bluuebunny/crossref_metadata_2025 huggingface dataset:
Voltage dependence of equivalent circuit parameters of bilayer organic photovoltaics
Authors: Thongprong Non , Duxbury Phillip M.
Published: February 2021

Despite the very different underlying physics of organic photovoltaics (OPVs), inorganic p-n junction’s Shockley’s diode equation is often applied to describe current density–voltage (JV) curves of OPVs. The model parameters, including the diode saturation current, diode ideality factor, series, and parallel resistances, are usually extracted and treated as constants in JV curve analyses. In this work, we develop a drift-diffusion bilayer interface (DD-BI) model for bilayer OPVs, which treats the donor–acceptor (D–A) heterojunction using the detailed balance between densities of polaron pairs, free electrons, and free holes. From the DD-BI model, we derive a diode equation, which is of Shockley’s equation form, but each parameter is explicitly written in terms of the D–A interface properties. We call this model the self-consistent diode (SCD) model as it is consistent with the DD-BI results provided that the key parameters are from the simulation data. By studying the effects of light intensity and carrier mobility, we find that the Shockley SCD parameters are voltage dependent because of space charge accumulation around the D–A heterojunction. Our models are successful in explaining the common discrepancies in OPV JV curve analyses, such as the validity of fitting for series resistance, deviation of ideality factor from the theoretical values, and different resistance values under light and dark conditions. The results provide a better understanding of OPVs with a D–A heterojunction and how we can capture its physics using the SCD equation.
Impact of lattice plane orientation in TiO2 based resistive switching memory: A computational approach
Authors: Chen Yu-Li , Balraj Babu , Chung Pei-Fang , Sivakumar Chandrasekar , Lee Wen-Jay , Ho Mon-Shu
Published: February 2021

Resistive Random Access Memories (ReRAMs) are promising future candidates for nonvolatile memory. The underlying mechanism involves resistive switching in high-k dielectric layers, and changes in resistance due to different mechanisms are caused by the evolution of defective structures triggered by electrical and thermal effects. For the memory purpose of the ReRAM, the electrical field can be used to adjust the resistance of the resistance material for the storage of information. In this study, nonequilibrium molecular dynamics simulations with the charge equilibration method are used to study the electrochemical reactions of ReRAMs. The Cu/TiO2/Ti heterojunction structures with (100)/(001), (100)/(110), (100)/(111), and (100)/(120) lattice planes as grains are considered to investigate the resistive switching properties based on the electrical, thermal, and structural properties of three models. Dielectric layers with the grain boundary of the bicrystal structure are composed of titanium dioxide nanoparticles. Our results demonstrate that an applied external electric field on grain boundaries is a key issue in resistive switching. Furthermore, the simulation results were verified with the experimental data. Overall, this simulation work provides details of the fundamental mechanism of resistance switching, including variation of the atomic structure and electronic properties, at the atom length scale and picosecond timescale, which suggest a number of useful aspects for the future development and optimization of materials for this ReRAM technology.
Analyzing the driving forces of insulin stability in the basic amino acid solutions: A perspective from hydration dynamics
Authors: Santra Santanu , Dhurua Shakuntala , Jana Madhurima
Published: February 2021

Amino acids having basic side chains, as additives, are known to increase the stability of native-folded state of proteins, but their relative efficiency and the molecular mechanism are still controversial and obscure as well. In the present work, extensive atomistic molecular dynamics simulations were performed to investigate the hydration properties of aqueous solutions of concentrated arginine, histidine, and lysine and their comparative efficiency on regulating the conformational stability of the insulin monomer. We identified that in the aqueous solutions of the free amino acids, the nonuniform relaxation of amino acid–water hydrogen bonds was due to the entrapment of water molecules within the amino acid clusters formed in solutions. Insulin, when tested with these solutions, was found to show rigid conformations, relative to that in pure water. We observed that while the salt bridges formed by the lysine as an additive contributed more toward the direct interactions with insulin, the cation–π was more prominent for the insulin–arginine interactions. Importantly, it was observed that the preferentially more excluded arginine, compared to histidine and lysine from the insulin surface, enriches the hydration layer of the protein. Our study reveals that the loss of configurational entropy of insulin in arginine solution, as compared to that in pure water, is more as compared to the entropy loss in the other two amino acid solutions, which, moreover, was found to be due to the presence of motionally bound less entropic hydration water of insulin in arginine solution than in histidine or lysine solution.
Relationship between human exhalation diffusion and posture in face-to-face scenario with utterance
Authors: Ishii Keiko , Ohno Yoshiko , Oikawa Maiko , Onishi Noriko
Published: February 2021

