k-Space Deep Learning for Reference-free EPI Ghost Correction

Nyquist ghost artifacts in EPI are originated from phase mismatch between the even and odd echoes. However, conventional correction methods using reference scans often produce erroneous results especially in high-field MRI due to the non-linear and time-varying local magnetic field changes. Recently, it was shown that the problem of ghost correction can be reformulated as k-space interpolation problem that can be solved using structured low-rank Hankel matrix approaches. Another recent work showed that data driven Hankel matrix decomposition can be reformulated to exhibit similar structures as deep convolutional neural network. By synergistically combining these findings, we propose a k-space deep learning approach that immediately corrects the phase mismatch without a reference scan in both accelerated and non-accelerated EPI acquisitions. To take advantage of the even and odd-phase directional redundancy, the k-space data is divided into two channels configured with even and odd phase encodings. The redundancies between coils are also exploited by stacking the multi-coil k-space data into additional input channels. Then, our k-space ghost correction network is trained to learn the interpolation kernel to estimate the missing virtual k-space data. For the accelerated EPI data, the same neural network is trained to directly estimate the interpolation kernels for missing k-space data from both ghost and subsampling. Reconstruction results using 3T and 7T in-vivo data showed that the proposed method outperformed the image quality compared to the existing methods, and the computing time is much faster.The proposed k-space deep learning for EPI ghost correction is highly robust and fast, and can be combined with acceleration, so that it can be used as a promising correction tool for high-field MRI without changing the current acquisition protocol.Comment: To appear in Magnetic Resonance in Medicin

Decentralized system identification using stochastic subspace identification for wireless sensor networks

Wireless sensor networks (WSNs) facilitate a new paradigm to structural identification and monitoring for civil infrastructure. Conventional structural monitoring systems based on wired sensors and centralized data acquisition systems are costly for installation as well as maintenance. WSNs have emerged as a technology that can overcome such difficulties, making deployment of a dense array of sensors on large civil structures both feasible and economical. However, as opposed to wired sensor networks in which centralized data acquisition and processing is common practice, WSNs require decentralized computing algorithms to reduce data transmission due to the limitation associated with wireless communication. In this paper, the stochastic subspace identification (SSI) technique is selected for system identification, and SSI-based decentralized system identification (SDSI) is proposed to be implemented in a WSN composed of Imote2 wireless sensors that measure acceleration. The SDSI is tightly scheduled in the hierarchical WSN, and its performance is experimentally verified in a laboratory test using a 5-story shear building model. ??? 2015 by the authors; licensee MDPI, Basel, Switzerlandopen0

Assessment of Animal Palatability for Domestic Developed Italian Ryegrass \u3cem\u3eLolium multiflorum\u3c/em\u3e Lam. in South Korea

About 5.6 million tons of forage were consumed in ruminant animals in Korea. But, most of them were supplied in rice straw (2 million ton) and more than one million ton of forage was imported from oversea. As a matter of fact, the self-sufficiency rate of high quality forage was 44 % (2.5 million ton). The research institute had started breeding programs of forage varieties (orchardgrass, Tall fescue and Italian ryegrass), Their remarkable breeding program resulted in release of a synthetic species Italian ryegrass (Lolium multiflorum Lam.) which was more cold-tolerant, much higher yielding than introduced varieties and more adapted in paddy field. Most varieties had focused in evaluation of chemical analysis and productivities of dry matter, however assessment of palatability for ruminant was not conducted. For this reason, this report examines the assessment of animal palatability for domestic developed Italian ryegrass in Korea

Uterine Artery Doppler Velocimetry During Mid-second Trimester to Predict Complications of Pregnancy Based on Unilateral or Bilateral Abnormalities

