bluuebunny/crossref_metadata_2025 huggingface dataset:
Forward modelling of MHD waves in braided magnetic fields
Authors: Fyfe L. E. , Howson T. A. , De Moortel I.
Published: September 2020

Aims. We investigate synthetic observational signatures generated from numerical models of transverse waves propagating in complex (braided) magnetic fields.

Methods. We consider two simulations with different levels of magnetic field braiding and impose periodic, transverse velocity perturbations at the lower boundary. As the waves reflect off the top boundary, a complex pattern of wave interference occurs. We applied the forward modelling code FoMo and analysed the synthetic emission data. We examined the line intensity, Doppler shifts, and kinetic energy along several line-of-sight (LOS) angles.

Results. The Doppler shift perturbations clearly show the presence of the transverse (Alfvénic) waves. However, in the total intensity, and running difference, the waves are less easily observed for more complex magnetic fields and may be indistinguishable from background noise. Depending on the LOS angle, the observable signatures of the waves reflect some of the magnetic field braiding, particularly when multiple emission lines are available, although it is not possible to deduce the actual level of complexity. In the more braided simulation, signatures of phase mixing can be identified. We highlight possible ambiguities in the interpretation of the wave modes based on the synthetic emission signatures.

Conclusions. Most of the observables discussed in this article behave in the manner expected, given knowledge of the evolution of the parameters in the 3D simulations. Nevertheless, some intriguing observational signatures are present. Identifying regions of magnetic field complexity is somewhat possible when waves are present; although, even then, simultaneous spectroscopic imaging from different lines is important in order to identify these locations. Care needs to be taken when interpreting intensity and Doppler velocity signatures as torsional motions, as is done in our setup. These types of signatures are a consequence of the complex nature of the magnetic field, rather than real torsional waves. Finally, we investigate the kinetic energy, which was estimated from the Doppler velocities and is highly dependent on the polarisation of the wave, the complexity of the background field, and the LOS angles.
Problems and Integrating Procedure of Quadcopter with Anemometer for Collect Wind Velocity Data
Authors: Budiprasojo Azamataufiq , Rudiyanto Bayu , Hariono Budi , Seetawan Tosawat
Published: September 2020

Wind speed profiles are generally sought by using an anemometer. However, problems occur when taking wind speed data over large areas, such as mapping the potential of wind energy in someplace. Altitude and coordinate variations will vary and difficult to executed if using a conventional anemometer. In this modern era where drones, which are unmanned Aerial Vehicles (UAVs) are increasingly used, have the prospect of being used as a tool in retrieving data. A type of drone that has an economical price is a quadcopter type drone. Integrating this drone with an anemometer will then be able to retrieve wind speed data at the coordinates and elevation. The wind speed survey process will be more accurate and can be saved in terms of cost and time. Problems and procedures in integrating these two tools will be studied in this study because both of these tools have specific characteristics such as turbulence from propeller drones that can interfere with data accuracy and sensitivity problems to the sensor anemometer that requires special attention. The development of quadcopter, including construction, modifying, and tuning, will be main issues to discuss in this journal.
Fuzzy Logic Controller Application for an Active Two-Axis Solar Tracking System
Authors: Imron Chairul , Abadi Imam , Brillianti Nurika , Khamim Asy’ari Muhammad , Ahmad Nor Yusilawati , Saepul Uyun Aep
Published: September 2020

The changes in the intensity of solar radiation cause the electrical power produced by solar panels to be not optimal. The solar panel position control system to the position of the solar is an effort to overcome this problem. There are four Light Dependent Resistor (LDR) sensors placed on the sides of the four cardinal directions. The difference in the intensity of solar radiation received by each sensor causes the position of the solar panel to turn perpendicular to the position of the solar. The control method used is fuzzy logic control with three membership functions. The controlled variables are pitch angle and yaw angle in an active two-axis solar tracking system. Input fuzzy logic control is an error, and output is PWM. The results of the performance of the pitch angle control system produce settling time for 10 s and error steady-state obtained by 0.080 %, while for the yaw angle control system produces settling time for 13 s and steady-state error is obtained at 0.038 %. The existence of a control system resulted in an increase in the percentage of power above 30 % with a power difference of 7.49 W to a fixed panel.
Performance Comparison of the Single Axis and Two-Axis Solar System using Adaptive Neuro-Fuzzy Inference System Controls
Authors: Imron Chairul , Abadi Imam , Amirul Akbar Ilham , Maknunah Jauharotul , Ahmad Nor Yusilawati , Saepul Uyun Aep
Published: September 2020

