Ingested fish bone induced intestinal perforations are seldom diagnosed preoperatively due to incomplete patient history taking and difficulties in image evidence identification.Most literature suggests early surgical...Ingested fish bone induced intestinal perforations are seldom diagnosed preoperatively due to incomplete patient history taking and difficulties in image evidence identification.Most literature suggests early surgical intervention to prevent sepsis and complications resulting from fish bone migrations.We report the case of a 44-year-old man suffered from acute abdomen induced by a fish bone micro-perforation.The diagnosis was supported by computed tomography(CT) imaging of fish bone lodged in distal ileum and a history of fish ingestion recalled by the patient.Medical treatment was elected to manage the patient's condition instead of surgical intervention.The treatment resulted in a complete resolution of abdominal pain on hospital day number 4 without complication.Factors affecting clinical treatment decisions include the nature of microperforation,the patient's good overall health condition,and the early diagnosis before sepsis signs develop.Micro-perforation means the puncture of intestine wall without CT evidence of free air,purulent peritoneum or abscess.We subsequently reviewed the literature to support our decision to pursue medical instead of surgical intervention.展开更多
The vibro-acoustic responses and sound absorption characteristics of two kinds of periodically stiffened micro-perforated plates are analyzed theoretically. The connected periodical structures of the stiffened plates ...The vibro-acoustic responses and sound absorption characteristics of two kinds of periodically stiffened micro-perforated plates are analyzed theoretically. The connected periodical structures of the stiffened plates can be ribs or block-like structures. Based on fundamental acoustic formulas of the micro-perforated plate of Maa and Takahashi, semi-analytical models of the vibrating stiffened plates are developed in this paper. Approaches like the space harmonic method, Fourier transforms and finite element method （FEM） are adopted to investigate both kinds of the stiffened plates. In the present work, the vibro-acoustic responses of micro-perforated stiffened plates in the wavenumber space are expressed as functions of plate displacement amplitudes. After approximate numerical solutions of the amplitudes, the vibration equations and sound absorption coefficients of the two kinds of stiffened plates in the physical space are then derived by employing the Fourier inverse transform. In numerical examples, the effects of some physical parameters, such as the perforation ratio, incident angles and periodical distances etc., on the sound absorption performance are examined. The proposed approaches are also validated by comparing the present results with solutions of Takahashi and previous studies of stiffened plates. Numerical results indicate that the flexural vibration of the plate has a signif- icant effect on the sound absorption coefficient in the water but has little influence in the air.展开更多
A kind of hybrid device for acoustic noise reduction and vibration energy harvesting based on the silicon micro- perforated panel （MPP） resonant structure is investigated in the article. The critical parts of the de...A kind of hybrid device for acoustic noise reduction and vibration energy harvesting based on the silicon micro- perforated panel （MPP） resonant structure is investigated in the article. The critical parts of the device include MPP and energy harvesting membranes. They are all fabricated by means of silicon micro-electro-mechanical systems （MEMS） tech- nology. The silicon MPP has dense and accurate micro-holes. This noise reduction structure has the advantages of wide band and higher absorption coefficients. The vibration energy harvesting part is formed by square piezoelectric membranes arranged in rows. ZnO material is used as it has a good compatibility with the fabrication process. The MPP, piezo- electric membranes, and metal bracket are assembled into a hybrid device with multifunctions. The device exhibits good performances of acoustic noise absorption and acoustic-electric conversion. Its maximum open circuit voltage achieves 69.41 mV.展开更多
This paper presents the development and performance of micro-perforated panels(MPP)from natural fiber reinforced composites.The MPP is made of Polylactic Acid(PLA)reinforced with Oil Palm Empty Fruit Bunch Fiber(OPEFB...This paper presents the development and performance of micro-perforated panels(MPP)from natural fiber reinforced composites.The MPP is made of Polylactic Acid(PLA)reinforced with Oil Palm Empty Fruit Bunch Fiber(OPEFBF).The investigation was made by varying the fiber density,air gap,and perforation ratio to observe the effect on the Sound Absorption Coefficient(SAC)through the experiment in an impedance tube.It is found that the peak level of SAC is not affected,but the peak frequency shifts to lower frequency when the fiber density is increased.This phenomenon might be due to the presence of porosity in the inner wall of the holes.Increasing or decreasing the air gap and perforation ratio shifts the peaks of acoustic absorption either way.展开更多
