bluuebunny/crossref_metadata_2025 huggingface dataset:
Clustering of inertial spheres in evolving Taylor–Green vortex flow
Authors: Jayaram Rohith , Jie Yucheng , Zhao Lihao , Andersson Helge I.
Published: April 2020

Clustering of inertial spheres in a statistically unsteady flow field is believed to be different from particle clustering observed in statistically steady flows. The continuously evolving three-dimensional Taylor–Green vortex (TGV) flow exhibits time-varying length and time scales, which are likely to alter the resonance of a given particle with the evolving flow structures. The tendency of homogeneously introduced spherical point-particles to cluster preferentially in the TGV flow is observed to depend on the particle inertia, parameterized in terms of the particle response time τp. The degree of the inhomogeneity of the particle distribution is measured by the variance σ2 of Voronoï volumes. The time evolution of the particle-laden TGV flow is characterized by a viscous dissipation time scale τd and the effective Stokes number Steff = τp/τd. Particles with low/little inertia do not cluster in the early stage when the TGV flow only consists of large-scale and almost inviscid structures and Steff < 1. Later, when the large structures have been broken down into smaller vortices, the least inertial particles exhibit a stronger preferential concentration than the more inertial spheres. At this stage, when the viscous energy dissipation has reached its maximum level, the effective Stokes number of these particles has reached the order of one. Particles are generally seen to cluster preferentially at strain-rate dominated locations, i.e., where the second invariant Q of the velocity gradient tensor is negative. However, a memory effect can be observed in the course of the flow evolution where high σ2 values do not always correlate with Q < 0.
Observation of phase transitions in shocked tin by molecular dynamics
Authors: Soulard L. , Durand O.
Published: April 2020

We investigate the phase transition of a tin single crystal under shock loading by using large molecular dynamics simulations. The interatomic interactions are described by a Modified Embedded Atom Model (MEAM) potential. The comparison of the Hugoniot curves corresponding to four crystallographic orientations with the poly-crystal experimental Hugoniot curve ensures that MEAM is an acceptable choice. We show the necessity to use large samples (i.e., several hundred million atoms) in order to limit size effects. A precise analysis of the results shows that tin undergoes in simulations a solid/solid phase transition beyond 10 GPa, in good agreement with the static phases diagram. Moreover, the calculated shock melting point is close to the experimental melting curve. The final structure behind the shock is analyzed by using a combination of Steinhardt’s coefficients and the radial distribution function. We obtain a three phase mixture containing a compressed initial β phase, a γ phase predicted by the phase diagram, and an intermediate phase. The time transition is close to 100 ps. Finally, we calculate the integrated x-ray diffraction spectrum. The comparison with recent time-resolved experiments is satisfactory and validates our simulation method.
Pulse-shape analysis in Cd0.9Zn0.1Te0.98Se0.02 room-temperature radiation detectors
Authors: Chaudhuri Sandeep K. , Sajjad Mohsin , Mandal Krishna C.
Published: April 2020

The effect of trapping of charge carriers on the shape of the charge pulses from room temperature nuclear detectors, based on a recently discovered quaternary semiconductor Cd0.9Zn0.1Te0.98Se0.02 (CZTS), has been studied. We present a charge-trapping model that explains the pulse shapes for its entire duration from radiation detectors containing multiple defect types. A piecewise continuous model, based on the movement of a large number of charge carriers rather than a single charge, has been proposed to explain the pulse shapes from planar room temperature nuclear detectors. An experimental method based on the model has been described to extract charge-trapping information. This model can be applied to similar semiconductor detectors with electrically active trap centers, in general, to extract information like pre-trapping drift times. Charge pulses from a CZTS planar detector, exposed to 5486 keV alpha particles emitted by a 241Am source, were acquired using a digitizer, and the pulse shapes were explained based on the proposed model. The pre-trapping drift times for electrons as well as holes in CZTS were calculated and studied as a function of operating bias voltage, and a contrast between their bias dependent behaviors was noticed, indicating the behavioral difference of electron and hole traps.
Broad-ferromagnetic-linewidth non-metallic gyromagnetic spheres: A comparison of linewidth characterization methods
Authors: Pacewicz A. , Krupka J. , Aleshkevych P. , Salski B. , Kopyt P. , Frender R.
Published: April 2020

The ferromagnetic linewidth obtained via different rectangular cavity ferromagnetic resonance experimental data processing algorithms has been compared. Approaches based on perturbation theory closed-form formulas, resonance frequency dispersion, Q-factor, transmitted power, and an electrodynamic transcendental equation (TDE) have been considered. The results were compared with direct Q-factor measurements in a subwavelength cavity and an electron paramagnetic resonance spectrometer. Three spherical samples, of approximately 1 mm in diameter and different saturation magnetization values, were investigated: monocrystalline gallium-substituted YIG (Ga:YIG, 50 Gs), polycrystalline aluminum-substituted YIG (Al:YIG, 380 Gs), and polycrystalline zirconium–calcium-substituted YIG (Zr,Ca:YIG,1826 Gs). A new approach to processing rectangular cavity data, based on the TDE, has been proposed and validated. Using the proposed approach, it is possible to obtain the accurate value of the linewidth in regimes where strong coupling between the sample and the cavity does not occur but the small perturbation assumption is no longer valid either. There is also no need to decouple the sample from the cavity. The conclusions of this work are useful for resonant characterization of not only magnetic spheres but also other shapes.
Funnel hopping Monte Carlo: An efficient method to overcome broken ergodicity
Authors: Finkler Jonas A. , Goedecker Stefan
Published: April 2020

