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Summary: The use of lignocellulosic fibers, pineapple leaf fiber (PALF) and sisal as reinforcements in thermoplastic and thermosetting resins for developing low cost and lightweight composites is an emerging field of research in polymer science and technology. Although, these biofibers have several advantages, such as low densities, low cost, nonabrasive nature, high filling level possible, low energy consumption, high specific properties, biodegradability, etc., over synthetic fibers, the absorption of moisture by untreated biofibers, poor wettability, and insufficient adhesion between the polymer matrix and fiber deteriorate the mechanical properties of composites made up of these biofibers. Therefore, the modification of these fibers is a key area of research at present to obtain optimum fiber‐matrix properties. This review article is concerned with the structure, composition and properties of PALF and sisal, the chemical modifications of these fibers and PALF/sisal‐reinforced thermosets, thermoplastics, rubber, cement, hybrids and biocomposites.Scanning electron micrograph of tensile fractured surface of alkali treated sisal fiber (magnification ×500).magnified imageScanning electron micrograph of tensile fractured surface of alkali treated sisal fiber (magnification ×500).

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In the present research, the effect of variations of the electron beam voltage on the output power is studied. In order to develop the study, this problem was investigated at different frequencies, which are the products of nonlinear behavior of the traveling wave tube (TWT) in response to the input frequency. Moreover, for a more realistic understanding, the tubes were considered with two linear and nonlinear responses to the input frequency. The TWT output power was calculated in linear and nonlinear modes, at different frequencies using the numerical solution of the mathematical equations of the Lagrangian model. Then, the output power in terms of distance and beam voltage in different frequencies was plotted and compared. The results revealed that the effects of variations of voltage on the output power were more proper in a singlemode TWT in comparison with a multimode one.