The induction pumping of Coaxial Lasers on Self-Terminating Transitions

2018 ◽  
pp. 98-112
Author(s):  
V. M. Batenin ◽  
V. T. Karpukhin ◽  
M. M. Malikov ◽  
A. S. Averyushkin ◽  
M. A. Kazaryan ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
High Frequency ◽  
Thermal Characteristics ◽  
Point Of View ◽  
Inductive Method ◽  
Copper Vapour Laser ◽  
Plasma Parameters ◽  
Electrodeless Discharge ◽  
Inverse Population ◽  
First Case

The paper presents the results of the numerical simulations of pumping a copper vapour laser by a repetitively pulsed induction (electrodeless) discharge. We have investigated the version of the laser with an annular discharge volume formed by two coaxial cylinders. Such coaxial chamber is shown to be more appropriate for the induction pumping than the conventional cylindrical chamber. In the first case, higher coupling factors in the transformercoupled circuit of the induction discharge as well as rather high curl electric field are achieved. Moreover, from the ecological point of view, the coaxial chamber appears to be safer for the surrounding personnel in terms of their exposure to electromagnetic radiation. The present work briefly presents the physical model of the laser which describes the dynamics of the plasma parameters, the kinetics of the inverse population of the working levels for the laser on self terminating transitions as well as the development of the induction radiation. The paper also presents the electrical equations describing the simplest source of electrical pump pulses. The thermal characteristics of the working medium are estimated and the design calculations of the chamber are performed. The numerical experiments have found that, in contrast to the case of a conventional copper vapour laser with aperiodic discharge, in the regarded versions of the copper vapour laser the pump pulse is realized as a train of high-frequency damped oscillations. The analysis of the physical processes occurring in the plasma of the high-frequency discharge is carried out. The pulsed behaviour of the Joule heat power is shown to release results in pronounced pulsations of the electron temperature. This fact, however, does not significantly affect the operation of the laser on self-terminating transitions. In the optimal pumping regimes, subtle oscillations are merely observed for the inverse population of the copper atom working levels and for the intensity in the radiation pulse. High output laser characteristics achieved in the numerical simulations demonstrate the potential for efficient pumping of the copper vapour laser using the inductive method which is new for such lasers. 

scholarly journals Insulation Characteristics of Sisal Fibre/Epoxy Composites

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
A. Shalwan ◽  
M. Alajmi ◽  
A. Alajmi
Keyword(s):  
Volume Fraction ◽  
Fibre Volume Fraction ◽  
Thermal Characteristics ◽  
Fibre Volume ◽  
Point Of View ◽  
Natural Fibres ◽  
Epoxy Composites ◽  
Ongoing Research ◽  
Sisal Fibre ◽  
The Impact

Using natural fibres in civil engineering is the aim of many industrial and academics sectors to overcome the impact of synthetic fibres on environments. One of the potential applications of natural fibres composites is to be implemented in insulation components. Thermal behaviour of polymer composites based on natural fibres is recent ongoing research. In this article, thermal characteristics of sisal fibre reinforced epoxy composites are evaluated for treated and untreated fibres considering different volume fractions of 0–30%. The results revealed that the increase in the fibre volume fraction increased the insulation performance of the composites for both treated and untreated fibres. More than 200% insulation rate was achieved at the volume fraction of 20% of treated sisal fibres. Untreated fibres showed about 400% insulation rate; however, it is not recommended to use untreated fibres from mechanical point of view. The results indicated that there is potential of using the developed composites for insulation purposes.

scholarly journals Erratum to: “Influence of external conditions on physical processes and plasma parameters in a model of a high-frequency hybrid plasma system”

2017 ◽  
Vol 46 (4) ◽  
pp. 299-299
Author(s):  
A. F. Aleksandrov ◽  
A. K. Petrov ◽  
K. V. Vavilin ◽  
E. A. Kral’kina ◽  
P. A. Neklyudova ◽  
...  
Keyword(s):  
High Frequency ◽  
Physical Processes ◽  
Plasma Parameters ◽  
Plasma System ◽  
Hybrid Plasma ◽  
External Conditions

scholarly journals Web Application for Statistical Tracking and Predicting the Evolution of Active Cases with the Novel Coronavirus (SARS-CoV-2)

2021 ◽  
pp. 70-74
Author(s):  
Iulia Clitan ◽  
◽  
Adela Puscasiu ◽  
Vlad Muresan ◽  
Mihaela Ligia Unguresan ◽  
...  
Keyword(s):  
Neural Network ◽  
Mathematical Model ◽  
Web Application ◽  
Point Of View ◽  
The Novel ◽  
End User ◽  
First Case ◽  
Novel Coronavirus ◽  
Second Wave ◽  
Over Time