Monte Carlo simulations are a powerful tool to investigate the thermodynamic properties of atomic systems. In practice, however, sampling of the complete configuration space is often hindered by high energy barriers between different regions of configuration space, which can make ergodic sampling completely infeasible within accessible simulation times. Although several extensions to the conventional Monte Carlo scheme have been developed, which enable the treatment of such systems, these extensions often entail substantial computational cost or rely on the harmonic approximation. In this work, we propose an exact method called Funnel Hopping Monte Carlo (FHMC) that is inspired by the ideas of smart darting but is more efficient. Gaussian mixtures are used to approximate the Boltzmann distribution around local energy minima, which are then used to propose high quality Monte Carlo moves that enable the Monte Carlo simulation to directly jump between different funnels. We demonstrate the method’s performance on the example of the 38 as well as the 75 atom Lennard-Jones clusters, which are well known for their double funnel energy landscapes that prevent ergodic sampling with conventional Monte Carlo simulations. By integrating FHMC into the parallel tempering scheme, we were able to reduce the number of steps required significantly until convergence of the simulation.
Height and position of the Bragg peak in the stopping of charged particles
Authors: Sigmund Peter , Schinner Andreas
Published: April 2020

We have explored the systematics of the magnitude and location of the Bragg peak in the stopping of ions in matter in terms of the atomic numbers Z1 and Z2 of the projectile and target species, respectively. Extensive analysis of experimental results reveals major deviations from predictions by the Bethe stopping theory. In particular, the height of the Bragg peak follows a ∝Z14/3 dependence rather than ∝Z12 following from the Bethe theory. We assert this to be due to the fact that, with the exception of H ions, the Bragg peak lies below the energy range where the Bethe theory can be expected to be valid. Although experimental values from different sources show significant scatter, especially in the location of the peak on the energy axis, general trends are well described by the Bohr stopping theory. Moreover, good agreement is found in the absolute magnitude with computations with PASS, including oscillations as a function of Z2, which are known to be related to the mean excitation energy or I-value.
On the equivalence of vapor-deposited and melt-quenched glasses
Authors: Wang Zhe , Du Tao , Anoop Krishnan N. M. , Smedskjaer Morten M. , Bauchy Mathieu
Published: April 2020

Vapor deposition can yield glasses that are more stable than those obtained by the traditional melt-quenching route. However, it remains unclear whether vapor-deposited glasses are “allowable” or “forbidden,” that is, if they are equivalent to glasses formed by cooling extremely slowly a liquid or if they differ in nature from melt-quenched glasses. Here, based on reactive molecular dynamics simulation of silica glasses, we demonstrate that the allowable or forbidden nature of vapor-deposited glasses depends on the temperature of the substrate and, in turn, is found to be encoded in their medium-range order structure.
An analytical solution of the inverse problem of capillary imbibition
Authors: Khatoon Sufia , Phirani Jyoti , Bahga Supreet Singh
Published: April 2020

The inverse problem of capillary imbibition involves determination of the capillary geometry from the measurements of the time-varying meniscus position. This inverse problem is known to have multiple solutions, and to ensure a unique solution, measurements of imbibition kinematics in both directions of the capillary are required. We here present a closed-form analytical solution of the inverse problem of determining the axially varying radius of a capillary from experimental data of the meniscus position as a function of time. We demonstrate the applicability of the method for solving the inverse capillary imbibition problem for two cases, wherein the data for imbibition kinematics are obtained (i) using numerical simulations and (ii) from published experimental work. In both cases, the axially varying capillary radius predicted by the analytical solution agrees with the true capillary radius. In contrast to the previously proposed iterative methods for solving the inverse capillary imbibition problem, the analytical method presented here yields a direct solution. This analytical solution of the inverse capillary imbibition problem can be helpful in determining the internal geometry of micro- and nano-porous structures in a non-destructive manner and design of autonomous capillary pumps for microfluidic applications.
Single-cell O
2
exchange imaging shows that cytoplasmic diffusion is a dominant barrier to efficient gas transport in red blood cells
Authors: Richardson Sarah L. , Hulikova Alzbeta , Proven Melanie , Hipkiss Ria , Akanni Magbor , Roy Noémi B. A. , Swietach Pawel
Published: April 2020

