bluuebunny/crossref_metadata_2025 huggingface dataset:
Large eddy simulation of tip-leakage cavitating flow using a multiscale cavitation model and investigation on model parameters
Authors: Li Linmin , Huo Yakang , Wang Zhengdong , Li Xiaojun , Zhu Zuchao
Published: September 2021

For understanding tip-leakage cavitating flow features, the present work aims to implement a multiscale model to comprehensively reproduce the complicated phase structure. The volume of fluid (VOF) interface capturing method is applied to simulate macroscale cavities, while a discrete bubble model using the Lagrangian formulation is newly developed to take the microscale bubbles into account. The Schnerr–Sauer cavitation model is incorporated into the VOF model to calculate the mass transfer rate between phases from the macroscale point of view. For microscale bubbles, the simplified Rayleigh–Plesset equation is adopted to simulate the bubble growing and collapsing stages. An algorithm for coupling the approaches simulating macroscale cavities and microscale bubbles is also implemented to achieve multiscale simulation. Unsteady flow features are simulated using the large eddy simulation approach. The results show that an anti-diffusive compression scheme for the spatial discretization of volume fraction equation is relatively accurate for simulating the tip-leakage cavitating flow. Applying the multiscale model, the tip-leakage cavitating flow features with multiple time and space scales including the formation of glass cavity tube and the transport of bubble clouds can be revealed. Suitable model parameters including the coefficient of saturated pressure, and the bubble evaporation and condensation coefficients are studied.
Bluff body uses deep-reinforcement-learning trained active flow control to achieve hydrodynamic stealth
Authors: Ren Feng , Wang Chenglei , Tang Hui
Published: September 2021

We propose a novel active-flow-control strategy for bluff bodies to hide their hydrodynamic traces, i.e., strong shears and periodically shed vortices, from predators. A group of windward-suction-leeward-blowing (WSLB) actuators are adopted to control the wake of a circular cylinder submerged in a uniform flow. An array of velocity sensors is deployed in the near wake to provide feedback signals. Through the data-driven deep reinforcement learning, effective control strategies are trained for the WSLB actuation to mitigate the cylinder's hydrodynamic signatures. Only a 0.29% deficit in streamwise velocity is detected, which is a 99.5% reduction from the uncontrolled value. The same control strategy is found also to be effective when the cylinder undergoes transverse vortex-induced vibration. The findings from this study can shed some light on the design and operation of underwater structures and robotics to achieve hydrodynamic stealth.
Extended continuum models for shock waves in CO2
Authors: Alekseev I. , Kustova E.
Published: September 2021

Three continuum models extending the conventional Navier–Stokes–Fourier approach for modeling the shock wave structure in carbon dioxide are developed using the generalized Chapman–Enskog method. Multi-temperature models are based on splitting multiple vibrational relaxation mechanisms into fast and slow processes and introducing vibrational temperatures of various CO2 modes. The one-temperature model takes into account relaxation processes through bulk viscosity and internal thermal conductivity. All developed models are free of limitations introduced by the assumptions of a calorically perfect gas and constant Prandtl number; thermodynamic properties and all transport coefficients are calculated rigorously in each cell of the grid. Simulations are carried out for Mach numbers 3–7; the results are compared with solutions obtained in the frame of other approaches: multi-temperature Euler equations, model kinetic equations, and models with constant Prandtl numbers. The influence of bulk viscosity and Prandtl number on the fluid-dynamic variables, viscous stress, heat flux, and total enthalpy is studied. Bulk viscosity plays an important role in sufficiently rarefied gases under weak deviations from equilibrium; in multi-temperature models, non-equilibrium effects are associated with slow relaxation processes rather than with bulk viscosity. Using a constant Prandtl number yields over-predicted values of the heat flux. Contributions of various energy modes to the total heat flux are evaluated, with emphasis on the compensation of translational–rotational and vibrational energy fluxes.
Observation of von Kármán vortex street in a droplet breakup
Authors: Song Xianzhao , Jiang Lin , Xie Lifeng , Li Bin , Zhang Dan
Published: September 2021

We report the first observation of von Kármán vortex street in a droplet breakup induced by shock waves and high-speed fluid after the shock. To obtain these data, a novel experimental system is used to record the interaction between the droplet and shock wave and the following fluid. Details of flow fields and transients are also presented and discussed. Based on high-speed shadowgraphs, a Strouhal number of 0.28 ± 0.09 with a Reynolds number of 2817 is obtained, which is in good qualitative agreement with earlier experiments on the von Karman vortex street. The results suggest that the vortex-induced vibration may dominate the oscillation in the horizontal direction, which would result in resonance when the frequency of the oscillating flow matches the natural frequency of the droplet, thereby enhancing the deformation and breakup of the droplet. Our data may be useful to benchmark related multiphase flow models or nonlinear theories.
Ptychography: A solution to the phase problem
Authors: Guizar-Sicairos Manuel , Thibault Pierre
Published: September 2021

First envisioned for elucidating crystalline structures, the technique is now used for high-resolution lensless imaging, wavefront sensing, and more.
Holdfast coalescence between buoyant and non-buoyant seaweeds
Authors: Kelly Eleanor , Cowley Grace , Fraser Ceridwen I.
Published: September 2021

