bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study on dielectric barrier discharge plasma-assisted combustion for nozzle
Authors: Chen Chuan , Che Xueke , Zheng Tikai , Chen Qingya , Li Liang , Li Xiuqian
Published: August 2019

Aiming at the structure of small thrust rocket engine injector, a coaxial shear-type dielectric barrier discharge plasma nozzle was designed, and the effects of methane discharge and air discharge on combustion effect under different excitation and different mixing ratio conditions are studied. The results show that: the flashback occurs when the methane discharge voltage is high, the air discharge can broaden the blow off limit of the air/methane diffusion flame, and has the effect of stabilizing the flame and reducing the lift height.
Study on effect of surface roughness on resistance based on results from experiments and simulation with CFD and LBM
Authors: Guo Wenqiang , Hou Guoxiang
Published: August 2019

In this paper, the rotating disk with a diameter of 50mm is selected as a simplified object to study the effect of surface roughness on resistance. The accuracy of different CFD models is studied to reduce the simulation error through rheometer experiment of smooth disk. Then, optimized models are used to calculate the torque of rough disks with different roughness. Compared with results from rheometer experiment, it’s found that smooth disk doesn’t have pressure drag, but rough disk has pressure drag. And the disk surface with roughness of 90μm has the maximum drag reduction rate of 3.26% at speed of 400rpm. There is an uncertain and irregular relationship between drag reduction effect and surface microgroove under different Reynolds number, so, the flow in microgrooves on rough surfaces is simulated for further analysis by LBM. Compared with channel without microgroove, channel with microgroove reduces the velocity gradient on bottom wall and there is vortex in each microgroove. The velocity gradient on bottom wall attains a minimum when the height of microgroove is 90μm, which has the minimum viscous friction, however, the pressure difference between inlet and outlet of channel with microgroove height of 90μm doesn’t reach a minimum. Therefore, when applied to macroscopic objects, the microgrooves, which can reduce the viscous friction, probably increase the total resistance due to the pressure drag.
Effect of Inlet Flow-Guide on Hydraulic Loss of Seawater MHD Propeller with Helical Channel
Authors: Chen Xiaoqiang , Zhao Lingzhi , Peng Aiwu
Published: August 2019

Inlet flow-guide is very important to the hydraulic loss of the whole channel of marine MHD thruster with helical channel. In this paper, variable helix is used as the line-type of flow-guide blade, and helical loop number (N), blade number (n) and blade height (H) (helix height) are established as the main geometric parameters. L
16 (43) orthogonal table was used to design the inlet flow-guide, which contains three factors with four levels of N, n and H. The whole flow filed of helical channel with inlet flow-guide was numerical simulated with Fluent. The results show that the hydraulic loss of the helical channel can be greatly reduced by the inlet flow-guide; The results of orthogonal experimental show that the hydraulic loss of the helical channel is sensitive to the line-type of the guide vane, and the total hydraulic loss increases with the increase of n, increases first and then decreases with the increase of N, and decreases first and then increases with the increase of H.
Calculation and Analysis of Aerodynamic Parameters of Wing Based on NS Equation
Authors: Ma Hongxia
Published: August 2019

The emergence of computational fluid dynamics has greatly simplified the research and design process of aircraft. At present, this technology has become the most popular research field in fluid mechanics and is of great significance to promote the development of China’s aerospace and other undertakings. With the development of computational fluid mechanics, the numerical solution speed of the mean navier-stokes equations (RANS) has been greatly improved. In this paper, the M6 wing is taken as the calculation model, the RANS equation is coupled with the relevant calculation model, the pressure coefficient and aerodynamic characteristics are calculated and analyzed, and relevant conclusions are drawn.
Numerical simulation on high frequency discharge of chemical nonequilibrium argon inductively coupled plasma
Authors: Yu Minghao , Ma Libin , Bai Chuanxin , Liu Kai
Published: August 2019

This paper studied the flow field properties of the 10 kW inductively coupled plasma wind tunnel (ICPWT). The results can be used for the development of the thermal material protection material for re-entry aerospace vehicles. In this paper, the ICP flow under different input powers was numerically simulated, and the flow-field characteristics in the ICP torch under different operating parameters were obtained. The results showed that when the input power is the typical working power i.e. 10 kW, the electron number density in the plasma torch reaches a maximum of 3.23×1021 1/m3, and the electron temperature is also up to 0.99 eV. Besides, the velocity in the plasma torch reaches a maximum of 34.9 m/s, and the translational temperature also reaches a maximum value of 8740 K.
Investigation on the Scale Effect of Air Tanker with Pumping System resistance components
Authors: Xiao Zhijian , Xiao Junqing , Jiang Rong , Wu Bing , Wan Yuxiang
Published: August 2019

The ship viscous flow field of multiple scale models including real scale was calculated by using RANS method and SST k-ω model. The reliability of the method was verified by comparing the computed results with the experimental results at different scales. By studying the scale effect of various resistance components of a air tanker, it was found that the scale effect of total resistance and water resistance of the model with the pumping system was obvious, and the dimensionless air resistance coefficient almost kept constant at the studied range of Reynolds number. The additional resistance coefficient generated by pumping system increased with the increase of Reynolds number, and the resistance coefficients of the baler increased with the increasing Reynolds number.
Design and flow Simulation of compressed Air Energy Storage system in Aquifer
Authors: Liu Can
Published: August 2019

