Design And Simulation Of Static Var Compensator For Voltage Sags Mitigation

Modem power networks are loaded more heavily than ever before to fully utilize the existing transmission facilities while power quality has become an important issue in power system, this is due to the fact that the usage of power electronic equipment and electronic-based loads, which are sensitive to power quality has increased, and thus normal operations in industrial and commercial environments are becoming more vulnerable to power quality problems. One of the problems associated with power quality is voltage sag. Voltage sag is a major power quality problem. It occurs because most voltage sags are due to short circuit on transmission and distribution lines. High technology industries are highly sensitive to voltage sags. A small voltage sag for several cycle, (short duration) is sufficient to interrupt the operation of the facility resulting in costly downtime.Traditional voltage regulating devices such as electromechanical transformer taps and shunt capacitor have been used extensively at the transmission and distribution. However, they are too slow to response to correct voltage sags. This problem can be overcome by replacing them with power-electronics based devices known as Flexible Alternating Currents Transmission System (FACTS). FACTS devices can provide a real-time control of transmission line impedance, voltage magnitude and phase angle. With advancement of high power electronics, fast response of FACTS device is now available. Through proper coordination, they can be utilized to control system power flow, increase power transfer capabilities, improve system transient stability, and damp power system oscillations. Static Var Compensator, SVC is a shunt connected FACTS device having capability of supplying reactive power and thus could protect the system from the potential threats of voltage sags. The objective of this research is to investigate and design SVC for voltage sags mitigation on a small test power system. This work has indicated SVC has the potential to mitigate voltage sag if properly designed and located

Hybrid Plasmonic Waveguide Fed Broadband Nano-antenna for Nanophotonic Applications

In this paper, we propose a novel hybrid plasmonic waveguide fed broadband optical patch nano-antenna for nanophotonic applications. Through full wave electromagnetic simulation, we demonstrated our proposed antenna to radiate and receive signal at all optical communication windows (e.g. $\lambda$ = 850nm, 1310nm & 1550nm) with around 86% bandwidth within the operational domain. Moreover numerical results demonstrate that the proposed nano-antenna has directional radiation pattern with satisfactory gain over all three communication bands. Additionally, we evaluated the antenna performances with two different array arrangements (e.g. one dimensional and square array). The proposed broadband antenna can be used for prominent nanophotonic applications such as optical wireless communication in inter and intra-chip devices, optical sensing and optical energy harvesting etc.Comment: 4 Page, 7 figure

Charged Scalar Pair Production in Strong-Field Photon-Photon Interaction

Following the pioneering work of H. Reiss [1], we provide a covariant calculation of the charged scalar particle pair production. The calculation is facilitated by the use of two-dimensional Bessel functions and light-font coordinates.Comment: 8 page

An Empirical Study on Relationship Marketing and its Effect on Customer Satisfaction

The intense competition among firms in the new global environment has made it inevitable for firms to seek ways to create and maintain quality relationship with customers, and Malaysia banks sector are no exception. However, little is understood from empirical viewpoint about the antecedents of relationship quality specifically. In fact, the actual influence of overall customer satisfaction will be assessed by its indicators (Trust, Communication, Competence, Commitment and Cooperation). In this study, we tend to examine the effects of relationship marketing on customer satisfactions. Based on data collected from 237 customers which consisted of university students of UUM, various data-analytic tools will be used in this study. These tools are used to analyze the data such as test of differences, reliability analysis, factor analysis, and multiple regression analysis. Findings of this study proved that customer can be satisfied by having a close attention to issues of trust, communication, competence, commitment and cooperation

Present Status of Corporate Environmental Accounting (CEA) in Bangladesh: A Study Based on Some Selected Textile Companies

This paper is aimed to analysis the present status of CEA of private sector textile mills of Bangladesh.For the study a sample of 25% of population has been taken. Environment has become a crucial factor in today’s ecological, social and economical set up.Managers who can influence decisions regarding eenvironment express the view that more environmental accounting work is needed, but very little such work is done. A semi-structured questionnaire was prepared and followed direct interview method to know the relevant information. Managers are positive about environmental issues. This paper revealed different problems for not adopting CEA in full swing. Key Words: Environment, Corporate Environmental Accounting(CEA), Corporate Environmental Accounting in Bangladesh

