OPTIMIZATION OF COMPLEXLY SHAPED DISSIPATIVE SILENCERS

Akustika ◽  
2021 ◽  
pp. 94
Author(s):  
Andrey Taratorin ◽  
Ainur Mukhametov
Keyword(s):  
Complex Shape ◽  
Aerodynamic Drag ◽  
Aerodynamic Resistance ◽  
Acoustic Properties ◽  
Constant Thickness ◽  
Thickness Change ◽  
Complex Shapes ◽  
The Mean ◽  
Verification Of Models ◽  
Comprehensive Study

The article is about a comprehensive study of dissipative silencers of complex shapes. Analyzed the acoustic efficiency of such silencers. The sound absorption coefficient determined from experimental data. The acoustic properties of plate silencers take into account that coefficient. Presented the results of verification of models with plates of constant thickness. Considered the plates of complex shapes: uniform thickness change, convex and concave. Obtained results of modeling the acoustic efficiency of silencers with complex shape plates. These results are for different values of the mean integral thickness for the octave bands frequencies. Determined the dependence of the length of complex shapes silencers on their mean integral thickness. Presented the results of mathematical modeling of the airflow in silencers to determine their aerodynamic drag. The calculations showed that there is an optimal shape and mean integral thickness of the plates. Under which conditions the aerodynamic resistance of the silencer is minimal.

scholarly journals Gender-wise Comparative Assessment of Lifestyle Patterns and Well-being Status among Healthcare Employees at a Tertiary Care Hospital

2021 ◽  
Author(s):  
Vanajakshamma Velam ◽  
Vyshnavi Kancherla ◽  
Latheef Kasala ◽  
Anusha Kancherla ◽  
Mounica Reddy Pillaram
Keyword(s):  
Tertiary Care Hospital ◽  
Tertiary Care ◽  
Well Being ◽  
Care Hospital ◽  
Cross Sectional ◽  
Significant Difference ◽  
Female Employees ◽  
The Mean ◽  
Lifestyle Patterns ◽  
Comprehensive Study

Abstract Background This study was an attempt to assess and compare the gender-wise lifestyle patterns and well-being status among the employees of a tertiary care teaching hospital. Material and Methods This is a cross-sectional, questionnaire-based study conducted at a tertiary care hospital between May and August 2019. A total of 777 employees belonging to both genders (male and female) and working at different professional levels were assessed. All the enrolled employees were subjected to a comprehensive study tool consisting of various dimensions of their health, which included physical, mental, social, spiritual and intellectual health dimensions. Results Among the participants, 327 (42.1%) were male and 450 (57.9%) were female. There was no significant difference in the mean age of male (37.91 ± 7.52) and female (36.85 ± 8.16) employees (p = 0.07). A significantly higher proportion of diabetes and hypertension were seen in male employees (9.8% and 14.4%, respectively) than in female (5.6% and 6.2% respectively). The overall well-being was better in male employees than in females and was statistically significant (p < 0.0001). We found that male employees had statistically significant better well-being in terms of physical, mental and social health whereas female employees had intellectual health. Conclusion The overall well-being in healthcare staff was good at our tertiary care hospital, and the outstanding/good well-being rate was higher in male employees than in female employees. Female employees experienced risks with regard to their physical health.

Contact of Rough Surfaces in Ankle Implants Under Combined Normal and Twist Loading

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Mohammad Hodaei ◽  
Kambiz Farhang
Keyword(s):  
Medical Application ◽  
Roughness Effects ◽  
Implant Surface ◽  
Surface Separation ◽  
Lateral Contact ◽  
Medical Issues ◽  
The Mean ◽  
Scale Roughness ◽  
Approximate Equations ◽  
Comprehensive Study