Significance

Blood is routinely tested for gas-carrying capacity (total hemoglobin), but this cannot determine the speed at which red blood cells (RBCs) exchange gases. Such information is critical for evaluating the physiological fitness of RBCs, which have very limited capillary transit times (<1 s) for turning over substantial volumes of gas. We developed a method to quantify gas exchange in individual RBCs and used it to show that restricted diffusion, imposed by hemoglobin crowding, is a major barrier to gas flows. Consequently, hematological disorders manifesting a change in cell shape or hemoglobin concentration have uncharted implications on gas exchange, which we illustrate using inherited anemias. With its single-cell resolution, the method can identify physiologically inferior subpopulations, providing a clinically useful appraisal of blood quality.
Direct kinetic measurements and theoretical predictions of an isoprene-derived Criegee intermediate
Authors: Caravan Rebecca L. , Vansco Michael F. , Au Kendrew , Khan M. Anwar H. , Li Yu-Lin , Winiberg Frank A. F. , Zuraski Kristen , Lin Yen-Hsiu , Chao Wen , Trongsiriwat Nisalak , Walsh Patrick J. , Osborn David L. , Percival Carl J. , Lin Jim Jr-Min , Shallcross Dudley E. , Sheps Leonid , Klippenstein Stephen J. , Taatjes Craig A. , Lester Marsha I.
Published: April 2020

Significance

Ozonolysis is an important sink of alkenes in Earth’s troposphere, leading to the formation of Criegee intermediates (CIs), whose reactions significantly impact tropospheric composition. The reactivity of the four-carbon unsaturated CIs derived from isoprene, the most abundant alkene, has remained unknown until now. Direct measurements of one such CI, methyl vinyl ketone oxide (MVK-oxide), with water vapor, SO
2
, and formic acid are reported herein, substantiated by high-level theory, revealing the long lifetime of
syn-
MVK-oxide with respect to unimolecular decay and reaction with water vapor. Through a combination of direct experiment, high-level theory, and global modelling,
syn
-MVK-oxide is shown to survive high-humidity tropospheric environments and play a role in sulfuric acid formation and formic acid removal.
High-throughput antibody screening from complex matrices using intact protein electrospray mass spectrometry
Authors: Sawyer William S. , Srikumar Neha , Carver Joseph , Chu Phillip Y. , Shen Amy , Xu Ankai , Williams Ambrose J. , Spiess Christoph , Wu Cong , Liu Yichin , Tran John C.
Published: April 2020

Significance

While electrospray ionization–mass spectrometry (ESI-MS) provides higher resolution for larger proteins, the conventional liquid chromatography (LC)-MS method suffers from low throughput. Our described RapidFire-MS workflow demonstrated unprecedented screening throughput as fast as 15 s/sample, a 10-fold improvement over conventional LC-MS approaches. The screening enabled selection of clones with the highest purity of bispecific antibody production with intact masses as accurate as 7 ppm with baseline resolution at the glycoform level in samples as complex as plasma sample. The utility of the method can be expanded to many other applications that can exploit the advantages of high-throughput intact protein MS analyses including but not limited to pharmacokinetic analyses, enzymatic screening, biotransformation characterization, and quality control screening.
Structural basis for Zika envelope domain III recognition by a germline version of a recurrent neutralizing antibody
Authors: Esswein Shannon R. , Gristick Harry B. , Jurado Andrea , Peace Avery , Keeffe Jennifer R. , Lee Yu E. , Voll Alisa V. , Saeed Mohsan , Nussenzweig Michel C. , Rice Charles M. , Robbiani Davide F. , MacDonald Margaret R. , Bjorkman Pamela J.
Published: April 2020

Recent epidemics demonstrate the global threat of Zika virus (ZIKV), a flavivirus transmitted by mosquitoes. Although infection is usually asymptomatic or mild, newborns of infected mothers can display severe symptoms, including neurodevelopmental abnormalities and microcephaly. Given the large-scale spread, symptom severity, and lack of treatment or prophylaxis, a safe and effective ZIKV vaccine is urgently needed. However, vaccine design is complicated by concern that elicited antibodies (Abs) may cross-react with other flaviviruses that share a similar envelope protein, such as dengue virus, West Nile virus, and yellow fever virus. This cross-reactivity may worsen symptoms of a subsequent infection through Ab-dependent enhancement. To better understand the neutralizing Ab response and risk of Ab-dependent enhancement, further information on germline Ab binding to ZIKV and the maturation process that gives rise to potently neutralizing Abs is needed. Here we use binding and structural studies to compare mature and inferred-germline Ab binding to envelope protein domain III of ZIKV and other flaviviruses. We show that affinity maturation of the light-chain variable domain is important for strong binding of the recurrent VH3-23/VK1-5 neutralizing Abs to ZIKV envelope protein domain III, and identify interacting residues that contribute to weak, cross-reactive binding to West Nile virus. These findings provide insight into the affinity maturation process and potential cross-reactivity of VH3-23/VK1-5 neutralizing Abs, informing precautions for protein-based vaccines designed to elicit germline versions of neutralizing Abs.
Quasi-Fermi level splitting in nanoscale junctions from ab initio
Authors: Lee Juho , Yeo Hyeonwoo , Kim Yong-Hoon
Published: April 2020

Significance

A universal feature of semiconductor devices is that the functional channel region is driven out of equilibrium, or formally it cannot be characterized by one global Fermi level. Naturally, the concept of quasi-Fermi (imref) levels (QFLs) and their splitting was introduced, and it has now become a standard theoretical tool to describe finite-bias nonequilibrium operations of semiconductor devices. However, after 70 years from its inception by Shockley, the first-principles calculation of QFLs still remains to be achieved. Applying a recently developed ab initio approach, we herein calculate the QFLs in molecular junctions and particularly for a conducting single-molecule junction establish the correlations among the splitting of QFLs, nonlinear electrostatic potential drop, and asymmetric Landauer residual-resistivity dipole distribution.
Landscape analysis of adjacent gene rearrangements reveals BCL2L14–ETV6 gene fusions in more aggressive triple-negative breast cancer
Authors: Lee Sanghoon , Hu Yiheng , Loo Suet Kee , Tan Ying , Bhargava Rohit , Lewis Michael T. , Wang Xiao-Song
Published: April 2020

