bluuebunny/crossref_metadata_2025 huggingface dataset:
Chaos in Cartan foliations
Authors: Bazaikin Yaroslav V. , Galaev Anton S. , Zhukova Nina I.
Published: October 2020

Chaotic foliations generalize Devaney’s concept of chaos for dynamical systems. The property of a foliation to be chaotic is transversal, i.e, depends on the structure of the leaf space of the foliation. The transversal structure of a Cartan foliation is modeled on a Cartan manifold. The problem of investigating chaotic Cartan foliations is reduced to the corresponding problem for their holonomy pseudogroups of local automorphisms of transversal Cartan manifolds. For a Cartan foliation of a wide class, this problem is reduced to the corresponding problem for its global holonomy group, which is a countable discrete subgroup of the Lie automorphism group of an associated simply connected Cartan manifold. Several types of Cartan foliations that cannot be chaotic are indicated. Examples of chaotic Cartan foliations are constructed.
Reset-voltage-dependent precise tuning operation of TiOx/Al2O3 memristive crossbar array
Authors: Kim Tae-Hyeon , Nili Hussein , Kim Min-Hwi , Min Kyung Kyu , Park Byung-Gook , Kim Hyungjin
Published: October 2020

In this Letter, we present reset-voltage-dependent precise tuning operation of TiOx/Al2O3-based memristive devices. For the high resistance state (HRS) with high reset voltage, abrupt set operations are observed with a large variation, while the HRS obtained by low reset voltage provides gradual and uniform switching behaviors. The improvement of gradual switching and the programming accuracy are analyzed regarding cycle-to-cycle as well as device-to-device variations. We believe that these results can be applied to operate TiOx/Al2O3-based memristors in areas requiring highly accurate tuning characteristics.
Spontaneous transitions to focal-onset epileptic seizures: A dynamical study
Authors: Zhang Liyuan , Wang Qingyun , Baier Gerold
Published: October 2020

Given the complex temporal evolution of epileptic seizures, understanding their dynamic nature might be beneficial for clinical diagnosis and treatment. Yet, the mechanisms behind, for instance, the onset of seizures are still unknown. According to an existing classification, two basic types of dynamic onset patterns plus a number of more complex onset waveforms can be distinguished. Here, we introduce a basic three-variable model with two time scales to study potential mechanisms of spontaneous seizure onset. We expand the model to demonstrate how coupling of oscillators leads to more complex seizure onset waveforms. Finally, we test the response to pulse perturbation as a potential biomarker of interictal changes.
Deep donor behavior of iron in β-Ga2O3 crystals: Establishing the Fe4+/3+ level
Authors: Gustafson T. D. , Lenyk C. A. , Halliburton L. E. , Giles N. C.
Published: October 2020

The Fe4+/3+ donor level is experimentally determined to be 0.70 eV (±0.05 eV) above the valence band maximum in β-Ga2O3. Electron paramagnetic resonance (EPR) is used to monitor Fe3+ ions that are unintentionally present in an Mg-doped β-Ga2O3 crystal (with a low Fermi level). For temperatures near 255 K, exposure to 325 nm laser light converts a portion of the Fe3+ ions to Fe4+ and Fe2+ ions and, at the same time, forms neutral magnesium acceptors (MgGa0) and neutral Ir donors (Ir3+). After removing the light, the intensity of the Fe3+ EPR spectrum has a significant additional decrease as holes thermally released to the valence band from rapidly decaying neutral Mg acceptors are trapped at Fe3+ ions and form even more Fe4+ ions. This demonstrates that the Mg0/− acceptor level, near 0.65 eV, is closer to the valence band than the Fe4+/3+ level. Following the fast initial post-light decrease, the Fe3+ spectrum then slowly recovers as Fe4+ ions are destroyed by electrons thermally excited from the valence band. An activation energy for the thermal decay of the Fe4+ donors, and thus a value for the Fe4+/3+ level, is obtained from the analysis of five Fe3+ isothermal recovery curves taken from the Mg-doped crystal between 250 and 270 K. A first-order kinetics model is used, as minimal retrapping is observed. In separate experiments, EPR shows that Fe4+ ions are also produced in an Fe-doped β-Ga2O3 crystal (without Mg acceptors) during exposures to laser light at temperatures near 255 K.
Multiparametric study of tearing modes in thin current sheets
Authors: Betar H. , Del Sarto D. , Ottaviani M. , Ghizzo A.
Published: October 2020

We investigate the asymptotic scaling of the growth rate and of the characteristic layer width of reduced-MHD tearing modes occurring in thin current sheets when reconnection depends on two non-ideal parameters. For this purpose, we use a new multi-precision finite difference eigensolver. The viscous-resistive regime, the warm-resistive regime that includes both resistivity and electron temperature effects, the warm-inertial regime in which a finite electron inertia replaces resistivity in allowing reconnection, and the inertial-resistive regime that includes both electron inertia and resistivity are investigated. Previous analytical results of the first three regimes are recovered. For all regimes, the scalings of the width of the reconnecting layer are provided in the different limits of the wavelength spectrum, and general estimates for the fastest growing modes are obtained and generalized to different magnetic equilibria. Implications for the disruption of evolving current sheets are discussed.
Nanotip response to monocycle terahertz pulses
Authors: Houard J. , Arnoldi L. , Ayoub A. , Hideur A. , Vella A.
Published: October 2020