A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coeff...A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coefficient of the acoustic structure are calculated via means of equivalent circuit.MATLAB is used to calculate the relationship between the parameters of the ontology structure and the sound-absorption coefficient and the sound insulation.It is revealed that the sound barrier of the new ontology structure is 7.659.80 dB,which is more than the sound barrier of the traditional reflective structures.The relationships among the parameters of sound-absorption structure,sound-absorption coefficient,and sound insulation performance are obtained.In addition,the parameters can be transformed to satisfy the noise reduction requirements of various road sections,which has a admirable adaptability.The acoustic barrier can have tremendous acoustic performance only if there is a splendid sound insulation in the traffic noise frequency band.展开更多
Mitigating low-frequency noise poses a significant challenge for acoustic engineers,due to their long wavelength,with conventional porous sound absorbers showing limitations in attenuating such noise.An effective stra...Mitigating low-frequency noise poses a significant challenge for acoustic engineers,due to their long wavelength,with conventional porous sound absorbers showing limitations in attenuating such noise.An effective strategy involves combining porous materials with micro-perforated plates(MPP)to address this issue.Given the significant impact of structural variables like panel thickness,hole diameter,and air gap on the acoustic characteristics of MPP,achieving the optimal condition demands numerous sample iterations.The impedance tube’s considerable expense for sound absorption measurement and the substantial cost involved in fabricating each sample using a 3D printer underscore the advantage of utilizing simulation methods to attain the optimal state.This study focuses on optimizing low-frequency enhancement by investigating key parameters.Using the Finite Element Numerical Method(FEM)in COMSOL software,a composite panel was constructed comprising date palm fiber layers,an intervening air layer,and MPP.The study explored the arrangement of these layers and the impact of parameters like hole diameter,plate thickness,and perforation ratio on acoustic behavior.The selected optimal parameter at each stage was consistently maintained for subsequent steps.Results revealed that layer arrangement significantly influenced acoustic characteristics.Placing the MPP layer before the porous material yielded superior low-frequency performance.Optimizing low-frequency behavior involved reducing hole diameter and perforation ratio while increasing plate thickness.Elevating the porous material’s thickness relative to the air layer behind the MPP enhanced absorption peak and resonance frequency.In conclusion,halving the porous layer’s thickness while incorporating an air layer and single MPP proved more effective than using a thick porous material.This approach not only reduces costs and space requirements but also enhances low-frequency performance.The study highlights the precision of numerical methods like FEM,reducing the need for resource-intensive direct methods and associated laboratory expenses.展开更多
The purpose of the research is to assess the sound absorption performance(SAP)of acoustic metamaterials made of double-layer Nomex honeycomb structures in which a micro-orifice corresponds to a honeycomb unit.For this...The purpose of the research is to assess the sound absorption performance(SAP)of acoustic metamaterials made of double-layer Nomex honeycomb structures in which a micro-orifice corresponds to a honeycomb unit.For this purpose,the influences of structural parameters on the SAP of acoustic metamaterials were investigated by using experimental testing and a validated theoretical model.In addition,the sandwich structure was optimized by the genetic algorithm.The research shows that the panel thickness and micro-orifice diameter mainly affect the second resonant frequency and second peak sound absorption coefficient(SAC)of the structure.The unit cell size is found to influence the first and second resonant frequencies and two peaks of the SAC.An extremely low side-length of the honeycomb core decreases the SAP of the structure for low-frequency noise signals.Additionally,the sandwich structure presents a better SAP when the diameter of micro-orifices on the front micro-perforated panel(MPP)exceeds that of the back MPP.The sandwich structure shows better noise reduction performance after the optimization aiming at the noise frequency outside trains.展开更多
The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the...The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the acoustic impedance and acoustic absorption coefficient of the new muffler structure are calculated by acoustic electric analogy method,and then the noise attenuation is calculated.When the new muffler structure parameters change,the relationship among the noise frequency,the sound absorption coefficient and the noise attenuation is calculated by using MATLAB.Finally,the calculated results are compared with the experimental data to verify the correctness of the theoretical calculation.The variation of resonance peak,resonance frequency and attenuation band width of each structural parameter is analyzed by the relation curve.The conclusion shows that it is feasible to use multilayer sound absorbing materials as the body structure of the new muffler.And the influence relationship between the change of various parameters of the sound absorption structure with the sound absorption coefficient and noise attenuation is obtained.展开更多
