Coordinated Control of Energy Storage in Networked Microgrids under Unpredicted Load Demands

In this paper a nonlinear control design for power balancing in networked microgrids using energy storage devices is presented. Each microgrid is considered to be interfaced to the distribution feeder though a solid-state transformer (SST). The internal duty cycle based controllers of each SST ensures stable regulation of power commands during normal operation. But problem arises when a sudden change in load or generation occurs in any microgrid in a completely unpredicted way in between the time instants at which the SSTs receive their power setpoints. In such a case, the energy storage unit in that microgrid must produce or absorb the deficit power. The challenge lies in designing a suitable regulator for this purpose owing to the nonlinearity of the battery model and its coupling with the nonlinear SST dynamics. We design an input-output linearization based controller, and show that it guarantees closed-loop stability via a cascade connection with the SST model. The design is also extended to the case when multiple SSTs must coordinate their individual storage controllers to assist a given SST whose storage capacity is insufficient to serve the unpredicted load. The design is verified using the IEEE 34-bus distribution system with nine SST-driven microgrids.Comment: 8 pages, 10 figure

EFFECT OF SEEDLING AGE ON GROWTH & YIELD OF BINA DHAN 6

An experiment was conducted at Rangpur, Bangladesh during November 2015 to July 2016 to study the effect of seedling ages on the growth & yield of BINA dhan 6. Seedlings of different ages, viz 25, 35, 45, 55 & 65 days old were transplanted on the same day. Result revealed that plant height, number of leaves hill-1, total dry matter (TDM) hill-1, leaf area index (LAI), number of total tillers, number fertile tillers hill-1, number of grains panicle-1, 1000 grain weight, grain & straw yield was affected significantly due to different ages of seedlings. The result also showed that number of tillers hill-1, number of leaves hill-1, & leaf area index increased for all seedling ages up to 75 days after transplanting (DAT) and decreased gradually thereafter. The highest number of tillers hill-1, leaves hill-1 and leaf area index, the highest amount of stem, leaf, root and total dry matter and CGR were obtained from 35days old seedlings at all sampling dates. The highest number of effective tillers hill-1, panicle length, number of grains panicle-1, grain yield (6.96 t ha-1) and straw yield (7.75 t ha-1) were also achieved by 35 days old seedlings at harvest. Thirty-five days old seedlings were found to be superior to other ages of seedlings in term of growth and grain yield

Tissue Heart Valve Replacement at BSMMU- Initial Experience with Two Cases

Research on prosthesis to replace diseased heart valves began almost simultaneously with mechanical valves which aredurable but with inherent thromboembolic complication requiring life-long anticoagulant therapy and tissue valves whichare more prone to structural failure but free from thromboembolic complication. Tissue valves are more useful in females ofreproductive age desiring a child, male patients older than 60 years of age and female patients over 55 years of age, patientshaving chronic liver disease, history of stroke, bleeding disorder and in presence of infective endocarditis. Gluteraldehydefixation at low pressure with removal of maximal amount of phospholipid have increased the durability of tissue valves inrecent years. Considering the better quality of life with tissue valve the trend is shifting towards using it more frequentlyaround the world. Recently two heart valve replacement operations using bovine perimount pericardial valve were done inthe department of cardiac surgery, BSMMU, one in aortic position another in mitral position, both in females of reproductiveage desiring children.The operations were technically demanding but the outcomes were uneventful. Tissue heart valvereplacement is a safe procedure and can be useful in female of child bearing age desiring children.Key Words: Tissue heart valve replacement; Aortic valve; Mitral valve; Bioprosthetic heart valves; Bovine perimountpericardial valve.DOI: 10.3329/bsmmuj.v3i1.5511BSMMU J 2010; 3(1): 27-3

Antibacterial activity of ethanol extract of Sargassum polycystum against Streptococcus mutans and Lactobacillus casei: in vitro

Introduction: Sargassum polycystum (brown seaweeds) has been recognized as a potential source of natural antibacterial and antimicrobial compounds. It has been used in many applications and products as they possess interesting biological activities that give benefit to the dental and medical area. Aims: The objectives of this study were to determine the growth curve of Streptococcus mutans and Lactobacillus casei, and also to determine minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) value of Sargassum polycystum extract against Streptococcus mutans and Lactobacillus casei. Materials and methods: The growth of both bacteria were studied by growth curve analysis. Besides that, the antibacterial activity of Sargassum polycystum ethanol extracts against two oral cariogenic bacteria were examined using broth dilution method. The bioactivity of the seaweed extract was studied by finding the MIC and MBC value. Results: The time taken for the Streptococcus mutans and Lactobacillus casei to achieve exponential phase during growth is 4 and 5 hours respectively. MIC values of ethanol extracts of Sargassum polycystum in different concentration against Streptococcus mutans and Lactobacillus casei were unreliable because the presence of fungus (white-precipitate) at all 96-well plates including the positive and negative control. As there was no MIC value, partial inhibition was determined by calculating the optical density. Therefore, MBC analysis was unable to carry out because the MIC values were unreliable. Conclusion: The ethanol extract of Sargassum polycystum used in this study show partial bacterial inhibition against pathogens used. Therefore, the same study by using different type of solvent are recommended to be carried out in the future

