Devices, algorithms and systems for maritime persistent surveillance

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 206-219).This thesis presents a novel approach to long-term marine data collection and monitoring. Long-term marine data collection is a key component for understanding planetary scale physical processes and for studying and understanding marine life. Marine monitoring is an important activity for border protection, port security and offshore oil field operations. However, monitoring is not easy because salt water is a harsh environment for humans and for instruments. Radio communication and remote sensing are difficult below ocean surface. Our approach to ocean data collection relies on the integration of (1) a network of underwater sensor nodes with acoustic and optical communication, (2) an autonomous underwater vehicle (AUV) and (3) a novel sensing device. A key characteristic is the extensive use of visible light for information transfer underwater. We use light for sensing, communication and control. We envision a system composed of sensor nodes that are deployed at static locations for data collection. Using acoustic signaling and pairwise ranging the sensor nodes can compute their positions (self-localize) and track mobile objects (e.g., AUVs). The AUV can visit the sensor nodes periodically and download their data using the high speed, low power optical communication. One consequence of using optical communication for the bulk of the data transfer is that less data needs to be transferred over the acoustic links, thus enabling the use of low power, low data rate techniques. For navigation, the AUV can rely on the tracking information provided by the sensor network. In addition, the AUV can dock and transport sensor nodes efficiently, enabling their autonomous relocation and recovery. The main application of our system is coral reef ecosystem research and health monitoring.(cont.) In this application the robot and the sensor nodes can be fitted with our novel imaging sensor, capable of taking underwater color-accurate photographs for reef health assessment and species identification. Compared to existing techniques, our approach: (1) simplifies the deployment of sensors through sensor self-localization, (2) provides sensor status information and thus enables the user to capture rare events or to react to sensor failure, (3) provides the user real time data and thus enables adaptive sampling, (4) simplifies mobile sensing underwater by providing position information to underwater robots, (5) collects new types of data (accurate color images) through the use of new sensors. We present several innovations that enable our approach: (1) an adaptive illumination approach to underwater imaging, (2) an underwater optical communication system using green light, (3) a low power modulation and medium access protocol for underwater acoustic telemetry, (4) a new AUV design capable of hovering and of efficiently transporting dynamic payloads. We present the design, fabrication and evaluation of a hardware platform to validate our approach. Our platform includes: (1) AquaNet, a wireless underwater sensor network composed of AquaNodes, (2) Amour, an underwater vehicle capable of autonomous navigation, data muling, docking and efficient transport of dynamic payloads and (3) AquaLight an underwater variable-spectrum Xenon strobe which enables underwater color accurate photography. We use this platform to implement and experimentally evaluate our algorithms and protocols.by Iuliu Vasilescu.Ph.D

The Complexity of Safety Stock Placement in General-Network Supply Chains

We consider the optimization problem of safety stock placement in a supply chain, as formulated in [1]. We prove that this problem is NP-Hard for supply chains modeled as general acyclic networks. Thus, we do not expect to find a polynomial-time algorithm for safety stock placement for a general-network supply chain.Singapore-MIT Alliance (SMA

Krill: An exploration in underwater sensor networks

While sensor networks have now become very popular on land, the underwater environment still poses some difficult problems. Communication is one of the difficult challenges under water. There are two options: optical and acoustic. We have designed an optical communication board that allows the Fleck’s to communicate optically. We have tested the resulting underwater sensor nodes in two different applications

Autonomous gathering of livestock using a multi-functional sensor network platform

In this paper we develop algorithms and hardware for the autonomous gathering of cattle. We present a comparison of three different autonomous gathering algorithms that employ sound and/or electric stimuli to guide the cattle. We evaluate these algorithms in simulation by extending previous behavioral simulations for cattle. We implemented one of these algorithms and present data from experiments in which cattle were equipped with sensor nodes that allowed cueing with sound and electric stimuli. We discuss the minimum requirements for algorithms and hardware for autonomous gathering

FlexTDOA : Robust and Scalable Time-Difference of Arrival Localization Using Ultra-Wideband Devices

In this paper, we propose FlexTDOA, an indoor localization method using ultra-wideband (UWB) radios, and we demonstrate its performance in a functional system. Our method uses time-difference of arrival (TDOA) localization so that the user device remains passive and is able to compute its location simply by listening to the communication between the fixed anchors, ensuring the scalability of the system. The anchors communicate using a custom and flexible time-division multiple-access (TDMA) scheme in which time is divided in slots. In each time slot, one anchor interrogates one or more anchors which respond in the same slot. The anchors do not need to have their clocks synchronized. We implemented FlexTDOA on in-house designed hardware using a commercial UWB module. We evaluate the localization accuracy of FlexTDOA with different system parameters such as the number of responses, the order of responses, and the number of anchors. We simulate and evaluate the effect of the physical speed of the tag on the choice of optimum system parameters. We also compare FlexTDOA against the classic TDOA approach and range-based localization in a deployment of ten anchors and one tag, both with and without obstructions. Results show that FlexTDOA achieves the highest localization accuracy in most of the scenarios, with up to 38% reduction in the localization error compared to the classic approach.Peer reviewe

