Flow-Induced Stresses and Displacements in Jointed Concrete Pipes Installed by Pipe Jacking Method

Transient flows result in unbalanced forces and high pressure in pipelines. Under these conditions, the combined effects of flow-induced forces along with sudden pipe displacements can create cracks in the pipeline, especially at the junctions. This situation consequently results in water leakage and reduced operational efficiency of the pipeline. In this study, displacements and stresses in a buried pressurized water transmission pipe installed by pipe jacking method are investigated using numerical modeling and considering interactions between fluid, pipe, and soil. The analyses were performed consecutively under no-flow, steady flow, and transient flow conditions, in order to investigate the effects of flow conditions on displacements and stresses in the system. Analyses of the results show that displacements and stresses in the jointed concrete pipes are significant under transient flow conditions. Moreover, because of pressure transient effects, maximum tensile stresses exceed the tensile strength of concrete at the junctions, leading to cracks and consequent water leakage

Sacrificial Piles as Scour Countermeasures in River Bridges A Numerical Study using FLOW-3D

Scour is defined as the erosive action of flowing water, as well as the excavating and carrying away materials from beds and banks of streams, and from the vicinity of bridge foundations, which is one of the main causes of river bridge failures. In the present study, implementing a numerical approach, and using the FLOW-3D model that works based on the finite volume method (FVM), the applicability of using sacrificial piles in different configurations in front of a bridge pier as countermeasures against scouring is investigated. In this regard, the numerical model was calibrated based on an experimental study on scouring around an unprotected circular river bridge pier. In simulations, the bridge pier and sacrificial piles were circular, and the riverbed was sandy. In all scenarios, the flow rate was constant and equal to 45 L/s. Furthermore, one to five sacrificial piles were placed in front of the pier in different locations for each scenario. Implementation of the sacrificial piles proved to be effective in substantially reducing the scour depths. The results showed that although scouring occurred in the entire area around the pier, the maximum and minimum scour depths were observed on the sides (using three sacrificial piles located upstream, at three and five times the pier diameter) and in the back (using five sacrificial piles located upstream, at four, six, and eight times the pier diameter) of the pier. Moreover, among scenarios where single piles were installed in front of the pier, installing them at a distance of five times the pier diameter was more effective in reducing scour depths. For other scenarios, in which three piles and five piles were installed, distances of six and four times the pier diameter for the three piles scenario, and four, six, and eight times the pier diameter for the five piles scenario were most effective

Distributed Voltage and Current Control of Multi-Terminal High-Voltage Direct Current Transmission Systems

High-voltage direct current (HVDC) is a commonly used technology for long-distance power transmission, due to its low resistive losses and low costs. In this paper, a novel distributed controller for multi-terminal HVDC (MTDC) systems is proposed. Under certain conditions on the controller gains, it is shown to stabilize the MTDC system. The controller is shown to always keep the voltages close to the nominal voltage, while assuring that the injected power is shared fairly among the converters. The theoretical results are validated by simulations, where the affect of communication time-delays is also studied

ローラーを用いた新型コンパクト同調マスダンパーの開発

学位の種別: 課程博士審査委員会委員 : （主査）東京大学教授 目黒 公郎, 東京大学教授 中埜 良昭, 東京大学教授 本田 利器, 東京大学准教授 長井 宏平, 東京大学講師 沼田 宗純University of Tokyo(東京大学

Effect of Overburden Height on Hydraulic Fracturing of Concrete-Lined Pressure Tunnels Excavated in Intact Rock: A Numerical Study

