DC-DC Boost Converter with Constant Output Voltage for Grid Connected Photovoltaic Application System

The main purpose of this paper is to introduce an approach to design a DC-DC boost converter with constant output voltage for grid connected photovoltaic application system. The boost converter is designed to step up a fluctuating solar panel voltage to a higher constant DC voltage. It uses voltage feedback to keep the output voltage constant. To do so, a microcontroller is used as the heart of the control system which it tracks and provides pulse-width-modulation signal to control power electronic device in boost converter. The boost converter will be able to direct couple with grid-tied inverter for grid connected photovoltaic system. Simulations were performed to describe the proposed design. Experimental works were carried out with the designed boost converter which has a power rating of 100 W and 24 V output voltage operated in continuous conduction mode at 20 kHz switching frequency. The test results show that the proposed design exhibits a good performance

Ecotourism and environmental conservation in small islands in the east coast of peninsular Malaysia

Many small islands off the east coast of Peninsular Malaysia have become wellknown destinations both to foreign as well as local tourists. However, as tourism authorities, hotels and tour operators increasingly focus on mass tourism and economics, environmental degradation and other issues are affecting tourism negatively. In recent decades, Malaysia has realised the need for protection of environmental attractions and has embarked on many conservation programmes, but most of them are ad hoc and not sustained. This article examines how tourists perceive environmental conservation, willingness to pay, reasons for coming, length of stay, favourite destinations, favourite activities, etc. The results of questionnaire interviews show that small islands off the east coast of Peninsular Malaysia are currently facing serious environmental degradation, with little or no comprehensive conservation, poor enforcement, with no clearcut vision from the authorities as to their future. The study shows that there is a need for a well-planned vision of development for the small islands and stricter control from the authorities. Without better control and implementation of a vision of sustainable development, it is envisaged that these small islands will continue to deteriorate and lose their glamour and attractions gradually. They need to be conserved and stay competitive to survive, given the competition from islands in neighbouring countrie

Regulation of Cardiac Progenitors by Combination of Mesp1 and ETS Transcription Factors

Heart disease remains the leading cause of death worldwide. By understanding the regulating networks during cardiac development we can exploit those networks to manipulate adult cells into cardiac progenitors and provide an alternative for repairing diseased hearts. Mesp1 is considered to have critical roles during cardiac development but the molecular mechanisms need to be further studied. The roles of ETS transcription factors have been primarily limited to hematopoietic differentiation and cancer progression. The ETS transcription factors are known to have proliferating roles and were hypothesized to also be involved in cardiac differentiation and may potentially be used for cell reprogramming. The first part of this study characterizes the expression pattern of Mesp1 protein in early mouse embryo from E6.5 to E9.5 and provides a full expression profile in differentiating embryoid bodies in vitro from the undifferentiated stage to Day10. Our work showed Mesp1 expresses in the posterior region of E6.5 embryo then starts migrating through the primitive streak toward anterior mesoderm and endoderm in E7.5. A Mesp1 linage tracing ES cell line was established, and it allowed us to trace the Mesp1 derived cell population. The lineage tracing system confirmed Mesp1 expressing cells give rise to a major part of the heart and also contributes to some endodermal derived organs such as the pancreas. The direct DNA binding targets of Mesp1 were determined using a Mesp1 specific antibody to perform ChIP of bound DNA that could then be used in next generation sequencing. The resulting sequence data included cardiac genes such as Gata4, Hand2, and Myocd. Endoderm correlated genes Foxa2, Pitx2, and Gata6 were also shown to be Mesp1 targets. The targeted genes were validated as transcriptional targets using an ES cell line with inducible Mesp1 followed by qPCR of target gene transcript levels with and without Mesp1 expression. Secondly, the complete gene expression profiles of over 20 ETS transcription factors were generated. By comparing the ETS factor expression patterns and identifying which showed cardiac gene activation, ETV4 and ETS2 were chosen for further study of their roles in cardiac differentiation. ETS2 was used in combination with Mesp1 to reprogram Normal Human Dermal Fibroblast into cardiac progenitors. The reprogrammed cells were then characterized for gene expression patterns, surface marker, and structural protein presentation. This work provides thorough insights into the roles of Mesp1 and ETS transcription factors during germ layer development and led to the development of a method to reprogram adult cells into cardiac progenitors that could be applied for clinical use in the future

The Effects Of Time Constraints And Proficiency On ESL Essay Writing Performance [LB2372.E5 C454 2007 f rb].

Kajian ini menyelidik kesan kekangan masa dan kecekapan terhadap pencapaian penulisan esei oleh subjek yang merupakan penutur bahasa Inggeris sebagai bahasa kedua. This study investigated the effects of time and proficiency on ESL writing performance. The subjects of the study were two groups of undergraduates, namely proficient and less proficient speakers of English

A Radial Basis Function Neural Network Approach to Two-Color Infrared Missile Detection

Multicolor infrared imaging missile-warning systems require real-time detection techniques that can process the wide instantaneous field of regard of focal plane array sensors with a low false alarm rate. Current technology applies classical statistical methods to this problem and ignores neural network techniques. Thus the research reported here is novel in that it investigates the use of radial basis function (RBF) neural networks to detect sub-pixel missile signatures. An RBF neural network is designed and trained to detect targets in two-color infrared imagery using a recently developed regression tree algorithm. Features are calculated for 3 by 3 pixel sub-images in each color band and concatenated into a vector as input to the network. The RBF network responds with a value of unity to feature vectors representing missiles and with zero to vectors representing background. Images are thresholded prior to application to the trained RBF network to narrow the field of interest of the RBF network and increase missile detection speed. The RBF network-based technique then generates potential target locations and probabilities that the locations correspond to missiles. Results show that the RBF network-based technique operates in near teal-time and detects 100% of the missiles in data that was not used in training Receiver operating characteristic (ROC) curves show that overly high classification thresholds can exceed the RBF network response for a true missile and result in non-detection. However, these ROC curves also show that adaptive control of the classification threshold on the RBF network output can reduce the number of false alarms to zero

