Refractory equipment for firing aluminum nitride substrates

2020 ◽  
pp. 7-9
Author(s):  
Yu. K. Nepochatov ◽  
P. M. Pletnev ◽  
A. A. Denisova
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
The Body ◽  
Special Design ◽  
High Quality ◽  
Reducing Environment ◽  
Recovery Medium

The features of firing aluminitride substrates, characterized by a high temperature of more than 1800 0С and the presence of a reducing environment, are described. It is shown that the high quality of substrates in parallelism, thermal conductivity, and other properties can be achieved, along with the establishment of optimal firing modes, using a special design of a capsule based on boron nitride, which is a container that consists of a body - a box of rectangular cross section, bottom and plane-parallel dividing plates with supports. To create a local (inside the capsule) clean recovery medium, thorn-groove interlocks between the body and the bottom are provided, filled with a heat-resistant inert powder.

scholarly journals Investigation of the Heteroepitaxial Process Optimization of Ge Layers on Si (001) by RPCVD

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 928
Author(s):  
Yong Du ◽  
Zhenzhen Kong ◽  
Muhammet Toprak ◽  
Guilei Wang ◽  
Yuanhao Miao ◽  
...  
Keyword(s):  
High Temperature ◽  
Buffer Layer ◽  
Layer Thickness ◽  
Growth Temperature ◽  
Crystalline Quality ◽  
Initial Growth ◽  
Two Dimensional ◽  
High Quality ◽  
Reduced Pressure

This work presents the growth of high-quality Ge epilayers on Si (001) substrates using a reduced pressure chemical vapor deposition (RPCVD) chamber. Based on the initial nucleation, a low temperature high temperature (LT-HT) two-step approach, we systematically investigate the nucleation time and surface topography, influence of a LT-Ge buffer layer thickness, a HT-Ge growth temperature, layer thickness, and high temperature thermal treatment on the morphological and crystalline quality of the Ge epilayers. It is also a unique study in the initial growth of Ge epitaxy; the start point of the experiments includes Stranski–Krastanov mode in which the Ge wet layer is initially formed and later the growth is developed to form nuclides. Afterwards, a two-dimensional Ge layer is formed from the coalescing of the nuclides. The evolution of the strain from the beginning stage of the growth up to the full Ge layer has been investigated. Material characterization results show that Ge epilayer with 400 nm LT-Ge buffer layer features at least the root mean square (RMS) value and it’s threading dislocation density (TDD) decreases by a factor of 2. In view of the 400 nm LT-Ge buffer layer, the 1000 nm Ge epilayer with HT-Ge growth temperature of 650 °C showed the best material quality, which is conducive to the merging of the crystals into a connected structure eventually forming a continuous and two-dimensional film. After increasing the thickness of Ge layer from 900 nm to 2000 nm, Ge surface roughness decreased first and then increased slowly (the RMS value for 1400 nm Ge layer was 0.81 nm). Finally, a high-temperature annealing process was carried out and high-quality Ge layer was obtained (TDD=2.78 × 107 cm−2). In addition, room temperature strong photoluminescence (PL) peak intensity and narrow full width at half maximum (11 meV) spectra further confirm the high crystalline quality of the Ge layer manufactured by this optimized process. This work highlights the inducing, increasing, and relaxing of the strain in the Ge buffer and the signature of the defect formation.

scholarly journals A Mapping Literature Review of Medical Cannabis Clinical Outcomes and Quality of Evidence in Approved Conditions in the USA from 2016 to 2019

2021 ◽  
pp. 1-22
Author(s):  
Sebastian Jugl ◽  
Aimalohi Okpeku ◽  
Brianna Costales ◽  
Earl J. Morris ◽  
Golnoosh Alipour-Haris ◽  
...  
Keyword(s):  
Systematic Reviews ◽  
The Body ◽  
Medical Cannabis ◽  
High Quality ◽  
Chronic Noncancer Pain ◽  
High Quality Evidence ◽  
Improved Outcomes ◽  
Noncancer Pain ◽  
Study Setting

