bluuebunny/crossref_metadata_2025 huggingface dataset:
Translational Research in Biliary Atresia: News from Mice and Men
Authors: Madadi-Sanjani Omid , Petersen Claus
Published: August 2019

Biliary atresia (BA) is a fibro-obliterative cholangiopathy of unknown etiology. While Kasai portoenterostomy achieves temporary biliary drainage in some cases, BA remains the most common indication for liver transplantation during childhood. During the last few decades, observations on BA, like cholestatic diseases in animals and the introduction of different animal models for BA, have not achieved the anticipated results, and we are still not able to translate the basic research to the patient's bedside. This article presents a review of the literature on available BA animal models and gives a glimpse of future developments.
Respiratory and Hemodynamic Changes in Neonates with Hypoxic–Ischemic Encephalopathy during and after Whole-Body Hypothermia
Authors: Sheppard Stephanie Rosenbloom , Desale Sameer , Abubakar Kabir
Published: August 2019

Objective This study aimed to determine the degree to which whole-body hypothermia (WBH) impacts hemodynamic and respiratory status during hypothermia and the subsequent rewarming period in neonates with hypoxic–ischemic encephalopathy (HIE).

Study Design This is a retrospective study reviewing the medical records of infants treated with WBH. Data including oxygenation index (OI), ventilator efficiency index (VEI), fraction of inspired oxygen (FiO2), blood lactate level, heart rate (HR), and mean blood pressure (MBP) were collected from defined time points from the beginning, middle, and end of WBH and then every 2 hours from the beginning of rewarming for 14 hours thereafter. The analysis included 65 infants. Data were analyzed using a piecewise linear regression with a mixed-effect model.

Results HR decreased during WBH and significantly increased during rewarming. Lactate level, OI, VEI, FiO2, and MBP all decreased during WBH but showed no significant change during and after rewarming.

Conclusion There was a decrease in metabolic demand as measured by oxygen requirement, OI, HR, and MBP during WBH, but only HR increased during rewarming, with no significant change in the other parameters. Some of this effect may be explained by improvement in the respiratory condition over time.
Medizinprodukte ständig verfügbar: Alles auf Lager
Authors: Reisinger Kathrin
Published: August 2019

Bei laufendem Betrieb hat das UKE in Hamburg Anfang 2017 ein neues automatisches Kleinteilelager implementiert. Der Kraftakt hat sich für den Maximalversorger gleich in mehrfacher Hinsicht gelohnt.
Polydimethylsiloxane (PDMS) irreversible bonding to untreated plastics and metals for microfluidics applications
Authors: Agostini Matteo , Greco Gina , Cecchini Marco
Published: August 2019

In order to properly manipulate liquids into microfluidic networks, an accurate sealing of the device is of paramount importance. Polydimethylsiloxane (PDMS) is ubiquitously used for fabricating microfluidic components, owing to its low cost, easy and fast fabrication, and optical transparency. However, PDMS is characterized by low surface energy, making its bonding to many substrates not trivial. Here is presented a versatile technique for PDMS microchannel bonding on untreated plastic and metal surfaces. First, the PDMS surface is functionalized with (3-aminopropyl) triethoxysilane (APTES) for further cross-linking with epoxy groups. Then, the PDMS-APTES surface is coated with Norland Optical Adhesive 74 (NOA74). Finally, the PDMS-APTES-NOA74 is put in contact with the target material and the glue is cured under a UV light. In order to characterize the bonding strength, a complete PDMS-on-gold microfluidic device is fabricated and tested with increasing injection pressures. Different liquids and a gas (nitrogen) are applied without leakage up to 2 bars, a value comparable to the one reported for the standard glass-PDMS bonding through plasma oxygen activation. The same technique is then successfully replicated with other nonmetallic substrates of interest for microfluidics, i.e., glass, poly(methyl methacrylate), polystyrene, polyethylene terephthalate, cyclic olefin copolymer, demonstrating its great versatility and potential for, but not limited to, microfluidic applications and LOC engineering.
Quasilinear Schrödinger equations with nonlinearities interacting with high eigenvalues
Authors: Silva Edcarlos D. , Silva J. S.
Published: August 2019

It is the established existence and multiplicity of solutions for quasilinear Schrödinger equations where the nonlinear term is 3-superlinear or 3-asymptotically linear at infinity in an appropriate sense. The main difficulty arises from the fact that the nonlinearity has an interaction with high eigenvalues for the linear eigenvalue problem. Under these conditions, we consider a local linking theorem together with a compactness result. In order to ensure our main results we, consider two distinct eigenvalues problems and some kind of crossing of eigenvalues.
A three dimensional numerical quantum mechanical model of field electron emission from metallic surfaces covered with carbon adsorbates
Authors: Márquez-Mijares Maykel , Lepetit Bruno
Published: August 2019

