bluuebunny/crossref_metadata_2025 huggingface dataset:
Remote epitaxy of GaN via graphene on GaN/sapphire templates
Authors: Badokas Kazimieras , Kadys Arūnas , Mickevičius Jūras , Ignatjev Ilja , Skapas Martynas , Stanionytė Sandra , Radiunas Edvinas , Juška Giedrius , Malinauskas Tadas
Published: February 2021

Remote epitaxy via graphene has recently attracted significant attention, since it provides the possibility to lift-off the grown epitaxial layer, reuse the substrate, and produce flexible devices. However, extensive research is still necessary to fully understand the III-nitride formation on the van der Waals surface of a two-dimensional material and utilize remote epitaxy to its full potential. In this work, the growth of a GaN epilayer using a GaN/sapphire template covered with monolayer graphene is presented. Metalorganic vapor phase epitaxy is chosen to fabricate both the template and the nitride epilayer on top as a cost-effective approach toward GaN homoepitaxy. One-step and multi-step growth temperature protocols are demonstrated while paying particular attention to the graphene interface. GaN seed formation on graphene is analyzed to identify remote epitaxy. Crystalline quality improvement of the epilayer by adjusting the growth parameters is further discussed to provide useful insights into GaN growth on a GaN/sapphire template via monolayer graphene.
High performance perovskite LEDs via SPR and enhanced hole injection by incorporated MoS2
Authors: Sun Dongwei , Zhang Ke , Mei Sijiong , Xu Jinxia , Jiang Yan , Xiao Xiangheng , Zhou Yuanming , Mei Fei
Published: February 2021

Organic–inorganic hybrid perovskites have attracted widespread attention in relation to light-emitting diodes (LEDs) due to their excellent properties. However, the imperfect energy band alignment between the perovskite and poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) limits the device’s performance. Here, we have investigated the effect of blending MoS2 in PEDOT:PSS and the resulting performance of perovskite LEDs (PeLEDs). We found that the doping of MoS2 can optimize the energy barrier and promote hole injection, significantly improving the current efficiency (CE) of PeLEDs, which can be attributed to the distinguished electrical conductivity and improved charge injection balance. At the same time, the local surface plasmon resonance effect with Au nanoparticles (NPs) is also introduced to reduce the nonradiative recombination and effectively promote light emission to further improve the performance of PeLED devices. Compared to the control PeLEDs device with undoped PEDOT:PSS as the hole transport layer, a 223% enhancement in maximum CE and a 130% enhancement in maximum luminance are achieved, with an optimal volume ratio for the PEDOT:PSS:MoS2 of 1:0.4 and Au NPs of 10%. Thus, the optimization combination of MoS2 and Au NPs is an excellent approach to improve the performance of PeLEDs, thereby increasing the potential applications of PeLED devices.
High-pressure monoclinic–monoclinic transition in fergusonite-type HoNbO4
Authors: Garg A B , Errandonea D , Rodríguez-Hernández P , Muñoz A
Published: February 2021

In this paper we perform a high-pressure (HP) study of fergusonite-type HoNbO4. Powder x-ray diffraction experiments and ab initio density-functional theory (DFT) simulations provide evidence of a phase transition at 18.9(1.1) GPa from the monoclinic fergusonite-type structure (space group I2/a) to another monoclinic polymorph described by space group P21/c. The phase transition is reversible and the HP structural behavior is different than the one previously observed in related niobates. The HP phase remains stable up to 29 GPa. The observed transition involves a change in the Nb coordination number from 4 to 6, and it is driven by mechanical instabilities. We have determined the pressure dependence of unit-cell parameters of both phases and calculated their room-temperature equation of state. For the fergusonite-phase we have also obtained the isothermal compressibility tensor. In addition to the HP studies, we report ambient-pressure Raman and infrared (IR) spectroscopy measurements. We have been able to identify all the active modes of fergusonite-type HoNbO4, which have been assigned based upon DFT calculations. These simulations also provide the elastic constants of the different structures and the pressure dependence of the Raman and IR modes of the two phases of HoNbO4. According to ab initio calculations, the reported phase transition is related to a mechanical instability and a phonon softening.
Emergence of magnetic anisotropy by surface adsorption of transition metal dimers on γ-graphyne framework
Authors: Jana Susmita , Chowdhury Suman , Jana Debnarayan , Chakrabarti Aparna , Banerjee Arup
Published: February 2021