The interaction of monocycle terahertz (THz) fields with metal nanostructures such as nanotips is attracting a lot of interest for the development of new applications such as THz-scanning tunneling microscopy and ultra-fast field emission. New methods have been introduced to measure the enhanced THz near field waveform in the vicinity of a nanotip surface. Here, we present results obtained by electron field emission in the multiphoton emission regime. The nanotip mimics the behavior of an antenna with a simplified equivalent circuit. We show that the electrical characteristics can be calculated using the nanowire geometry approximation and taking into account a conduction shell with a thickness smaller than the material skin depth. The results introduce a method to predict the antenna response of the nanotip and thus the near THz field waveform.
Effects of perturbation order and basis set on alchemical predictions
Authors: Domenichini Giorgio , von Rudorff Guido Falk , von Lilienfeld O. Anatole
Published: October 2020

Alchemical perturbation density functional theory has been shown to be an efficient and computationally inexpensive way to explore chemical compound space. We investigate approximations made, in terms of atomic basis sets and the perturbation order, introduce an electron-density based estimate of errors of the alchemical prediction, and propose a correction for effects due to basis set incompleteness. Our numerical analysis of potential energy estimates, and resulting binding curves, is based on coupled-cluster single double (CCSD) reference results and is limited to all neutral diatomics with 14 electrons (AlH⋯NN). The method predicts binding energy, equilibrium distance, and vibrational frequencies of neighboring out-of-sample diatomics with near CCSD quality using perturbations up to the fifth order. We also discuss simultaneous alchemical mutations at multiple sites in benzene.
Theoretical investigation of non-Förster exciton transfer mechanisms in perylene diimide donor, phenylene bridge, and terrylene diimide acceptor systems
Authors: Yang Lei , Jang Seogjoo J.
Published: October 2020

The rates of exciton transfer within dyads of perylene diimide and terrylene diimide connected by oligophenylene bridge units have been shown to deviate significantly from those of Förster’s resonance energy transfer theory, according to single molecule spectroscopy experiments. The present work provides a detailed computational and theoretical study investigating the source of such a discrepancy. Electronic spectroscopy data are calculated by time-dependent density functional theory and then compared with experimental results. Electronic couplings between the exciton donor and the acceptor are estimated based on both the transition density cube method and transition dipole approximation. These results confirm that the delocalization of the exciton to the bridge parts contributes to significant enhancement of donor–acceptor electronic coupling. Mechanistic details of exciton transfer are examined by estimating the contributions of the bridge electronic states, vibrational modes of the dyads commonly coupled to both donor and acceptor, inelastic resonance energy transfer mechanism, and dark exciton states. These analyses suggest that the contribution of common vibrational modes serves as the main source of deviation from Förster’s spectral overlap expression.
Amplifying photocurrent of graphene on GeSn film by sandwiching a thin oxide between them
Authors: Lv Yanhui , Li Hui , Lee Kuo-Chih , Chang Guo-En , Shieh Tung-Ho , Wu Xiao-Shan , Chang Ching-Ray , Wu Han-Chun , Hung Kuan-Ming. , Cheng Hung-Hsiang
Published: October 2020

We report an investigation of the photoresponse of a GeSn film with a graphene layer placed on top and a thin GeO2 layer sandwiched between them. Both wavelength- and power-dependent amplification of the photocurrent are demonstrated. These results are associated with the spatial separation of photoexcited electrons and holes enabled by the thin oxide layer, where electrons and holes accumulate in graphene and the GeSn film, respectively. This spatial separation of negative and positive charges generates a mutual gating that increases the number of carriers in both layers, yielding the amplification observed in the measurement. A quantitative method based on an equivalent circuit model is provided, and the numerical results agree well with the experimental data. Our results represent an advance toward the realization of high-performance heterostructured photodetectors, and the modeling provides a framework for analyzing the photodetection capability of other two-dimensional materials on semiconductor films.
Modulators for mid-infrared and terahertz light
Authors: Herrmann Eric , Gao Hua , Huang Zhixiang , Sitaram Sai Rahul , Ma Ke , Wang Xi
Published: October 2020

The rise of mid-infrared and terahertz wave technology over the past two decades has led to incredible insights and potential applications for next-generation optoelectronics. Modulators, which control amplitude, phase, and/or polarization of incident light, are widely used in communications, imaging, and sensing and are crucial for further development of technology functioning in the mid-infrared and terahertz frequency regimes. The lack of natural materials with optical responses in these frequency regimes has led to a surge in engineering efforts to create novel devices and architectures for achieving control over the properties of mid-infrared and terahertz radiation. Major efforts in the field have been devoted to studying carrier concentration modulation, liquid crystals, phase-change materials, and micro-electromechanical systems for controlling the light–matter interaction. Although there has been considerable progress in realizing mid-infrared and terahertz modulators, novel approaches are seeking higher modulation speed, more functionality, and miniaturized size. In this perspective, we review the recent advancements of modulators for mid-infrared and terahertz wavelengths. We discuss various modulation mechanisms, along with their relative performance, and consider future architectures to improve upon the current technology for mid-infrared and terahertz modulation.
Space charge profile study of AlGaN-based p-type distributed polarization doped claddings without impurity doping for UV-C laser diodes
Authors: Zhang Ziyi , Kushimoto Maki , Horita Masahiro , Sugiyama Naoharu , Schowalter Leo J. , Sasaoka Chiaki , Amano Hiroshi
Published: October 2020