Because of the COVID-19, the world has been affected significantly. Not only health and medical problems but also the decline in life quality and economic activity due to the suspension of social activities cannot be disregarded. It is assumed that the virus is transmitted through coughing and sneezing; however, the possibility of airborne infection by aerosols containing viruses scattered in the air has become a popular topic recently. In airborne infections, the risk of infection increases when the mucous membrane is exposed to exhaled aerosols for a significant amount of time. Therefore, in this study, we visualize human breath using the smoke of electronic cigarettes as tracer particles. Exhalation when speaking was visualized for four human posture patterns. The result shows that the exhaled breath is affected by the body wall temperature; it rises when it remains in the boundary layer by wearing a mask. On the other hand, without a mask, it initially flows downward due to the structure of the nose and mouth, so it flows downward due to inertia and diffuses randomly. This finding is effective in reducing the risk of infection during face-to-face customer service.
Cascade of torus birth bifurcations and inverse cascade of Shilnikov attractors merging at the threshold of hyperchaos
Authors: Sataev I. R. , Stankevich N. V.
Published: February 2021

We study the hyperchaos formation scenario in the modified Anishchenko–Astakhov generator. The scenario is connected with the existence of sequence of secondary torus bifurcations of resonant cycles preceding the hyperchaos emergence. This bifurcation cascade leads to the birth of the hierarchy of saddle-focus cycles with a two-dimensional unstable manifold as well as of saddle hyperchaotic sets resulting from the period-doubling cascades of unstable resonant cycles. Hyperchaos is born as a result of an inverse cascade of bifurcations of the emergence of discrete spiral Shilnikov attractors, accompanied by absorbing the cycles constituting this hierarchy.
The convergence of combustion models and compliance with the Kolmogorov scaling of turbulence
Authors: Klimenko A. Y.
Published: February 2021

Development of turbulent combustion models has resulted in the convergence of some of the probability density function models with models based on the effective use of the mixture fraction. These new models are global but implement localized mixing and are compliant with the laws of the inertial interval of turbulence and, consequently, are consistent with the fast chemistry and flamelet limits. This consistency can be extended to distributed premixed flames but, generally, not to premixed flamesheets. We show that turbulent scaling of premixed flamesheets is not exactly the same as the Kolmogorov scaling of turbulence and, to some extent, still remains unknown. The proposed interpretation for the scaling of turbulent premixed flames in flamesheet regimes is consistent with experiments, upholds principal elements of Kolmogorov's theory of turbulence, and can serve as a possible explanation and/or a guiding constraint for practical modeling.
Impurity band assisted carrier relaxation in Cr doped topological insulator Bi2Se3
Authors: Tu Jian , Zhao Yafei , Zhang Xiaoqian , Nie Zhonghui , Li Yao , Zhang Yilin , Turcu Ion Cristian Edmond , Poletto Luca , Frassetto Fabio , Ruan Xuezhong , Zhong Wenbin , Wang Xuefeng , Liu Wenqing , Zhang Yu , Zhang Rong , Xu Yongbing , He Liang
Published: February 2021

Topological insulators (TIs) with unique band structures have wide application prospects in the fields of ultrafast optical and spintronic devices. The dynamics of hot carriers plays a key role in these TI-based devices. In this work, using the time- and angle-resolved photoemission spectroscopy technique, the relaxation process of the hot carriers in Cr-doped Bi2Se3 has been systematically studied since the ferromagnetic TI is one of the key building blocks for next-generation spintronics. It is found that electronic temperature (Te) and chemical potential (μ) decrease faster with the increase in the Cr doping concentration. Similarly, the lifetime (τ) of the excited electrons also decreases with more Cr doped into Bi2Se3. The results suggest a mechanism of impurity band-assisted carrier relaxation, where the impurity band within the bulk bandgap introduced by Cr doping provides significant recombination channels for the excited electrons. This work directly illustrates the dynamic process of the photon-generated carriers in Cr-doped Bi2Se3, which is expected to promote the applications of (Bi1-xCrx)2Se3 in photoelectric devices.
Controllability of voltage- and calcium-driven cardiac alternans in a map model
Authors: Muñoz Laura M. , Ampofo Mark O. , Cherry Elizabeth M.
Published: February 2021

Certain cardiac arrhythmias are preceded by electrical alternans, a state characterized by beat-to-beat alternation in cellular action potential duration. Cardiac alternans may arise from different mechanisms including instabilities in voltage or intracellular calcium cycling. Although a number of techniques have been proposed to suppress alternans, these methods have mainly been tested using models that do not support calcium-driven alternans. Therefore, it is important to understand how control methods may perform when alternans is driven by instabilities in calcium cycling. In this study, we applied controllability analysis to a discrete map of alternans dynamics in a cardiac cell. We compared two different controllability measures to determine to what extent different control strategies could suppress alternans and tested these predictions using three feedback controllers. We found a modal controllability measure, unlike the minimum singular value of the controllability matrix, consistently indicated the control strategies requiring the least control effort and yielding the smallest closed-loop eigenvalue. In addition, action potential duration was identified as the most effective variable through which control can be applied, regardless of alternans mechanism, although sarcoplasmic reticulum calcium load was also useful for the calcium-driven alternans cases.
Tuning the hexane isomer separation performances of Zeolitic Imidazole Framework-8 using mechanical pressure
Authors: Zhao Henglo , Maurin Guillaume , Ghoufi Aziz
Published: February 2021

