Recently, environmental noise has arisen from various sources, such as those from exhaust mufflers of combustion engines found in cars, trucks, or power generators, which produce significant noise during their operation. Controlling the radiated noise from these mufflers is a major factor in improving acoustic comfort and minimizing the impact on the surrounding communities. Numerous research has been presented for this reason by modification of the internal structure of the exhaust muffler. The main objective of this work is to reduce the noise level emitted from exhaust mufflers. This can be achieved by adjusting structure parameters to attenuate the surrounding environment's radiated noise. Analysis of pressure-wave propagation has been done by building 3D models using COMSOL Multiphysics software. Different entities were conducted to investigate the influence of muffler shells and plate thicknesses on acoustic performance through the frequency domain to obtain better attenuation. SPL over a frequency band is presented, describing how the sound intensity varies at different frequencies within a given bandwidth. The results showed that increasing the muffler shell thickness improved the TL; this particularly causes a double value at a range above 1.2 kHz, where there are two distinct peaks at 1.3 kHz and 2.8 kHz. Additionally, it was found that increasing the muffler plate thickness reduces the TL whole range and moves the curve peak to higher frequencies. This is because the pressure pulses that stimulate the shell plates would exert a more distinct influence on plates characterized by a reduced thickness, and the muffler structure thickness is correlated with its increased stiffness, resulting in an elevation of the frequency for this eigenmode
The purpose of present study is to evaluate the effect of co-administration of curcumin (CUR) at various doses on the pharmacokinetic (PK) profile of tacrolimus (TAC), a CYP 3A4 substrate in healthy male rabbits. Healthy male rabbits (n=18) were employed in an in vivo, parallel-randomized study. Three groups of rabbits were selected and separated: The rabbits in the first group (control group) received 1 mg/kg TAC orally. Blood samples (1.5-2 mL) were drawn from rabbits' ear marginal veins at the following time frames: 15.0, 30.0, 45.0, 60.0, 90.0, 120.0, 150.0, 180.0 and 300 minutes after TAC administration post dosing and analyzed by using a TAC chemiluminescent enzyme immunoassay (CLIA) detection kit. In the second and third gro
... Show MoreNowadays, the use of recycled waste construction materials instead of aggregates is becoming popular in construction owing to its environmental benefits. This paper presents an experimental and analytical campaign to study the behavior of axially loaded columns constructed from recycled aggregates. The latter was used instead of natural aggregates, and they were collected from the waste of previous concrete constructions. Different concrete mixtures made from varying amounts of recycled aggregates ranged from 0 to 50% of the total coarse aggregate were conducted to achieve 28 MPa. The effect of steel fibers is another investigated variable with volumes ranged from 0 to 2% concerning concrete’s mixture. The experimental
... Show MorePiroxicam is a non-steroidal anti-inflammatory drug (NSAID) used in the treatment of musculo-skeletal and joint disorders. The problem with this drug is its poor solubility in water and hence poor bioavailability after oral administration. In order to improve its solubility and dissolution behavior, hydrophilic additives such as starch, lactose, superdisintegrants including crospovidone (C.P), cross carmellose sodium (CCS), and sodium starch glycolate (SSG) were physically dry mixed with the drug by simple trituration. The improvement in the solubility in 0.1 N HCl was obtained as the amount of starch or lactose increased in the physical mixture, while for superdisintegrants, they further improve the solubility when they are present in s
... Show MoreThe life insurance companies need a sound system to use it in selecting Insurable risks so they can avoid or reduce possible losses that may be insured to a minimum levels , But the application within IRAQI INSURANCE COMPANY reflects that it still depends on a traditional ways in the procedures used to select that risks .
