Theoretical and Experimental Crushing Analysis of Metal Square Honeycombs Under Quasi-Static Loading

2010 ◽  
Author(s):  
M. Zarei Mahmoudabadi ◽  
M. Sadighi ◽  
A. Eyvazian
Keyword(s):  
Flow Stress ◽  
Static Loading ◽  
Experimental Tests ◽  
High Energy ◽  
Geometrical Parameters ◽  
External Work ◽  
Modified Model ◽  
Curvature Effects ◽  
The Mean ◽  
Honeycomb Material

Honeycomb cellular structures, due to their light weight and high energy absorbing, have been used extensively as energy absorbers or cushions to resist external loads. In this paper, the mean crushing stress and the wavelength of the folding mode, as two important parameters in the study of metal square honeycomb crushing under quasi-static loading have been investigated theoretically and experimentally. Firstly, by considering the true cylindrical curvature effects and the flow stress in the folding mode of the honeycomb material, the Wierzbicki’s model in the study of metal hexagonal honeycomb crushing under quasi-static loading is modified. This modification is performed by rewriting the internal energy terms and the external work in the energy method through the basic element folding by considering the true cylindrical curvature effects and the flow stress of the honeycomb material. Comparison of the results obtained by this modified model and Wierzbicki’s model with the experimental data shows better prediction by the model presented in this paper. Subsequently, this modified model has been extended to the study of metal square honeycombs crushing under quasi-static loading and the mean crushing stress and the wavelength of the folding mode of these structures have been predicted. This analytical model predicts the mean crushing stress of the metal square honeycomb as a function of both the geometrical parameters and its material, while the predicted wavelength of the folding mode is just a function of the geometrical parameters. Finally, the experimental tests have been performed to verify the preciseness of this theoretical model.

Anisotropy of damage productions in electron irradiated molybdenum

1978 ◽  
Vol 36 (1) ◽  
pp. 354-355
Author(s):  
K. Izui ◽  
S. Furuno ◽  
H. Otsu ◽  
T. Nishida ◽  
H. Maeta
Keyword(s):  
Electron Flux ◽  
Threshold Energy ◽  
High Energy ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
Displacement Threshold ◽  
The Mean ◽  
Channeling Effect ◽  
Different Origins ◽  
Threshold Energies

Anisotropy of damage productions in crystals due to high energy electron bombardment are caused from two different origins. One is an anisotropic displacement threshold energy, and the other is an anisotropic distribution of electron flux near the atomic rows in crystals due to the electron channeling effect. By the n-beam dynamical calculations for germanium and molybdenum we have shown that electron flux at the atomic positions are from ∽4 to ∽7 times larger than the mean incident flux for the principal zone axis directions of incident 1 MeV electron beams, and concluded that such a locally increased electron flux results in an enhanced damage production. The present paper reports the experimental evidence for the enhanced damage production due to the locally increased electron flux and also the results of measurements of the displacement threshold energies for the <100>,<110> and <111> directions in molybdenum crystals by using a high voltage electron microscope.

General Relativity

2019 ◽  
Author(s):  
Steven Carlip
Keyword(s):  
General Relativity ◽  
High Energy Physics ◽  
Hamiltonian Formulation ◽  
Experimental Tests ◽  
High Energy ◽  
Gravitational Energy ◽  
Field Equations ◽  
Physics First ◽  
Condensed Matter Theory ◽  
Introductory Textbooks

This work is a short textbook on general relativity and gravitation, aimed at readers with a broad range of interests in physics, from cosmology to gravitational radiation to high energy physics to condensed matter theory. It is an introductory text, but it has also been written as a jumping-off point for readers who plan to study more specialized topics. As a textbook, it is designed to be usable in a one-quarter course (about 25 hours of instruction), and should be suitable for both graduate students and advanced undergraduates. The pedagogical approach is “physics first”: readers move very quickly to the calculation of observational predictions, and only return to the mathematical foundations after the physics is established. The book is mathematically correct—even nonspecialists need to know some differential geometry to be able to read papers—but informal. In addition to the “standard” topics covered by most introductory textbooks, it contains short introductions to more advanced topics: for instance, why field equations are second order, how to treat gravitational energy, what is required for a Hamiltonian formulation of general relativity. A concluding chapter discusses directions for further study, from mathematical relativity to experimental tests to quantum gravity.