Hybrid osmotic Monte Carlo simulations were performed to anticipate the tunability of the separation performance of the flexible Zeolitic Imidazole Framework-8 (ZIF-8) via the application of an external mechanical pressure. This synergistic combination of mechanical control of the pore aperture/cage dimension and guest adsorption was applied to the challenging hexane isomers separation processes of vital importance in the field of petrochemical industry. The application of a mechanical pressure above 1 GPa was predicted to boost the linear hexane/2-methylpentane and 2-methylpentane/2,3-dimethylbutane selectivity by 40% and 17%, respectively, as compared to the pristine ZIF-8. We further unraveled the microscopic origin of this optimized performance with an in-depth analysis of the critical interplay between the structural changes of the ZIF-8 framework and the conformational rearrangements of C6 isomers under mechanical pressure.
Iron(II) spin crossover complexes with a sulfur rich ligand backbone
Authors: Schönfeld Sophie , Baier Felix , Jungklaus Jennifer , Hörner Gerald , Winterstein Simon , Enders Axel , Senker Jürgen , Weber Birgit
Published: February 2021

One goal that many scientists pursue is the unification of several interesting chemical or physical properties in one system, as only multifunctional materials will meet the challenges of today's technologies. With this background, three novel iron(II) coordination compounds with a Schiff base-like N2O2 coordinating ligand L bearing a sulfur-rich backbone are investigated in this work. Two of the complexes, the mononuclear [FeL(py)2] (py = pyridine) and the coordination polymer {[FeL(bpee)]}n [bpee = trans-1,2-bis(4-pyridyl)ethene], show spin crossover behavior followed using magnetic susceptibility measurements and Mössbauer spectroscopy. To get a closer insight into different states of the complex spin crossover behavior of {[FeL(bpee)]}n, XPS measurements were conducted at different temperatures. Furthermore, impedance spectroscopic measurements at variable temperatures were performed to get insight into the electrical conductivity of this system. All iron(II) complexes were electrochemically characterized using cyclovoltammetric measurements, supplemented by DFT computation. Apparently, the extension by a sulfur backbone leads to a stabilization of the HOMO. Due to this, the complexes are more difficult to oxidize than comparable systems. With {[FeL(azpy)]}n, another coordination polymer, this time axially decorated by the redox-active ligand azpy (azpy = 4,4′-azopyridine), is investigated, which is, however, a pure high spin complex.
Oviposition-promoting pars intercerebralis neurons showperiod-dependent photoperiodic changes in their firing activity in the bean bug
Authors: Hasebe Masaharu , Shiga Sakiko
Published: February 2021

Significance

Animals adapt to seasonal changes by photoperiodic modulation of their physiology and behavior. It is widely recognized that circadian clock systems underlie photoperiodic regulation. However, the importance of clock genes in photoperiodic responses at the cellular level is poorly understood. In this study, we focused on the insect neuroendocrine center, pars intercerebralis (PI), which is known to be homologous to the vertebrate hypothalamus. A combination of electrophysiological and genetic analyses revealed that oviposition-promoting PI neurons showed photoperiodic responses dependent on the clock geneperiod. This report shows the significance of a clock gene in cellular photoperiodic responses. The present analyses are a good model for revealing clock-gene-dependent photoperiodic responses at the cellular level.
Toward an understanding of myofibrillar function in health and disease
Authors: Moss Richard L. , Cremo Christine , Granzier Henk L.
Published: February 2021

The March 2021 issue of JGP is a collection of peer-reviewed articles focused on the function and dynamic regulation of contractile systems in muscle and non-muscle cells.
Determinism and General Relativity
Authors: Smeenk Chris , Wüthrich Christian
Published: February 2021

We investigate the fate of determinism in general relativity (GR), comparing the philosopher’s account with the physicist’s well-posed initial value formulations. The fate of determinism is interwoven with the question of what it is for a spacetime to be ‘physically reasonable’. A central concern is the status of global hyperbolicity, a putatively necessary condition for determinism in GR. While global hyperbolicity may fail to be true of all physically reasonable models, we analyze whether global hyperbolicity should be (i) imposed by fiat; (ii) established from weaker assumptions, as in cosmic censorship theorems; or (iii) justified by beyond-GR physics.
Approximate Coherentism and Luck
Authors: Babic Boris
Published: February 2021

Approximate coherentism suggests that imperfectly rational agents should hold approximately coherent credences. This norm is intended as a generalization of ordinary coherence. I argue that it may be unable to play this role by considering its application under learning experiences. While it is unclear how imperfect agents should revise their beliefs, I suggest a plausible route is through Bayesian updating. However, Bayesian updating can take an incoherent agent from relatively more coherent credences to relatively less coherent credences, depending on the data observed. Thus, comparative rationality judgments among incoherent agents are unduly sensitive to luck.
Plasma propagation in a single bead DBD reactor at different dielectric constants: insights from fluid modelling
Authors: Wang Weizong , Butterworth Tom , Bogaerts Annemie
Published: February 2021

