Stabilization of Compressor Surge Using Gain-Scheduled Controller

Gain scheduling is a control method that is used in nonlinear systems to optimize their controlled performance and robustness over a wide range of operating conditions. It is one of the most commonly used controller design approaches for nonlinear systems. In this control technique, the controller consists of a collection of linear controllers, each of which provides satisfactory closed-loop stability and performance for a small operating region, and combined they guarantee the stability of the system along the entire operating range. The operating region of the system is determined by a scheduling signal, also known as the scheduling variable, which may be either exogenous or endogenous with respect to the plan. A good design of the gain-scheduled controller requires a suitable selection of the scheduling variables to properly reflect the dynamics of the system. In this thesis, we apply the gain scheduling control method to the control of compression systems with active magnetic bearings (AMBs). First, a gain-scheduled controller is designed and tested for the rotor levitation control of the AMB system. The levitation controller is designed to guarantee robust rotor levitation over a wide range of rotating speeds. We show through numerical simulation that the rotor vibration is contained in the presence of uncertainties introduced by speed dependent gyroscopic forces. Next, we implement the gain scheduling control method to the active stabilization of compressor surge in a compression system using the AMBs as actuators. Recently, Yoon et al. [1] showed that AMBs can be used to stabilize the surge instability in a compression system. In this thesis, we demonstrate that gain scheduling control can effectively extend the stable operating region of the compression system beyond the limits presented in [1]. For the stabilization of surge, a gain-scheduled controller was obtained by combining six linear controllers that together they cover the full operating range of the compression system. We were able to demonstrate through numerical simulation that the designed surge controller is effective in suppressing the instability down to a throttle valve opening of 12%, and in the presence of random flow disturbance and actuator saturation. An observer-based technique was implemented to achieve a bumpless and smooth transfer when switching between the linear controllers

Perancangan dan Realisasi Antena Biquad untuk WiMAX pada frekuensi 3.3-3.4 GHz

ABSTRAKSI: Seiring dengan perkembangan jaman, teknologi pun kian berkembang. Banyak teknologi – teknologi baru bermunculan pada masa sekarang ini. Setiap Negara pun seakan berlomba – lomba untuk mengembangkan teknologi baru tersebut. Salah satunya adalah WiMAX. Meski tidak terlalu baru di luar sana, tapi bagi Negara Indonesia teknologi tersebut masih baru. Untuk itu dibutuhkan beberapa perangkat pendukung untuk mendukung berkembangnya WiMAX di Indonesia.Pada masa sekarang ini, masih kurang sekali perangkat – perangkat pendukung berkembangnya WiMAX di Indonesia. Salah satu perangkat itu adalah antena user terminal (CPE). Untuk antena user terminal (CPE), sangat dibutuhkan suatu antena yang memiliki gain tepat, arah pancar yang sesuai, akurat, lebih efisien dan bentuk yang kompak. Antena yang dibuat pada penelitian ini berbentuk persegi belah ketupat yang disusun 2 buah dan disebut antena Biquad. Antena yang dibuat dapat bekerja pada frekuensi 3.3 – 3.4 GHz dengan batasan VSWR ≤ 1.3 untuk mendukung aplikasi WiMAX IEEE 802.16e. Pola radiasi antena tersebut adalah omnidirectional sehingga antena dapat memancarkan gelombang ke segala arah dengan polarisasi linier.Dari hasil pengukuran, didapatkan nilai VSWR sebesar 1.027 pada frekuensi kerjanya, yaitu 3.35 GHz. Sedangkan untuk frekuensi 3.3 GHz dan 3.4 GHz masing-masing memiliki nilai VSWR sebesar 1.253 dan 1.208. Gain yang diperoleh dari pengukuran, yaitu sebesar 7.119 dBi. Antena yang telah direalisasikan memiliki pola pancar bidirectional dan berpolarisasi elips mendekati linear.Kata Kunci : Antena Biquad, WimaxABSTRACT: Through the rolling time, technology is just followed the evolution stage. There are so many new found technologies had been discover lately. Every country is just competed each other to show who is the best one. One of the new found technologies is Worldwide Interoperability for Mobile Access (WiMAX). Even it is not truly new out there, but in Indonesia it is still count as the new one. By that reason, in Indonesia still needs some supported equipment to develop WiMAX in Indonesia itself.In this time, supported equipment to develop WiMAX in Indonesia is still in the minor amount of goods. CPE (Customer Premises Equipment) antenna is one of the supported equipments. This antenna is located in the consumer side. Because it is in the consumer side, we have to consider the size of the antenna. So, we need the antenna that has compact design, exact gain, and has the right polarization. By that specification, I would like to make that kind antenna. The antenna has square form and arrayed by 2 antennas. It is called Biquad Antenna. The Biquad Antenna will work at the range frequencies of 3.3-3.4 GHz and has VSWR ≤ 1.3 to support the WiMAX IEEE 802.16e application. It has bidirectional radiation pattern and linear polarization.From the measurements, the antenna has 1.027 in VSWR at its center frequency, 3.35 GHz, and has 1.253 in VSWR at the frequency of 3.3 GHz and 1.208 in VSWR at the frequency of 3.4 GHz. It gain is 7.119 dBi. It has omnidirectional radiation pattern and elliptic polarization which is closely to linear polarization.Keyword: Biquad Antenna, WiMA