In 2017, a National Academies of Sciences, Engineering, and Medicine (NASEM) report comprehensively evaluated the body of evidence regarding cannabis health effects through the year 2016. The objectives of this study are to identify and map the most recently (2016–2019) published literature across approved conditions for medical cannabis and to evaluate the quality of identified recent systematic reviews, published following the NASEM report. Following the literature search from 5 databases and consultation with experts, 11 conditions were identified for evidence compilation and evaluation: amyotrophic lateral sclerosis, autism, cancer, chronic noncancer pain, Crohn’s disease, epilepsy, glaucoma, human immunodeficiency virus/AIDS, multiple sclerosis (MS), Parkinson’s disease, and posttraumatic stress disorder. A total of 198 studies were included after screening for condition-specific relevance and after imposing the following exclusion criteria: preclinical focus, non-English language, abstracts only, editorials/commentary, case studies/series, and non-U.S. study setting. Data extracted from studies included: study design type, outcome definition, intervention definition, sample size, study setting, and reported effect size. Few completed randomized controlled trials (RCTs) were identified. Studies classified as systematic reviews were graded using the Assessing the Methodological Quality of Systematic Reviews-2 tool to evaluate the quality of evidence. Few high-quality systematic reviews were available for most conditions, with the exceptions of MS (9 of 9 graded moderate/high quality; evidence for 2/9 indicating cannabis improved outcomes; evidence for 7/9 indicating cannabis inconclusive), epilepsy (3 of 4 graded moderate/high quality; 3 indicating cannabis improved outcomes; 1 indicating cannabis inconclusive), and chronic noncancer pain (12 of 13 graded moderate/high quality; evidence for 7/13 indicating cannabis improved outcomes; evidence from 6/7 indicating cannabis inconclusive). Among RCTs, we identified few studies of substantial rigor and quality to contribute to the evidence base. However, there are some conditions for which significant evidence suggests that select dosage forms and routes of administration likely have favorable risk-benefit ratios (i.e., epilepsy and chronic noncancer pain). The body of evidence for medical cannabis requires more rigorous evaluation before consideration as a treatment option for many conditions, and evidence necessary to inform policy and treatment guidelines is currently insufficient for many conditions.

Numerical and Experimental Modelling of an Air Flow Field in the Chamber of a Rectangular Cross-Section Contraction

2015 ◽  
Vol 769 ◽  
pp. 161-165
Author(s):  
Vladimira Michalcova ◽  
Sergej Kuznetsov ◽  
Lenka Lausova ◽  
Iveta Skotnicova
Keyword(s):  
Cross Section ◽  
Rectangular Cross Section ◽  
Optimal Shape ◽  
High Quality ◽  
Ansys Fluent ◽  
Experimental Modelling ◽  
Software Models ◽  
Turbulent Characteristics ◽  
Fluent Software ◽  
Enclosed Chamber

The article describes the study of turbulent characteristics in the enclosed chamber of a rectangular corss-section nozzle using numerical calculations. Suitable Ansys Fluent software models were selected based on the measurements results comparison in an aerodynamic tunnel as the fluid exits the nozzle. Special attention is paid to profile velocity near the peripheral wall of the observed enclosed chamber in order to confirm the optimal shape of the contraction and thus take steps towards a high quality velocity field.

Experimental Analysis of Vortex Induced Vibration in the Bladeless Small Wind Turbine

2019 ◽  
Author(s):  
Micha Premkumar Thomai ◽  
Lasoodawanki Kharsati ◽  
Nakandhrakumar Rama Samy ◽  
Seralathan Sivamani ◽  
Hariram Venkatesan
Keyword(s):  
Energy Conversion ◽  
Wind Turbine ◽  
Natural Frequency ◽  
Cross Section ◽  
Vortex Shedding ◽  
Rectangular Cross Section ◽  
The Body ◽  
Test Facility ◽  
Vortex Induced Vibration ◽  
Small Wind Turbine

Abstract Vortex-induced vibration is one of the predominant fundamental concepts for forced oscillation which attracts considerable practical engineering application for energy conversion. In this work, an oscillation of a mast arising as a result of wind force is utilized for energy conversion. The paradigm for energy conversion from vortex-induced vibration in the mast is the bladeless wind turbine. It consists of a rigid mass known as a mast, fixed in the spring of stiffness (k) and allowed to oscillate along the direction of the flow. In this work, four different types of mast have been fabricated and tested. The first is uniform tapered hollow conical mast (MAST1), the cross-section of the second is uniform tapered plus symbol (MAST2), the third is uniform tapered inversed plus symbol (MAST3) and the fourth is uniform tapered simple rectangular cross-section (MAST4). All the masts were fabricated using fiber carbon. The experiments were conducted in a versatile small wind turbine testing facility of Hindustan Institute of Technology and Science, Chennai. This test facility contained an open jet wind tunnel with variable frequency drive and other measuring instruments. The vibration sensor was located in the mast where it experienced a large oscillation in a free stream. In this experiment, an increase in wind velocity led to a terrible change in the amplitude of vibration. A vigorous oscillation was experienced in this mast at this critical frequency, when the natural frequency of the mast was synchronized with the frequency of the vortex shedding and the frequency of the oscillation of the mast. The total force in this oscillation was a summation of the body force due to the mass of the mast and vorticity force that is mainly which was the result of the shedding of the vortices. In this work, extensive studies have been carried out for Reynolds number ranging from 2.5 × 105 to 5.0 × 105. The mast length to diameter ratio of 13 was exposed to various speeds of wind and response was measured. The occurrence of the maximum oscillation in a simple rectangular mast was seen where vortex shedding due to the bluff body was large for constant mass and spring stiffness. The frequency of the oscillation at maximum amplitude of the rectangular cross-section mast was equal to the natural frequency, due to vortices shedding at critical velocity. This demonstrated the appropriateness of the simple rectangular cross-section for harnessing the low rated wind energy and its suitability for renewable energy conversion in the small bladeless wind turbine.

