New torque and flux controllers for direct torque control of induction machines

The new torque and flux controllers with constant switching frequency and low torque and flux ripples for direct torque control induction machine drives are presented. The core of these proposed controllers is based on the comparison between the compensated error signals with high frequency triangular waveforms, thus does not require complex calculation to generate the inverter switching signals. The controllers are therefore can be implemented using analog and/or digital circuits. Modeling and simulation of the new controllers are presented and the results show that the torque and flux ripples are reduced significan

Travelling-wave similarity solutions for an unsteady shear-stress-driven dry patch in a flowing film

We investigate unsteady flow of a thin film of Newtonian fluid around a symmetric slender dry patch moving with constant velocity on an inclined planar substrate, the flow being driven by a prescribed constant shear stress at the free surface of the film (which would be of uniform thickness in the absence of the dry patch). We obtain a novel unsteady travelling-wave similarity solution which predicts that the dry patch has a parabolic shape and that the film thickness increases monotonically away from the dry patch

Unsteady gravity-driven slender rivulets of a power-law fluid

Unsteady gravity-driven flow of a thin slender rivulet of a non-Newtonian power-law fluid on a plane inclined at an angle α to the horizontal is considered. Unsteady similarity solutions are obtained for both converging sessile rivulets (when 0 0 with t > 0, where x denotes a coordinate measured down the plane and t denotes time. Numerical and asymptotic methods are used to show that for each value of the power-law index N there are two physically realisable solutions, with cross-sectional profiles that are 'single-humped' and 'double-humped', respectively. Each solution predicts that at any time t the rivulet widens or narrows according to |x | (2N+1)/2(N+1) and thickens or thins according to |x | N/(N+1) as it flows down the plane; moreover, at any station x, it widens or narrows according to |t | −N/2(N+1) and thickens or thins according to |t | −N/(N+1). The length of a truncated rivulet of fixed volume is found to behave according to |t | N/(2N+1)

To develop an efficient variable speed compressor motor system

This research presents a proposed new method of improving the energy efficiency of a Variable Speed Drive (VSD) for induction motors. The principles of VSD are reviewed with emphasis on the efficiency and power losses associated with the operation of the variable speed compressor motor drive, particularly at low speed operation.The efficiency of induction motor when operated at rated speed and load torque is high. However at low load operation, application of the induction motor at rated flux will cause the iron losses to increase excessively, hence its efficiency will reduce dramatically. To improve this efficiency, it is essential to obtain the flux level that minimizes the total motor losses. This technique is known as an efficiency or energy optimization control method. In practice, typical of the compressor load does not require high dynamic response, therefore improvement of the efficiency optimization control that is proposed in this research is based on scalar control model.In this research, development of a new neural network controller for efficiency optimization control is proposed. The controller is designed to generate both voltage and frequency reference signals imultaneously. To achieve a robust controller from variation of motor parameters, a real-time or on-line learning algorithm based on a second order optimization Levenberg-Marquardt is employed. The simulation of the proposed controller for variable speed compressor is presented. The results obtained clearly show that the efficiency at low speed is significant increased. Besides that the speed of the motor can be maintained. Furthermore, the controller is also robust to the motor parameters variation. The simulation results are also verified by experiment

A simulation study of a parametric mixture model of three different distributions to analyze heterogeneous survival data

In this paper a simulation study of a parametric mixture model of three different distributions is considered to model heterogeneous survival data.Some properties of the proposed parametric mixture of Exponential, Gamma and Weibull are investigated.The Expectation Maximization Algorithm (EM) is implemented to estimate the maximum likelihood estimators of three different postulated parametric mixture model parameters.The simulations are performed by simulating data sampled from a population of three component parametric mixture of three different distributions, and the simulations are repeated 10, 30, 50, 100 and 500 times to investigate the consistency and stability of the EM scheme.The EM Algorithm scheme developed is able to estimate the parameters of the mixture which are very close to the parameters of the postulated model.The repetitions of the simulation give parameters closer and closer to the postulated models, as the number of repetitions increases, with relatively small standard errors

Travelling-wave similarity solution for unsteady flow around a dry patch driven by gravity and constant surface shear stress