In this paper a systematic study is carried out to demonstrate the structural stability and magnetic novelty of adsorbing transition metal (TM) dimers (A-B) on graphyne (GY) surface, GY@A-B. Our research points out that the dimers are strongly adsorbed onto GY due to their large natural pores and the electron affinity of the sp-hybridized carbon atoms. Electronic properties of these dimer-graphyne composite systems are of particular importance as they behave as degenerate semiconductors with partial occupation of states at E
F. Furthermore, their remarkable spin polarization (>80%) at Fermi energy (E
F) can be of paramount importance in spintronics applications. Most of the GY@A-B structures exhibit large magnetic anisotropies as well as magnetic moments along the out-of-plane direction with respect to the GY surface. Particularly, GY@Co–Ir, GY@Ir–Ir and GY@Ir–Os structures possess positive magnetic anisotropic energies (MAE) of 121 meV, 81 meV and 137 meV, respectively, which are comparable to other well-known TM dimer doped systems. The emergence of high MAE can be understood using the second-order perturbation theory on the basis of the strong spin–orbit coupling (SOC) between the two TMs and the degeneracy of their d-orbitals near E
F. A close correspondence between the simulated and the analytical results has been established through our work. Further, a simple estimation shows that, GY@A-B structures have the potential to store data up to 64 PB m−2. These intriguing electronic characteristics along with magnetism suggest GY@A-B to be a promising material for future magnetic storage devices.
Foundations of measurement of electrons, ions and species fluxes toward surfaces in low-temperature plasmas
Authors: Benedikt Jan , Kersten Holger , Piel Alexander
Published: February 2021

This foundation article discusses the diagnostics of electrons and ions in plasmas and fluxes of charged and neutral species toward plasma-facing surfaces by non-optical methods. The focus is laid on the fundamentals of the most common methods and their application to non-equilibrium low-pressure electropositive plasmas and ion beams. The key topics are Langmuir probes (LPs), Faraday cups (FCs) and energy analyzers, mass spectrometry, as well as novel calorimetric and force probes (FPs). For each method, the concepts are introduced, hints at best practice are given, and a survey of the recently published literature is included. Starting with the sheath–plasma boundary, the principles of plane and cylindrical LPs and the measurement of electron temperature and density are discussed. Beyond standard textbooks, double, triple and emissive probes are described and modulation techniques for obtaining the electron energy distribution function are presented. More technical issues related to probe compensation in radio-frequency plasmas, probe contamination, and the influence of a magnetic field are also included. The presentation is completed by modern radio-frequency techniques, such as impedance probes, multipole resonance probes, and self-excited electron resonance spectroscopy. FCs, retarding field analyzers (RFAs) as well as novel calorimetric and FPs are useful tools for the measurement of overall, not species resolved, ions and neutral species fluxes toward surfaces. RFAs provide overall ion energy distribution functions, whereas calorimetric and FPs can deliver information about fluxes of fast neutrals. The issues related to secondary electron emission, absolute signal calibration, and analysis of plasmas with complex chemistry are discussed. Mass spectrometry diagnostics is capable of mass and energy-resolved detection of ions and neutral species at the plasma-facing surfaces. Detection, identification and absolute density calibration of neutral stable and radical species are treated in detail and peculiarities of ion mass spectrometry, such as detection of negative ions, ion measurements in front of powered electrodes, or chromatic aberration and acceptance angle limitations in energy spectrum measurements are introduced.
Remote streamer initiation on dielectric surface
Authors: Kusýn L , Synek P , Becker M M , Hoder T
Published: February 2021

We study the origin of filamentary patterns in a sinusoidally driven surface barrier discharge at high over-voltage in atmospheric pressure air. Using a time-correlated single-photon counting based optical emission spectroscopy, we reveal ultrafast processes within generated discharges in both polarities of the applied voltage. For negative polarity, we observe initiation of complex streamer cascade which emerges far from the bare cathode. This event is responsible for long filamentary structure detected by an intensified CCD camera and transfers an exceptionally large electrical charge. It constitutes another, previously unknown, mechanism contributing to the charge-transfer equilibrium in studied periodical discharge. The revealed process leads to the formation of an intense cathode spot, a critical condition for plasma-transition into a highly ionised state.
Formulation of UV curable nano-silver conductive ink for direct screen-printing on common fabric substrates for wearable electronic applications
Authors: Hong Hong , Jiang Lihong , Tu Huating , Hu Jiyong , Yan Xiong
Published: February 2021

One-step printing of electrically conductive inks on textiles is one of the simplest and most prospective methods to manufacture functional wearable electronics. However, the high surface roughness and porous structure as well as poor temperature endurance of most textiles have become the major challenges for the realization of printed electronic textiles (E-textiles). To solve these issues, the UV curable conductive ink with fast curing and low temperature characteristics was formulated to fabricate the flexible fabric-based conductive patterns using screen printing method. The specific focus was spent on investigating the effect of ink composition on curing speed, film forming ability, morphological characteristics and electrical properties of conductive patterns directly printed on fabric substrates. Firstly, we determined the necessity of defoamer for the formation of uniform and continuous printed textile-based patterns, and optimized the film forming ability of UV-curing ink by exploring the defoamer performance. Then, the ink curing speed was found heavily depending on the different types and contents of photoinitiators. Finally, the nano-silver loading showed critical influence to the screen-printability and the electrical properties of printed patterns. An ink formulation with 60 wt% nano-silver, 4 wt% photoinitiator (1173), and 0.2 wt% defoamer (BYK-555) showed satisfactory screen printability, and the conductive patterns with 1.0 mm width exhibited a remarkably low resistivity of 4.04 × 10−5 Ω cm. Moreover, the high performance of the conductive pattern screen-printed on four different fabrics by the formulated UV curable conductive ink further demonstrated its application potential. The results showed that uniformity and electrical properties of printed patterns were directly
related to the weaving method, texture characteristic, and roughness of the
textiles. We believe these results will provide basic guidance for the formulation design of conductive ink and facilitate the utility of textiles-based wearable electronics.
Electromagnetic properties of curved HTS trapped field stacks under high-frequency cross fields for high-speed rotating machines
Authors: Zhang Hongye , Mueller Markus
Published: February 2021