The space charge density profile of the nondoped AlGaN-based p-type cladding layer for UV-C laser diodes realized by distributed polarization doping is examined theoretically and experimentally. The analysis of the capacitance-voltage measurement revealed that the average effective acceptor density of 4.2 × 1017 cm–3 is achieved even without impurity doping, and it is in good agreement with the theoretical prediction from the measured Al composition profile. This result suggests that the cladding layer is ideal for UV-C LDs because it provides sufficient hole injection while potentially avoiding internal losses due to impurity doping.
Epitaxial growth of
β
-Ga2O3 on (110) substrate by plasma-assisted molecular beam epitaxy
Authors: Itoh Takeki , Mauze Akhil , Zhang Yuewei , Speck James S.
Published: October 2020

Epitaxial growth of β-Ga2O3 films on (110) substrates has been performed via plasma-assisted molecular beam epitaxy (PAMBE). The atomic force microscopy scan shows a very low root mean square roughness of 0.08 nm for the surface of the as-received (110) substrates. High-resolution x-ray diffraction measurements reveal a 2.5 nm/min growth rate of β-Ga2O3 films on (110) substrates for conventional PAMBE growth conditions (∼700 °C), which is comparable to that on (010) substrates. The surface morphology of β-Ga2O3 epitaxial films is smooth and has a similar dependence on Ga flux to (010) growth. However, the (110) plane does not have a tendency to show a well-defined step–terrace structure in spite of the appearance of (110) facets in the growth of (010) β-Ga2O3. Indium catalyzed growth was also demonstrated to improve the growth rate up to 4.5 nm/min and increase the maximum growth temperature up to 900 °C of (110) β-Ga2O3.
Importance of sugarcane straw maintenance to prevent soil organic matter depletion in a Nitisol in the central-southern region of Brazil
Authors: Popin Gustavo V. , Santos Arthur K. B. , Melo Paul L. A. , Cherubin Maurício R. , Cerri Carlos E. P. , Siqueira-Neto Marcos
Published: October 2020

Sugarcane straw is a potential feedstock to increase bioenergy production. However, leaving straw on the soil surface is important to sustaining soil organic matter (SOM). We conducted a field experiment to evaluate the impacts of two years of straw removal on SOM in a sugarcane area – on an Eutric Nitisol in south-eastern Brazil – with low straw production (7 Mg ha–1). The experiment was a randomised complete block design (four blocks) with four rates of straw removal: (i) no removal, (ii) medium removal, (iii) high removal and (iv) total removal. We evaluated straw decomposition, soil carbon (C) and nitrogen (N) stock (0–30 cm), labile C, and microbial biomass C and N (0–10 cm). Increases in the straw removal rates reduced decomposition, with 30–42% of the initial straw amount remaining on the soil after one year (first year) and 33–38% remaining at the end of the second year. During the first year, no effect was found on soil C (8 kg m–2) and N (0.7 kg m–2) stocks; however, during the second year, total straw removal reduced soil C stock by 10% (0–30 cm) compared with no straw removal. Straw removal rates negatively affected the labile C (6–10% and 20–25%, first and second year respectively) and microbial C (correspondingly 10–15% and 21–27%). Microbial N was not altered in the first year, but decreased 26% due to straw maintenance (no removal) during the second year. Total straw removal decreased the C management index (CMI) by 15% (first year) compared with no straw removal. However, during the second year, all rates of straw removal decreased the CMI: by 15% for medium, 22% for high and 26% for total removal. Our findings indicate that any straw removal in areas with low straw production negatively affects SOM, initially through reduction in labile C pools. Although slight impacts on soil C and N stock were detected, reduction in straw-derived inputs stimulates microbial utilisation of soil C pools, and consequently reduces SOM over time.
Firesetting among People with Mental Disorders: Differences in Diagnosis, Motives and Behaviour
Authors: Nanayakkara Vindya , Ogloff James R. P. , McEwan Troy E. , Ducat Lauren
Published: October 2020