Neighborhood analysis for metropolitan areas

Call number: LD2668 .R4 1968 H

Bioremediation of oil spills in soil

Oil spillage can cause a critical environmental impact on soil. Thus, many technologies have been developed for treating land contaminated by petroleum products. In this project, crude oil contaminated soil will be treated by bioremediation using oil-utilizing bacterial consortium. The bacterial consortium will be isolated from the crude-oil contaminated soil samples, and the best hydrocarbons degrading organisms will be selected for developing the bioremediation process. Water sludge with known composition will be used as nutrient source for the degradation process. The highest growth and hydrocarbon-degradation rate bacteria with the optimum process parameters will be used for the design of the bioremediation process

New robust bounded control for uncertain nonlinear system using mixed backstepping and lyapunov redesign

This paper presents a new robust bounded control law to stabilize uncertain nonlinear system with time varying disturbance. The design idea comes from the advantages of backstepping with Lyapunov redesign, which avoid the needs of fast switching of discontinuous control law offered by its counterpart - a variable structure control. We reduce the conservatism in the design process where the control law can be flexibly chosen from Lyapunov function, hence avoiding the use of convex optimization via linear matrix inequality (LMI) in which the feasibility is rather hard to be obtained. For this work, we design two type control algorithms namely normal control and bounded control. As such, our contribution is the introduction of a new bounded control law that can avoid excessive control energy, high magnitude chattering in control signal and small oscillation in stabilized states. Computation of total energy for both control laws confirmed that the bounded control law can stabilize with less enegry consumption. We also use Euler's approximation to compute average power for both control laws. The robustness of the proposed controller is achieved via saturation-like function in Lyapunov redesign, and hence guaranting asymptotic stability of the closed-loop system

Robust controller design for position tracking of nonlinear system using back stepping-GSA approach

Electro-hydraulic actuator (EHA) system is highly non-linear system with uncertain dynamics in which the mathematical representation of the system cannot sufficiently represent the practical system. Nonlinearities of the system come from either the system itself or external disturbance signals. These dynamic characteristics are the reasons that cause the controller design for the system to be quite challenging. In this paper, back-stepping controller design for tracking purpose of this system is presented based on Lyapunov stability condition. Gravitational Search Algorithm (GSA) technique is then used to optimize the control parameters in order to achieve a predefined system performance. The performance is evaluated based on the tracking output and the tracking error between reference input and the system output. The results show that the system's output follow the reference input given but the tracking performance is influenced by the condition of the system and number of agents and iteration in the algorithm

Studies on Chromene based 2, 6-disubstituted-Thiazolo [3,2-B] [1,2,4] Triazole derivatives: Synthesis and Biological Evaluation

In this study, a series of novel chromene based 2,6-disubstituted-thiazolo[3,2-b] [1,2,4] triazole derivatives (7a-g) were synthesized by condensing 5-substituted-1,2,4-traizole-thione (6a-g) using poly phosphoric acid through one pot reaction. The structure of new compounds was supported by 1H NMR, 13C NMR and MS data. The synthesized compounds were evaluated using writhing assays for analgesic and carrageenan-induced rat paw edema method for anti-inflammatory activities respectively. Some of the newly synthesized compounds 7c, 7f and 7g showed very good anti-inflammatory activity with 90.83%, 85.81% and 88.40% protection respectively along with low GI toxicity as compared to standard drug ibuprofen while compounds 7a, 7b, 7d and 7f showed highest analgesic activity with 52.54%, 54.02%, 56.76% and 52.45% protection among them compound 7d showed better protection than standard drug ibuprofen. Keywords: thiazolo-triazoles, Chromene, Anti-inflammatory, Analgesi

Confidence in Teaching Mathematics Among Malaysia Pre-Service Teachers

This study focuses on the confidence level of mathematics education students in teaching school mathematics. Respondents were 165 final year students from four Malaysian universities. It was found that the respondents showed a strong foundation in mathematics upon entrance to the university. In spite of their strong background in school mathematics, their mean cumulative grade point average (CGPA) during their final year in the university was rather low. The mean confidence level in teaching mathematics was moderate. The respondents showed a relatively high confidence in the pedagogical aspect of teaching. Respondents reported great confidence in teaching Form One to Form Three, however the confidence level declined as the level taught became higher. The confidence level varied with the topics, which was lowest for the topic on probability. Confidence level in solving problems spontaneously during class was low and teaching mathematics in English was the lowest. The results showed that a significant but low positive correlation exists between (i) level of confidence and CGPA and (ii) level of confidence and confidence in implementing specific aspects of teaching. A significant negative correlation was established between (i) level of confidence and CGPA; and (ii) level of confidence and university level mathematics