Some inherently poorly dispersive marine species have surprisingly large or patchy distributions that might be explained by rafting or ‘hitchhiking’. The genus Durvillaea (southern bull kelp) includes both highly buoyant and entirely non-buoyant species. Several of the non-buoyant, poorly dispersive species have puzzling distributions that are hard to explain without invoking long-distance dispersal hypotheses. We propose that these non-dispersive species of Durvillaea may be able to hitchhike with buoyant, dispersive congenerics by interspecific holdfast coalescence. Although many cases of intraspecific holdfast coalescence have been recorded, interspecific coalescence is less well documented. To determine whether interspecific holdfast coalescence occurs in Durvillaea, a rock platform on the south-east coast of New Zealand was surveyed, revealing multiple examples of naturally occurring interspecific holdfast coalescence. Samples were taken from coalesced holdfasts and genetic sequencing was performed to attempt to gauge whether tissue from both species was mixed throughout the holdfast or remained discrete. The discovery of interspecific coalescence between non-buoyant and buoyant Durvillaea raises the possibility that non-buoyant seaweeds may disperse with buoyant congenerics by rafting, and could help explain the distributions of various other non-buoyant macroalgae.
Reproductive biology and genetics.
Authors: Rees Paul A.
Published: August 2021

This chapter contains questions on the biology of reproduction, population dynamics and the genetics of animals living in zoos.
Conservation breeding and assisted reproductive technologies.
Authors: Rees Paul A.
Published: August 2021

This chapter contains questions on the role of zoos in conservation (captive) breeding programmes and the technologies that have been developed to assist in the reproduction of rare species.
Behaviour, training and environmental enrichment.
Authors: Rees Paul A.
Published: August 2021

This chapter contains questions on the behaviour of animals in zoos, the techniques used to train them and the environmental enrichment of their enclosures.
Answers.
Authors: Rees Paul A.
Published: August 2021

This part of the book contains the key to each question about the history of zoos and aquariums along with a brief explanation of why this is correct and, in some cases, what the distracters mean.
Developmental Validation of the Novel Six-Dye GoldeneyeTM DNA ID System 35InDel Kit for Forensic Application
Authors: Yang Qi , Yu Huan , Qu Yiling , Zhang Xiaochun , Xia Ruocheng , Wang Ziwei , Tan Rui , Xiong Lei , Xi Shihan , Wu Jun , Gao Yuzhen , Zhang Suhua , Li Chengtao
Published: August 2021

Insertion/deletion polymorphisms (InDels) have been treated as a prospective and helpful genetic marker in the fields of forensic human identification, anthropology and population genetics for the past few years. In this study, we developed a six-dye multiplex typing system consisting of 34 autosomal InDels and Amelogenin for forensic application. The contained InDels were specifically selected for Chinese population with the MAF ≥ 0.25 in East Asia, which do not overlap with the markers of Investigator® DIPplex kit. The typing system was named as GoldeneyeTM DNA ID System 35InDel Kit, and a series of developmental validation studies including repeatability/reproducibility, concordance, accuracy, sensitivity, stability, species specificity and population genetics were conducted on this kit. We confirmed that the 35InDel kit is precise, sensitive, species specific and robust for forensic practice. Moreover, the 35InDel kit is capable of typing DNA extracted from forensic routine case-type samples as well as degraded samples and mixture samples. All markers are proved to be highly polymorphic with an average observed heterozygosity (He) of 0.4582. The combined power of discrimination (CPD) is 0.999 999 999 999 978 and the combined power of exclusion in duos (CPED) and trios (CPET) are 0.978 837 and 0.999573, respectively, which are higher than those of the Investigator® DIPplex kit. Thus, the GoldeneyeTM DNA ID System 35InDel kit is suitable for forensic human identification and could serve as a supplementary typing system for paternity testing.
Quantifying fire severity: a brief review and recommendations for improvement
Authors: Han Dongdong , Di Xueying , Yang Guang , Sun Long , Weng Yuetai
Published: September 2021

Introduction:
Quantifying fire severity is an important aspect of studying the response mechanism of terrestrial ecosystems to wildfire, and it is of great significance to fire ecology. In this paper we comprehensively introduce and compare the classification and quantification methods for fire severity; we discuss the development and application status of various methods, and we elucidate their existing problems.
Results:
1) According to features of the burned area, fire severity can be classified as light, moderate, and heavy. 2) Using composite burn index (CBI) to quantify and record the fire severity. 3) In quantifying fire severity with vegetation change, there are certain limitations and theoretical problems to be solved. 4) Remote sensing could very well be an important means of measuring fire severity in the future, but there are still many problems that need to be solved before the remote sensing index can become a global fire severity indicator.
Discussion and Conclusion:
Only by clarifying the relationship between fire behavior, fire severity, time related variables and the pre- and post-fire ecosystem can the existing models be perfected or new, better fire severity measurement models be proposed for broad applications.
Increasing risks of crop failure and water scarcity in global breadbaskets by 2030
Authors: Caparas Monica , Zobel Zachary , Castanho Andrea D A , Schwalm Christopher R
Published: September 2021