Triple-negative breast cancer (TNBC) accounts for 10 to 20% of breast cancer, with chemotherapy as its mainstay of treatment due to lack of well-defined targets, and recent genomic sequencing studies have revealed a paucity of TNBC-specific mutations. Recurrent gene fusions comprise a class of viable genetic targets in solid tumors; however, their role in breast cancer remains underappreciated due to the complexity of genomic rearrangements in this cancer. Our interrogation of the whole-genome sequencing data for 215 breast tumors catalogued 99 recurrent gene fusions, 57% of which are cryptic adjacent gene rearrangements (AGRs). The most frequent AGRs,BCL2L14–ETV6,TTC6–MIPOL1,ESR1–CCDC170, andAKAP8–BRD4, were preferentially found in the more aggressive forms of breast cancers that lack well-defined genetic targets. Among these,BCL2L14–ETV6was exclusively detected in TNBC, and interrogation of four independent patient cohorts detectedBCL2L14–ETV6in 4.4 to 12.2% of TNBC tumors. Interestingly, these fusion-positive tumors exhibit more aggressive histopathological features, such as gross necrosis and high tumor grade. Amid TNBC subtypes,BCL2L14–ETV6is most frequently detected in the mesenchymal entity, accounting for ∼19% of these tumors. Ectopic expression of BCL2L14–ETV6 fusions induce distinct expression changes from wild-type ETV6 and enhance cell motility and invasiveness of TNBC and benign breast epithelial cells. Furthermore, BCL2L14–ETV6 fusions prime partial epithelial–mesenchymal transition and endow resistance to paclitaxel treatment. Together, these data reveal AGRs as a class of underexplored genetic aberrations that could be pathological in breast cancer, and identifyBCL2L14–ETV6as a recurrent gene fusion in more aggressive form of TNBC tumors.
On the oscillations and future asymptotics of locally rotationally symmetric Bianchi type III cosmologies with a massive scalar field*
Authors: Fajman David , Heißel Gernot , Maliborski Maciej
Published: April 2020

We analyse spatially homogenous cosmological models of locally rotationally symmetric Bianchi type III with a massive scalar field as matter model. Our main result concerns the future asymptotics of these spacetimes and gives the dominant time behaviour of the metric and the scalar field for all solutions for late times. This metric is forever expanding in all directions, however, in one spatial direction only at a logarithmic rate, while at a power-law rate in the other two. Although the energy density goes to zero, it is matter dominated in the sense that the metric components differ qualitatively from the corresponding vacuum future asymptotics. Our results rely on a conjecture for which we give strong analytical and numerical support. For this we apply methods from the theory of averaging in nonlinear dynamical systems. This allows us to control the oscillations entering the system through the scalar field by the Klein–Gordon equation in a perturbative approach.
Step height standards based on self-assembly for 3D metrology of biological samples
Authors: Heikkinen V , Kassamakov I , Viitala T , Järvinen M , Vainikka T , Nolvi A , Bermúdez C , Artigas R , Martinez P , Korpelainen V , Lassila A , Hæggström E
Published: April 2020

Modern microscopes and profilometers such as the coherence scanning interferometer (CSI) approach sub-nm precision in height measurements. Transfer standards at all measured size scales are needed to guarantee traceability at any scale and utilize the full potential of these instruments, but transfer standards with similar characteristics upon reflection to those of the measured samples are preferred. This is currently not the case for samples featuring dimensions of less than 10 nm and for biosamples with different optical charasteristics to silicon, silica or metals. To address the need for 3D images of biosamples with traceable dimensions, we introduce a transfer standard with dimensions guaranteed by natural self-assembly and a material that is optically similar to that in typical biosamples. We test the functionality of these transfer standards by first calibrating them using an atomic force microscope (AFM) and then using them to calibrate a CSI. We investigate whether a good enough calibration accuracy can be reached to enable a useful calibration of the CSI system. The result is that the calibration uncertainty is only marginally increased due to the sample.
Penalized maximum-likelihood reconstruction for improving limited-angle artifacts in a dedicated head and neck PET system
Authors: Zhang Hengquan , Wang Yuli , Qi Jinyi , Abbaszadeh Shiva
Published: April 2020

Positron emission tomography (PET) suffers from limited spatial resolution in current head and neck cancer management. We are building a dual-panel high-resolution PET system to aid the detection of tumor involvement in small lymph nodes (

