The Capacity of Wireless Channels: A Physical Approach

In this paper, the capacity of wireless channels is characterized based on electromagnetic and antenna theories with only minimal assumptions. We assume the transmitter can generate an arbitrary current distribution inside a spherical region and the receive antennas are uniformly distributed on a bigger sphere surrounding the transmitter. The capacity is shown to be $(\alpha P/N_0) \log e$ [bits/sec] in the limit of large number of receive antennas, where $P$ is the transmit power constraint, $\alpha$ is the normalized density of the receive antennas and $N_0$ is the noise power spectral density. Although this result may look trivial, it is surprising in two ways. First, this result holds regardless of the bandwidth (bandwidth can even be negligibly small). Second, this result shows that the capacity is irrespective of the size of the region containing the transmitter. This is against some previous results that claimed the maximum degrees of freedom is proportional to the surface area containing the transmitter normalized by the square of the wavelength. Our result has important practical implications since it shows that even a compact antenna array with negligible bandwidth and antenna spacing well below the wavelength can provide a huge throughput as if the array was big enough so that the antenna spacing is on the order of the wavelength.Comment: 5 pages, to appear in proceedings of 2013 IEEE ISI

Efficient Graduated Non-Convexity for Pose Graph Optimization

We propose a novel approach to Graduated Non-Convexity (GNC) and demonstrate its efficacy through its application in robust pose graph optimization, a key component in SLAM backends. Traditional GNC methods often rely on heuristic methods for GNC schedule, updating control parameter {\mu} for escalating the non-convexity. In contrast, our approach leverages the properties of convex functions and convex optimization to identify the boundary points beyond which convexity is no longer guaranteed, thereby eliminating redundant optimization steps in existing methodologies and enhancing both speed and robustness. We show that our method outperforms the state-of-the-art method in terms of speed and accuracy when used for robust back-end pose graph optimization via GNC. Our work builds upon and enhances the open-source riSAM framework. Our implementation can be accessed from: https://github.com/SNU-DLLAB/EGNC-PGOComment: 6 pages, 6 figure

Adaptive Graduated Non-Convexity for Pose Graph Optimization

We present a novel approach to robust pose graph optimization based on Graduated Non-Convexity (GNC). Unlike traditional GNC-based methods, the proposed approach employs an adaptive shape function using B-spline to optimize the shape of the robust kernel. This aims to reduce GNC iterations, boosting computational speed without compromising accuracy. When integrated with the open-source riSAM algorithm, the method demonstrates enhanced efficiency across diverse datasets. Accompanying open-source code aims to encourage further research in this area. https://github.com/SNU-DLLAB/AGNC-PGOComment: 4 pages, 3 figures. Accepted for the workshop on Robotic Perception and Mapping(ROPEM): Frontier Vision & Learning Techniques, organized at the 2023 International Conference on Intelligent Robots and Systems (IROS

Heating Experiment of CNT Cementitious Composites with Single-Walled and Multiwalled Carbon Nanotubes

Carbon nanotubes (CNTs) are a primary nanomaterial that have outstanding physical and mechanical characteristics, and CNTs can be combined with cement-based materials to alter their heating characteristics. In this study, the types of CNTs used were multiwalled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs). Experiments were performed to determine the altered heating characteristics of the CNT cement mortars. The parameters of the experiment were CNT type, CNT content, curing age, and applied voltage. The results for the different CNT cement mortars indicate that mixing SWCNTs with water to produce CNT cement mortars was more effective for modifying the heating characteristics compared to mixing MWCNTs with water. In addition, field emission scanning electron microscope (FE-SEM) images supported the results found in the heating experiments

Real-time label-free quantitative monitoring of biomolecules without surface binding by floating-gate complementary metal-oxide semiconductor sensor array integrated with readout circuitry

We report a label-free field-effect sensing array integrated with complementary metal-oxide semiconductor (CMOS) readout circuitry to detect the surface potential determined by the negative charge in DNA molecules. For real-time DNA quantification, we have demonstrated the measurements of DNA molecules without immobilizing them on the sensing surface which is composed of an array of floating-gate CMOS transistors. This nonimmobilizing technique allows the continuous monitoring of the amount of charged molecules by injecting DNA solutions sequentially. We have carried out the real-time quantitative measurement of 19 bp oligonucleotides and analyzed its sensitivity as a function of pH in buffer solutions. (c) 2007 American Institute of Physics.open2

Nonoperative Korean Medicine Combination Therapy for Lumbar Spinal Stenosis: A Retrospective Case-Series Study

This is a retrospective case series exploring the therapeutic benefits and harm of nonoperative Korean medicine combination therapy for lumbar spinal stenosis (LSS). The medical records of a total of 33 LSS patients, who were treated as inpatients at Mokhuri Neck and Back Hospital, Republic of Korea, from November 2010 to January 2012, were reviewed first and telephone survey on these patients was conducted after one year. Body acupuncture, pharmacoacupuncture, Chuna, and oral administration of herbal medicines were offered to all patients. A Visual analogue scale (VAS) of pain and the walking duration without pain were used to assess the patients during the approximately 1-month treatment period. The average VAS score of pain and the walking duration improved significantly; the VAS score decreased from 9 (SD, 1.15) to 2.75 (2.22) (p<0.01), and the walking duration increased from 5.5 (6.66) to 16.75 (13.00) minutes (p<0.01). No adverse event was reported during the treatment. In addition, the decreased pain level and improved function continued for over one year. Although we did not find definitive evidence, the study results suggest that KM combination therapy may be beneficial for decreasing pain and improving function in LSS patients and may produce comparatively few adverse events