Compressed air energy storage is the most promising energy storage technology at present, and aquifer compressed air energy storage can achieve large-scale storage of compressed air by breaking the dependence of traditional compressed air energy storage on geological conditions such as large rock caves. Based on Kushnir’s study and some hypotheses, the mathematical model of compressed air energy storage in aquifer is established in this paper. Then, taking 3 MW energy storage scale as an example, the energy storage model of underground aquifer with buried depth of 800m in horizontal stratum is established by using numerical simulation method. The initial gas bag formation after gas injection and the parameters of pressure and gas saturation during the system cycle were analyzed. Experimental results show that the pressure and gas saturation change little after a complete cycle, and the effective gas phase volume of the available energy storage and energy release cycle decreases slowly with the cycle going on. The aquifer is widely distributed and well sealed, so it is feasible to store compressed air energy as a gas storage bank.
Numerical Simulation of Internal Flow and External Atomization in Pressure Swirl Nozzle
Authors: Wang Lei , Chen Longfei , Fang Bin
Published: August 2019

A computational fluid dynamics (CFD) study is carried out on the internal flow characteristics of pressure swirl nozzle and the breakup of external liquid film outside the nozzle. The numerical simulation of two-phase flow shows the unsteady characteristics inside the nozzle and the breaking mechanism of liquid film outside the nozzle. In the nozzle, the numerical simulation reveals the three-dimensional velocity distribution in the swirl chamber and the nozzle outlet. At the same time, the study shows that the breakup of liquid film is caused by the circumferential disturbance wave produced by R-T instability under the condition of 0.7 MPa inlet pressure. The influence of inflow characteristics on the instability of liquid film is pointed out.
Unsteady numerical simulation of flap vibration for 30P30N three-element airfoil
Authors: Ding Li , Xu Zhen
Published: August 2019

The pitching motion of NACA0012 airfoil and the flap vibration of 30P30N multi-element airfoil are simulated by using commercial fluid dynamics simulation software Fluent. The influence of flap vibration on lift coefficient and pitch moment coefficient of multi-element airfoil is analyzed. The results show that the influence of flap vibration on pitching moment coefficient of multi-element airfoil is greater. With the increase of flap amplitude, the variation range of lift and moment coefficients gradually increases, while with the increase of frequency, the variation range of lift and moment coefficients gradually decreases, and the hysteresis loop gradually becomes “thin” and its shape tends to ellipse. With the increase of flap vibration frequency, the unsteady effect of flow field increases, and the hysteresis loop may change in reverse direction.
Experimental investigation of flow separation in a planar convergent-divergent nozzle
Authors: Li Yaohua , He Chengjun , Li Jianqiang , Miao Lei , Gao Rongzhao , Liang Jinmin
Published: August 2019

Under the conditions of nozzle pressure ratio (NPR) of 2.79, 2.82 and 2.95, the flow field was observed by dynamic pressure measurement and focusing schlieren technique, and the flow separation characteristics of a planar convergent-divergent nozzle were studied. The results show that as the NPR increases, the nozzle flow structure changes from asymmetric to a symmetrical configuration. Under the condition of NPR=2.79, the flow in the nozzle goes obviously downward to the bottom wall of the nozzle, and the restricted shock separation (RSS) occurs on the bottom wall; under the condition of NPR=2.82 and NPR=2.95, the flow in the nozzle tends to be symmetrical, RSS appears on both the top and bottom walls. Based on spectrum analysis, it is found that there is obvious low-frequency oscillation characteristics near the separation point.
Numerical research on jet tab thrust vector nozzle aerodynamic characteristics
Authors: Cong Rongfei , Ye Youda , Zhao Zhongliang , Wu Junqiang , Zhang Changfeng
Published: August 2019

Jet tab thrust vector nozzle is a unique kind of thrust vector device which generates control force by inserting tab into the nozzle exhaust. The influence of tab geometric parameters on the nozzle aerodynamic characteristics is not clear. In order to meet the requirements of control rate modeling and optimization of jet tab thrust vector control system, a computational study was conducted to investigate the effects of tab geometric parameters which include insertion height, width, axial distance, incline angle on nozzle aerodynamic characteristics. The flow structure of nozzle with different tabs are demonstrated, and thrust vector performance is evaluated. Results indicate that the lateral force coefficient and the thrust loss coefficient increased with the increase of the tab insertion height, the thrust vector efficiency decreased as the insertion height increased; increasing tab width increased the thrust vector efficiency, the thrust vector efficiency increased by 24.8% when the tab width increased form 10mm to 18mm; both increasing axial distance and increasing tilt angle decreased the lateral force and efficiency, in practical application, the axial position and incline angle should be minimized.
Effect of Casing Movement on Flow and Heat Transfer Characteristics of Grooved Blade Tip
Authors: Zhang Yunsong , Liu Yongbao , Li Yujie , He Xing
Published: August 2019