Since February 2020, when the first case of infection with SARS COV-2 virus appeared in Romania, the evolution of COVID-19 pandemic continues to have an ascending allure, reaching in September 2020 a second wave of infections as expected. In order to understand the evolution and spread of this disease over time and space, more and more research is focused on obtaining mathematical models that are able to predict the evolution of active cases based on different scenarios and taking into account the numerous inputs that influence the spread of this infection. This paper presents a web responsive application that allows the end user to analyze the evolution of the pandemic in Romania, graphically, and that incorporates, unlike other COVID-19 statistical applications, a prediction of active cases evolution. The prediction is based on a neural network mathematical model, described from the architectural point of view.

scholarly journals Optimal Design and Testing of a Thermoplastic Pressurized Passenger Door Manufactured Using Thermoforming

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3394
Author(s):  
Roman Růžek ◽  
Josef Křena ◽  
Radek Doubrava ◽  
Josef Tkadlec ◽  
Martin Kadlec ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Impact Damage ◽  
Research Work ◽  
Variable Cross Section ◽  
Mechanical Tests ◽  
Point Of View ◽  
Topological Optimization ◽  
Variable Cross ◽  
Thermoplastic Resin ◽  
Significant Difference

The present paper documents and discusses research work associated with a newly designed passenger door structure demonstrator. The composite structure was manufactured from carbon-fiber-reinforced thermoplastic resin. A composite frame with a variable cross-section was designed, optimized, and fabricated using thermoforming technology. Both numerical simulations and experiments supported structural verification according to the damage tolerance philosophy; i.e., impact damage is presented. The Tsai-Wu and maximal stress criteria were used for damage analysis of the composite parts. Topological optimization of the metal hinges from the point of view of weight reduction was used. All expected parameters and proposed requirements of the mechanical properties were proved and completed. The door panel showed an expected numerically evaluated residual strength (ultimate structure load) as well as meeting airworthiness requirements. No impact damage propagation in the composite parts was observed during mechanical tests, even though visible impact damage was introduced into the structure. No significant difference between the numerical simulations and the experimentally measured total deformation was observed. Repeated deformation measurements during fatigue showed a nonlinear structure behavior. This can be attributed to the relaxation of thermoplastics.

scholarly journals Normalizability analysis of the generalized quantum electrodynamics from the causal point of view

2017 ◽  
Vol 32 (27) ◽  
pp. 1750165 ◽  
Author(s):  
R. Bufalo ◽  
B. M. Pimentel ◽  
D. E. Soto
Keyword(s):  
Perturbation Theory ◽  
Physical Model ◽  
Gauge Invariance ◽  
Quantum Electrodynamics ◽  
Lorentz Invariance ◽  
Point Of View ◽  
Inductive Method ◽  
S Matrix ◽  
Causal Approach

The causal perturbation theory is an axiomatic perturbative theory of the S-matrix. This formalism has as its essence the following axioms: causality, Lorentz invariance and asymptotic conditions. Any other property must be showed via the inductive method order-by-order and, of course, it depends on the particular physical model. In this work we shall study the normalizability of the generalized quantum electrodynamics in the framework of the causal approach. Furthermore, we analyze the implication of the gauge invariance onto the model and obtain the respective Ward–Takahashi–Fradkin identities.

An Alternative Carcass Design to Prevent Flow-Induced Pulsations in Flexibles

2021 ◽  
Author(s):  
N. González Díez ◽  
S. P. C. Belfroid ◽  
T. Iversen Solfeldt ◽  
C. Kristiansen
Keyword(s):  
Pressure Drop ◽  
Theoretical Analysis ◽  
Numerical Simulations ◽  
Steel Strip ◽  
Point Of View ◽  
Theoretical Point ◽  
Adjacent Structures ◽  
Operational Constraints ◽  
Short Time ◽  
Fatigue Failures

Abstract Flow-induced pulsations (FLIP) are pressure oscillations generated inside of flexibles used in dry gas applications that can cause unacceptable vibration levels and eventually failure of equipment. Because of the design of inner layer of the flexibles, the carcass, the frequency of the pulsations is high, potentially leading to fatigue failures of adjacent structures in a relatively short time. The traditional carcass is made of a steel strip formed into an interlocked s-shape in a series of preforming and winding steps. To enable bending of the pipe, gaps are present between each winding with a shape that can cause FLIP. The gaps can be reduced, and the profiles optimized, but they will always be able to generate FLIP at a certain gas velocity. To remove the risk of FLIP in dry gas projects and ensure that operator does not get operational constraints, an alternative carcass design has been developed. This is essentially a conventional agraff carcass but with an additional cover strip to close the gap, making the resulting carcass nearly smooth bore in nature. With a smooth bore this carcass can be used for flexibles which have a risk of FLIP or to produce pipes with a lower internal roughness. This alternative design can be manufactured and can therefore build on the large manufacturing and design experience of the traditional strip carcass. This alternative carcass technology is to undergo a full qualification process, in which the risk of flow induced pulsations is an essential component. With the investigated alternative carcass design, the cavities present in the traditional agraff designs are covered. It is expected that the risk due to the appearance of FLIP is therefore eliminated. Theoretical analysis, numerical simulations and scaled experiments are used to explore the risk for the alternative technology to create FLIP. The theoretical analysis is based on existing knowledge and literature. The numerical simulations and scaled tests are done to generate direct evidence for the end statements resulting from the qualification process. Numerical simulations follow the power balance method presented by the same authors in earlier papers. The same applies to the techniques used for the scaled tests. The main outcome of the qualification presented here are the pressure drop performance and the anti-FLIP capabilities of the design. The new design performs significantly better than the nominal design carcass for the same purpose. The pressure drop coefficients found are close to those expected for a normal, non-corrugated pipe, and thus the recommendation given by the API 17J standard does not apply to this design. The pressure drop coefficient is dependent on the installation direction of the flexible with respect to the flow. No signs of FLIP are found for the nominal design of the investigated carcass technology. This is the case for either installation direction. This is explained from a theoretical point of view, but also numerical and experimental evidence are provided.