Superconducting electric propulsion systems, characterized by high power densities and efficiencies, provide a possibility to zero carbon emission for future aviation. Stacks of high temperature superconducting (HTS) coated conductors (CCs) have become an alternative for high field magnets applied to superconducting machines, given their excellent field trapping ability and thermal stability. High-frequency ripple fields always exist in high-speed electric machines. Most research work regarding HTS trapped field stacks (TFSs) was focused on their magnetization methods and amplitude of trapped flux density; however, their performance in the high-frequency environment remains unclear. Despite several numerical models established for flat HTS TFSs, a comprehensive analysis of curved ones is still lacking, which possess geometrical applicability for cylindrical rotating shafts. Aimed at exploring the electromagnetic properties of curved HTS TFSs applied to high-speed rotating machines, a 3D numerical model considering both the multilayer structure and the Jc
(B) dependence of HTS CCs has been built. Current and magnetic flux density distributions, as well as loss properties of a curved HTS TFS have been studied in detail, under perpendicular and cross fields with varying frequencies ranging from 50 Hz to 20 kHz. Results have shown that, the widely adopted two-dimensional-axisymmetric models are inapplicable to study the electromagnetic distributions of TFSs because of the emergence of the electromagnetic criss-cross defined in this paper. High-frequency ripple fields can drive induced current towards the periphery of the HTS TFS due to the skin effect, leading to a fast rise of AC loss and even an irreversible demagnetization of the stack. This paper has qualified and quantified the high-frequency electromagnetic behaviours of curved HTS TFSs, providing a useful reference for their loss controlling and anti-demagnetization design in high-speed propulsion machines.
Superconducting properties of the non-centrosymmetric superconductors TaXSi (X = Re, Ru)
Authors: P Sajilesh K , Singh R P
Published: February 2021

Ternary noncentrosymmetric superconductors TaXSi (X = Re, Ru) investigated by magnetization, resistivity, and specific heat measurements. It crystallize in the orthorhombic TiFeSi-type structure with superconducting transition

T

c

= 5.32 K and 3.91 K for TaReSi and TaRuSi, respectively. A low value of specific heat jump and the upper critical field concave nature suggests a nontrivial superconducting gap.
Zero-energy modes of two-component Bose–Bose droplets
Authors: Zin Paweł , Pylak Maciej , Gajda Mariusz
Published: February 2021

Bose–Bose droplets are self-bound objects emerging from a mixture of two interacting Bose–Einstein condensates when their interactions are appropriately tuned. During droplet formation three continuous symmetries of the system’s Hamiltonian are broken: translational symmetry and two U(1) symmetries, allowing for arbitrary choice of phases of the mean-field wavefunctions describing the two components. Breaking of these symmetries must be accompanied by appearance of zero-energy excitations in the energy spectrum of the system recovering the broken symmetries. Normal modes corresponding to these excitations are the zero-energy modes. Here we find analytic expressions for these modes and introduce Hamiltonians generating their time evolution—dynamics of the droplet’s centers of mass as well as dynamics of the phases of the two droplet’s wavefunctions. When internal types of excitations (quasiparticles) are neglected then the very complex system of a quantum droplet is described using only a few ‘global’ degrees of freedom—the position of the center of mass of the droplet and two phases of two wave-functions, all these being quantum operators. We believe that our work might be useful in describing in a relatively easy way the low energy collisions of quantum droplets in situations where coherent flow of atoms between the droplets takes place.
Dynamic community discovery via common subspace projection
Authors: Yu Lanlan , Li Ping , Zhang Jie , Kurths Jürgen
Published: February 2021

Detecting communities of highly internal and low external interactions in dynamically evolving networks has become increasingly important owing to its wide applications in divers fields. Conventional solutions based on static community detection approaches treat each snapshot of dynamic networks independently, which may fragment communities in time (Aynaud T and Guillaume J L 2010 8th Int. Symp. on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (IEEE) pp 513–9), resulting in the problem of instability. In this work, we develop a novel dynamic community detection algorithm by leveraging the encoding–decoding scheme present in a succinct network representation method to reconstruct each snapshot via a common low-dimensional subspace, which can remove non-significant links and highlight the community structures, resulting in the mitigation of community instability to a large degree. We conduct experiments on simulated data and real social networking data with ground truths (GT) and compare the proposed method with several baselines. Our method is shown to be more stable without missing communities and more effective than the baselines with competitive performance. The distribution of community size in our method is more in line with the real distribution than those of the baselines at the same time.
Difference synchronization in nonidentical discrete-time chaotic systems with different dimensions using three scaling matrices
Authors: Feng Cun-Fang , Yang Hai-Jun , Zhou Cai
Published: February 2021

In this paper, we consider the difference synchronization for different chaotic maps with different dimensions using three scaling matrices. The proposed method allows us to study difference synchronization of two master discrete-time chaotic systems with dimension

n

and one response discrete-time chaotic system with dimension

m
.