This research represents an attempt to put acceptable suggestions about developing a system for selecting insurable risks which used now by iraqi insurance company by recognizing the risks of life insurance , determining kinds of risks which can difined as normal and upnormal risks , rectification of the
... Show MoreCdSe quantum dots possess a tuning energy gap which can control gap values according to the size of the quantum dots, this is made the material able to absorb the wavelengths within visible light. A simple model is provided for the absorption coefficient, optical properties, and optical constants for CdSe quantum dots from the size 10nm to 1nm with the range of visible region between (300-730) nm at room temperature. It turns out that there is an absorption threshold for each wavelength, CdSe quantum dots begin to absorb the visible spectrum of 1.4 nm at room temperature for a wavelength of 300 nm. It has been noted that; when the wavelength is increased, the absorption threshold also increases. This applies to the optical propertie
... Show MoreSamples prepared by using carbon black as a filler material and phenolic resin as a binder. The samples were pressed in a (3) cm diameter cylindrical die to (250)MPa and treated thermally within temperature range of (600-1000)oC for two and three hours. Physical properties tests were performed, like density, porosity, and X-ray tests. Moreover vicker microhardness and electric resistivity tests were done. From the results, it can be concluded that density was increased while porosity was decreased gradually with increasing temperature and treating time. In microhardness test, it found that more temperature and treating time cause more hardness. Finally the resistivity was decreased in steps with temperature and treating time. It can be c
... Show MoreIn this work, 332 Al alloy was prepared and reinforced with (0.5% and 1%) nano-Al2O3 particles. The prepared unreinforced and reinforced 332 Al alloy with nano-Al2O3 were solution heat treated (T6) at 510 ̊C and aged at 225 ̊C with different times (1, 3, and 5 h). Hardness test was performed on all the prepared alloys. All prepared alloys were dry slided under different applied loads (5, 10, 15, and 20 N) against steel counterface surface using pin on disk apparatus. The results showed that refinement effect was observed after addition of nano-Al2O3 particles and a change in silicon morphology after performing the solution heat treatment. The results also showed that har
... Show MoreEffect of the thermal annealing at 400oC for 2 hours and Argon laser radiation for half hour on the optical properties of AgAlS2 thin films, prepared on glass slides by chemical spray pyrolysis at 360oC with (0.18±0.05) μm thickness .The optical characteristics of the prepared thin films have been investigated by UV/Vis spectrophotometer in the wavelength range (300 – 1100)nm .The films have a direct allow electronic transition with optical energy (Eg) values decreased from (2.25) eV for untreated thin films to (2.10) eV for the annealed films and to (2.00) eV for the radiated films. The maximum value of the refractive index (n) for all thin films are given about (2.6). Also the extinction coefficient (K) and the real and imaginary d
... Show MoreBeta-irradiation effects on the microstructure of LDPE samples have been investigated
using Positron Annihilation Lifetime Technique (PALT). These effects on the orthopositronium
(o-Ps) Lifetime t3, the free positron annihilation lifetime 2 t , the free-volume
hole size (Vh) and the free volume fraction (fh) were measured as functions of Beta
irradiation - dose up to a total dose of 30.28 kGy.
The results show that the values of t3, Vh and fh increase gradually with increasing Beta
dose up to a total dose of 1.289 kGy, and reach a maximum increment of 17.4%, 32.8% and
5.86%, respectively, while t2 reachs maximum increment of 211.9% at a total dose of 1.59
kGy. Above these doses, the values show nonlinear changes u
Stone Matrix Asphalt (SMA) is a gap-graded asphalt concrete hot blend combining high-quality coarse aggregate with a rich asphalt cement content. This blend generates a stable paving combination with a powerful stone-on-stone skeleton that offers excellent durability and routing strength. The objectives of this work are: Studying the durability performance of stone matrix asphalt (SMA) mixture in terms of moisture damage and temperature susceptibility and Discovering the effect of stabilized additive (Fly Ash ) on the performance of stone matrix asphalt (SMA) mixture. In this investigation, the durability of stone matrix asphalt concrete was assessed in terms of temperature susceptibility, resistance to moisture damage, and sensitivity t
... Show More