As the greatest water user in the world, the agricultural sector is vulnerable to changes in climate and water resource availability. Understanding the impact of these changes on crop yield is critical in order to achieve and maintain global food security. We analyze output from an ensemble of Agricultural Model Intercomparison and Improvement Project models to project the probability of rice, soybean, maize, and wheat yield failures across global and national breadbaskets through mid-century. The probability of crop yield failures is projected to be as much as 4.5 times higher by 2030 and up to 25 times higher by 2050 across global breadbaskets. Crop failures are projected to be more likely when effects of CO2 fertilization are ignored. We utilize the open-source Aqueduct Water Risk Atlas to create a Water Scarcity Index composed of ten hydrological variables. The index reveals high water scarcity across crop breadbaskets in India, China, and the United States. If the ability to irrigate breadbaskets was eliminated due to water scarcity, the likelihood of crop failures would increase. Shifts in breadbaskets may cross national borders as crop yields will increase in Canada and decrease in the US as a response to a changing climate. Our analysis highlights top producing agricultural regions that have historically provided the global food system with large quantities of one or more major crops, but will face challenges in continuing to do so due to climate change and growing water scarcity.
Characteristics of medium-low rank coal blending on performance and efficiency steam power plant
Authors: Hendri  , Nurhasanah R , Lubis A F
Published: September 2021

Blending medium rank coal (MRC) with low-rank coal (LRC) is carried out to meet the caloric content which follows the boiler specifications. Negative effects of blending with LRC are environmental, specific fuel consumption (SFC), and efficiency issues. The purpose of this research is the optimum blending composition of LRC and MRC coal, which can be used by power plants. The research methodology used is to simulate coal blending with MRC percentage in the MRC-LRC from 0, 20%, 40%, 50%, 60%, 80%, and 100%. The type of coal used is categorized in MRC1, MRC2, LRC1, LRC2, LRC3. The combination used is MRC1-LRC1, MRC1-LRC2, and MRC2-LRC3. From the analysis obtained, if the MRC percentage in MRC-LRC blending increases, losses will decrease mass flow will decrease, SFC will decrease, and boiler efficiency will increase. Blending MRC2-LRC3 has the lowest losses, low mass flow with an average of 298.78 ton/h, low SFC with an average of 0.466 kg/kWh, and boiler efficiency between 84.85% to 85.71 %. Blending MRC2-LRC3 is most recommended for use in combustion plant with a minimum MRC2 percentage of 50%.
Optimization of shell and tube heat exchanger using the water cycle algorithm
Authors: Hanafi M F I M , Bahreininejad A , Uddin N
Published: September 2021

The shell and tube heat exchangers (STHEs) are used to transfer the thermal energy between two or more media. Due to its importance for conserving energy, numerous studies of heat exchanger design optimization have been carried out. The traditional design approaches are usually time-consuming, and may not guarantee to produce an economically optimal solution. A complete optimization procedure was conducted to find the minimum cost of the heat exchanger system. Heat exchanger design optimization was carried out using a recently proposed optimization algorithm called the water cycle algorithm (WCA). Three design variables are considered consisting of the shell inside diameter, tube outer diameter, and baffle spacing. The total annual costs which include the investment costs and the operating costs will be considered as the objective function.
Classification of Civet and Canephora coffee using Support-Vector Machines (SVM) algorithm based on order-1 feature extraction
Authors: Suyoto R Z H , Komarudin M , Nama G F , Yulianti T
Published: September 2021

Identification of coffee beans types is a process carried out in determining the category of civet and robusta coffee. The selection of civet coffee manually by the community in determining the variety of coffee beans. Manual selection makes the process slow. There is no certainty whether the selected coffee stated original civet coffee or a mixture with Robusta coffee. It needs to be built a system in identifying the types of coffee beans. In this study, the classification technology used for the selection process of Civet and Robusta coffee beans. This research uses first-order feature extraction with the Support-Vector Machines (SVM) algorithm, which aims to recognize civet and robusta coffee beans’ patterns using texture analysis on grayscale images and feature extraction. In the study, the authors used the Rapid Application Development approach to build the selection system. The data used in this study were 120 images, consisting of 110 training data and 10 test data. The accuracy in identifying the types of coffee beans by using this method is 87.27%.
Geophysical approach for assessment of seawater intrusion in the coastal aquifer of Bandar Lampung, Indonesia
Authors: Rustadi  , Darmawan I G B , Haerudin N , Suharno  , Setiawan A
Published: September 2021

Overexploitation in 1980-2000 caused a lot of groundwater loss in the aquifer coastal of Bandar Lampung. Groundwater has been degraded with increasing salinity due to the intrusion of seawater. In 2013, the intrusion extended 400 m from the coastline. Subsurface geological mapping is carried out to examine alluvial formation’s material constituents and the ability to transfer seawater to land. Three well explorations combined with three geoelectric tomography and 51 points of gravity. The gravity method is used to map structures that can connect coastal aquifers and land aquifers. Meanwhile, geoelectric tomography to map the presence of aquifers and low resistivity zones by seawater intrusion. The coastline has relatively shallow aquifers at a depth of 2-10 m in a sand layer with coral inserts, while the lower part is composed of silt and clay. The aquifer has experienced a decrease in resistivity of fewer than 10 ohms.m appears in the three circular patterns, caused by seawater. In addition to the permeable zone of shallow aquifers, there is a northwest-southeast trending structure that can channel seawater to land aquifers.
Investigation of conical draft tube of Kaplan turbine with spiral liner and without spiral liner using CFD simulation
Authors: Sirojuddin  , Ekayana I , Nugroho B C H , Aziz H R , Kholil A , Harahap S
Published: September 2021