Using numerical simulation method, the influence of casing movement on the flow and heat transfer characteristics in the groove tip has analysed, and the influence of rotation speed and blowing ratio was also considered. The results show that the casing movement reduces the casing temperature at the top of the rib and the Nu peak number at the bottom of the groove, it also reduces the mixing loss from the interaction of coolant and leakage flow. The higher the casing motion speed, the lower the average Nu on the wall surface and the smaller the mixing loss in the gap. Large blowing ratio cooling jet can effectively improve wall heat transfer.
Application of Fluid Dynamics in the Development of Communication Industrialization
Authors: Xu Lingrui , Xiong Xiong
Published: August 2019

Fluid mechanics has made great progress in recent decades, especially in the field of communication engineering, which is an important emerging direction. This paper provides an overview of the main essence and latest progress of this method. At the same time, it also discusses the development of relevant scientific and technological software and its impact on practical industrial applications.
Influence of turbulence boundary condition on pollutant diffusion for a natural draft cooling tower with flue gas injection
Authors: Yang Guangjun , Ding Li , Guo Zhaobing
Published: August 2019

The influence of the specification of turbulence model in equilibrium atmosphere boundary layer (ABL) on the numerical simulation of pollutant diffusion for a natural draft cooling tower with flue gas injection is investigated. The ABL must be considered due to the immense size of cooling tower. The flow field and pollutant distribution under the circumstance of different turbulence boundary conditions are predicted by solving Navier-Stokes (N-S) equations based on shear-stress transport (SST) k-ω turbulence model. The results indicate that the pollutant distribution remains almost unchanged when the turbulence boundary condition changed, it can be inferred that the turbulence boundary condition has little effect on the diffusion of pollutant for other Reynolds Average Navier-Stokes (RANS) turbulence models. Since RANS cannot consider the fluctuation velocity, it is not very suitable for predicting the pollutant diffusion. To more accurately simulate the pollutant propagation and diffusion, the large eddy simulation (LES) model is needed.
A lattice Boltzmann simulation of coalescence-induced droplet jumping on superhydrophobic surfaces
Authors: Ling Fengru , Huang Gang , Tang Hao , Geng Mengmeng , Ye Yutong , Qin Zhangrong
Published: August 2019

The coalescence-induced droplet jumping on superhydrophobic surfaces (SHSs) observed in nature plays a significant role in energy and environmental applications. By using a three-dimensional chemical-potential-based multiphase lattice Boltzmann model, the coalescence-induced jumping of two droplets and multidroplet are systematically simulated and analysed. The results show that the size and the number of droplets and the characteristics of pillared SHSs have a strong influence on the droplet behaviour. The coalesced droplet could only jump under appropriate droplet size and characteristic parameters of SHSs. Furthermore, coalesced droplets are more likely to jump and jump higher on SHSs with larger contact angle and pillar height and smaller distance between two pillars. This work will contribute to understand the phenomenon of the coalescence-induced droplet jumping and provide theoretical guidelines for the design of new SHSs.
The influence of OGV airfoil profile on the TRF
Authors: Li Shulei , Jin Donghai , Gui Xingmin , Li Jinwei
Published: August 2019

The outlet guide vane in a turbine rare frame plays a vital role in de-swirling the flow as well as load-bearing. This paper numerically simulates the performance of the single stage turbine with different airfoil profile design in the outlet guide vane. The result shows that the outlet guide vane with NACA65 profile has the best performance. The pressure growth in the suction side is steady and no obvious separation is found in the flow field.
Study on Flow Field Characteristics of Air Filter Intake System for Heavy Truck
Authors: Shi Pidong , Wang Renren , Cao Fang , Gao Chao , Wang Hongliang , Liu Zhihao
Published: August 2019

A three-dimensional watershed model of the intake system of the air filter for heavy trucks is built. The influence of the structure parameters of the intake pipe and cyclone separator on the flow field characteristics of the intake system is studied by using computational fluid dynamics (CFD) method, the parameters of the forward gas system are optimized. The results show: The internal structure of the intake pipe and cyclone separator is complex, so that pressure loss of the whole flow field is larger, and it affects the performance of the intake system.
Numerical study on the influence of the outlet width of vaneless diffuser on the performance of centrifugal compressor
Authors: Du Linfeng , Pan Yupeng
Published: August 2019

In this paper, the 3D model of the centrifugal compressor is established by Solidworks software at first. Second, the numerical simulation of the centrifugal compressor is carried out by using CFX software. Combined with the simulation results, the conclusion that properly reducing the outlet width of diffuser can effectively restrain the generation of flow separation and reduce the influence of impeller rotation on diffuser is revealed. Finally, the internal flow field structure and machine performance of the diffuser are improved. The research provides a reference for improving the performance and flow field structure of the compressor as well as the design of the vaneless diffuser.
Thermal analysis based on heat transfer equation
Authors: Mao Jie
Published: August 2019

When working in a high temperature environment, people need to wear special clothes to avoid burns. High-temperature special clothing can avoid burns, which greatly improves work safety. In order to design a special garment with high strength, heat insulation and low cost, we need to consider that the thickness of the clothes should not be too thick and increase the cost, and it should not be too thin to affect the function. So, we built a model through micro-element analysis to determine the thickness of the clothes. This allows the garment to reduce costs while ensuring insulation.
Numerical Simulation on Combustor of Impinging Stream Vortex Engine (ISVE)
Authors: Yu Xiaojing , Liu Yang , Pei Jingqiu
Published: August 2019

