Zone Of Holes Research Articles

Теплопровідність твердих розчинів GeBiTe

The paper calculates the electronic and lattice components of thermal conductivity coefficients for GeBiTe solid solutions. The calculation was carried out using two different models of the band structure of GeTe, which differ in the relative location of the zones of heavy and light holes. The first of the models is generally accepted for A4B6 compounds and assumes the location of the zone of light holes above the zone of heavy ones in the energy spectrum. Another model, obtained on the basis of DFT calculation, predicts the location of the zone of light holes below the zone of heavy ones. A significant difference was established in the numerical values of the electronic and lattice components of the thermal conductivity coefficients, depending on the adopted model. The influence of other calculation parameters on the investigated values was analyzed.

АНАЛИЗ ХАРАКТЕРИСТИК НАПРЯЖЕННО-ДЕФОРМИРОВАННОГО СОСТОЯНИЯ КОМЛЕВОЙ ЧАСТИ ЛОПАСТИ НЕСУЩЕГО ВИНТА ВЕРТОЛЕТА

The butt part of the main rotor blade (RB) of the helicopter is presented. A geometric model of the calculated connection was developed using the CATIA V5 system. With the help of the ANSYS system, a finite element model of the butt part of the main rotor blade was developed, and the calculation and analysis of the characteristics of the results obtained were carried out. To describe the response of materials to an external action, a model of an elastically deformable isotropic body was used with the assignment of the corresponding elastic constants of the material. The case of loading a bolted joint by a centrifugal force arising during the rotation of a blade is considered. To model the contact interaction, a generalized surface-to-surface contact interaction model was adopted. The analysis of the calculation results includes the determination of reactions at the attachment points, the values of the maximum displacements of structural elements and stresses in the stress concentration zones. In the course of the calculation, reactions were determined at the points of attachment of the tip along the holes in the lugs. The nature of the deformation of the bolted joint as a whole and of its individual elements is analyzed. The assessment of total displacements and displacement components is carried out. To assess the static and fatigue strength of the elements of the bolted connection of the tip with the blade spar, the stresses in the load-bearing elements were analyzed for typical concentrators. When assessing the static strength, the distribution of equivalent stresses according to Mises was analyzed. The distribution of stresses in the zone of holes along the rows is analyzed, starting from the root section in the direction of increasing the Y coordinate. The maximum von Mises stresses for typical stress concentration zones were compared with the ultimate strength of the structural element material. To assess the fatigue strength, we analyzed the distribution of the main tensile stresses in the load-bearing elements by typical stress concentrators. The maximum values of these stresses were compared with the fatigue limit of the structural element material.

Study on picosecond laser processing of blind holes in carbon fiber-reinforced plastics

In view of the rough and sunken bottom of blind hole during the laser processing on carbon fiber-reinforced plastics (CFRP), a processing experiment with different hatch distance is conducted by picosecond laser, and the numerical simulation is carried out by COMSOL. The effects of scanning path distribution of hatch distance with equal and variable hatch distance in the processing depth, heat-affected zone and bottom micro-morphology of blind holes are studied. The results show that the variable hatch distance machining path can make heat more uniform on the material, so that the concave effect of the inner ring bottom is weakened. Moreover, the variable hatch distance path can reduce the fiber breakage and resin residue of blind holes, and enhance the physical performance of the structure. When the processing path is three sets of concentric circles with 70 µm innermost hatch distance and 100 µm outermost hatch distance, the machining depth can be achieved, and high-quality blind hole can be obtained under the premise of smaller heat-affected zone and borehole taper.

Histological Evaluation of Early-Phase Changes in the Osteochondral Unit After Microfracture in a Full-Thickness Cartilage Defect Rat Model