Hybrid Approach to Steganography System Based on Quantum Encryption and Chaos Algorithms

This paper proposes a hybrid system for secretly embedding images into the dithered multilevelimage. Confident hybridizations between steganography and quantum encryptions are either rare inliterature or suffer a poor effectiveness in secure communication. This paper scrambles and divides thesecret image into groups to be embedded in the blocks of the cover image using three chaos algorithms.These are Lorenz map, Henon map, and Logistic map algorithms. The encryption of embedded imagesconducted using the quantum one-time pad. Results showed that the proposed hybrid system succeeded inembedding and combining images with quantum cryptography algorithms

Distortions to Agricultural Incentives in Bangladesh

Distorted incentives, agricultural and trade policy reforms, national agricultural development, Agricultural and Food Policy, International Relations/Trade, F13, F14, Q17, Q18,

The Dream of Return in Ghassan Kanafani’s Returning to Haifa

Home is the place where we are supposed to feel the most secure, comfortable and safe. However, such are the vagaries of human existence; that it is this sanctuary which comes under threat from various forces. Gassan Kanafani, in his fiction, has repeatedly highlighted this problem as it was (and continues to be) faced by several Palestinians in the face of Israeli extremist atrocities. Even while highlighting the problem, Kanafani staunchly advocates the need to hold on to one’s home, even in the face of extreme adversity. Returning to Haifa, on which this paper specifically focuses, is a powerful case in point. This paper attempts to analyse how through the trials of one displaced family, Kanafani has tried to show the need to fight for one’s homeland; because once it is given up, even if we do return later to try to pick up the threads, the narrative often changes beyond our control by then

Bulk-mediated diffusion on a planar surface: full solution

We consider the effective surface motion of a particle that intermittently unbinds from a planar surface and performs bulk excursions. Based on a random walk approach we derive the diffusion equations for surface and bulk diffusion including the surface-bulk coupling. From these exact dynamic equations we analytically obtain the propagator of the effective surface motion. This approach allows us to deduce a superdiffusive, Cauchy-type behavior on the surface, together with exact cutoffs limiting the Cauchy form. Moreover we study the long-time dynamics for the surface motion.Comment: 12 pages, 1 figur

Enhancement of the feeding value of some agro-industrial by-products for laying hens after their solid state fermentation with Trichoderma viride