scholarly journals Pull-Out Capability of a 3D Printed Threadless Suture Anchor with Rectangular Cross-Section: A Biomechanical Study

2021 ◽  
Vol 11 (24) ◽  
pp. 12128
Author(s):  
Yueh-Ying Hsieh ◽  
Lien-Chen Wu ◽  
Fon-Yih Tsuang ◽  
Chia-Hsien Chen ◽  
Chang-Jung Chiang
Keyword(s):  
Cross Section ◽  
Cyclic Load ◽  
Suture Anchor ◽  
Rectangular Cross Section ◽  
The Body ◽  
Load Test ◽  
The Novel ◽  
Pullout Strength ◽  
Pull Out ◽  
3D Printed

Suture anchor fixation is a common method for securing bone and soft tissue in the body, with proven applications in the hip, elbow, hand, knee and foot. A critical limiting factor of suture anchors is the pull-out strength, particularly in suboptimal bone. This study introduces a novel 3D printed threadless suture anchor with a rectangular cross-section. The titanium anchor was designed with surface fenestration and a porous central core to improve bone ingrowth. The aim of this study was to compare the pull-out properties of the novel threadless anchor with a traditional circular threaded suture anchor. The anchors were inserted into a 0.24 g/cm3 synthetic cancellous bone block at angles of 90° and 135° to the surface. The sutures were pulled at 180° (parallel) to the surface under a static pull test (anchor pullout) and cyclic load test using a tensile testing machine. Under the static load, the greatest pullout strength was seen with the novel threadless anchor inserted at 90° (mean, 105.6 N; standard deviation [SD], 3.5 N). The weakest pullout strength was seen with the threaded anchor inserted at 90° (mean, 87.9 N; SD, 4.1 N). In the cyclic load test, all six of the threaded anchors with a 90° insertion angle pulled out after 18 cycles (70 N). All of the threadless anchors inserted at 90° survived the cyclic test (90 N). In conclusion, the novel threadless suture anchor with rectangular cross-section and traditional threaded suture anchor had similar pullout survivorship when inserted at either 90° or 135°. In addition, the 3D printed threadless anchor has the potential for good bone integration to improve long-term stabilization.

TEM Study of High Quality GaN Grown by OMVPE Using an Intermediate Layer

2000 ◽  
Vol 622 ◽  
Author(s):  
M. Benamara ◽  
Z. Liliental-Weber ◽  
S. Kellermann ◽  
W. Swider ◽  
J. Washburn ◽  
...  
Keyword(s):  
Cross Section ◽  
Intermediate Layer ◽  
Defect Analysis ◽  
High Quality ◽  
Lateral Epitaxial Overgrowth ◽  
Lateral Overgrowth ◽  
Time Observation ◽  
First Time ◽  
Growth Methods

ABSTRACTWe report on high quality GaN layers grown with the use of one intermediate layer. The defect analysis shows that the density of dislocation is only 8×107/cm2 in these layers, compared to over 1010/cm2 for layers grown without the intermediate layer (IL). Electron microscopy on cross-section samples shows that deposition under certain specific conditions of a low- temperature IL directly benefits the quality of the subsequently deposited GaN layer. The growth of the GaN top layer appears to be similar to growth observed for lateral epitaxial overgrowth layers. This first time observation opens the possibility for using standard growth methods of GaN compounds to achieve a dislocation density comparable to that achieved with lateral overgrowth epitaxy.

An Investigation of Heat Affected Zone of Round Steel Rods Welded by Friction Welding

2012 ◽  
Vol 217-219 ◽  
pp. 2198-2201
Author(s):  
Chawalit Thinvongpituk ◽  
Surasing Arayangkun
Keyword(s):  
High Temperature ◽  
Temperature Gradient ◽  
Heat Affected Zone ◽  
Friction Welding ◽  
Welding Process ◽  
High Strength ◽  
High Quality ◽  
Joint Property ◽  
Welding Technique

Friction welding is a welding technique that has been studied and developed continuously. This is due to its advantages, such as it provides high quality of joint, high strength of joint. It can make welded zone through the whole section without bubble. However, there is heat generated in the welding process that can change the phase of materials. Hence, the hardness and strength of joint are affected. This paper is aimed to investigate the microstructure at the joint, which is called heat affected zone. The experiment was conducted with a number of steel rods of 10 mm. diameter. The welded specimens were tested for strength, hardness and microstructure. The temperature gradient of specimen under welding process was also recorded. It was revealed that the strength of welded element is higher but the hardness is lower. The photo of thermo scan revealed that heat is generated around the lip of interface, resulting high temperature in heat affected zone. This causes some change in microstructure composition as well as joint property.

