Design of high efficiency turbomachinery blades

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Computational Modeling of Airborne Noise Demonstrated Via Benchmarks, Supersonic Jet, and Railway Barrier

In the last several years, there has been a growing demand for mobility to cope with the increasing population. All kinds of transportation have responded to this demand by expanding their networks and introducing new ideas. Rail transportation introduced the idea of high-speed trains and air transportation introduced the idea of high-speed civil transport (HSCT). In this expanding world, the noise legislation is felt to inhibit these plans. Accurate computational methods for noise prediction are in great demand. In the current research, two computational methods are developed to predict noise propagation in air. The first method is based on the finite differencing technique on generalized curvilinear coordinates and it is used to solve linear and nonlinear Euler equations. The dispersion-relation-preserving scheme is adopted for spatial discretization. For temporal integration, either the dispersion-relation-preserving scheme or the low-dispersion-and-dissipation Runge-Kutta scheme is used. Both characteristic and asymptotic nonreflective boundary conditions are studied. Ghost points are employed to satisfy the wall boundary condition. A number of benchmark problems are solved to validate different components of the present method. These include initial pulse in free space, initial pulse reflected from a flat or curved wall, time-periodic train of waves reflected from a flat wall, and oscillatory sink flow. The computed results are compared with the analytical solutions and good agreements are obtained. Using the method developed, the noise of Mach 2.1, perfectly expanded, two-dimensional supersonic jet is computed. The Reynolds-averaged Navier-Stokes equations are solved for the jet mean flow. The instability waves, which are used to excite the jet, are obtained from the solution of the compressible Rayleigh equation. Then, the linearized Euler equations are solved for jet noise. To improve computational efficiency, flow-adapted grid and a multi-block time integration technique are developed. The computations are compared with the experimental results for both the mean flow and the jet noise. Good agreement is obtained. The method proved to be fast and efficient. The second computational method is based on the boundary element technique. The Helmholtz equation is solved for the sound field around a railway noise barrier. Linear elements are used to discretize the barrier surface. Frequency-dependent grids are employed for efficiency. The train noise is represented by a point source located above the nearest rail. The source parameters are estimated from a typical field measurement of train noise spectrum. Both elevated and ground-level train decks are considered. The performance of the noise barrier at low and high frequencies is investigated. Moreover, A-weighted sound pressure levels are calculated. The computed results are successfully compared with field measurements

Back to Thailand: Post-Graduated Patani Students’ Work Orientation

Kajian ini membahas orientasi kerja mahasiswa Islam asal Patani, Thailand, setelah lulus perkuliahan dari UIN Sunan Gunung Djati Bandung. Dengan fokus penelitian pada alumni asal Patani lulusan tahun 2012-2015, kajian ini bertujuan untuk mengetahui variasi pekerjaan mereka dan mengungkapkan faktor-faktor yang mempengaruhi orientasi kerja mereka. Penelitian ini menggunakan teori pilihan rasional Coleman. Metode penelitian yang digunakan adalah kualitatif-deskriptif. Pengambilan sampel sumber data dilakukan dengan teknik purporsive sampling dan snowball sampling. Analisis data dilakukan dengan triangulasi (gabungan) dan bersifat interaktif dan kualitatif yang lebih menekankan pada makna daripada generalisasi. Hasil penelitian ini  menunjukkan bahwa dalam hal orientasi kerja mahasiswa Patani di UIN SGD Bandung pasca-kelulusan sebagian besar memiliki keinginan mendapat pekerjaan sesuai dengan latar belakang keilmuannya masing-masing walaupun ada sebagian mahasiswa yang memilih pekerjaan di luar dari latar belakang keilmuannya. Variasi pekerjaan yang didapatkan oleh para alumni UIN SGD Bandung asal Patani lulusan dari tahun 2012 sampai tahun 2015 adalah guru, wirausaha dan petani. Orientasi kerja mereka dipengaruhi oleh faktor penghambat, yakni sedikitnya lapangan perkerjaan yang tersedia dikarenakan sulitnya sistem rekruitmen pekerjaan di Thailand, dan faktor pendorong yakni motivasi, ekonomi, dan sumber daya manusia

Evaluation of Orifice Flow Meter Accuracy under Pulsation Conditions

Orifice meter is a flow measuring device which is widely used in various industrial applications. Although the device gives accurate measurement during steady flow, measurement errors related to square root and sampling errors are unavoidable if pulsations exist. This research investigatesand improves the performance of an orifice plate flow meter under pulsation effects. A simple model for the pulsating flow through an orifice meter is presented. Square root error (SRE) is estimated. Sampling errors (SE) are reduced by proper selection of the averaging tim

Dynamic thermal model for proton-exchange membrane fuel cell

In this paper, a mathematical model is developed to simulate the transient phenomena in a polymer electrolyte membrane fuel cell (PEMFC) system. Large transient changes are expected for practical application such as transportation vehicles due to acceleration and deceleration. Simple models are usually unable to capture these transient dynamics. For control purposes, a fuel cell model must include the dynamics of flow and pressure in the anode and cathode channels and mass/heat transfer transients. The proposed model can predict the transient response of cell voltage, temperature of the cell, hydrogen/oxygen out flow rates and cathode and anode channel pressures under sudden change in load current. It is implemented in SIMULINK environment. The model is tested by simulating a transportation-size fuel cell with 85 kW maximum power output. Results for maximum power and multi-step input current that simulate start up-shut down cycle are shown. The predicted power, pressure and temperature are matching the published data for the fuel cell. The model will be very useful for the optimal design and real-time control of PEM fuel cell systems in practical automotive or stationary applications

Factors Influencing the Intention of Recipient to Pay Back Education Loan in State Foundation

This paper explores the factors that influence the intention to pay back the education loan among students in a state foundation. Education loan is the primary source for the student in order to pursue their studies. The government has introduced many forms of financial assistance such as scholarship, grants and education loan. However, the loan recipients have faced difficulties in repaying the loan, which will affect the provider and future recipients. This is because, the loan provider will not be able to sponsor future students if they are not able to collect the loan from the loan recipients. This paper identifies attitude, parental influence, media awareness and perception of loan agreement towards the intention to pay back the education loan. Theory of Planned Behavior (TPB) is suggested to be the underpinning theory of this study. Findings of the study can assist the state foundations on setting strategies to collect payment from the loan recipients