Based on the Lyapunov stability theory and stability property of linear discrete-time systems, controllers are derived to achieve the difference synchronization among three nonidentical discrete-time chaotic systems with different dimensions in two cases:

n
<
m

and

n
>
m
.

For the case

n
<
m
,

2D Fold map and 2D Hénon map are used as the master systems, and the 3D Hitzl-Zele map is chosen as the slave system to simulate the difference synchronization. For the case

n
>
m
,

3D Stefanski map and 3D Baier-Klein map are adopted as the master systems, and 2D Lorenz discrete-time chaotic system is used as the slave system during the simulation. The numerical simulations illustrate the effectiveness and feasibility of the proposed method.
A new approach for modelling the damped Helmholtz oscillator: applications to plasma physics and electronic circuits
Authors: El-Tantawy S A , Salas Alvaro H , Alharthi M R
Published: February 2021

In this paper, a new approach is devoted to find novel analytical and approximate solutions to the damped quadratic nonlinear Helmholtz equation (HE) in terms of the Weiersrtrass elliptic function. The exact solution for undamped HE (integrable case) and approximate/semi-analytical solution to the damped HE (non-integrable case) are given for any arbitrary initial conditions. As a special case, the necessary and sufficient condition for the integrability of the damped HE using an elementary approach is reported. In general, a new ansatz is suggested to find a semi-analytical solution to the non-integrable case in the form of Weierstrass elliptic function. In addition, the relation between the Weierstrass and Jacobian elliptic functions solutions to the integrable case will be derived in details. Also, we will make a comparison between the semi-analytical solution and the approximate numerical solutions via using Runge–Kutta fourth-order method, finite difference method, and homotopy perturbation method for the first-two approximations. Furthermore, the maximum distance errors between the approximate/semi-analytical solution and the approximate numerical solutions will be estimated. As real applications, the obtained solutions will be devoted to describe the characteristics behavior of the oscillations in RLC series circuits and in various plasma models such as electronegative complex plasma model.
A pedagogical review on solvable irrelevant deformations of 2D quantum field theory
Authors: Jiang Yunfeng
Published: February 2021

This is a pedagogical review on

T

T

¯

deformation of two dimensional quantum field theories. It is based on three lectures which the author gave at ITP-CAS in December 2018. This review consists of four parts. The first part is a general introduction to

T

T

¯

deformation. Special emphasises are put on the deformed classical Lagrangian and the exact solvability of the spectrum. The second part focuses on the torus partition sum of the

T

T

¯

/

J

T

¯

deformed conformal field theories and modular invariance/covariance. In the third part, different perspectives of

T

T

¯

deformation are presented, including its relation to random geometry, 2D topological gravity and holography. We summarize more recent developments until January 2021 in the last part.
Possibility of robust detrended fluctuation analysis as a method for identifying fractal properties of geomagnetic time series
Authors: Rifqi F N , Hamid N S A , Yoshikawa A
Published: February 2021

Geomagnetic data has been demonstrated to exhibit fractal properties, which are analysed using various fractal methods. These methods allow the characterization of geomagnetic activity during certain periods using the Hurst exponent. In this study, the geomagnetic activity during the quiet period of the month of December 2011 is analysed using the r-DFA method, of which viability to identify fractal properties of geomagnetic data has not been tested yet, and also using its established predecessor; the detrended fluctuation analysis (DFA). The results show that the r-DFA method is indeed viable to be used upon geomagnetic time series, with comparable if not better performance compared to its predecessor.
An Overview of Log Periodic Dipole Antenna (LPDA) UiTM Site and the Progress Status
Authors: Norsham N A M , Hamidi Z S , Shariff N N M , Husien N , Zainol N H , Sabri S N U
Published: February 2021

The main objective of this paper is focused on the overview of log periodic dipole antenna that was constructed and placed at UiTM and the data obtained from the antenna. The LPDA antenna was combined with the CALLISTO spectrometer where this is a program under the International Space Weather Initiative to support new country to be a part of solar astrophysics group. Until now, there are many locations around the world that grab this opportunity to contribute the data from their country so that all people can be benefited from it. The function of the antenna and CALLISTO system is more to monitor the Sun for 24 hours per day. The monitoring of the Sun is important as the activities from it such as solar flares and Coronal Mass Ejections (CMEs) could harm and disturb the technologies such as GPS and satellites. UiTM take this chance to build the log periodic dipole antenna and the data recorded was presented in this paper. The future improvement of the antenna was discussed to obtain the best performance in gaining the data.
Design of Space-based IoT System on Multiple Access Communication for Nanosatellite Applications
Authors: Rahim S N M , Zaki S B M , Jusoh M H
Published: February 2021