Solar energy is one of the renewable energy that gets more attention from many countries. Solar photo voltaic (PV) takes the right position to get the maximum energy yield. The study was conducted by comparison of performance with two methods of tracking the sun with one axis and two axes by using ANFIS control (Adaptive Neuro-Fuzzy Inference System). The solar tracking system is a system that operates on the sun by using a light sensor and controls the photovoltaic to always perpendicular to the sun by changing the pitch and yaw axis of the sun tracing properties. LDR (Light Dependent Resistor) is one of the light sensors whose resistance changes depending on the intensity of incoming light. Direct current (DC )motor is used as a PV drive panel in a solar tracking system. A two-axis solar tracking system has a greater power output than a tracking system with a single photovoltaic panel that does not use a tracking system (fixed).
Manufacturing Risk Identification in the Steel Industry
Authors: Dewi Dharu , Bastori Imam , Tris Yuliyanto Arief , Stankevica Karina , Soetrisnanto Arnold
Published: September 2020

The steel manufacturing industry is an inseparable part of the nuclear power plant construction project. This industry is a business full of dynamics, risks, and challenges. The implementation of risk management becomes an obligation that must be executed in managing this very complex project. In general, risk management in manufacturing includes steps to understand and identify potential problems that may occur, evaluate, monitor, and handle risks. The main risk management objectives are to prevent or minimize adverse effects due to unforeseen events through risk aversion or preparation of contingency plans related to those risks. This paper describes the identification of risk factors and assessments using the Boston Matrix. The results of the analysis show that unrealistic schedules, skill not appropriate, not available equipment, transportation barriers to the workshop, fluctuations in steel material prices, wrong specifications from owner, incorrect interpretation of specifications, misinterpretation of drawings, incorrect volume, material storage, wrong cutting, incorrect installation, and wrong order are factors with moderate and high risk.
Solar Power in the Island Nation, Mauritius
Authors: Rughoo Dhirajsing
Published: September 2020

The challenges to integrating a greater share of renewable energy, more specifically solar energy into the power grid in tropical islands are that these islands have a complex microclimate, high humidity and high cloud coverage. Because of this, the power output from solar photovoltaic (SPV) plants is severely affected. In this manuscript, the results of a study carried out on the performance of a 15.2 MW solar photovoltaic (SPV) plant in the island nation Mauritius is presented. The net annual yield was 22 162 MWh and has avoided 22 162 metric t of CO2 emission into the atmosphere. An attempt is also made to develop a model to forecast the power that can be generated from the SPV plants at that location. The grid operator, the national Central Electricity Board (CEB) needs to know a priori, the energy mix for the subsequent few days so that the level of operation of fossil fuel fired thermal plants can be tuned accordingly to minimize the environment pollution of this pristine island.
Potential of New and Renewable Energy in Merauke Regency as the Future Energy
Authors: Hariyanto Hariyanto , Parenden Daniel , Vincēviča-Gaile Zane , Gamawati Adinurani Praptiningsih
Published: September 2020

Electricity consumption in Merauke Regency increases every year in line with economic growth and population growth. Meanwhile, fossil energy reserves as fuel for power plants have decreased. To reduce dependence on fossil energy and offset the increase in electricity consumption it is necessary to develop alternative electrical energy sourced from renewable energy. Merauke Regency has great potential for renewable energy derived from biomass, solar, and wind. A study or analysis is needed to be able to estimate the energy potential that can be developed in an area. This study uses data collection techniques and analysis of the potential for renewable energy in Merauke Regency using RETScreen Expert. Analysis results show the potential of solar energy, and the most potential biomass energy to be developed.
Development of Moving Equipment for Fishermen’s Catches using the Portable Conveyor System
Authors: Susanto Herry , Hendroko Setyobudi Roy , Muhammad Nur Syukri , Yandri Erkata , Saepul Uyun Aep , Yaro Abubakar , Abdullah Kamaruddin , Krido Wahono Satriyo , Burlakovs Juris , Adhi Nugroho Yogo
Published: September 2020

Indonesia is an archipelago that has a wealth of marine fish resources, and the country with the second-longest coastline in the world. The improvement witnessed in the economy of Indonesia in recent years, is as a result of the growth experienced in various sectors, among which is the fisheries and marine. To overcome this problem, a portable conveyor system of moving equipment for fishermen’s catches was designed. It can be placed at the dock or port where the fishermen are anchored and unloading the fishermen’s catches from the sea. It designed to have the ability to move up and down in the moving frame, making this conveyor system can be used both in high tides and low tides of seawater level conditions. The advantage of this portable conveyor system is could be done continuously with a little human power. Other than that, from the results of the calculations, known that with increasing motor rotation, the required traveling time will only become shorter. The resulting conveyor capacity shows an increase. Also, it can use drive motors that are available on the market with a power capacity of 0.37 kW. Therefore, the process of this portable conveyor system can be more efficient.
Polyol Modification of PEDOT: PSS as Hole Transport Material Affects the Performance and Stability of Calcium Titanate (CaTiO3) Solar Cell and UV Photodetector
Authors: Ernawati Lusi , Abat Amelenan Torimtubun Alfonsina , Arofai Teguh , Yani Adhya , Huda Thorikul , Agung Wahyuono Ruri
Published: September 2020