Despite the prevalence of mental disorder among firesetters, there is limited empirical research on how firesetting manifests in people with different psychiatric conditions. In this study, classification methodology was used to explore different types of firesetting committed by people with mental disorders. Associations between motives, diagnoses, situational, and behavioral variables were also observed to clarify the nexus between mental disorder and firesetting. A sample of 103 mentally disordered firesetters referred to community-based forensic mental health services was used. Four types of firesetting perpetrated by people with mental disorders were differentiated using multidimensional scaling: (1) Psychotic Struggle, (2) Hopeless, (3) Dysregulated, and (4) Fire Interest. In the first two types of firesetting, motives of revenge and suicide were mainly derived from psychotic symptoms and a more direct relationship between psychosis and firesetting was observed. Conversely, the latter two types featured motives of express frustration and excitement seeking, in association with personality disorder and pyromania, respectively. These types indicated pathways to firesetting wherein the corresponding mental disorder appeared to exacerbate predisposing vulnerabilities for firesetting. The implications for clinical formulation and theory development are discussed, emphasizing the need to better understand the etiology of firesetting including the underlying motives, psychopathology and context.
Asymptotic behavior of correlation functions of one-dimensional polar-molecules on optical lattices
Authors: De Silva Theja N
Published: October 2020

We combine a slave-spin approach with a mean-field theory to develop an approximate theoretical scheme to study the density, spin, and, pairing correlation functions of fermionic polar molecules. We model the polar molecules subjected to a one-dimensional periodic optical lattice potential using a generalized t–J model, where the long-range part of the interaction is included through the exchange interaction parameter. For this model, we derive a set of self-consistent equations for the correlation functions, and evaluate them numerically for the long-distance behavior. We find that the pairing correlations are related to spin correlations through the density and the slave-spin correlations. Further, our calculations indicates that the long-range character of the interaction can be probed through these correlation functions. In the absence of exact solutions for the one-dimensional t–J model, our approximate theoretical treatment can be treated as a useful tool to study one dimensional long-range correlated fermions.
New investigation of the electron-impact ionization of the intermediate valence state of ammonia
Authors: El Mir R , Kaja K , Naja A , Staicu Casagrande E M , Houamer S , Dal Cappello C
Published: October 2020

We report on the measurement of the triply differential cross-section for electron-impact ionization of the valence 1e orbitals of ammonia using the (e, 2e) technique with coplanar asymmetric kinematics. The experimental results are first compared to the theoretical cross sections calculated using the 1CW, 1DW and the BBK models recently extended to molecules. We then introduce the short-range (SR) potential of interaction between the incident electron and the target into these models. The experimental data are thus compared to the newly developed extended models 1CWSR, 1DWSR and BBKSR. We show that the introduction of the SR potential improves the visibility of the recoil region.
Ultralight plat-type vibration damper with designable working bandwidth and strong multi-peak suppression performance
Authors: Ma Fuyin , Cai Yongqing , Wu Jiu Hui
Published: October 2020

This paper proposed a low-frequency vibration damping method which attaches some ultralight locally resonant plate-type units onto the vibration structure as dampers. Owing to the designable band gap property of the units, the structural vibration in the pre-defined band gap range is localized and consumed by the dampers, thereby realizing a vibration damping effect. This damping method achieved vibration attenuation via the band gap characteristics of the local resonance unit, while the band gap properties operated in a frequency band with a certain width, so the vibration within the band gap range could be attenuated effectively. Moreover, as the frequency range, bandwidth and polarization direction of the band gap are tunable by adjusting the configuration and parameters of the unit cell, this vibration damping method shows flexible design potential. The advantage of this damping method was that, in addition to a considerable working bandwidth and convenient designable working frequency range, the additional mass was minimal and negligible. The total weight of the damper could reach levels as low as 0.3‰ of the objective vibration structure, displaying no evident increase in the overall weight. Moreover, even if only a single cell was used, a good damping effect with strong multi-peak suppression performance could be obtained. Compared with conventional methods, this damping method reduced the amplitude of the vibration peak of the original structure but did not generate additional vibration peaks on either side of the reduced peak like previous vibration absorbers. In addition, due to the fact that the configuration of the damper unit can be easily and flexibly designed according to actual application requirements, it has a wide range of engineering applications including but not limiting to aircraft, land-based vehicles, modern industrial equipment, precision instruments and household appliances.
Driving frequency effect on discharge parameters and higher harmonic generation in capacitive discharges at constant power densities
Authors: Sharma Sarveshwar , Sirse Nishant , Kuley Animesh , Sen Abhijit , Turner Miles M
Published: October 2020