The impinging stream vortex engine (ISVE), with the advantages of strong thermal protection performance, low cost and simple structure, emerges as the times require. In this paper, the propellant mixing performance, atomization performance, combustion performance and thermal protection performance under different working conditions are calculated and analyzed by numerical simulation for the designed impinging swirl cooling thrust chamber, and the influence of thrust chamber structure on its flow and combustion performance is discussed. The results show that the wall temperature of the thrust chamber is lower than 400K, and the combustion efficiency reaches 93%. The double eddy current structure will strengthen the combustion reaction and make the top temperature of the thrust chamber too high, which will provide theoretical guidance for the next structural design of the thrust chamber.
Effect of grid and time step for predicting hydrodynamic resistance of blunt body
Authors: Wang Lili , Sun Kangning , Cai Yufeng , Jiao Jun , Zhang Jiaxu , Wang Mingzhen , Han Xiaohong , Xu Yongze
Published: August 2019

Taking the amphibious vehicle as an example, the hydrodynamic resistance was obtained by using computational fluid dynamics (CFD). This paper investigated the influent factors which contain mesh generation and time step which influences hydrodynamic calculation, and compared the calculation results with the relevant experimental results. This paper analyzed three factors which affecting amphibious vehicle’s resistance calculation, including the first grid thickness of boundary layer and ratio for extending surface mesh to the computational domain. By means of analyzing different factors, a high calculation precision strategy which could serve as reference for amphibious vehicle’s hydrodynamic resistance was obtained.
Numerical Simulation of Oxygen-Enriched Combustion of Low-Quality Coal in Cement Rotary Kiln
Authors: Li Song , Wang Jingfu
Published: August 2019

On the basis of the original four-channel burner, the oxygen-enriched channel is added to control the oxygen-enriched rate by adjusting the opening of the valve at the entrance of the oxygen-enriched channel. In actual production, the oxygen concentration in rotary kiln can be adjusted more flexibly to meet the combustion needs of different coal types in kiln and realize oxygen-enriched combustion under different oxygen concentration. A physical model of rotary kiln--burner is established in this paper, using FLUENT to increase the oxygen - channel rotary kiln burner structure for numerical simulation of combustion of pulverized coal. The distribution of velocity field, combustion temperature and component concentration field in kiln were analyzed, and the combustion characteristics of pulverized coal in kiln were compared between two kinds of burners. The calculation results show that the addition of oxygen-enriched channels will not cause significant changes in the velocity field in the rotary kiln, and can promote the combustion of pulverized coal in the rotary kiln, thus verifying the feasibility of adding oxygen-enriched channels.
Study on Heat Conduction Characteristics of Heat Insulation Wall Based on Airflow Reverse Osmosis Principle
Authors: Cao Dingyu , Fu Lequn , Lin Chuangting
Published: August 2019

Building energy saving is an important theme in the development of construction industry. It has important significance to achieve wall heat insulation. MATLAB software was utilized to model the heat transfer coefficient and obtain the main factors influencing airflow reverse osmosis principle based on the research of airflow reverse osmosis principle. The influence of seepage layer thickness and seepage velocity on thermal performance of airflow reverse seepage principle was determined and the optimal value was obtained through ANSYS simulation. An energy-saving plate was designed to build a removable house, and the heat conduction characteristics of air reverse osmosis principle were verified by experiments. The simulation results showed that heat conduction characteristics of the heat insulation wall based on airflow reverse osmosis principle were optimal when the thickness of the seepage layer is 40mm and the seepage velocity is 0.008m/s. The experimental results showed that the heat-shielding performance of the wall based on the airflow reverse osmosis principle was improved by 18.56%, and the thermal insulation performance was improved by 24.15% compared with that of the ordinary wall, and heat insulation wall based on airflow reverse osmosis principle had excellent heat conduction characteristics.
Numerical Simulation and Analysis of the dynamic Behaviours on the Spring-loaded Pressure Relief Valve
Authors: Gan Lifeng , Yu Xinhai
Published: August 2019

In this paper, in engineering practice, the computational fluid dynamics method was adopted to study the dynamic characteristics of the spring-loaded pressure relief valve. The effects of different parameters on the dynamic performance were investigated by CFD simulation. In the simulation, the damping coefficient has little influence on the discharge time and reseating pressure of the relief valve. With the decrease of spring stiffness, the reseating time of pressure relief valve increases, and reducing the spring stiffness can effectively reduce the reseating pressure. The reseating pressure decreases with the rise in the distance between the upper adjusting ring and the sealing face. This simulation results can provide a reference for the design and optimization of the structural parameters of the spring-loaded pressure relief valve.
Fluid-Structure Coupling Analysis of Non-linear Reciprocating Piston Seals in Series
Authors: Zhang Shouyuan
Published: August 2019

