52,216 research outputs found
Statistical novelty detection within the Yeongjong suspension bridge under environmental and operational variations
No full textStructural health monitoring is concerned with estimating the current health state of a structure being monitored and aims to provide reliable information on the presence, location, and severity of damage. When the structure experiences damage, it causes changes in structural parameters such as stiffness reduction and consequently alters measured signals or features extracted from the measured signals. Therefore, damage diagnosis can often be performed by novelty detection, i.e., detecting the changes in the measured signals or the features by comparing the most recent data obtained from an unknown condition of the structure with the baseline data accumulated from its normal conditions. In reality, time-varying environmental and operational conditions such as temperature, wind, and traffic loading also induce changes in the measured signals or the features and consequently may produce false alarms. Therefore, to achieve successful novelty detection, it is necessary to distinguish the signal changes caused by abnormality from those caused by environmental and operational variations. This process is called data normalization. In this study, kernel principal component analysis is employed to perform data normalization and incorporated with a novelty index and generalized extreme value statistics for novelty detection. The proposed approach is applied to the field data obtained from the Yeongjong grand bridge in Korea and demonstrated to be a promising tool for detecting abnormality in the presence of environmental and operational variations.The authors express gratitude to New Airport Hiway Co.
Ltd for providing the hanger tension data of the Yeongjong
grand bridge in Korea. This research is supported by the
Radiation Technology Program under Korea Science and
Engineering Foundation (KOSEF) and the Ministry of Science
and Technology (M20703000015-07N0300-01510) and by the
Korean Ministry of Land, Transportation and Maritime Affairs
(MLTM-07-HighTech-A01). Any opinions, findings, and
conclusions or recommendations expressed in this material are
those of the authors and do not necessarily reflect the views of
the funding agencies
System change detection within the yong jong suspension bridge subject to environmental and operational variations
No full textUltrasonic wireless sensor development for online fatigue crack detection and failure warning
No full textThis paper develops a wireless sensor for online fatigue crack detection and failure warning based on crack-induced nonlinear ultrasonic modulation. The wireless sensor consists of packaged piezoelectric (PZT) module, an excitation/sensing module, a data acquisition/processing module, a wireless communication module, and a power supply module. The packaged PZT and the excitation/sensing module generate ultrasonic waves on a structure and capture the response. Based on nonlinear ultrasonic modulation created by a crack, the data acquisition/processing module periodically performs fatigue crack diagnosis and provides failure warning if a component failure is imminent. The outcomes are transmitted to a base through the wireless communication module where two-levels duty cycling media access control (MAC) is implemented. The uniqueness of the paper lies in that 1) the proposed wireless sensor is developed specifically for online fatigue crack detection and failure warning, 2) failure warning as well as crack diagnosis are provided based on crack-induced nonlinear ultrasonic modulation, 3) event-driven operation of the sensor, considering rare extreme events such as earthquakes, is made possible with a power minimization strategy, and 4) the applicability of the wireless sensor to steel welded members is examined through field and laboratory tests. A fatigue crack on a steel welded specimen was successfully detected when the overall width of the crack was around 30 mu m, and a failure warnings were provided when about 97.6% of the remaining useful fatigue lives were reached. Four wireless sensors were deployed on Yeongjong Grand Bridge in Souht Korea. The wireless sensor consumed 282.95 J for 3 weeks, and the processed results on the sensor were transmitted up to 20 m with over 90% success rate.
Constraint-based human resource allocation in software projects
No full textResource allocation in a software project is crucial for successful software development. Among various types of resources, human resource is the most important as software development is a human-intensive activity. Human resource allocation is very complex owing to the human characteristics of developers. The human characteristics affecting allocation can be grouped into individual-level characteristics and team-level characteristics. At the individual level, familiarity with tasks needs to be taken into account as it affects the performance of developers. In addition, developers have different levels of productivity, depending on their capability and experience; the productivity of developers also varies according to tasks. At the team level, characteristics such as team cohesion, communication overhead, and collaboration and management also affect human resource allocation. As these characteristics affect the efficiency of project execution, we treat them as constraints of human resource allocation in our approach. We identify individual-level constraints and team-level constraints based on the literature and interviews with experts in the industry. With these constraints, our approach optimizes the scheduling of human resource allocations, resulting in more realistic and efficient allocations. We also provide a guideline supporting various factors, with respect to roles and module characteristics, to estimate the productivity of developers based on COCOMO II. As productivity data are hard to obtain and manage, our guideline can provide a useful direction for human resource allocation in case of software projects. To validate our proposed approach, we document a case study using real project data. Copyright (C) 2011 John Wiley & Sons, Ltd
Neuroprotection: Rescue from Neuronal Death in the Brain
