Influence of air masses on microphone vibration sensitivity

A study is presented of the primary design parameters that influence the vibration sensitivity of a microphone. The sensitivity to vibration is generally determined by the mass of the pressure-sensing diaphragm along with the mass of air that moves with it. The sound-sensing performance is improved as the pressure-sensing diaphragm is made thinner, but for a thin enough diaphragm, the moving air mass is not negligible relative to that of the diaphragm itself. In the present study, we develop a simple duct-acoustic model to account for the effect of the co-vibrating air. It is shown that an idealized massless, thin microphone diaphragm will still produce unwanted vibration signal due to acceleration of the air masses within the microphone. For a small microphone, the predicted pressure related acceleration sensitivity is found to be a simple function of the mass per unit area of the air inside of the microphone package. The acceleration sensitivity predicted using a finite element model of a one micrometer thick clamped flexible silicon diaphragm agrees with that predicted by the simple duct model. Measured and predicted acceleration sensitivities are compared for several MEMS and sub-miniature electret microphones of different back volume lengths . It is found that the primary design parameter determining vibration sensitivity for these microphones is the effective length of the column of air inside the microphone’s packaging. Microphones that have longer air-filled volumes had greater pressure related acceleration sensitivity.

Experimental study on flow over arced-plan porous weirs

Unlike conventional impermeable weirs, porous weirs without clogging the flow and passage of aquatic life with increased aeration and aerobic reactions with minimal negative effects on the environment are known as environmentally friendly structures. This study experimentally investigates the hydraulic performance of Arced-Plan Porous Weirs (APPWs) in different hydraulic and geometric conditions. For this purpose, four different porous and two solid weirs were examined. Experiments were conducted in a horizontal laboratory flume with length, width, and height of 20, 0.6, and 0.5 m, respectively, for a wide range of flow rates, particle sizes, and three arc lengths. Results showed that increasing filling material sizes increases the free discharge coefficient and reduces the submerged Discharge Reduction Factor (DRF). It was also concluded that the weirs’ effective length significantly impacts the free discharge coefficient and has no significant effect on the threshold submergence index and submerged DRF. Unlike solid weirs, the threshold submergence of porous weirs occurs at a downstream depth lower than the weir's height. Finally, according to the dimensional analysis and Gene-Expression Programming (GEP) approach, three relations were extracted to calculate the free discharge coefficient, threshold submergence index, and submerged discharge reduction factor for APPWs.

Investigation of transport mechanisms induced by filament-coupling bridges- network in Bi-2212 wires

One of the features unique in Bi-2212/Ag wires is the network of bridges between the filaments formed by grains grown through the Ag matrix during the partial-melt heat treatment process. Although these interconnections favor a redistribution of the current among the filaments allowing high critical current density, they represent a strong electrical coupling between the filaments themself. Such a coupling increases the AC losses, present also in case of charge and discharge of DC magnets, principal applications of this kind of superconductor. In this work, through transport and magnetic measurements and their comparison, we study the behavior of these bridges as a function of applied magnetic field and temperature and the implications they have on the electrical coupling. The experiment has been performed on two multifilamentary wires prepared by GDG-PIT process starting from two commercial Bi-2212 precursor powders: Nexans and Engi-Mat. The reported results provide information on the effective length scale on which the filaments are coupled as a function of the field and temperature and we believe that such findings can be useful in magnet design.

Quantitative Evidence for the Dependence of Highly Crystalline Single Wall Carbon Nanotube Synthesis on the Growth Method

We present a study quantitatively demonstrating that the method of synthesis (gas phase, fixed bed, non-fixed bed) represents a determining factor in the level of crystallinity in growing single wall carbon nanotubes (SWCNTs). Using far infrared spectroscopy, the “effective length” (associated with the level of crystallinity) was estimated for CNTs grown using various synthetic methods (lab-produced and supplemented by commercially purchased SWCNTs) as a metric for crystallinity (i.e., defect density). Analysis of the observed “effective lengths” showed that the SWCNTs fell into two general groups: long and short (high and low crystallinity) synthesized by gas-phase methods and all other supported catalyst methods, respectively. Importantly, the “long” group exhibited effective lengths in the range of 700–2200 nm, which was greater than double that of the typical values representing the “short” group (110–490 nm). These results highlight the significant difference in crystallinity. We interpret that the difference in the crystallinity stemmed from stress concentration at the nanotube-catalyst interface during the growth process, which originated from various sources of mismatch in growth rates (e.g., vertically aligned array) as well as impact stress from contact with other substrates during fluidization or rotation. These results are consistent with well-accepted belief, but now are demonstrated quantitatively.

