Simple nonlinear static analysis of steel portal frame with pitched roof exposed to fire

Papadopoulos, Panagis G.,Papadopoulou, Anastassia K.,Papaioannou, Kyriakos K. Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.1

Plane steel portal frames, with pitched roof, exposed to fire, are examined. First, a determinate frame is analysed by hand. For flexible columns and shallow roof, snap-through occurs before plastic hinges mechanism is formed. An indeterminate frame with shorter columns and taller roof is also analysed by hand. Then, the same frame is simulated by a truss and a nonlinear static analysis is performed by use of a short computer program. The results of computer analysis by use of truss model are compared with those of analysis by hand and a satisfactory approximation between them is observed.

The Reality Deck--an Immersive Gigapixel Display

Papadopoulos, Charilaos,Petkov, Kaloian,Kaufman, Arie E.,Mueller, Klaus IEEE 2015 IEEE computer graphics and applications Vol.35 No.1

<P>The Reality Deck is a visualization facility offering state-of-the-art aggregate resolution and immersion. Its a 1.5-Gpixel immersive tiled display with a full 360-degree horizontal field of view. Comprising 416 high-density LED-backlit LCD displays, it visualizes gigapixel-resolution data while providing 20/20 visual acuity for most of the visualization space.</P>

19세기 초엽 그리스의 해방과 유럽의 외교상황

Papadopoulos, Stephanos 동국사학회 1984 동국사학 Vol.18 No.-

Experimental investigation of a new steel friction device with link element for seismic strengthening of structures

Papadopoulos, Panikos K.,Salonikios, Thomas N.,Dimitrakis, Stergios A.,Papadopoulos, Alkis P. Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.4

In the present work a new friction device, with a set of single or double rotational friction flanges and a link element, is described and tested. The mechanism may be applied for the strengthening of existing r/c or steel buildings as well as in new constructed buildings. The device has selectable variable behavior in different levels of displacement and an interlock mechanism that is provided by the link element. The link element may be designed to lock at preselected level of displacement, offering in this way an extra safety reserve against strong earthquakes. A summary of the existing literature about other similar mechanisms is initially presented in this paper. The proposed mechanism is presented and described in details. Laboratory experiments are presented in detail and the resulted response that proves the efficiency of the mechanism at selectable levels of strength capacity is discussed. Drawings of the mechanism attached to a r/c frame with connection details are also included. Finally a dynamic analysis of two r/c frames, with and without the proposed mechanism attached, is performed and the resulted response is given. The main conclusion is that the proposed mechanism is a cheap and efficient devise for the improvement of the performance of new or existing framed buildings to seismic loads.

An algorithm for fast 3D inversion of surface electrical resistivity tomography data: application on imaging buried antiquities

Papadopoulos, N.G.,Tsourlos, P.,Papazachos, C.,Tsokas, G.N.,Sarris, A.,Kim, J.H. Blackwell Publishing Ltd 2011 Geophysical prospecting Vol.59 No.3

<P><B>ABSTRACT</B></P><P>In this work a new algorithm for the fast and efficient 3D inversion of conventional 2D surface electrical resistivity tomography lines is presented. The proposed approach lies on the assumption that for every surface measurement there is a large number of 3D parameters with very small absolute Jacobian matrix values, which can be excluded in advance from the Jacobian matrix calculation, as they do not contribute significant information in the inversion procedure. A sensitivity analysis for both homogeneous and inhomogeneous earth models showed that each measurement has a specific region of influence, which can be limited to parameters in a critical rectangular prism volume. Application of the proposed algorithm accelerated almost three times the Jacobian (sensitivity) matrix calculation for the data sets tested in this work. Moreover, application of the least squares regression iterative inversion technique, resulted in a new 3D resistivity inversion algorithm more than 2.7 times faster and with computer memory requirements less than half compared to the original algorithm. The efficiency and accuracy of the algorithm was verified using synthetic models representing typical archaeological structures, as well as field data collected from two archaeological sites in Greece, employing different electrode configurations. The applicability of the presented approach is demonstrated for archaeological investigations and the basic idea of the proposed algorithm can be easily extended for the inversion of other geophysical data.</P>