The effect of metallic surface contamination on the field electron emission is investigated for the first time using a three dimensional quantum mechanical model. The plane wave periodic version of the density functional theory is used to obtain wavefunctions and potentials. Local and averaged emitted current densities are obtained from them using the time dependent perturbation theory. This method is used to study the effect of the presence of carbon adsorbates on emission from tungsten surfaces. Fowler-Nordheim plots, which provide the dependence of the emitted current with the external electric field, show that carbon contamination inhibits emission. Significant differences with the results of the analytical Fowler-Nordheim model are observed. Emission images (i.e., the spatial dependence of the emitted current density) are presented to identify the important emission spots. These images are significantly different from the electronic density plots usually presented to model constant height scanning tunneling microscope images. Analysis of the emitted current density energy distributions in the light of the projected local density of states provides a deeper understanding of the emission process.
Wall ablation effect on the recombination pumping of EUV laser in pinching capillary discharge
Authors: Vrbova M. , Vrba P. , Jancarek A. , Nevrkla M. , Bobrova N. A. , Sasorov P. V.
Published: August 2019

Magnetohydrodynamic simulations of plasma evolution in nitrogen-filled alumina capillaries, taking into account the ablation of capillary walls, are reported. Time dependences of the ionization state and populations of the selected energy levels of nitrogen ions are evaluated by the kinetic code FLYCHK, used as a postprocessor. Plasma properties, including the spectral characteristics, simulated according to experiments done in different laboratories, are in good agreement with experimental results. We made some estimations of the wall evaporation, showing that capillary wall ablation may play a significant role. We show that ablation of the capillary material is a serious barrier on the way to 13 nm nitrogen laser recombination pumping by the capillary pinch.
Lateral charge carrier transport properties of B-10 enriched hexagonal BN thick epilayers
Authors: Grenadier S. , Maity A. , Li J. , Lin J. Y. , Jiang H. X.
Published: August 2019

Neutron detectors based on B-10 enriched hexagonal boron nitride (h-10BN or h-BN) epilayers have demonstrated the highest thermal neutron detection efficiency among solid-state neutron detectors at about 58%. However, many fundamental transport parameters of h-BN, including the room temperature carrier mobility, minority carrier lifetime, and surface recombination velocity, which are essential to the performance of detectors, are still unknown. We report here the carrier drift mobilities (μ) and lifetimes (τ) of both electrons and holes in h-10BN epilayers measured by using a time-of-flight (TOF) technique. Lateral photoconductive type detectors fabricated from a 65 μm thick freestanding h-10BN epilayer were utilized to carry out the TOF measurements, which revealed μe ∼ 34 cm2/V s for electrons and μh ∼ 36 cm2/V s for holes and carrier lifetimes on the order of tens of microseconds. By combining the values of μ measured from TOF with S/μ (the ratio of the surface recombination velocity to mobility) deduced directly from the bias voltage dependence of photocurrent, S for both electrons (Se ∼ 1.4 × 104 cm/s) and holes (Sh ∼ 2.7 × 103 cm/s) in h-10BN has been extracted. The determination of these important fundamental parameters (μ, τ, and S) not only provides a better understanding of the carrier dynamics and electrical transport properties of h-BN but is also valuable for further advancing the development of h-BN materials and devices.
Improved contacts to p-type MoS2 transistors by charge-transfer doping and contact engineering
Authors: Zhang Siyuan , Le Son T. , Richter Curt A. , Hacker Christina A.
Published: August 2019

MoS2 is known to show stubborn n-type behavior due to its intrinsic band structure and Fermi level pinning. Here, we investigate the combined effects of molecular doping and contact engineering on the transport and contact properties of monolayer (ML) MoS2 devices. Significant p-type (hole-transport) behavior was only observed for chemically doped MoS2 devices with high work function palladium (Pd) contacts, while MoS2 devices with low work function metal contacts made from titanium showed ambipolar behavior with electron transport favored even after prolonged p-doping treatment. ML MoS2 transistors with Pd contacts exhibit effective hole mobilities of (2.3 ± 0.7) cm2 V−1 S−1 and an on/off ratio exceeding 106. We also show that p-doping can help to improve electrical contacts in p-type field-effect transistors: relatively low contact resistances of (482 ± 40) kΩ μm and a Schottky barrier height of ≈156 meV were obtained for ML MoS2 transistors. To demonstrate the potential application of 2D-based complementary electronic devices, a MoS2 inverter based on pristine (n-type) and p-doped monolayer MoS2 was fabricated. This work presents a simple and effective route for contact engineering, which enables the exploration and development of high-efficiency 2D-based semiconductor devices.
Macroscale single crystal graphene templated directional alignment of liquid-crystal microlens array for light field imaging
Authors: Xin Zhaowei , Deng Bing , Wei Dong , Chen Mingce , Hu Chai , Zhang Xinyu , Wang Haiwei , Xie Changsheng , Liu Zhongfan , Peng Hailin
Published: August 2019

Single crystal graphene (SCG) as a transparent conductive electrode material with a relatively strong liquid crystal molecule anchoring energy is expected to provide remarkable improvements to the functionalities of electro-optical devices. Here, we efficiently grew macroscale SCG on Cu(111) and transferred it onto a silica substrate to fabricate a liquid-crystal microlens array (LCMLA) integrated with an arrayed photodetector. As shown, the LC molecules can be aligned along a desired direction over the SCG electrode with the zigzag lattice of the graphene. Furthermore, we demonstrate a prototypical plenoptic camera using the SCG-LCMLA with a controlled unidirectional LC alignment. Dual mode imaging to acquire both two-dimensional and light field images was realized by integrating photodetectors with the electrically adjustable SCG-LCMLA.
Improving sensitivity of self-powered room temperature NO2 sensor by triboelectric-photoelectric coupling effect
Authors: Su Yuanjie , Yao Mingliang , Xie Guangzhong , Pan Hong , Yuan Hong , Yang Min , Tai Huiling , Du Xiaosong , Jiang Yadong
Published: August 2019

