Micro-perforated panel (MPP) absorber is increasingly gaining popularity as an alternative sound absorber in buildings compared to the well-known synthetic porous materials. A single MPP has a typical feature of a Helmholtz resonator with a high amplitude of absorption but a narrow absorption frequency bandwidth. To improve the bandwidth, a single MPP can be cascaded with another single MPP to form a double-layer MPP. This paper proposes the introduction of inhomogeneous perforation in the double-layer MPP system (DL-iMPP) to enhance the absorption bandwidth of a double-layer MPP. Mathematical models are proposed using the equivalent electrical circuit model and are validated with experiments with good agreement. It is revealed that the DL-iMPP produces a wider half-absorption bandwidth compared to the conventional homogeneous double-layer MPP. The absorption bandwidth to higher frequencies can be effectively controlled by reducing the air cavity between the iMPPs and to the lower frequencies by increasing the back cavity depth at the second layer.
This review article concentrates the light about aetiology and treatment of the periimplantitis.
This article discusses how women have significant abilities to cope with the difficulties of war times. They are not the weak and vulnerable victims who are thought to be. On the contrary, they have the power to control over many-sided fronts, like participating in the battlefield as nurses or activists for peace, or even fighters, as well as through the tasks and responsibilities assigned to them to protect and support their families during wartime. The researcher will examine the impact of war upon women. Like men, women suffer during wartime. They are being injured, tortured and killed. Yet, they are able to give examples of love and courage even in the difficult times of war. Hana is one of those women who lived during wartimes,
... Show MoreOne of the main environmental problems which affect extensively the areas in the world is soil salinity. Traditional data collection methods are neither enough for considering this important environmental problem nor accurate for soil studies. Remote sensing data could overcome most of these problems. Although satellite images are commonly used for these studies, however there are still needs to find the best calibration between the data and real situations in each specified area. Landsat satellite (TM & ETM+) images have been analyzed to study soil pollution (Exacerbation of salinity in the soil without the use of abandoned agricultural for a long time) at west of Baghdad city of Iraqi country for the years 1990, 2001 & 2007. All of the th
... Show MoreIn this study, pebble bed as an absorber and storage material was placed in a south facing, flat plate air-type solar collector at fixed tilt angle of (45°). The effect of this material and differ- ent parameters on collector efficiency has been investigated experimentally and
theoretically. Two operation modes were employed to study the performance of the solar air heater. An inte- grated mode of continuous operation of the system during the period of (11:00 am – 3:00 pm) and non-integrated mode in which the system stored the solar energy through the day then used the stored energy during the period of (3:00 pm – 8:00 pm). The results of parametric study in case of continuous operating showed that the maximum average temperatur
Theauthor addressed politeness discourse in “Surat Ghafir”. Quran texts include many rhetorical utterances which are considered pragmatic mechanismsconcerned with finding polite discourse. examining these texts allow to determine the effectiveness degree in the discourse, and to find the effect level that leads to interaction between the speaker and the listener. Graduation is considered an effect and a mechanism of discourse escalation.
The author reached a common definition of the graduation effectiveness term, due to its importance in finding polite discourse that is constructed by lingual manifestations some of which are escalation and graduation. Escalation is a mechanism to show the level of discourse graduation, it is a mea
The key objective of the study is to understand the best processes that are currently used in managing talent in Australian higher education (AHE) and design a quantitative measurement of talent management processes (TMPs) for the higher education (HE) sector.
The three qualitative multi-method studies that are commonly used in empirical studies, namely, brainstorming, focus group discussions and semi-structured individual interviews were considered. Twenty
This study aims to know how and what is the media processing presented by the television talk shows for the religious extremism topics in terms of topics, hosted personalities, and ways to address this global phenomenon.
The study is based on descriptive research, and the researcher used the analytical-survey method, analyzing the episodes of (Awkar Al Dhalam) T.V Show which was presented on Al-Iraqiya News Channel, and (Islam Hur) T.V Show which was presented on Al-Hurra in 2019 with 25 episodes from each Show, The sample and research community was chosen with the intent to cover the research problem and its
The study reached several conclusions, including:
- The various dialogs in the episo
A mathematical method with a new algorithm with the aid of Matlab language is proposed to compute the linear equivalence (or the recursion length) of the pseudo-random key-stream periodic sequences using Fourier transform. The proposed method enables the computation of the linear equivalence to determine the degree of the complexity of any binary or real periodic sequences produced from linear or nonlinear key-stream generators. The procedure can be used with comparatively greater computational ease and efficiency. The results of this algorithm are compared with Berlekamp-Massey (BM) method and good results are obtained where the results of the Fourier transform are more accurate than those of (BM) method for computing the linear equivalenc
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