In this paper we use the lubrication approximation to analyse three-dimensional unsteady flow of a thin film of Newtonian fluid around a symmetric slender moving dry patch on an inclined planar substrate. The flow being driven by gravity and a prescribed constant shear stress at the free surface. We obtain a novel unsteady travelling-wave similarity solution for the dry patch of uniform thickness, in which the dry patch travels at constant speed. This solution predicts that the dry patch has a parabolic shape which may be concave up or concave down the substrate. In all cases investigated numerically the film thickness is found to increase monotonically away from the contact line

PEMANFAATAN LIMBAH KULIT KOPI MENJADI BIOETANOL DENGAN PROSES FERMENTASI MENGGUNAKAN BAKTERI ZYMOMONAS MOBILIS

Limbah kulit kopi selama ini belum dimanfaatkan karena yang digunakan hanya biji kopi. Pada proses pengolahan kopi akan menghasilkan 35% limbah kulit kopi yang merupakan sumber bahan organic berkadar selulosa cukup tinggi dan tersedia melimpah di Indonesia, sehingga limbah kulit kopi dapat dimanfaatkan menjadi bioetanol. Sebagai energy alternative pengganti BBM, bioetanol memiliki kelebihan dibanding dengan BBM, diantaranya memiliki kandungan oksigen yang lebih tinggi (35%) sehingga terbakar lebih sempurna, bernilai oktan lebih tinggi (118) dan lebih ramah lingkungan karena mengandung emisi gas CO lebih rendah 19–25 % (Indartono Y., 2005). Proses pembuatan bioetanol dilakukan dengan menghidrolisis kulit kopi menjadi glukosa menggunakan katalis H2SO4 (10, 20, 30 % v/v) dan HCl (10, 20, 30 % v/v). Selanjutnya glukosa difermentasi menjadi bioetanol menggunakan bakteri Zymomonas Mobilis. Dengan variabel waktu Fermentasi (2, 3, 4, 5, 6, 7, 8 hari), dan konsentrasi starter Zymomonas mobilis ( 9, 10, 11 % v/v). Penelitian menunjukkan bahwa kulit kopi dapat digunakan sebagai bahan baku alternative pembuatan bioetanol dengan proses hidrolisis dan fermentasi, hasil terbaik diperoleh pada konsentrasi starter 11 %, waktu fermentasi 7 hari menghasilkan bioetanol sebanyak 51,02 % dengan kadar 38,68 %

Evaluation of Land Suitability for Banggai Sweet Potato (Discorea alata) in Peling Tengah District, Banggai Islands

The sweet potato plant is a type of local food, tubers that are very popular in the Peling Tengah community, Banggai Islands Regency, and are an alternative type of plant for the main food ingredient after rice. For this reason, knowledge of land evaluation is needed so that optimal and sustainable agricultural production can be achieved. This research was conducted in October 2021 - January 2022, in Peling Tengah District, Banggai Islands Regency. The research method used is survey, analysis, and land suitability classification based on the following criteria: requirements for plant growth in accordance with the characteristics/quality of the land. The results showed that the actual land suitability class was S3 (marginal), with  limiting  factors  including: rainfall, temperature, slope, drainage, texture, soil CEC, pH, N-Total, P2O5, K2O, erosion hazard. base saturation, and C Organi

Tahap Penglibatan Peserta dalam Projek Hala Cara Baru Pembangunan Kampung dan Luar Bandar

Projek Hala Cara Baru pembangunan kampung dan luar bandar (HCB) telah dilancarkan untuk pelaksanaan pada tahun 1984. Sungguhpun tujuh tahun telah berlalu,kemajuan pelaksanaannya didapati kurang memuaskan. Tahap penglibatan peserta yang rendah telah dikaitkan dengan masalah pelaksanaan projek tersebut. Tujuan umum kajian ialah untuk menentukan faktor-faktor berhubung dengan penglibatan peserta dalam projek Hala Cara Baru pembangunan kampung dan luar bandar. Secara khusus, kajian ini bertujuan mengetahui: (i) tahap penglibatan peserta dalam perencanaan projek HCB, (ii) penerimaan responden terhadap pelaksanaan aktiviti projek HCB, (iii) tanggapan peserta terhadap matlamat dan strategi projek HCB, (iv) hubungan antara tahap pelaksanaan projek dengan tahap penglibatan peserta, dan (v) hubungan antara penglibatan dengan beberapa angkubah bebas terpilih kajian