Very high frequency (VHF) driven capacitive discharges are now being increasingly adopted for plasma-based materials processing due to their high processing rates and lower substrate damage. Past studies related to complex plasma dynamics and higher harmonics generation in such systems were limited to constant voltage/current conditions, whereas, industrial systems are mostly driven by constant power density sources. In the present study, using particle-in-cell (PIC) simulation, we explore the dynamics of collisionless symmetric capacitive discharges that is operated at constant power densities. Our focus is on the effect of the driving frequency on the discharge parameters like the electron density/temperature, the electron energy distribution function (EEDF), the ion energy distribution function (IEDF), and the generation of higher harmonics in the device. The simulations are performed for a driving frequency from 27.12 to 100 MHz in argon plasma at a gas pressure of 1 Pa and for two values of the power density, namely, 2 kW m−3 and 20 kW m−3. It is observed that the required discharge voltage for maintaining constant power density decreases and discharge current increases with an increase in the driving frequency. A transition frequency is observed at both power densities. The density decreases (electron temperature increases) before the transition frequency and the trend is reversed after crossing the transition frequency. The EEDF shows an enhancement in the population of the mid-energy range of electrons as the driving frequency increases up to the transition frequency thereby changing the shape of EEDF from bi-Maxwellian to nearly Maxwellian, and then transforms into a nearly bi-Maxwellian at higher driving frequencies. The IEDF at the electrode surface shows bimodal behaviour at a lower driving frequency, becoming more pronounced at a power density of 20 kW m−3, and then turning into a single energy peak. The corresponding maximum ion energy is found to decrease with driving frequency.
Inhomogeneous superconductivity and quasilinear magnetoresistance at amorphous LaTiO3/SrTiO3 interfaces
Authors: Lebedev N , Stehno M , Rana A , Gauquelin N , Verbeeck J , Brinkman A , Aarts J
Published: October 2020

We have studied the transport properties of LaTiO3/SrTiO3 (LTO/STO) heterostructures. In spite of 2D growth observed in reflection high energy electron diffraction, transmission electron microscopy images revealed that the samples tend to amorphize. Still, we observe that the structures are conducting, and some of them exhibit high conductance and/or superconductivity. We established that conductivity arises mainly on the STO side of the interface, and shows all the signs of the two-dimensional electron gas usually observed at interfaces between STO and LTO or LaAlO3, including the presence of two electron bands and tunability with a gate voltage. Analysis of magnetoresistance (MR) and superconductivity indicates the presence of spatial fluctuations of the electronic properties in our samples. That can explain the observed quasilinear out-of-plane MR, as well as various features of the in-plane MR and the observed superconductivity.
A new approach to achieving strong ferroelectric properties in TiN/Hf0.5Zr0.5O2/TiN devices
Authors: Kim Hyungwoo , Kashir Alireza , Oh Seungyeol , Hwang Hyunsang
Published: October 2020

In this paper, we propose a method to improve the performance of TiN/Hf0.5Zr0.5O2 (HZO)/TiN Nano-capacitors used in memory devices. Instead of direct fabrication of the TiN/HZO/TiN device, our method involves an intermediate step in which W metal is used as a capping material to induce a large in-plane tensile strain during rapid thermal annealing, resulting in a total suppression of the monoclinic phase and the appearance of the ferroelectric phase. Consequently, after removing the W capping electrode through an etching process and the post-deposition of a TiN top electrode at room temperature, a high remnant polarization of approximately 40 μC cm−2 and a 65% increase of coercive field were obtained. Moreover, the leakage current was reduced by an order of magnitude compared to the normal TiN/HZO/TiN capacitor; this result is attributed to the presence (absence) of the W/HZO (TiN/HZO) top interface during thermal annealing. The formation of a TiO
x
interfacial layer at elevated temperatures, which pulls oxygen from the HZO layer, resulting in the formation of oxygen vacancies, is the main cause of the high leakage current through the TiN/HZO/TiN stacks. It was confirmed that the re-capped TiN/HZO/TiN capacitor has a comparable endurance to a normal capacitor. Our results offer the re-capping process as a promising approach to fabricating HfO2-based ferroelectric memory devices with various electrode materials.
Generative adversarial network-based sinogram super-resolution for computed tomography imaging
Authors: Tang Chao , Zhang Wenkun , Wang Linyuan , Cai Ailong , Liang Ningning , Li Lei , Yan Bin
Published: October 2020

Compared with the conventional 1×1 acquisition mode of projection in computed tomography (CT) image reconstruction, the 2×2 acquisition mode improves the collection efficiency of the projection and reduces the x-ray exposure time. However, the collected projection based on the 2×2 acquisition mode has low resolution (LR) and the reconstructed image quality is poor, thus limiting the use of this mode in CT imaging systems. In this study, a novel sinogram-super-resolution (SR) generative adversarial network model is proposed to obtain high-resolution (HR) sinograms from LR sinograms, thereby improving the reconstruction image quality under the 2×2 acquisition mode. The proposed generator is based on the residual network for LR sinogram feature extraction and SR sinogram generation. A relativistic discriminator is designed to render the network capable of obtaining more realistic SR sinograms. Moreover, we combine the cycle consistency loss, sinogram domain loss, and reconstruction image domain loss in the total loss function to supervise SR sinogram generation. Then, a trained model can be obtained by inputting the paired LR/HR sinograms into the network. Finally, the classic filtered-back-projection reconstruction algorithm is used for CT image reconstruction based on the generated SR sinogram. The qualitative and quantitative results of evaluations on digital and real data illustrate that the proposed model not only obtains clean SR sinograms from noisy LR sinograms but also outperforms its counterparts.
High-strength steel frames with SMA connections in self-centring energy-dissipation bays: insights and a multimodal nonlinear static procedure
Authors: Ke Ke , Yam Michael C H , Zhang Huanyang , Lam Angus C C , Zhou Xuhong
Published: October 2020