This report a novel and straightforward architecture of CaTiO3based solar cells with optimized hole transport material (HTM) properties. The perovskite CaTiO3particle was prepared via the solution process using different CaCO3/TiO2ratios. The design of CaTiO3-based solar cell follows the inverted architecture, in which poly (4-styrene sulfonate)-doped poly (3, 4-ethylenedioxy-thiophene (PEDOT:PSS) and PCBM-C70 were used as HTM and electron transport layer (ETL), respectively. Charge mobility of HTM was modified and improved by using either ethylene glycol (EG) or diethylene glycol (DEG). The optimum condition of CaTiO3-based solar cell was obtained using CaCO3/TiO2ratio of (1:7) annealed at 900 °C and 44.4 % (v/v) DEG-modified PEDOT/PSS. The conversion efficiency of 3.1 % with a stable solar cell performance up to 72 h under the ambient condition without encapsulation was achieved.
The Effect of Activated Carbon Addition on Woody Cutting Waste Briquette Combustion Quality
Authors: Ayunina Maulida Okta Arifianti Qurrotin , Anggarini Ufafa , Nafis Akbar , Rosita Sari Erny , Fidiya Nugrahani Elita
Published: September 2020

This study aims to increase the calorific value of woody cutting waste briquette by adding activated carbon. The previous experiments showed that the highest calorific value of woody cutting waste briquette reached only 3 630 kCal kg–1. In this research, activated carbon was made of Palmyra palm fiber using H3PO4as an activator solvent. There are four different proportion of activated carbon used in the experiment, for example, 5 %, 10 %, 15 %, and 20 % with 10 % tapioca flour binder. The woody cutting waste were carbonized and sieved into 50 mesh to 100 mesh. The briquette performance was tested using proximate analysis, bomb calorimeter, and combustion analysis. The addition of activated carbon in briquette could increase the calorific value from 3 630 kCal kg–1to around 4 500 kCal kg–1.
Analysis of Voltage Unbalance and Energy Loss in Residential Low Voltage Distribution Systems with Rooftop Photovoltaic Systems
Authors: Charoenwattana Rattanaprapa , Sangpanich Umarin
Published: September 2020

This paper investigates effects of voltage unbalance and energy losses due to the connection of rooftop photovoltaic systems in a low voltage distribution system of a housing estate, which has light loads during daytime. The paper presents a case study of a real distribution power system of housing estate in Thailand. Voltage unbalance and energy losses were simulated by using system characteristic and load data from GIS database of PEA with the DIgSILENT Power Factory program. The key findings of our analysis are as follows. Firstly, the number of installable 1-phase rooftop PV systems varies directly with load density. Secondly, the number of installed 1-phase rooftop PV systems can be increased if the installation locations are closer to the transformer. For 3-phase rooftop PV systems, their installations do not have any effects on the voltage unbalance. Furthermore, system energy loss relates to the load density and PV system installation locations in the same way as the voltage unbalance. The key implication of our study is that the installation of 1-phase rooftop PV system should be granted based on a careful consideration of the installation location and the load density.
Correction to: Interpretation and integration of “creating shared value” in Asia: implications for strategy research and practice
Authors: Kim Rebecca Chunghee , Saito Akira , Avvari V. Mohan
Published: September 2020

The article “Interpretation and integration of “creating shared value” in Asia: implications for strategy research and practice”, written by Kim, R.C., Saito, A. & Avvari, V.M. was originally published Online First without Open Access. After publication in volume 19, issue 4, page 379–406 the author decided to opt for Open Choice and to make the article an Open Access publication. Therefore, the copyright of the article has been changed to © The Author(s) 2020 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0.
Understanding regional value chains through the interaction of public and private governance: Insights from Southern Africa’s apparel sector
Authors: Pasquali Giovanni , Godfrey Shane , Nadvi Khalid
Published: September 2020

Regional value chains (RVCs) and South–South trade are increasingly considered key features of 21st-century globalisation. This article investigates how RVCs are shaped by the interaction of private and public governance. It evaluates how this interaction unfolded in Southern Africa’s apparel RVCs, exploring trade, investment and labour regimes across three levels of analysis: national, regional, and global. The paper draws on trade data, secondary literature, and interviews with suppliers and institutions in Eswatini and Lesotho (the largest exporters to the region), and lead firms in South Africa (the largest regional importer). The findings underline the critical role of public governance in shaping retailers’ and suppliers’ participation in RVCs through: (i) regional ‘trade regimes’ protecting regional exporters from global competitors, and recent shifts in global trade regimes; (ii) national and regional ‘investment regimes’ facilitating investment flows from South Africa to Lesotho and Eswatini, and the more recent shift of US-oriented suppliers towards regional markets; and (iii) ‘labour regimes’, including lower wages, less comprehensive labour legislation and weaker trade unions in Lesotho and Eswatini compared to South Africa. The article concludes by considering the policy implications of the interaction of private and public governance for existing and future RVCs in Sub-Saharan Africa.
Explosive electrical wire failures behave differently depending on the voltage applied
Authors: Bandari Anashe
Published: September 2020