Packed bed dielectric barrier discharge (PB-DBD) plasma reactors are very promising for various plasma catalysis applications, but the exact mechanisms of plasma–catalyst interaction are far from understood, because the plasma discharge and catalyst/packing properties are mutually dependent. To better understand the effect of packing dielectric material on the electrical plasma properties, we study here a single bead DBD plasma reactor operating in dry air, with beads of different dielectric constant and for different applied voltages, by means of fluid modelling validated by optical imaging experiments. Our study reveals that the plasma in the single bead DBD reactor can manifest itself in two different modalities, i.e. (a) polar discharges at the bead poles in contact with the electrodes, and (b) a streamer discharge caused by surface ionization waves, which bridges the gas gap. Beads with high dielectric constant result in localised electric field enhancement and hence yield a reduction of the applied voltage required for plasma production. At low applied voltage, the discharge appears as polar discharges between the bead and the electrodes, and upon higher voltage it undergoes a transition into a bridging streamer discharge. The transition voltage to the streamer mode rises for beads with higher dielectric constant. These observations are important for plasma catalysis applications. A higher dielectric constant yields a higher electric field and thus higher average electron energy and density, giving rise to more reactive species, but it also yields a confined discharge near the contact points of packing beads, limiting the interaction area between the catalyst and the active plasma species. In addition, our model reveals that the dielectric bead behaves as a capacitor and traps charges, which can explain the significant occurrence of partial discharging in PB-DBDs and non-parallelogram shaped Lissajous plots. Hence, equivalent circuit modelling of PB-DBDs should take into account the role of packing beads in charge trapping as a capacitor.
Role of flexural phonons in carrier mobility of two-dimensional semiconductors: free standing vs on substrate
Authors: Zhang Chenmu , Cheng Long , Liu Yuanyue
Published: February 2021

Two-dimensional (2D) semiconductor is a promising material for future electronics. It is believed that the flexural phonon (FP) induced scattering plays an important role in the room-temperature carrier mobility, and the substrate can significantly affect such scattering. Here we develop an ‘implicit’ substrate model, which allows us to effectively quantify different effects of the substrate on the FP scattering. In conjunction with the first-principles calculations, we study the intrinsic mobilities of the holes in Sb and electrons in MoS2 as representative examples for 2D semiconductors. We find that the FP scattering is not dominant and is weaker than other scatterings such as that induced by longitudinal acoustic (LA) phonon. This is due to the significantly smaller electron–phonon-coupling (EPC) matrix elements for the FP compared with that for the LA phonon in the free-standing case; although the substrate enhances the FP EPC, it suppresses the FP population, making the FP scattering still weaker than the LA scattering. Our work improves the fundamental understanding of the role of FP and its interaction with the substrate in carrier mobility, and provides a computational model to study the substrate effects.
A repeat positioning, scanning tunneling microscope based on a straight-push piezoelectric nanopositioner
Authors: Guo Wenjing , Wang Jihao , Xia Zhigang , Zhang Jingjing , Lu Qingyou
Published: February 2021

In this paper, we develop a repeat positioning, scanning tunneling microscope (STM), whose core component is a new straight-push piezoelectric nanopositioner. The special rigid frame structure and straight-push stepping method of this nanopositioner ensure that there is no lateral deviation while it is stepping. It has a smaller volume and a lower driving voltage than that of traditional piezoelectric nanopositioners with the same load capacity. The test results show that its threshold voltage is only 4 V. Additionally, when the driving signal frequency is constant, its step size and the amplitude of the driving signal show a linear relationship. Moreover, when the driving signal amplitude is constant, the velocity and driving signal frequency of the nanopositioner also show a linear relationship. In addition, the small STM (diameter less than 10 mm, length less than 50 mm) designed on the basis of this nanopositioner can work at full low-voltage. The STM’s high-resolution images and repeatable positioning performance are demonstrated in detail in this article. When the STM moves back and forth along the Z direction at a millimeter-scale distance, its positioning deviation in the same area of the sample is less than 30 nm. The capacity of the STM is very important for tracking and observing the different characteristics of some samples in different test conditions and is also significant for applications such as multi-tip collaborative work.
Ohmic contact formation for inkjet-printed nanoparticle copper inks on highly doped GaAs
Authors: Hayati-Roodbari Nastaran , Wheeldon Alexander , Hendler Carina , Fian Alexander , Trattnig Roman
Published: February 2021