: This study investigated the impact of overburden height on the hydraulic fracturing of a concrete-lined pressure tunnel, excavated in intact rock, under steady-state and transient-state conditions. Moreover, the Norwegian design criterion that only suggests increasing the overburden height as a countermeasure against hydraulic fracturing was evaluated. The Mohr–Coulomb failure criterion was implemented to investigate failure in the rock elements adjacent to the lining. A pressure tunnel with an inner diameter of 3.6 m was modeled in Abaqus Finite Element Analysis (FEA), using the finite element method (FEM). It was assumed that transient pressures occur inside the tunnel due to control gate closure in a hydroelectric power plant, downstream of the tunnel, in three different closure modes: fast (14 s), normal (18 s), and slow (26 s). For steady-state conditions, the results indicated that resistance to the fracturing of the rock increased with increasing the rock friction angle, as well as the overburden height. However, the influence of the friction angle on the resistance to rock fracture was much larger than that of the overburden height. For transient-state conditions, the results showed that, in fast, normal, and slow control gate closure modes, the required overburden heights to failure were respectively 1.07, 0.8, and 0.67 times the static head of water in the tunnel under a steady-state condition. It was concluded that increasing the height of overburden should not be the absolute solution to prevent hydraulic fracturing in pressure tunnels

Water on Mars—A Literature Review

To assess Mars’ potential for both harboring life and providing useable resources for future human exploration, it is of paramount importance to comprehend the water situation on the planet. Therefore, studies have been conducted to determine any evidence of past or present water existence on Mars. While the presence of abundant water on Mars very early in its history is widely accepted, on its modern form, only a fraction of this water can be found, as either ice or locked into the structure of Mars’ plentiful water-rich materials. Water on the planet is evaluated through various evidence such as rocks and minerals, Martian achondrites, low volume transient briny outflows (e.g., dune flows, reactivated gullies, slope streaks, etc.), diurnal shallow soil moisture (e.g., measurements by Curiosity and Phoenix Lander), geomorphic representation (possibly from lakes and river valleys), and groundwater, along with further evidence obtained by probe and rover discoveries. One of the most significant lines of evidence is for an ancient streambed in Gale Crater, implying ancient amounts of “vigorous” water on Mars. Long ago, hospitable conditions for microbial life existed on the surface of Mars, as it was likely periodically wet. However, its current dry surface makes it almost impossible as an appropriate environment for living organisms; therefore, scientists have recognized the planet’s subsurface environments as the best potential locations for exploring life on Mars. As a result, modern research has aimed towards discovering underground water, leading to the discovery of a large amount of underground ice in 2016 by NASA, and a subglacial lake in 2018 by Italian scientists. Nevertheless, the presence of life in Mars’ history is still an open question. In this unifying context, the current review summarizes results from a wide variety of studies and reports related to the history of water on Mars, as well as any related discussions on the possibility of living organism existence on the planet

Impact of feature harmonization on radiogenomics analysis:Prediction of EGFR and KRAS mutations from non-small cell lung cancer PET/CT images

Objective: To investigate the impact of harmonization on the performance of CT, PET, and fused PET/CT radiomic features toward the prediction of mutations status, for epidermal growth factor receptor (EGFR) and Kirsten rat sarcoma viral oncogene (KRAS) genes in non-small cell lung cancer (NSCLC) patients. Methods: Radiomic features were extracted from tumors delineated on CT, PET, and wavelet fused PET/CT images obtained from 136 histologically proven NSCLC patients. Univariate and multivariate predictive models were developed using radiomic features before and after ComBat harmonization to predict EGFR and KRAS mutation statuses. Multivariate models were built using minimum redundancy maximum relevance feature selection and random forest classifier. We utilized 70/30% splitting patient datasets for training/testing, respectively, and repeated the procedure 10 times. The area under the receiver operator characteristic curve (AUC), accuracy, sensitivity, and specificity were used to assess model performance. The performance of the models (univariate and multivariate), before and after ComBat harmonization was compared using statistical analyses. Results: While the performance of most features in univariate modeling was significantly improved for EGFR prediction, most features did not show any significant difference in performance after harmonization in KRAS prediction. Average AUCs of all multivariate predictive models for both EGFR and KRAS were significantly improved (q-value &lt; 0.05) following ComBat harmonization. The mean ranges of AUCs increased following harmonization from 0.87-0.90 to 0.92-0.94 for EGFR, and from 0.85-0.90 to 0.91-0.94 for KRAS. The highest performance was achieved by harmonized F_R0.66_W0.75 model with AUC of 0.94, and 0.93 for EGFR and KRAS, respectively. Conclusion: Our results demonstrated that regarding univariate modelling, while ComBat harmonization had generally a better impact on features for EGFR compared to KRAS status prediction, its effect is feature-dependent. Hence, no systematic effect was observed. Regarding the multivariate models, ComBat harmonization significantly improved the performance of all radiomics models toward more successful prediction of EGFR and KRAS mutation statuses in lung cancer patients. Thus, by eliminating the batch effect in multi-centric radiomic feature sets, harmonization is a promising tool for developing robust and reproducible radiomics using vast and variant datasets.</p