The reciprocating piston seals are crucial parts in hydraulic system which are widely used in aerospace and military industry. A direct fluid-structure coupling method with high efficiency is proposed for solving the transient Elaso-Hydrodynamic-Lubrication (EHL) problem in hydropneumatic suspension reciprocating piston seal system. Detailed 3D fluid-structure coupling model is built using finite element discretization. Material tests are carried out to obtain the parameters of the 3rd-oder Ogden constitutive model of the rubber O-ring. The sealing performance and friction force of the sealing system are analyzed in different piston speed. The critical speed from mixed lubrication to full film lubrication is obtained.
The application of numerical calculation method in determining the coefficient of S-type Pitot tube
Authors: Li Haiyang , Zhang Liang , Yao Xinhong , Zhang Jinming
Published: August 2019

In this paper, the coefficient of S-type Pitot tube is obtained by using numerical calculation method with the help of the computational fluid dynamics (CFD) software. The process includes designing the three-dimensional geometric models of the S-type Pitot tube being calibrated and the low speed wind tunnel used in calibrating the Pitot, meshing the 3D geometric model, setting calculation model and boundary conditions, solving mesh by using hydrodynamic equations, and obtaining the coefficient of the Pitot tube by post-processing of the calculation results. However, in order to verify the validity of the method, a real flow test of calibrating the K coefficient of S-type Pitot tube was carried out in a low speed wind tunnel. The result shows that all the Pitot tube coefficients at different velocity points have errors of less than 1.5% except for the minimum flow velocity point, which indicates the effectiveness of the numerical method.
Numerical simulation of the churning losses in vehicle rear axle hypoid gear
Authors: Huang Fengyun , Liu Weiteng , Zou Lin , Xu Jinli
Published: August 2019

A simplified 3D flow field numerical model of rear axle including passive bevel gear and the differential housing is established, based on the VOF (Volume of Fluid) model and the RNG k-ε turbulence model. With the model, the transient oil flow distribution and the influence law of speed, viccosity and bolt structure on the velocity field and the power losses is obtained. In general, the churning power losses increases with the rotational speed and viscosity while the rotational speed has more impact than viscosity on the power losses. The fluid region and the flow velocity increases with the rotational speed and the bolt structure causes a high speed area with the larger velocity gradient in the backflow surface of the bolts, implying the bolts can generate additional churning torque.
Network Analysis of Patenting Trends in Energy Efficiency
Authors: Bogomolova A , Balk I , Semenov E , Ivaschenko N
Published: August 2019

One of the most important topics of sustainability research and applications is reaching energy efficiency. In this paper we analysed more than 100,000 of patents related to different aspects of energy efficiency with the issue dates from 1973 to 2019. In the paper we will discuss how network theory can be applied to discover technology trends and apply them to improve sustainability efforts making more educated decision. This paper will demonstrate how patenting trends change with time and how different topics influence each other.
Elaboration of an Algorithm for the Efficient Use of Municipal Solid Waste Landfills
Authors: Rumyantseva A , Berezyuk M , Plastinina I , Rumyantseva E
Published: August 2019

The annual increase in generation and disposal of production and consumer wastes presents an ever pressing environmental, economic, and social challenge for modern industrially developed urbanized territories. As part of the waste management reform, an important issue is the restoration of old landfills for municipal solid waste (MSW). One of possible engineering solutions for the implementation of projects for the reburial of waste from old landfills is excavation of the landfill body with further sorting and extraction of landfill soil and, in some cases, recycled materials. This will reduce the amount of waste subject to reburial. The article examines several options for the implementation of the projects of old landfill restoration. It offers an algorithm for the efficient use of MSW landfills based on the data of environmental and economic analysis of some waste landfill restoration projects.
NaBaR(BO3)2 (R = Dy, Ho, Er and Tm): structurally perfect triangular lattice materials with two rare earth layers
Authors: Guo Shu , Kong Tai , Cava R J
Published: August 2019

We report the crystal growth of NaBaR(BO3)2 (R = Dy, Ho, Er and Tm) by the flux method. In the rhombohedral crystal structures, [RO6] octahedra and planar [BO3] units connect by bridging O atoms, forming triangular layers in the ab plane that are evenly spaced along c. Two perfectly triangular rare earth layers of identical dimension are found. Anisotropic magnetic susceptibility is observed for all; NaBaEr(BO3)2 is nearly isotropic while NaBaTm(BO3)2 is the most anisotropic. Heat capacity measurements reveal no long-range magnetic ordering down to 0.35 K for R = Dy or Er, while the Ho material displays a significant entropy loss. All the magnetic entropy appears to be absent in the Tm case by low temperature, suggesting that a singlet ground state may have formed.
Minimizing Risk and Maximizing Spatial Transferability: Challenges in Constructing a Useful Model of Potential Suitability for an Invasive Insect
Authors: Morey Amy C , Venette Robert C
Published: August 2019