Optimal hydraulic design of an ultra-low specific speed centrifugal pump based on the local entropy production theory

2019 ◽  
Vol 233 (6) ◽  
pp. 715-726 ◽  
Author(s):  
Hucan Hou ◽  
Yongxue Zhang ◽  
Xin Zhou ◽  
Zhitao Zuo ◽  
Haisheng Chen
Keyword(s):  
Entropy Production ◽  
Centrifugal Pump ◽  
Orthogonal Design ◽  
High Energy ◽  
Geometrical Parameters ◽  
Production Theory ◽  
Local Entropy ◽  
Hydraulic Design ◽  
Low Specific Speed ◽  
Specific Speed

The ultra-low specific speed centrifugal pump has been widely applied in aerospace engineering, metallurgy, and other industrial fields. However, its hydraulic design lacks specialized theory and method. Moreover, the impeller and volute are designed separately without considering their coupling effect. Therefore, the optimal design is proposed in this study based on the local entropy production theory. Four geometrical parameters are selected to establish orthogonal design schemes including blade outlet setting angle, wrapping angle volute inlet width, and throat area. Subsequently, a 3D steady flow with Reynolds stress turbulent model and energy equation model is numerically conducted and the entropy production is calculated by a user-defined function code. The range analysis is made to identify the optimal scheme indicating that the combination of local entropy production and orthogonal design is feasible on pump optimization. The optimal pump is visibly improved with an increase of 1.08% in efficiency. Entropy production is decreased by 16.75% and 6.03% in impeller and volute, respectively. High energy loss areas are captured and explained in terms of helical vortex and wall friction, and the turbulent and wall entropy production are respectively reduced by 3.82% and 14.34% for the total pump.

scholarly journals Performance Characteristics in Runner of an Impulse Water Turbine with Splitter Blade

Processes ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 303
Author(s):  
Lingdi Tang ◽  
Shouqi Yuan ◽  
Yue Tang ◽  
Zhijun Gao
Keyword(s):  
Energy Conversion ◽  
Flow Direction ◽  
Mechanical Energy ◽  
Experimental Tests ◽  
High Energy ◽  
Negative Energy ◽  
Water Turbine ◽  
Conversion Performance ◽  
Water Turbines ◽  
Current Energy

The impulse water turbine is a promising energy conversion device that can be used as mechanical power or a micro hydro generator, and its application can effectively ease the current energy crisis. This paper aims to clarify the mechanism of liquid acting on runner blades, the hydraulic performance, and energy conversion characteristics in the runner domain of an impulse water turbine with a splitter blade by using experimental tests and numerical simulations. The runner was divided into seven areas along the flow direction, and the power variation in the runner domain was analyzed to reflect its energy conversion characteristics. The obtained results indicate that the critical area of the runner for doing the work is in the front half of the blades, while the rear area of the blades does relatively little work and even consumes the mechanical energy of the runner to produce negative work. The high energy area is concentrated in the flow passage facing the nozzle. The energy is gradually evenly distributed from the runner inlet to the runner outlet, and the negative energy caused by flow separation with high probability is gradually reduced. The clarification of the energy conversion performance is of great significance to improve the design of impulse water turbines.

scholarly journals The Surgical Outcomes of Unstable Ankle Fractures in Patients Aged >65 Years

2021 ◽  
Vol 12 ◽  
pp. 215145932199776
Author(s):  
Adem Sahin ◽  
Anıl Agar ◽  
Deniz Gulabi ◽  
Cemil Erturk
Keyword(s):  
Surgical Outcomes ◽  
External Rotation ◽  
High Energy ◽  
Ankle Fractures ◽  
Medial Malleolus ◽  
Aofas Score ◽  
Non Union ◽  
The Mean ◽  
Medial Malleolus Fracture ◽  
Mechanism Of Trauma

Aim: To evaluate the surgical outcomes and complications of patients over 65 years of age, with unstable ankle fractures. Material and Method: The study included 111 patients (73F/38 M) operated on between January 2015 and February 2019 and followed up for a mean of 21.2 months (range, 6-62 months).Demographic characteristics, comorbidities, fracture type, and mechanisms of injury were evaluated. Relationships between postoperative complications and comorbidities were examined. In the postoperative functional evaluations, the AOFAS score was used and pre and postoperative mobilization (eg, use of assistive devices) was assessed. Results: The mean age of the patients was 70.5 ± 6.1 years (range, 65-90 years). The mechanism of trauma was low-energy trauma in 90.1% of the fractures and high-energy trauma in 9.9%. The fractures were formed with a SER injury (supination external rotation) in 83.7% of cases and bimalleolar fractures were seen most frequently (85/111, 76%).Complications developed in 16 (14.4%) patients and a second operation was performed in 11 (9.9%) patients with complications. Plate was removed and debridement was performed in 5 of 6 patients due to wound problems. Nonunion was developed in the medial malleolus in 4 patients. Revision surgery was performed because of implant irritation in 2 patients and early fixation loss in the medial malleolus fracture in one patient. Calcaneotibial arthrodesis was performed in 3 patients because of implant failure and ankle luxation associated with non-union. A correlation was determined between ASA score and DM and complications, but not with osteoporosis. The mean follow-up AOFAS score was 86.7 ± 12.5 (range, 36-100).A total of 94 (84.7%) patients could walk without assistance postoperatively and 92 (82.9%) were able to regain the preoperative level of mobilization. Conclusion: Although surgery can be considered an appropriate treatment option for ankle fractures in patients aged >65 years, care must be taken to prevent potential complications and the necessary precautions must be taken against correctable comorbidities.