This work is related to the Store and Forward (S&F) technology demonstration mission of UiTMSAT-1 (UiTM’s first nanosatellite). The work aims to develop an array of Ground Sensor Terminal (GST) units to communicate with a single nanosatellite with the S&F application. The terminal unit will uplink Earth based sensor’s data to nanosatellite, hence requires specific equipment to ensure a successful data transmission. A synchronization method based on Time Division Multiple Access (TDMA) is utilised for synchronizing three GST units. The work’s methodology focus is on the situation when all the GST units are within the same nanosatellite’s footprint. In this paper, the design of the system is simulated with different scripted codes and the result is analysed. This work will help to introduce a potential technique for data transfer synchronization between terminals for S&F application of space-based IoT.
Increasing maize yields in Northeast China are more closely associated with changes in crop timing than with climate warming
Authors: Zhang Yi , Zhao Yanxia , Sun Qing
Published: February 2021

An understanding of mechanisms that underlie the steady increase in crop yields over recent decades is important for promotion of future sustainable yield gains and maintenance of future food security. In this study, we coupled observational maize yield and climate variables based on crop development data from 1981 to 2009 to construct an empirical model that can resolve the separate and combined effects of climate and agricultural practices related to crop timing on maize yield in Northeast China (NEC), the largest spring maize-producing region of China. Climate warming contributed to approximately 15.6% of the trend for increasing yield over the 29 year period. The beneficial effects of climate warming on yield were due to increases in accumulation of temperatures between 10 °C and 30 °C (growing degree days, GDD), which positively contributed to 29.7% of yield and offset the −14.1% yield reduction caused by a trend involving increasing accumulation of temperatures above 30 °C (or extreme degree days, EDD). Adaptive improvements in crop timing practices (e.g. shifts in planting date and selection of later-maturity cultivars) further optimized the impacts of GDD and EDD during the entire growing season by exploiting more GDD during the reproductive phase and fewer EDD during the vegetative phase, thereby contributing to a yield gain of 25.4% over the period from 1981 to 2009. Taken together, climate warming and crop timing practices contributed to 39.4% of the maize yield increase since 1981. Yield losses due to climate warming were detected at only one site located in the southern part of the NEC region, where yield losses must be offset by positive effects of crop timing changes. The trends in maize yields presented here may provide guidance for effective adaptation options for maize production under conditions of continued climate warming.
Association between county-level coal-fired power plant pollution and racial disparities in preterm births from 2000 to 2018
Authors: Daouda Misbath , Henneman Lucas , Kioumourtzoglou Marianthi-Anna , Gemmill Alison , Zigler Corwin , Casey Joan A
Published: February 2021

Coal has historically been a primary energy source in the United States (U.S.). The byproducts of coal combustion, such as fine particulate matter (PM2.5), have increasingly been associated with adverse birth outcomes. The goal of this study was to leverage the current progressive transition away from coal in the U.S. to assess whether coal PM2.5 is associated with preterm birth (PTB) rates and whether this association differs by maternal Black/White race/ethnicity. Using a novel dispersion modeling approach, we estimated PM2.5 pollution from coal-fired power plants nationwide at the county-level during the study period (2000–2018). We also obtained county-level PTB rates for non-Hispanic White and non-Hispanic Black mothers. We used a generalized additive mixed model to estimate the relationship between coal PM2.5 and PTB rates, overall and stratified by maternal race. We included a natural spline to allow for non-linearity in the concentration–response curve. We observed a positive non-linear relationship between coal PM2.5 and PTB rate, which plateaued at higher levels of pollution. We also observed differential associations by maternal race; the association was stronger for White women, especially at higher levels of coal PM2.5 (>2.0 μg m−3). Our findings suggest that the transition away from coal may reduce PTB rates in the U.S.
Utilization of Bamboo Fiber towards sustainable asphalt mixture
Authors: Masri K A , Nur Fatin N Y , Chin S C , Nur Syafiqah S M Z , Shaffie E
Published: February 2021

Stone Mastic Asphalt (SMA) is a gap-graded asphalt mixture that depends on the stone-to-stone contact to provide its load-carrying capacity against rutting and stripping. Even though SMA has good performance, especially in resisting permanent deformation, it suffers from excessive binder drain down due to high bitumen content. Thus, the aim of this study is intended to utilize bamboo fiber to control the drainage and bleeding problem. In this study, bamboo fiber is chosen as a modified binder to enhance the performance of stone mastic (SMA 20) due to more economical than other conventional fibers. The aim of this study to evaluate the mechanical performance of bamboo fiber stone mastic asphalt (SMA) in terms of Marshall stability, resilient modulus, dynamic creep, and Cantabro Loss. Twelve samples of SMA 20 mix with PEN 60/70 binders are tested for each test. Bamboo fiber in the range of 0%, 0.2%, 0.3%, 0.4%, 0.5% and 0.6% of on the aggregate weight used in the original mix design. From the results, it shows that the addition of 0.4% fiber contributes to the lowest value of abrasion and dynamic creep and 0.4% producing the highest value for resilient modulus, stability, density, and stiffness. Based on that,0.4 % is the optimum fiber content that could be used to design. Thus, it can be concluded that the existence of fiber is capable of enhancing the performance of SMA 20.
Assessment of Performance Wonogiri Dam in Service of Water Needs Due to The Impact of Erosion and Sedimentation
Authors: Ari Murdhianti A , Sri Wahyu Kusumastuti B , Lily Montarcih C , Pitojo Tri Juwono D , Sisinggih Dian E
Published: February 2021