<

10 mm in diameter). The system is based on cadmium zinc telluride (CZT) detectors with cross-strip electrode readout (1 mm anode pitch and 5 mm cathode pitch). One challenge of the dual-panel system is that the limited angular coverage of the imaging volume leads to artifacts in reconstructed images, such as the elongation of lesions. In this work, we leverage a penalized maximum-likelihood (PML) reconstruction for the limited-angle PET system. The dissimilarity between the image to be reconstructed and a prior image from a low-resolution whole-body scanner is penalized. An image-based resolution model is incorporated into the regularization. Computer simulations were used to evaluate the performance of the method. Results demonstrate that the elongation of the 6-mm and 8-mm diameter hot spheres is eliminated with the regularization strength γ being 0.02 or larger. The PML reconstruction yields higher contrast recovery coefficient (CRC) of hot spheres compared to the maximum-likelihood reconstruction, as well as the low-resolution whole-body image, across all hot sphere sizes tested (3, 4, 6, and 8 mm). The method studied in this work provides a way to mitigate the limited-angle artifacts in the reconstruction from limited-angle PET data, making the high-resolution dual-panel dedicated head and neck PET system promising for head and neck cancer management.
Delineating rainbow reflection and trapping with applications for energy harvesting
Authors: Chaplain G J , Pajer Daniel , De Ponti Jacopo M , Craster R V
Published: April 2020

Important distinctions are made between two related wave control mechanisms that act to spatially separate frequency components; these so-called rainbow mechanisms either slow or reverse guided waves propagating along a graded line array. We demonstrate an important nuance distinguishing rainbow reflection from genuine rainbow trapping and show the implications of this distinction for energy harvesting designs, through inspection of the interaction time between slowed zero group velocity waves and the array. The difference between these related mechanisms is highlighted using a design methodology, applied to flexural waves on mass loaded thin Kirchhoff–Love elastic plates, and emphasised through simulations for energy harvesting in the setting of elasticity, by elastic metasurfaces of graded line arrays of resonant rods atop a beam. The delineation of these two effects, reflection and trapping, allows us to characterise the behaviour of forced line array systems and predict their capabilities for trapping, conversion and focussing of energy.
Hubble telescope 30 years in orbit: personal reflections
Authors: Williams Robert
Published: April 2020

With an initial requirement to make observations a minimum of 5–10 years, Hubble Space Telescope (HST) has continued to operate well for 30 years. It has relied upon five servicing missions to repair and replace essential components. Since the final Space Shuttle mission 10 years ago, it has avoided major breaks in its operation, with the only serious effects of aging in space being a progressive deterioration in the performance of the gyroscopes and sensitivity of the instrument detectors. A number of factors were important in making HST a scientific landmark. Ground-breaking discoveries have been made with HST — the most important being the discovery of cosmic acceleration. When HST operation ceases, future observations in space should be assured with successful operation of major missions now planned by NASA, ESA, and the Chinese and Japanese Space Agencies.
HIKER: a halo-finding method based on kernel-shift algorithm
Authors: Sun Shuang-Peng , Liao Shi-Hong , Guo Qi , Wang Qiao , Gao Liang
Published: April 2020

We introduce a new halo/subhalo finder, HIKER (a Halo fInder based on KERnel-shift algorithm), which takes advantage of a machine learning method – the mean-shift algorithm combined with the Plummer kernel function, to effectively locate density peaks corresponding to halos/subhalos in density field. Based on these density peaks, dark matter halos are identified as spherical overdensity structures, and subhalos are bound substructures with boundaries at their tidal radius. By testing HIKER code with mock halos, we show that HIKER performs excellently in recovering input halo properties. In particular, HIKER has higher accuracy in locating halo/subhalo centres than most halo finders. With cosmological simulations, we further show that HIKER reproduces the abundance of dark matter halos and subhalos quite accurately, and the HIKER halo/subhalo mass functions and V
max functions are in good agreement with two widely used halo finders, SUBFIND and AHF.
New multi-color photometric investigations of solar-like contact binary V680 Per
Authors: Wang Jing-Jing , He Jia-Jia , Zhao Song-Qing
Published: April 2020

High-precision CCD photometric observations of the contact binary V680 Per were obtained in 2016. Its symmetric multi-color light curves were analyzed by using the Wilson–Devinney (2013) program. These photometric solutions suggest that V680 Per is an A-type W UMa contact binary with the mass ratio of q = 0.693 and a fill-out factor of f = 18.84% with a small temperature difference of 101 K. Based on all minimum times, the O − C curve was analyzed for the first time in this study. A cyclic oscillation (A
3 = 0.00093 d, T
3 = 4.92 yr) superimposed on a secular decrease (dP/dt = −8.16 × 10−8 d yr−1) was identified. The continuous decrease in period is possibly a result of mass transfer from the more massive component to the less massive one, or angular momentum loss due to a magnetic stellar wind. Because of this secular decrease, it is predicted that the degree of contact will become higher, and V680 Per will evolve into a deeper overcontact binary.
Exploring the spectral information content in the LAMOST medium-resolution survey (MRS)
Authors: Zhang Bo , Liu Chao , Li Chun-Qian , Deng Li-Cai , Yan Tai-Sheng , Shi Jian-Rong
Published: April 2020