Background: The microfracture (MF) technique is an established surgical treatment for cartilage injury. However, the early-phase histological changes in full-thickness cartilage defects (FTCDs) after MF and the concomitant changes in the subchondral bone are still unknown. Purpose: To determine the early-phase histological changes in FTCD associated with subchondral bone remodeling after MF in rat model. Study Design: Controlled laboratory study. Methods: Rats were subjected to FTCD, followed by MF at the trochlear groove. For histological analysis, experiment and untreated control rats were sacrificed at 0, 1, 3, 7, 14, 28, and 56 days postoperatively (n = 6 knees per time point). Cartilage healing response was evaluated with the Pineda score. Osteoclast activity was evaluated by counting and locating the number of tartrate-resistant acid phosphatase (TRAP)–positive cells in the subchondral bone. MF hole diameter and bone mineral density in the subchondral bone were measured sequentially in 3 rats (n = 6 knees) by 3-dimensional μ–computed tomography. Results: Pineda score showed no difference in cartilage response from day 0 to day 3 but a significant improvement from day 7 to day 56. Although the MF holes were filled with blood clots in all specimens, the defect sites were not. The number of TRAP-positive cells peaked at day 3, mostly accumulating around the deeper zone of the MF holes. Over time, the number of TRAP-positive cells decreased to preoperative levels, localizing around the aperture of the MF holes where there was active remodeling of the osteochondral unit. The MF hole diameter was largest at day 14, and most holes disappeared by day 28. Bone mineral density was also highest at day 14 and decreased to preoperative levels by day 56. Conclusion: Histological changes in the FTCD after MF were derived from endochondral ossification within the deeper zone of the MF holes. Clinical Relevance: The absence of healing by blood clot in the FTCD should be noted by surgeons performing MF, and indications for MF should be carefully considered not only for maximizing the postoperative clinical outcome but also minimizing potential complications, such as formation of subchondral bone cysts or intralesional osteophytes.

Evolution of geometric and quality features during ultrasonic vibration-assisted continuous wave laser surface drilling

Recently, the processes involving simultaneous application of ultrasonic vibrations during conventional materials processing are attracting significant interests for improving process efficiency and material quality. It has been previously shown that the simultaneous application of ultrasonic vibrations (frequency of 20kHz and vibration displacement of 23μm) during continuous wave (CW) CO2 laser surface melting results in melt expulsion and formation of surface holes. In this paper, a systematic evolution of geometric features (hole depth, diameter, aspect ratio, and taper) and quality parameters (material build-up, spatter, recast layer thickness, and heat affected zone) of holes with laser irradiation time (0.05, 0.1, 0.2, 0.25, 0.35, 0.75, and 1.25s) for the ultrasonic vibration-assisted CW CO2 laser surface drilling of AISI 316 stainless steel is investigated. Also, a multi-step finite element analysis, taking into account the observations of melt expulsion from high speed photography, is presented for the prediction of laser drilled hole volume. The results indicate that the laser melting regime of the continuous wave laser-material interactions can be extended for drilling of materials, expanding the applications of these widely used lasers for flexible manufacturing.

Efficient single light-emitting layer pure blue phosphorescent organic light-emitting devices with wide gap host and matched interlayer

In this work, we report the highly efficient pure blue electroluminescent (EL) device based on bis[(3,5-difluoro-4-cyanophenyl)pyridine]picolinate iridium(III) (FCNIrpic) doped 9-(4-tert-Butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole (CzSi) film. The matched energy levels of FCNIrpic and CzSi are helpful in facilitating the trapping of carriers, while the high triplet energy of CzSi can well avoid the undesired reverse energy transfer. More importantly, the injection of holes was further accelerated by inserting 5nm 4,4′,4″-Tri(9-carbazoyl)triphenylamine (TcTa) film between hole transport layer and lighting-emitting layer (EML) as interlayer. Consequently, EL performances were significantly enhanced attributed to wider recombination zone and better balance of holes and electrons. Interestingly, single-EML device displayed higher performances than those of double-EMLs device. Finally, pure blue EL device with the structure of ITO/MoO3 (3nm)/TAPC (40nm)/TcTa (5nm)/FCNIrpic (20%): CzSi (30nm)/TmPyPB (40nm)/LiF (1nm)/Al (100nm) realized the maximum brightness, current efficiency, power efficiency and external quantum efficiency up to 12,505cd/m2, 36.20cd/A, 28.42lm/W and 16.9%, respectively. Even at the high brightness of 1000cd/m2, current efficiency and external quantum efficiency up to 17.40cd/A and 8.1%, respectively, can be retained by the same device.

Smooth horizons and quantum ripples

Black holes are unique objects which allow for meaningful theoretical studies of strong gravity and even quantum gravity effects. An infalling and a distant observer would have very different views on the structure of the world. However, a careful analysis has shown that it entails no genuine contradictions for physics, and the paradigm of observer complementarity has been coined. Recently this picture was put into doubt. In particular, it was argued that in old black holes a firewall must form in order to protect the basic principles of quantum mechanics. This AMPS paradox has already been discussed in a vast number of papers with different attitudes and conclusions. Here we want to argue that a possible source of confusion is the neglect of quantum gravity effects. Contrary to widespread perception, it does not necessarily mean that effective field theory is inapplicable in rather smooth neighbourhoods of large black hole horizons. The real offender might be an attempt to consistently use it over the huge distances from the near-horizon zone of old black holes to the early radiation. We give simple estimates to support this viewpoint and show how the Page time and (somewhat more speculative) scrambling time do appear.