The draft tube is a component in the Kaplan turbine to create positive suction pressure using kinetic energy that is not used when leaving the turbine runner and increasing turbine power efficiency. This research aimed to find out the highest efficiency of variant geometries of a conical draft tube with spiral liner and without the spiral liner. The design geometry was processed using 2D software and 3D using Inventor and simulated in CFD software. The inlet water discharge was 0.1 m³s−1 with head 5 m and theoretical turbine power 4.9 kW. Based on the simulation results showed that the spiral liner draft tube variant was the best power and efficiency.
Batik wastewater treatment by the hydrodynamic cavitation and Ozonation with coagulation-flocculation pretreatment
Authors: Saputra A E , Siahaan I N J , Karamah E F
Published: September 2021

Wastewater discharged by Batik’s industry still contains a high concentration of dyes and pollutants, thus can contaminate the water’s ecosystem. Because of that, in this study, Batik wastewater was treated by the hydrodynamic cavitation, ozonation, and combination of those two. By using PAC, a coagulation-flocculation-based pretreatment technic was conducted first to increase the effectiveness of the main wastewater treatment process. Then, variations in flow rate (2 L/min, 4 L/min, and 6 L/min) and initial pH of wastewater (4, 7, and 10) were evaluated to analyze its effect on the pH changing and the degradation of TSS, COD, color (Pt-Co), and TOC. The best result obtained from this research was by the application of the combination technic, which can eliminate 95.19%; 78.85%; 96.42%; and 60.56% of TSS, COD, color (Pt-Co), and TOC, respectively after 60 minutes treatment.
Influence of groundnut shell ash on compressive and tensile strengths of concrete
Authors: Samsunan  , Salena I Y , Rosiana  , Ruslaini
Published: September 2021

Research objectives are to determine the effect of groundnut shell ash used as partial cement replacement on concrete compressive strength. Groundnut shell ash obtained from the combustion results and passed sieve No. 200. Design mix is 21.7 MPa, with different variation percentage of groundnut shell ash in the order of 0%, 5%, 7.5%, 10% and 12.5% as partial replacement of cement for mixes. Total of 60 concrete specimens with 150 mm in diameter and height of 300 mm and tested for compression and tensile strength in 14 and 28 days. The result according to variations percentages in compression strength test on average at the age of 14 respectively were 18.495; 19.250; 20.382; 22.647 and 20.005 MPa. Whereas 28 days respectively were 18.495; 19.250; 20.382; 21.703 and 22.741 MPa. The results in tensile strength at the age of 14 respectively were 2.218; 2.029; 1.746; 1.557 and 1.463 MPa and 28-day age concrete respectively were 1.934; 2.029; 2.123; 2.029 and 1.840 MPa. The highest compressive and tensile strength in days 14 were 22.647 and 2.218, and in days, 28 were 22.741 and 2.123. It was observe that the strength has increased and groundnut shell ash seems promising material in concrete production.
Synthesis and characterization of hydroxyapatite bioceramics from shells of serai snail and mangrove crab in Tanjung Jabung beach: effect of milling process
Authors: Utami R , Gustiono D , Effendi M D , Roseno S , Fahyuan H D , Nasri M Z
Published: September 2021

Hydroxyapatite (HA) is a calcium phosphate compound that is used as a substitute for damaged body tissues, such as bone and dental implants. HA has been synthesized from the serai snail shells and the mangrove crab of west Tanjung Jabung, Jambi province using the dry method. Calcination of the shell at 1000 °C for 12 hours produces CaO, then contact of CaO with air produces Ca(OH)2which is used as a source of calcium in HA synthesis. Milling time variations for 0 hours, 3 hours, and 6 hours. Sintering at 600 °C for 2 hours produces HA as characterized by using X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and particle size analysis using Particle Size Analyzer (PSA). HA which has the highest accuracy of lattice parameters is that which is milling for 3 hours. The diffraction pattern shows the formation of the HA phase accompanied by several other calcium phosphate phases at an angle of 2θ. The FTIR spectrum shows the presence of PO43-and OH−groups from HA. PSA analysis shows the longer the milling makes the smaller particle size.
Physical, mechanical and corrosion properties of Zn-15Al alloy coating deposited at different voltage using thermal spray process
Authors: Yu-Song L , Bakar T A A , Ghandvar H , Fadil N A , Suhaili N
Published: September 2021