Although high-resolution stellar spectra allow us to derive precise stellar labels (effective temperature, metallicity, surface gravity, elemental abundances, etc.) based on resolved atomic lines and molecular bands, low-resolution spectra have been proved to be competitive in determiningmany stellar labels at comparable precision. It is useful to consider the spectral information content when assessing the capability of a stellar spectrum in deriving precise stellar labels. In this work, we quantify the information content brought by the LAMOST-II medium-resolution spectroscopic survey (MRS) using the gradient spectra as well as the coefficients-of-dependence (CODs). In general, the wavelength coverage of the MRS well constrains the stellar labels but the sensitivities of different stellar labels vary with spectral types and metallicity of the stars of interest. Consequently, this affects the performance of the stellar label determination from the MRS spectra. By applying the SLAM method to the synthetic spectra which mimic the MRS data, we find that the precision of the fundamental stellar parameters T
eff, log g and [M/H] are better when combining both the blue and red bands of the MRS. This is especially important for warm stars because the Hα line located in the red part plays a more important role in determining the effective temperature for warm stars. With blue and red parts together, we are able to reach similar performance to the low-resolution spectra except for warm stars. However, at [M/H] ∼ −2.0 dex, the uncertainties of fundamental stellar labels estimated from MRS are substantially larger than that from low-resolution spectra. We also tested the uncertainties of T
eff, log g and [M/H] From MRS data induced from the radial velocity mismatch and find that a mismatch of about 1 km s−1, which is typical for LAMOST MRS data, would not significantly affect the stellar label estimates. Finally, reference precision limits are calculated using synthetic gradient spectra, according to which we expect abundances of at least 17 elements to be measured precisely from MRS spectra.
Investigation of near-contact semi-detached binary WUMi through observations and evolutionary models
Authors: Soydugan Faruk , Soydugan Esin , Aliçavuş Fahri
Published: April 2020

W UMi is a near contact, semi-detached, double-lined eclipsing binary star with an orbital period of 1.7 d. Simultaneous analysis of new BV R multi-color light curves and radial velocity data yields the main astrophysical parameters of the binary and its component stars. We determined mass and radius to be M
1 = 3.22 ± 0.08 M
⊙, R
1 = 3.63 ± 0.04 R
⊙ for the primary star and M
2 = 1.44 ± 0.05 M
⊙, R
2 = 3.09 ± 0.03 R
⊙ for the secondary star. Based on analysis of mid-eclipse times, variation in the orbital period is represented by a cyclic term and a downward parabola. Mass loss from the system is suggested for a secular decrease (−0.02 s yr−1) in the period. Both the mechanisms of a hypothetical tertiary star orbiting around W UMi and the surface magnetic activity of the less massive cooler companion were used to interpret periodic changes. Observational parameters were found to be consistent with binary stellar evolution models produced in the non-conservative approach of MESA at a higher metallicity than the Sun and an age of about 400 Myr for the system. Evidence that the system is rich in metal was obtained from spectral and kinematic analysis as well as evolution models. W UMi, a high mass ratio system compared to classical semi-detached binaries, is an important example since it is estimated from binary evolutionary models that the system may reach its contact phase in a short time interval.
Simultaneous photometric and spectral analysis of a new outburst of V1686 Cyg
Authors: Andreasyan Hasmik , Magakian Tigran , Movsessian Tigran
Published: April 2020

We present an analysis of the optical observations of Herbig Ae/Be (HAeBe) star V1686 Cyg, which is associated with a small isolated star-forming region around HAeBe star BD+40°4124. We observed this star as a part of our project investigating young eruptive stars. Observations were conducted on the 2.6-m telescope of Byurakan Observatory from 2015 to 2017. In this period, we obtained direct images of V1686 Cyg and 14 medium- and low-resolution spectra. In the course of observations, we noticed that this star underwent an atypical brightness outburst. After data reduction, we found that the full rise and decline in the brightness of V1686 Cyg had an amplitude of almost 3 magnitudes and lasted about 3 months. We were also able to track changes in the stellar spectrum during the outburst, which are correlated with the photometric variations.
Cosmological constraints on ultra-light axion fields
Authors: Kang Jian-Gang , Gong Yan , Cheng Gong , Chen Xuelei
Published: April 2020

Ultra-light axions (ULAs) with mass less than 10−20 eV have interesting behaviors that may contribute to either dark energy or dark matter at different epochs of the Universe. Their properties can be explored by cosmological observations, such as expansion history of the Universe, cosmic large-scale structure, cosmic microwave background, etc. In this work, we study the ULAs with mass around 10−33 eV, which means that the ULA field still rolls slowly at present with the equation of state w = −1 as dark energy. To investigate the mass and other properties of this kind of ULA field, we adopt the measurements of Type Ia supernova (SN Ia), baryon acoustic oscillation (BAO), and Hubble parameter H(z). The Markov Chain Monte Carlo (MCMC) technique is employed to perform the constraints on the parameters. Finally, by exploring four cases of the model, we find that the mass of this ULA field is about 3 × 10−33 eV if assuming the initial axion field ϕ
i = M
pl. We also investigate a general case by assuming ϕ
i ≤ M
pl, and find that the fitting results of ϕ
i/M
pl are consistent with or close to 1 for the datasets that we use.
Study on the pointing model of a slant-axis terahertz antenna
Authors: Wang Yu , Lou Zheng , Zuo Ying-Xi , Kang Hao-Ran , Zhang Ming-Zhu
Published: April 2020