Nitrogen dioxide sensors with high sensitivity and low energy consumption are demanded for atmosphere sensing networks. Here, a self-powered room temperature NO2 sensor has been developed based on the conjugation between the triboelectric and photoelectric effect. By converting the mechanical motions into electricity, a triboelectric nanogenerator (TENG) serves as a power source to simultaneously drive chemoresistive gas sensing and UV illumination. Under a 5 Hz external impact, the output voltage drop across interdigital electrodes has a proportional relationship with the NO2 concentration. A self-powered optomechatronic gas sensor (OGS) with hydrothermal ZnO nanowires synthesized at a concentration of 0.035 mol/l exhibits a superior response (∼14.8) and sensitivity (0.302 ppm−1) than those synthesized at other concentrations. Furthermore, the influence of the external force frequency and rectification on the gas sensing properties was systematically investigated. It is found that the TENG induced built-in electric field can effectively modulate the internal quantum efficiency and thus the sensing performance of OGSs. This work not only paves the way for constructing self-powered optomechatronic devices and systems but also pushes forward the active multifunctional network node for environmental monitoring.
Design triple points, nexus points, and related topological phases by stacking monolayers
Authors: Xie Yuee , Gong Cheng , Zhou Jun , Yan Xiaohong , Chen Yuanping
Published: August 2019

Triple points and nexus points are two interesting topological phases, which have been reported in some three-dimensional materials. Here, we propose that triple points, nexus points, and related phases, such as topological tangle nodal lines, can be obtained by alternatively stacking two types of monolayers. Two conditions for the stacking monolayers are required: the first condition is that they have a threefold (C3) rotation symmetry and three mirror planes along the C3 axis; the second condition is that one of the monolayers should be insulating while the other one should be metallic (or semiconducting) and has a double degenerate band and a nondegenerate band at the Γ point around the Fermi level. Hexagonal boron nitride (HBN) and α/α′-boron sheets are suggested as candidate materials. Even if HBN is a wide-gap insulator, the interactions between layers lead to crossings of the nondegenerate and double degenerate bands along the direction normal to the nanosheets and thus form triple/nexus points or related phases. A tight-binding model is adopted to explain the phase transition between triple points, nexus points, and other related phases.
Computing three-dimensional densities from force densities improves statistical efficiency
Authors: Coles Samuel W. , Borgis Daniel , Vuilleumier Rodolphe , Rotenberg Benjamin
Published: August 2019

The extraction of inhomogeneous 3-dimensional densities around tagged solutes from molecular simulations is known to have a very high computational cost because this is traditionally performed by collecting histograms, with each discrete voxel in three-dimensional space needing to be visited significantly. This paper presents an extension of a previous methodology for the extraction of 3D solvent number densities with a reduced variance principle [Borgis et al., Mol. Phys. 111, 3486–3492 (2013)] to other 3D densities such as charge and polarization densities. The approach is also generalized to cover molecular solvents with structures described using rigid geometrical constraints, which include in particular popular water models such as SPC/E and TIPnP class of models. The noise reduction is illustrated for the microscopic hydration structure of a small molecule, in various simulation conditions, and for a protein. The method has large applicability to simulations of solvation in many fields, for example around biomolecules, nanoparticles, or within porous materials.
The role of annealing ambient on diffusion of implanted Si in β-Ga2O3
Authors: Sharma Ribhu , Law Mark E. , Fares Chaker , Tadjer Marko , Ren Fan , Kuramata A. , Pearton S. J.
Published: August 2019

The most common n-type dopant, Si, was implanted into bulk (-201) β-Ga2O3 at total doses from 2x1013-2x1015 cm-2 and annealed at 1100 °C for 10-120 secs in either O2 or N2 ambients. Secondary Ion Mass Spectrometry profiling showed a significant effect of the annealing ambient on the Si diffusivity. In the case of O2 annealing, there was extensive redistribution of the Si across the entire dose range, while in sharp contrast, the use of N2 annealing suppressed the Si diffusion. The results are consistent with a defect-assisted process. Excellent fits to the Si profiles were obtained with the FLOOPS simulator, assuming mobile vacancy/defect concentrations as the important factor for the difference in the O2 vs N2 annealing ambients. One possibility is that for N2 anneals, more Ga vacancies are created, enabling interstitial Si to migrate onto a substitutional Ga site where it has low diffusivity. The N2 ambient also suppresses loss of Si to the surface, with >90% of the initial dose retained after annealing at 1100 °C for 120 secs, compared to 66-77% with O2 anneals under the same conditions.
Electronic structure, Fermi surface and x-ray magnetic circular dichroism in the CeAgSb2
Authors: Antonov V. N.
Published: August 2019

