AC voltage regulation of a bidirectional high-frequency link converter using a deadbeat controller

This paper presents a digital controller for AC voltage regulation of a bidirectional high-frequency link (BHFL) inverter using Deadbeat control. The proposed controller consists of inner current loop, outer voltage loop and a feed-forward controller, which imposes a gain scheduling effect according to the reference signal to compensate the steady-state error of the system. The main property of the proposed controller is that the current- and the voltage-loop controllers have the same structure, and use the same sampling period. This simplifies the design and implementation processes. To improve the overall performance of the system, additional disturbance decoupling networks are employed. This takes into account the model discretization effect. Therefore, accurate disturbance decoupling can be achieved, and the system robustness towards load variations is increased. To avoid transformer saturation due to low frequency voltage envelopes, an equalized pulse width modulation (PWM) technique has been introduced. The proposed controller has been realized using the DS1104 digital signal processor (DSP) from dSPACE. Its performances have been tested on a one kVA prototype inverter. Experimental results showed that the proposed controller has very fast dynamic and good steady-state responses even under highly nonlinear loads

Partnership Program Evaluations Shelled Crab Cultivation of a Triangle Pattern in the Post and Marine Fisheries Extension Services in Sub Tangkahan Durian Western Districts Berandan Langkat District of North Sumatra Province

The research was conducted on 27 March to 3 April 2015 in the Village of West Berandan Tangkahan Durian Langkat District of North Sumatra province. The research goal is to investagate increase in business scale and increase revenues before and after the program. Of the various indicators of business as the implementation of business partnership program soft shelled crab cultivation triangle pattern has increased the scale of business of 252.5 kg/person/year, increase the production of 466 kg/person/year, and grow profits for beneficiaries an average of 22.168.500/ person/year. Business partnership program soft shelled crab cultivation triangle pattern has given the average rate of profit to the owners of capital of 0.54% per year or 4.5% per month and this has far exceeded the interest rates on deposits offered by banks, which only reached 7 to 12% per year. Controllers aspect of the program also provides a profit of Rp. 66.97431 million or 58.2% per year and has opened up jobs for two people with a minimum salary of each of Rp. 2,000,000 per month.Of the various aspects that have been evaluated, we conclude that the business partnership program soft shelled crab cultivation triangle pattern appropriate to proceed and the business opportunities that provide benefits to both the beneficiaries, the owners of capital and controllers

PREVALENCE OF ACADEMIC STRESS AMONG MEDICAL AND PHARMACEUTICAL STUDENTS

Prevalence of academic stress among university students has been high across the world. Most studies on such topic have been conducted in limited population, particularly in the students of medical faculty and the publicly secular-based university. The present study was carried out on students at the department of medicine and department of pharmacy, the Universitas Islam Negeri (UIN) Maulana Malik Ibrahim Malang, Indonesia. This study was aimed to describe the level of academic stress prevalence among the students as well as its difference based on demographics, including department, gender, and previous education backgrounds. This study involved 72 students as participants. The results indicated that the prevalence of academic stress reached 61% in the medical students and 48.4% in the pharmaceutical students. Meanwhile, there were no significant differences in the level of prevalence in terms of department, gender, and educational background (P > .05). Academic stress was experienced by the students of various departments, from the differing previous education background, i.e., the Public Senior High School (Sekolah Menengah Atas), Islamic Senior High School (Madrasah Aliyah), and Islamic Boarding School (Pesantren), both the males and females. A high prevalence of academic stress among students at the Islamic university should draw more attention and call for special intervention from the unit of guidance and counseling service.  Article visualizations

Landslides and lineament mapping along the Simpang Pulai to Kg Raja highway, Malaysia

Geological structural features, such as the discontinuities that may be detected on satellite imagery as lineaments, in many cases control landslide occurrences. Lineament may represent the plane of weakness where the strength of the slope material has been reduced, eventually resulting in slope failure. The main objective of this study is to assess the relationship between lineament and landslide occurrences along the Simpang Pulai to Kg Raja highway, Malaysia. Lineament mapping was undertaken utilizing Landsat imagery and landslide distributions were identified based on field mapping and historical records. Lineament density maps of length, number and intersections were generated and compared with landslide distributions. The lineaments were also visually compared with the landslide occurrences. The results showed that there is an association between the lineaments and landslide distribution. Thus, lineament mapping is essential for the early stages of planning to prevent hazard potential from landslides

