Internal Hole Research Articles

An In Silico Study on the Isomers of Pentacene: The Case for Air-Stable and Alternative C22H14 Acenes for Organic Electronics.

Pentacene is one of the most investigated candidates for organic thin film transistor (OTFT) applications over the last few decades even though it unstable in air (Eg = 1.80 eV), owing in part to its planar nature and high charge-transfer mobilities as both a single crystal (35 cm2 V-1 s-1) and as a thin-film (3.0 cm2 V-1 s-1). Until now, picene is the only isomer of pentacene to be investigated for organic electronic applications, due to its greater stability (Eg = 4.21 eV) and high-charge transfer mobility (3.0 cm2 V-1 s-1); even benefiting from oxygen doping. In the present study, a total of 12 fused-ring isomers (including pentacene, picene and ten other structures) of the formula C22H14 were analyzed and investigated for their electronic and optical properties for worth in OTFT applications. We screened several pure and hybrid DFT functionals against the experimental frontier molecular orbitals (FMOs) of pentacene, then deployed Marcus Theory, Koopmans' Theorem and Green's function with the P3 electron propagator variant, for the internal hole reorganization energy, the hole transfer integral (via the "splitting-in-dimer method" at d = 3.0, 3.5, and 4.0 Å), the charge transfer rate constant, and vertical ionization energies. Using these as a basis, we studied pentacene's isomers and found that the four nonplanar structures, namely, benzo[g]chrysene (3), naphtho[c]phenanthrene (7), benzo[c]chrysene (11) and dibenzo[c,c']phenthrene (12), are (I) more stable than pentacene, by up to 2 eV, and (II) have relatively similar ionization energies (7.5-7.6 eV) to those of picene's experimental value (7.51 eV). The largest charge transfer rates at 3.5 Å dimer separations were given by the isomers benzo[b]chrysene 4, naphtha[c]phenanthrene 7, dibenzo[a,c]anthracene 8 and benzo[a]tetracene 10 and found to be 2.92, 1.72, 1.30, and 3.09 × 1014 s-1 respectively. In comparison to that of pentacene (KCT = 3.97 × 1014 s-1), these unusual isomers are thus promising air-stable and alternative candidates for organic electronic applications.

Influence of Spray Drying Conditions on Particle Size and Morphology of Al<sub>2</sub>O<sub>3</sub>/ZrO<sub>2</sub>(3Y) Composite Particles

Zirconia toughened alumina materials are frequently used in biomedical applications due to their enhanced toughness, strength and wear resistance compared to monolithic alumina. In this work, the influence of spray drying conditions is studied on the characteristics of spray-dried Al2O3/ZrO2(3Y) composite particles. The SEM images of composite particles confirm the formation of dense composite particles of round shape without internal holes. The particles of the best morphology of the median diameter of 44 µm were produced by drying the slurry of 70 wt.% solid content with feed rate of 15 ml/min using the drying air with inlet temperature of 210 °C and spraying air with flow rate of 357 l/h.

Observation of Internal Photoinduced Electron and Hole Separation in Hybrid Two-Dimentional Perovskite Films.

Two-dimensional (2D) organolead halide perovskites are promising for various optoelectronic applications. Here we report a unique spontaneous charge (electron/hole) separation property in multilayered (BA)2(MA)n-1PbnI3n+1 (BA = CH3(CH2)3NH3+, MA = CH3NH3+) 2D perovskite films by studying the charge carrier dynamics using ultrafast transient absorption and photoluminescence spectroscopy. Surprisingly, the 2D perovskite films, although nominally prepared as "n = 4", are found to be mixture of multiple perovskite phases, with n = 2, 3, 4 and ≈ ∞, that naturally align in the order of n along the direction perpendicular to the substrate. Driven by the band alignment between 2D perovskites phases, we observe consecutive photoinduced electron transfer from small-n to large-n phases and hole transfer in the opposite direction on hundreds of picoseconds inside the 2D film of ∼358 nm thickness. This internal charge transfer efficiently separates electrons and holes to the upper and bottom surfaces of the films, which is a unique property beneficial for applications in photovoltaics and other optoelectronics devices.