The electronic structure, Fermi surface, angle dependence of the cyclotron masses and extremal cross sections of the Fermi surface as well as x-ray magnetic circular dichroism (XMCD) in the CeAgSb2 compound were investigated from first principles using the fully relativistic Dirac linear muffin-tin orbital method. In our calculations Ce 4f states have been considered as: 1) itinerant using the generalized gradient approximation (GGA), 2) fully localized, treating them as core states, and 3) partly localized using the GGA + U approximation. The effect of the spin-orbit (SO) interaction and Coulomb repulsion U in a frame of the GGA + U method on the Fermi surface, orbital dependence of the cyclotron masses, and extremal cross sections of the Fermi surface are examined in details. We show that the conventional GGA band calculations fail to describe the Fermi surface of the CeAgSb2 due to wrong position of Ce 4f states (too close to the EF). On the other hand, fully localized (4f states in core) and the GGA + U approach produce similar Fermi surfaces and dHvA frequencies in the CeAgSb2. A good agreement with the experimental data of XMCD spectra at the Ce M4.5 edges was achieved using the GGA + U approximation. The origin of the XMCD spectra in the compound is examined. The core hole effect in the final states has been investigated using a supercell approximation. It improves the agreement be-tween the theory and the experiment of the XAS and the XMCD spectra at the Ce M4.5 edges.
Simulating flame propagation in channels and tubes
Authors: Larter Raima
Published: August 2019

Computational simulations of flames propagating through channels and tubes reveal an interesting dependence on Lewis number.
A pathway linking translation stress to checkpoint kinase 2 signaling in
Neurospora crassa
Authors: Diernfellner Axel C. R. , Lauinger Linda , Shostak Anton , Brunner Michael
Published: August 2019

Significance

Checkpoint kinase 2 (CHK-2) is a key component of the DNA damage response (DDR) pathway and its activation mechanism is evolutionarily conserved. We show that PERIOD-4 (PRD-4), the CHK-2 ortholog of
Neurospora crassa
, is part of an additional signaling pathway that is activated when protein translation is compromised. Translation stress induces phosphorylation of PRD-4 by an upstream kinase distinct from those of the DDR pathway. We present evidence that the activating kinase is mTOR. Translation stress is sensed via a decrease in levels of an unstable inhibitor that antagonizes phosphorylation of PRD-4.
Role of a patatin-like phospholipase inPlasmodium falciparumgametogenesis and malaria transmission
Authors: Singh Pallavi , Alaganan Aditi , More Kunal R. , Lorthiois Audrey , Thiberge Sabine , Gorgette Olivier , Guillotte Blisnick Micheline , Guglielmini Julien , Aguilera Shivani Shankar , Touqui Lhousseine , Singh Shailja , Chitnis Chetan E.
Published: August 2019

Significance

Malaria transmission involves a complex process that is initiated whenPlasmodiumgametocytes ingested during a blood meal are activated in the mosquito midgut and transform into gametes. The process of gametogenesis involves rounding up of activated gametocytes, exflagellation of male gametes, and gamete egress. Here, we have used a genetic approach to identify a patatin-like phospholipase, PfPATPL1, that mediates gametocyte rounding up, exflagellation, and secretion of a perforin-like protein, PfPLP2, which ruptures peripheral membranes to enable egress. We demonstrate that genetic depletion of PfPATPL1 reduces the transmission efficiency of malaria parasites in mosquitoes. Our study identifies PfPATPL1 as a player in the process of gametogenesis and suggests that phospholipases could be targeted to inhibit transmission and help eliminate malaria.
Toxoplasma gondiieffector TgIST blocks type I interferon signaling to promote infection
Authors: Matta Sumit K. , Olias Philipp , Huang Zhou , Wang Qiuling , Park Eugene , Yokoyama Wayne M. , Sibley L. David
Published: August 2019

In contrast to the importance of type II interferon-γ (IFN-γ) in control of toxoplasmosis, the role of type I IFN is less clear. We demonstrate here that TgIST, a secreted effector previously implicated in blocking type II IFN-γ signaling, also blocked IFN-β responses by inhibiting STAT1/STAT2-mediated transcription in infected cells. Consistent with a role for type I IFN in cell intrinsic control, ∆Tgist mutants were more susceptible to growth inhibition by murine and human macrophages activated with IFN-β. Additionally, type I IFN was important for production of IFN-γ by natural killer (NK) cells and recruitment of inflammatory monocytes at the site of infection. Mice lacking type I IFN receptors (Ifnar1−/−) showed increased mortality following infection with wild-type parasites and decreased virulence of ∆Tgist parasites was restored in Ifnar1−/−mice. The findings highlight the importance of type I IFN in control of toxoplasmosis and illuminate a parasite mechanism to counteract the effects of both type I and II IFN-mediated host defenses.
Arabidopsis BRUTUS-LIKE E3 ligases negatively regulate iron uptake by targeting transcription factor FIT for recycling
Authors: Rodríguez-Celma Jorge , Connorton James M. , Kruse Inga , Green Robert T. , Franceschetti Marina , Chen Yi-Tze , Cui Yan , Ling Hong-Qing , Yeh Kuo-Chen , Balk Janneke
Published: August 2019

Organisms need to balance sufficient uptake of iron (Fe) with possible toxicity. In plant roots, a regulon of uptake genes is transcriptionally activated under Fe deficiency, but it is unknown how this response is inactivated when Fe becomes available. Here we describe the function of 2 partially redundant E3 ubiquitin ligases, BRUTUS-LIKE1 (BTSL1) and BTSL2, in
Arabidopsis thaliana
and provide evidence that they target the transcription factor FIT, a key regulator of Fe uptake, for degradation. The
btsl
double mutant failed to effectively down-regulate the transcription of genes controlled by FIT, and accumulated toxic levels of Fe in roots and leaves. The C-terminal domains of BTSL1 and BTSL2 exhibited E3 ligase activity, and interacted with FIT but not its dimeric partner bHLH39. The BTSL proteins were able to poly-ubiquitinate FIT in vitro and promote FIT degradation in vivo. Thus, posttranslational control of FIT is critical to prevent excess Fe uptake.
Regularizations of time-crystal dynamics
Authors: Shapere Alfred D. , Wilczek Frank
Published: August 2019

