System identification of an in-service railroad bridge using wireless smart sensors

Robin E. Kim,Fernando Moreu,Billie F. Spencer, Jr 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.15 No.3

Railroad bridges form an integral part of railway infrastructure throughout the world. Toaccommodate increased axel loads, train speeds, and greater volumes of freight traffic, in the presence ofchanging structural conditions, the load carrying capacity and serviceability of existing bridges must beassessed. One way is through system identification of in-service railroad bridges. To dates, numerousresearchers have reported system identification studies with a large portion of their applications beinghighway bridges. Moreover, most of those models are calibrated at global level, while only a few studiesapplications have used globally and locally calibrated model. To reach the global and local calibration, bothambient vibration tests and controlled tests need to be performed. Thus, an approach for systemidentification of a railroad bridge that can be used to assess the bridge in global and local sense is needed. This study presents system identification of a railroad bridge using free vibration data. Wireless smartsensors are employed and provided a portable way to collect data that is then used to determine bridgefrequencies and mode shapes. Subsequently, a calibrated finite element model of the bridge provides globaland local information of the bridge. The ability of the model to simulate local responses is validated bycomparing predicted and measured strain in one of the diagonal members of the truss. This researchdemonstrates the potential of using measured field data to perform model calibration in a simple andpractical manner that will lead to better understanding the state of railroad bridges.

Synchronized sensing for wireless monitoring of large structures

Robin E. Kim,Jian Li,Billie F. Spencer, Jr,Tomonori Nagayama,Kirill A. Mechitov 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.5

Advances in low-cost wireless sensing have made instrumentation of large civil infrastructure systems with dense arrays of wireless sensors possible. A critical issue with regard to effective use of the information harvested from these sensors is synchronized sensing. Although a number of synchronization methods have been developed, most provide only clock synchronization. Synchronized sensing requires not only clock synchronization among wireless nodes, but also synchronization of the data. Existing synchronization protocols are generally limited to networks of modest size in which all sensor nodes are within a limited distance from a central base station. The scale of civil infrastructure is often too large to be covered by a single wireless sensor network. Multiple independent networks have been installed, and post-facto synchronization schemes have been developed and applied with some success. In this paper, we present a new approach to achieving synchronized sensing among multiple networks using the Pulse-Per-Second signals from low-cost GPS receivers. The method is implemented and verified on the Imote2 sensor platform using TinyOS to achieve 50 us synchronization accuracy of the measured data for multiple networks. These results demonstrate that the proposed approach is highly-scalable, realizing precise synchronized sensing that is necessary for effective structural health monitoring.

System identification of an in-service railroad bridge using wireless smart sensors

Kim, Robin E.,Moreu, Fernando,Spencer, Billie F. Techno-Press 2015 Smart Structures and Systems, An International Jou Vol.15 No.3

Railroad bridges form an integral part of railway infrastructure throughout the world. To accommodate increased axel loads, train speeds, and greater volumes of freight traffic, in the presence of changing structural conditions, the load carrying capacity and serviceability of existing bridges must be assessed. One way is through system identification of in-service railroad bridges. To dates, numerous researchers have reported system identification studies with a large portion of their applications being highway bridges. Moreover, most of those models are calibrated at global level, while only a few studies applications have used globally and locally calibrated model. To reach the global and local calibration, both ambient vibration tests and controlled tests need to be performed. Thus, an approach for system identification of a railroad bridge that can be used to assess the bridge in global and local sense is needed. This study presents system identification of a railroad bridge using free vibration data. Wireless smart sensors are employed and provided a portable way to collect data that is then used to determine bridge frequencies and mode shapes. Subsequently, a calibrated finite element model of the bridge provides global and local information of the bridge. The ability of the model to simulate local responses is validated by comparing predicted and measured strain in one of the diagonal members of the truss. This research demonstrates the potential of using measured field data to perform model calibration in a simple and practical manner that will lead to better understanding the state of railroad bridges.

The dynamics of the piglet gut microbiome during the weaning transition in association with health and nutrition

Guevarra, Robin B.,Hong, Sang Hyun,Cho, Jin Ho,Kim, Bo-Ra,Shin, Jiwon,Lee, Jun Hyung,Kang, Bit Na,Kim, Young Hwa,Wattanaphansak, Suphot,Isaacson, Richard E.,Song, Minho,Kim, Hyeun Bum BioMed Central 2018 Journal of animal science and biotechnology Vol.9 No.-