This study explores the effectiveness of shape-memory-alloy (SMA)-based self-centring energy-dissipation bays (SCEDBs) for enhancing the seismic performance of high-strength-steel (HSS) frames. The work commences with the development of an ensemble of prototype HSS frames equipped with SCEDBs, known as HSSF-SCEDB structures. The prototype systems are examined using cyclic-pushover and nonlinear-response-history analyses (NL-RHAs). According to the analysis database, it is found that the cyclic-pushover responses generally show a typical flag shape over a wide deformation range and that the post-earthquake residual deformations are below 0.5%, even following maximum interstorey drifts beyond the codified deformation threshold (i.e. 2%). To offer a practical tool to engineers for damage-control behaviour evaluation and seismic demand estimation, we develop a multimodal nonlinear static procedure based on a modified energy-balance concept. Conventional procedures relating to the fundamental vibration mode are also revisited. The results indicate that a medium-rise HSSF-SCEDB may be appreciably influenced by higher vibration modes. The difference between the average maximum interstorey drifts calculated by NL-RHAs and those obtained using the proposed procedure for an ensemble of earthquake motions is generally below 5%, and the adequacy of the proposed method is confirmed.
A novel passive adaptive magnetorheological energy absorber
Authors: Xi Jun , Dong Xiaomin , Li Wenfeng , Wang Tao , Song Xianyu , Zhang Zhiyuan
Published: October 2020

For traditional magnetorheological (MR) shock absorbers, the damping force is proportional to the square of the impact velocity. The instantaneous peak value of the damping force can easily cause damage to the load structure or human body, which will reduce the buffering efficiency. The viscous damping force is significantly affected by the size of the gap. Therefore, by changing the flow gap under different buffer strokes by presetting, the damping force can be maintained at a constant output in the full piston stroke, thereby improving the buffer efficiency. That is, a large gap is used at high speed and a small gap is used at low speed. The increase of the magnetic damping force at a small gap is applied to compensate for the decrease of the viscous force at low speed. Only constant current needs to be applied during buffering, which can greatly reduce costs. Based on this idea, a novel MR damper based on axial variable damping gap (MRD-VDG) is proposed. The MRD-VDG design method for the constant value output of the damping force in the full piston stroke is discussed and applied. According to the different requirements of the damping force under different piston displacements, the damping gap of different axial position are preset to realize the constant value output of the damping force during the stroke. The damping force under different damping gaps is analytically derived according to the Bingham-plastic nonlinear flow model with minor losses. Combining with the finite element analysis to obtain magnetic fields at different damping gaps between piston and cylinder. To validate the performance of the proposed design method, the prototype of MRD-VDG is fabricated. Damping characteristic test and impact test are performed to measure the damping characteristics of the MRD-VDG under different excited conditions. The results show that the piston displacement history of the damping force in the experiment is agreed well with the displacement history of the desired F-S curve under the assumed speed. The buffer efficiency of the prototype under designed conditions (the ratio of the corrected theoretical constant damping force to the actual peak damping force) exceeds 90%. This demonstrates the effectiveness of the MRD-VDG design. This design method has significant application prospects under impact condition without complex control (such as gun buffer, landing buffer, etc.)
Non-destructive detection of two cucumber cultivars fruit quality using NIR Spectroscopy
Authors: Kusumiyati  , Hamdani J S , Sutari W , Mubarok S , Kurniasari I
Published: October 2020

Cucumber fruit quality can be detected by the non-destructive method such as NIR Spectroscopy. NIR determines the content quality of the product rapidly, precise, and accurate. This study aims to predict the quality component of cucumber cultivars Bandana and Wulan by a non-destructive method using portable NIR. The experiment was conducted at Post Harvest Laboratory of Agriculture Faculty of Padjadjaran University and the instrument used to measure the fruit quality in a non-destructive way was the NIR (NirVana AG410, Integrated Spectronics Pty, Ltd, Australia). To determine cucumber internal quality it was done from the evaluations obtained by a non-destructive method (NIR) and a destructive method. The calibration and validation models are built using the partial least squares (PLS) method. The result shows that the quality component of the non-destructive cucumber method using NIR has accuracy values similar to the conventional method. In the observed result quality component, the correlation coefficient (R) was close to 1.00 and the standard error of calibration (SEC) was low or close to 0.00.
Utilization of selected microorganisms in enhancing the growth of selected plant in ex gold mining soil
Authors: Widiastuti H , Wulandari D , Zarate J
Published: October 2020

Gold mining is an essential economic booster in enhancing the foreign exchange of a country. However, the gold mining activities resulting in contaminated soil. Phytoremediation, using plants for environmental remediation, has been intensively investigated in last decade. Phytoremediation has fewer side effects than conventional physical and chemical methods. This remediation technique embraces an array of low-cost plant-based technologies that could be potentially advantageous for remediation of the former gold mining site. This research aimed to assess the potency of selected microorganisms to support the growth of the plant in the soil of the former gold mining area. The application of selected microorganisms of P solubilizer, N fixing, growth-promoting bacteria, and arbuscular mycorrhizal fungi showed the best result on yield. This study showed that sengon (Falcataria) yields the better one compared to that of sorghum both in a medium consisting of ex gold mining soil and compost and medium with the composition of the soil, compost, and zeolite. It can thus be concluded that sengon inoculated with selected microbe is a potential method for remediating ex gold mining area.
Farmers’ resilience towards land use change case study in Padang City, West Sumatra, Indonesia)
Authors: Mutiara VI , Febriamansyah R , Hariance R , Utami A S
Published: October 2020