非線形バネの分岐現象を用いたコンクリート異常検出のための打音機構の提案

In the purpose of the development of an automated system to detect cracks and internal holes in the concrete infrastructure, a mechanical system to reproduce hammering tests is highly important. The system is required to provide an effective impact force for the accuracy in acoustic analysis. In the present study, we focused on bifurcation phenomenon of the nonlinear spring system in the form of the buckling instability, proposed a prototype of the hammering system based on the spring dynamics to provide a quick motion of the hammer head and analyzed the energy theoretically.

Competition between excluded-volume and electrostatic interactions for nanogel swelling: effects of the counterion valence and nanogel charge.

In this work the equilibrium distribution of ions around a thermo-responsive charged nanogel particle in an electrolyte aqueous suspension is explored using coarse-grained Monte Carlo computer simulations and the Ornstein-Zernike integral equation theory. We explicitly consider the ionic size in both methods and study the interplay between electrostatic and excluded-volume effects for swollen and shrunken nanogels, monovalent and trivalent counterions, and for two different nanogel charges. We find good quantitative agreement between the ionic density profiles obtained using both methods when the excluded repulsive force exerted by the cross-linked polymer network is taken into account. For the shrunken conformation, the electrostatic repulsion between the charged groups provokes a heterogeneous polymer density profile, leading to a nanogel structure with an internal low density hole surrounded by a dense corona. The results show that the excluded-volume repulsion strongly hinders the ion permeation for shrunken nanogels, where volume exclusion is able to significantly reduce the concentration of counterions in the more dense regions of the nanogel. In general, we demonstrate that the thermosensitive behaviour of nanogels, as well as their internal structure, is strongly influenced by the valence of the counterions and also by the charge of the particles. On the one hand, an increase of the counterion valence moves the swelling transition to lower temperatures, and induces a major structuring of the charged monomers into internal and external layers around the crown for shrunken nanogels. On the other hand, increasing the particle charge shifts the swelling curve to larger values of the effective radius of the nanogel.

Multiscale crack initiator promoted super-low ice adhesion surfaces.

Preventing icing on exposed surfaces is important for life and technology. While suppressing ice nucleation by surface structuring and local confinement is highly desirable and yet to be achieved, a realistic roadmap of icephobicity is to live with ice, but with lowest possible ice adhesion. According to fracture mechanics, the key to lower ice adhesion is to maximize crack driving forces at the ice-substrate interface. Herein, we present a novel integrated macro-crack initiator mechanism combining nano-crack and micro-crack initiators, and demonstrate a new approach to designing super-low ice adhesion surfaces by introducing sub-structures into smooth polydimethylsiloxane coatings. Our design promotes the initiation of macro-cracks and enables the reduction of ice adhesion by at least ∼50% regardless of the curing temperature, weight ratio and size of internal holes, reaching a lowest ice adhesion of 5.7 kPa. The multiscale crack initiator mechanisms provide an unprecedented and versatile strategy towards designing super-low ice adhesion surfaces.

Secured Direction Oriented Forwarding through Minimum Amount of Edge Nodes (SDOF-MEN) Protocol for MANETS

Background/Objectives: A Mobile Ad-Hoc Network is formed with an assembly of mobile nodes. Efficient data transmission with security is the important requirement. Security vulnerabilities like attacks are high in MANET. One of the vital attacks is Black hole attack. Methods/Statistical Analysis: The objective of this article is to transmit data in efficient way and also in secured manner. This paper suggests a Secured Direction Oriented Forwarding through Minimum amount of Edge Nodes (SDOF-MEN) protocol for MANET. By reducing the amount of transmissions the efficiency can be improved. Secured transmission is achieved by identifying and removing Hateful nodes from the network. Findings: The SDOF-MEN Protocol is a method which selects least amount of edge nodes to communicate the data. It picks one particular verge node as following hop, and transmits data to the selected following node only. Hence the routing overhead is completely reduced. Thereby it reduces the amount of path-finding messages. With respect to the location, the information is straightly conveyed through midway nodes, hence the efficiency of the whole network is increased. Some nodes are Hateful nodes which are dropping data packets. It identifies both internal and external black hole nodes and removes from the data transmission process. Applications/Improvements: In this paper the algorithm is simulated using ns-2 simulator and analyzed by measuring the performance parameter Packet Delivery Ratio. The Packet Delivery Ratio can be enriched by removing Hateful node.