A composite absorber made of a polyurethane sponge and multi-layer micro-perforated plates is pre-sented in this study.Results from an acoustic impedance tube test show that the polyurethane sponge can exhibits higher...A composite absorber made of a polyurethane sponge and multi-layer micro-perforated plates is pre-sented in this study.Results from an acoustic impedance tube test show that the polyurethane sponge can exhibits higher low-frequency sound absorption in front of the micro-perforated plate,while sound absorption at medium and high-frequencies remains low.The physical mechanism behind this is that the micro-perforated plate increases the denpth cavity.If the polyurethane sponge is placed behind the micro-perforated plate,the amplitude of the original absorption peak will remain constant,but the ab-sorption peaks will shift to lower frequencies.The reason for this phenomenon is that porous materials with low flow resistance can be approximately equivalent to fluid,which not only does not affect the res-onance absorption coefficient of micro-perforated plate,but also makes the peaks move to low frequency.This study has the potential applications in the sound absorption design of composite structure.展开更多
1 Introduction Early attempts to create a sound absorber which would function without the involvement of any fibrous or porous damping material go far back to K. A. Veliszhanina, S. N. Rschevkin and others as was out...1 Introduction Early attempts to create a sound absorber which would function without the involvement of any fibrous or porous damping material go far back to K. A. Veliszhanina, S. N. Rschevkin and others as was outlined in Ref. [1]. 30 years ago, D. Y. MAA[2] was first in proposing a practicable design concept and calculation model for Micro-Perforated Absorber （MPA） prototypes which still forms the basis for various applications. During the past 12 years the Fraunhofer IBP developed a whole family of MPA products in close cooperation with 8 or more industrial partners operating in a variety of widely differing market segments. Meanwhile a large number of MPA modules and surface elements have evolved from MAA＇s creative pioneer work. More and more ambitious acousticians have, more recently, caught on this attractive idea of employing absorbers made of non-fibrous, non-abrasive materials with non-polluting, almost closed and optically attractive surfaces. MPA structures have played an important part in a long-standing and on-going effort at IBP to establish novel Alternative Fibreless Absorber （ALFA） tools for a better noise control and acoustic comfort.展开更多
The geometric parameters of micro-perforated panels with irregular holes cannot be directly known,making it difficult to calculate the sound absorption performance.Therefore,we propose a method of estimating the geome...The geometric parameters of micro-perforated panels with irregular holes cannot be directly known,making it difficult to calculate the sound absorption performance.Therefore,we propose a method of estimating the geometric parameters of micro-perforated panels.The irregular holes are treated as equivalent circular ones,and the model of estimating the geometric parameters is established by using Maa's theory about the panel with circular holes.The result of the parameter estimation of a type of micro-perforated panel is used to predict the absorption performance,resulting in good agreement with experiments.According to the influences of the geometric parameters of the panel on the high absorption region,we discuss the relationship between the application limit of Maa's theory and the geometric parameters,and investigate the evolution law of the sound absorption performance when the panel is polluted by dust.If the parameters of the panel are designed near the center of the high absorption region,large value of the application limit of Maa's theory can be obtained;and if the parameters are located in the upper right part of the high absorption region,a certain degree of dust pollution of the panel does not decrease the sound absorption performance.展开更多
文摘Ingested fish bone induced intestinal perforations are seldom diagnosed preoperatively due to incomplete patient history taking and difficulties in image evidence identification.Most literature suggests early surgical intervention to prevent sepsis and complications resulting from fish bone migrations.We report the case of a 44-year-old man suffered from acute abdomen induced by a fish bone micro-perforation.The diagnosis was supported by computed tomography(CT) imaging of fish bone lodged in distal ileum and a history of fish ingestion recalled by the patient.Medical treatment was elected to manage the patient's condition instead of surgical intervention.The treatment resulted in a complete resolution of abdominal pain on hospital day number 4 without complication.Factors affecting clinical treatment decisions include the nature of microperforation,the patient's good overall health condition,and the early diagnosis before sepsis signs develop.Micro-perforation means the puncture of intestine wall without CT evidence of free air,purulent peritoneum or abscess.We subsequently reviewed the literature to support our decision to pursue medical instead of surgical intervention.