A diagnostic pitfall in hepatic mesenchymal hamartoma mimicking hepatoblastoma: A case report

2020 ◽  
Author(s):  
Zhihong Chen ◽  
Lutong Fang ◽  
Ying Zhang ◽  
Yuanzi Ye ◽  
Wenshu Ji ◽  
...  
Keyword(s):  
Blood Vessels ◽  
Female Child ◽  
Point Of View ◽  
Mesenchymal Hamartoma ◽  
Diagnostic Pitfall ◽  
First Case ◽  
Contrast Enhanced ◽  
Enhanced Ct ◽  
Vascular Channels ◽  
The Right

Abstract Background: Hepatic mesenchymal hamartoma (HMH) is an uncommon benign tumor in children. While mesenchymal hamartomas may be angiomatous and blood vessels may be identified, HMH with a malignant tumor symptom on the contrast-enhanced hepatic computed tomography angiography (CTA) has not been described. Here, we present the first case of HMH mimicking hepatoblastoma on the hepatic CTA from pathological point of view and review the imaging and histological features of this unique lesion. Case presentation: A 2-year-old female child was found a distention in the right abdomen and was admitted to our hospital. The Hepatic CTA showed that the blood vessels were thickened, the tumor blood vessels were clustered in the tumor. According to the hepatic CT findings, the tumor was considered to be malignant, possibly a hepatoblastoma. Microscopic examination showed a tumor arranged in lobules, composed of loose myxoid mesenchyme surrounding ductal structures, with intervening vascular channels. The Immunohistochemical staining revealed positive CK7 and CD34 for the bile duct elements and the lining endothelial cells of the vascular channels. There were abundant blood vessels around the nodules and the margins of remaining hepatocytes, but few in the central region. The blood vessels are small, thin-walled vessels and presented like capillaries and venules. Conclusions: A histological diagnosis of Hepatic Mesenchymal Hamartoma was confirmed by the microscopic examinations. This case adds learning points to radiologists when heterogeneous reinforcement on enhanced CT scan was presented in such a large childhood liver tumor.

scholarly journals Complete laparoscopic pancreaticoduodenectomy: our experience of the first case

2019 ◽  
Vol 22 (1) ◽  
pp. 26-30
Author(s):  
Mukund Raj Joshi ◽  
Sujan Regmee ◽  
Tanka Prasad Bohara ◽  
Rupesh Chakradhar ◽  
Mandesh Shrestha
Keyword(s):  
Blood Loss ◽  
Point Of View ◽  
Resected Specimen ◽  
Laparoscopic Pancreaticoduodenectomy ◽  
Technical Aspects ◽  
Technical Point ◽  
Operative Outcomes ◽  
Post Operative Period ◽  
First Case

Laparoscopic pancreaticoduodenectomy was described in 1994. It is considered the most challenging abdominal surgery. Although the procedure was found to be feasible in initial reports, the benefits were not considered favorable. In recent days, with the increasing experience of surgeons, acceptable outcomes are being observed and have been found to be technically beneficial and oncologically safe in selective cases in experienced hands. We performed the procedure in a 42-year-old gentleman with good operative and post-operative outcomes. The patient’s follow-up for six post-operative months seems satisfactory. The operation took 840 minutes with minimal blood loss. The resected specimen was adequate and satisfactory from an oncological and technical point of view. The patient developed some inherent complications of the procedure in the post-operative period. He recovered well. Details of the case and technical aspects are being discussed.  

scholarly journals Determining breast pathology in surgical margins with high-frequency ultrasound: phantom and numerical simulations

2013 ◽  
Author(s):  
Timothy E. Doyle ◽  
Monica Cervantes ◽  
Laurel A. Thompson ◽  
Joseph E. Roring ◽  
Matthew A. Grover ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
High Frequency ◽  
Surgical Margins ◽  
High Frequency Ultrasound ◽  
Breast Pathology ◽  
Ultrasound Phantom ◽  
Frequency Ultrasound
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