Shape Of Gap Research Articles

Natural Regeneration Within Natural and Man-Made Canopy Gaps in Caspian Natural Beech (Fagus Orientalis Lipsky) Forest, Northern Iran

ABSTRACTThis study aimed to quantify the structural similarities and differences and the regeneration establishment in natural and man-made canopy gaps in the north of Iran. All canopy gaps and related parameters were measured within 20 ha areas, from 60 canopy gaps. Gaps were analyzed by classifying the areas including small, medium, and large gaps. The relationship between seedlings and saplings frequency with the gap size and shape was compared. Gaps area ranged from the smallest of sizes 35.7 and 33.27 m2 to the largest of sizes 536.8 and 582.26 m2, in natural and man-made gaps, respectively. There existed no significant difference in the perimeter to area ratio between the two types of gaps. Most of the gaps were created by one gapmaker. Results revealed that total seedling abundance correlated with gap size, whereas there was no significant relationship between definitive gapfiller abundance (>1.3 m) and gap size in the natural gaps. Abundance of beech seedling showed negative significant correlation with the gaps size. This investigation provided useful data to manage the natural seedlings and saplings based on forest sustainability. Canopy openings with small size, irregular shape, and created by falling one gapmaker are nearer to nature.

First implementation of plasma shape GAP control method in EAST

Preliminary implementation of plasma GAP shape control in EAST is presented. Compared with ISOFLUX method, GAP control could work together with not only real-time equilibrium reconstruction but also real-time boundary reconstruction. Based on the plasma response matrix, the GAP controller is designed and the PID parameter has been optimized for EAST plasma shape control. P-EFIT provides real-time gap calculation and GAP controller is integrated into EAST PCS. Successful plasma shape with GAP control scheme is achieved in EAST 2018 summer campaign. Experimental results prove that GAP control algorithm and controller could achieve similar control ability as ISOFLUX and provide an option for shape control with optical-based boundary reconstruction in EAST and future device CFETR.

Research on flexible rolling process of three-dimensional surface part using auxiliary rolls

Flexible rolling is a sheet metal forming process used to rapidly manufacture three-dimensional (3D) surface parts for various industries. In this paper, a flexible rolling method of 3D surface parts using auxiliary rolls is introduced, and a forming mechanism of curved surface parts is described. The generation of instability of a convex surface part in the rolling process was analyzed, and the calculation for longitudinal bending deformation was deduced to obtain an effective design method for the roll gap shape. Numerical simulations and experimentation were performed for two rolling processes, with and without auxiliary rolls, for surface parts, for which the curvature distribution and dimensional accuracy were measured and analyzed. The simulation results show that the flexible rolling process with auxiliary rolls offers a more stable rolling process with smaller curvature fluctuation of the formed parts. The experimental results further verify that the process with auxiliary rolls is better than that without auxiliary rolls, as indicated by the shape error that can be controlled in a narrower range and the smaller error value of fluctuation. Overall, the proposed flexible rolling process with auxiliary rolls offers a feasible method to effectively form 3D surface parts with good forming quality and accuracy.

The effect of garment combinations on thermal comfort of office clothing

Clothing and the enclosed air layers highly affect heat dissipation from the body and thus, are crucial factors when it comes to thermal comfort. The heat and moisture transfer is affected by the variation of the size and the shape of air gaps between the garment and the human body. In addition, the fabric and garment design properties can affect the amount of heat loss from different body parts. In this study, we investigated the effect of fabric properties (different raw materials and weave types) and the garment fit on the heat loss through the garment combinations (undershirt and shirt) for the different parts of the upper body (trunk, chest, and back) using a sweating thermal manikin. The undershirt fit and the raw material of the shirts showed strong effects on the dry thermal resistance of the garment combinations. Moreover, the undershirt properties affected the evaporative heat loss from garment combinations, and the magnitude of these effects varied over different body regions. Whilst the undershirt fit had a significant impact on the evaporative heat loss of the back region, the influence of the undershirt raw material was more important in the chest region. The findings of this study provide fundamental knowledge to improve the thermal comfort of garment combinations for office wear.