Significance

Crystals—an extremely common and important class of states of matter—have been studied intensely and fruitfully for many years. Recently, the possibility of “time crystals,” which self-organize into regular patterns of behavior in time, was proposed theoretically and has inspired important experimental discoveries. This qualitatively new class of states of matter plausibly will lead, among other things, to better clocks. New concepts are needed to describe time (or space-time) crystals, because the most straightforward attempts lead to mathematical singularities. Here, we show how an enriched version of the simplest proposed time-crystal model can be realized as a limiting case of a conventional, fully nonsingular physical system. This firmer foundation predicts characteristic behavior and should support wide-ranging generalizations.
Hydrophobic catalysis and a potential biological role of DNA unstacking induced by environment effects
Authors: Feng Bobo , Sosa Robert P. , Mårtensson Anna K. F. , Jiang Kai , Tong Alex , Dorfman Kevin D. , Takahashi Masayuki , Lincoln Per , Bustamante Carlos J. , Westerlund Fredrik , Nordén Bengt
Published: August 2019

Significance

The main stabilizer of the DNA double helix is not the base-pair hydrogen bonds but coin-pile stacking of base pairs, whose hydrophobic cohesion, requiring abundant water, indirectly makes the DNA interior dry so that hydrogen bonds can exert full recognition power. We report that certain semihydrophobic agents depress the stacking energy (measurable in single-molecule experiments), leading to transiently occurring holes in the base-pair stack (monitorable via binding of threading intercalators). Similar structures observed in DNA complexes with RecA and Rad51, and previous observations of spontaneous strand exchange catalyzed in semihydrophobic model systems, make us propose that some hydrophobic protein residues may have roles in catalyzing homologous recombination. We speculate that hydrophobic catalysis is a general phenomenon in DNA enzymes.
Micromechanical modelling of mechanochemical processes in heterogeneous materials
Authors: Poluektov M , Freidin A B , Figiel Ł
Published: August 2019

There is a range of practical problems where advanced engineering heterogeneous materials undergo chemical transformations. The primary example of such system is energy storage materials, in particular anodes of Li-ion batteries containing active Si particles. The exploitation of such anodes involves extreme volumetric expansion of the active particles during the chemical reaction. The expansion is causing mechanical stress, which, in turn, influences the kinetics of chemical reactions even up to their arrest. A particular reaction between Si and Li is localised, as well as a number of other reactions, such as oxidation or precipitate formation. The model presented in this paper accounts for the kinetics of the reactions in a collection of particles inside a matrix material. The microstructure is modelled using the multiscale mean-field (MF) framework based on the incremental Mori–Tanaka (IMT) method. This is the first application of a multiscale MF technique to modelling reaction front kinetics in particles and linking the intra-particle kinetics with the response of the matrix. A number of physical effects arising from the influence of the deformation mechanisms of the matrix on the kinetics of the intra-particle reactions is investigated. Furthermore, the applicability of the proposed model and the IMT homogenisation scheme is studied by comparison to the full-field simulations in the cases of small and finite strains.
Finite Element Modelling and Updating of a Bolted Structure Using Elements Representing the Stiffness Members, Bolts and Affected Areas of the Joints
Authors: Omar R , Rani M N Abdul , Yunus M A
Published: August 2019

Efficient and accurate analytical representation of bolted joints in an assembled structure for the prediction of the dynamic behaviour of the structure has been a crucial unsolved issue in the finite element (FE) community. 3D modelling of bolted joints, possessing a large number of degrees of freedom, leads to very high computational time. This paper proposes an efficient representation of bolted joints for the prediction of the dynamic behaviour of a bolted structure. The FE model of the bolted joints was developed using CBUSH element connectors for bolt shanks and CELAS element connectors for the stiffness of the members at the affected areas of the bolted joints. The results of the normal modes analysis of the FE model of the bolted structure were in a very good correlation with experimental modal analysis (EMA) counterparts quantified by a range of MAC values between 0.91 to 0.99 for all modes. Finite element model updating was used to improve the accuracy of the FE model of the bolted joints. The updated FE model of the assembled structure was validated with the physical tested structure. It was found that the comparison of the results has shown good agreement. In addition, the natural frequencies and mode shapes predicted from the proposed model have been found to be more accurate than the results obtained from the previous analytical models reported in the literature on bolted joint modelling of dynamic behaviour investigation. The proposed model can be used for a large and complex structure.
Identification of the nonlinearity in mass-spring system via experimental method
Authors: Bahari A R , Yunus M A , Rani M N Abdul , Shah M A S Aziz , Iskandar Mirza W I I Wan , Salleh N
Published: August 2019