Steel is the most widely used metal on earth, cheap and found everywhere. It has good properties such as machinability, strength, ductility, and compatibility with other materials. However, it has weakness such as high corrosion rate which need to improve to achieve satisfying properties. The coating is one of the enhanced methods to improve the quality of steel coating methods are dipping and thermal deposition processes. Both processes have their own advantages and disadvantages. However, the thermal deposition method can produce a coating with better characteristics and performance. Zinc and aluminium are common metals to be used in the thermal spray process; however, a few parameters need to be concerned in the thermal spraying process. They include spraying voltage, spraying distance, deposition rate and applied current. The basic concept is that it melts the material and burst it to the substrate with high velocity. The purpose of this research is to evaluate the physical and corrosion properties of thermal sprayed pure zinc, aluminum and Zn-15Al alloy coating on a mild steel plate. The experimental procedures include roughness, thickness, adhesion, SEM with EDX, and EIS tests. The results show that at 30V, the surface roughness becomes lower, zinc’s decreases from 7.30um to 6.55um, Zn-15Al’s is from 8.52um to 7.93um. For aluminium, its surface roughness increases at higher voltage, from 13.10um to 18.25um. For coating thickness, the value of zinc, aluminium and Zn-15Al of 20V and 30V spraying voltage decreased from 629um to 601um, 486um to 452um, 541um to 536um respectively. The reason for sprays the material at higher velocity to the substrate; these findings depicted smooth and dense coating. Based on SEM/EDX analysis on the cross-sectioned samples, there is no gap between the coating and substrate and demonstrates good coating adhesion. The Daimler-Benz adhesion test shows all coating samples demonstrate good adhesion as no failure at the indentation boundary. In the EIS corrosion test, the frequency range 0.1Hz to 100kHz in 3.5wt.% NaCl solution, the highest impedance shown by zinc, aluminium and Zn-15Al at 20V are 21, 2122 and 49ohms; at 30V, they possess 11, 1347 and 20ohms. It illustrates those coatings with lower spraying voltages demonstrate better corrosion resistance due to the higher coating thickness. Hence, the coating which owns the best properties in all aspects is pure aluminum coating.
Oils and water absorption behavior of Biduri (Calotropis gigantea) fibers
Authors: Sukmawati A , Septiani W
Published: September 2021

This article reports on the oil and water absorption behavior of Biduri (Calotropis gigantea) fibres at room temperature. The material measured is a 100% raw material for Biduri (Calotropis gigantea) fibre, from 0.3 g to 1.5 g, and nonwoven structures made from 50/50, 60/40, 70/30, 80/20, and 90/10 mixture of Biduri and polyester. FTIR characterized the Biduri fibre, and the viscosity of used oil measured using Brookfield viscometer. The higher oils absorption at weight 0.3 g, 45.53 g/g, and water absorption at weight 0.3 g, 1.47 (g/g). The higher oil absorption at nonwoven structure showed at 90/10 composition, 42,86 g/g. It showed Biduri fibre is a natural absorbent that exhibits excellent hydrophobic and oleophilic properties.
Indonesian glider GL-1 spoiler preliminary design and computational fluid dynamics analysis using EASA CS-22 performance requirements
Authors: Mulyanto T , Zulkarnain M F
Published: September 2021

GL-1 is an Indonesian glider which is currently being developed using EASA CS-22 as its basis requirements. Spoiler is an important control mechanism in glider as it is used to control the glide slope of a glider. The design of spoiler includes configuration and dimension such as span, height, and position in wing. One of the requirements for spoiler design in EASA CS-22 is approach and dive performance. Compliance to the performance requirements needs aerodynamics analysis to find lift loss and drag gain due to spoiler extension. Several variable of spoiler dimension, such as the length, the height, and the gap, is varied to obtain a spoiler design which comply to the requirements. To simplify design and aerodynamic analysis process, a method of obtaining 3D aerodynamic characteristics from 2D airfoil with spoiler simulation is developed. 3D CFD simulations is used as a validation and to develop correcting factors. The spoiler dimension which complies to requirements are: 1.4-meter span, 90mm height, and location at 24 to 43% wing span.
Stochastic modeling of aircraft flight parameters in terminal control area based on automatic dependent surveillance-broadcast (ADS-B) data
Authors: Medianto R , Jusuf J , Oktafianto R , Atiqah R , Sembiring J , Pasaribu H M , Jenie Y I , Muhammad H
Published: September 2021

A critical step in developing good traffic management (ATM) system simulation model is to build a kinematic model of an aircraft movement that can represent the actual conditions. This study aims to obtain flight parameters for aircraft operating in the terminal control area of Soekarno-Hatta International Airport using Automatic Dependent Surveillance-Broadcast (ADS-B) data, which is openly available on Flight Radar24. Flight parameters were measured for several flight phases, such as take-off, initial climb, climb, cruise, descend, and final approach. In addition to these flight phases, flight parameters at waypoints on the arrival and departure were also measured. Furthermore, all flight parameters are modeled stochastically through the probability distribution function (PDF) approach. The best model for each parameter is obtained using the Maximum Likelihood method (MLE) with some relevant Kosmolgrove Smirnov Test criteria. The use of ADS-B data along with the stochastic model presented in this paper provides comprehensive information on flight behavior, which can be further utilized for an aircraft simulation model of an Air Traffic Management system.
Dynamic obstacle avoidance system for the unmanned aerial vehicle (UAV)
Authors: Rawikara S S , Sasongko R A
Published: September 2021

This paper presents a method for collision avoidance for moving obstacle based on ellipsoid geometry. Ellipsoid algorithm itself has been implemented in small unmanned aerial vehicle (UAV) for static obstacle avoidance. In extending the algorithm to dynamic object, two adjustments have been made, first is to calculate safe heading and selection of head or tail contact point. Using these two adjustments, the algorithm succesfully generates safe waypoint for dynamic obstacle avoidance and select which direction to use, whether it is to the head or the tail of obstacle moving direction.
V-Tail flutter analysis of wing-in-surface-effect (WISE) aircraft using a structural analysis software
Authors: Kusni M , Taufiqurrahman A , Gunawan L
Published: September 2021