Analysis of Transmission Lightning Arrester Locations Using Tflash

Tropical countries with extensive lightning activity, such as Malaysia, encounter numerous problems on their electrical transmission and distribution systems. Many overhead lines trip because of back flashover of lightning and shielding failures of the grounding system. To overcome the problem and improve transmission line performance, a detailed lightning study is required to analyse the corresponding lines and determine the best location for transmission line arrester (TLA) installation. We used TFlash to analyse a TLA installation on a 132-kV SSWW-BBST overhead transmission line system located in Selangor, Malaysia. Based on the results, the installation of the TLA at the optimum quantity and at appropriate towers have reduced the number of lines that trip

Control of an Underactuated Double-Pendulum Overhead Crane using Improved Model Reference Command Shaping: Design, Simulation and Experiment

This paper presents a new control scheme based on model reference command shaping (MRCS) for an overhead crane, with double-pendulum mechanism effects. The approach has an advantage in achieving an accurate trolley positioning, with low hook and payload oscillations, under various desired trolley positions and parameter uncertainties, without the requirement for measurement or estimation of system parameters. These are challenging in practice. The previously developed MRCS algorithm is improved in order to reduce its design complexity, as well as to ensure that it can be augmented with a feedback controller so that a concurrent controller tuning can be realised. The combined MRCS and feedback controller is used to achieve both, precise trolley positioning, and low hook and payload oscillations. To evaluate the effectiveness and the robustness of the approach, simulations and experiments using a nonlinear model and a laboratory double-pendulum crane are carried out. Under various desired positions and parameter uncertainties that involve varying the cable lengths (payload hoisting) and the payload mass variations, the superiority of the proposed approach is confirmed by achieving higher hook and payload oscillation reductions when compared with a recently proposed feedback controller. In addition, the desired trolley positions are achieved with smoother responses

Analysis of transmission lightning arrester locations using Tflash

Tropical countries with extensive lightning activity, such as Malaysia, encounter numerous problems on their electrical transmission and distribution systems. Many overhead lines trip because of back flashover of lightning and shielding failures of the grounding system. To overcome the problem and improve transmission line performance, a detailed lightning study is required to analyse the corresponding lines and determine the best location for transmission line arrester (TLA) installation. We used TFlash to analyse a TLA installation on a 132-kV SSWW-BBST overhead transmission line system located in Selangor, Malaysia. Based on the results, the installation of the TLA at the optimum quantity and at appropriate towers have reduced the number of lines that trip

A three competing species model for wastewater treatment: case study on Taman Timur oxidation pond, Johor Bahru

Oxidation pond techniques have practically proved to be effective for wastewater treatment process (WWTP) because of their low construction and operating cost. Cumbersome sampling is required to monitor the dynamics of the WWTP which also involves enormous costly work. Deterministic model accommodating the correlation between the amount of phototrophic bacteria in a product called mPHO (bioproduct used to improve water quality) and pollutant (bacteria E.coli and Coliform) existing in oxidation pond is developed to facilitate the analysis of this process. This study presents ordinary differential equation model for an oxidation pond to investigate the effect of mPHO on the degradation of pollutant. The model consists of a system of ordinary differential equations (ODE) with coupled reaction equations for the pollutant and phototrophic bacteria. The parameters of the model is estimated using the real data collected from an aerobic oxidation pond located in Taman Timor, Johor, Malaysia to illustrate a real life application of this model. The simulation results provide a better understanding of the ecological system in the oxidation pond

Transmission-Lightning-Arrester : A Location Determination Using Tflash

The high density of lightning occurrence in Malaysiahas caused problems to transmission and distribution electricalenergy. Normally, transmission overhead lines trip due to BackFlashover (BF) of lightning and shielding failures of earth wire.Therefore, a detailed lightning study is required to analyse thecorresponding lines and to determine the exact location ofTransmission Lightning Arrester (TLA). In this paper, a simulationof lightning study using TFlash software associated with theinstallation of (TLA) at 132 kV SSWW-BBST overhead linessystem located in Selangor, Malaysia is presented. By using theTFlash software the location of TLA has been determine