The medical application of implant replacements to remedy the pain in joints has necessitated a comprehensive study of wear due to contact of implant surfaces. Excessive wear can lead to toxicity and other implant associated medical issues such as patient discomfort and decreased mobility. Since implant wear is the result of contact between surfaces of tibia and talus implant, it is important to establish a model that can address implant surface contact mechanics with roughness effects. In this research, a statistical contact model is developed for the interaction of tibia and talus including normal and lateral contact in which surface roughness effects are included. The model accounts for the elastic–plastic interaction of the implant surface with roughness. For this purpose, tibia and talus implants are considered as macroscopic surfaces containing micron-scale roughness. Approximate equations are obtained that relate the contact force to the mean surface separation explicitly. Closed-form equations are obtained for hysteretic energy loss in implant using the approximate equations. Such a function can serve as a very useful tool for implant designers and manufacturers. Natural frequencies of both adduction-abduction and planter-dorsiflexion rotations are obtained using nonlinear vibration analyses.

The aerodynamic resistance to a rotating sphere in the transition régime between free molecule and continuum creep flow

1964 ◽  
Vol 279 (1376) ◽  
pp. 39-49 ◽  
Keyword(s):  
Rarefied Gas ◽  
Aerodynamic Drag ◽  
Aerodynamic Resistance ◽  
Reynolds Numbers ◽  
Approximate Theory ◽  
Drag Torque ◽  
Free Molecule ◽  
Steel Sphere ◽  
Creep Flow ◽  
Wide Range

An experimental and theoretical study has been made of the aerodynamic drag torque on a sphere rotating in a rarefied gas. The drag torque on a magnetically suspended polished steel sphere rotating in air was measured over a wide range of Knudsen numbers from continuum to free molecule flow and for several different Mach numbers up to ca . 1. The drag under free molecule conditions was found to be consistent with the assumption of perfectly diffuse reflexion of molecules at the surface of the rotor. An approximate theory is derived which is analogous to Millikan’s solution to the problem of plane Couette flow and is valid for low Mach and Reynolds numbers. Theory and experiment are found to agree to within 10 % in the range investigated, for Reynolds numbers less than ca . 20.

Estimating Curvature of Nondifferentiable Functions and Complex Shape Contours

2005 ◽  
Vol 101 (2) ◽  
pp. 362-364 ◽  
Author(s):  
Noah Schwartz
Keyword(s):  
Visual Experience ◽  
Complex Shape ◽  
Simple Modification ◽  
Nondifferentiable Functions ◽  
Point Of Interest ◽  
Complex Shapes ◽  
Psychophysical Analysis ◽  
Sharp Corners

Salvadori and Luccio demonstrated that, for the purpose of psychophysical analysis, the curvature of a point on a continuous single-valued function can be quantified as the inverse ray of the circle osculating the function at the point of interest. While this method is mathematically sound, it does not allow for estimation of curvature in complex shapes containing discontinuities and irregularities such as sharp corners, closed contours, or line intersections—features that commonly occur in normal visual experience. In this paper, a simple modification of this algorithm is presented which overcomes these limitations by using discrete rather than continuous contour sampling, thereby allowing estimation of curvature for a wider variety of shape contours.

scholarly journals Effect of reinforcements on polymer matrix bio-composites – an overview

2018 ◽  
Vol 25 (6) ◽  
pp. 1039-1058 ◽  
Author(s):  
Sumit Das Lala ◽  
Ashish B. Deoghare ◽  
Sushovan Chatterjee
Keyword(s):  
Mechanical Properties ◽  
Low Cost ◽  
Natural Fibers ◽  
High Strength ◽  
Low Density ◽  
Intrinsic Properties ◽  
Environment Friendly ◽  
Complex Shapes ◽  
Strength And Durability ◽  
Comprehensive Study

AbstractThe inherent properties of bio-composites such as biodegradability, environment friendly, low cost of production, high strength and durability make them a suitable replacement to traditional materials such as glass and nylon. Bio-polymers are finding wide applications due to their intrinsic properties such as low density, low thermal conductivity, corrosion resistance and ease of manufacturing complex shapes. This paper aims toward a comprehensive study on polymer bio-composites. The review mainly focuses on types of reinforcements such as natural fibers, seed shells, animal fibers, cellulose, bio-polymers, bio-chemicals and bioceramics which enhance the mechanical properties, such as tensile strength, compressive strength, flexural strength, Young’s modulus and creep behavior, of the composites. The pertinent study carried out in this review explores an enormous potentiality of the composites toward a wide variety of applications.