High-speed imaging of electrical wire failure reveals regions of fluid instability, bubble growth and rapid change from fluid breakup to phase explosion.
Screening more than 1,500 silicides to determine their thermoelectric properties
Authors: Frank Jodi Ackerman
Published: September 2020

Based on first principles, researchers find compounds with thermoelectric properties that could replace more-toxic materials.
Practicing deep learning in materials science: An evaluation for predicting the formation energies
Authors: Huang Liyuan , Ling Chen
Published: September 2020

Deep learning in recent years has entered the chemistry and materials research arsenal with many successful accomplishments in tasks considered to be intractable using traditional means. However, the widespread application of this data-driven technology is still challenged by the requirement of large training data, poor model interpretability, and hard-to-detect errors that undermine the soundness of conclusion. Here, we performed a systematic study for the modeling of the formation energies of inorganic compounds using deep learning. Our results proved the advantage of deep learning methods over several non-deep learning methods in this specific task and demonstrated the abstraction of knowledge using deep learning, which was a unique ability compared to non-deep learning methods. Several aspects that critically affected the conclusion were also highlighted, including the importance to rigorously compare model performance with the same dataset, the design of input representation, and the careful selection of model architecture. Findings from the current study demonstrate the capabilities of deep learning solving complicated problems in materials research and serve as new guidelines for future practicing of deep learning in this field.
A tabletop setup for ultrafast helicity-dependent and element-specific absorption spectroscopy and scattering in the extreme ultraviolet spectral range
Authors: Yao Kelvin , Willems Felix , von Korff Schmising Clemens , Strüber Christian , Hessing Piet , Pfau Bastian , Schick Daniel , Engel Dieter , Gerlinger Kathinka , Schneider Michael , Eisebitt Stefan
Published: September 2020

Further advances in the field of ultrafast magnetization dynamics require experimental tools to measure the spin and electron dynamics with element-specificity and femtosecond temporal resolution. We present a new laboratory setup for two complementary experiments with light in the extreme ultraviolet (XUV) spectral range. One experiment is designed for polarization-dependent transient spectroscopy, particularly for simultaneous measurements of magnetic circular dichroism (MCD) at the 3p resonances of the 3d transition metals Fe, Co, and Ni. The second instrument is designed for resonant small-angle scattering experiments with monochromatic light allowing us to monitor spin dynamics with spatial information on the nanometer scale. We combine a high harmonic generation (HHG) source with a phase shifter to obtain XUV pulses with variable polarization and a flux of about (3 ± 1) × 1010 photons/s/harmonic at 60 eV at the source. A dedicated reference spectrometer effectively reduces the intensity fluctuations of the HHG spectrum to below 0.12% rms. We demonstrate the capabilities of the setup by capturing the energy- and polarization-dependent absorption of a thin Co film as well as the time-resolved small-angle scattering in a magnetic-domain network of a Co/Pt multilayer. The new laboratory setup allows systematic studies of optically induced spin and electron dynamics with element-specificity, particularly with MCD as the contrast mechanism with femtosecond temporal resolution and an unprecedented signal-to-noise ratio.
Non-commutative birational maps satisfying Zamolodchikov equation, and Desargues lattices
Authors: Doliwa Adam , Kashaev Rinat M.
Published: September 2020

We present new solutions of the functional Zamolodchikov tetrahedron equation in terms of birational maps in totally non-commutative variables. All the maps originate from Desargues lattices, which provide geometric realization of solutions to the non-Abelian Hirota–Miwa system. The first map is derived using the original Hirota’s gauge for the corresponding linear problem, and the second one is derived from its affine (non-homogeneous) description. We also provide an interpretation of the maps within the local Yang–Baxter equation approach. We exploit the decomposition of the second map into two simpler maps, which, as we show, satisfy the pentagonal condition. We also provide geometric meaning of the matching ten-term condition between the pentagonal maps. The generic description of Desargues lattices in homogeneous coordinates allows us to define another solution of the Zamolodchikov equation, but with a functional parameter that should be adjusted in a particular way. Its ultra-local reduction produces a birational quantum map (with two central parameters) with the Zamolodchikov property, which preserves Weyl commutation relations. In the classical limit, our construction gives the corresponding Poisson map, satisfying the Zamolodchikov condition.
Output density quantification of electricity generation by flowing deionized water on graphene
Authors: Kuriya Kei , Ochiai Kotaro , Kalita Golap , Tanemura Masaki , Komiya Atsuki , Kikugawa Gota , Ohara Taku , Yamashita Ichiro , Ohuchi Fumio S. , Meyyappan M. , Samukawa Seiji , Washio Katsuyoshi , Okada Takeru
Published: September 2020