William Byrd, John Petre and Oxford, Bodleian Ms Mus. Sch. E. 423

1996 ◽  
Vol 29 ◽  
pp. 21-46 ◽  
Author(s):  
David Mateer
Keyword(s):  
Cross Section ◽  
Instrumental Music ◽  
Vocal Music ◽  
High Quality ◽  
Imperfect State ◽  
Sheer Size ◽  
Musical Genres ◽  
William Byrd ◽  
Special Relevance

This manuscript consists of the Contratenor only of what was originally a set of six partbooks. Had the collection survived intact, it would undoubtedly have ranked as one of the most important of all secular sources dating from the Elizabethan period, for it comprises a representative cross-section of most musical genres—English anthems, Latin motets, consort songs and instrumental pieces—and its 131 items include many unica. But the sheer size of the anthology is not the only reason why we should lament its tragically imperfect state. Mus. Sch. E. 423 is an important and authoritative source for the vocal music of William Byrd, as Philip Brett, Alan Brown and other scholars have shown. Writing more generally about the instrumental music it contains, Warwick Edwards has stated that its ‘authority as a consort source derives from its exclusion of all but a few faults against other sources’. The manuscript's special relevance to Byrd, then, not the mention the high quality of its musical and verbal texts, makes the loss of its companion books all the more regrettable.

Preparation and Characterization of SiC Coating on Graphite Substrate

2014 ◽  
Vol 602-603 ◽  
pp. 412-415 ◽  
Author(s):  
Yan Li Huo ◽  
Shu Guang Chen ◽  
Hai Long Liang ◽  
Chun Peng Wang ◽  
Jian Zhou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Cross Section ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Optical Microscope ◽  
Chemical Vapor Infiltration ◽  
Good Combination ◽  
Graphite Substrate

High thermal conductivity and dense SiC coating were fabricated by chemical vapor deposition (CVD) on surface of different graphite at temperature of 1100°C. The results indicated that the thickness of the coating influences the quality of coating. There was no crack in coating when thickness of the coating is less than 0.3mm. The structure of graphite affected the reaction badly. When the graphite is coarse and porous the reaction is chemical vapor infiltration (CVI) and the interface of coating and substrate isnt obvious. When the graphite is dense and smooth, the coating is covered in surface of graphite, the interface is found between the coating and substrate. Optical microscope and SEM were used to observe the surface and cross-section morphology and microstructure of coatings. It shown coating and substrate had a good combination and the deposited grains mainly showed equiaxed form with the crystallite size of 30 nm at 1100°C.

scholarly journals Сверхпроводящий резонатор с микромостиком из гафния при температурах 50-350 mK

2018 ◽  
Vol 44 (13) ◽  
pp. 59
Author(s):  
А.В. Меренков ◽  
С.В. Шитов ◽  
В.И. Чичков ◽  
А.Б. Ермаков ◽  
Т.М. Ким ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Frequency Division Multiplexing ◽  
Frequency Division ◽  
High Quality ◽  
Bias Power ◽  
Superconducting Resonator ◽  
Terahertz Band ◽  
Imaging Array ◽  
Key Factor

AbstractA high-quality superconducting resonator with a microbridge of hafnium film for use in a circuit for readout a terahertz-band imaging array with frequency division multiplexing is demonstrated experimentally. The variability of the impedance of the bridge at a frequency of 1.5 GHz, which is a key factor in the control of the quality of the resonator, is studied. The bridge, having a thickness of about 50 nm, a critical temperature T _ C ≈ 380 mK, and a plan size of 2.5 × 2.5 μm, was connected as a load of a resonator made of niobium film with a thickness of about 100 nm ( T _ C ~ 9 K). It is shown that the bridge smoothly changes its impedance proportionally to the bias power in the entire temperature range. The effective thermal insulation of the bridge was measured in a dilution cryostat at temperatures of 50–300 mK. Thermal conductivity G of the bridge was calculated and found to be ~4 × 10^–13 W/K, which gives an estimate of the sensitivity of the structure in the bolometric mode NEP ≈ 8 × 10^–19 W/Hz^1/2 at a temperature of 150 mK.

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