Forecasting the spread and potential impacts of invasive, alien species is vital to relevant management and policy decisions. Models that estimate areas of potential suitability are useful to guide early detection and eradication, inform effective budget allocations, and justify quarantine regulations. Machine-learning is a rapidly emerging technology with myriad applications, including the analysis of factors that govern species’ distributions. However, forecasts for invasive species often require extrapolation into novel spaces, which may severely erode model reliability. Using the popular machine-learning platform, MaxEnt, we integrate numerous tools and recommendations to demonstrate a method of rigorous model development that emphasizes assessment of model transferability. Our models use Lymantria dispar dispar (L.) (Lepidoptera: Erebidae), an insect brought to the United States in the late 1860s from Europe and subsequently well monitored in spread. Recent genetic analyses provide evidence that the eastern North American population originated in Germany, France, and northern Italy. We demonstrate that models built and assessed using typical methodology for invasive species (e.g., using records from the full native geographic range) showed the smallest extent of extrapolation, but the worst transferability when validated with independent data. Conversely, models based on the purported genetic source of the eastern North American populations (i.e., a subset of the native range) showed the greatest transferability, but the largest extent of extrapolation. Overall, the model that yielded high transferability to North America and low extrapolation was built following current recommendations of spatial thinning and parameter optimization with records from both the genetic source in Europe and early North American invasion.
Klotho, the elusive kidney-derived anti-ageing factor
Authors: Sanchez-Niño Maria Dolores , Fernandez-Fernandez Beatriz , Ortiz Alberto
Published: August 2019

Chronic kidney disease (CKD) is one of the fastest growing causes of death worldwide. Only early diagnosis will allow prevention of both CKD progression and the negative impact of CKD on all-cause and cardiovascular mortality. Klotho is a protein produced by the kidneys that has anti-ageing and phosphaturic properties, preventing excess positive phosphate balance. There is evidence that Klotho downregulation is one of the earliest consequences of kidney injury. Thus the development of reliable assays to monitor Klotho levels may allow an early diagnosis of CKD and monitoring the impact of therapies aimed at preserving Klotho expression or at preventing CKD progression. However, the performance of Klotho assays has been suboptimal so far. In this issue of Clinical Kidney Journal, Neyra et al. explore methods to improve the reliability of Klotho assays.
Digging the topology of rock art in northwestern Patagonia
Authors: Vargas Fernando E , Lanata José L , Abramson Guillermo , Kuperman Marcelo N , Fiore Danae
Published: August 2019

We present a study on the rock art of northern Patagonia based on network analysis and communities detection. We unveil a significant aggregation of archaeological sites, linked by common rock art motifs that turn out to be consistent with their geographical distribution and archaeological background of hunter-gatherer stages of regional peopling and land use. This exploratory study will allow us to approach more accurately some social strategies of visual communication entailed by rock art motif distribution, in space and time.
Tricuspid regurgitation and long-term clinical outcomes
Authors: Chorin Ehud , Rozenbaum Zach , Topilsky Yan , Konigstein Maayan , Ziv-Baran Tomer , Richert Eyal , Keren Gad , Banai Shmuel
Published: August 2019

Aims

Tricuspid regurgitation (TR) is a frequent echocardiographic finding; however, its effect on outcome is unclear. The objectives of current study were to evaluate the impact of TR severity on heart failure hospitalization and mortality.

Methods and results

We retrospectively reviewed consecutive echocardiograms performed between 2011 and 2016 at the Tel-Aviv Medical Center. TR severity was determined using semi-quantitative approach including colour jet area, vena contracta width, density of continuous Doppler jet, hepatic vein flow pattern, trans-tricuspid inflow pattern, annular diameter, right ventricle, and right atrial size. Major comorbidities, re-admissions and all-cause mortality were extracted from the electronic health records. The final analysis included 33 305 patients with median follow-up period of 3.34 years (interquartile range 2.11–4.54). TR (≥mild) was present in 31% of our cohort. One-year mortality rates were 7.7% for patients with no/trivial TR, 16.8% for patients with mild TR, 29.5% for moderate TR, and 45.6% for patients with severe TR (P < 0.001). Univariate and multivariate analyses demonstrated a positive correlation between TR severity and overall mortality and rates of heart failure re-admission after adjustment for potential confounders. The proportional hazards method for overall mortality showed that patients with moderate [hazard ratio (HR) 1.15, 95% confidence interval (CI) 1.02–1.3, P = 0.024] and severe TR (HR 1.43, 95% CI 1.08–1.88, P = 0.011) had a worse prognosis than those with no or minimal TR.

Conclusions

The presence of any degree of TR is associated with adverse clinical outcome. At least moderate TR is independently associated with increased mortality.
Long-term survival following on-pump and off-pump coronary artery bypass graft surgery: a propensity score-matched analysis
Authors: Kirmani Bilal H , Guo Hui , Ahmadyur Omaid , Bittar Mohamad N
Published: August 2019

OBJECTIVES

Recent studies have once again brought into focus the long-term survival following off-pump coronary artery bypass grafting (OPCAB) compared with conventional on-pump coronary artery bypass grafting surgery (ONCAB). The aim of this study was to compare the long-term risk-adjusted survival rates in patients undergoing coronary artery bypass grafting (CABG) using these 2 techniques.

METHODS

We undertook a propensity score-matched analysis of 10 293 patients who underwent CABG at our single institution between 2000 and 2016. A logistic regression model was fitted using 14 covariates and their 2-way interactions to calculate an estimated propensity score [area under curve (AUC) 0.69], from which 1:1 nearest neighbour matching was performed. Patient survival was assessed using the Kaplan–Meier method and log-rank test.