<P><B>Background</B></P><P>Understanding the composition of the microbial community and its functional capacity during weaning is important for pig production as bacteria play important roles in the pig’s health and growth performance. However, limited information is available regarding the composition and function of the gut microbiome of piglets in early-life. Therefore, we performed 16S rRNA gene and whole metagenome shotgun sequencing of DNA from fecal samples from healthy piglets during weaning to measure microbiome shifts, and to identify the potential contribution of the early-life microbiota in shaping piglet health with a focus on microbial stress responses, carbohydrate and amino acid metabolism.</P><P><B>Results</B></P><P>The analysis of 16S rRNA genes and whole metagenome shotgun sequencing revealed significant compositional and functional differences between the fecal microbiome in nursing and weaned piglets. The fecal microbiome of the nursing piglets showed higher relative abundance of bacteria in the genus <I>Bacteroides</I> with abundant gene families related to the utilization of lactose and galactose. <I>Prevotella</I> and <I>Lactobacillus</I> were enriched in weaned piglets with an enrichment for the gene families associated with carbohydrate and amino acid metabolism. In addition, an analysis of the functional capacity of the fecal microbiome showed higher abundances of genes associated with heat shock and oxidative stress in the metagenome of weaned piglets compared to nursing piglets.</P><P><B>Conclusions</B></P><P>Overall, our data show that microbial shifts and changes in functional capacities of the piglet fecal microbiome resulted in potential reductions in the effects of stress, including dietary changes that occur during weaning. These results provide us with new insights into the piglet gut microbiome that contributes to the growth of the animal.</P><P><B>Electronic supplementary material</B></P><P>The online version of this article (10.1186/s40104-018-0269-6) contains supplementary material, which is available to authorized users.</P>

Deciphering Diversity Indices for a Better Understanding of Microbial Communities

( Bo-ra Kim ),( Jiwon Shin ),( Robin B. Guevarra ),( Jun Hyung Lee ),( Doo Wan Kim ),( Kuk-hwan Seol ),( Ju-hoon Lee ),( Hyeun Bum Kim ),( Richard E. Isaacson ) 한국미생물생명공학회(구 한국산업미생물학회) 2017 Journal of microbiology and biotechnology Vol.27 No.12

The past decades have been a golden era during which great tasks were accomplished in the field of microbiology, including food microbiology. In the past, culture-dependent methods have been the primary choice to investigate bacterial diversity. However, using culture-independent high-throughput sequencing of 16S rRNA genes has greatly facilitated studies exploring the microbial compositions and dynamics associated with health and diseases. These culture-independent DNA-based studies generate large-scale data sets that describe the microbial composition of a certain niche. Consequently, understanding microbial diversity becomes of greater importance when investigating the composition, function, and dynamics of the microbiota associated with health and diseases. Even though there is no general agreement on which diversity index is the best to use, diversity indices have been used to compare the diversity among samples and between treatments with controls. Tools such as the Shannon- Weaver index and Simpson index can be used to describe population diversity in samples. The purpose of this review is to explain the principles of diversity indices, such as Shannon- Weaver and Simpson, to aid general microbiologists in better understanding bacterial communities. In this review, important questions concerning microbial diversity are addressed. Information from this review should facilitate evidence-based strategies to explore microbial communities.

Nanocomposites of poly(L-lysine) and single-walled carbon nanotubes

Kim, Jong-Beom,Premkumar, Thathan,Giani, Olivia,Robin, Jean-Jaques,Schue, Francois,Geckeler, Kurt E John Wiley Sons, Ltd. 2008 Polymer international Vol.57 No.2

<P>BACKGROUND: Single-walled carbon nanotubes have inspired research owing to their promise in a broad range of applications. The dispersion of carbon nanotubes is of key importance for the utilization of this interesting material for various potential applications.</P><P>RESULTS: A novel and simple method was developed to fabricate polymer composites with single-walled carbon nanotubes based on a solid-state reaction, in which the nanotubes were reacted with poly(L-lysine) using high-speed vibration milling. Fourier transform infrared and UV-visible spectroscopy as well as thermogravimetry were employed to characterize the novel composites. The morphology and the dispersion of the carbon nanotubes were determined using scanning and transmission electron microscopy.</P><P>CONCLUSION: The resulting composites were dispersable in water and are expected to have great potential for both molecular-level studies and device applications of nanotubes. Copyright © 2007 Society of Chemical Industry</P>

Microwave-driven coherent operation of a semiconductor quantum dot charge qubit.