Design of layered structure for thermal cloak with complex shape

2016 ◽  
Vol 30 (20) ◽  
pp. 1650256 ◽  
Author(s):  
Xuebo Yuan ◽  
Guochang Lin ◽  
Youshan Wang
Keyword(s):  
Numerical Simulations ◽  
Layered Structure ◽  
Complex Shape ◽  
Thermal Protection ◽  
Design Method ◽  
Two Dimensional ◽  
Spatial Transformation ◽  
Complex Shapes ◽  
Potential Applications ◽  
Thermal Cloaking

Thermal cloaks have potential applications in thermal protection and sensing, and those cloaks with complex shapes are much more efficient in application. Layered discretization is a valid way to realize thermal cloaks designed through spatial transformation which are usually nonhomogeneous and anisotropic. However, previous studies are limited to two-dimensional cylindrical ones. Based on the theories of spatial transformation and effective medium, a four-step design method for layered structure of thermal cloak with complex shape is proposed. It is expected to realize the designed layered structure by utilizing the existing regular materials. According to the numerical simulations, the thermal cloaking performances of layered structures are good and close to that of the perfect thermal cloaks. This study has provided an effective way for realizing thermal cloak with complex shape.

scholarly journals Quiescent-phase evolution of a surge-type glacier: Black Rapids Glacier, Alaska, U.S.A.

1996 ◽  
Vol 42 (140) ◽  
pp. 110-122 ◽  
Author(s):  
T.A. Heinrichs ◽  
L.R. Mayo ◽  
K.A. Echelmeyer ◽  
W.D. Harrison
Keyword(s):  
Phase Evolution ◽  
Ice Thickness ◽  
Alaska Range ◽  
Thickness Change ◽  
Quiescent Phase ◽  
Cyclical Fluctuations ◽  
Ice Velocity ◽  
The Mean ◽  
Black Rapids Glacier ◽  
Speed Fluctuations

AbstractBlack Rapids Glacier, a surge-type glacier in the Alaska Range, most recently surged in 1936–37 and is currently in its quiescent phase. Mass balance, ice velocity and thickness change have been measured at three to ten sites from 1972 to 1994. The annual speed has undergone cyclical fluctuations of as much as 45% about the mean speed. Ice thickness and surface slope did not change enough to cause the speed fluctuations through changes in ice deformation, which indicates that they are being drinven by changes in basal motion. The behavior of Black Rapids Glacier during this quiescent phase is significantly different from that of Variegated Glacier, another well-studied surge-type glacier in Alaska. The present medial-moraine configuration of Black Rapids Glacier indicates that a surge could occur at any time. However, ice velocity data indicate that the next surge may not be imminent. We belive that there is little chance that the next surge will cross and dam the Delta River.

A comprehensive study of mechanical and acoustic properties of selective laser melting material

2019 ◽  
Vol 20 (1) ◽  
Author(s):  
Claudia Barile ◽  
Caterina Casavola ◽  
Vincenzo Moramarco ◽  
Paramsamy Kannan Vimalathithan
Keyword(s):  
Selective Laser Melting ◽  
Acoustic Properties ◽  
Laser Melting ◽  
Melting Material ◽  
Comprehensive Study

Experimental investigation of the aerodynamic drag of roof-mounted insulators for trains

2019 ◽  
Vol 234 (8) ◽  
pp. 834-846
Author(s):  
Jonathan Tschepe ◽  
Jörg-Torsten Maaß ◽  
Christian Navid Nayeri ◽  
Christian Oliver Paschereit
Keyword(s):  
Boundary Conditions ◽  
Energy Demand ◽  
High Speed ◽  
Aerodynamic Drag ◽  
Aerodynamic Resistance ◽  
Reynolds Numbers ◽  
Experimental Investigations ◽  
Flexible Material ◽  
High Speed Trains ◽  
The Impact