RESULTS

Of the total cohort, 8319 patients had ONCAB and 1974 had OPCAB. Prior to matching, the OPCAB group had marginally higher EuroSCORE [3.7 ± 2.7 vs 3.5 ± 3, median (interquartile range) 3 (2–5) vs 3 (2–5), P = 0.016] and significantly lower average number of grafts per patient (2.39 ± 0.72 vs 2.75 ± 0.48, P < 0.001). Post-matching distributions between OPCAB and ONCAB showed a substantial improvement in balance in preoperative patient characteristics. The 2 surgery groups differed significantly in survival (P < 0.001). OPCAB demonstrated improved long-term survival at 10 years [84.8%, 95% confidence interval (CI) (82.7–86.9%) vs 75.8%, 95% CI (73.4–78.2%)] and 15 years [65.4%, 95% CI (61.4–69.6%) vs 58.5%, 95% CI (54.9–62.3%)]. Results of sensitivity analysis for 1:2 and 1:3 matched data were in concordance with these findings of survival.

CONCLUSION

At our institution, selected patients who underwent OPCAB had lower in-hospital morbidity and improved long-term survival when compared with a matched population of ONCAB patients.
Plastome Reduction in the Only Parasitic Gymnosperm Parasitaxus Is Due to Losses of Photosynthesis but Not Housekeeping Genes and Apparently Involves the Secondary Gain of a Large Inverted Repeat
Authors: Qu Xiao-Jian , Fan Shou-Jin , Wicke Susann , Yi Ting-Shuang
Published: August 2019

Plastid genomes (plastomes) of parasitic plants undergo dramatic reductions as the need for photosynthesis relaxes. Here, we report the plastome of the only known heterotrophic gymnosperm Parasitaxus usta (Podocarpaceae). With 68 unique genes, of which 33 encode proteins, 31 tRNAs, and four rRNAs in a plastome of 85.3-kb length, Parasitaxus has both the smallest and the functionally least capable plastid genome of gymnosperms. Although the heterotroph retains chlorophyll, all genes for photosynthesis are physically or functionally lost, making photosynthetic energy gain impossible. The pseudogenization of the three plastome-encoded light-independent chlorophyll biosynthesis genes chlB, chlL, and chlN implies that Parasitaxus relies on either only the light-dependent chlorophyll biosynthesis pathway or another regulation system. Nesting within a group of gymnosperms known for the absence of the large inverted repeat regions (IRs), another unusual feature of the Parasitaxus plastome is the existence of a 9,256-bp long IR. Its short length and a gene composition that completely differs from those of IR-containing gymnosperms together suggest a regain of this critical, plastome structure-stabilizing feature. In sum, our findings highlight the particular path of lifestyle-associated reductive plastome evolution, where structural features might provide additional cues of a continued selection for plastome maintenance.
Age Differences in Negative, but Not Positive, Rumination
Authors: Emery Lisa , Sorrell Anne , Miles Cassidy
Published: August 2019

Objectives

The main objective of this study was to determine whether there are age differences in positive and negative repetitive thought (ie, rumination).

Method

Young adults (ages 19–39; n = 114) and older adults (ages 60–85; n = 88) completed measures of negative and positive rumination. Bayesian analyses were used to determine whether age differences were present for both negative (young > old) and positive (old > young) rumination.

Results

There was extremely strong evidence for age differences in negative rumination, with lower scores in older adults. In contrast, the evidence was in favor of the null hypothesis for positive rumination.

Discussion

Age-related positivity is better characterized as decreased dwelling on the meaning of negative moods, rather than increased attention to positive ones.
Aberrant mitochondrial function in patient-derived neural cells from CDKL5 deficiency disorder and Rett syndrome
Authors: Jagtap Smita , Thanos Jessica M , Fu Ting , Wang Jennifer , Lalonde Jasmin , Dial Thomas O , Feiglin Ariel , Chen Jeffrey , Kohane Isaac , Lee Jeannie T , Sheridan Steven D , Perlis Roy H
Published: August 2019

The X-linked neurodevelopmental diseases CDKL5 deficiency disorder (CDD) and Rett syndrome (RTT) are associated with intellectual disability, infantile spasms and seizures. Although mitochondrial dysfunction has been suggested in RTT, less is understood about mitochondrial function in CDD. A comparison of bioenergetics and mitochondrial function between isogenic wild-type and mutant neural progenitor cell (NPC) lines revealed increased oxygen consumption in CDD mutant lines, which is associated with altered mitochondrial function and structure. Transcriptomic analysis revealed differential expression of genes related to mitochondrial and REDOX function in NPCs expressing the mutant CDKL5. Furthermore, a similar increase in oxygen consumption specific to RTT patient–derived isogenic mutant NPCs was observed, though the pattern of mitochondrial functional alterations was distinct from CDKL5 mutant–expressing NPCs. We propose that aberrant neural bioenergetics is a common feature between CDD and RTT disorders. The observed changes in oxidative stress and mitochondrial function may facilitate the development of therapeutic agents for CDD and related disorders.
Lower body ischaemic time is a risk factor for acute kidney injury after surgery for type A acute aortic dissection
Authors: Amano Kentaro , Takami Yoshiyuki , Ishikawa Hiroshi , Ishida Michiko , Tochii Masato , Akita Kiyotoshi , Sakurai Yusuke , Noda Mika , Takagi Yasushi
Published: August 2019

OBJECTIVES

Postoperative acute kidney injury (AKI) is known as a risk factor for death after surgery for Stanford type A acute aortic dissection under hypothermic circulatory arrest. It may also adversely affect long-term survival. We searched for modifiable risk factors for postoperative AKI, focusing on lower body ischaemic time.