Engineering structures operate with a nonlinear dynamics behaviour at certain amplitude of input range which will produce noticeable changes and unpredictable effects. In this paper, the nonlinear property of a spring is investigated. The simplified mass-spring system is developed which consists of two springs attached on a thin plate structure. The translational degree of freedom is considered in the experimental and a preferential direction on the length direction of the spring is investigated. The linear property is first investigated via impact testing for the acceleration measurement. Subsequently, the spectral testing with different amplitude of periodic chirp excitations is carried out to identify the nonlinear property of the springs. The nonlinear dynamics behaviour of the springs are identified from the significant changes of natural frequencies from the frequency response function of the system.
Occupational Noise Exposure Among Airport Workers in Malaysia: An Ergonomic Investigation
Authors: Athirah B. , Nurul Shahida M.S.
Published: August 2019

Occupational noise is defined as a disturbance of sound at a workplace received by a worker’s auditory system when they are working. A sustained and prolonged exposure to the noise can cause permanent hearing loss or damage to the worker. According to Occupational Safety and Health Act (OSHA), there is a certain tolerable noise level that can be exposed to the workers at a given time. This study aims to investigate the level of noise produced at the landing area in Sultan Ahmad Shah (SAS) Airport, Kuantan, Malaysia. A comprehensive ergonomic assessment divided into two phases is utilized in order to evaluate the noise exposure of the workers. In Phase I, an initial Ergonomics Risk Assessment is applied to gather the information on the ergonomic risk factors of the noise exposure, while for Phase II, an advanced Ergonomics Risk Assessment is used by monitoring the noise using occupational noise level meter. Thirty workers from the landing area which consists of the ground handlers were included as the subjects for this study. The value of noise exposure is measured while the workers perform their job. Results suggested that (a) the workers are aware of the noise exposure as per results shown in initial Ergonomics Risk Assessment in Phase I, and (b) the workers were exposed to high level of noise as suggested by OSHA (> 100 dBA at 2 hours exposure). With the suggested findings, the management of SAS Airport needs to create sufficient awareness to emphasize the usage of hearing protection devices in the workplace.
Application of Micro Electro-Mechanical Sensors (MEMS) Devices with Wifi Connectivity and Cloud Data Solution for Industrial Noise and Vibration Measurements
Authors: Sahdom A. S.
Published: August 2019

This paper introduces the application of Microelectromechanical Systems (MEMS) for industrial noise and vibration measurements. Sound measurement was done using a compact sound level meter with type 1 Micro-Electro-Mechanical Systems (MEMS) microphone while the vibration measurement used a compact vibration measuring device with 3-axial accelerometer, which is also a MEMS type sensor. The MEMS Sensors being used in both measuring devices provide advantages in terms of features and specifications such as weight reduction, compact in size and economically affordable for various applications. Besides MEMS Sensors, the devices are equipped with wireless connectivity to a local server via a WIFI router. This eliminates the usage of wired connection in data handling. Furthermore, Cloud connectivity is an add-on feature to the wireless capabilities of both devices. Using the Cloud features enable threshold alert alarm, data monitoring and collection to be done regardless of time and location of devices, provided that the internet connectivity is available to the user and the devices.
Retaining {100} fibre texture in electrical steel via strain-induced boundary migration recrystallisation.
Authors: Ji M , Davis C , Slater C
Published: August 2019

In this paper, the feasibility of retaining the preferred {100} fibre texture for non-grain oriented (NGO) electrical steel from the as-cast columnar {100} grains by encouraging recrystallisation via the strain induced boundary migration (SIBM) mechanism was investigated. Rolling with intermediate annealing stages before the final anneal was used to reduce the stored energy through recovery before the final recrystallisation step. A strong {100} fibre recrystallisation texture, i.e. 32% area fraction, was seen in the sample which was warm deformed to 1.6 strain with 5 intermediate annealing stages then annealed at 950 °C for 5 minutes (to observe the early stages of recrystallisation) or 1 hour. Whereas only 12 - 14% {100} fibre component was observed after 1.2 strain with a single or with no intermediate annealing stage. It was found that the {100} fibre recrystallisation texture was formed in regions adjacent to parental deformed grains with {100} fibre texture due to the SIBM recrystallisation mechanism. EBSD imaging analysis was used to follow the recrystallisation process in the same microstructural region using interrupted heat treatments and it was seen that the {100} texture grains carried very low stored energy after deformation, which meant the subgrains in these grains bulged into the surrounding grains with higher stored energy. Due to its slow recrystallisation nucleation rate, a low overall stored energy is preferred to encourage {100} texture recrystallised grains to form via the SIBM recrystallisation mechanism.
Determination of static recrystallization and recovery parameters for steel by fitting model to stress relaxation data
Authors: Pohjonen A , Seppälä O , Jokiranta A , Kaijalainen A , Somani M , Porter D , Larkiola J , Kömi J
Published: August 2019

A model for static recrystallization by Zurob et al. [1] has been fitted to experimental stress relaxation [2] data obtained on a low-alloyed steel using a Gleeble thermomechanical simulator. The model has been implemented as an algorithm that calculates the stress relaxation as a function of time, including physical descriptions of the recovery and recrystallization processes. The activation energy and volume were used as fitting parameters for recovery, and the activation energy of diffusion and nucleation site density were used as the fitting parameters for recrystallization. The four fitting parameters were determined from the experimental data by applying the Nelder-Mead algorithm within Matlab software. It can be concluded from the preliminary results that Zurob’s model can be successfully fitted to the stress relaxation data in order to illustrate the static restoration characteristics and kinetics in carbon steels using these fitting parameters.
Preferred orientation formation in surface layer of aluminum sheet subjected to friction roll surface processing and temperature gradient annealing
Authors: Takayama Yoshimasa , Hamano Ryuichi , Arakawa Takuya , Watanabe Hideo
Published: August 2019