This paper describes the establishment and verification of an accurate pointing model for a 1.2 m aperture slant-axis terahertz antenna. A new analytical pointing model for the slant-axis antenna is presented based on an analogy to that of the alt-azimuth antennas. Furthermore, extra error terms are added to the pointing model based on the structure and mechanical analysis of the slant-axis antenna. To verify the pointing model experimentally, a pointing error measurement method based on photogrammetric techniques is proposed. Using this method, pointing behaviors of the antenna are accurately measured without the aid of astronomical observations, and major sources of the pointing errors are measured individually by photogrammetry and their respective coefficients are compared with those in the analytical pointing model. The results show that an extended pointing model consisting 21 error terms can significantly reduce the residual systematic errors compared with the traditional model, more details are given in the following sections.
Photometric light curve solutions of three ultra-short period eclipsing binaries
Authors: Acerbi Francesco , Michel Raul , Barani Carlo , Martignoni Massimiliano , Fox-Machado Lexter
Published: April 2020

We present the results of our study of the eclipsing binary systems CSS J112237.1+395219, LINEAR 1286561 and LINEAR 2602707 based on new CCD B, V, Rc
and Ic
complete light curves. The ultra-short period nature of these stars, as reported by Drake et al., is confirmed and the system’s periods are revised. The light curves were modeled using the 2003 version of the Wilson-Devinney code. When necessary, cool spots on the surface of the primary component were introduced to account for asymmetries in the light curves. As a result, we found that CSS J112237.1+395219 is a W UMa type contact binary system belonging to W subclass with a mass ratio of q = 1.61 and a shallow degree of contact of 14.8% where the primary component is hotter than the secondary one by 500 K. LINEAR 1286561 and LINEAR 2602707 are detached binary systems with mass ratios q = 3.467 and q = 0.987 respectively. These detached systems are low-mass M-type eclipsing binaries with similar temperatures. The marginal contact, fill-out factor and temperature difference between components of CSS J112237.1+395219 suggest that this system may be at a key evolutionary state predicted by thermal relaxation oscillation (TRO) theory. From the estimated absolute parameters, we conclude that our systems share common properties with other ultra-short period binaries.
Preliminary Study of Melting Basalt Rock As A Raw of Advanced Material
Authors: Isnugroho Kusno , Birawidha David C , Hendronursito Yusup , Amin Muhammad , Muttaqii Muhammad Al , Efriyo Hadi R Agung , Fazma Muhammad Fadil
Published: April 2020

The aim of this research is to conduct initial research on the process of melting basalt rocks using an upright shaft furnace. The preliminary process of melting basalt rock has been carried out as a raw of advanced material. The raw material of basalt was obtained from East Lampung, Lampung Province, Indonesia. Coke is used as fuel for the smelting process. Laboratory scale of shaft furnace which is designed and made by Research Unit for Mineral Technology is used for the smelting process. The basalt smelting process lasts for 4 hours, starting from the charging materials to the tapping process, with a process temperature of 1500-1600 °C. The yield of this process can reach 68,7%, while the rest was trap inside the bottom of the furnace due to lack of pressure at the end of the smelting process and the other was lost during the process. The product was basalt cast with the following dominant composition is MgO 5.244%, Al2O3 21.295%, SiO2 48.750, CaO 10.138%, Fe2O3 11.019%, TiO2 1.361% and Na2O 2.132%. However, the products obtained are still brittle. Therefore, further research related to the crystallization process needs to be done to obtain products that are not brittle.
Optimization of Fuel Savers Preheater Water System (PWS) for Diesel Fuel
Authors: Pranoto A , Purwanto A
Published: April 2020

The present work aims to design and investigate the performance of diesel fuel heating system called Preheater Water System (PWS). The PWS is made of stainless-steel container, copper spiral pipe and electric heater. The container has a diameter of 140 mm and height of 170 mm. The tube has a diameter of 8.5 mm. This system heats the diesel fuel before entering the fuel injector pump. The system utilizes heat from the heat from radiator cooling water and also uses additional electrical heating. The system is equipped with temperature sensor to measure the diesel fuel entering the fuel injector pump. The results show that at engine speed of 800 rpm (idle condition), temperature of the fuel increases 55°C, fuel consumption is 26% more efficient. At medium speed of 1200 rpm, the temperature increases up to 55°C and fuel consumption is 15% less. Meanwhile at the engine speed of 2200 rpm, the temperature rises to 60°C and fuel consumption increases up to 15%. In can be conclude that the PWS works well and the optimum temperature of the diesel fuel is 50°C.
Optimization of information technology utilization based on geography information system as a marketing media for micro, small, and medium enterprises to improve competitiveness in Bantul Regency, Indonesia
Authors: Hardiyanto Denny , Sholeh Muhammad , Rachmawati Rr Yuliana
Published: April 2020

