. Results show that the EV hosting capacity of the grid is good for a majority of the end‐users, but the weakest power cable in the system will be overloaded at a 20% EV penetration level. The network tolerated an EV penetration of 50% with regard to the voltage levels at all end‐users. Injecting reactive power at the location of an installed fast charger proved to significantly reduce the largest voltage deviations otherwise imposed by the charger.
Impact of EV fast charging station on distribution system embedded with wind generation
Authors: Shukla Akanksha , Verma Kusum , Kumar Rajesh
Published: June 2019

This study presents the synergy between the electric vehicle (EV) fast charging station (FCS) and wind generation. A queuing analysis based 24‐h FCS charging demand is presented in the study. The uncertainty in wind speed variation is represented with a Weibull distribution function. The impact on the distribution system is analysed for EV penetration up to 50% and wind generation penetration up to 30%. The excess wind energy, reverse power flow, reduction in network losses and voltage deviation are investigated for the IEEE 123 bus radial distribution system to quantify the interaction between FCS and wind generation. The results show that 30% of wind generation is sufficient to supply 50% EV penetration and reduction in active and reactive energy loss is observed by 10.08% and 10.94%, respectively.
Design of an anti‐irradiation beam‐steering unit based on ASIC circuit
Authors: Xiao Wenguang , Yao Baidong
Published: June 2019

There are a large number of high‐energy particles in the space. These high‐energy particles induce a single‐event upset effect on DSP, FPGA, and other programmable digital controllers inside the beam‐steering unit, which can produce unpredictable and erroneous influences, thereby reducing the reliability of space‐borne‐phased array radars. In order to solve the above problems, this study presents a design of beam‐steering unit based on a kind of application‐specific integrated circuit (ASIC). By using the advantages of ASIC circuits such as strong radiation resistance, high integration, and low power consumption, this solution adopts an anti‐irradiation ASIC chip as a controller, and anti‐irradiation RS422 transceivers are used to complete interface conversion for receiving data and transmitting data. The beam refreshing and telemetry functions between the beam control computer and the 24 microwave modules are realised finally. The test result shows that the phase distribution time is <30 μs when the clock is 3.125 MHz, and the falling edge of sampling pulse is located at half the length of a data symbol, ensuring data hold time long enough to sample correctly.