Preferred orientation formation in surface layer of aluminum sheet subjected to friction roll surface processing (FRSP) and temperature gradient annealing has been investigated by SEM/EBSD analysis. FRSP imposed severe shear strain in the surface layer of the aluminum sheet, where the indentation was selected as 0.1mm and the feeding speed was set as 0.3mm/s. The annealing with steep temperature gradient in longitudinal direction was applied to the small specimen of 12mm long, 10mm wide and 1mm thick, which made microstructural evolution concentrated to the nearest layer to the surface. Shear strain more than 10 was imposed at a site of 14μm beneath the surface. The temperature gradient more than 20K/mm was attained even for aluminum which has high thermal conductivity. The {100} pole of ND/TD (FRSP plane/FRSP direction) FRSPed specimen showed very weak intensity of <001>//ND while the {111} pole implies <110>//TD. In contrast, the shear texture component {111}<110> mainly evolved in the specimen subjected to FRSP and the ordinary annealing. Evolution of the component {111}<110> after the temperature gradient annealing were compared with that after the ordinary annealing in consideration of stored strain energy in each crystallographic orientation.
Effect of Cr and C on microstructure evolution of medium carbon steels during friction stir welding process and their mechanical property
Authors: Cheng C , Kadoi K , Tokita S , Fujii H , Ushioda K , Inoue H
Published: August 2019

The aim of the present study was to investigate the effect of chromium and carbon in medium carbon steels on the microstructure evolution during FSW process and their mechanical property. The materials are dynamically recrystallized in austenite during FSW followed by phase transformation from austenite to ferrite, pearlite, bainite, and martensite. In the case of 0.2%C, the microstructure of the stir zone transited from pearlite and ferrite to bainite and martensite with the increase in chromium content. On the other hand, in the case of 0.4%C, the microstructure transited from pearlite to martensite with the increase in chromium content. The specimens of 0.2%C-4%Cr, 0.4%C-2%Cr and 0.4%C-4%Cr showed high tensile strength of over 1.5 GPa. In addition, even though the microstructures in the stir zones of the specimens are martensite, the elongation of 0.2%C-4%Cr was 31%while those of the others were less than 5%. TEM observation revealed that many tiny carbides precipitated in martensite of the stir zone of 0.2%C-4%Cr and micro twin formed in martensite in those of 0.4%C-2%Cr and 0.4%C-4%Cr. Thus, it was considered that auto-tempering occurred in the stir zone of 0.2%C-4%Cr during FSW process. The carbide precipitation in martensite is more effective to improve the tensile elongation compared with micro twin formation.
Influences of cold rolling, recrystallization and surface effect on the transformation textures in a TA10 titanium alloy
Authors: Yang P , Wei Z G , Gu X F , Cui F E , Mao W M
Published: August 2019

A transformation treatment based on surface effect induced transformation is applied to cold rolled TA10 titanium alloy sheets to change and control transformation texture. This kind of treatment can promote the α-phase nucleation at sheet surface region during cooling and control the growth of surface α-grains into center layer of sheet. The results indicate that as the heating temperature increased, the transformation textures in the final HCP-structured TA10 sheets changed in helium atmosphere from the recrystallization type texture of <11-20>//RD to the transformation type texture of <11-20>//ND. The textures in sheets treated at low transformation temperature of 1000°C reveal texture memory effect, while those treated at high transformation temperature of 1100°C illustrate the effects of both transformation strain and anisotropy in elastic modules of HCP titanium crystals. The surface effect is promoted by cooling gas of helium, which leads to layered structures along sheet thickness direction. The surface region often shows small equiaxed grains with recrystallization orientations, while the center layer reveals coarse grains with either plate-like or equiaxed grain morphology corresponding to transformation orientation or recrystallization orientation, respectively. The special grain boundaries in plate-like α variants are different from those in equiaxed grains. These differences in morphologies, sizes and orientations are explained in terms of the mechanism change of the factors affecting variant selection.
Effect of hot deformation on grain refinement in a Re containing nickel-based superalloy
Authors: Mukhtarov Sh Kh , Imayev V M , Ganeev A A , Shakhov R V , Logunov A V
Published: August 2019

Hot deformation experiments have been performed for a novel polycrystalline superalloy with a nominal composition Ni-12.5(Al,Ti,Nb,Ta)-37(Cr,Co,W,Mo,Re)-0.17(C,La,Y,Ce,B) (in wt. %) intended for disc applications in gas turbine engines. The as-cast superalloy was characterized by a higher amount of the γ’ phase, a coarse γ grain size and a high level of dendritic segregation. The as-cast superalloy was subjected to long-term annealing to homogenize and heterogenize the material prior to hot deformation. The hot working experiments were performed in a different manner. First, isothermal compression experiments at temperatures below and above the γ’ solvus temperature were performed. These experiments allowed us to determine the temperature-strain rate conditions providing improved workability. Second, unidirectional forging experiments were performed under quasi-isothermal conditions using a specially designed can made of a stainless steel. The use of the optimal temperature-strain conditions and the can provided reasonable hot workability and delocalized occurrence of recrystallization processes during hot forging. EBSD analysis of the forged workpieces revealed that the grain refinement resulted from continuous dynamic recrystallization. For the first time hot deformation processing was successfully developed for the rhenium containing ingot-metallurgy nickel-based superalloy.
Turning the corner on US power sector CO2 emissions—a 1990–2015 state level analysis
Authors: Mohlin Kristina , Bi Alex , Brooks Susanne , Camuzeaux Jonathan , Stoerk Thomas
Published: August 2019