Micro, small and medium enterprises (MSMEs) are the largest group of economic actors in the Indonesian economy. The growth of the micro industry grew by 8% every year, especially in Bantul Regency, Special Region of Yogyakarta. Various factors that led to the growth of the small micro industry in Bantul were caused by the increasing stretch of business in the creative economy sector, the majority of which were engaged in the craft sector. As support, the Government of Bantul provides policies that protect or secure raw materials for handicraft or industrial production properly and facilitate physical promotion by participating in various exhibition events through online media. In the era of information technology development, the support of online information system become one of the promotional media that can reach a large area. The research objectives are to build a website for MSME in Bantul Regency and to provide a media for MSME actors to advertise their goods and services. In this study, the MSME information system that was built was equipped with facilities for maps, images and videos of MSME products. This map facility makes it easy for users to go to business locations. The system was developed by utilizing the Application Programming Interface (API) of google map and database used to store all MSME data using MySQL with the PHP: Hypertext Pre-processor Programming language. The result is development of marketplace website (https://wartacara.com/ukm) that have many features to explore and advertise MSME actor in Bantul Regency.
The Effect of Orientation Fibres on Flexural and Tensile Properties of Arenga Pinnata Fibres Reinforced Polyester Composites
Authors: Widodo R D , Robi W , Rusiyanto  , Nugroho A , Al-Janan D H
Published: April 2020

This paper presents flexural and tensile properties of sugar palm (Arenga pinnata) fibres-reinforced polyester composites study. The fibres were treated by alkaline solution with 5% NaOH solution for 2 hours of soaking time. The composites were prepared with different orientations of fibres (i.e. 0° + 45°, 0° + 90°, 45° + 90°, and 45° + (-45°)), while the ratio between Arenga pinnata fibres and polyester is 30 percent volume. Hand lay-up method was employed to produce the specimens. ASTM D-790 03 and ASTM D-3039 standard were employed to characterize the specimens in good sequent. As the result, the specimen with 45°+90° orientation generated maximum important values both in flexural strength (24.03 MPa) and modulus (4.01 GPa), tensile strength (23.84 MPa) and modulus elasticity (0.97 GPa). This is due to palm fibres as reinforcement that forms an angle of 90 ° or increasingly upright to the load crossing field (load of bending) and tensile load giving the effect of maximum reinforcement compared to other fibres orientations.
Identification of the delaying factors on construction work completion in Jambi city according to the contractor perception
Authors: Handayani Elvira , Amalia Kiki Rizky , Yamali Fakrul Rozi
Published: April 2020

One of the successes in the Implementation of Construction Works is marked by the implementation of timely work. However, in the process of implementing the construction work often encountered various problems, one of which is work delays. the number of factors is the cause of delays that are often faced by parties involved, especially contractors who act as executors. This study aims to determine the main factors of the delay in the Construction Work. The questionnaire was distributed to 63 Middle-class contractors with the value of the company’s assets qualified into the M1-M2 based on the Business Entity Registration List (DRBU) of the Jambi City Construction Services Development Agency (LPJK). The factors of delay in construction work are grouped into 7 factors, each of which consists of several sub-factors. The results showed that the most dominant factor in the construction work in Jambi City was environmental factors with sub-factors Heavy rain / waterlogged work location with a percentage of 15.73%, while the Time Factors namely Sub-factors Too late shop drawing agreement is the 7th most influential factor in work delay has the smallest percentage value of 13.41%.
The design programming simulation as a reference for the adjustment of the relay GFR on the protection of the airway medium voltage 20 KV
Authors: Djufri Umar , Yandra Fadli Eka
Published: April 2020

Short circuit fault phase to ground and phase to phase is one of the problems that may arise in the operation of the power transformer in a Substation. The interference caused by the presence of a short circuit caused a lot of losses, losses on the transmission system of electricity and losses on the part of consumers of electric energy. One way to overcome this disorder is with safety protection relay OCR and GFR that works with the Power Breaker (Circuit Breaker). This research will create a Programming-Based Object (PBO) using the GUI of MATLAB, where programs are designed is one answer to cope with the calculation of the adjustment GFR (Ground Fault Relay) attached on the network, the validation of the programming that is done using armed forces data from the company, which for reasons of privacy mentioned as XYZ. Great protection Setting of the interference 1 phase ground occurs along the feeder can be concluded that the working time of GFR on the side of the outgoing and incoming have a difference of 0.4 seconds, thus the design of programming windows in this study can be used as a reference as setting tms on GFR which is mounted on an equipment of protection of electric power because it has been in accordance with the applicable standards.
The Nature of Coconut Fibre Fly Ash-Based Mechanical Geopolymer
Authors: Zulfiati Ria , Saloma  , Idris Yakni
Published: April 2020

In order to reduce carbon emissions in the atmosphere, one of the steps is to use environmentally friendly concrete. Environmentally friendly concrete uses industrial waste as a substitute for cement, such as rice husk ash, palm burning ash, coal burning ash or fly ash. Today, the development of the use of fly ash as a substitute for cement has been widely used, especially in geopolymer concrete. This study uses natural fibres such as coconut fibre. Coconut fibre is also an alternative material in the use of natural fibres as geopolymer mortar composites. This research carried out compressive strength and flexural strength test by doing several variations such as the length of coconut fibres 10 mm, 20 mm, and 30 mm and the percentage of fibre used was 0, 0.25% and 0.50% of the weight of the mortar. Geopolymer mortar made from 100% fly ash. The concentration of NaOH solution used was 14 M and 16 M. The results of this study indicate that the fibre length of 30 mm with a percentage of 0.50% fibre at a concentration of 16 M NaOH solution gives a compressive strength of 40.016 MPa and the greatest flexural strength of 8.799 MPa at 28 days mortar age.