In-plane light emission of organic light-emitting transistors with bilayer structure using ambipolar semiconducting polymers

The concept of using an ambipolar bilayer semiconducting heterostructure in organic light-emitting transistors (OLETs) is introduced to provide a new approach to achieve surface emission. The properties of top-gate-type bilayer OLETs with ambipolar materials based on two types of fluorene-type polymers used as an emissive layer and an electron blocking layer are investigated. Line-shaped yellow–green emission occurs near a hole-injection electrode. When hole transport is dominant in the upper layer which acts as an electron blocking layer, and electrons are injected into the lower layer, an in-plane light-emitting pattern is observed. The measured in-plane emission zone confirms that both hole and electron transport are determined to occur mainly along the different organic layers between the source and drain electrodes, and an in-plane recombination zone of electrons and holes exists near the bilayer organic interface. This work is anticipated to be useful for the development of in-plane light-emitting transistors.

Histological analysis of failed cartilage repair after marrow stimulation for the treatment of large cartilage defect in medial compartmental osteoarthritis of the knee.

Bone marrow-stimulating techniques such as microfracture and subchondral drilling are valuable treatments for full-thickness cartilage defects. However, marrow stimulation-derived reparative tissues are not histologically well-documented in human osteoarthritis. We retrospectively investigated cartilage repairs after marrow stimulation for the treatment of large cartilage defects in osteoarthritic knees. Tissues were obtained from patients who underwent total knee arthroplasty (TKA) after arthroscopic marrow stimulation in medial compartmental osteoarthritis. Clinical findings and cartilage repair were assessed. Sections of medial femoral condyles were histologically investigated by safranin O staining and anti-type II collagen antibody. Marrow stimulation decreased the knee pain in the short term. However, varus leg alignment gradually progressed, and TKA conversions were required. The grade of cartilage repair was not improved. Marrow stimulations resulted in insufficient cartilage regeneration on medial femoral condyles. Safranin O-stained proteoglycans and type II collagen were observed in the deep zone of marrow-stimulated holes. This study demonstrated that marrow stimulation resulted in failed cartilage repair for the treatment of large cartilage defects in osteoarthritic knees. Our results suggest that arthroscopic marrow stimulation might not improve clinical symptoms for the long term in patients suffering large osteoarthritic cartilage defects.

Numerical analysis of the long-term strength of the rotor disks of steam turbines

We present the results of numerical analyses (in the three-dimensional statement) of the kinetics of stressed state and accumulation of dispersed defects in the zone of discharge holes in the rotor disks of a steam turbine in creep for 400,000 h. It is shown that the zones of discharge holes in the disks of the first two stages suffer the action of the highest stresses and the material in these zones is damaged more intensely that near the surface of the axial channel.

Influence of filter ventilation on the chemical composition of cigarette mainstream smoke

Total yields of cigarette smoke constituents are greatly influenced by smoking behaviour, the tobacco blend as well as a variety of cigarette design parameters. Thereby, filter ventilation, i.e. diluting the smoke by providing a zone of microscopic holes around the circumference of the filter is one method to reduce the yield of ‘tar’ and other smoke compounds. However, little is known how these design variations influence the combustion conditions, and therefore, the overall chemical pattern of the smoke. In this paper single photon ionization-time-of-flight mass spectrometry (SPI-TOFMS) is used to characterize and compare cigarettes on a puff-by-puff basis, which differ only in filter ventilation magnitude. The research cigarettes investigated were made from Virginia tobacco and featured filter ventilations of 0% (no ventilation), 35%, and 70%. The cigarettes were smoked under two different puffing regimes, one using the puffing parameters of the conventional International Organization for Standardization (ISO) smoking regime and a more intense smoking condition. Results show that every variation entails a change of the chemical pattern, whereby, in general, cigarettes with 0% filter ventilation as well as the intense smoking regime lead to a more complete combustion compared to the ISO smoking conditions and the high ventilated cigarettes. Changes in the overall patterns can also be observed during the smoking for individual puffs. Some substances dominate the first puff, some species are more pronounced in the middle puffs, whereas others are preferably formed in the last puffs. This demonstrates the high complexity of the occurring processes. Results might help to understand the formation and decomposition reactions taking place when a cigarette is smoked and offer scope for targeted reduction strategies for specific toxicants or groups of toxicants in the smoke.