GaAs compound-based electronics attracted significant interest due to unique properties of GaAs like high electron mobility, high saturated electron velocity and low sensitivity to heat. However, GaAs compound-based electronics demand a significant decrease in their manufacturing costs to be a good competitor in the commercial markets. In this context, copper-based nanoparticle (NP) inks represent one of the most cost-effective metal inks as a proper candidate to be deposited as contact grids on GaAs. In addition, Inkjet-printing, as a low-cost back-end of the line process, is a flexible manufacturing method to deposit copper NP ink on GaAs. These printed copper NP structures need to be uncapped and fused via a sintering method in order to become conductive and form an ohmic contact with low contact resistivity. The main challenge for uncapping a copper-based NP ink is its rapid oxidation potential. Laser sintering, as a fast uncapping method for NPs, reduces the oxidation of uncapped copper. The critical point to combine these two well-known industrial methods of inkjet printing and laser sintering is to adjust the printing features and laser sintering power in a way that as much copper as possible is uncapped resulting in minimum contact resistivity and high conductivity. In this research, copper ink contact grids were deposited on n-doped GaAs by inkjet-printing. The printed copper ink was converted to a copper grid via applying the optimized settings of a picosecond laser. As a result, an ohmic copper on GaAs contact with a low contact resistivity (8 mΩ cm2) was realized successfully.
Electrodeposition of (111)-oriented and nanotwin-doped nanocrystalline Cu with ultrahigh strength for 3D IC application
Authors: Zheng Zeyang , Huang Yu-Ting , Wang Zhenyu , Zhang Mingyang , Wang Wei-Ting , Chung Chih-Chun , Cherng Sheng-Jye , Tsai Ya-Hui , Li Po-Chien , Lu Zhouguang , Chen Chih-Ming , Feng Shien-Ping
Published: February 2021

The mechanical performance of electroplated Cu plays a crucial role in next-generation Cu-to-Cu direct bonding for the three-dimension integrated circuit (3D IC). This work reports direct-current electroplated (111)-preferred and nanotwin-doped nanocrystalline Cu, of which strength is at the forefront performance compared with all reported electroplated Cu materials. Tension and compression tests are performed to present the ultrahigh ultimate strength of 977 MPa and 1158 MPa, respectively. The microstructure of nanoscale Cu grains with an average grain size around 61 nm greatly contributes to the ultrahigh strength as described by the grain refinement effect. A gap between the obtained yield strength and the Hall–Petch relationship indicates the presence of extra strengthening mechanisms. X-ray diffraction and transmission electron microscopy analysis identify the highly (111) oriented texture and sporadic twins with optimum thicknesses, which can effectively impede intragranular dislocation movements, thus further advance the strength. Via filling capability and high throughput are also demonstrated in the patterned wafer plating. The combination of ultrahigh tensile/compressive strength, (111) preferred texture, superfilling capability and high throughput satisfies the critical requirement of Cu interconnects plating technology towards the industrial manufacturing in advanced 3D IC packaging application.
Perovskite random lasers: a tunable coherent light source for emerging applications
Authors: Kao Tsung Sheng , Hong Yu-Heng , Hong Kuo-Bin , Lu Tien-Chang
Published: February 2021

Metal halide perovskites have attracted increasing attention due to their superior optical and electrical characteristics, flexible tunability, and easy fabrication processes. Apart from their unprecedented successes in photovoltaic devices, lasing action is the latest exploitation of the optoelectronic performance of perovskites. Among the substantial body of research on the configuration design and light emission quality of perovskite lasers, the random laser is a very interesting stimulated emission phenomenon with unique optical characteristics. In this review article, we first comprehensively overview the development of perovskite-based optoelectronic devices and then focus our discussion on random lasing performance. After an introduction to the historical development of versatile random lasers and perovskite random lasers, we summarize several synthesis methods and discuss their material configurations and stability in synthesized perovskite materials. Following this, a theoretical approach is provided to explain the random lasing mechanism in metal halide perovskites. Finally, we propose future applications of perovskite random lasers, presenting conclusions as well as future challenges, such as quality stability and toxicity reduction, of perovskite materials with regard to practical applications in this promising field.
Artificial intelligence supported single detector multi-energy proton radiography system
Authors: van der Heyden Brent , Cohilis Marie , Souris Kevin , de Freitas Nascimento Luana , Sterpin Edmond
Published: February 2021

Proton radiography imaging was proposed as a promising technique to evaluate internal anatomical changes, to enable pre-treatment patient alignment, and most importantly, to optimize the patient specific CT number to stopping-power ratio conversion. The clinical implementation rate of proton radiography systems is still limited due to their complex bulky design, together with the persistent problem of (in)elastic nuclear interactions and multiple Coulomb scattering (i.e. range mixing). In this work, a compact multi-energy proton radiography system was proposed in combination with an artificial intelligence network architecture (ProtonDSE) to remove the persistent problem of proton scatter in proton radiography. A realistic Monte Carlo model of the Proteus®One accelerator was built at 200 and 220 MeV to isolate the scattered proton signal in 236 proton radiographies of 80 digital anthropomorphic phantoms. ProtonDSE was trained to predict the proton scatter distribution at two beam energies in a 60%/25%/15% scheme for training, testing, and validation. A calibration procedure was proposed to derive the water equivalent thickness image based on the detector dose response relationship at both beam energies. ProtonDSE network performance was evaluated with quantitative metrics that showed an overall mean absolute percentage error below 1.4% ± 0.4% in our test dataset. For one example patient, detector dose to WET conversions were performed based on the total dose (

I

Total

), the primary proton dose (

I

Primary

), and the ProtonDSE corrected detector dose (

I

Corrected

). The determined WET accuracy was compared with respect to the reference WET by idealistic raytracing in a manually delineated region-of-interest inside the brain. The error was determined 4.3% ± 4.1% for

