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Propulsion Performance of Spanwise Flexible Wing Using Unsteady Panel Method

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Journal of Ocean University of China 2020年第3期19卷 505-518页

作者： najafi saeed LIU Pengfei Ocean Engineering and Technology Department Iranian National Institute for Oceanography(INIO)Tehran ***Iran Marine Offshore and Subsea TechnologySchool of EngineeringNewcastle UniversityNewcastle upon TyneNE17RUUK

In this paper, the propulsion performance of a spanwise flexible oscillating wing, which is broadly similar to the undulation of a fin fluke, is investigated. The geometry of the fluke underwent three prescribed harmonic oscillating motions simultaneously while surging with constant velocity. The effect of deflection phase angle, flexibility parameter, and wing tip deflection amplitude on thrust coefficient and swimming efficiency was studied. A low-order unsteady panel method coupled with a time stepping algorithm for free wake alignment is implemented in a computer program to estimate the propulsion efficiency of lifting bodies. A novel approach is introduced to evaluate the singular integrals of line vortices by using an adaptive mollifier function. This method is an efficient way to accelerate computational speed by reducing the order of problem from R^3 to body boundaries. Results present the significant effect of phase angle on the propulsion characteristics of oscillating fluke.

关键词： propulsion performance fin whale fluke flexible wing panel method wake alignment

Sediment contribution from different geologic formations and land uses in an Iranian small watershed,case study

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International Journal of Sediment Research 2017年第2期32卷 210-220页

作者： Seyed Hamidreza Sadeghi saeed najafi Alireza Riyahi Bakhtiari Department of Watershed Management Engineering Faculty of Natural ResourcesTarbiat Modares University Department of Environmental Sciences Faculty of Natural ResourceTarbiat Modares University

Many intra and extra problems occurred due to unsustainable human use of natural resources leading to increasing sediment loads in the ***,few studies have been comprehensively conducted in progressing countries to prioritize sediment sources from different points of views,particularly in some countries like Iran where such valuable information is essential for proper watershed resources *** present study was therefore planned to assess the importance of potential sediment sources viz.,spatial sources(geologic units) and source types(land use units) in sediment yield in Idelo watershed as one of the important sub-watersheds of Sefidrood large Watershed in Zanjan Province,Iran,using composite *** addition,the results of the sediment fingerprinting approach were compared with those of field measurement data obtained from studying soil erosion types(viz.,sheet,rill and gully erosion).Toward this attempt,16 tracers were detected in different geologic units and land uses and the sediment yielded at the watershed *** results showed that the composite fingerprints of the different geologic units comprising As,N,Cu,Zn,OC and Co tracers could correctly distinguish 86% of the sediment source *** red gypsiferous marl contributed 85 percent in sediment *** regard to source types,the optimum composite fingerprint encompassed only N and Cu and provided a discriminatory efficiency of 90%.Besides that,the rangelands with 48.8% study area coverage had a significant contribution of 88% in sediment *** field measurements confirmed the reliability of results of fingerprinting approach in apportioning watershed scale sediment sources on the base of consistency of the two sets of *** was also understood from the results,besides successful applicability of composite fingerprinting in assessing the provenance of the sediment yielded at the watershed outlet that the geologic formations and land use types played differe

关键词： Composite fingerprinting Multivariate mixing model Soil erosion Spatial sources Source types

Investigating the Performance of Twin Marine Propellers in Different Ship Wake Fields Using an Unsteady Viscous and Inviscid Solver

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Journal of Marine Science and Application 2022年第2期21卷 92-105页

作者： saeed najafi Mehdi Pourmostafa Iranian National Institute for Oceanography and Atmospheric Science(INIOAS) Fatemi Ave.14155-4781 TehranIran Department of Maritime Engineering Amirkabir University of TechnologyHafez Ave.15875-4413 TehranIran

In this study,the performance of a twin-screw propeller under the influence of the wake field of a fully appended ship was investigated using a coupled Reynolds-averaged Navier–Stokes(RANS)/boundary element method(BEM)*** unsteady BEM is an efficient approach to predicting propeller *** applying the time-stepping method in the BEM solver,the trailing vortex sheet pattern of the propeller can be accurately captured at each time *** is the main innovation of the coupled ***,to ascertain the effect of the wake field of the ship with acceptable accuracy,a RANS solver was developed.A finite volume method was used to discretize the Navier–Stokes equations on fully unstructured *** simulate ship motions,the volume of the fluid method was applied to the RANS *** validation of each solver(BEM/RANS)was separately performed,and the results were compared with experimental ***,the BEM and RANS solvers were coupled to estimate the performance of a twin-screw propeller,which was affected by the wake field of the fully appended *** proposed model was applied to a twin-screw oceanography research *** results demonstrated that the presented model can estimate the thrust coefficient of a propeller with good accuracy as compared to an experimental self-propulsion *** wake sheet pattern of the propeller in open water(uniform flow)was also compared with the propeller in a real wake field.