Energy conversion by water flowing over graphene is a promising mode of energy harvesting. However, the mechanism, energy-conversion efficiency, and quantification of power density for this mode of interfacial electricity generation remain unknown. Quantification of the output performance for the flow-induced electricity generation using graphene is presented in this work. The output performance per unit contact area between water and graphene is found to be proportional to the flow speed, with an electromotive force density of 0.0025 [μV/mm2/mm/s] for the conditions used in this work. The ability to quantify output density will help to construct guidelines for future applications of this form of electricity generation.
Reduced bandgap and enhanced p-type electrical conduction in Ag-alloyed Cu2O thin films
Authors: Hu Pengcheng , Du Wenzheng , Wang Mingxu , Wei Haoming , Ouyang Jun , Qian Zhao , Tian Yun
Published: September 2020

The photovoltaic absorber Cu2O has attracted much interest in recent years because it is a nontoxic, earth-abundant, and low-cost p-type semiconductor. To date, Cu2O-based solar cells have achieved a power conversion efficiency of ∼8%. However, this value is still far below its theoretical power conversion efficiency of ∼20%. Further improvement in the photovoltaic properties is believed, at least in part, to be limited by its poor p-type electrical conductivity and its relatively wide bandgap (∼2.17 eV). Herein, we studied the electrical and optical properties of Ag alloyed-Cu2O thin films. We demonstrated that the bandgaps of Cu2O can be decreased by Ag-alloying, which is confirmed by density functional theory calculations indicating that the bandgap reduction is due to the downshift of the conduction band minimum in Cu2O, while the valence band edge of Cu2O remains unchanged. Additionally, we found that p-type carrier concentrations are dramatically enhanced in Ag alloyed-Cu2O thin films. Such interesting behavior may be due to the reduced activation energy for hole transport caused by Ag-alloying. This work suggests that Ag incorporation may be a promising and practical method to improve the photovoltaic performance of high efficiency Cu2O-based solar energy conversion.
Transport coefficients of multicomponent mixtures of noble gases based on ab initio potentials: Diffusion coefficients and thermal diffusion factors
Authors: Sharipov Felix , Benites Victor J.
Published: September 2020

Diffusion coefficients and thermal diffusion factors of binary, ternary, and quaternary mixtures of helium, neon, argon, and krypton at low density are computed for wide ranges of temperatures and molar fractions, applying the Chapman–Enskog method. Two definitions of the diffusion coefficients are discussed, and a general relation between them is obtained. Ab initio interatomic potentials are employed in order to calculate the omega-integrals being part of the expression of the reported quantities. The relative numerical errors of the diffusion coefficients do not exceed the value of 5 × 10−5 being even smaller in some cases. The uncertainties of diffusion coefficients due to the interatomic potential vary between 4 × 10−4 and 6 × 10−3. The numerical error and uncertainty due to the potential of the thermal diffusion factors are estimated as 10−4 and 3 × 10−3, respectively. It is shown that the present results for binary mixtures are more accurate than any other available in the literature, while the results for ternary and quaternary mixtures are reported for the first time.
Documenting COVID-19 screening before surgery during lockdown (COVID Screen): an audit with routinely collected health data
Authors: Story David , Coyle Elizabeth , Devapalasundaram Abarna , Sidiropoulos Sofia , Ou Yang Bobby , Coulson Tim
Published: September 2020

ObjectiveThis study analysed screening for COVID-19 before surgery and outcomes of any perioperative testing for SARS-CoV-2 infection during pandemic-restricted surgery. MethodsAn audit was conducted with routinely collected health data before both elective and non-elective surgery at two large Melbourne hospitals during April and early May 2020. We looked for documented systematic screening for COVID-19 disease and fever (>38°C) and results of SARS-COV-2 testing, and proposed a minimum acceptable documenting rate of 85%. ResultsThe study included 2197 consecutive patients (1279 (58%) undergoing elective surgery, 917 (42%) undergoing non-elective surgery) across most specialities. Although 926 (72%) patients undergoing elective surgery had both systematic screening and temperature documented, approximately half that percentage undergoing non-elective surgery (n=347; 38%) had both documented. However, 871 (95%) of non-elective surgery patients had temperature documented. Acknowledging limited screening, 85 (9.3%) non-elective surgery patients had positive screening, compared with 39 (3.0%) elective surgery patients. All 152 (7%) patients who were tested for SARS-CoV-2 were negative, and no cases were reported from external contact tracing. ConclusionsAlthough ‘not documented’ does not necessarily equal ‘not done’, we found that documenting of COVID-19 screening could be improved. Better understanding of implementing screening practices in pandemics and other crises, particularly for non-elective surgery patients, is warranted. What is known about the topic?Little is known about routine screening for SARS-CoV-2 infection among surgical patients. However, it is well established that implementing effective uptake of safety and quality initiatives can be difficult. What does this paper add?We found that although most patients had documented temperature, fewer than 75% had a documented systematic questionnaire screen for COVID, particularly patients undergoing non-elective surgery. What are the implications for practitioners?Clear documenting is important in managing patients. Pandemics and other crises can require rapid changes in practice. Implementing such measures may be less complete than anticipated and may require greater use of evidence-based implementation strategies, particularly in the less predictable care of non-elective surgery patients.
Riemannian Newton-CG methods for constructing a positive doubly stochastic matrix from spectral data*
Authors: Wang Yang , Zhao Zhi , Bai Zheng-Jian
Published: September 2020