A comparative study on the edge states in phosphorene quantum dots and rings

Using the tight-binding Hamiltonian approach, we comparatively investigate the energy spectrums of triangular zigzag phosphorene quantum dots (PQDs) and rings (PQRs), as well as their potential applications. In comparison with the outer edge states in the PQD, new extra inner edge states can be produced in the PQR by its internal hole. A transition from the uncoupled to coupled edge states can be induced by decreasing the width between the outer and inner edges of the PQR. Also, the edge states in PQD/PQR are all anisotropically localized in one side, rather than three sides as in triangular graphene quantum dots (QDs) and rings (QRs). Furthermore, the PQD/PQR energy levels can be anisotropically manipulated by the external electric fields and strains, clearly demonstrating their potential applications in field effect transistors or electromechanical devices. In the meanwhile, we also consider the electron probability distributions corresponding to the different energy levels, clearly exposing the characteristics of the PQD/PQR energy levels. The comparison between the asymmetrical triangular PQDs/PQRs and the symmetrical triangular QDs/QRs in graphene should be instructive for understanding the similar triangular QDs/QRs in other two-dimensional layered materials, as well as other types of QDs/QRs of different shapes.

Well-dispersed palladium nanoparticles on three-dimensional hollow N-doped graphene frameworks for enhancement of methanol electro-oxidation

In this work, palladium (Pd) nanoparticles/three-dimensional hollow N-doped graphene frameworks (HNGF) hybrid catalysts were fabricated by using amine-functionalized poly (glycidyl methacrylate) microspheres-templated HNGF as supporting materials for Pd nanoparticles (NPs). The results demonstrate that the Pd NPs with average sizes of ~5.5nm can be well dispersed on the surfaces of HNGF with internal circular holes of ~400nm. The Pd/HNGF catalysts exhibit high electrocatalytic activity and durability toward methanol electro-oxidation in alkaline medium, compared to Pd/graphene and Pd/carbon.

Fatigue Failure of Electronic Unit Pumps Used in Truck Diesel Engine

Several electronic unit pumps (EUPs) used in the truck diesel engine failed during the trial tests. All the failures occurred at the same location, the fifth thread root on the outer diameter of oil-outlet of EUP. Two typical failed EUPs were analyzed to assess failure causes. Fractographic investigation shows that the fatigue fracture was the dominant failure mechanism of two EUPs. Crack origins of the failed EUPs initiated from the fillet root of the step in the internal hole of oil-outlet and propagated toward the fifth thread root on the outer diameter of oil-outlet. Over-small radius of the root fillet caused a high notch effect, and the presence of porous structure and network nitrides on the nitrided internal hole surface created a “metallurgical stress concentration.” Under the action of the great contact force between the plug and the side wall of internal hole of oil-outlet resulting from the press-fitting the plug, the crack initiated easily at the fillet root. The fillet root of step in the internal hole was almost in the same level with the fifth thread root on the outer diameter of oil-outlet. The fifth thread on the outer diameter of oil-outlet was just corresponding to the first engaged thread inside the nut of oil-pipe matched with the threaded portion of the outer diameter of oil-outlet. This resulted in a maximum axial tensile load on the fifth thread due to pre-tightening the nut of oil-pipe. The crack propagated rapidly toward the fifth thread on the outer diameter under the great axial tensile load to lead to premature fatigue failure of EUP.

Static and dynamic tensile failure characteristics of rock based on splitting test of circular ring

Static and dynamic splitting tests were conducted on ring marble specimens with different internal diameters to study the tensile strength and failure modes with the change of the ratio of internal radius to external radius (ρ) under different loading rates. The results show that the dynamic tensile strength of disc rock specimen is approximately five times its static tensile strength. The failure modes of ring specimens are related to the dimension of the internal hole and loading rate. Under static loading tests, when the ratio of internal radius to external radius of the rock ring is small enough (ρ<0.3), specimens mostly split along the diametral loading line. With the increase of the ratio, the secondary cracks are formed in the direction perpendicular to the loading line. Under dynamic loading tests, specimens usually break up into four pieces. When the ratio ρ reaches 0.5, the secondary cracks are formed near the input bar. The tensile strength calculated by Hobbs' formula is greater than the Brazilian splitting strength. The peak load and the radius ratio show a negative exponential relationship under static test. Using ring specimen to determine tensile strength of rock material is more like a test indicator rather than the material properties.