关键词： Twin propeller Reynolds-averaged Navier-Stokes(RANS) Boundary element method(BEM) Time-stepping method(TSM) Wake sheet pattern Effective wake field

Color and Gloss Changes of a Lignin-Based Polyurethane Coating under Accelerated Weathering

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Journal of Renewable Materials 2024年第2期12卷 305-323页

作者： Fatemeh Hassani Khorshidi saeed Kazemi najafi Farhood najafi Antonio Pizzi Dick Sandberg Rabi Behrooz Department of Wood Science and Technology Faculty of Natural ResourcesTarbiat Modares UniversityTehranIran Department of Resin and Additives Institute for Color Science and TechnologyP.O.Box 16765-654TehranIran LERMAB University of LorraineBlvd des AiguillettesNancy54000France Wood Science and Engineering LuleåUniversity of TechnologySkellefteåSweden

The purpose of this research study was to investigate the properties of polyurethane coatings based on lignin *** this purpose,the prepared coatings were applied to pine wood surfaces and weathered ***,color and gloss of the coatings were measured before and after the weathering *** emission scanning electron microscopy(FE-SEM)micrographs prepared from the coatings showed that the average size of nano-particles in the polyurethane substrate was approximately 500 *** magnetic resonance(13C-NMR)spectroscopy showed that strong urethane bonds were formed in the nano-lignin-based *** calorimetric analysis(DSC)test revealed that the glass-transition temperature(Tg)of lignin nanoparticles modified with diethylenetriamine(DETA)was 112.8℃ and Tg of lignin nano-particles modified with ethylenediamine(EDA)was 102.5℃,which is lower than the Tg of un-modified lignin(114.6℃)and lignin modified with DETA(126.8℃)and lignin modified with EDA(131.3℃).The coatings modified with lignin nano-particles had a greater change in *** lignin nano-particles in the modified coating are trapping hydroxyl radicals which reduces photoactivity and yellowing of the polyurethane by about 3 times compared to unmodified polyurethane *** weathering test,the nano-lignin-based coating had a rougher surface with a lower contact angle(0.78°)compared to the unmodified polyurethane coating(0.85°).

关键词： Amination propylene carbonate lignin biopolymer polyurethane coating polyol UN SDG 13

Evaluating innovation ecosystem resiliency using agent-based modeling and systems dynamics

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Journal of Safety Science and Resilience 2024年第2期5卷 204-221页

作者： Soheila Abdi Mehdi Yazdani Esmaeil najafi Department of Industrial Engineering Science and Research BranchIslamic Azad UniversityTehranIran Department of Industrial Engineering Qazvin BranchIslamic Azad UniversityQazvinIran

Evaluating the resilience of the innovation ecosystem to maintain its performance,in the sense of resistance to disruption and recovery after it,has recently received more *** studies have been conducted to model different ecosystems and evaluate their ***,modeling the innovation ecosystem from a holistic perspective and performing a quantitative assessment of its resilience have received less *** paper models the innovation ecosystem holistically and evaluates its resilience index using a quantitative approach through five main *** the first step,a case study related to the innovation ecosystem of Iran's Ministry of Energy,called the Power Innovation Ecosystem,is modeled by combining system dynamics and agent-based *** validating the model in the second step,the disruption of the loss of experts is investigated in the third step,and all possible actions to recover each actor are *** the fourth step,the performance of the ecosystem is simulated before and after the disruption using the data gathered in the previous ***,resilience is calculated in two different ways in the fifth *** improvement solutions are also suggested when considering that the resilience index of the innovation ecosystem is at a medium *** research may assist policymakers in observing the resilience level of the innovation ecosystem based on the proposed *** applying strategic changes to this model,they can determine the effects of their policies and make the most appropriate decisions to increase the resilience of the innovation ecosystem.

关键词： Resilience index innovation ecosystem System dynamics Agent-based modeling

Isoimperatorin alleviates acetic acid-induced colitis in rats

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Asian Pacific Journal of Tropical Biomedicine 2024年第4期14卷 147-153页

作者： Saied Goodarzi Amir Hossein Abdolghaffari Behnaz najafi Mostafa Pirali Hamedani saeed Tavakoli Mahshad Marvi Maryam Baeeri Narguess Yassa Abbas Hadjiakhoondi Mohammad Abdollahi Zahra Tofighi Medicinal Plants Research Center Faculty of PharmacyTehran University of Medical SciencesTehranIran Department of Toxicology and Pharmacology Faculty of PharmacyTehran Medical SciencesIslamic Azad UniversityTehranIran Department of Pharmacognosy Faculty of PharmacyTehran University of Medical SciencesTehranIran Medicinal Plants Research Center Institute of Medicinal PlantsACECRKarajIran International Campus School of Pharmacy Tehran University of Medical SciencesTehranIran Toxicology and Diseases group The Pharmaceutical Sciences Research CenterTehran University of Medical SciencesTehranIran Department of Toxicology and Pharmacology Faculty of PharmacyTehran University of Medical SciencesTehranIran

Objective:To investigate the effect of isoimperatorin on histopathological and biochemical changes in acetic acid-induced colitis ***:Colitis was induced by intracolonic administration of acetic acid solution(4%v/v)in *** were divided into six groups including the sham group,the negative control group,the dexamethasone-treated group,and the groups treated with isoimperatorin(0.1,1,and 10 mg/kg/d by gavage).The treatments were administered for three days and then colonic status was assessed by macroscopic,histopathological,and biochemical ***:Isoimperatorin significantly alleviated colonic damage in a dose-dependent manner and improved histological changes in rats with acetic acid-induced *** also significantly reduced myeloperoxidase,TNF-α,IL-1β,and malodialdehyde ***:Isoimperatorin alleviates acetic acid-induced colitis in rats and may be a potential therapeutic agent for the treatment of colitis.