In this paper, we consider the inverse eigenvalue problem for the positive doubly stochastic matrices, which aims to construct a positive doubly stochastic matrix from the prescribed realizable spectral data. By using the real Schur decomposition, the inverse problem is written as a nonlinear matrix equation on a matrix product manifold. We propose monotone and nonmonotone Riemannian inexact Newton-CG methods for solving the nonlinear matrix equation. The global and quadratic convergence of the proposed methods is established under some assumptions. We also provide invariant subspaces of the constructed solution to the inverse problem based on the computed real Schur decomposition. Finally, we report some numerical tests, including an application in digraph, to illustrate the effectiveness of the proposed methods.
Anodization-induced ZrOx/AlOx stacked films for low-temperature, solution-processed indium oxide thin-film transistors
Authors: Li Yuzhi , Lu Kuankuan , Zhang Shengdong
Published: September 2020

In this study, anodization is introduced to induce dehydroxylation and condensation of solution-processed ZrOx films as well as growth of AlOx films. The anodization-induced ZrOx/AlOx stacked films are systematically studied in structure, surface morphology, density, chemical composition, dielectric and electrical properties. X-ray diffraction and atomic force microscopy reveal that anodization-induced ZrOx/AlOx stacked films exhibit amorphous structure and smooth surface roughness (<1 nm). X-ray reflectivity and x-ray photoelectron spectroscopy reveal that the solution-processed ZrOx films exhibit a higher density and a lower content of hydroxyl groups after anodization, suggesting the anodization can induce dehydroxylation and condensation for the ZrOx films. The synergistic effect of collision inducing dissociation and the self-heating from anodization of Al film is proposed to explain the dehydroxylation of the ZrOx films. Dielectric and electrical measurements illustrate that the anodization-induced ZrOx/AlOx stacked films exhibit a lower leakage current, a higher breakdown voltage and a slighter capacitance dispersion on frequency comparing with that of solution-processed ZrOx films without anodization. To verify the possible applications of anodization-induced ZrOx/AlOx stacked films as the gate dielectric in metal-oxide (MO) thin-film transistors (TFTs), they were integrated in low-temperature, directly photopatternable InOx TFTs. Remarkably, with a low process temperature of 200 °C, the InOx TFTs based on the optimized ZrOx/AlOx dielectrics exhibit an average mobility of 8.94 cm2 V−1 s−1, an I
on/I
off of large than 105 and negligible hysteresis in transfer curves. These results demonstrate the potential application of anodization-induced solution-processed MO dielectric films for low-temperature TFTs.
Controllable liquid water sensitivity of polymer-encapsulated oxide thin-film transistors
Authors: Yu Kyeong Min , Kim Sung-Hun , Park Ji-Won , Sim Eun-Seon , Boampong Amos Amoako , Kim Min-Hoi
Published: September 2020

We demonstrated the controllable liquid water sensitivity of polymer-encapsulated oxide-based thin-film transistors (OxTFTs). The oxide active channels of the fabricated TFTs were utilized as water-sensitive layers. The OxTFTs were encapsulated with several polymers as water controlling layers (WCLs) to investigate and optimize the water sensitivity. It was found that the surface energy and porosity of the WCL significantly affect the water-dependent electrical characteristics of the OxTFTs. By employing poly(vinylidene-trifluoroethylene) (P(VDF-TrFE)) as a WCL and annealing the chosen polymer properly, we achieved a continuous shift of the threshold voltage even after several hours of direct exposure to the liquid phase of water which is crucial for sensor properties of the OxTFTs. The device using P(VDF-TrFE) as the WCL exhibits long-term stable detection characteristics and repeatability, demonstrating its applicability as a low-cost soil moisture sensor.
Combined effect of nanorod and stacking fault for improving nanorod interface in YBa2Cu3O7−δ nanocomposite films
Authors: Horide Tomoya , Ishimaru Manabu , Sato Kazuhisa , Matsumoto Kaname
Published: September 2020

Self-organized nanorods in YBa2Cu3O7−δ films are important pinning centers from the technical and fundamental views. While influence of nanoscale factors (>4–5 nm) on the vortex pinning has already been discussed in detail, the interface control of nanorods (at the smaller scale) has not yet been performed. Here, it is demonstrated that the stacking faults can control the nanorod interface to improve the vortex pinning. The stacking faults were formed across the nanorods by post-annealing the YBa2Cu3O7−δ films containing BaMO3 (M = Zr, Sn, Hf) nanorods. The strong bonding between YBa2Cu3O7−δ and BaMO3 varies the atomic position of YBa2Cu3O7−δ, degrading an interface sharpness and an elementary pinning force of the nanorod. Scanning transmission electron microscopy and density functional theory calculation clarified that the stacking faults broke the strong bonding between YBa2Cu3O7−δ and BaMO3 at the nanorod interface, and reduced the local strain around the nanorods, improving the elementary pinning force. As a result, the critical current density was improved in low temperature and low magnetic field when magnetic field was aligned with the c-axis. Thus, the combined effect of nanoinclusions and crystalline defects, in the present case, nanorods and stacking faults, can control the interface of nanoinclusion pinning centers, opening the interface design to realize the ideal pinning situation.
Mathematical computations for Peristaltic flow of heated non-Newtonian fluid inside a sinusoidal elliptic duct
Authors: Saleem Anber , Akhtar Salman , Nadeem Sohail , Alharbi Fahad M , Ghalambaz Mehdi , Issakhov Alibek
Published: September 2020

