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Search Results: 1 - 10 of 5176 matches for " Cavity Noise "
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Numerical Modelling of Aerodynamic Noise in Compressible Flows  [PDF]
S?awomir Dykas, Sebastian Rulik, W?odzimierz Wroblewski
Open Journal of Fluid Dynamics (OJFD) , 2012, DOI: 10.4236/ojfd.2012.23007
Abstract: The solution of the AeroAcoustics (CAA) problems by means of the Direct Numerical Simulation (DNS) or even the Large Eddy Simulation (LES) for a large computational domain is very time consuming and cannot be applied widely for engineering applications. In this paper the in-house CFD and CAA codes are presented. The in-house CFD code is based on the LES approach whereas the CAA code is an acoustic postprocessor solving the non-linearized Euler equations for fluctuating (acoustic) variables. These codes are used to solve the aerodynamically generated sound field by a flow over a rectangular cavity with inlet Mach number 0.53.
Analysis on Physical Mechanism of Sound Generation inside Cavities Based on Acoustic Analogy Method  [PDF]
Dangguo Yang, Jianqiang Li, Jun Liu, Yi Zhang, Yaohua Li
Open Journal of Fluid Dynamics (OJFD) , 2013, DOI: 10.4236/ojfd.2013.31003
Abstract: Analysis of coupling aerodynamics and acoustics are performed to investigate the self-sustained oscillation and aerodynamic noise in two-dimensional flow past a cavity with length to depth ratio of 2 at subsonic speeds. The large eddy simulation (LES) equations and integral formulation of Ffowcs-Williams and Hawings (FW-H) are solved for the cavity with same conditions as experiments. The obtained density-field agrees well with Krishnamurty’s experimental schlieren photograph, which simulates flow-field distributions and the direction of sound wave radiation. The simulated self-sustained oscillation modes inside the cavity agree with Rossiter’s and Heller’s predicated results, which indicate frequency characteristics are obtained. Moreover, the results indicate that the feedback mechanism that new shedding-vortexes induced by propagation of sound wave created by the impingement of the shedding-vortexes in the shear-layer and rear cavity face leads to self-sustained oscillation and high noise inside the cavity. The peak acoustic pressure occurs in the first oscillation mode and the most of sound energy focuses on the low-frequency region.
The Effect of Tire Design Parameters on the Force Transmissibility  [PDF]
Woo Cheol Park, Hee Kyu Lim, Kyoung Moon Jeong, Tan Wan Kim
Open Journal of Applied Sciences (OJAppS) , 2018, DOI: 10.4236/ojapps.2018.810035
Abstract: A finite element modeling technique is employed in this paper to predict the force transmissibility of tire-cavity-wheel assembly under a free-fixed condition. The tire and wheel force transmissibility is factor in structure borne road noise performance. In order to improve structure borne noise, it is required to lower the 1st peak frequency of force transmissibility. This paper presents an application of finite element analysis modeling along with experimental verification to predict the force transmissibility of tire and wheel assembly. The results of finite element analysis for force transmissibility are shown to be in good agreement with the results from the indoor test. In order to improve structure borne noise, it is required to lower the 1st peak frequency of force transmissibility. And, the effect of the tire design parameters such as the density and modulus of a rubber and the cord stiffness on the force transmissibility is discussed. It is found that the prediction of the force transmissibility model using finite element analysis will be useful for the improvement of the road noise performance of passenger car tire.
High temperature superconducting (HTS) C-band oscillator with phase noise of 134 dBc/Hz
Hong Li,Aisheng He,Tiefeng Shi,Zhonglin Gong,Shunzhou Li,Yongwei Sun,Yusheng He
Chinese Science Bulletin , 2002, DOI: 10.1360/02tb9098
Abstract: A high Q HTS cavity resonator with resonating frequency f0= 5.624 GHz was fabricated using high quality HTS film and high purity sapphire. The unloaded quality factor of the HTS resonator was as high as Q u= 1.09xl06 at the nitrogen temperature, 77 K. A HTS local oscillator combining the high Q cavity resonator with a C-band low noise GaAs HEMT amplifier was then designed and constructed. The phase noise of the oscillator, measured by a HP 3048A noise measurement system, is 134 dBc/Hz at 10 kHz offset when the temperature is 77 K. This result is close to the best level reported by other groups in the world.
High temperature super-conducting (HTS) C-band oscillator with phase noise of -134 dBc/Hz

LI Hong,

科学通报(英文版) , 2002,
Abstract: A high Q HTS cavity resonator with resonating frequency fo = 5.624 GHz was fabricated using high quality HTS film and high purity sapphire. The unloaded quality factor of the HTS resonator was as high as Qt = 1.09×106 at the nitrogen temperature, 77 K. A HTS local oscillator combining the high Q cavity resonator with a C-band low noise GaAs HEMT amplifier was then designed and constructed.The phase noise of the oscillator, measured by a HP 3048A noise measurement system, is -134 dBc/Hz at 10 kHz offset when the temperature is 77 K. This result is close to the best level reported by other groups in the world.
Some applications of neural networks in microwave modeling
Milovanovi? Bratislav D.,Markovi? Vera,Marinkovi? Zlatica D.,Stankovi? Zoran 2
Journal of Automatic Control , 2003, DOI: 10.2298/jac0301039m
Abstract: This paper presents some applications of neural networks in the microwave modeling. The applications are related to modeling of either passive or active structures and devices. Modeling is performed using not only simple multilayer perception network (MLP) but also advanced knowledge based neural network (KBNN) structures.
What Does “Noise Pollution” Mean?  [PDF]
Alice Elizabeth González
Journal of Environmental Protection (JEP) , 2014, DOI: 10.4236/jep.2014.54037
Abstract:

Noise features different characteristics that make it different from every other “classic” pollutant. Noise is invisible; it does not smell; it disappears when the source is turned off and leaves no traces in the environment. In addition, when people perceive something wrong about their hearing capacity, it is often long time after the beginning of noise exposure. This fact contributes to strengthening the misconception that noise is not harmful to human health or, at least, efforts and funds aim preferably at controling and decreasing the emission of other pollutants. Adding to this, most people tend to consider that noise is the price to pay for accessing to the amenities of the Technological Era and it is indivisible and inevitably linked to them. Last but not least, noise pollution could adversely affect ecosystems and ecological services. Then, how is it possible to convince the decision makers that noise pollution is one of the major current environmental problems? The aim of this paper is to discuss step by step the applicability of noise of a “pollution” definition, as a way to ease the understanding that lowering environmental noise levels should be prioritized: because it will lead to a healthier and better society.

Impact of Noise on Health: The Divide between Policy and Science  [PDF]
Arline L. Bronzaft
Open Journal of Social Sciences (JSS) , 2017, DOI: 10.4236/jss.2017.55008
Abstract: In her chapter “Sources of Noise” in Noise and Health, Annette Zaner [1] writes that sounds have been environmental pollutants for thousands of years, citing examples of stories of loud music in the Old Testament and noisy delivery wagons in ancient times. The Industrial Revolution and urbanization in more recent times raised the decibel levels in our communities, especially with the growth in transportation on the roads, on the rails and in the air, as well as the growth of noise polluting products. The proliferation of boom cars, cell phones and wind turbines during the past twenty years has made our world even noisier. Studies have been carried out that have demonstrated the potential impact of these noises on our mental and physical health, and there have been some efforts to lessen some of the intrusive sounds, e.g. aircraft and road traffic noise, but there is still too little attention paid to the deleterious effects of noise. While noise complaints top the list of complaints in major cities worldwide and noise even threatens the natural sound systems of our planet, there is no movement globally to address the noise pollutant. The following paper will examine the research linking noise to health effects, question why governments have not seriously attempted to lower noise levels and suggest ways to lessen the din. Doing so will not only be beneficial to our health and well-being but it would also be wise economically.
Cavernous Hemangioma of the Nasal Cavity  [PDF]
Peter Kalina, Jeffrey Rykken
Open Journal of Medical Imaging (OJMI) , 2011, DOI: 10.4236/ojmi.2011.12007
Abstract: A 22 year old six month pregnant female presented with right eye tearing, proptosis and nasal congestion. CT revealed a large right nasal cavity mass with involvement of the ethmoids, right maxillary sinus, lamina papyracea, cribriform plate and nasal septum. There was significant remodeling of the right cribriform plate with mild extra-axial intracranial and mild intraorbital extension. Transnasal endoscopic excision confirming the diagnosis of cavernous hemangioma of the nasal cavity. Hemangiomas are benign slow-growing vascular neoplasms classified as capillary, cavernous or mixed. Hemangiomas of the nasal cavity and paranasal sinuses are very rare with only a few reported cases. The occurrence and growth of these lesions during pregnancy may be related to increased blood volume or hormonal factors. The most common therapeutic option is complete surgical resection via transnasal endoscopic approach. Pre-operative embolization may be utilized in some cases to decrease the risk of intraoperative bleeding.
Melanoma of the Oral Cavity: About Two Cases and Review of Literature  [PDF]
F. Elomrani, H. Mouzount, I. Ouziane, R. Khmamouch, S. lkhoyali, A. Boukir, M. ElKabous, S. Boutayeb, H. Mrabti, B. Elkhannoussi, H. Errihani
International Journal of Clinical Medicine (IJCM) , 2013, DOI: 10.4236/ijcm.2013.44033
Abstract:

Mucosal malignant melanoma of the oral cavity is an extremely rare condition. It has a poor prognosis. Here we report two typical cases of malignant melanoma. In the first case, 64 years old man developed an exophytic tumor in the hard palate. Head and neck and chest computerized tomography scan showed a large aggressive tumor of the hard palate. The patient also had multiple lung metastases and a cervical lymph node. The second case is a 73 years old woman presenting a burgeoning mass on the right palate. Facial CT reveals a malignant tumor lateralized in the right palate with ipsilateral metastatic lymph nodes. Histological with immunohistochemical studies assigned both cases to a malignant melanoma. Due to the rarity of oral malignant melanomas, case reports are a necessary source of information.

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