Synergistic effects of COVID-19 pandemic and sedentary lifestyles on obesity rates among South Korean adults

Abstract Since March 2020, South Korea has implemented social distancing measures to reduce the spread of the coronavirus disease (COVID-19). These policies resulted in significant changes in the lifestyle of Korean adults, including spending more time indoors and experiencing increased sedentary time during the pandemic. This study aimed to investigate the combined influence of sedentary lifestyle and the COVID-19 pandemic on obesity rates among adults residing in South Korea. Data were obtained from the 2018–2020 Korea National Health and Nutrition Examination Survey (KNHANES). Multiple logistic regression was used to analyze the synergistic effects of a sedentary lifestyle and COVID-19 on obesity. The prevalence of sedentary lifestyles among the participants increased from 30.4% pre-COVID-19 to 36.6% during the pandemic. Furthermore, the obesity rates were raised independently by COVID-19 (OR: 1.16, 95% CI 1.04–1.30) and by a sedentary lifestyle (OR = 1.17, 95% CI 1.04–1.31). A synergistic effect of a sedentary lifestyle and COVID-19 on obesity was identified (OR: 1.57, 95% CI 1.30–1.85). COVID-19 and a sedentary lifestyle significantly increased the risk of obesity in South Korean adults. Moreover, the combined synergistic effects of these risk factors were too substantial to be disregarded by merely summing their individual effects on obesity

Estimation of Curvature Changes for Steel-Concrete Composite Bridge Using Fiber Bragg Grating Sensors

This study is focused on the verification of the key idea of a newly developed steel-concrete composite bridge. The key idea of the proposed bridge is to reduce the design moment by applying vertical prestressing force to steel girders, so that a moment distribution of a continuous span bridge is formed in a simple span bridge. For the verification of the key technology, curvature changes of the bridge should be monitored sequentially at every construction stage. A pair of multiplexed FBG sensor arrays is proposed in order to measure curvature changes in this study. They are embedded in a full-scale test bridge and measured local strains, which are finally converted to curvatures. From the result of curvature changes, it is successfully ensured that the key idea of the proposed bridge, expected theoretically, is viable

Simplified Load Distribution Factor for Use in LRFD Design

The “S-over” equation for the load distribution factor (LDF) was first introduced in the 1930s in the AASHTO Standard. Finite element studies, however, have shown it to be unsafe in some cases and too conservative in others. AASHTO LRFD 1994 introduced a new LDF equation as a result of the NCHRP 12-26 project. This equation is based on parametric studies and finite element analyses (FEA). It is considered to be a good representation of bridge behavior. However, this equation involves a longitudinal stiffness parameter, which is not initially known in design. Thus, an iterative procedure is required to correctly determine the LDF value. This need for an iterative design procedure is perceived by practicing engineers as the major impediment to widespread acceptance of the AASHTO LRFD equation. In this study, a new simplified equation that is based on the AASHTO LRFD formula and does not require an iterative procedure is developed. A total of 43 steel girder bridges and 17 prestressed concrete girder bridges in the state of Indiana are selected and analyzed using a sophisticated finite element model. The new simplified equation produces LDF values that are always conservative when compared to those obtained from the finite element analyses and are generally greater than the LDF obtained using AASHTO LRFD specification. Therefore, the simplified equation provides a simple yet safe specification for LDF calculation. This study also investigates the effects of secondary elements and bridge deck cracking on the LDF of bridges. The AASHTO LRFD LDF equation was developed based on elastic finite element analysis considering only primary members, i.e., the effects of secondary elements such as lateral bracing and parapets were not considered. Meanwhile, many bridges have been identified as having significant cracking in the concrete deck. Even though deck cracking is a well-known phenomenon, the significance of pre-existing cracks on the live load distribution has not yet been assessed in the literature. First, secondary elements such as diaphragms and parapet were modeled using the finite element method, and the calculated load distribution factors were compared with the code-specified values. Second, the effects of typical deck cracking and crack types that have a major effect on load distribution were identified through a number of nonlinear finite element analyses. It was found that the presence of secondary elements can result in a load distribution factor up to 40 % lower than the AASHTO LRFD value. Longitudinal cracking was found to increase the load distribution factor; the resulting load distribution factor can be up to 17 % higher than the LRFD value. Transverse cracking was found to not significantly influence the transverse distribution of moment. Finally, for one of the selected bridges, both concrete cracking and secondary elements are considered to invesitigate their combined effect on lateral load distribution. The increased LDF due to deck cracking is offset by the contributions from the secondary elements. The result is that the proposed simplified equation is conservative and is recommended for determination of LDF