This research work interprets the mathematical study of peristaltic flow of non-Newtonian fluid across an elliptical duct. The heat transfer mechanism for this elliptical duct problem is also considered in detail. The mathematical equations for Casson fluid model are developed and then by using appropriate transformations and long wavelength approximation, this mathematical problem is converted into its dimensionless form. After converting the problem in dimensionless form, we have obtained partial differential equations for both velocity and temperature profiles. These partial differential equations are solved subject to given boundary conditions over elliptical cross sections and exact mathematical solutions are obtained. The results are further discussed by plotting graphical results for velocity, pressure gradient, temperature, pressure rise and streamlines.
The state-of-the-art on Refrigerants
Authors: Cavallini A
Published: September 2020

The two recent global emergencies (stratospheric ozone depletion and global warming) force refrigerating engineers and operators to face a new revolution on the choice of the working fluids for the different applications of refrigeration technology. Chemistry by now runs short of new synthetic products meeting within acceptable limits all the requirements asked for by the different refrigeration applications, and compromise solutions are more and more necessary, involving a limited use of few old-generation fluids, the new family of products HFO and an increased consideration for natural refrigerants. While dealing with these topics, this paper will show how basic thermodynamics can highlight important characteristics of a refrigerant.
Experimental study of a phase change material storage for low-temperature applications
Authors: Besagni G , Croci L
Published: September 2020

Thermal energy storage technologies are matter of intense research and discussion, in the broader framework of decoupling the “demand-side” and the “supply-side”. This topic is of paramount importance to support the large-scale deployment of renewable energy-based technologies in the residential sector, to support the decarbonisation pathways. In this perspective, a promising solution concerns solar-assisted heat pumps. This paper contributes to the existing discussion by developing, building and testing a “pilot-scale” finned-and-tube phase change material storage for solar-assisted heat pumps applications (viz.,low temperature applications, in the range of 20 - 30 °C). The proposed storage unit is tested, under real boundary conditions and it is able to store 65 % higher thermal energy stored compared with an equivalent water storage unit.
Two-Phase Heat Transfer in 4.0 mm Tube Under Different Gravity Conditions
Authors: Lancione Giorgia , Mieko Iceri Daiane , Gugliermetti Luca , Saraceno Luca , Zummo Giuseppe , Bisegna Fabio , Nardecchia Fabio
Published: September 2020

This study aimed to analyze the two-phase heat transfer in a vertical upward flow configuration under different gravity conditions. The facility is a new version of MicroBo (Microgravity Boiling), the working fluid used is perfluorohexane C6F14 and a 4.0 mm aluminum channel is arranged vertically to perform ebullition process. The platform used to get data in microgravity was the parabolic flight, which represents one of the most widely used platforms despite the period of time available to collect data is very short. The analysis of the results has been carried out following two main approaches: the first, ground-flight data comparison, for the study of variable gravity data collected during the 67th ESA campaign of parabolic flight held in November 2017, while the second, ground data analysis, to analyze the data collected on the ground in the ENEA laboratory with the same facility in December 2018. In particular ground – flight data have been analyzed comparing boiling curves at different flow rates, from a minimum of 5.3 l/h up to 17 l/h, in micro, hyper and normal gravity. The operating inlet pressure during experiments has been fixed at 1.6 bar with a heat flux range of 5.4 - 85.6 kW/m2. For what regard ground data boiling curves, with a flow rate of 10 l/h, are shown with a direct flow pattern visualization. The operating pressure has been fixed at 1.3 bar and 1.8 bar with a heat flux range of 2.5 – 94.6 kW/m2. For the latter analysis, it also has been carried out a qualitative study for the validation of the void fraction model, starting from the visualization of the images of flow patterns recorded during the acquisitions.
Experimental analysis of drop-size density distribution during dropwise condensation of steam
Authors: Mirafiori M , Parin R , Bortolin S , Del Col D
Published: September 2020