Investigation of Gas Foil Bearings With an Adaptive and Non-Linear Structure

Abstract The article discusses the results of simulation-based and experimental research carried out on gas foil bearings. Owing to the use of a set of flexible thin foils in such bearings, they exhibit certain beneficial features that cannot be found in other types of bearings. They have nonlinear operational characteristics and allow the dissipation of excess energy, thus reducing the vibration level. Moreover, gas foil bearings can self-adapt themselves to the current operating conditions by changing the shape of the lubrication gap. Therefore, they can be used to improve the dynamic performance of rotors, in particular, those operating at very high rotational speeds. This article explains the mechanisms for changes of stiffness and vibration damping in compliant components of a foil bearing. The results of the analysis of the bearing’s subassemblies using advanced numerical models are presented. They are followed by conclusions that were drawn not only from these results but also from the results of the experimental research. It has been proven that the rotor supported on carefully designed foil bearings is capable of maintaining a low vibration level, even if it operates at a high rotational speed.

Sphingomyelin Depletion from Plasma Membranes of Human Airway Epithelial Cells Completely Abrogates the Deleterious Actions of S. aureus Alpha-Toxin.

Interaction of Staphylococcus aureus alpha-toxin (hemolysin A, Hla) with eukaryotic cell membranes is mediated by proteinaceous receptors and certain lipid domains in host cell plasma membranes. Hla is secreted as a 33 kDa monomer that forms heptameric transmembrane pores whose action compromises maintenance of cell shape and epithelial tightness. It is not exactly known whether certain membrane lipid domains of host cells facilitate adhesion of Ha monomers, oligomerization, or pore formation. We used sphingomyelinase (hemolysin B, Hlb) expressed by some strains of staphylococci to pre-treat airway epithelial model cells in order to specifically decrease the sphingomyelin (SM) abundance in their plasma membranes. Such a pre-incubation exclusively removed SM from the plasma membrane lipid fraction. It abrogated the formation of heptamers and prevented the formation of functional transmembrane pores. Hla exposure of rHlb pre-treated cells did not result in increases in [Ca2+]i, did not induce any microscopically visible changes in cell shape or formation of paracellular gaps, and did not induce hypo-phosphorylation of the actin depolymerizing factor cofilin as usual. Removal of sphingomyelin from the plasma membranes of human airway epithelial cells completely abrogates the deleterious actions of Staphylococcus aureus alpha-toxin.

Validation of correction method for gap shape measurement by vertical-objective-type ellipsometric microscopy with rotating-compensator ellipsometry

Validation of correction method for gap shape measurement by vertical-objective-type ellipsometric microscopy with rotating-compensator ellipsometry

Gaps and Rings in an ALMA Survey of Disks in the Taurus Star-forming Region

Abstract Rings are the most frequently revealed substructure in Atacama Large Millimeter/submillimeter Array (ALMA) dust observations of protoplanetary disks, but their origin is still hotly debated. In this paper, we identify dust substructures in 12 disks and measure their properties to investigate how they form. This subsample of disks is selected from a high-resolution (∼0.″12) ALMA 1.33 mm survey of 32 disks in the Taurus star-forming region, which was designed to cover a wide range of brightness and to be unbiased to previously known substructures. While axisymmetric rings and gaps are common within our sample, spiral patterns and high-contrast azimuthal asymmetries are not detected. Fits of disk models to the visibilities lead to estimates of the location and shape of gaps and rings, the flux in each disk component, and the size of the disk. The dust substructures occur across a wide range of stellar mass and disk brightness. Disks with multiple rings tend to be more massive and more extended. The correlation between gap locations and widths, the intensity contrast between rings and gaps, and the separations of rings and gaps could all be explained if most gaps are opened by low-mass planets (super-Earths and Neptunes) in the condition of low disk turbulence (α = 10−4). The gap locations are not well correlated with the expected locations of CO and N2 ice lines, so condensation fronts are unlikely to be a universal mechanism to create gaps and rings, though they may play a role in some cases.

The Contractile Apparatus Is Essential for the Integrity of the Blood-Brain Barrier After Experimental Subarachnoid Hemorrhage