This paper presents the results of experimental investigations on the aerodynamic drag of roof-mounted insulators for use on low- and high-speed trains. Wind tunnel investigations at different Reynolds numbers in the subcritical, critical, and supercritical flow regime were performed, in addition to investigations using wall-mounted cylinders. Furthermore, the impact of insulator sheds made of flexible material was analyzed. For a better understanding of the aerodynamic behavior of the insulators when mounted on trains, different boundary conditions representing realistic configurations as found on the roof of trains were simulated. From the measured drag, the energy demand to overcome the aerodynamic resistance of different types of insulators was calculated. Depending on the above mentioned boundary conditions, a noticeable contribution of the insulators to the entire train's aerodynamic drag could be observed. With flexible insulator sheds, a further increased air resistance was observed with the onset of fluttering. Similar to the cylinder, the aerodynamic behavior of the insulators depends on the respective Reynolds number.

scholarly journals Subchondral Bone Degradation Following Bone Marrow Stimulation -An MRI Analysis-

2017 ◽  
Vol 2 (3) ◽  
pp. 2473011417S0000
Author(s):  
Yoshiharu Shimozono ◽  
Youichi Yasui ◽  
Robin Megill ◽  
John Kennedy
Keyword(s):  
Subchondral Bone ◽  
Scoring System ◽  
3 Tesla ◽  
Joint Loading ◽  
Thickness Change ◽  
Health Score ◽  
Subchondral Cyst ◽  
3 Tesla Mri ◽  
The Mean

Category: Ankle Introduction/Purpose: Microfracture is the most common operative procedure for the treatment of osteochondral lesions of the talus (OLT). The role of the subchondral bone (SCB)/plate (SCBP) is recognized as one of the most significant factors providing joint-loading support to the ankle. Greater attention has recently been paid to the SCBP and its effects on overlying hyaline and fibrocartilage function. However, damage to the SCB and SCBP during microfracture may irreversibly change the joint loading support of the ankle, leading to reparative cartilage degradation. The purpose of this study is to investigate the morphological change in the SCB and SCBP after microfracture for OLT by developing a novel magnetic resonance imaging (MRI) scoring system specifically for evaluating SCB and SCBP. Methods: Twenty patients who underwent microfracture for OLT and had at least a one year follow-up 3-Tesla MRI between 2008 and 2011 were selected. A SCB Health scoring system was developed to assess the condition of the SCB using 3-Tesla MRI. The SCB Health score is based on the amount of edema, subchondral cyst diameter, qualitative change in SCBP morphology and thickness change of the SCBP (Table 1). Nine of the twenty patients had two follow-up MRIs, and differences in their scores were calculated. The clinical evaluation was assessed using the Foot and Ankle Outcome Scores (FAOS) preoperatively and at final follow-up. Results: At first follow-up MRI, 65% of patients had mild or greater edema, 40% had subchondral cysts, 65% had irregularity or collapse of their SCBP and 85% had a >25% change in SCBP thickness. The overall SCB Health score of 90% of patients were abnormal. Of the nine patients who had a subsequent follow-up MRIs, the mean time between the first and second study was 22±6 months. The scores between the two time points were not statistically significant (p=0.347, p=0.559, p=0.169, p=0.347 p=0.154 for edema, subchondral cyst diameter, qualitative SCBP measurements, SCBP thickness change and overall SCB Health score, respectively). The mean FAOS score improved significantly from 55.5±16.8 preoperatively to 76.0±12.3 at final follow-up (p<0.05). Conclusion: The SCB and SCBP were not completely healed in 90% of patients at a mean 18 months follow-up following microfracture of the talus. Subsequently, morphological changes were not restored at a mean 43 months at second follow-up in a smaller subset of patients. Most previous studies have focused on the degeneration of the articular cartilage layer, and its effect on clinical outcomes. The authors of current study believe that looking at the changes in the SCB may provide additional information as to why BMS procedures fail in the long-term.

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