Dropwise condensation (DWC) has attracted research interest since its first description in 1930 due to the high heat transfer coefficients that can be obtained by promoting this mechanism as compared to the case of filmwise condensation. The modelling of dropwise condensation heat transfer is complex since it must account for droplets nucleation, growth and removal: researchers proposed different methods and the first semi-empirical model was presented in 1966 by Le Fevre and Rose. Their model predicts the total heat transfer across a surface during DWC by estimating the drop-size density distribution and the heat transfer through a single droplet. The goal of the present work is to investigate the large drop-size density distribution during dropwise condensation considering different operating conditions (heat flux and surface coating). In this work, a new illumination system (torus-shaped LED) has been designed and built to allow droplets detection with diameters from millimetres down to few microns. The torus-shaped LED is used as light source for a high-speed camera coupled with microscope lens. The recorded images have been analysed by a homemade software in MATLAB® code, and the measured droplet population has been compared with the theoretical formula proposed by Le Fevre and Rose [1]. More than six million droplets have been detected and an excellent agreement with the Le Fevre and Rose theory has been found.
Water Pool boiling on Aluminum Metal Foams
Authors: Righetti G. , Calati M. , Doretti L. , Hooman K. , Mancin S.
Published: September 2020

With current growth in electronic systems, their physical sizes decrease, and the spacing between components decreases, both the total amount of heat generated and the power density increase significantly. There is a general agreement in the scientific community that current air-cooling technologies are asymptotically approaching their intrinsic limits. Pool boiling is widely used in many different engineering systems, but most of these applications have a common limitation: the maximum heat flux that can be rejected by the cooling systems under safe, reliable, and efficient operation. In this paper experimental data pertinent to deionized water pool boiling across 10 mm thick aluminum foams are presented. Three foam samples with different pore densities, 5, 10, and 40 PPI, yet with an identical mean porosity of 0.92 are tested. Compared to a heated flat plate, the foams offer higher heat transfer area albeit at induced bubble escaping resistance. The tradeoff between these two effects is investigated. Through the use of high speed video camera recording, bubble generation, trajectory and growth rate were analyzed and critically discussed.
Natural convection in a vertical channel with open-cell foams
Authors: Andreozzi A , Bianco N , Iasiello M , Naso V
Published: September 2020

Open-cell foams are promising to enhance heat transfer in many applications, such as electronics cooling. Though heat transfer coefficients are low, natural convection in open-cell foams is used in low-end applications, as consumer electronics or switching devices. In this paper air natural convection in a vertical channel equipped with an open-cell foam, with a symmetric uniform heat flux boundary condition at the vertical sides, is investigated numerically. The foam is modeled as a continuous porous medium under the assumption of Local Thermal Non-Equilibrium (LTNE) between solid and fluid phases. Mass, momentum and energy equations are solved numerically under the appropriate boundary conditions by employing a commercial finite element code. The velocity of the fluid and the temperature of the solid as well as the global heat transfer coefficient, for different thermo-physical properties and morphologies of the foam, and for various channel aspect ratios, are predicted.
Numerical investigation on thermoelectric generators in an exhaust automotive line with aluminium foam
Authors: Buonomo B , di Pasqua A , Manca O , Nardini S
Published: September 2020

In the present paper a two-dimensional convective heat transfer problem in a partially filled channel with metal foam is numerically solved in steady state regime. An external thermoelectric generators (TEG) component is placed on the top surface of the channel. The numerical analyses are accomplished assuming the local thermal equilibrium (LTE) model to simulate the presence of the aluminum foam. The working fluid is exhaust gas with properties equal to the air for fixed temperature of the upper surface of the thermo-electric generator (TEG). The thermophysical properties are assumed temperature independent and the TEG component is considered as a solid with an internal energy generation. The Ansys-Fluent code is applied in order to resolve the governing equations for gas, porous media and TEG. Several mass flow rates of exhaust gas on the inlet section of the channel are considered. Different thicknesses of aluminum foam are assumed into the duct. The foam is characterized by different porosity equal to 0.90, 0.95, 0.97. Moreover, the number of pores per inch also changes and assumes the following values of 5, 20, 40. Results are showed in terms of temperature distributions, pressure drop, thermoelectric efficiency for different exhaust gas flow rates and metal foam characteristics and thicknesses. The results highlight that the use of metal foams significantly increases the heat transfer between the surface of exhaust gas tube and hot gas. Consequently, the effectiveness improves, and it increases between three-ten times with respect to the one for tube without metal foams. It is shown that the pore density does not affect the effectiveness.
Onset of thermal convection in a horizontal porous layer saturated by a power–law fluid
Authors: Celli Michele , Natale Impiombato Andrea , Barletta Antonio
Published: September 2020

A horizontal porous layer saturated by a non–Newtonian fluid is taken into account. The fluid is a Ostwald–De Waele type of fluid. The layer is heated from below while the upper boundary is isothermal. The lower boundary is impermeable and the upper one is free. A fully developed basic throughflow is considered. The basic state is perturbed by employing small amplitude perturbations such that a linear stability analysis is performed. The disturbances are assumed to be normal modes and a system of ordinary differential equations governing the perturbation dynamics is obtained. These ODEs form an eigenvalue problem that is solved numerically: both the neutral stability curves and the threshold values for the onset of convection are presented.