Development of vasogenic brain edema is a key event contributing to mortality after subarachnoid hemorrhage (SAH). The precise underlying mechanisms at the neurovascular level that lead to disruption of the blood-brain barrier (BBB) are still unknown. Activation of myosin light chain kinases (MLCK) may result in change of endothelial cell shape and opening of the intercellular gap with subsequent vascular leakage. Male C57Bl6 mice were subjected to endovascular perforation. Brain water content was determined by wet-dry ratio and BBB integrity by Evans-Blue extravasation. The specific MLCK inhibitor ML-7 was administered to the mice to determine the role of the contractile apparatus of the neurovascular unit in determining brain water content, BBB integrity, neurofunctional outcome, brain damage, and survival at 7 days after SAH. Inhibition of MLCK significantly reduced BBB permeability (Evans Blue extravasation − 28%) and significantly decreased edema formation in comparison with controls (− 2%). MLCK-treated mice showed reduced intracranial pressure (− 53%), improved neurological outcome at 24 h and 48 h after SAH, and reduced 7-day mortality. Tight junction proteins claudin-5 and zonula occludens-1 levels were not influenced by ML-7 at 24 h after insult. The effect of ML-7 on pMLC was confirmed in brain endothelial cell culture (bEnd.3 cells) subjected to 4-h oxygen-glucose deprivation. The present study indicates that MLCK contributes to blood-brain barrier dysfunction after SAH by a mechanism that does not involve modulation of tight junction protein levels, but via activation of the contractile apparatus of the endothelial cell skeleton. This underlying mechanism may be a promising target for the treatment of SAH.

Copper compound deposition for decreasing electrical insulation in aged oil-filled cables

Copper compounds, such as copper sulfide, are aggregated and deposited at specific locations on insulating paper in aged oil-filled cables via oil flow and dielectrophoresis. Thus, the depositions produce various black shapes such as straight lines along oil gap, spots, and tree-like shapes. Herein, the deposition of copper compounds and the effect on electrical insulation were investigated for each deposited shape using Fourier-transform infrared spectroscopy, Raman spectroscopy, and energy dispersive X-ray spectrometry. The results indicate that copper compounds deposit on all shapes, whereas copper sulfide deposits only on some portions of the shapes. Moreover, the electric charging degradation sites show low insulation performance because of having a starting point of partial discharge. In other words, an analysis of aged cables revealed that this deposition phenomenon was a type of oil-filled cable degradation.

Numerical methods for contact analysis of complex-shaped bodies with account for non-linear interface layers

In order to ensure high technical characteristics of machines for various applications, it is necessary to increase the strength of the most loaded and heavy-duty elements of constructions, which are complex-shaped components under intense contact loads. When bodies get in contact over surfaces of close shape, new factors that have not been taken into account before come into play. In particular, nonlinear contact stiffness of the surface layers of the components is among them. Accordingly, nonlinear components appear in impenetration contact conditions instead of traditional linear ones. To study the contact interaction with account for such constraints, a new method for stress-strain state analysis and structural strength design of various machine parts has been developed on the basis of a modification of the Kalker’s variational principle. Nonlinear models of the material behavior of the surface layers of contacting complex-shaped bodies were created and applied. The discretization of the resulting mathematical problem was performed with the help of the developed version of the boundary element method. The developed models of contact interaction combine physical and structural nonlinearities. This provides more accurate modelling of stress-strain state of contacting complex-shaped bodies in comparison with conventional approaches. The peculiar variation of the contact pressure distribution with the change of the gap shape and the properties of the interface layer between the contacting bodies were studied on this basis. It is possible to derive more relevant recommendations to justify design and technological solutions with account for the results of such analysis. Eventually, this will enhance the technical characteristics of machines of various applications

First principles phase diagram calculation for the 2D TMD system [formula omitted

First principles phase diagram calculations, that included van der Waals interactions, were performed for the bulk transition metal dichalcogenide system (1−X)·WS2−(X)·WTe2. To obtain a converged phase diagram, a series of cluster expansion calculations were performed with increasing numbers of structural energies, (Nstr) up to Nstr=435, used to fit the cluster expansion Hamiltonian. All calculated formation energies are positive and all ground-state analyses predict that formation energies for supercells with 16 or fewer anion sites are positive; but when 150⪅Nstr⪅376, false ordered ground-states are predicted. With Nstr≥399, only a miscibility gap is predicted, but one with dramatic asymmetry opposite to what one expects from size-effect considerations; i.e. the calculations predict more solubility on the small-ion S-rich side of the diagram and less on the large-ion Te-rich side. This occurs because S-rich low-energy metastable ordered configurations have lower energies than their Te-rich counterparts which suggests that elastic relaxation effects are not dominant for the shape of the miscibility gap.