Extraperitoneal Spread of Anorectal Abscess: A Case Report and Literature Review

Papadopoulos S. Konstantinos,Dimopoulos Andreas,Kordeni Kleoniki,Filis Dimitrios 대한대장항문학회 2021 Annals of Coloproctolgy Vol.37 No.S

Supralevator abscess is a rare form of anorectal disease responsible for very rare but morbid manifestations, one of which is superior spread through fascial planes. We present a rare case of a spreading anorectal abscess in a patient who presented with only diffuse abdominal pain, and we review similar cases in the literature according to anatomical considerations, presentation, diagnostic procedures, and treatment options. We identified 7 previously reported cases of spreading anorectal abscesses. Most abscesses had a horseshoe morphology, and all patients presented or developed abdominal pain. All patients had perianal swelling and pain. Five out of 7 patients were previously mistreated. Only 2 abscesses spread through both the pre- and retroperitoneal planes. Abdominal pain is a dominant feature of extraperitoneal inflammation originating from anorectal abscesses. The absence of perianal signs is rare, and proper inspection of the patient along with the medical history can lead to quicker diagnosis and decisive treatment.

A Fast Steady-State Loss Model of a Modular Multilevel Converter for Optimization Purposes

A. Papadopoulos,S. Rodrigues,E. Kontos,T. Todorcevic,P. Bauer 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Lesnicar and Marquardt introduced a Modular Multilevel Converter (MMC) topology back in 2003. Although this topology has received a great deal of attention in recent years by both the research community and industry, hitherto no steadystate model has been developed which accurately captured all the relevant power losses while being computationally light. Hence, the aim of this paper is to introduce a fast MMC loss model which captures the key sources of power losses in steady-state operation. The model only requires information which is known a priori, e.g. datasheet information of the components. The proposed model was compared to a loss model developed by Marquardt. Both models presented similar results under the same assumptions. However, the proposed model captures the switching losses more realistically and considers the temperature of operation of the electronics, as well as the losses of the inductors and cooling system in the overall efficiency of the MMC. To validate these new additions, the proposed steady-state model was compared to a dynamic model. Once again the proposed model was able to capture the different sources of power losses. Nonetheless, results demonstrated that the balancing strategy greatly influences the efficiency of the MMC. Therefore, information regarding the envisioned control strategy is necessary to accurately calculate the efficiency curve of the MMC.

Impact of piezocision on orthodontic tooth movement

Nikolaos Papadopoulos,Nicola Beindorff,Stefan Hoffmann,Paul-Georg Jost-Brinkmann,Thomas Michael Prager 대한치과교정학회 2021 대한치과교정학회지 Vol.51 No.6

Objective: This study investigated the impact of a single piezocision in the maxillary alveolar process on the speed of tooth movement. The null hypothesis was that the speed of tooth movement will be equal with and without piezocision. Methods: All maxillary molars on one side were moved against the combined incisors in 10 ten-week-old male Wistar rats. Under general anesthesia, a force of 25 cN was applied on either side using a Sentalloy closed coil spring. After placing the orthodontic appliance, vertical corticision was performed using a piezotome under local anesthesia, 2 mm mesial from the mesial root of the first molar on a randomly selected side; the other side served as the control. At the beginning of the treatment, and 2 and 4 weeks later, skull micro-computed tomography was performed. After image reconstruction, the distance between the mesial root of the first molar and the incisive canal, and the length of the mesial root of the first maxillary molar were measured. Moreover, the root resorption score was determined as described by Lu et al. Results: Significantly higher speed of tooth movement was observed on the corticision side; thus, the null hypothesis was rejected. The loss of root length and root resorption score were significantly more pronounced after piezocision than before. A strong correlation was observed between the speed of tooth movement and root resorption on the surgical side, but the control side only showed a weak correlation. Conclusions: Piezocision accelerates orthodontic tooth movement and causes increased root resorption.