Regulation of Cardiac Progenitors by Combination of Mesp1 and ETS Transcription Factors

Heart disease remains the leading cause of death worldwide. By understanding the regulating networks during cardiac development we can exploit those networks to manipulate adult cells into cardiac progenitors and provide an alternative for repairing diseased hearts. Mesp1 is considered to have critical roles during cardiac development but the molecular mechanisms need to be further studied. The roles of ETS transcription factors have been primarily limited to hematopoietic differentiation and cancer progression. The ETS transcription factors are known to have proliferating roles and were hypothesized to also be involved in cardiac differentiation and may potentially be used for cell reprogramming. The first part of this study characterizes the expression pattern of Mesp1 protein in early mouse embryo from E6.5 to E9.5 and provides a full expression profile in differentiating embryoid bodies in vitro from the undifferentiated stage to Day10. Our work showed Mesp1 expresses in the posterior region of E6.5 embryo then starts migrating through the primitive streak toward anterior mesoderm and endoderm in E7.5. A Mesp1 linage tracing ES cell line was established, and it allowed us to trace the Mesp1 derived cell population. The lineage tracing system confirmed Mesp1 expressing cells give rise to a major part of the heart and also contributes to some endodermal derived organs such as the pancreas. The direct DNA binding targets of Mesp1 were determined using a Mesp1 specific antibody to perform ChIP of bound DNA that could then be used in next generation sequencing. The resulting sequence data included cardiac genes such as Gata4, Hand2, and Myocd. Endoderm correlated genes Foxa2, Pitx2, and Gata6 were also shown to be Mesp1 targets. The targeted genes were validated as transcriptional targets using an ES cell line with inducible Mesp1 followed by qPCR of target gene transcript levels with and without Mesp1 expression. Secondly, the complete gene expression profiles of over 20 ETS transcription factors were generated. By comparing the ETS factor expression patterns and identifying which showed cardiac gene activation, ETV4 and ETS2 were chosen for further study of their roles in cardiac differentiation. ETS2 was used in combination with Mesp1 to reprogram Normal Human Dermal Fibroblast into cardiac progenitors. The reprogrammed cells were then characterized for gene expression patterns, surface marker, and structural protein presentation. This work provides thorough insights into the roles of Mesp1 and ETS transcription factors during germ layer development and led to the development of a method to reprogram adult cells into cardiac progenitors that could be applied for clinical use in the future

PIC Control Dc To Dc Converter With Variable Input Voltage And Constant Output Voltage For Photovoltaic Integration

In recent years, attention towards renewable energy such as solar power had increased dramatically due to the awareness of energy crisis. A lot of solar power application systems had been designed. One of the most important solar power applications is to deliver the power produced by solar panel to local utility grid. A constant voltage should be obtained from solar panel in the design of this application system as solar panel is producing a fluctuating voltage level which depends on irradiation and temperature level. Therefore, a DC-DC boost converter is designed to step up the fluctuating solar panel voltage to a higher constant voltage. A microcontroller based DC-DC boost converter is proposed in this design. A PIC16F877 microcontroller is used and performs a voltage-feedback technique where it continuously tracks and measures the DC-DC boost converter output voltage and compares the measured value to a reference voltage. The differential compared value is used to produce a pulse-width-modulation signal. The signal is used to control a switch in the DC-DC boost converter. Simulation results describe the performance of the proposed design. Experimental work was carried out with the converter operating in continuous conduction mode with constant 24 V output voltage, 100 W output power, 20 kHz switching frequency and supplied from solar panel voltage. The experimental results show that the proposed design is able to produce a constant 24 V with efficiency more than 72.9% at 100 W load conditions

A Comparative Study Of The Mean And Median Rainfall Patterns In Northwest Peninsular Malaysia.

Most rainfall studies in Malaysia have used the mean to represent the average rainfall characteristics of the respective regions under study

School Risk Management Practice: A Pilot Study

The purpose of this study was to investigate the relationship between risk management and relevant safety practices of school administrators of 28 primary and secondary schools in the town of Sungai Siput (U), Perak. The factors considered in this study were the independent variables: Risk Identification, Risk Assessment and Risk Control and the personal characteristics of the school administrators: gender, age, service category (educational level), years of service and race. A questionnaire was developed to measure the relevant safety practices of the school administrator and its measurement is known as Risk Management Practice. The study conducted show that 64.28 percent of the school administrators carried out regularly risk management practices in their respective schools. The findings of this study show that Risk Identification, Risk Assessment and Risk Control are significantly related to Risk Management Practice. The personal characteristics of the school administrators do not appear to be significantly related to Risk Management Practice

Slip of fluid molecules on solid surfaces by surface diffusion

The mechanism of fluid slip on a solid surface has been linked to surface diffusion, by which mobile adsorbed fluid molecules perform hops between adsorption sites. However, slip velocity arising from this surface hopping mechanism has been estimated to be significantly lower than that observed experimentally. In this paper, we propose a re-adsorption mechanism for fluid slip. Slip velocity predictions via this mechanism show the improved agreement with experimental measurements