基金supported by the National Natural Science Foundation of China(51405276 and 50875030)
文摘The vibro-acoustic responses and sound absorption characteristics of two kinds of periodically stiffened micro-perforated plates are analyzed theoretically. The connected periodical structures of the stiffened plates can be ribs or block-like structures. Based on fundamental acoustic formulas of the micro-perforated plate of Maa and Takahashi, semi-analytical models of the vibrating stiffened plates are developed in this paper. Approaches like the space harmonic method, Fourier transforms and finite element method （FEM） are adopted to investigate both kinds of the stiffened plates. In the present work, the vibro-acoustic responses of micro-perforated stiffened plates in the wavenumber space are expressed as functions of plate displacement amplitudes. After approximate numerical solutions of the amplitudes, the vibration equations and sound absorption coefficients of the two kinds of stiffened plates in the physical space are then derived by employing the Fourier inverse transform. In numerical examples, the effects of some physical parameters, such as the perforation ratio, incident angles and periodical distances etc., on the sound absorption performance are examined. The proposed approaches are also validated by comparing the present results with solutions of Takahashi and previous studies of stiffened plates. Numerical results indicate that the flexural vibration of the plate has a signif- icant effect on the sound absorption coefficient in the water but has little influence in the air.
基金Project supported by the National Natural Science Foundation of China(Grant No.51305423)the National Basic Research Program of China(GrantNo.2011CB302104)
文摘A kind of hybrid device for acoustic noise reduction and vibration energy harvesting based on the silicon micro- perforated panel （MPP） resonant structure is investigated in the article. The critical parts of the device include MPP and energy harvesting membranes. They are all fabricated by means of silicon micro-electro-mechanical systems （MEMS） tech- nology. The silicon MPP has dense and accurate micro-holes. This noise reduction structure has the advantages of wide band and higher absorption coefficients. The vibration energy harvesting part is formed by square piezoelectric membranes arranged in rows. ZnO material is used as it has a good compatibility with the fabrication process. The MPP, piezo- electric membranes, and metal bracket are assembled into a hybrid device with multifunctions. The device exhibits good performances of acoustic noise absorption and acoustic-electric conversion. Its maximum open circuit voltage achieves 69.41 mV.
基金sponsored by Taylor’s University Flagship Research Grant TUFR/2017/001/05。
文摘This paper presents the development and performance of micro-perforated panels(MPP)from natural fiber reinforced composites.The MPP is made of Polylactic Acid(PLA)reinforced with Oil Palm Empty Fruit Bunch Fiber(OPEFBF).The investigation was made by varying the fiber density,air gap,and perforation ratio to observe the effect on the Sound Absorption Coefficient(SAC)through the experiment in an impedance tube.It is found that the peak level of SAC is not affected,but the peak frequency shifts to lower frequency when the fiber density is increased.This phenomenon might be due to the presence of porosity in the inner wall of the holes.Increasing or decreasing the air gap and perforation ratio shifts the peaks of acoustic absorption either way.
