32 research outputs found
Hybrid Material and Device Platforms for Reconfigurable Integrated Nanophotonics
No full textPresented on November 27, 2018 at 12:00 p.m.-1:00 p.m. in the Marcus Nanotechnology Building, Room 1117-1118, Georgia Tech.Ali Adibi is the director of Bio and Environmental Sensing Technologies (BEST) and a professor and Joseph M. Pettit chair in the School of Electrical and Computer Engineering, Georgia Institute of Technology. His research group has pioneered several structures in the field of integrated nanophotonics for both information processing and sensing. He is the author of more than 150 journal papers and 400 conference papers. He is the editor-in-chief of the Journal of Nanophotonics, and the nanophotonic program track chair of the Photonics West meeting. He is the recipient of several awards including Presidential Early Career Award for Scientists and Engineers, Packard Fellowship, NSF CAREER Award, and the SPIE Technology Achievement Award. He is also a fellow of OSA, SPIE, and AAAS.Runtime: 51:02 minutesThe development of ultra-compact integrated nanophotonic structures for communications, sensing, and signal processing has been of great interest lately. Recent progress in the development of miniaturized high-Q microresonators has resulted in orders of magnitude reduction in the size of functional integrated photonic structures. The possibility of low-power tuning of the resonance features in these structures has made the formation of reconfigurable photonic structures possible. Among existing CMOS-compatible substrates, silicon (Si) and silicon nitride (SiN) have been used the most. Despite impressive progress in Si-based and SiN-based integrated photonics, neither substrate alone can be used for practical applications. Si (despite its good reconfigurability) suffers from strong nonlinear effects (especially at high light intensities) and relatively large free-carrier loss while SiN (with one order of magnitude lower loss and lower nonlinearity compared to Si) is very hard to tune. Thus, a reliable material system that combines ultra-loss-loss and high power handling with efficient and fast reconfigurability is of high demand in integrated nanophotonics. In this talk, the recent achievements in the development and optimization of hybrid multi-layer CMOS-compatible material systems (e.g., SiN/Si, multi-layer Si/SiO2, etc.) to address all the practical requirements of ultra-fast and ultra-compact integrated photonic structures will be discussed. Using these hybrid material systems, a series of ultra-compact and high-performance reconfigurable photonic devices and subsystems that are formed by using high Q resonators will be demonstrated. The use of these devices and subsystems for realization of densely-integrated reconfigurable photonic chips for signal processing and sensing applications will be discussed
Secondary Frequency Control of Microgrids: An Online Reinforcement Learning Approach
No full textIn this article, we present a reinforcement learning-based scheme for secondary frequency control of lossy inverter-based microgrids. Compared with the existing methods in the literature, we relax the common restrictions on the system, i.e., being lossless, and the transmission lines and loads to have known constant impedances. The proposed secondary frequency control scheme does not require a priori information about system parameters and can achieve frequency synchronization within an ultimate bound in the presence of dominantly resistive and/or inductive line and load impedances, model parameter uncertainties, and time varying loads and disturbances. First, using Lyapunov theory, a feedback control is formulated based on the unknown dynamics of the microgrid. Next, a performance function is defined based on cumulative costs toward achieving convergence to the nominal frequency. The performance function is approximated by a critic neural network in real-time. An actor network is then simultaneously learning a parameterized approximation of the nonlinear dynamics and optimizing the approximated performance function obtained from the critic network. Furthermore, using the Lyapunov approach, the uniformly ultimate boundedness of the closed-loop frequency error dynamics and the networks' weight estimation errors are shown. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Mathematical Physic
Tuning of narrow-bandwidth photonic crystal devices etched in InGaAsP planar waveguides by Liquid Crystal infiltration
No full textPhotonic crystal (PC) devices in the InP/InGaAsP/InP planar waveguide system exhibiting narrow bandwidth features were investigated for use as ultrasmall and tunable building blocks for photonic integrated circuits at the telecom wavelength of 1.55 ?m. The H1 cavity, consisting of a single PC-hole left unetched, represents the smallest possible cavity in a dielectric material. The tuning of this cavity by temperature was investigated under the conditions as etched and after the holes were infiltrated with liquid crystal (LC), thus separating the contributions of host semiconductor and LC-infill. The shift and tuning by temperature of the MiniStopBand (MSB) in a W3 waveguide, consisting of three rows of holes left unetched, was observed after infiltrating the PC with LC. The samples finally underwent a third processing step of local wet underetching the PC to leave an InGaAsP membrane structure, which was optically assessed through the ridge waveguides that remained after the under etch and by SNOM-probing.Kavli Institute of NanoscienceApplied Science
A value chain analysis of Malaysia's seaweed industry