An optimization method for flexural bearing design for high-stroke high-frequency applications

A method for optimization of a high-stroke, high-frequency flexural bearing was completed. The main goal was to design a flexural bearing system as the energy restoration component of a one kW free piston linear engine alternator (LEA) operating at 90 Hz and maximum targeted displacement of 22 mm. Defined electricity output of 1 kW, with more than 30% efficiency, required engine operation under high speed and high stroke conditions. Under such challenging stroke and frequency requirements, a method of design was required to select between a wide range of parameters in flexural bearing design. A parametric CAD model was prepared and used in the optimization package of a finite element analysis (FEA) software. Four main parameters of flexural bearing geometry were identified and included the outer diameter, thickness, number of arms, and sweep angle of spiral cuts. Other design parameters including spiral gap width, shape factor and spiral start points angle were shown to be less important compared to these four main parameters in primary design and were examined separately. A neural network algorithm was used to investigate the interactions and effects of design parameters. The sensitivity of each parameter on output criteria such as maximum stress and natural frequency was examined and design charts developed. Methods for further modification of the spiral curve at end points were introduced to reduce the maximum stress level by up to 20%. Several steel alloys and a titanium-based alloy were identified as proper material candidates for high cycle applications and the final designed spring was manufactured and tested to validate the FEA results of axial stiffness and strain level throughout the flexure arms. The percent of the flexure’s moving mass was estimated to be 29% with FEA analysis and compared well with the experimental value of 31%. The stress/strain results of the FEA analysis matched with the experimental results – within ±5%.

Palaeogeological hiatus surface mapping: a tool to visualize vertical motion of the continents

AbstractDynamic topography is a well-established consequence of global geodynamic models of mantle convection with horizontal dimensions of >1000 km and amplitudes up to 2 km. Such physical models guide the interpretation of geological records on equal dimensions. Continent-scale geological maps therefore serve as reference frames of choice to visualize erosion/non-deposition as a proxy for long-wavelength, low-amplitude vertical surface motion. At a resolution of systems or series, such maps display conformable and unconformable time boundaries traceable over hundreds to thousands of kilometres. Unconformable contact surfaces define the shape and size of time gap (hiatus) in millions of years based on the duration of time represented by the missing systems or series. Hiatus for a single system or series base datum diminishes laterally to locations (anchor points) where it is conformable at the mapped resolution; it is highly dependent upon scale. A comparison of hiatus area between two successive system or series boundaries yields changes in location, shape, size and duration, indicative of the transient nature of vertical surface motion. As a single-step technique, it serves as a quantitative proxy for palaeotopography that can be calibrated using other geological data. The tool magnifies the need for geological mapping at the temporal resolution of stages, matching process rates. The method has no resolving power within conformable regions (basins) but connects around them. When applied to marine seismic sections that relate to rock record, not to time, biostratigraphic and radiometric data from deep wells are needed before hiatus areas – that relate to time – can be mapped.

Increasing the bandwidth of an extended interaction klystron at 0.34 THz by staggered tuning of the multi-gap cavities

To increase the bandwidth of EIKs at 0.34 THz, a synthetical method containing several steps is proposed. As the crucial unit determining the performance of EIKs, the output cavity is studied. Based on the theory of space charge wave, the number of gaps in the output cavity is optimized to increase both the interaction efficiency and the instantaneous bandwidth. The approaches of tuning the shape of a barbell gap and the number of gaps in idler cavities are studied, leading to the practicable method of staggered tuning on all the intermediate cavities. As a result, the bandwidth of an EIK is improved step by step. Another approach of adjusting the drift tubes is also discussed and the synthetically tuning strategy for terahertz EIKs is concluded. Finally, the optimized nonuniform structure is verified by PIC simulations and the results show that it can effectively broaden the −3 dB bandwidth up to 500 MHz, which is double that of the uniform structure. The synthetical method is proved to be practicable in tuning the bandwidth and capable to keep the device operating in stability.

PERBANDINGAN SUHU PENYIMPANAN ELEKTRODA TERHADAP KEKERASAN BAJA KARBON

The welding is the process of connecting two metals, where factors that
 influence are current, voltage, plate thickness, gap shape and heating temperature
 of the electrode. The heating of this electrode aims to stabilize the arc arising
 during welding.
 The objective of the study was to determine the maximum hardness of low
 carbon steel welding with E 7018, with temperature of electrode storage at
 temperature 50, 75 and 100 ° C. Determine the maximum change in the hardness
 of the welded by using heated electrodes preheated to an initial temperature of 50,
 75 and 100 ° C. Compare its hardness to the standard. The specimen-making
 method is based on JIS Z 3121, further data are compared against the standard.
 The result of maximum hardness value for slit I is 175HV and for slit V
 264HV in weld area with temperature 75 ° C, hardness change of 33HV for
 temperature 100 °C.