Farmers in Padang City, West Sumatra Province, Indonesia face a dilemma of choices to change in land use due to urban development and population growth in the city. However, some farmers still survive and keep their land for agricultural farming purposes. This research aims to analyze farmers’ resilience factors for coping and adaptation towards land us change. This study used a survey method and selected; 3 sub-districts in Padang Cityhave the largest irrigated agriculture land area and have a tendency of high land conversion. One hundred and two rice farmers were selected as respondents with a criterion of having land close to the main road access, arterial roads, and residential roads and in an area with a high land convention tendency. Primary data were collected using a structured questionnaire, which then analyzed using descriptive qualitative analysis. The results show that internal factors and external factorsinternal factors influenced farmers’ resilience and external factors influenced farmers’ resilience, internal factors and external factors influenced farmers’ re-silience, internal factors, and external factors influenced farmers’ resilience. Internal factors include land ownership, farm income, farming experience, and the nature of farming activity where farming is a transfer of strong knowledge and understanding between parents and their children in farming, thus strengthening farmers to continue their farming. The external factor that affects farmers to survive is the ownership system of communal land (ulayat land) as a Minangkabau cultural heritage. This forces farmers to keep working on their land. By considering these factors, the government policy should be concerned about the social system in Minangkabau society as a baseline policy to maintain agricultural land.
Competitive analysis of crude palm oil (CPO) in West Sumatera Province to other provinces in Sumatera Island in domestic market
Authors: Nesti L , Tan F , Hadiguna R A
Published: October 2020

The agricultural sector in Indonesia, especially Crude Palm Oil (CPO) has contributed the country’s foreign exchange with the value of CPO exports in 2016 amounting to the US $ 17.8 billion, up 8 per cent compared to the previous year of US $ IG.5 billion. This has led Indonesia to become the largest producer and exporter of palm oil until now. Six provinces became the largest production centre of palm oil in Indonesia, but West Sumatera Province has not been included in the big six. West Sumatera Province, which is still dominated by an agriculture sector, and or plantation sub-sector has contributed 6.57%. The purpose of this research is to analyze the competitiveness of CPO export of five provinces located in Sumatra Island in a domestic market and compare it with C PO competitiveness in West Sumatera Province with time-series data from 2000-2016 using RCA (Revealed Comparative Advantage) Index. The results show that on average the RCA value produced by RCA > 1 is only South Sumatera province with RCA < 1 if each year the analysis of each Province shows fluctuating RCA values that lend to show a decline. Except for the value of RCA Provinces West Sumatera showed on the increase. One of the causes of the declining RCA values is that each Province has started to focus on the development of downstream CPO products so that the CPO that was once more exported overseas has gradually started to reduce exports and more to meet domestic demand as raw materials CPO downstream products such as the manufacture of food and non-food products. Meanwhile, CPO in West Sumatera Province is still dominated by foreign exports compared to downstream development.
The ability of selected indigenous cyanobacteria isolates of West Sumatra to control Fusarium oxysporum f. sp. capsici on chili
Authors: Yanti Y , Hamid H , Syarif Z
Published: October 2020

The cyanobacteria provide a promising inoculant alternative for enhancement the growth, nitrogen fixation and yields. Our Previous study had screened the best cyanobacteria isolates, which has potential as a plant growth promoter. However, the ability of the cyanobacteria strain to control Fusarium wilt disease is not yet identified. This research aimed to screen the best cyanobacteria strains isolated from chili rhizosphere as growth promotor and biocontrol agents for fusarium wilt on chili. Cyanobacteria multiplied with common methods using BG-11 medium ( room temperature, 12/12 h L/D cycle). All strains showed ability as growth promotor and increase yields. All isolates also showed suppression of disease development caused by Fusarium oxysporum f.sp. capsici (Foc). All the five strains that are known for their ability to control R. syzygii subsp. indonesiensis were also had the best ability to promote growth and increase resistance to Foc.
Bibliometric analysis of traceability in agri-food research
Authors: Hisjam M , Sartika V , Priyandari Y , Sutopo W
Published: October 2020

Traceability in agri-food has become an important aspect of consumer awareness that demand foods that are available, in good quality, healthy, and traceable in handling processes. This field has also become the focus of the study among the related scientists. We used bibliometric analysis to review the published traceability of agri-food papers. The analysis using a query from the Scopus website to see the importance of this field to research. Our web search covers publication from 1998 to 2018, and we found 67 articles published on this query, and 31 papers include the query using the keyword ‘food safety’. The authors of these articles are mostly from developed countries. Although somewhat fluctuated, the number of documents tends to increase with time to indicate that this field is growing.
Realtime measurement of human labor energy for primary tillage operation in paddy cultivation
Authors: Putri RE , Lubis MIA , Hasan A , Santosa  , Arlius F
Published: October 2020