WET

(

I

Total

)

,

2.2% ± 1.4% for

WET

(

I

Primary

)

,

and 2.5% ± 2.0% for

WET

(

I

Corrected

)

.
Driver sleepiness detection with deep neural networks using electrophysiological data
Authors: Hultman Martin , Johansson Ida , Lindqvist Frida , Ahlström Christer
Published: February 2021

Objective. The objective of this paper is to present a driver sleepiness detection model based on electrophysiological data and a neural network consisting of convolutional neural networks and a long short-term memory architecture. Approach. The model was developed and evaluated on data from 12 different experiments with 269 drivers and 1187 driving sessions during daytime (low sleepiness condition) and night-time (high sleepiness condition), collected during naturalistic driving conditions on real roads in Sweden or in an advanced moving-base driving simulator. Electrooculographic and electroencephalographic time series data, split up in 16 634 2.5 min data segments was used as input to the deep neural network. This probably constitutes the largest labeled driver sleepiness dataset in the world. The model outputs a binary decision as alert (defined as ≤6 on the Karolinska Sleepiness Scale, KSS) or sleepy (KSS ≥ 8) or a regression output corresponding to KSS ϵ [1–5, 6, 7, 8, 9]. Main results. The subject-independent mean absolute error (MAE) was 0.78. Binary classification accuracy for the regression model was 82.6% as compared to 82.0% for a model that was trained specifically for the binary classification task. Data from the eyes were more informative than data from the brain. A combined input improved performance for some models, but the gain was very limited. Significance. Improved classification results were achieved with the regression model compared to the classification model. This suggests that the implicit order of the KSS ratings, i.e. the progression from alert to sleepy, provides important information for robust modelling of driver sleepiness, and that class labels should not simply be aggregated into an alert and a sleepy class. Furthermore, the model consistently showed better results than a model trained on manually extracted features based on expert knowledge, indicating that the model can detect sleepiness that is not covered by traditional algorithms.
Development of EGFET-based ITO pH sensors using epoxy free membrane
Authors: Ahmed Naser M , Sabah Fayroz A , Al-Hardan Naif H , Almessiere Munirah A , Mohammad Sabah M , Foong Lim Way , Jumaah Maadh , Islam A K M Shafiqul , Hassan Z , Quah Hock Jin , Afzal Naveed
Published: February 2021

The design of high-performance cavity for the accurate and efficient operation of various pH sensors remains challenging. In this paper, we report the simplistic design of an epoxy-free cavity with good quality contact effective for the extended gate field effect transistor (EGFET)-based pH sensors. This inexpensive, simple and leakage current free brass-based Teflon cavity was designed to separate the sensitive film devoid of the epoxy. The performance of the proposed cavity was assessed against four indium tin oxide (ITO) thin films (sensing membranes acted as pH sensors) of different sheet resistance by integrating into EGFET. The structure, morphology and sensing characteristics of these ITO membranes were determined as a function of varying resistance. The results revealed the formation of excellent electrical contacts and responses of these sensors to the changing pH values. The proposed pH sensors with the resistance of 2.5, 9.0, 15 and 35 kΩ showed the corresponding sensitivity of 34.86, 30, 16.66 and 17.5 mV pH−1, respectively. It is asserted that the designed cavity may contribute towards the evolution of efficient sensing electrodes desired for diverse applications in the field of pH, biomedical, electrochemical and ions selective sensors.
Controllable four-wave mixing based on quantum dot-cavity coupling system
Authors: Xing Hong-Wu , Chen Bin , Xing Li-Li , Chen Jian-Bin , Xue Hai-Bin , Guo Kang-Xian
Published: February 2021

We theoretically study the four-wave mixing (FWM) response in a quantum dot-cavity coupling system, where a two-level quantum dot (QD) is placed in an optical cavity while the cavity mode is coupled to the nanomechanical resonator via radiation pressure. The influences of the QD-cavity coupling strength, the Rabi coupling strength of the QD, and the power of the pump light on the FWM intensity are mainly considered. The numerical results show that the FWM intensity in this hybrid system can be significantly enhanced by increasing the QD-cavity coupling strength. In addition, the FWM intensity can be effectively modulated by the Rabi coupling strength and the pump power. Furthermore, the effects of the cavity decay rate and the cavity-pump detuning on the FWM signal are also explored. The obtained results may have potential applications in the fields of quantum optics and quantum information science.
Transient heating in fixed length optical cavities for use as temperature and pressure standards
Authors: Ricker J , Douglass K O , Syssoev S , Stone J , Avdiaj S , Hendricks J H
Published: February 2021