Levobupivacaine versus racemic bupivacaine: a comparative study on spinal anaesthesia in lower limb surgeries

Background: This study aims to compare the anaesthetic potency of intrathecally administered levobupivacaine with racemic bupivacaine in lower limb surgeries.Methods: 60 adult cases ranging in age from 18 to 60 years with ASA Grade I and II, presenting for elective lower limb surgery were randomly allocated into two groups containing 30 cases each. Cases in Group L received 3ml of 0.5% levobupivacaine and those in Group R received 3ml of 0.5% levobupivacaine.Results: Cases in both groups showed similarity and no statistically significant differences were observed. Cardiovascular parameters were stable and similar between both groups.Conclusions: Levobupivacaine and racemic bupivacaine show equally effective potencies for spinal anaesthesia in lower limb surgeries

Effects of delayed metamorphosis on larval survival, metamorphosis, and juvenile performance of four closely related species of tropical sea urchins (genus Echinometra)

We report here, the effects of extended competency on larval survival, metamorphosis, and postlarval juvenile growth of four closely related species of tropical sea urchins, Echinometra sp. A (Ea), E. mathaei (Em), Echinometra sp. C (Ec), and E. oblonga (Eo). Planktotrophic larvae of all four species fed on cultured phytoplankton (Chaetoceros gracilis) attained metamorphic competence within 22–24 days after fertilization. Competent larvae were forced to delay metamorphosis for up to 5 months by preventing them from settling in culture bottles with continuous stirring on a set of 10 rpm rotating rollers and larval survival per monthly intervals was recorded. Larval survival was highest at 24 days, when competence was attained (0 delayed period), and there were no significant differences among the four species. Larvae that had experienced a prolonged delay had reduced survival rate, metamorphosis success, and juvenile survival, but among older larvae, Em had the highest success followed by Ea, Eo, and Ec. Juveniles from larvae of all four species that metamorphosed soon after becoming competent tended to have higher growth rates (test diameter and length of spines) than juveniles from larvae that metamorphosed after a prolonged period of competence with progressively slower growth the longer the prolonged period. Despite the adverse effects of delaying metamorphosis on growth parameters, competent larvae of all four species were able to survive up to 5 months and after metamorphosis grew into 1-month-old juveniles in lab condition. Overall, delayed larvae of Em showed significantly higher larval survival, metamorphosis, and juvenile survival than Ea and Eo, while Ec showed the lowest values in these performances. Em has the most widespread distribution of these species ranging from Africa to Hawaii, while Ec probably has the most restricted distribution. Consequently, differences in distribution may be related to differences in the ability to delay metamorphosis

Growth and survival of the tropical sea urchin, Salmacis sphaeroides fed with different macroalgae in captive rearing condition

An experiment was undertaken to develop appropriate culture techniques for high-valued tropical sea urchin, Salmacis sphaeroides under captive aqua-rearing conditions. Three-month-old juveniles produced through induced breeding, larval rearing and metamorphic induction were stocked with 20 juveniles in each of nine well-aerated glass aquaria (46 x 30 x 30 cm).? Juveniles fed with red alga (Amphiroa fragilissima) were designated as Treatment-1 (T1), brown alga (Sargassum polysystum) as Treatment-2 (T(2)) and sea grass (Enhalus acoroides) as Treatment-3 (T(3)). At the time of stocking, juveniles were under the same age group and batch-reared with a mean length and weight of 9.98 ? 0.56 mm and 0.49 ? 0.11 g, respectively. The juveniles were fed ad libitum, and the seawater in each rearing aquarium was changed at bi-monthly intervals. The culture was carried out for one year during which time the juveniles attained sexual maturity. Growth performances (viz., final weight, weight gain, final length, length gain, specific growth rate and daily growth rate) and survival of adults were significantly higher (P < 0.05) in T(1) than those in T(2) and T(3), respectively. Gonad production, in terms of wet gonad weight and gonad index, also followed the same trend as that for growth. Hence, of the three algal feed evaluated, red alga appeared to be the most suitable food for rearing of S. sphaeroides under captive conditions. The present study is the first demonstration of successful culturing of S. sphaeroides in a static aquarium system, the findings of which could be helpful towards the commercial sea urchin aquaculture