Influence of Roadway Cross-Section Shape on Gas Explosion Shock Wave Law in U-Type Ventilation Working Faces

In U-shaped ventilation working face, different tunnel section shapes are one of the important factors affecting the propagation of gas explosion shock wave. In order to study the propagation law of gas explosion shock wave in working face, the numerical simulation study was carried out by using Fluent simulation software combined with the actual situation of gas explosion in #415 working face of Chenjiashan Coal Mine in Shaanxi Province. By constructing a three-dimensional mathematical and physical model, a simulation study of the upper-corner gas explosion was carried out. The results are described as follows. (1) After the gas explosion shock wave propagates 40 m, the overpressure peak equidistant difference tends to be stable and attenuates and propagates in the form of a single shock wave. The study determines that the effective length of the U-shaped ventilation inlet/return tunnel is 40 m. (2) When the tunnel section is trapezoidal, the initial overpressure of the gas explosion shock wave propagating to the inlet/return airway is the highest, followed by rectangular and semicircular arches, but the internal overpressure attenuation trend of different cross-sectional shapes is the same. (3) The gas explosion shock wave propagates radially along the working face section during the working face propagation. The farther away the location is from the upper corner of the tunnel during a gas explosion with different cross-sectional shapes, the closer the cutoff overpressure peak is. The attenuation trend of overpressure with the propagation distance conforms to the power function law. The research results provide an important theoretical direction for the numerical simulation of gas explosions in coal mining faces.

Dynamically tunable ultralong photonic nanojet by a curved surface truncated dielectric microcylinder

As for micro-particles (microspheres or microcylinders) that form Photonic nanojet (PNJ) in near fied,a curved truncated dielectric microcylinder structure (CSTDM) is investigated by finite element method(FEM) which can form ultralong PNJ with the longest effective length:209.49λ. We found that changing parameter h of structure can realize long dynamic range tuning of the effective length of PNJ. The effective length varies quasi-periodically with h; the law of the variation of main indicators of microcylinder are further discussed, such as the effective length,the working distance, peak electric field intensity and full width half height

Story Stability of a Structure- A Literature Review

Column is a slender beam, which carries load. Failure pattern of a column varies with different parameters such as buckling, compression, shear and tension. The initial imperfections in a column increases deflection and reduction in load carrying capacity. To accomplish stability, the key engineering elements such as connection and rigidity governs the effective length and width of the members. The researchers, covering the key engineering elements with different loading patterns, established numerous comprehensive studies. Further, advancement in the research were carried out to determine lateral stiffness, inter-story displacement and deflected beam shape under various loading patterns. The present study focuses on various literatures on effective length and governing factors, which determine the stability of the structure.

Validated Capillary Zone Electrophoretic Determination of Avanafil and Dapoxetine Hydrochloride in their Pure form and Pharmaceutical Preparation

Aims: In this study, a simple, green, and rapid capillary zone electrophoresis (CZE) method coupled with a diode array detector (DAD) was applied for the analysis of avanafil (AVA) and dapoxetine hydrochloride (DAP) as a binary mixture using vardenafil (VAR) as an internal standard (IS) in pure form and pharmaceutical formulation. Methodology: The separation was done using fused silica capillary (58.5 cm total length, 50 cm effective length, and 50 μm internal diameter) and the running background electrolyte (BGE) was 100 mM acetate buffer at pH 3.6. During the separation process, the applied voltage was 30 KV, while the temperature was 25 °C. The sample injection was applied at a pressure of 50 mbar for 10 s, and detection was carried out at 210 nm for DAP and 248 nm for AVA and VAR. Results: Analysis of the tested drugs and the internal standard was carried out in less than 6.5 min, where the migration times were 4.29, 4.90, and 6.02 min for IS, DAP and AVA respectively. The proposed method showed linearity in the concentration range 5-80 and 5-70 μg/mL with correlation coefficients 0.9996 and 0.9999 for AVA and DAP respectively. The limit of detection (LOD) was 0.523 and 0.531 for AVA and DAP respectively, while the limit of quantification (LOQ) was 1.585 and 1.608 in respective order. The Peak purity and identity in the proposed method were validated by DAD. Conclusion: The proposed CZE method was validated according to ICH guidelines and applied successfully for the estimation of AVA and DAP in their combined pharmaceutical preparation.

Alternative Design Procedure for RC-Braced Long Columns Based on New Moment Magnifiers Matrix

Based on modified methods for the results of first-order analysis of RC columns, different codes approximate the second-order effects by using equations focusing on the maximum additional moment through the column height. These equations did not refer to the additional moments between the column and the connected beam, only the effect of the connected beams is taken into consideration by dealing with the effective length of the column, not the total length. Moreover, these equations did not take into account the second-order effect, which is caused by axial force and the inverse moments due to beam restriction for the column ends. This paper presents a new moment magnifiers matrix for the additional moments at the connection between braced columns and the connected beams as a simplified computation that can be used in the design procedure. That is through an equation based on transforming the original long column in second-order analysis to an equivalent isolated column. The equivalent column was represented as an element restricted with rotational spring support at its ends, and it is subjected to lateral distributed loads that have the same influence of the second-order effect on the induced additional moments in the long column. The suggested equivalent column can be used to form the additional bending moment diagram, also to compute the additional deformations as well. Numerous factors were analyzed linearly by using the presented new moment magnifiers matrix and finite element method, and the results proved the efficiency of the proposed model. Although the presented suggested model is based on the isolated analysis of the long column, the effect of the additional moments in the adjacent long column can be considered by presented two suggestions to improve the model. Also, development was proceeded on the model by modifying the flexural rigidity (EI) which is recommended in ACI to appropriate the time of failure. The additional moment values of the developed model were close to the values calculated by the ACI equation.