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"Sejak pertama kali ditemukannya fenomena pengurangan hambatan gesek oleh B.A Toms tahun 1948 yang terjadi pada larutan polimer, banyak studi yang dilakukan oleh para peneliti untuk meningkatkan efisiensi dalam penggunaan energi. Pengurangan hambatan atau Drag Reduction (DR) biasa terjadi pada aliran turbulen dan aliran transisi.Efek Drag Reduction dengan penambahan aditif berupa polymer dapat menimbulkan peredaman turbulensi yang disebabkan oleh karakteristik dan gerakan fluida itu sendiri. Kerugian tekanan dalam pipa segi empat diukur dengan variasi konsentrai guar gum dalam air untuk mengetahui efek bertambahnya drag reduction sebagai tujuan dari penelitian ini.Pengukuran tekanan dilakukan dalam pipa segi empat berukuran 3 x 3 mm dan 4 x 4 mm pada bilangan Reynolds 500 - 50000 dengan konsentrasi guar gum 250 dan 500 ppm. Diketahui bahwa larutan guar gum mengurangi faktor gesekan pada aliran turbulen.

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Since drag reduction phenomenon in polymer additives was found by Toms, B.A., in 1948, much of the work increasing efficiently to economizing energy by investigators. The drag reduction occurs in turbulent flow and transition.The drag reduction effect in polymer additives due to wall turbulens caused by the characterstic of moving the fluid owners. The pressure loss in rectangular duct was measured for various concentration of guar gum in water to study the effect of the additives on drag reduction as the objective of this paper.The pressure measurement were carried out in rectangular ducts are of approximately 3 x 3 mm and 4 x 4 mm within a range of Re from about 500 to 50000 to various concentration of guar gum in water 250 and 500 ppm. It is found that guar gum reduced the friction factor in turbulent flow."

"Mobile VIMAX system is espexted to be an base for wireless ubiquitous products all over the world. This high mobilety communication systems need efficient channel estimation to cope high requency selectivity and time variation channel effect...."

"Kehadiran sistem UWB telah menawarkan potensi besar untuk desain komunikasi nirkabel jarak pendek berkecepatan tinggi dengan kapasitas transfer data yang sangat besar. Hal ini dapat dicapai dengan cara melakukan eksploitasi spasial dan perbedaan multipath melalui penggunaan sistem MIMO-OFDM dan teknik simbol yang tepat. Sistem tersebut mengkombinasikan antena MIMO dan teknik OFDM yang handal dalam mentransmisikan data berkecepatan tinggi, meski pada lingkungan multipath sekalipun. Juga dapat mengatasi distorsi delay spread dan unflat fading akibat kanal multipath, sehingga dapat dicapai efisiensi spektrum dan peningkatan throughput.Pada tesis ini dilakukan penelitian tentang MIMO OFDM berbasis SVD. Pemodelan kanalnya dilakukan dengan cara menerapkan konsep dekomposisi kanal frekuensi selektif fading ke bentuk kanal paralel flat fading dalam domain frekuensi. Model kanal domain frekuensi digunakan untuk menyajikan performansi kecepatan data yang berbeda. Kemudian mengembangkan konsep decouple kanal frekuensi selektif ke dalam domain spasial dengan cara mendekomposisi kanal MIMO flat fading ke dalam kanal domain spasial orthogonal menggunakan pendekatan berbasis SVD. Selanjutnya mengkom- binasikan decouple spasial berbasis SVD dengan decouple domain frekuensi berbasis FFT untuk mendapatkan model kanal paralel UWB MIMO OFDM. Akhirnya diharapkan bahwa analisa teoritis ini dapat diaplikasikan dalam sistem komunikasi nirkabel jarak pendek berkecepatan tinggi dengan menerapkan suatu cara untuk memilih kecepatan data yang berbasis pada kondisi kanal.The emerging UWB system offers a great potential for the design of high speed short range wireless communications which fully support high data streaming capacity. This can be achieved by exploiting both spatial and multipath diversity via the use of MIMO OFDM system and proper coding techniques. The systems combine MIMO antenna and OFDM technique which reliable in high data rate transmission even in multipath environment. It also overcomes delay spread distortion and unflat fading caused by multipath channels, thus high spectral efficiency and high throughput improvement can be achieved.

This thesis studies MIMO OFDM techniques base on singular value decomposition. The channel modeling is done by applying the concept of decomposition of frequency selective fading channel into parallel flat fading channel in the frequency domain. This frequency domain channel model is used to present the performance for different data rates. Then develops the concept of decoupling of frequency selective channel into spatial domain by presenting SVD based approach to decouple flat fading MIMO channels to orthogonal spatial channels. At least, the SVD based spatial domain decoupling is combined with FFT based frequency domain decoupling to obtain UWB MIMO OFDM parallel channel model. It is finally expected this theoretical analysis can be implemented in high speed short range wireless communication systems by applying a rate selection technique base on channel condit."

"This book focuses on the two-phase flow problems relevant in the automotive and power generation sectors. It includes fundamental studies on liquid-gas two-phase interactions, nucleate and film boiling, condensation, cavitation, suspension flows as well as the latest developments in the field of two-phase problems pertaining to power generation systems. It also discusses the latest analytical, numerical and experimental techniques for investigating the role of two-phase flows in performance analysis of devices like combustion engines, gas turbines, nuclear reactors and fuel cells. The wide scope of applications of this topic makes this book of interest to researchers and professionals alike."