Flutter is a dynamic aeroelastic instability that may cause structural failure and limits flight envelope of an aircraft. A passenger aircraft is required to be free from flutter and other aeroelastic instability phenomena, as stated in the regulations such as FAR 25. 33 / FAR 23.33. This paper presents the flutter analyses of the WISE aircraft using MSC Nastran. The analyses were carried out to the V-tail, one of the component where flutter might occur, by assuming rigid fuselage. Results of each analysis, in the form of velocity-damping and velocity-frequency curves, were evaluated to determine the critical flutter speed and frequency. First the analysis were conducted for sea level operation using KE, PK and PKNL methods which predict respectively the flutter speed of 1036 knot, 1037 knot, and 1037 knot. The three methods also consistently predict that the mode shapes involved in the flutter are the 5th mode and the 3rd mode. Then by using the PK-method, the analysis were repeated for air density variation. It is shown that the lower the air density, the higher the flutter speed is. It is concluded that tail flutter does not occur during the operation of the WISE craft with max operating speed of 80 knot.
Microstructure and twin behavior of Ti-2Al-2.5Zr during cold pilgering
Authors: Wu Jun , Zhaodandan Ma , Xiao Liu , Li Wang , Hui Wang , Jingjing Liao
Published: September 2021

The microstructure and twin behavior of Ti-2Al-2.5Zr tube during cold pilgering were investigated. During the deformation, the intragranular deformation is not uniform, and the microstructure characteristics are similar to low-cycle shear fatigue. Under alternating stress, the rotation tendency of grain is mainly related to the ratio of circumferential to radial strain. As the mainly primary twin, tensile {10–12}〈10–11〉 is activated in large number, which selection of twinning variant conforms to the Schmidt factor law. However, the selection of the secondary twinning variant is related to the slip system activated by the adjacent grains to accommodate the shear strain caused by the twins. The Schmidt factor of the secondary twin is determined by the slip system opened by the adjacent grains.
Effects of quenching and tempering heat treatment on microstructure, mechanical properties, and fatigue crack growth behavior of 51CrV4 spring steel
Authors: Lai Chaobin , Huang Wei , Li Shengci , Liu Tao , Lv Ruiguo , Tang Xiaoyong , Yu Jianlin
Published: September 2021

Herein, the microstructure, mechanical properties, and fatigue crack growth (FCG) behavior of 51CrV4 spring steels under different quenching and tempering heat treatment were studied. Results show that tempering temperature would not affect the prior austenite grain (PAG) size, while quenching temperature has a great influence on it; the volume fraction of carbide precipitates decreased with increasing quenching temperature. The width of martensite lath has little relationship with the prior austenite grain size. The mechanical properties of the investigated steels decreased with an increasing tempering temperature. Tempering temperature had a greater influence on the fatigue crack growth behavior compared with quenching temperature. The FCG of all the investigated steels were well interpreted by Paris model. When the quenching temperature was 840 °C, the stable expanding stage of the fatigue fracture was representative fatigue striations, fatigue steps and secondary cracks; multiple failure mechanisms coexisted in the rapid expanding stage; the fracture morphology of unstable failure stage was mainly dimples. When the quenching temperature increased to 880 °C and 920 °C, quasi-cleavage was observed in all the stages compared with the samples quenched at 840 °C. Secondary cracks, fatigue steps and crack closure could retard the FCG rate by consuming the driving force near the tip of fatigue crack.
Ultrafast photo-induced phonon hardening due to Pauli blocking in MAPbI3 single-crystal and polycrystalline perovskites
Authors: Xia Chelsea Q , Poncé Samuel , Peng Jiali , Ulatowski Aleksander M , Patel Jay B , Wright Adam D , Milot Rebecca L , Kraus Hans , Lin Qianqian , Herz Laura M , Giustino Feliciano , Johnston Michael B
Published: September 2021

Metal-halide perovskite semiconductors have attracted intense interest over the past decade, particularly for applications in photovoltaics. Low-energy optical phonons combined with significant crystal anharmonicity play an important role in charge-carrier cooling and scattering in these materials, strongly affecting their optoelectronic properties. We have observed optical phonons associated with Pb–I stretching in both MAPbI3 single crystals and polycrystalline thin films as a function of temperature by measuring their terahertz conductivity spectra with and without photoexcitation. An anomalous bond hardening was observed under above-bandgap illumination for both single-crystal and polycrystalline MAPbI3. First-principles calculations reproduced this photo-induced bond hardening and identified a related lattice contraction (photostriction), with the mechanism revealed as Pauli blocking. For single-crystal MAPbI3, phonon lifetimes were significantly longer and phonon frequencies shifted less with temperature, compared with polycrystalline MAPbI3. We attribute these differences to increased crystalline disorder, associated with grain boundaries and strain in the polycrystalline MAPbI3. Thus we provide fundamental insight into the photoexcitation and electron–phonon coupling in MAPbI3.
Ion dynamics in fluoride-containing polyatomic anion cathodes by muon spectroscopy
Authors: Johnston Beth I J , Baker Peter J , Cussen Serena A
Published: September 2021