Wonogiri Dam administratively located in Wonogiri Regency exactly in the upper reaches of Bengawan Solo Watershed. Wonogiri Dam is a multipurpose dam which is used as irrigation, raw water, hydroelectric power plant and flood control. The high impact of erosion and sedimentation became main issue in Wonogiri Dam caused by changes in land use at upstream area. Within 25 years the capacity of Wonogiri Reservoir was reduced by 65 million m3 from 440 million m3 in 1980 to 375 m3 in 2005 as recorded. One of parameter that used for assessment of the dam performance depends on erosion and sedimentation. This study aims to determine assessment of performance Wonogiri Dam in service of water needs due to erosion and sedimentation. Erosion and sedimentation analysis can be determined by using USLE (Universal Soil Loss Equation) and SRD (Sedimen Delivery Ratio) methods. As the result showed that erosion in Wonogiri Watershed has high erosion potential which gain 3,2 million m3/year. The Keduang Sub Watershed shows the highest level of erosion potential, which is between 1.175 million m3/year. The sedimentation rate result in Wonogiri Dam considered relatively high with rate value 1,948,000 m3/year. There for it is necessary that a comprehensive sedimentation management system is needed in the Wonogiri Watershed from both side, in technical and non technical aspect, such as reforestation or dredging activities. Based on the results of the analysis of the impact of erosion and sedimentation, it can be concluded that the performance evaluation of the Wonogiri Dam is include in the sufficient category because many activities have been carried out to restore the reservoir function to its original condition.
Processing of Local Bauxite to Obtain Highly Purified and Fine Alumina Powder
Authors: Ibrahim I , Baharuddin S , Arbain R , Othman A , Joannes C
Published: February 2021

A study on local bauxite was conducted at Mineral Research Centre, Ipoh to produce highly purified fine alumina (Al2O3) powder by using Bayer process as a basis. The study was conducted on a local bauxite from Johor. The raw material being classified having the specific gravity of 2.42 and the major constituent of mineral was identified as gibbsite in which indicates of having 58.7% Al2O3. Moreover, this raw material being classified as high silica content of bauxite ore because of the presence amount of SiO2 was slightly more than 7.0%. Four (4) major processes were performed at Mineral Research Centre such as sample preparation, characterization of raw material, precipitation and characterization of product. In order to produce highly purified and fine alumina, some alternative on leaching and precipitation processes were studied. These due to leaching process tends to pre-determine the rate of recovery and the purity of alumina whereas a very effective precipitation process can be applied to produce fine size of alumina powder. This paper presents some results of leaching and precipitation processes and probably help to show how various processing parameters will affect the effectiveness of alumina recovery, purity as well as its sizes.
Heavy Machinery Operators: Necessary Competencies to Reduce Construction Accidents
Authors: Bedi J K , Rahman R A , Din Z
Published: February 2021

The construction industry has been consistently performing poorly in safety resulting in substantial human and economic losses globally. The hazard related to heavy machinery operations can lead to injury or fatality of operators, workers, or visitors. Thus, safety training of heavy machinery operators (HMOs) is crucial to perform their tasks safely on construction projects. HMOs face various risks due to complex work environments at a job site such as the presence of other workers, material flow, equipment motion, and temporary structures that limit the space for heavy machinery. This research identifies the causes of accidents and competencies required to eliminate these accidents associated with heavy machinery operators. To achieve that, interview data with fifteen construction project managers are analyzed. This study’s findings suggest that the causes of heavy machinery accidents include insufficient maintenance, negligence of operators, inadequate training, human factor, and site condition. Conversely, the competencies to mitigate heavy machinery accidents are knowledge of safety incentives and penalties from safety training, the ability to conduct safety briefing, inspect heavy machinery and site conditions, and communication skills. Industry practitioners and researchers can use these findings to enhance construction productivity by creating a safe working environment at construction sites.
Current Practice in Rehabilitating Old Pipes for Water Distribution Network in Malaysia
Authors: Sufian S S , Romali N S , Rahman R A , Seman M A
Published: February 2021

The water distribution network (WDN) is critical in daily life because it provides treated water to consumers. However, WDN in Malaysia is facing a significant amount of water loss during the water distribution process (i.e., non-revenue water (NRW) with an average percentage of 35.6%. While one of the leading causes of NRW is old pipes, water operators are still facing barriers to rehabilitate old pipes to new pipes. Therefore, this study aims to identify the strategies to improve current practice in rehabilitating old pipes. To achieve that objective, open-ended individual interviews will be performed with sixteen individuals that have experience in managing WDN and NRW in Malaysia. This research contributes to identify the current practice/method, which has three main categories i.e. people, technology, and process in rehabilitating old pipes from industry practitioners’ perspectives, which could assist researchers and industry practitioners in developing strategies to reduce NRW among water operators. The findings of this research can help to improve WDN in reducing NRW.
Model Performance Index of Ground Water Irrigation Systems in the Karst Mountain Region: Case Study in Gunung Kidul Regency, Yogyakarta
Authors: Susilo Hendro , Purwantoro Dwi , Rahadiansyah Shakti
Published: February 2021