No full textDear Colleagues, The brain is vulnerable to injury. Following injury in the brain, apoptosis or necrosis may occur easily, leading to various functional disabilities. Neuronal death is associated with a number of neurological disorders including hypoxic ischemia, epileptic seizures, and neurodegenerative diseases. The brain subjected to injury is regarded to be responsible for the alterations in neurotransmission processes, resulting in functional changes. Oxidative stress produced by reactive oxygen species has been shown to be related to the death of neurons in traumatic injury, stroke, and neurodegenerative diseases. Therefore, scavenging or decreasing free radicals may be crucial for preventing neural tissues from harmful adversities in the brain. Neurotrophic factors, bioactive compounds, dietary nutrients, or cell engineering may ameliorate the pathological processes related to neuronal death or neurodegeneration and appear beneficial for improving neuroprotection. As a result of neuronal death or neuroprotection, the brain undergoes activity-dependent long-lasting changes in synaptic transmission, which is also known as functional plasticity. Neuroprotection implying the rescue from neuronal death is now becoming one of global health concerns. This Special Issue attempts to explore the recent advances in neuroprotection related to the brain. This Special Issue welcomes original research or review papers demonstrating the mechanisms of neuroprotection against brain injury using in vivo or in vitro models of animals as well as in clinical settings. The issues in a paper should be supported by sufficient data or evidence. Prof. Bae Hwan Lee Guest Edito
Neuroprotection: Rescue from Neuronal Death in the Brain
Get PDFDear Colleagues, The brain is vulnerable to injury. Following injury in the brain, apoptosis or necrosis may occur easily, leading to various functional disabilities. Neuronal death is associated with a number of neurological disorders including hypoxic ischemia, epileptic seizures, and neurodegenerative diseases. The brain subjected to injury is regarded to be responsible for the alterations in neurotransmission processes, resulting in functional changes. Oxidative stress produced by reactive oxygen species has been shown to be related to the death of neurons in traumatic injury, stroke, and neurodegenerative diseases. Therefore, scavenging or decreasing free radicals may be crucial for preventing neural tissues from harmful adversities in the brain. Neurotrophic factors, bioactive compounds, dietary nutrients, or cell engineering may ameliorate the pathological processes related to neuronal death or neurodegeneration and appear beneficial for improving neuroprotection. As a result of neuronal death or neuroprotection, the brain undergoes activity-dependent long-lasting changes in synaptic transmission, which is also known as functional plasticity. Neuroprotection implying the rescue from neuronal death is now becoming one of global health concerns. This Special Issue attempts to explore the recent advances in neuroprotection related to the brain. This Special Issue welcomes original research or review papers demonstrating the mechanisms of neuroprotection against brain injury using in vivo or in vitro models of animals as well as in clinical settings. The issues in a paper should be supported by sufficient data or evidence. Prof. Bae Hwan Lee Guest Edito
Concepts and Models of Environment of Self-Adaptive Systems: A Systematic Literature Review
No full textThe runtime environment is an important concern for self-adaptive systems (SASs). Although researchers have proposed many approaches for developing SASs that address the issues from runtime environments, the understanding of these environments varies depending on the objectives, perspectives, and assumptions of the research. Thus, the current understanding of environments in SAS development remains ambiguous and abstract. To make this knowledge more concrete, we investigated concepts and models of the environment covered in this area through a systematic literature review (SLR). We automatically and manually searched 3719 papers and selected 128 papers as primary studies. We explored and analyzed concepts of the environment covered in the primary studies and investigated cases in which the concepts were specifically expressed as environment models. In doing so, we provide trends of how SAS academia understands the environment of SAS. Specifically, this SLR provides five common characteristics of the environment, two common sources of the environmental uncertainty, and 14 reference environment models with various purpose and expressiveness. Finally, we summarized lessons learned through this SLR and directions for future SAS research on the basis of the concrete knowledge of the SAS environment
Dynamic project performance estimation by combining static estimation models with system dynamics
No full textChanges in user requirements or project personnel occur frequently during project execution particularly in long-term and large-size projects. We need a tool which can estimate the effects of changing conditions to effectively manage the project. This paper proposes a simulation method for dynamic project performance in terms of effort, schedule, and defect density changes in a dynamic project environment by combining COCOMO II with system dynamics. We apply expert judgment technique to overcome the lack of empirical data on the effects of dynamic project environment. We develop a simulation tool (available on the authors' website) which has model adjustment parameters to reflect experts estimation on project characteristics. The simulation experiment on a military application development project demonstrates that the developed model can show the behavioral characteristics of a project suffering unanticipated and uncontrolled requirements creep. This helps project managers understand interactions between project factors and proactively evaluate and control the effects of dynamic project environment. (C) 2008 Elsevier B.V. All rights reserved.This research was supported by the MKE (Ministry of Knowledge
Economy), Korea, under the ITRC (Information Technology
Research Center) support program supervised by the IITA(Institute
of Information Technology Advancement) (IITA-2007-(C1090-
0701-0032)). This work was partially supported by Defense
Acquisition Program Administration and Agency for Defense
Development under the contract
- …