Comparison of Ultrasound-Guided Local Dexmedetomidine Injection vs. Corticosteroid Injection in the Treatment of Chronic Plantar Fasciitis: A Randomized Clinical Trial

Background: Heel pain is commonly caused by chronic plantar fasciitis, associated with pain and activity limitation in patients. Although steroid injection is a popular method to treat this disease, it has side effects and provides short-term pain relief. The study was designed to investigate the effects of dexmedetomidine and corticosteroid injection in treating chronic plantar fasciitis. Materials and Methods: A total of 70 participants were divided into two groups. The intervention group received a mixture of dexmedetomidine (1μg/kg) with 1 ml of lidocaine 2%. The control group received a combination of 1ml of corticosteroid (40mg triamcinolone) with 1ml of lidocaine 2%. Outcome measures were evaluated with Numerical Rating Scale (NRS) and Maryland foot score (MFS) before, one, and three months after the intervention. Results: Significant improvements in NRS and MFS were observed in both groups at 1 and 3 months of follow-up compared to baseline(P<0.001). NRS score improvement in the first month was more significant in the corticosteroid group compared to the dexmedetomidine group. However, after three months, the dexmedetomidine group experienced greater pain reduction (P=0.012) and higher functional ability (P<0.001) than the corticosteroid group. Conclusion: Local injection of dexmedetomidine provided significant and long-term effects on pain severity and physical activity. Corticosteroids caused an immediate but short‑term effect, whereas sustained improvement in the dexmedetomidine group was observed during the follow-up

Analyzing the Impact of COVID-19 Pandemic on Different Educational Aspects of Surgical Specialties’ Residency Program: A Preliminary Report

Introduction: The lifestyle and learning of trainees from different surgical specialties have been severely affected by the COVID-19 pandemic. Despite the growing body of research, the extent to which their surgical or educational performance is affected is not yet well-understood. We investigated the Iranian multi-specialty surgical residents nationwide to clarify the extent this new pandemic’s has affected their surgical and educational activities. Material and Methods: Our specialized board designed a questionnaire which was sent to residents from the 18th of May to 12th of Jun 2020. The questionnaire comprised demographic data, questions on the clinical, surgical, and educational activities during and before the pandemic. Results: Out of 700 eligible residents, 543 (77%) submitted their answers to all questions. 417 (76.8%) of the respondents declared they had spent their residency program at a hospital that was the main referral center for patients with COVID-19 infection. The weekly number of the outpatient and emergent visits decreased by one third (P&lt;0.001) and one-half (P&lt;0.001), respectively, following the pandemic. Also, the amount of surgeries has dramatically decreased (P&lt;0.001). The median weekly hours devoted to face-to-face activities decreased, while the study time increased and the share of virtual education has a five-fold increase (P&lt;0.001). Conclusion: This pandemic had a significant impact on many aspects of training in surgical specialties’ residency program in Iran. Increasing the time available to study is an opportunity, and online education, despite its challenges, has been effective