Polyatomic anion insertion electrodes present compositional and morphological variety, as well as the ability to tune operational voltages by influencing the nature of metal-oxygen bonding. Realizing the application of these compounds as electrodes in Li- and Na-ion batteries requires a detailed understanding of ion dynamics in these systems. Here is presented the microscopic Li-ion and Na-ion diffusion properties in LiFeSO4F and Na2FePO4F, respectively, using muon spin relaxation (μ
+SR) spectroscopy for the first time. Li-ion diffusion processes in the tavorite LiFeSO4F phase are found to proceed with an activation energy (E
a) of 48(4) meV and a diffusion coefficient of 1.71 × 10−9 cm2 s−1, while Na-ion mobility in Na2FePO4F has a calculated diffusion coefficient of 3.47 × 10−10cm2 s−1 and a higher energy barrier to ion diffusion at 96(8) meV. This is the first such examination of fluoride-containing polyatomic cathodes using μ
+SR, where the presence of the highly electronegative fluoride species was thought to preclude activation energy and diffusion coefficient determination due to strong μ
+-F− interactions. These insights open up the possibility of studying a myriad of fluoride-containing electrode materials using the μ
+SR technique.
Explicit bound for the number of primes in arithmetic progressions assuming the Generalized Riemann Hypothesis
Authors: Ernvall-Hytönen Anne-Maria , Palojärvi Neea
Published: September 2021

We prove an explicit error term for the

ψ
(
x
,
χ
)

\psi (x,\chi )

function assuming the Generalized Riemann Hypothesis. Using this estimate, we prove a conditional explicit bound for the number of primes in arithmetic progressions.
On 𝐶² umbilical hypersurfaces
Authors: Mantegazza Carlo
Published: September 2021

We show by an elementary argument that the second fundamental form of a connected, totally umbilical hypersurface of class

C
2

C^2

is a constant multiple of the metric tensor. It follows that the hypersurface is smooth and it is either a piece of a hyperplane or of a sphere.
A diamond lemma for Hecke-type algebras
Authors: Elias Ben
Published: September 2021

In this paper we give a version of Bergman’s diamond lemma which applies to certain monoidal categories presented by generators and relations. In particular, it applies to: the Coxeter presentation of the symmetric groups, the quiver Hecke algebras of Khovanov-Lauda-Rouquier, the Webster tensor product algebras, and various generalizations of these.

We also give an extension of Manin-Schechtmann theory to non-reduced expressions.
Caregiver and provider perspectives on dual VA and Medicare Part D medication use in veterans with suspected dementia or cognitive impairment
Authors: Schleiden Loren J , Zickmund Susan L , Roman Katie Lynn , Kennedy Kayla , Thorpe Joshua M , Rossi Michelle I , Niznik Joshua D , Springer Sydney P , Thorpe Carolyn T
Published: August 2021

Purpose

Many older veterans with dementia fill prescriptions through both Veterans Affairs (VA) and Medicare Part D benefits. Dual VA/Part D medication use may have unintended negative consequences in terms of prescribing safety and quality. We aimed to characterize benefits and drawbacks of dual VA/Part D medication use in veterans with dementia or cognitive impairment from the perspectives of caregivers and providers.

Methods

This was a qualitative study based on semistructured telephone interviews of 2 groups: (1) informal caregivers accompanying veterans with suspected dementia or cognitive impairment to visits at a VA Geriatric Evaluation and Management clinic (n = 11) and (2) VA healthcare providers of veterans with dementia who obtained medications via VA and Part D (n = 12). We conducted semistructured telephone interviews with caregivers and providers about benefits and drawbacks of dual VA/Part D medication use. Interview transcripts were subjected to qualitative content analysis to identify key themes.

Results

Caregivers and providers both described cost and convenience benefits to dual VA/Part D medication use. Caregivers reported drawbacks including poor communication between VA and non-VA providers and difficulty managing medications from multiple systems. Providers reported potential safety risks including communication barriers, conflicting care decisions, and drug interactions.

Conclusion

Results of this study allow for understanding of potential policy interventions to better manage dual VA/Part D medication use for older veterans with dementia or cognitive impairment at a time when VA is expanding access to non-VA care.
Nephrotic syndrome and acute kidney injury following CoronaVac anti-SARS-CoV-2 vaccine
Authors: Unver Suat , Haholu Aptullah , Yildirim Sukru
Published: August 2021

A 67-year-old female with Type 2 diabetes mellitus developed nephrotic syndrome within 1 week of receiving the first dose of severe acute respiratory syndrome coronavirus 2 CoronaVac vaccine. A kidney biopsy was consistent with minimal change nephrotic syndrome and treatment was symptomatic with antiproteinuric therapy and improvement in proteinuria. Oedema returned within 1 week of the second dose of CoronaVac. On this occasion, acute kidney injury and massive proteinuria were noted. In kidney biopsy, glomeruli were normal, but tubulointerstitial inflammation consistent with acute tubulointerstitial nephritis was noted. Pulse followed by oral steroids was followed by recovery of kidney function. Proteinuria decreased after initiation of cyclosporine A.
Do data breaches damage reputation? Evidence from 45 companies between 2002 and 2018
Authors: Makridis Christos A
Published: September 2021