Kim, Dohun,Ward, D R,Simmons, C B,Gamble, John King,Blume-Kohout, Robin,Nielsen, Erik,Savage, D E,Lagally, M G,Friesen, Mark,Coppersmith, S N,Eriksson, M A Nature Pub. Group 2015 Nature nanotechnology Vol.10 No.3

<P>An intuitive realization of a qubit is an electron charge at two well-defined positions of a double quantum dot. This qubit is simple and has the potential for high-speed operation because of its strong coupling to electric fields. However, charge noise also couples strongly to this qubit, resulting in rapid dephasing at all but one special operating point called the 'sweet spot'. In previous studies d.c. voltage pulses have been used to manipulate semiconductor charge qubits but did not achieve high-fidelity control, because d.c. gating requires excursions away from the sweet spot. Here, by using resonant a.c. microwave driving we achieve fast (greater than gigahertz) and universal single qubit rotations of a semiconductor charge qubit. The Z-axis rotations of the qubit are well protected at the sweet spot, and we demonstrate the same protection for rotations about arbitrary axes in the X-Y plane of the qubit Bloch sphere. We characterize the qubit operation using two tomographic approaches: standard process tomography and gate set tomography. Both methods consistently yield process fidelities greater than 86% with respect to a universal set of unitary single-qubit operations.</P>

Piglet gut microbial shifts early in life: causes and effects

Guevarra, Robin B.,Lee, Jun Hyung,Lee, Sun Hee,Seok, Min-Jae,Kim, Doo Wan,Kang, Bit Na,Johnson, Timothy J.,Isaacson, Richard E.,Kim, Hyeun Bum BioMed Central 2019 Journal of animal science and biotechnology Vol.10 No.1

<P>The gut microbiome has long been known to play fundamentally important roles in the animal health and the well-being of its host. As such, the establishment and maintenance of a beneficial gut microbiota early in life is crucial in pigs, since early gut colonizers are pivotal in the establishment of permanent microbial community structures affecting the health and growth performance of pigs later in life. Emphasizing this importance of early gut colonizers, it is critical to understand the factors impacting the establishment of the piglet gut microbiome at weaning. Factors include, among others, diet, in-feed antibiotics, probiotics and prebiotic administration. The impact of these factors on establishment of the gut microbiome of piglets at weaning includes effects on piglet gut microbial diversity, structure, and succession. In this review, we thoroughly reviewed the most recent findings on the piglet gut microbiome shifts as influenced by weaning, and how these microbiome changes brought about by various factors that have been shown to affect the development of microbiota in piglets. This review will provide a general overview of recent studies that can help to facilitate the design of new strategies to modulate the gut microbiome in order to enhance gastrointestinal health, growth performance and well-being of piglets.</P>

Hybrid Simulation Method for a Structure Subjected to Fire and Its Application to a Steel Frame

Wang, Xuguang,Kim, Robin E.,Kwon, Oh-Sung,Yeo, Inhwan American Society of Civil Engineers 2018 Journal of structural engineering Vol.144 No.8

Surface Modification of Droplet Polymeric Microfluidic Devices for the Stable and Continuous Generation of Aqueous Droplets

Subramanian, Balamurugan,Kim, Namwon,Lee, Wonbae,Spivak, David A.,Nikitopoulos, Dimitris E.,McCarley, Robin L.,Soper, Steven A. American Chemical Society 2011 Langmuir Vol.27 No.12

<P>Droplet microfluidics performed in poly(methyl methacrylate) (PMMA) microfluidic devices resulted in significant wall wetting by water droplets formed in a liquid–liquid segmented flow when using a hydrophobic carrier fluid such as perfluorotripropylamine (FC-3283). This wall wetting led to water droplets with nonuniform sizes that were often trapped on the wall surfaces, leading to unstable and poorly controlled liquid–liquid segmented flow. To circumvent this problem, we developed a two-step procedure to hydrophobically modify the surfaces of PMMA and other thermoplastic materials commonly used to make microfluidic devices. The surface-modification route involved the introduction of hydroxyl groups by oxygen plasma treatment of the polymer surface followed by a solution-phase reaction with heptadecafluoro-1,1,2,2-tetrahydrodecyl trichlorosilane dissolved in fluorocarbon solvent FC-3283. This procedure was found to be useful for the modification of PMMA and other thermoplastic surfaces, including polycyclic olefin copolymer (COC) and polycarbonate (PC). Angle-resolved X-ray photoelectron spectroscopy indicated that the fluorination of these polymers took place with high surface selectivity. This procedure was used to modify the surface of a PMMA droplet microfluidic device (DMFD) and was shown to be useful in reducing the wetting problem during the generation of aqueous droplets in a perfluorotripropylamine (FC-3283) carrier fluid and could generate stable segmented flows for hours of operation. In the case of PMMA DMFD, oxygen plasma treatment was carried out after the PMMA cover plate was thermally fusion bonded to the PMMA microfluidic chip. Because the appended chemistry to the channel wall created a hydrophobic surface, it will accommodate the use of other carrier fluids that are hydrophobic as well, such as hexadecane or mineral oils.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/langd5/2011/langd5.2011.27.issue-12/la200298n/production/images/medium/la-2011-00298n_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/la200298n'>ACS Electronic Supporting Info</A></P>