35 research outputs found
A Decentralized Pilot Assignment Algorithm for Scalable O-RAN Cell-Free Massive MIMO
Radio access networks (RANs) in monolithic architectures have limited
adaptability to supporting different network scenarios. Recently, open-RAN
(O-RAN) techniques have begun adding enormous flexibility to RAN
implementations. O-RAN is a natural architectural fit for cell-free massive
multiple-input multiple-output (CFmMIMO) systems, where many
geographically-distributed access points (APs) are employed to achieve
ubiquitous coverage and enhanced user performance. In this paper, we address
the decentralized pilot assignment (PA) problem for scalable O-RAN-based
CFmMIMO systems. We propose a low-complexity PA scheme using a multi-agent deep
reinforcement learning (MA-DRL) framework in which multiple learning agents
perform distributed learning over the O-RAN communication architecture to
suppress pilot contamination. Our approach does not require prior channel
knowledge but instead relies on real-time interactions made with the
environment during the learning procedure. In addition, we design a codebook
search (CS) scheme that exploits the decentralization of our O-RAN CFmMIMO
architecture, where different codebook sets can be utilized to further improve
PA performance without any significant additional complexities. Numerical
evaluations verify that our proposed scheme provides substantial computational
scalability advantages and improvements in channel estimation performance
compared to the state-of-the-art.Comment: This paper has been submitted to IEEE Journal on Selected Areas in
Communications for possible publicatio
Radiological diagnosis of congenital diaphragmatic hernia in 17th century Korean mummy.
Congenital diaphragmatic hernia (CDH) is a birth defect of the diaphragm resulting in pulmonary sequelae that threaten the lives of infants. In computed tomography (CT) images of a 17th century middle-aged male mummy (the Andong mummy), we observed that the abdominal contents had protruded into the right thoracic cavity through the diaphragmatic defect, accompanied by a mediastinal shift to the left. On autopsy, the defect in the right posterolateral aspect of the diaphragm was reconfirmed, as was the herniation of the abdominal organs. The herniated contents included the right lobe of the liver, the pyloric part of the stomach, a part of the greater omentum, and the right colic flexure connecting the superior part of the ascending colon and the right part of the transverse colon. Taking our CT and autopsy results together, this case was diagnosed as the Bochdalek-type CDH. Herein we make the first ever report of a CT-assisted diagnosis of a pre-modern historical case of CDH. Our results show the promising utility of this modality in investigations of mummified human remains archaeologically obtained
The potential for non-invasive study of mummies: validation of the use of computerized tomography by post factum dissection and histological examination of a 17th century female Korean mummy
The socio-cultural antipathies of some descendants with regard to invasive examinations of age-old human remains make permission for dissection of Korean mummies of the Joseon Dynasty (1392-1910) difficult to obtain. Overcoming this obstacle necessitated the use of non-invasive techniques, such as multi-detector computerized tomography (MDCT) and endoscopic examination, enabling determination of the preservation status of internal organs of mummies without significantly damaging the mummies themselves. However, MDCT alone cannot clearly differentiate specific mummified organs. Therefore, in much the same way as diagnostic radiologists make their MDCT readings on living patients more reliable by means of comparison with accumulated post-factum data from autopsies or histological studies, examinations of mummies by invasive techniques should not be decried as mere destruction of age-old human remains. Rather, providing that due permission from descendants and/or other relevant authorities can be obtained, dissection and histological examination should be performed whenever opportunities arise. Therefore, in this study, we compared the radiological data acquired from a 17th century mummy with our dissection results for the same subject. As accumulation of this kind of data could be very crucial for correct interpretation of MDCT findings on Korean mummies, we will perform similar trials on other Korean mummies found in forthcoming days if conditions permit
A possible case of cherubism in a 17th-century Korean mummy.
Cherubism is a benign fibro-osseous disease of childhood limited specifically to the maxilla and mandible. The progressive replacement of the jaw bones with expansile multilocular cystic lesions causes eventual prominence of the lower face, and hence the classic "cherubic" phenotype reflecting variable extents of jaw hypertrophy. Histologically, this condition has been characterized as replacement of the normal bone matrix with multicystic pockets of fibrous stroma and osteoclastic giant cells. Because of radiographic features common to both, primarily the presence of multiloculated lucencies with heterogeneous "ground-glass" sclerosis on CT imaging, cherubism was long mistaken for a craniofacial subtype of fibrous dysplasia. In 1999, however, the distinct genetic basis for cherubism was mapped to chromosome 4p16.3 and the SH-3 binding protein SH3BP2. But while there are already three suspected cases of fibrous dysplasia amongst archaeological populations, no definitive cases of cherubism have yet been reported in historical populations. In the current study we describe micro- and macro-structural changes in the face of a 17th century Joseon Dynasty Korean mummy which may coincide with the clinic-pathologic and radiologic features of cherubism
The CT images of this case.
<p>(A) for head; (B) for thorax. Most mummified organs were displaced to the dorsal side of body cavities. Their morphologies were seriously deformed. Br, brain; Ht, heart; RL, right lung; LL, left lung.</p
Anatomical Confirmation of Computed Tomography-Based Diagnosis of the Atherosclerosis Discovered in 17<sup>th</sup> Century Korean Mummy
<div><p>In the present study on a newly discovered 17<sup>th</sup> century Korean mummy, computed tomography (CT) revealed multiple aortic calcifications within the aortic wall that were indicative of ancient atherosclerosis. The CT-based findings were confirmed by our subsequent <i>post-factum</i> dissection, which exhibited possible signs of the disease including ulcerated plaques, ruptured hemorrhages, and intimal thickening where the necrotic core was covered by the fibrous cap. These findings are strong indicators that the mummy suffered from aortic atherosclerosis during her lifetime. The present study is a good example of how CT images of vascular calcifications can be a useful diagnostic tool in forming at least preliminary diagnoses of ancient atherosclerosis.</p></div