No full textA global shortfall in protein supply from capture fisheries has motivated the Malaysian government to revise its aquaculture strategy, focusing on three commodities: seaweed, fish and marine shrimp. However, the performance of the Malaysian aquaculture sector, particularly seaweed production, is poorly documented. This is the first empirical study to undertake a value chain analysis (VCA) of the Malaysian seaweed sector using stakeholder perceptions and secondary data that encompass members of seaweed farming cooperatives (the Semporna Area Farmers’ Association and the governments’ flagship Seaweed Cluster Project). Fieldwork was conducted between April and June 2015 among seaweed stakeholders involved in the value chain using a mixed methods approach—in-depth interviews with key informants, focus group discussions, household surveys, personal observation and secondary data. Qualitative and quantitative data were collected from both upstream (seaweed farming, marketing structure and the Malaysian Good Aquaculture Practices [MyGAP] certification programme) and downstream (seaweed processing) activities involving farmers, intermediaries/middlemen (buyers), processors and officials. Kappaphycus spp. was sold in two forms: (1) dried seaweed to be used as raw materials in carrageenan processing (approximately 90% of total harvest) and (2) fresh seaweed to be used as a source of seedlings (approximately 10% of total harvest). The value chain ended with the carrageenan form, which is exported to international markets. The price of dried seaweed varied according to a combination of seaweed quality, the strength of farmer’s relationships with intermediaries and processors and in response to demand from the carrageenan industry. The prices obtained by Malaysian farmers for dried seaweed and carrageenan remained low, US 4.43 per kg, respectively, despite efforts by the government to enhance the value chain by imposing seaweed standards (via MyGAP) for farm management, dried seaweed and semi-refined carrageenan. The VCA was a useful tool to identify and map the market, with the results providing a better understanding of the seaweed sector, which could be helpful in supporting further aquaculture development in Malaysia
Is a cooperative approach to seaweed farming effectual? An analysis of the seaweed cluster project (SCP), Malaysia
No full textSeaweed (Kappaphycus spp.) farming has been practised in Malaysia since the late 1970s following government policy incentives (training and farming inputs). However, numerous governance, economic, environmental, technological and sociocultural challenges have limited the industry from achieving its full potential. The Seaweed Cluster Project (SCP) was introduced in 2012 to address some of these challenges. We sought to evaluate the effectiveness of the SCP in delivering its central objectives of increasing seaweed production, optimising the farming area, improving seaweed quality and farming efficiency, raising farmers’ income, and reducing the environmental impact of seaweed farming. Community and industry perceptions of the SCP were obtained from seven communities using a mixed-methods approach based on face-to-face semi-structured interviews, focus group discussions, household surveys, observation and secondary data. Views on the SCP outcomes were generally negative, including low take-up rates by indigenous people, poor stakeholder participation in decision-making, limited acceptance of new technologies, economic vulnerability, a complex marketing system, and low social cohesion of seaweed farming communities. Positive perceptions included recognition that the SCP confers high social status upon a community, reduces operating costs, and facilitates the production of certified seaweed. The SCP’s problems are linked to poor multi-level governance, weak market mechanisms and unintegrated community development. The study concludes with five recommendations to improve the SCP: promote the participation of indigenous people; legalise existing migrant farmers; strengthen local seaweed cooperative organisations; provide entrepreneurship skills to farmers; and fully integrate stakeholders into decision-making
A Reinforcement Learning Approach for Frequency Control of Inverted-Based Microgrids
No full textIn this paper, we present a reinforcement learning control scheme for optimal frequency synchronization in a lossy inverter-based microgrid. Compared to the existing methods in the literature, we relax the restrictions on the system, i.e. being a lossless microgrid, and the transmission lines and loads to have constant impedances. The proposed control scheme does not require a priori information about system parameters and can achieve frequency synchronization in the presence of dominantly resistive and/or inductive line and load impedances, model parameter uncertainties, time varying loads and disturbances. First, using Lyapunov theory a feedback control is formulated based on the unknown dynamics of the microgrid. Next, a performance function is defined based on cumulative rewards towards achieving convergence to the nominal frequency. The performance function is approximated by a critic neural network in real-time. An actor network is then simultaneously learning a parameterized approximation of the nonlinear dynamics and optimizing the approximated performance function obtained from the critic network. The performance of our control scheme is validated via simulation on a lossy microgrid case study in the presence of disturbances.Mathematical Physic
AN OVERVIEW OF BUDU PRODUCTION IN KELANTAN FROM HALAL AND POLICY ASPECTS
No full textBudu or fish sauce is a traditional food of the East Coast communities in Peninsular Malaysia that is produced through a fermentation process between 6 to 12 months in the covered containers known as unprocessed budu. Meanwhile, the processed budu is prepared by grounding coarsely unprocessed budu before mixing with tamarind paste, palm sugar, sugar, monosodium glutamate (MSG), food colouring, and then boiled. Once the mixture is filtered, processed budu is cooled, bottled and marketed all over Malaysia. Most of the manufacturers (23) are located in Kelantan and Terengganu. However, based on the recent data, only one brand of budu is halal-certified as compared to other Malaysian fermented fish products, i.e., belacan (243), pekasam (14), and cencaluk (13). The study offers some important insights into the issues that arise in budu production from the halal and policy aspects that may hinder the manufacturers from applying halal certification. The use of qualitative studies is a well-established approach in this study. Five broad themes emerged from the analysis, the low quality of raw materials (anchovies) and lack of awareness and knowledge base in food safety and hygiene practices among the manufacturers and workers are identified as the main factors contributing to scare-mongering against halal certification. In addition, we found shortage of raw materials (anchovies), lack of incentive and specification standards for the quality of budu were the bottleneck of halal application among the budu entrepreneur. Therefore, more outstanding efforts are needed to ensure the involvement and cooperation from the government agencies and regulators and budu manufacturers to help them penetrate the international market. Indeed, a desire is needed to boost the exportation of budu globally following the market demand and opportunities.  