Influence of heat treatment on microstructure and hot crack susceptibility of laser-drilled turbine blades made from René 80

Turbine components from conventionally cast nickel-base alloy René 80 show different hot cracking susceptibilities depending on their heat treatment conditions leading to slightly different microstructures. Electron probe micro-analysis, focused ion beam technique and analytical transmission electron microscopy were applied to reveal and identify grain boundary precipitates and the γ–γ′-microstructure. The distribution of borides along grain boundaries was evaluated statistically by quantitative metallography. The following features could be correlated with an increase of cracking susceptibility: i) Increasing grain size, ii) increasing fraction of grain boundaries with densely spaced borides, iii) lack of secondary γ′-particles in matrix channels between the coarse cuboidal γ′-precipitates. The latter feature seems to be responsible for linking-up of cracked grain boundary precipitates which occurred as an additional cracking mechanism after one heat treatment, whereas decohesion at the boride-matrix-interface in the heat affected zone of laser-drilled holes was observed for both heat treatments.

Investigation of the recombination zone in the structure of red organic electroluminescent devices

A hole-blocking layer (HBL) is used to obtain red organic electroluminescence (OEL) from 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-8-yl) vinyl]-4H-pyran (DCM2) fluorescent dye. Indium tin oxide (ITO) was used as a glass substrate and N, N′-bis-(1-naphthyl)- N, N′-diphenyl-1,1-biphenyl-4-4′-diamine (NPB) as a hole transport layer and an emissive layer. DCM2, as a red fluorescent dye, was doped into the NPB layer. Bathocuproine (BCP) was used as a hole-blocking layer (HBL); tris-(8-hydroxy-quinoline) aluminum (Alq 3) was used in the electron transport layer, and aluminum (Al) was used as a cathode in red organic electroluminescent (OEL) devices with the configuration ITO/NPB (30 − x nm)/NPB:DCM2 (1.5 nm)/NPB ( x nm)/BCP (30 nm)/Alq 3 (40 nm)/Al. BCP acted as HBL, sp the electrons and holes recombine in the NPB:DCM2 layer. Accordingly, the OEL device emits red light by energy transfer from NPB to DCM2. The recombination zone of electrons and holes was investigated by varying the NPB:DCM2 location in the OEL device. This investigation indicates that the optimum thickness of the carrier recombination zone was x = 0∼3 nm, as measured from the interface of the BCP layer.

Preparation and Characterization of Organic Electroluminescent Devices Using Fluorescent Polyimides as a Light-Emitting Layer

The electroluminescence (EL) properties of the organic electroluminescent devices (OELDs) using three kinds of fluorescent polyimides, ODPA/DCHM (HFPI-1), 10FEDA/DCHM (HFPI2), and P2FDA/DCHM (HFPI-3), for light emitting layers were investigated. The HOMO energy levels of HFPI-1 and HFPI-2 were determined as 6.7 and 6.9 eV, respectively, using cyclic voltammetry. Single-layer EL devices having the ITO/HFPI/Al structure were fabricated using HFPI-1 and HFPI-2, but these devices did not exhibit any current and EL properties. This is due to the quite large energy gaps between ITO (work function: 4.7 eV) and the HOMO levels of polyimides (>2.0 eV). Further, multilayer devices were fabricated using carrier transport materials. For these devices, the carrier injection properties from both electrodes were expected to be improved. However, no current and EL properties were observed for all devices. These experimental facts indicate that fluorescent polyimides have little carrier transportability. The EL properties of the devices using TPD-dispersed fluorescent poly-imides as hole transport layers were also investigated. In case of using HFPI-3 whose excitation spectrum is overlapped with the emission of Alq3, the device emits a distinct EL at 520 nm under the operation at 15 V. Further, the emission was displaced to 560 nm under the operation at 30 V, which can be explained by the energy transfer to HFPI-3 or the displacement of the recombination zone of electrons and holes from Alq3 to HFPI-3+TPD layer. This device mechanism might be promising as a novel wavelength-tunable OELD.