LONG TERM BEHAVIOR OF CONCRETE MEMBER STRENGTHENED WITH INTERNAL PRESTRESSING SYSTEM

To maintain and retrofit appropriately concrete structures, various strengthening materials and methods have been developed and applied. One of the effective and reliable strengthening method for concrete is an application of the prestressing system. The present study focuses on a strengthening system using an internal anchorage and a prestressing tendon. The strengthening system is acceptable even in relatively narrow workspaces, and also applicable for joints between existing and additional concrete members. In our previous investigations, a static push-out and pull-out tests were performed to examine the load-bearing capacity of the prestressing tendon embedded in the wedge anchor. The test confirmed that the prestressing tendon can be anchored firmly in an internal wedge hole filled with high-strength mortar. Long-term behavior of the strengthened member should be examined to confirm the applicability of the system. The load and deformation of a concrete member subjected to sustained force by the prestressing bar were measured for 1 year. This paper reports the long-term loading test, and discusses the time-dependent properties of the strengthened concrete member. The test result confirms that the loss of prestressing force is negligible for actual applications.

Coexistence of Photonic Bandgap Guidance and Total Internal Reflection in Photonic Crystal Fiber Based on a High-Index Array With Internal Air Holes

We show that both photonic bandgap guidance and modified total internal reflection can simultaneously occur in a chalcogenide–tellurite photonic crystal fiber (PCF) whose cladding is composed of a high-index array with internal regions being air. The coexistence of these two guidance mechanisms is corroborated by numerical simulations based on a plane wave expansion method and an analytical model. Despite being scalar and for high-index contrast material systems, the analytical model can accurately predict the band structures of the PCF. A PCF with seven ring units removed as the fiber core is designed to guide in the 580–950-nm wavelength range by the photonic bandgap effect and in the 2.0–4.6-μm wavelength range by total internal reflection. Such a PCF can be an interesting platform for nonlinear phenomena occurring across the two guidance regions.

Turn-on analysis of silicon insulated gate bipolar transistors with emitter trenches

In this study, we analyzed the turn-on of silicon insulated gate bipolar transistors (IGBTs) with an emitter trench. The tail of collector-to-emitter voltage during turn-on fluctuated when an emitter trench was inserted. Interestingly, the gate-to-collector capacitance of IGBTs with an emitter trench was lower than that without an emitter trench. The internal hole current distribution at the time of the tail of collector-to-emitter voltage was investigated by device simulation. The hole current was diverted, passing adjacent to the emitter trench. It was clarified that the fluctuation in the tail of collector-to-emitter voltage originates from a decrease in PNP transistor gain associated with this change of the hole current path. We demonstrated that this fluctuation in the tail of collector-to-emitter voltage can be suppressed by connecting the emitter trench to a gate electrode.

Effect of Slurry Formulation on Morphology and Flowability of Spray-Dried Alumina/Zirconia Composite Particles

Alumina/zirconia composite materials are widely used for biomedical applications because of their high biocompatibility and good mechanical properties. In this work, the effects of slurry solid content and binder type are studied on the characteristics of spray-dried composite particles. The tap density and particle size of composite particles increase while the compressibility index decreases with increasing solid content of slurry. An analysis of the SEM micrographs of spray-dried particles confirms the formation of dense composite particles of round shape without internal holes with 70 wt.% slurry using PVA+PEG co-binder.