While data breaches have become more common, there is little evidence that companies that incur them experience a persistent decline in financial performance or security prices. Using new firm-level data between 2002 and 2018, this paper finds that firms experience a 26–29% increase in reputational intangible capital following an average data breach. However, the largest and most salient breaches are associated with a 5–9% decline in reputational intangible capital following a data breach. These effects are concentrated among firms in consumer-facing industries: smaller (larger) data breaches are associated with more positive (negative) effects. These results suggest that current regulatory guidance may not provide complete incentives for firms to invest in cybersecurity capabilities, particularly for small- to medium-sized breaches.
Interseismic deformation in the Gulf of Aqaba from GPS measurements
Authors: Castro-Perdomo Nicolás , Viltres Renier , Masson Frédéric , Klinger Yann , Liu Shaozhuo , Dhahry Maher , Ulrich Patrice , Bernard Jean-Daniel , Matrau Rémi , Alothman Abdulaziz , Zahran Hani , Reilinger Robert , Mai P Martin , Jónsson Sigurjón
Published: August 2021

Although the Dead Sea Transform (DST) fault system has been extensively studied in the past, little has been known about the present-day kinematics of its southernmost portion that is offshore in the Gulf of Aqaba. Here, we present a new GPS velocity field based on three surveys conducted between 2015 and 2019 at 30 campaign sites, complemented by 11 permanent stations operating near the gulf coast. Interseismic models of strain accumulation indicate a slip rate of $4.9^{+0.9}_{-0.6}~\mathrm{ mm}\,\mathrm{ yr}^{-1}$ and a locking depth of $6.8^{+3.5}_{-3.1}~\mathrm{ km}$ in the gulf’s northern region. Our results further indicate an apparent reduction of the locking depth from the inland portion of the DST towards its southern junction with the Red Sea rift. Our modelling results reveal a small systematic left-lateral residual motion that we postulate is caused by, at least in part, late post-seismic transient motion from the 1995 MW 7.2 Nuweiba earthquake. Estimates of the moment accumulation rate on the main faults in the gulf, other than the one that ruptured in 1995, suggest that they might be near the end of their current interseismic period, implying elevated seismic hazard in the gulf area.
Jennings v Rice [2002] EWCA Civ 159, Court of Appeal
Authors: Nair Aruna
Published: September 2021

Essential Cases: Land Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Jennings v Rice [2002] EWCA Civ 159, Court of Appeal. The document also includes supporting commentary from author Aruna Nair.
Stack v Dowden [2007] UKHL 17, House of Lords
Authors: Nair Aruna
Published: September 2021

Essential Cases: Land Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Stack v Dowden [2007] UKHL 17, House of Lords. The document also includes supporting commentary from author Aruna Nair.
MacLeod v Gold Harp Properties Ltd [2014] EWCA 1084, Court of Appeal
Authors: Nair Aruna
Published: September 2021

Essential Cases: Land Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in MacLeod v Gold Harp Properties Ltd [2014] EWCA 1084, Court of Appeal. The document also includes supporting commentary from author Aruna Nair.
William & Glynn’s Bank v Boland [1981] AC 487, House of Lords
Authors: Nair Aruna
Published: September 2021

Essential Cases: Land Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in William & Glynn’s Bank v Boland [1981] AC 487, House of Lords. The document also includes supporting commentary from author Aruna Nair.
Manchester Airport v Dutton [2000] 1 QB 133, Court of Appeal
Authors: Nair Aruna
Published: September 2021

Essential Cases: Land Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Manchester Airport v Dutton [2000] 1 QB 133, Court of Appeal. The document also includes supporting commentary from author Aruna Nair.
Horsham Properties Group Ltd v Clark [2008] EWHC 2327, High Court (Chancery Division)
Authors: Nair Aruna
Published: September 2021

Essential Cases: Land Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Horsham Properties Group Ltd v Clark [2008] EWHC 2327, High Court (Chancery Division). The document also includes supporting commentary from author Aruna Nair.
Halsall v Brizell [1957] Ch 169, High Court (Chancery Division)
Authors: Nair Aruna
Published: September 2021

Essential Cases: Land Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Halsall v Brizell [1957] Ch 169, High Court (Chancery Division). The document also includes supporting commentary from author Aruna Nair.
Tulk v Moxhay (1848) 41 ER 1143, High Court (Chancery Division)
Authors: Nair Aruna
Published: September 2021

Essential Cases: Land Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Tulk v Moxhay (1848) 41 ER 1143, High Court (Chancery Division). The document also includes supporting commentary from author Aruna Nair.
Robinson v Chief Constable of West Yorkshire [2018] UKSC 4
Authors: Purshouse Craig
Published: September 2021

Essential Cases: Tort Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Robinson v Chief Constable of West Yorkshire [2018] UKSC 4. The document also included supporting commentary from author Craig Purshouse.
Frost (or White) v Chief Constable of South Yorkshire Police [1999] 2 AC 455
Authors: Purshouse Craig
Published: September 2021

Essential Cases: Tort Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Frost (or White) v Chief Constable of South Yorkshire Police [1999] 2 AC 455. The document also included supporting commentary from author Craig Purshouse.
Murphy v Brentwood DC [1991] 1 AC 398
Authors: Purshouse Craig
Published: September 2021

Essential Cases: Tort Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Murphy v Brentwood DC [1991] 1 AC 398. The document also included supporting commentary from author Craig Purshouse.
Wilsher v Essex Area Health Authority [1988] 1 AC 1074
Authors: Purshouse Craig
Published: September 2021

Essential Cases: Tort Law provides a bridge between course textbooks and key case judgments. This case document summarizes the facts and decision in Wilsher v Essex Area Health Authority [1988] 1 AC 1074. The document also included supporting commentary from author Craig Purshouse.