METHODS

We reviewed 191 patients undergoing surgical repair for Stanford type A acute aortic dissection. The distal anastomosis depended on excluding the primary tear location, resulting in ascending/hemiarch (n = 119), partial arch (n = 18) and total arch replacement (n = 54). We defined an increase in the serum creatinine level to ≧2 times the baseline level as AKI. The incidence of AKI was investigated with multivariate analysis of its risk factors.

RESULTS

Postoperative AKI was observed in 49 patients (26%), 31% of whom required renal replacement therapy. The overall hospital mortality rate was 8.5%. Postoperative AKI, preoperative shock and organ malperfusion were predictors of hospital death. Multivariate stepwise logistic regression analysis identified age, body mass index, preoperative chronic kidney disease and lower body ischaemic time as risk factors for postoperative AKI.

CONCLUSIONS

Although surgical repair for Stanford type A acute aortic dissection showed favourable results, the incidence of postoperative AKI is still high, closely associated with hospital death. Lower body ischaemic time should be recognized specifically as a modifiable surgical risk factor for postoperative AKI.
Surgical correction of a pulmonary artery aneurysm with severe pulmonary regurgitation with a valve-sparing technique
Authors: Carino Davide , Mehta Nikita , Fernández-Cisneros Alejandro , Pereda Daniel
Published: August 2019

Pulmonary artery aneurysms are rare but are associated with a significant risk of rupture and dissection. Moreover, pulmonary valve regurgitation and/or stenosis often coexist. In this study, we present a case of a pulmonary artery aneurysm with severe pulmonary regurgitation in a patient with pulmonary hypertension treated with aneurysm resection and pulmonary valve repair.
Complexity of Strong Approximation on the Sphere
Authors: T Sardari Naser
Published: August 2019

By assuming some widely believed arithmetic conjectures, we show that the task of accepting a number that is representable as a sum of $d\geq 2$ squares subjected to given congruence conditions is NP-complete. On the other hand, we develop and implement a deterministic polynomial-time algorithm that represents a number as a sum of four squares with some restricted congruence conditions, by assuming a polynomial-time algorithm for factoring integers and Conjecture 1.1. As an application, we develop and implement a deterministic polynomial-time algorithm for navigating Lubotzky, Phillips, Sarnak (LPS) Ramanujan graphs, under the same assumptions.
The First Computer on the Moon
Authors: Hind Richard
Published: August 2019

To celebrate the 50th anniversary of the Apollo 11 lunar landing (20 July 2019), Richard Hind MBCS explores the computers that took Neil Armstrong and Buzz Aldrin to the surface of the moon.
Online and Hate Harassment
Authors: Aldridge David
Published: August 2019

The Universities UK Conference, on tackling online harassment, recently took place at the BCS offices in London. ‘It was clear from the speakers that we must do more as a society to safeguard the individual and prevent online harassment,’ writes Daniel Aldridge, Senior Policy Programme Manager at BCS
High Flying Data Collection With Drones
Authors: Hamilton Johanna
Published: August 2019

Matthew Greaves, founder of Drones on Demand, tells Johanna Hamilton AMBCS about his IT career facilitating transformative change and how he discovered a whole new data solution in the form of drones.
Mining social media for prescription medication abuse monitoring: a review and proposal for a data-centric framework
Authors: Sarker Abeed , DeRoos Annika , Perrone Jeanmarie
Published: August 2019

Objective

Prescription medication (PM) misuse and abuse is a major health problem globally, and a number of recent studies have focused on exploring social media as a resource for monitoring nonmedical PM use. Our objectives are to present a methodological review of social media–based PM abuse or misuse monitoring studies, and to propose a potential generalizable, data-centric processing pipeline for the curation of data from this resource.

Materials and Methods

We identified studies involving social media, PMs, and misuse or abuse (inclusion criteria) from Medline, Embase, Scopus, Web of Science, and Google Scholar. We categorized studies based on multiple characteristics including but not limited to data size; social media source(s); medications studied; and primary objectives, methods, and findings.

Results

A total of 39 studies met our inclusion criteria, with 31 (∼79.5%) published since 2015. Twitter has been the most popular resource, with Reddit and Instagram gaining popularity recently. Early studies focused mostly on manual, qualitative analyses, with a growing trend toward the use of data-centric methods involving natural language processing and machine learning.

Discussion

There is a paucity of standardized, data-centric frameworks for curating social media data for task-specific analyses and near real-time surveillance of nonmedical PM use. Many existing studies do not quantify human agreements for manual annotation tasks or take into account the presence of noise in data.

Conclusion

The development of reproducible and standardized data-centric frameworks that build on the current state-of-the-art methods in data and text mining may enable effective utilization of social media data for understanding and monitoring nonmedical PM use.