Optical refractometry techniques enable realization of both pressure and temperature directly from properties of the gas. The NIST refractometer, a fixed length optical cavity (FLOC) has previously been evaluated for operation as pressure standard, and now in this paper, is evaluated for the feasibility of operation as a primary temperature standard as well. The challenge is that during operation, one cavity is filled with gas. Gas dynamics predicts that this will result in heating which in turn will affect the cavity temperature uniformity, impeding the ability to measure the gas temperature with sufficient accuracy to make the standard useful as a primary standard for temperature or pressure. Temperature uniformity across the refractometer must be less than 0.5 mK for measurements of the refractivity to be sufficiently accurate for the FLOC. This paper compares computer modeling to laboratory measurements, enabling us to validate the model to predict thermal behavior and to accurately determine the measurement uncertainty of the technique. The results presented in this paper show that temperature of the glass elements of the refractometer and ‘thermal-shell’ copper chamber are equivalent to within 0.5 mK after an equilibration time of 3000 s (when going from 1 kPa to 100 kPa). This finding enables measurements of the copper chamber to determine the gas temperature to within an uncertainty (k = 1) of 0.5 mK. Additionally, the NIST refractometer is evaluated for feasibility of operation as temperature standard.
Investigation on the removal of nitrate from water using different types of biosorbents
Authors: Ang B Y H , Ong Y H , Ng Y S
Published: February 2021

Eutrophication due to excessive leaching of dissolved nitrogen is a principal cause of water quality degradation. Among different types of removal methods, adsorption is contemporarily deemed favourable due to its simplicity, efficiency and reusability. In this study, six biosorbent candidates, namely rambutan skin (RS), passion fruit skin (PFS), longan seeds (LS), chia seeds (CS), papaya seeds (PS), and luffa (L) were investigated for nitrate removal from water at pH 3.0, room temperature, initial nitrate concentration of 50 mg/L, biosorbent particle size of 425 μm, contact duration of 4 h, shaking speed of 120 rpm, and biosorbent dosage of 0.1 g. Shake flask method was carried out in the adsorption experiments to investigate the effect of heat treatment and acid treatment on the uptake of nitrate from water. The results showed that acid- and heat-treated passion fruit skin biosorbent (biochar, PFSBC) has the best biosorption performance for nitrate uptake of 5.179 mg/g. This biochar possessed high porosity, and abundant surface functional groups for nitrate adsorption.
Water usage behaviour: Case study in a southern state in Peninsular Malaysia
Authors: Muhammad N S , Abdullah J , Rahman N Abd , Razali N A
Published: February 2021

Generally, Malaysia’s per capita water consumption is high. Therefore, this study perform a thorough investigation on a water consumption that is related to a middle-class community in Malaysia, which accounts for the highest income group in the country. Specifically, we focused on three major categories, i.e. domestic water-usage activities, water habits of the community, and water-saving efforts that can be easily adopted. The main source of data was collected using structured interview method. The frequency of indoor water usage of more than four times a day was high, which suggested that most people did not control their water consumption, especially for cooking, bathing/showering, toilet usage, and dish washing. Community awareness in terms of water-saving efforts is low, as indicated by the respondents that uses dual-pump cisterns in their toilets and employs rainwater-harvesting system for non-potable use. Low water tariff in the study area may discouraged the residents to practice water-saving measures. The findings from this study are important, particularly in understanding the activities and habits associated with high water usage. Additionally, the relevant stakeholders can use these findings to formulate a pro-active action plan to achieve the water usage of 165 litres/capita/day recommended by the World Health Organization.
Removal of COD from landfill leachate using Moringa oleifera
Authors: Salwa M Z M , Amirah A S N , Mahyun A W , Hassan Z , Mohamed Norsyazwani Che
Published: February 2021

Moringa oleifera was tested as a coagulant for its excellent coagulating properties in the treatment of water and wastewater. Moringa oleifera is a tropical plant belonging to the family of Moringaceae, besides being a non-toxic and natural organic polymer. The aim of this study is to investigate the removal of chemical oxygen demand (COD) from landfill leachate using Moringa oleifera through a coagulation-flocculation process. In this study, Moringa oleifera was used as a coagulant. Jar test experiments were employed in order to determine the optimum conditions of coagulant dosage and pH. The conditions of Moringa oleifera dosage of 20 mL and pH 2 were found to be optimal in the effective treatment of the landfill leachate. The study has proven that Moringa oleifera is a good natural coagulant for water treatment. Furthermore, only a small quantity of Moringa oleifera is required in treating a large amount of leachate.
Performance of rubber seed shell adsorbents for removal of methylene blue dye in aqueous solution
Authors: Chanderan Thevdarshni , Hasan Masitah , Mokhtar Zulfakar , Ibrahim Naimah
Published: February 2021