基金National Natural Science Foundation of China(No.51175195)Guiding Plan of Textile Industry Federation,China(No.2017053)
文摘A new acoustic barrier structure with resonant sound of micro-perforation board absorption structure and impedance composite sound-absorption structure is proposed.The acoustic impedance and the sound-absorption coefficient of the acoustic structure are calculated via means of equivalent circuit.MATLAB is used to calculate the relationship between the parameters of the ontology structure and the sound-absorption coefficient and the sound insulation.It is revealed that the sound barrier of the new ontology structure is 7.659.80 dB,which is more than the sound barrier of the traditional reflective structures.The relationships among the parameters of sound-absorption structure,sound-absorption coefficient,and sound insulation performance are obtained.In addition,the parameters can be transformed to satisfy the noise reduction requirements of various road sections,which has a admirable adaptability.The acoustic barrier can have tremendous acoustic performance only if there is a splendid sound insulation in the traffic noise frequency band.
文摘Mitigating low-frequency noise poses a significant challenge for acoustic engineers,due to their long wavelength,with conventional porous sound absorbers showing limitations in attenuating such noise.An effective strategy involves combining porous materials with micro-perforated plates(MPP)to address this issue.Given the significant impact of structural variables like panel thickness,hole diameter,and air gap on the acoustic characteristics of MPP,achieving the optimal condition demands numerous sample iterations.The impedance tube’s considerable expense for sound absorption measurement and the substantial cost involved in fabricating each sample using a 3D printer underscore the advantage of utilizing simulation methods to attain the optimal state.This study focuses on optimizing low-frequency enhancement by investigating key parameters.Using the Finite Element Numerical Method(FEM)in COMSOL software,a composite panel was constructed comprising date palm fiber layers,an intervening air layer,and MPP.The study explored the arrangement of these layers and the impact of parameters like hole diameter,plate thickness,and perforation ratio on acoustic behavior.The selected optimal parameter at each stage was consistently maintained for subsequent steps.Results revealed that layer arrangement significantly influenced acoustic characteristics.Placing the MPP layer before the porous material yielded superior low-frequency performance.Optimizing low-frequency behavior involved reducing hole diameter and perforation ratio while increasing plate thickness.Elevating the porous material’s thickness relative to the air layer behind the MPP enhanced absorption peak and resonance frequency.In conclusion,halving the porous layer’s thickness while incorporating an air layer and single MPP proved more effective than using a thick porous material.This approach not only reduces costs and space requirements but also enhances low-frequency performance.The study highlights the precision of numerical methods like FEM,reducing the need for resource-intensive direct methods and associated laboratory expenses.
基金Project(51775558)supported by the National Natural Science Foundation of ChinaProject(2019 JJ 30034)supported by the Natural Science Foundation for Excellent Youth Scholars of Hunan Province,ChinaProject(20181053303 gg)supported by the Training Objects of Young-Middle-Aged Backbone Teacher in Ordinary Universities of Hunan Province,China。
文摘The purpose of the research is to assess the sound absorption performance(SAP)of acoustic metamaterials made of double-layer Nomex honeycomb structures in which a micro-orifice corresponds to a honeycomb unit.For this purpose,the influences of structural parameters on the SAP of acoustic metamaterials were investigated by using experimental testing and a validated theoretical model.In addition,the sandwich structure was optimized by the genetic algorithm.The research shows that the panel thickness and micro-orifice diameter mainly affect the second resonant frequency and second peak sound absorption coefficient(SAC)of the structure.The unit cell size is found to influence the first and second resonant frequencies and two peaks of the SAC.An extremely low side-length of the honeycomb core decreases the SAP of the structure for low-frequency noise signals.Additionally,the sandwich structure presents a better SAP when the diameter of micro-orifices on the front micro-perforated panel(MPP)exceeds that of the back MPP.The sandwich structure shows better noise reduction performance after the optimization aiming at the noise frequency outside trains.