scholarly journals Importance of a Follow-Up Ultrasound Protocol in Monitoring Posttraumatic Spleen Complications in Children Treated with a Non-Operative Management

Medicina ◽  
2021 ◽  
Vol 57 (8) ◽  
pp. 734
Author(s):  
Ivona Djordjevic ◽  
Dragoljub Zivanovic ◽  
Ivana Budic ◽  
Ana Kostic ◽  
Danijela Djeric
Keyword(s):  
Splenic Abscess ◽  
Operative Management ◽  
High Energy ◽  
Significant Difference ◽  
Injury Grade ◽  
Grade Ii ◽  
The Mean ◽  
Non Operative Management ◽  
Grade Iii

Background and objectives: For the last three decades, non-operative management (NOM) has been the standard in the treatment of clinically stable patients with blunt spleen injury, with a success rate of up to 95%. However, there are no prospective issues in the literature dealing with the incidence and type of splenic complications after NOM. Materials and methods: This study analyzed 76 pediatric patients, up to the age of 18, with blunt splenic injury who were treated non-operatively. All patients were included in a posttraumatic follow-up protocol with ultrasound examinations 4 and 12 weeks after injury. Results: The mean age of the children was 9.58 ± 3.97 years (range 1.98 to 17.75 years), with no statistically significant difference between the genders. The severity of the injury was determined according to the American Association for Surgery of Trauma (AAST) classification: 7 patients had grade I injuries (89.21%), 21 patients had grade II injuries (27.63%), 33 patients had grade III injuries (43.42%), and 15 patients had grade IV injuries (19.73%). The majority of the injuries were so-called high-energy ones, which were recorded in 45 patients (59.21%). According to a previously created posttraumatic follow-up protocol, complications were detected in 16 patients (21.05%). Hematomas had the highest incidence and were detected in 11 patients (14.47%), while pseudocysts were detected in 3 (3.94%), and a splenic abscess and pseudoaneurysm were detected in 1 patient (1.31%), respectively. The complications were in a direct correlation with injury grade: seven occurred in patients with grade IV injuries (9.21%), five occurred in children with grade III injuries (6.57%), three occurred in patients with grade II injuries (3.94%), and one occurred in a patient with a grade I injury (1.31%). Conclusion: Based on the severity of the spleen injury, it is difficult to predict the further course of developing complications, but complications are more common in high-grade injuries. The implementation of a follow-up ultrasound protocol is mandatory in all patients with NOM of spleen injuries for the early detection of potentially dangerous and fatal complications.

scholarly journals Application of Radiation-Thermal Treatment to Suppress Sensitivity of Silicon Microcircuits to Single Radiation Effects

2021 ◽  
Vol 8 (3) ◽  
pp. 99-103
Author(s):  
P. B. Lagov ◽  
◽  
A. S. Drenin ◽  
A. A. Meshcheryakov ◽  
N. A. Yudanov ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Integrated Circuits ◽  
Radiation Effects ◽  
Experimental Tests ◽  
High Energy ◽  
Particle Accelerators ◽  
Transfer Coefficients ◽  
Heavy Charged Particles ◽  
Equilibrium Charge ◽  
Technological Tool

The paper analyses the possibility to reduce the sensitivity of silicon integrated circuits (ICs) to single radiation effects by means of radiation-thermal treatment including irradiation in charged particle accelerators and subsequent low-temperature heat treatment. It is shown that reduction in sensitivity to single radiation effects is provided by formation of thermostable recombination centers in semiconductor IC structure in necessary concentrations. At the same time a decrease in primary photocurrent generated by heavy charged particles or high-energy protons, reduction in transfer coefficients of parasitic bipolar transistors forming thyristor structures, reduction in carrier avalanche multiplication coefficients at high electric field strengths can be provided. Radiationthermal treatment can be introduced in the manufacturing process of ICs of various classes at the end of the manufacturing cycle and does not require correction of the basic technology. A possible undesirable growth of inverse currents and preservation of values of other electrical parameters within acceptable values when using radiation-thermal treatment is provided by choosing optimal modes of irradiation and annealing which are established in the course of experimental tests. The calculated evaluation has shown that using radiation-thermal treatment in the technology of IC fabrication can provide a decrease in the effective collection length of non-equilibrium charge carriers generated under the influence of single radiation effects by at least 10 times which allows considering radiation-thermal treatment as an effective technological tool to suppress the sensitivity to single radiation effects.