Regeneration of rubber seed shell (RSS) in producing an effective low-cost activated carbon (AC) through chemical activation using H3PO4. Adsorption of methylene blue (MB) by raw, AC1 (impregnation ratio 1:1) and AC2 (impregnation ratio 1:3) carbons were analyzed to discover its adsorption capacity. The effects of various experimental parameters: pH of solution, initial concentration, contact time and adsorbent dosage were analyzed. Characterization of adsorbents produced were performed using SEM, ash content, iodine number and BET. Overall performance of the adsorbents was investigated by employing the optimum values obtained in the batch adsorption studies. This study revealed that the carbon with higher impregnation ratio (AC2) has the highest removal efficiency of MB at 91.4%. Specific surface area, iodine adsorption number and ash content for AC2 are 317.6 m2/g, 676.9 mg/g and 2.6%, respectively. This study revealed the primacy of chemically activated carbons with higher impregnation ratio (AC2) for the removal of MB.
Investigation of light non-aqueous phase liquid penetration in double-porosity using physical experiment and computer simulation
Authors: Rashid M F Abd , Alias N , Ahmad K , Sa’Ari R , Tsai F T C , Ramli M Z , Ibrahim Z , Jumain M , Jamal M H , Bakar A Abu , Shahrin M I
Published: February 2021

Groundwater resources benefits to human activity for developing country. Groundwater contamination is crucial, particularly due to the amount of leakage and spillage of hydrocarbon liquids such as light non-aqueous phase liquids (LNAPLs), resulting in contaminated the groundwater and unsafe for domestic and agriculture activities. Penetration of hydrocarbon liquids into groundwater can be seen through double-porosity soil. Therefore, this paper investigates the penetration of LNAPLs in double-porosity soil using computer modelling to calibrate and validate from physical experiment data. These computer modelling and physical experiment studies discuss the pattern and rate of LNAPL penetrations by employing PetraSim commercial software and digital image processing technique (DIPT) by using acrylic glass cylinder, mirror and Nikon D90 digital camera. The LNAPL volume of 70 ml and 150 ml were poured instantaneously onto the surface of soil sample for calibration and validation purposes. The penetration pattern in double-porosity were monitored and recorded using digital camera at pre-determine time intervals. The images were processed using Surfer software and Matlab routine to plot the LNAPL penetration pattern. PetraSim simulation was used to calibrate and validate the penetration of LNAPL through double-porosity soil with physical experiment data. As a result, the PetraSim results valid with the physical experiment results. The Nash-Sutcliffe efficiency results more than 0.50 with percentage of differences for calibration and validation are 1.34% and 5.47% between physical experiment and PetraSim simulation. As a conclusion, PetraSim simulation can be used for further investigation on LNAPL penetration through subsurface soil.
A study on early detection of sewer pipeline blockage using CCD tomography approach
Authors: Jamaludin J , Rahim R A , Rahiman M H F , Ismail W Z W , Ismail I , Sahrim M , Balakrishnan S R , Raisin S N , Rahalim F M , Naeem B
Published: February 2021

In a sewage system, congealed mass is created by mixing non-biodegradable solid matter with fat, oil and grease. Congealed mass might cause a sewer blockage and overflow. This issue may impose a risk to public health and environment. It also leads to increased operational and maintenance costs of sewer system. A robust and durable sensor system are required to monitor the sewer network blockage which could cause a fluctuation in the data. CCD tomography approach will be used to detect the congealed mass forming in sewer network at early stage. The main concept of CCD tomography approach is to analyze the structure and composition of congealed mass by examining the light intensity after penetrated. Therefore, the location and size of the sewer blockage can be predicted. Light reflection from the congealed mass will strikes onto CCD surfaces. This light source will be converted into an electrical signal which is in voltage output value. Filtered images of Linear Back Projection (LBP) algorithm will be applied to reconstruct the image and identify the characteristic of congealed mass either fat, oil or grease. The location and the size of the congealed mass forming also can be identified using this CCD tomography approach.
Multilayer Perceptron Model for the prediction of corrosion rate of Aluminium Alloy 5083 in seawater via different training algorithms
Authors: Zulkifli F , Abdullah S , Suriani M J , Kamaludin M I A , Wan Nik W B
Published: February 2021

Corrosion inhibitor is often opted as a corrosion protection method for various industries worldwide. The development of eco-friendly corrosion inhibitor has become a trending concern due to the various environmental regulations impose by several countries. However, a laboratory testing would be such a tedious, costly and time-consuming process. Therefore, artificial neural network (ANN) has been used extensively to predict the verdict based on the experimental values. In this study, 3-layered Multilayer Perceptron (MLP) models were developed with 3 inputs (Electrochemical Impedance Spectroscopy, Ω.cm2), (Potentiodynamic polarization, A/cm2), (weight loss, %), and one output (corrosion rate, mm.yr−1). The data were divided into three parts; 70%, 15%, and 15% for model development, model validation and model testing, respectively. Three training algorithms were tested during the model development, including the Levenberg-Marquadt (LM), Bayesian Regularization (BR), and Scale Conjugate Gradient (SCG). Results revealed that the best MLP models during the development were using neuron number 4 (r = 0.99272), 6 (r = 0.99155), and 2 (r = 0.98624) for LM, BR and SCG, respectively. Among the three training algorithms, LM is opted as the best training algorithm for the corrosion rate prediction which executed high correlation coefficient (R) values during development (R = 0.99272), validation (R = 0.99905), and testing (R = 0.97908). These findings will be an essential tool for the model development with the sole purposes of predicting the corrosion rate in line to ensure the exact time for repair and maintenance schedule.