Impact response of 3‐D woven composites reinforced by consolidated rods

AbstractThis paper examines the impact response of three‐dimensionally woven fabric composites using consolidated rods in the axial direction. The material processing includes fabrication of the 1‐mm rods by pultrusion, formation of the fabrics, and impregnation of the resin. A weaving setup incorporating the rods in the axial direction has been developed. Using the setup, three types of orthogonal fabrics with varying the tow sizes have been made. The microgeometry of yarns and the distribution of fibers were examined. Impact tests were carried out using an instrumented drop‐weight impactor. Matrix cracks and rod debonding are the principal damage modes on the top and bottom surfaces. However, the crack configurations on these surfaces are very different. Formation of these damage modes and the associated influencing factors have been discussed. One feature not found in conventional composites is rod pull‐in, which is a result of rod debonding and sliding. The pull‐in creates a zone of holes on the specimen edge, revealing how the stress wave propagates from the impact to the non‐impact sides. It is found that the pull‐in is more pronounced near the non‐impact side. The load‐time and energy‐time histories have been examined and related to how the specimens respond to the impact.

Geochemistry and isotope systematics of sulphur in the mixing zone of Bahamian blue holes

A profile of aqueous S species concentrations and stable isotope compositions is presented for the mixing zone of Cousteau's Blue Hole, North Andros, Bahamas, together with similar, but less detailed results from two other blue holes. These data show that S 0 and S 2− are produced by bacterially mediated sulphate reduction near the base of the mixing zone and that these species are reoxidized at shallower levels. Acidity generated by oxidation can contribute to corrosion of limestone wall-rock. Estimated rates of such corrosion range up to 1200 mm wall-rock recession per 10 ka at Cousteau's Blue Hole (equivalent to 16% porosity generation per 10 ka) and are comparable with rates of dissolution caused by inorganic mixing corrosion.

Early reduction of the burst hazard of a coal seam by hydroseparation

1. In the influence zone of hydroseparation holes, where aquatic solutions of hydrochloric acid and surfactants were used as the working fluid, no gas-dynamic phenomena occurred during the course of drifting. Hazard indicators R1 and K1 had values below the critical. 2. The use of aqueous solutions of hydrochloric acid and surfactants provided uniform wetting of the coal seam. Because the holes were not developed, there was an increase of excessive moisture content in the seam by 1.1–1.9%, and reduced gas permeability. 3. The coal hardness decreased insignificantly as the working advanced into the hydroseparation zone. The drainage of the seam restored it to the level of untreated mass. 4. The yield of drilling fines from the holes showed that the hydroseparation of burst-hazardous coal seams by water solutions of hydrochloric acid and surfactants loosens the coal seam and slackens the stresses in the face area. 5. The gas permeability of the coal seam after hydraulic separation without hole development was slightly increased. In order to enhance the seam permeability, hydroseparation should be followed by drainage and degassing, and, before the excavation work, additional water should be added to lower the sorption potential of the “coal-working liquid-gas” system. 6. The use of aqueous solutions of 4–6% hydrochloric acid with the addition of 0.1–0.5% noniogenic surfactant ensured a faster antiburst treatment of the coal seam compared to treatment with water alone. 7. The tests have determined that the burst hazard of a thick, gentle sloping coal seam in the hydroseparation zones is reduced, demonstrating that the use of aqueous solutions of hydrochloric acid and surfactants in the Karaganda Basin could allow abandoning local antiburst measures and thus enhance the technicoeconomic efficiency of the operation on development and breakage segments in burst-hazardous seams.

Nonrelativistic dispersional equations for crystals of sphalerite and diamond structure

The tenth- and eleventh-order dispersion equations obtained for sphalerite and diamond structures in previous works are reduced to algebraic form and compared. The dispersion equation for the sphalerite structure is factorized at the axes and in the planes of symmetry. At the axes Δ and Λ the factorization is complete; the zones of heavy and light holes are the same as in the diamond structure. At the axes gS only a zone of heavy holes is isolated, which is again no different from that obtained from the diamond structure. Factorization of the equations for both structures in the whole of the (110) plane is performed.

The Universal Ureteral Stent

AbstractThe universal ureteral stent is an 8F soft silicone rubber tube 90cm. long with a zone of side holes marked with radiopaque material. This stent does not cause the discomfort associated with other ureteral stents and can provide immediate nephrostomy drainage if obstruction occurs. The universal stent is reasonably priced, and because only 1 size stent is needed, which has several applications, the size and cost of hospital stent inventories should be decreased.

The Universal Ureteral Stent

Abstract: The universal ureteral stent is an 8F soft silicone rubber tube 90cm. long with a zone of side holes marked with radiopaque material. This stent does not cause the discomfort associated with other ureteral stents and can provide immediate nephrostomy drainage if obstruction occurs. The universal stent is reasonably priced, and because only 1 size stent is needed, which has several applications, the size and cost of hospital stent inventories should be decreased.