Total CO2 emissions from the United States power sector increased over the period 1990–2005, but peaked soon after, and by 2015 they had declined by 20% compared to 2005. This study analyzes the supply-side drivers of the increasing trend up until 2005 as well as the factors across US states that enabled significant reductions in the following decade. Using index decomposition analysis, we show that the two main factors driving the CO2 decrease were natural gas substituting for coal and petroleum, and large increases in renewable energy generation (primarily wind)—which were responsible for 60% and 30% of the decline respectively since 2005. Both effects were concentrated in states where low natural gas prices or a combination of federal tax credits, state energy policies, decreasing costs of renewables, and advantageous wind conditions drove significant reductions of CO2 emissions—resulting in the overall national emissions decline.
A Review on Process Parameters and their effects on Dissimilar Friction Stir Welding of Aluminium and Steel Alloys
Authors: Chitturi Veerendra , Rao Pedapati Srinivasa , Awang Mokhtar
Published: August 2019

Friction Stir Welding (FSW) presents numerous advantages over conventional fusion welding techniques such as eliminating the need for a shielding gas, requiring less energy per weld, and the lack of a flame or arc making it safer in the work place. Another advantage of FSW is its ability to join materials that are extremely difficult, or impossible to weld with conventional fusion techniques. The growing need for dissimilar welding relates to joining aluminium and steel base metals. Individually, both metals are utilized extensively in the automotive and aerospace industries due to various advantages respectively, including lightweight, high specific strength, and recyclability. Like conventional welding methods, the intermetallic compound formation represents the main problem issue in FSW. Heat cycle has a significant effect on Intermetallic Compounds thickening phase transformation and the elimination of the amorphous phase. The hybrid techniques utilized in FSW for Al-to-steel joints reveal high joint strength in conjunction with high costs of setup and equipment. These techniques modify the steel flow around the rotated pin by acting as an assisted heat source. Process parameters play the most important role in defining the quality of the weld to withstand. In this paper we are going to discuss the effect of different parameters on Dissimilar FSW.
Investigating the effectiveness of Water Hyacinth Fiber Mat for Soil Erosion Control
Authors: Chow M.F. , Hashrim H. , Chong S.T. , Ng Y.J.
Published: August 2019

The usage of natural fiber mat has created much attention especially in soil erosion control sector due to low cost and sustainable materials. This study investigated the effectiveness of natural fiber mat made from water hyacinth stems for soil erosion control. The water hyacinth fiber mat (WHFM) was fabricated with mesh opening size of 30 mm × 30mm and tested at 30 degree slope inclinations under simulated rainfall with constant intensity. Results revealed that soil with treatment (covered by WHFM) significantly decreased sediment yields and volumes, with average 78.74% reduction efficiency compared to untreated soil (bare soil).
Numerical Simulation on the Flame Propagation in Duct-Vented Gas Explosion: The Effect of Duct Length on the Secondary Explosion
Authors: Zubaidah Sulaiman Siti , Syazwana Noor Azmi Nurul , Ramli Azizan , Md Kasmani Rafiziana , Kholijah Abdul Mudalip Siti , Che Man Rohaida , Md Shaarani Shalyda , Iffah Mohd Arshad Zatul
Published: August 2019

Duct venting is the most recognized explosion protection technique used in the industry. However, the key problem with this technique is the appropriate design of the duct size for an effective release material to prevent the secondary explosion that can cause further damage to the plant. Factors such as duct length and diameter have a significant effect on the duct venting mechanism that contributes to the second explosion. Thus in this study, the duct-vented gas explosion was simulated with the aim to investigate the influence of duct length focusing on the flame and pressure characteristics. From the simulation analysis, it shows that vessel interconnected with the duct with 0.05 m diameter and 0.5 m length experience a flame severe problem behavior to produce the secondary explosion effect.
Effect of Mixing Parameter on Epoxy-Organo Montmorillonite Composites: Flexural and Microscopy Analysis
Authors: Mat Daud Yusrina , Fazlina Osman Azlin , Farhana Zainal Farah , Firdaus Abu Hashim Mohammad , Si Hasri M. , Si Hartati S. , Soo Li Ng , Arzuria Adnan Sinar
Published: August 2019

The effect of two mixing parameters during preparation of epoxy composites on speed 250 rpm and 500 rpm, mixing time 60, 90, 120, 150 and 180 minutes were observed in this study by flexural and microscopy analysis. Preparation epoxy composites were based on epoxy diglycidyl ether of bisphenol A (DGEBA) and montmorillonite (OMMT) filler. It was found that mixing speed at 500 rpm performed higher flexural strength as compared to 250 rpm at mixing time 150 minutes. This was due to an improved mixing speed by appropriate time as observed through Scanning Electron Microscopy (SEM).