A New Approach for Measurement of Tensile Strength of Concrete

Tensile strength is one of the important mechanical properties of concrete. Indirect methods have been used up till now for its measurement. These methods though widely accepted, do not furnish the true tensile strength of concrete. In this paper, a compression to tensile load transformer device is developed to determine direct tensile strength of concrete. The cubic concrete samples with dimension of 15*19*6 cm containing internal hole with dimension of 75mm is prepared using the mixture of cement, fine sand and water. This model is subjected to direct tensile loading by special loading device. A series of finite element analysis were performed using FRANC2D to analyse the effect of hole diameter on the stress concentration around the hole and to render a suitable criteria for determination of real tensile strength of concrete. Concurrent with direct tensile test, Brazilian test is performed to compare the results of two methods. Results obtained by this test are quite encouraging and shows that the direct tensile strength is clearly lower than the Brazilian test. The dierence between the Brazilian and direct tensile strengths is about 33%.

Numerical Study of the Effect Internal Holes Shapes in Blade Turbine Cooling

As the temperature of combustion gases is higher than the melting temperature of the turbine materials, cooling of turbine parts in a gas turbine engine is necessary. The gap between rotating turbine blades and the stationary shroud provides an unintended flow path for hot gases. Gases that flow through the tip region cause pressure losses in the turbine section and high heat loads to the blade tip. This paper numerically studies the effect of change shapes of internal cooling holes and shows the effect of cooling at the tip of blade. Also measures the effect of pressure effectiveness and temperature distribution at the tip and alone holes channels. In this study, results of change shapes of internal holes to circle, rectangle and triangle shows the circle shape is better in cooling by 45 ℃ and 125℃ when compared with rectangle and triangle shapes respectively. Streamlines results explain that they are very crowded at suction side and decreases at pressure sides and many of streamlines that passed through the gap and mixed with cooled flow. Results show also the temperature distribution alone the holes passages are reduced along them from shelf to tip and the maximum values at entrance region. Finally, the results show when the internal velocity of holes increases, the static temperature decreases in the blade.

Localized Electrochemical Deburring of Cross Hole Using Gelatinous Electrolyte

Burrs are formed in mechanical processes such as cutting and blanking, and can have a number of negative effects, such as reducing product life. Burr removal generally depends on manual treatment methods due to the various shapes and properties of burrs. Deburring is therefore considered a significant issue in terms of achieving efficient production and automation. Electrochemical machining (ECM) is commonly used in the deburring of internal cross holes because of its high efficiency and lack of surface residual stresses. However, in the electrochemical deburring process, stray corrosion may cause loss of machining precision and surface quality. We herein propose a localized electrochemical deburring process using a gelatinous electrolyte to solve the problem of stray corrosion. As the gelatinous electrolyte is in contact with the burr surface without macroscopic liquid flow, electrochemical corrosion is confined to the narrow bounds of the burr. Our results indicate that the proposed process can maintain the original machined precision and surface quality while preventing stray corrosion, which is not possible using traditional ECM.

Anchored boundary conditions for locally isostatic networks

Finite pieces of locally isostatic networks have a large number of floppy modes because of missing constraints at the surface. Here we show that by imposing suitable boundary conditions at the surface the network can be rendered effectively isostatic. We refer to these as anchored boundary conditions. An important example is formed by a two-dimensional network of corner sharing triangles, which is the focus of this paper. Another way of rendering such networks isostatic is by adding an external wire along which all unpinned vertices can slide (sliding boundary conditions). This approach also allows for the incorporation of boundaries associated with internal holes and complex sample geometries, which are illustrated with examples. The recent synthesis of bilayers of vitreous silica has provided impetus for this work. Experimental results from the imaging of finite pieces at the atomic level need such boundary conditions, if the observed structure is to be computer refined so that the interior atoms have the perception of being in an infinite isostatic environment.

Continuum Foam

We consider the simulation of dense foams composed of microscopic bubbles, such as shaving cream and whipped cream. We represent foam not as a collection of discrete bubbles, but instead as a continuum. We employ thematerial point method(MPM) to discretize a hyperelastic constitutive relation augmented with the Herschel-Bulkley model of non-Newtonian viscoplastic flow, which is known to closely approximate foam behavior. Since large shearing flows in foam can produce poor distributions of material points, a typical MPM implementation can produce non-physical internal holes in the continuum. To address these artifacts, we introduce a particle resampling method for MPM. In addition, we introduce an explicit tearing model to prevent regions from shearing into artificially thin, honey-like threads. We evaluate our method's efficacy by simulating a number of dense foams, and we validate our method by comparing to real-world footage of foam.