Ground Water Irrigation Network (GWIN) make a major contribution to agricultural production in karst mountainous areas, especially in the dry season. A performance index model would be developed to measure the level of success in developing groundwater irrigation systems. Performance evaluation of groundwater irrigation systems was a value called the Groundwater Irrigation Performance Index. This study aims to obtain determinants of the parameters of the index performance of groundwater irrigation that based on technical and non-technical aspects by analyzing the variables that give effect to the both aspects. Technical variables were physical infrastructure, supporting facilities, geological conditions, vegetation conditions, water recharge area conditions, direction of spatial planning, documentation, and crop productivity. Non-technical aspects were personnel organizations, P3A (Association of Water User Farmers’), and economic-socio-cultural. The locus of research was in the Karst Mountains area of Gunung Kidul Regency, Yogyakarta. The method used in collecting data was direct measurement of site visit and secondary data from the field. The non-technical aspects of using questionnaire data as qualitative data were converted into quantitative data. Smart Partial Least Squares was used for filtering variables. GRG-Generalized Reduced Gradient method was used to solve the non-linear equation with the objective-objective assumption and constraints. The model calibration test was calibrated and simulated on the parameters used. The results were a performance index model to measure the level of success in developing groundwater irrigation systems. The performance index evaluation of the developed groundwater irrigation system was an accumulation of technical indexes and non-technical indices involving influential variables.
Towards Better Contractor Performance to Achieve Sustainable Road Project Development
Authors: Shamsuddin Sabri Ir , Ali Mohd Nazri b , Aziz Rohayu Abd , Ismail Ir. Mohd Erie Husairrie b
Published: February 2021

Public Works Department (PWD) is heavily involved in road project management whether the project is conventional in-house, consultant or design and built. Nowadays, PWD has implemented aspects of sustainable road development to improve economic and social development simultaneously with environmental protection. Since 2016 until 2019, 13 road projects in the design stage have been certified Penarafan Hijau (pH JKR). The performance and sustainability of the road project will depend on the performance of the contractor who executes the project. Thus, the appointed contractor must perform well to ensure that the project can be completed within the specified time, cost and quality stipulated and achieve the goals of sustainable road development. To ensure that only the best contractor is chosen, it is important to have a database on the evaluation of a contractor’s performance. This paper proposes the best method to evaluate contractor performance comprehensively. The evaluation encompasses all aspects during construction, including site organisation, administration, planning work progress, work quality, the control of nominated subcontractors or suppliers, and implementing sustainable road development. The assessments were done every six months, and the marks given can be converted into grades to categorise each contractor’s performance. These assessments not only provide the data of contractor performance but will motivate contractors to perform at their peak throughout the project period.
Simulation Solvent Extraction of Rare Earth Metal Source Origin from Marine Sediment
Authors: Ahmat Farouq , Yunus Mohd Yusri Mohd , Ismail Nurul Ain
Published: February 2021

Ocean mining probably one of the world’s largest untapped resources of rare earth elements. Specifically, the rare earth resources from polymetallic nodule which receive less attention from industry due to the various challenges. This article studied the simulation HDEHP-HCl system fractional cascade extraction strategy for extraction of rare earth elements from polymetallic nodule. HDEHP-HCl was capable of complete extract very high purity rare earth elements (99.9%). The fractional cascade extraction strategy simulation designed for the separation of rare earth elements could be momentous for practical application. The simulation data shows high purity of products at both outlets, aqueous and organic are obtainable. All these will provide the promising industrial applications of HDEHP-HCl system in extracting rare earth elements from polymetallic nodule with more fundamental data and guidance.
Economical cultivation system of microalgae Spirulina platensis for lipid production
Authors: Palanisamy K M , Paramasivam P , Jayakumar S , Maniam G P , Rahim M H A , Govindan N
Published: February 2021

The marine algae Spirulina platensis was cultured in a medium of palm oil mill effluent (POME) and the production of lipid in the biomass was optimized. Among 7 species Spirulina platensis was isolated from the marine sample which have greater lipid potential was collected from Pantai Teluk Cempedak, Kuantan which is located at East Coast region of Pahang state. At 28+2 °C, the maximum lipid content in the biomass harvested at the end of a 15 days batch culture was quantified with the following values of the experimental factors: POME concentration with (10%, 20% and 30%) (v/v) and light intensity (3,000 lux, 4,000 lux, 5,000 lux). Under the optimized conditions with 20% of POME, the maximum dry mass concentration of the was 754.5 mg L−1 with lipid 34.5% production on day 13 of a batch culture, declining to ∼687 mg L−1 on day 15. At 5,000 lux light intensities, the maximum yield obtained was 854.6 mg L−1 with lipid 35.8% production on day 14, it declined to 732.8 mg L−1 on day 15.
Low-Calcination Temperature to Synthesize A-Alumina From Aluminium Waste Can Using Sol-Gel Method
Authors: Omer Al Haiqi , Bin Mokaizh A A , Shariffuddin Jun Haslinda Binti Haji
Published: February 2021