We performed this study to evaluate uterine artery Doppler velocimetry (UADV) measurement of unilateral or bilateral abnormalities as a predictor of complications in pregnancy during the mid-second trimester (20-24 weeks). We enrolled 1,090 pregnant women who had undergone UADV twice: once between the 20th and 24th week (1st stage) and again between the 28th and 32nd week (2nd stage) of pregnancy, and then delivered at Yonsei Medical Center. UADV was performed bilaterally. Follow-up UADV was performed between the 28th and 32nd week, and the frequencies of pregnancy-induced hypertension (PIH), fetal growth restriction (FGR), and preterm delivery (before 34 weeks of gestation) were determined. Chi-squared and t-tests were used where appropriate, with p < .05 considered significant. According to the results of UADV performed between 20-24 weeks of gestation, 825 women (75.7%) were included in the normal group, 196 (18.0%) in the unilateral abnormality group, and 69 (6.3%) in the bilateral abnormality group. The incidences of FGR were 8.0%, 10.2%, and 26.1%, and the incidences of PIH were 0.1%, 3.6%, and 14.5%, respectively. The incidence of PIH was significantly lower in the normal group. The incidences of preterm delivery were 2.2%, 5.6%, and 8.7%, respectively. PIH developed in 46.7% of patients with bilateral abnormal findings in both the 1st and 2nd stage tests, and developed in none of the patients with normal findings in both tests. Abnormal results found by UADV performed between the 20-24th weeks of pregnancy, such as high S/D ratios regardless of placental location and the presence of an early diastolic notch, were associated with significant increases in the incidences of intrauterine growth restriction (IUGR) and PIH. This was true for both bilateral and unilateral abnormalities. Abnormal findings in bilateral UADV during the second trimester especially warrant close follow up for the detection of subsequent development of pregnancy complications

Reference-Free Displacement Estimation of Bridges Using Kalman Filter-Based Multimetric Data Fusion

Displacement responses of a bridge as a result of external loadings provide crucial information regarding structural integrity and current conditions. Due to the relative characteristic of displacement, the conventional measurement approach requires reference points to firmly install the transducers, while the points are often unavailable for bridges. In this paper, a displacement estimation approach using Kalman filter-based data fusion is proposed to provide a practical means for displacement measurement. The proposed method enables accurate displacement estimation by optimally utilizing acceleration and strain in combination that have high availability and are free from reference points for sensor installation. The Kalman filter is formulated using a state-space model representing the double integration of acceleration and model-based strain-displacement relationship. The validation of the proposed method is conducted successfully by a numerical simulation and a field experiment, which shows the efficacy and accuracy of the proposed approach in bridge displacement measurement.ope

Lagrangian Formulation of Symmetric Space sine-Gordon Models

The symmetric space sine-Gordon models arise by conformal reduction of ordinary 2-dim $\sigma$-models, and they are integrable exhibiting a black-hole type metric in target space. We provide a Lagrangian formulation of these systems by considering a triplet of Lie groups $F \supset G \supset H$. We show that for every symmetric space $F/G$, the generalized sine-Gordon models can be derived from the $G/H$ WZW action, plus a potential term that is algebraically specified. Thus, the symmetric space sine-Gordon models describe certain integrable perturbations of coset conformal field theories at the classical level. We also briefly discuss their vacuum structure, Backlund transformations, and soliton solutions.Comment: 12 page

Forage Rye Cultivars for Animal Feed in Korea

Rye (Secale cereal L.) is well known for its overwintering ability and has the highest tolerance to cold temperature of the small grain cereals such as wheat, barley, and oat. Rye is used as livestock pasture and as green manure in Korea, and its cultivation area for fodder is about 50,000 ha in 2014. Most rye is grown as a fall-sown annual crop, generally called “winter rye”. In Korea, rye cultivation for whole crop silage (WCS) in the winter-season rice field can be considered as a promising way to enhance feed supply. The WCS production can be an efficient way to use farm products as livestock feed, and it can also contribute to increasing farm income. Although rye is inferior in several ways to the predominant cereal crops (wheat, rice, and maize), it will continue to be an important crop for farmers in Korea because of its winter hardiness and early harvesting by rapid growing ability

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