Using ducted fuel injection to attenuate or prevent soot formation in mixing-controlled combustion strategies for engine applications

Ducted fuel injection is a strategy that can be used to enhance the fuel/charge-gas mixing within the combustion chamber of a direct-injection compression-ignition engine. The concept involves injecting the fuel through a small tube within the combustion chamber to make the most fuel-rich regions of the micture in the autoignition zone leaner relative to a conventional free-spray configuration (i.e., a fuel spray that is not surrounded by a duct). This study is a follow-on to initial proof-of-concept experiments that also were conducted in a constant-volume combustion vessel. While the initial natural luminosity imaging experiments demonstrated that ducted fuel injection lowers soot incandescence dramatically, this study adds a more quantitative diffuse back-illumination diagnostic to measure soot mass, as well as investigates the effects on performance of varying duct geometry (axial gap, length, diameter, and inlet and outlet shapes), ambient density, and charge-gas dilution level. The result is that ducted fuel injection is further proven to be effective at lowering soot by 35–100% across a wide range of operating conditions and geometries, and guidance is offered on geometric parameters that are most important for improving performance and facilitating packaging for engine applications.

Control of optical nanometer gap shapes made via standard lithography using atomic layer deposition

Atomic layer deposition is an efficient method for coating a few nanometer-thick alumina over a wafer scale. This method combined with the standard photolithography process was presented to fabricate metallic nanometer gaps that optically act in terahertz regimes. However, the cross-sectional view of the gap shape of the metal–insulator–metal nanogap structure varies depending on the conditions from the stepwise procedure. In specific, selecting photoresist materials, adding ion milling and chemical etching processes, and varying metal thicknesses and substrates result in various optical gap widths and shapes. Since the cross-sectional gap shape affects the field enhancement of the funneled electromagnetic waves via the nanogap, the control of tailoring the gap shape is necessary. Thus, we present five different versions of fabricating quadrangle-ring-shaped nanometer gap arrays with varying different kinds of outcomes. We foresee the usage of the suggested category for specific applications.

Fatigue Behavior Investigation and Stress Analysis for Rib-to-Deck Welded Joints in Orthotropic Steel Decks

The fatigue problems in orthotropic steel decks have raised widely concerns in recent years. This study focused on the root crack mechanism at rib-to-deck welded joints, based on the previous test results of sectional specimens and the matching FE analysis, the fatigue behaviors of structure detail were investigated by considering the effect of root gap shapes, weld penetrations, and plate thicknesses on crack initiation. Besides, various root crack depths were simulated in models to clarify the stress variations occurring during the propagation stage under cyclic loading. The results showed that the root gap shape and penetration rate have an impact on the root cracking direction and fatigue life at the initiation stage, but seem not directly related to the crack propagation mechanism; the higher penetration rate is advantageous for the prevention of root crack initiation. However, although the stiffness increased with the increase in plate thickness, the fatigue life of crack initiation might be reduced owing to the low fatigue strength of the thick deck plate, whereas the U-rib thickness has limited effect on the stress response of the root tip. Moreover, the significant difference between the 8 mm-crack model and other crack models is the high stress concentration around the crack tip. The stress conditions of root tip would be changed under loading cycles when a root crack propagated into half of deck plate thickness. Finally, the effect of structural dimensions on fatigue strength were also compared according to test results and FEA.

Magneto-electronic and thermoelectric properties of some Fe-based Heusler alloys

We present electronic, magnetic and transport properties of some 24-valence-electron semiconducting Heusler alloys obtained by first principles and use of Boltzmann theory. The spin-resolved electronic structures show that the materials are semiconductors in both spin channels and that they follow the ZT − 24 Slater–Pauling rule in the Fm3¯m phase. In Fe2TiSi, Fe2TiGe and Fe2ZrSi, the shape and size of the band gap is mainly determined by d–d hybridization between the d-states of transition metal atoms Ti (Zr) and Fe. Decreasing covalent character in bonding is observed when Y and Z atoms are replaced by the corresponding atoms lower in the group. The transport properties predict the materials to have p-type character, with electrical conductivity and the Seebeck coefficient having a semiconductor-like nature in all three compounds studied. The large Seebeck coefficients at room temperature strongly support the possible application of these materials as thermoelectric materials.