This study with some agro-byproducts was carried out to provide information on the use of fermentation by-products; brewer's dried grains (BDG), rice bran (RB), palm kernel meal (PKM) and corn bran (CB). Changes in the nutrient compositions of some selected agro industrial by-products on biodegradation with Trichoderma viride and their feeding value as an energy source for layers were investigated. The protein in BDG, RB, PKM and CB increased by 87, 68, 32 and 61%, respectively, when they were fermented with the fungi for 14 days. At the same time, the fiber in the by-products decreased by 35.00, 40.00, 36.50 and 37.50%, respectively with a corresponding increase of 49.00, 37.00, 9.00 and 5.50% in the level of soluble sugars. The energy in the biodegraded by-products increased by 6.30, 5.00, 9.00 and 18.50%, respectively. In a feeding trial with layers, 50% of the maize in a standard commercial diet was replaced with biodegraded BDG, RB and PKM. Birds on the BDG and RB diets had significantly (

Étude de la qualité des eaux d’une retenue située sous climat aride : cas du barrage Hassan II (Province de Midelt, Maroc)

Les ressources hydriques dont dispose le Maroc sont limitées. Elles sont, par ailleurs, soumises à des variations cycliques extrêmes traduites par la succession des cycles de sécheresse aigue. Celle-ci est devenue un phénomène très fréquent au Maroc, qui contribue à la dégradation des zones humides nationales. Pour subvenir aux besoins en eau de plus en plus croissants, le Maroc s'est doté d'une importante infrastructure de grands barrages. Toutefois, la faisabilité et la gestion de ces ouvrages aménagés se trouvent confrontées à deux problèmes: l'envasement et l'eutrophisation. Ces deux phénomènes sont principalement favorisés par la nature du climat et les caractéristiques intrinsèques des bassins versants. Le bassin versant de la Moulouya est parmi les bassins  hydrographiques les plus importants au Maroc, il abrite jusqu'à nos jours cinq grands barrages, dont le barrage Hassan II qui fut mise en eau en 2005.Ce barrage constitue l’une des plus grandes retenues marocaines avec une capacité de stockage maximale de 400 millions de mètres cubes. Il contrôle un bassin versant de 3 300 km2. Il a comme vocations principales la production d’eau potable, l’irrigation, et la protection des zones aval contre les inondations. Or la prolifération des activités anthropiques, en amont, associées aux caractéristiques du climat de la région d’implantation du barrage, pourront être à l’origine de la dégradation de la qualité de ce plan d’eau. Notre travail étalé sur la période allant de septembre 2011 à août 2012 avait pour objectifs d'étudier la qualité des eaux du réservoir Hassan II et d’en déterminer l’état trophique. Il en ressort qu’il s’agit d’un lac oligotrophe avec une qualité de l’eau allant du bonne à excellente.Mots-clés : barrage Hassan II, Maroc, climat, eau, qualité, eutrophisation

Effective Leadership, Self-Efficacy, Emotional Intelligence, Information Acquisition and Utilization of Managers in Packaging Companies in Nigeria

This study investigated self-efficacy, emotional intelligence, information acquisition and utilization of determinants of effective leadership of managers in packaging companies in Nigeria. The survey method was used. Total enumeration technique and questionnaire was used for data gathering from a population size of 450 managers in the surveyed companies out of which 400 responded giving a response rate of 88.8 percent. Simple correlation and hierarchical regression analyses were used for data analysis. The study established that there were significant correlations among self-efficacy, emotional intelligence, information acquisition, information utilization and effective leadership of the respondents. It was further established that self-efficacy, emotional intelligence, information acquisition and utilization were significant determinants of effective leadership of managers in the packaging companies in Nigeria. It was therefore recommended that the board of management in the studied companies should endeavour to encourage their managers to acquire and utilize information to enhance their effective leadership. They should give self-efficacy and emotional intelligence training to their managers in order for them to be effective leaders. KEYWORDS: Self-efficacy, Emotional intelligence, Information acquisition, Information utilization, Managers, Nigeria