关键词： Isoimperatorin Inflammatory bowel disease Acetic acid Colitis TNF-α IL-1β

A thermo-mechanical simulation for the stability analysis of a horizontal wellbore in underground coal gasification

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Petroleum 2024年第2期10卷 243-253页

作者： Mohammadreza Shahbazi Mehdi najafi Mohammad Fatehi Marji Ramin Rafiee Department of Mining and Metallurgical Eng. Yazd UniversityYazdIran Department of Mining Petroleum&Geophysics Eng.Shahrood University of TechnologyShahroodIran

The stability analysis of horizontal wells is essential for a successful underground coal gasification(UCG)*** this paper,a new 3D coupled thermo-mechanical numerical modeling is proposed for analyzing the stability of UCG horizontal *** this model,the effect of front abutment stresses,syngas pressure,syngas temperature and thermal stresses is considered to predict the mud weight window and drilling mud pressure during UCG *** results show that the roof caving in UCG panel has a greatest impact on the stability of horizontal ***,when the time of coal gasification is increased,the well convergence increases and for more stability it is necessary to increase the drilling mud *** research was carried out on the M2 coal seam in Mazino coal deposit(Iran).The results showed that the mud weight window for horizontal well drilling is between 0 and 33 *** appropriate stress for the maximum stability of the horizontal well,taking all the thermal and mechanical parameters into account,is 28 *** suggested numerical method is a comprehensive and consistent way for analyzing the stability of horizontal wells in UCG sites.

关键词： Underground coal gasification Thermo-mechanical simulation Numerical modeling Stress distribution Horizontal well

Examining the Effect of Hydroalcoholic Extract of Dracaena cinnabari on Sex Hormones and Ovarian and Uterine Tissues of Rats

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World Journal of Traditional Chinese Medicine 2024年第2期10卷 213-219页

作者： Elham najafi Bahareh Babaei Hoolari Akbar Karimi Aliasghar Pilehvarian Department of Cellular Biology Genesis Evolution-Develoment Isfahan Payame Noor University IsfahanIran Department of Anatomy School of MedicineTehran University of Medical SciencesTehranIran Department of Biology Group Faculty Member of Isfahan Payame Noor UniversityIsfahanIran

Introduction: Dracaena cinnabari is considered a rich source of phytochemicals used widely in traditional medicine. In the present study, the effect of D. cinnabari hydraulic extract on the reproductive system of female rats was investigated. Methods: The samples were randomly divided into four groups(six samples in each group), including three treatment groups and one control group, and all samples were kept at the same conditions. Hydraulic extract of D. cinnabari and injected intraperitoneally daily for 10 days, while physiological serum was used for injection in to the control group. After 10 days of injection, estrogen and progesterone levels were measured by enzyme immunoassay technique. After dissection, the ovaries and uterine tissues were isolated for histological examination, and tissue changes were carefully examined. Results: The results revealed that the levels of estrogen and progesterone in experimental Groups 2 and 3 had a significant increase(P < 0.001). Regarding tissue changes, a significant increase was observed in epithelial thickness(P < 0.001), number of corpus luteum(P < 0.01), and Graafian follicle(P < 0.01) in doses of 100 and 150 mg/kg. Conclusions: Based on the results, it seems that D. cinnabari extract has an effect on the ovarian follicles.

关键词： Dracaena cinnabari herbal medicine ovarian tissues reproductive sex hormones

Forest Road Detection Using LiDAR Data

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Journal of Forestry Research 2014年第4期25卷 975-980页

作者： Zahra Azizi Akbar najafi saeed Sadeghian Faculty of Natural Resources Tarbiat Modares University P.O. Box:46414–356 Noor IRAN Geomatics College of National Cartographic Center P.O. BOX: 13185-1684 Tehran IRAN

We developed a three-step classification approach for forest road extraction utilizing LiDAR data. The first step employed the IDW method to interpolate LiDAR point data （first and last pulses） to achieve DSM, DTM and DNTM layers （at 1 m resolution）. For this interpolation RMSE was 0.19 m. In the second step, the Support Vector Machine （SVM） was employed to classify the LiDAR data into two classes, road and non-road. For this classification, SVM indicated the merged distance layer with intensity data and yielded better identification of the road position. Assessments of the obtained results showed 63% correctness, 75% completeness and 52% quality of classification. In the next step, road edges were defined in the LiDAR-extracted layers, enabling accu- rate digitizing of the centerline location. More than 95% of the Li- DAR-derived road was digitized within 1.3 m to the field surveyed nor- rnal. The proposed approach can provide thorough and accurate road inventory data to support forest management.

关键词： forest road LiDAR SVM IDW method