Left Ventricular Hypertrophy and Cerebral Small Vessel Disease: A Systematic Review and Meta-Analysis

Andreas Papadopoulos,Konstantinos Palaiopanos,Athanasios P. Protogerou,George P. Paraskevas,Georgios Tsivgoulis,Marios K. Georgakis 대한뇌졸중학회 2020 Journal of stroke Vol.22 No.2

Background and Purpose Left ventricular hypertrophy (LVH) is associated with the risk of stroke and dementia independently of other vascular risk factors, but its association with cerebral small vessel disease (CSVD) remains unknown. Here, we employed a systematic review and meta-analysis to address this gap. Methods Following the MOOSE guidelines (PROSPERO protocol: CRD42018110305), we systematically searched the literature for studies exploring the association between LVH or left ventricular (LV) mass, with neuroimaging markers of CSVD (lacunes, white matter hyperintensities [WMHs], cerebral microbleeds [CMBs]). We evaluated risk of bias and pooled association estimates with random-effects meta-analyses. Results We identified 31 studies (n=25,562) meeting our eligibility criteria. In meta-analysis, LVH was associated with lacunes and extensive WMHs in studies of the general population (odds ratio [OR]lacunes, 1.49; 95% confidence interval [CI], 1.12 to 2.00) (ORWMH, 1.73; 95% CI, 1.38 to 2.17) and studies in highrisk populations (ORlacunes: 2.39; 95% CI, 1.32 to 4.32) (ORWMH, 2.01; 95% CI, 1.45 to 2.80). The results remained stable in general population studies adjusting for hypertension and other vascular risk factors, as well as in sub-analyses by LVH assessment method (echocardiography/electrocardiogram), study design (cross-sectional/cohort), and study quality. Across LV morphology patterns, we found gradually increasing ORs for concentric remodelling, eccentric hypertrophy, and concentric hypertrophy, as compared to normal LV geometry. LVH was further associated with CMBs in high-risk population studies. Conclusions LVH is associated with neuroimaging markers of CSVD independently of hypertension and other vascular risk factors. Our findings suggest LVH as a novel risk factor for CSVD and highlight the link between subclinical heart and brain damage.

Electroacupuncture for the Treatment of Calcific Tendonitis. A Pilot Study

Georgios Papadopoulos,Alexandros Mavrodontidis,Antonia Liarmakopoulou,Petros Tzimas,Georgios Angelidakis,Panagiotis Koulouvaris,Anastasios Petrou 사단법인약침학회 2018 Journal of Acupuncture & Meridian Studies Vol.11 No.2

Current treatment for calcific tendonitis consists of arm rest, antiinflammatory medications, and corticosteroid injections. If unsuccessful, a lot of clinicians suggest several physiotherapy modalities, such as shockwave therapy and electrotherapy. The purpose of our study was to assess the efficacy of electroacupuncture, as a substitute for failed medical treatment in calcific tendonitis. In a pilot study, we prospectively followed 10 patients treated with electroacupuncture for calcific tendonitis who failed to respond to medical treatment. Its efficacy was assessed by evaluating the level of pain, the Beck Depression Inventory, the range of active elbow mobility, and by repeated radiological evaluation of the course of calcific deposits. All clinical and radiological observations were recorded before and within 6 months after the onset of treatment. After electroacupuncture treatment (2 Hz, 180 mA for 30–60 seconds at GB21, GB34, LI4, LI 14, LI15, TW5, TW14, Chien Chien SI9, SI12, S37, S38), the visual analog score decreased notably, and the range of motion returned to normal. Radiological evaluation demonstrated almost complete absorption of calcific deposits within 6 months, after treatment. We conclude that electroacupuncture relieved skeletal pain, improved the quality of patient's life, and contributed to total regression of the calcific depositions in followed patients. So, electroacupuncture may be a valuable treatment option for calcific tendonitis, when medical treatment fails to relieve symptoms.