Color-accurate underwater imaging using perceptual adaptive illumination

Capturing color in water is challenging due to the heavy non-uniform attenuation of light in water across the visible spectrum, which results in dramatic hue shifts toward blue. Yet observing color in water is important for monitoring and surveillance as well as marine biology studies related to species identification, individual and group behavior, and ecosystem health and activity monitoring. Underwater robots are equipped with motor control for large scale transects but they lack sensors that enable capturing color-accurate underwater images. We present a method for color-accurate imaging in water called perceptual adaptive illumination. This method dynamically mixes the illumination of an object in a distance-dependent way using a controllable multi-color light source. The color mix compensates correctly for color loss and results in an image whose color composition is equivalent to rendering the object in air. Experiments were conducted with a color palette in the pool and at three different coral reefs sites, and with an underwater robot collecting image data with the new sensor.United States. Office of Naval Research (Project N000140911051

It is time to define an organizational model for the prevention and management of infections along the surgical pathway : a worldwide cross-sectional survey

Background The objectives of the study were to investigate the organizational characteristics of acute care facilities worldwide in preventing and managing infections in surgery; assess participants' perception regarding infection prevention and control (IPC) measures, antibiotic prescribing practices, and source control; describe awareness about the global burden of antimicrobial resistance (AMR) and IPC measures; and determine the role of the Coronavirus Disease 2019 pandemic on said awareness. Methods A cross-sectional web-based survey was conducted contacting 1432 health care workers (HCWs) belonging to a mailing list provided by the Global Alliance for Infections in Surgery. The self-administered questionnaire was developed by a multidisciplinary team. The survey was open from May 22, 2021, and June 22, 2021. Three reminders were sent, after 7, 14, and 21 days. Results Three hundred four respondents from 72 countries returned a questionnaire, with an overall response rate of 21.2%. Respectively, 90.4% and 68.8% of participants stated their hospital had a multidisciplinary IPC team or a multidisciplinary antimicrobial stewardship team. Local protocols for antimicrobial therapy of surgical infections and protocols for surgical antibiotic prophylaxis were present in 76.6% and 90.8% of hospitals, respectively. In 23.4% and 24.0% of hospitals no surveillance systems for surgical site infections and no monitoring systems of used antimicrobials were implemented. Patient and family involvement in IPC management was considered to be slightly or not important in their hospital by the majority of respondents (65.1%). Awareness of the global burden of AMR among HCWs was considered very important or important by 54.6% of participants. The COVID-19 pandemic was considered by 80.3% of respondents as a very important or important factor in raising HCWs awareness of the IPC programs in their hospital. Based on the survey results, the authors developed 15 statements for several questions regarding the prevention and management of infections in surgery. The statements may be the starting point for designing future evidence-based recommendations. Conclusion Adequacy of prevention and management of infections in acute care facilities depends on HCWs behaviours and on the organizational characteristics of acute health care facilities to support best practices and promote behavioural change. Patient involvement in the implementation of IPC is still little considered. A debate on how operationalising a fundamental change to IPC, from being solely the HCWs responsibility to one that involves a collaborative relationship between HCWs and patients, should be opened.Peer reviewe

It is time to define an organizational model for the prevention and management of infections along the surgical pathway: a worldwide cross-sectional survey

Background The objectives of the study were to investigate the organizational characteristics of acute care facilities worldwide in preventing and managing infections in surgery; assess participants' perception regarding infection prevention and control (IPC) measures, antibiotic prescribing practices, and source control; describe awareness about the global burden of antimicrobial resistance (AMR) and IPC measures; and determine the role of the Coronavirus Disease 2019 pandemic on said awareness. Methods A cross-sectional web-based survey was conducted contacting 1432 health care workers (HCWs) belonging to a mailing list provided by the Global Alliance for Infections in Surgery. The self-administered questionnaire was developed by a multidisciplinary team. The survey was open from May 22, 2021, and June 22, 2021. Three reminders were sent, after 7, 14, and 21 days. Results Three hundred four respondents from 72 countries returned a questionnaire, with an overall response rate of 21.2%. Respectively, 90.4% and 68.8% of participants stated their hospital had a multidisciplinary IPC team or a multidisciplinary antimicrobial stewardship team. Local protocols for antimicrobial therapy of surgical infections and protocols for surgical antibiotic prophylaxis were present in 76.6% and 90.8% of hospitals, respectively. In 23.4% and 24.0% of hospitals no surveillance systems for surgical site infections and no monitoring systems of used antimicrobials were implemented. Patient and family involvement in IPC management was considered to be slightly or not important in their hospital by the majority of respondents (65.1%). Awareness of the global burden of AMR among HCWs was considered very important or important by 54.6% of participants. The COVID-19 pandemic was considered by 80.3% of respondents as a very important or important factor in raising HCWs awareness of the IPC programs in their hospital. Based on the survey results, the authors developed 15 statements for several questions regarding the prevention and management of infections in surgery. The statements may be the starting point for designing future evidence-based recommendations. Conclusion Adequacy of prevention and management of infections in acute care facilities depends on HCWs behaviours and on the organizational characteristics of acute health care facilities to support best practices and promote behavioural change. Patient involvement in the implementation of IPC is still little considered. A debate on how operationalising a fundamental change to IPC, from being solely the HCWs responsibility to one that involves a collaborative relationship between HCWs and patients, should be opened