基金National Natural Science Foundation of China(Nos.51705545 and 15A460041)。
文摘The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the acoustic impedance and acoustic absorption coefficient of the new muffler structure are calculated by acoustic electric analogy method,and then the noise attenuation is calculated.When the new muffler structure parameters change,the relationship among the noise frequency,the sound absorption coefficient and the noise attenuation is calculated by using MATLAB.Finally,the calculated results are compared with the experimental data to verify the correctness of the theoretical calculation.The variation of resonance peak,resonance frequency and attenuation band width of each structural parameter is analyzed by the relation curve.The conclusion shows that it is feasible to use multilayer sound absorbing materials as the body structure of the new muffler.And the influence relationship between the change of various parameters of the sound absorption structure with the sound absorption coefficient and noise attenuation is obtained.
基金by Aeronautical Science Foundation of China(Grant 20181553015)Foundation of Shaanxi Educational Committee(Grant 2018BSHYDZZ03)+1 种基金the National Natural Science Foundation of China(Grant 11704314)China Postdoctoral Sci-ence Foundation(Grant 2018M631194).
文摘A composite absorber made of a polyurethane sponge and multi-layer micro-perforated plates is pre-sented in this study.Results from an acoustic impedance tube test show that the polyurethane sponge can exhibits higher low-frequency sound absorption in front of the micro-perforated plate,while sound absorption at medium and high-frequencies remains low.The physical mechanism behind this is that the micro-perforated plate increases the denpth cavity.If the polyurethane sponge is placed behind the micro-perforated plate,the amplitude of the original absorption peak will remain constant,but the ab-sorption peaks will shift to lower frequencies.The reason for this phenomenon is that porous materials with low flow resistance can be approximately equivalent to fluid,which not only does not affect the res-onance absorption coefficient of micro-perforated plate,but also makes the peaks move to low frequency.This study has the potential applications in the sound absorption design of composite structure.
文摘1 Introduction Early attempts to create a sound absorber which would function without the involvement of any fibrous or porous damping material go far back to K. A. Veliszhanina, S. N. Rschevkin and others as was outlined in Ref. [1]. 30 years ago, D. Y. MAA[2] was first in proposing a practicable design concept and calculation model for Micro-Perforated Absorber （MPA） prototypes which still forms the basis for various applications. During the past 12 years the Fraunhofer IBP developed a whole family of MPA products in close cooperation with 8 or more industrial partners operating in a variety of widely differing market segments. Meanwhile a large number of MPA modules and surface elements have evolved from MAA＇s creative pioneer work. More and more ambitious acousticians have, more recently, caught on this attractive idea of employing absorbers made of non-fibrous, non-abrasive materials with non-polluting, almost closed and optically attractive surfaces. MPA structures have played an important part in a long-standing and on-going effort at IBP to establish novel Alternative Fibreless Absorber （ALFA） tools for a better noise control and acoustic comfort.
基金supported by the General Project of College Natural Science Research of Jiangsu Province(16KJD460002)the National Natural Science Foundation of China(51605209)
文摘The geometric parameters of micro-perforated panels with irregular holes cannot be directly known,making it difficult to calculate the sound absorption performance.Therefore,we propose a method of estimating the geometric parameters of micro-perforated panels.The irregular holes are treated as equivalent circular ones,and the model of estimating the geometric parameters is established by using Maa's theory about the panel with circular holes.The result of the parameter estimation of a type of micro-perforated panel is used to predict the absorption performance,resulting in good agreement with experiments.According to the influences of the geometric parameters of the panel on the high absorption region,we discuss the relationship between the application limit of Maa's theory and the geometric parameters,and investigate the evolution law of the sound absorption performance when the panel is polluted by dust.If the parameters of the panel are designed near the center of the high absorption region,large value of the application limit of Maa's theory can be obtained;and if the parameters are located in the upper right part of the high absorption region,a certain degree of dust pollution of the panel does not decrease the sound absorption performance.