Human labor energy still provides a large and dominant contribution in rice cultivation in Indonesia. This study is specified to determine human energy needed for primary tillage operation in paddy cultivation practices in Padang Pariaman, West Sumatera Indonesia. The objectives of this research are to analyze human energy expenditure for primary tillage operation and to compare between real-time measurement and conversion factor of energy. The data were collected with three different plot areas with average size 30 m × 25 m. The analysis of human energy consumption conducted by two methods (predicted energy using conversion factor value of energy and real-time energy using Garmin Forerunner 35). The result shows that the real-time measurements of labor energy expenditure for primary tillage operation were 17.7291, 19.2857, and 12.2483 MJ/ha, respectively. However, the labor energy defined by the conversion factor were 13.3568, 14.0141 and 12.7498 MJ/ha, respectively. Thus, tillage operation with average heart beat rate was 127 bpm, it could be categorized as heavy work. This information is needed as a basis to improve and recommend designing of agricultural equipment and machinery, and also tools to reduce the use of labor energy.
Hedonic Test of Kombucha Coffee
Authors: Nana Kusdiana Raden , Ferdi Vinsensius , Kusumawardhana Indra , Levyta Farah
Published: October 2020

Kombucha is a fermented drink that has a health benefit. Originally, kombucha made from a combination of sweetened tea that mixed with a symbiotic culture of bacteria and yeast to ferment. Moreover, the making of kombucha starts to vary through an infusion method such as herbs infusion, flowers or fruits, and vegetable mixture, and even to substitute with the coffee ground. Indonesia is the fifth largest consumer of coffee in the world. Therefore, this article aims to study an upcycling of leftover coffee grounds to produce kombucha. This form of fermentation method with inoculum Kombucha tea, which then known as Kombucha coffee (KC). The empiric study was conducted using a quantitative method, where a secondary data was supported with the primary result of questionnaires to eighty panelists. The findings of this research suggested that the aroma and taste of KC widely accept by the respondents. Additionally, KC’s aroma, taste, and texture proved more hedonic value than tea kombucha. Although the study has a limitation such as time and the number of respondents. But, the result of the study stimulates a further discussion to investigate the significance of KC towards business and economic benefits.
Effects of Pouring Temperature Variations on Fatigue Properties of Al-Cu Alloy After Remelting
Authors: Muhammad Sadida Hizba , Tri Iswanto Priyo
Published: October 2020

The aim of this research is to observe the casting temperature variations effects on fatigue properties of Al 2024 with different types of casting temperature. Three different pouring temperatures were carried out 688, 738, 788 °C, and the cast mold was preheated and kept constant at 220°C. The speciment was heat-treated by T6 process in which this method was heat treated in electrical furnace at 500 °C for 2 hours continued by fast quenching into water. Finally, the sample cast was treated by artificial aging method with the temperature at 190 °C. The results show that at 688°C pouring temperature, it has the highest tensile test results than to other variations which is 138.37 MPa, and for the fatigue strength at more than 2x106 cycles is 62.3 MPa. It shows that fatigue life of aluminum alloy 2024 could be improved by T6 heat treatment and artificial aging in which it indicates that the number of the fatigue strength depends on the number of the maximum tensile strength of the material because the increase in the maximum tensile strength will increase the fatigue strength.
Shape Modification of Manganese Oxide Prepared by Solvothermal: Effect of Precipitation Agent
Authors: Kusumaningrum Retno , De Yesu Prisila Abi Faustina , Sukmarani Galuh , Muhammad Habieb Alvin , Fauzi Fiqhi , Bambang Widayatno Wahyu , Sukarto Wismogroho Agus , Ikhlasul Amal Muhamad , Taufiqu Rochman Nurul , Noviyanto Alfian
Published: October 2020

Nano-sized manganese oxide was synthesized by the solvothermal method. Manganese sulfate was used as a precursor, which is obtained from the Sumbawa manganese ore. Two kinds of the precipitating agent, ammonium persulfate and sodium hydroxide, were used in this study and the effect on the solvothermal product were examined thoroughly. The solvothermal temperature and time were 120°C for 18 hours, respectively, for both precipitating agents. The results showed that the phase of manganese oxide was influenced by the precipitating agent, as indicated by X-ray diffraction analysis. Phase <x-MnO2 was obtained from the reaction between MnSO4 and ammonium persulfate, while Mn3O4 for the sodium hydroxide. The formation of a-MnO2 was influenced by the excess of NH4
+ which came from the manganese ore leaching into MnSO4. One notable finding in this study is that the morphology of manganese oxide was also affected by the precipitating agent. For instance, the shape of MnO2 and Mn3O4 was needle and sphere, respectively. Moreover, the strict long thinner needle of <x-MnO2 was formed and the aspect ratio increased at a higher temperature. While the particle size of Mn3O4 decreased with the increased temperature. These results imply that variation of a precipitating agent is imperative to obtain the specific manganese oxide product, including the shape.