Exploring, harnessing and conserving marine genetic resources towards a sustainable seaweed aquaculture
No full textSeaweed cultivation is the fastest‐growing aquaculture sector, with a demonstrable potential to drive development in some of the poorest coastal populations worldwide. However, sustainable exploitation, fair access and equitable benefits from marine genetic resources, such as seaweeds have yet to be fully realised. Patchy fundamental knowledge on the genetic diversity and metabolic potential of algae limits their exploitation; scant practical skills and low investment in breeding restricts germplasm availability and the Nagoya protocol has only partially remediated insufficient governance. Further developments and the addressing of knowledge gaps in relation to biosecurity, breeders’ rights and conservation of genetic resources are needed for progress.CMMG, JaB, RCS, PEL, IC, EJCC, VM, GW, VLM, FEM, JuB were supported by the United Kingdom Research and Innovation–Global Challenges Research Fund (UKRI‐ GCRF) ‘GlobalSeaweedSTAR' Programme (Grant No. BB/P027806/1), which also supported RVD through the research fund GSS/RF/015. RVD would like to thank the Department of Science and Technology (DOST), Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (PCAARRD) under the program, Establishment of Seaweed Research and Development Center (SeaRDeC) to Support the Seaweed Industry in BARMM, Project 2: Molecular characterization, selection and production of high quality eucheumatoid cultivars in the Bangsamoro Autonomous Region in Muslim Mindanao. We also thank the interdisciplinary discussions and comments from the GlobalSeaweedSTAR team, specifically Jee Suyo, Ivy Matoju, Azam Asri, Adibi M. Nor and Louise Shaxson
The Presence of a Clinical Informationist on Ward Rounds: An Action Research Study
No full textThis study was conducted with the aim of involving Clinical Informationists (CI) in the hospital setting. It is fundamental-applied research done in an action research method. The research was conducted in the gastrointestinal ward of Al-Zahra Hospital, Isfahan University of Medical Sciences, Iran. The time covered was 2015–2019. Qualitative content analysis and concept mapping were used to analyze the data. Based on the first three steps of Action research, a CI participated in ward round sessions. In the fourth step strengths and weaknesses of the services were explored. In the fifth stage, existing problems, gaps in the way of providing this service, and suggestions were presented. The members of the clinical team were satisfied with the participation of the CI, but in order to improve this participation, technical, structural and individual problems and obstacles are required be addressed. © 2021 The Author(s). Published with license by Taylor & Francis Group, LLC
Passive all-optical polarization switch, binary logic gates, and digital processor
No full text© 2010 Optical Society of AmericaThe definitive version of this paper is available at: http://dx.doi.org/10.1364/OE.19.020332DOI: 10.1364/OE.19.020332We introduce the passive all-optical polarization switch, which modulates light with light. That switch is used to construct all the binary logic gates of two or more inputs. We discuss the design concepts and the operation of the AND, OR, NAND, and NOR gates as examples. The rest of the 16 logic gates are similarly designed. Cascading of such gates is straightforward as we show and discuss. Cascading in itself does not require a power source, but feedback at this stage of development does. The design and operation of an SR Latch is presented as one of the popular basic sequential devices used for memory cells. That completes the essential components of an all-optical polarization digital processor. The speed of such devices is well above 10 GHz for bulk implementations and is much higher for chip-size implementations. In addition, the presented devices do have the four essential characteristics previously thought unique to the microelectronic ones