scholarly journals Regulation of murine myocardial energy metabolism during adrenergic stress studied by in vivo 31P NMR spectroscopy

2003 ◽  
Vol 285 (5) ◽  
pp. H1976-H1979 ◽  
Author(s):  
A. V. Naumova ◽  
R. G. Weiss ◽  
V. P. Chacko
Keyword(s):  
Heart Rate ◽  
Cardiac Metabolism ◽  
High Energy ◽  
Dobutamine Stress ◽  
Resonance Spectroscopy ◽  
31P Nmr Spectroscopy ◽  
Adult Mice ◽  
The Mean ◽  
Large Animals

Image-guided, spatially localized 31P magnetic resonance spectroscopy (MRS) was used to study in vivo murine cardiac metabolism under resting and dobutamine-induced stress conditions. Intravenous dobutamine infusion (24 μg · min–1 · kg body wt–1) increased the mean heart rate by ∼39% from 482 ± 46 per min at baseline to 669 ± 77 per min in adult mice. The myocardial phosphocreatine (PCr)-to-ATP (PCr/ATP) ratio remained unchanged at 2.1 ± 0.5 during dobutamine stress, compared with baseline conditions. Therefore, we conclude that a significant increase in heart rate does not result in a decline in the in vivo murine cardiac PCr/ATP ratio. These observations in very small mammals, viz., mice, at extremely high heart rates are consistent with studies in large animals demonstrating that global levels of high-energy phosphate metabolites do not regulate in vivo myocardial metabolism during physiologically relevant increases in cardiac work.

Based on Comparable Price Energy Input-Output Table of Xinjiang to Research Low Carbon Economic Development Strategy

2013 ◽  
Vol 291-294 ◽  
pp. 1573-1576
Author(s):  
Yuan Sheng Huang ◽  
Lu Tong Li
Keyword(s):  
Development Strategy ◽  
Carbon Emissions ◽  
Energy Input ◽  
High Energy ◽  
Low Carbon ◽  
Input Output ◽  
Output Table ◽  
The Mean ◽  
The Cost ◽  
Advanced Production

Based on the input-output theory, the paper using the comparable price energy input-output table,quantitatively estimates the implicit carbon emissions of each industrial department,and analyzes the growth of the implicit carbon emissions of the resident consumption through the structure decomposition.Conclusion indicates:From 1992 to 1997, the mean of the implicit carbon emissions of each industrial department in Xinjiang had been rising; From 1997 to 2007, the mean of the implicit carbon emissions of each industrial department had been declining;The implicit carbon emissions of Hydropower industry, the fire power and other seven similar industrial department were higher than that of each industrial department so that Xinjiang should strengthen monitoring on the high energy consumption.The implicit carbon emissions of the resident consumption was still in the trend of ceaseless growth and all of that states clearly that the economic grows at the cost of the increase of the greenhouse gas emissions.Xinjiang should introduce foreign advanced production technology,further optimizing the structure of the resident consumption.

scholarly journals Rotating Stall in Centrifugal Compressor Vaneless Diffuser: Experimental Analysis of Geometrical Parameters Influence on Phenomenon Evolution

2004 ◽  
Vol 10 (6) ◽  
pp. 433-442 ◽  
Author(s):  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Leonardo Baldassarre
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Experimental Tests ◽  
Fast Response ◽  
Rotating Stall ◽  
Geometrical Parameters ◽  
Vaneless Diffuser ◽  
Response Dynamic ◽  
Frequency Domains

The rotating stall is a key problem for achieving a good working range of a centrifugal compressor and a detailed understanding of the phenomenon is very important to anticipate and avoid it. Many experimental tests have been planned by the authors to investigate the influence on stall behavior of different geometrical configurations. A stage with a backward channel upstream, a 2-D impeller with a vaneless diffuser and a constant cross-section volute downstream, constitute the basic configuration. Several diffuser types with different widths, pinch shapes, and diffusion ratios were tested. The stage was instrumented with many fast response dynamic pressure sensors so as to characterize inception and evolution of the rotating stall. This kind of analysis was carried out both in time and in frequency domains. The methodology used and the results on phenomenon evolution will be presented and discussed in this article.

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