Many countries around the world are facing issues in managing solid waste materials; most of these wastes such as aluminium can are deposited to the landfills, leading to environmental pollution. Recycling is considered as an effective technique to manage the aluminium can waste since it can provide benefits in terms of energy savings, reduce volumes of waste and cost-effectiveness. In this article, it was desired to turn the aluminium can waste into α-Alumina using sol-gel method. Alumina exists in many crystalline structures which degenerate to the most stable hexagonal α-phase at high temperatures. α-Alumina (a-Al2O3) is the most stable crystalline structure widely used and studied as electronic packaging, corrosion resistance ceramics, high-temperature structural material, and translucent ceramics. FTIR, XRD, SEM-EDX, TGA, and BET were employed to investigate the properties of a-alumina. The experimental results obtained from this study demonstrates the possibility of producing alumina from an aluminium can waste with the exact surface area of 5.2105 m2/g, crystallite size at 132.50 nm and total weight loss of 2.71% at 900 °C calcination temperature.
Water Quality Monitoring and Evaluation in the Bengawan Solo River Region
Authors: Sri Wahyu Kusumastuti A , Moh Bisri B , Solichin C , Tri Budi P D
Published: February 2021

The Bengawan Solo River Region with an area of 19,778 km2 consists of 96 watersheds with four main watersheds, namely the Bengawan Solo watershed with an area of 15,295.69 km2, which has a main river, the Bengawan Solo River which flows from Wonogiri to the downstream area on the north coast of Gresik Regency, Grindulu Lorog Watershed with 1,040,656 km2 area, Corong watershed with an area of 815,081 km2, and Lamong watershed with an area of 760,292 km2. Bengawan Solo River crosses various areas both natural and cultivated areas including forests, rice fields, to settlements and industries, causing changes in water quality from upstream to downstream. The purpose of this study was to determine the level of pollution in the Bengawan Solo River Region from upstream to downstream. This research method is to analyze the parameters of the results of testing water quality samples at several points with the Pollution Index method for second grade water quality then spatially analyzed. The results showed that of the 29 monitoring points of river water quality in the Bengawan Solo River Region, 17% were heavily polluted, 59% were moderately polluted, 24% were light polluted, and 0% were meeting quality standards. Therefore, efforts are needed to manage the river based on its water quality by maintaining the capacity of the river against pollution loads that can be received by water bodies.
Research on Value Perception Models and Strategies of Electric Power Users
Authors: Li Pingwen , Yin Shuo , Yang Meng , Guo Xingwu , Jin Man , Yan Jing , Zhang Na
Published: February 2021

Energy management business is to provide a “management nature” business for the user’s energy use process, focusing on the management of the user’s energy system, improving the efficiency of energy use, and reducing the user’s energy cost. The key factor that affects the transformation of consumer psychology into consumer behaviour is the value of electricity value-added services. This article constructs a quantitative model for the perceived value of energy management business, which is based on the definition of user value perception and value-added service value perception function, so as to serve electricity sales companies to develop integrated energy business.
Failure Analysis of Metal Oxide Surge Arrester on Busbar of 220kV Substation
Authors: Zhang Dewen , Huang Hai , Zhao Xiangyu , Shang Fang , Zhu Linlin , Hu Xiaoxu
Published: February 2021

MOA (Metal Oxide Arrester) is widely used in power systems because of its good nonlinear volt-ampere characteristics and current-carrying capacity. Its long-term operation may have defects such as heat generation and reduced insulation performance. This paper analyzes a 220kV substation bus lightning arrester, collects fault recording information, points out the cause of the fault and puts forward corresponding preventive measures.
Facile electrodeposited MnO2 as cathode materials for Zn-ion batteries
Authors: Chen Siwei , Wang Pei , Song Ming
Published: February 2021

MnO2 prepared through facile electrochemical-deposition method at different deposition time on Ni foam substrates are used as cathode materials for Zn-ion batteries. The results show that the electrode using the condition of deposition current of 80 mA for 10 min has the best overall electrochemical performances. The specific capacity measured by the electrode position of the MnO2 electrode for 5 min is the highest, but the cycle performance of the sample is poor. The specific capacity measured by electrode position of the MnO2 electrode sample for 20 min is the lowest, but the cycle performance of the sample is the best.
A software and hardware design of intelligent measurement and control terminal of distribution network based on a communication adaptive approach
Authors: Ding Yujie , Xiao Xiaobing , Tian Hao , Liu Chang , Ouyang Guangze , Zhang Ruifeng
Published: February 2021

With the development of science and technology, the hardware and software design of transformer intelligent measurement and control terminal is very important. Based on the hardware and software appization of internet of things, the design scheme of hardware and software structure is given. Supported by high-performance operating system, the terminal device can be upgraded flexibly through APP application software. The intelligent terminal pair can realize full data collection, full control and full fusion, and real-time exchange of key operation data with the power distribution master station. The intelligent terminal can support 5G communication and realize full compatibility of communication conditions downward.