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Risk Assessment of Vertical Breakwaters -A Case Study in Turkey

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China Ocean engineering 2002年第1期17卷 123-134页

作者： CanElmarBALAS LeventKOC civil engineering Department Faculty of Engineering and ArchitectureGazi UniversityCivil Engineering DepartmentFaculty of Engineering and ArchitectureGazi University 06570 AnkaraTurkey06570 AnkaraTurkey

In the reliability-risk assessment, the second order reliability index (βⅡ ) method and the Conditional Expectation Monte Carlo (CEMC) simulation are interrelated as a new Level Ⅲ approach for the analysis of the safety level of the Dalaman yacht harbor vertical wall breakwater in Turkey. The missing wave data of the Dalaman measurement station are hindcasted by use of multi-layer feed-forward neural networks with the steepest descent and conjugate gradient algorithms. The structural failure probabilities of sliding and overturning failure modes are forecasted by approximation of the failure sur-face with a second-degree polynomial of an equal curvature at the design point. in the new approach, for each randomly generated load and tide combination, the joint failure probability reflects both the occurrence probability of loading condition and the structural failure risk at the limit state. The approach can be applied to risk assessment of vertical breakwaters in short CPU durations of portable computers.

关键词： vertieal breakwater simulation stability neural network reliability

Applications of A Numerical Model to Wave Propagation on Mild Slopes

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China Ocean engineering 2002年第4期17卷 569-576页

作者： Asu INAN Lale BALAS civil engineering Department Faculty of Engineering and Architecture Gazi University 06570 Ankara Turkey Civil Engineering Department Faculty of Engineering and Architecture Gazi University 06570 Ankara Turkey

Based on the mild slope equation that has heen deeomposed inlo three equations related to wave phase function, wave amplitude and wave approach angle, a refraction-diffraction model is developed. The finite difference method has been selected as the solution method. The model results are compared with experimental results and the model is applied to coastal waters of the Fethiye Bay, whieh is located at the Mediterranean Sea of Turkey.

关键词： numerical model wave propagation mild slope refraction-difjraction

The influence of environmental factors on the carbon dioxide flux across the water–air interface of reservoirs in south-eastern Poland

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Journal of Environmental Sciences 2017年第6期29卷 290-299页

作者： Renata Gruca-Rokosz Lilianna Bartoszek Piotr Koszelnik faculty of civil and Environmental engineering and architecture Rzeszdw University of TechnologyRzeszowPoland

Studies concerning the emission of carbon dioxide （CO2） were carried out in 2009-2012 for six reservoirs located in four provinces of south-eastern Poland. The CO2 flux across the water-air interface was measured using the ＂static chamber＂ method. The measured fluxes of CO2 （FCO2） ranged from -30.64 to 183.78 mmol/m2/day, and the average values varied in the range from -3.52 to 82.11 mmol/m2/day. In most of the cases, emission of CO2 to the atmosphere was observed. The obtained values of CO2 fluxes were comparable to values typical for other temperate reservoirs. Analysis of the influence of selected envi- ronmental factors on the FCO2 showed that it depends on parameters characterizing both the sediments and surface water. The CO2 flux at the water-air interface was positively correlated with parameters of bottom sediments such as porosity, content of organic carbon and total nitrogen; and negatively with pH value and 51℃ of organic carbon. In the case of the parameters characterizing surface water, positive dependences on the concen- trations of nitrate and total nitrogen, and negative relationships with water temperature and chlorophyll a concentrations, were found.

关键词： Carbon dioxideGreenhouse gasesReservoirSediment

Evaluation of Stress Intensity Factors for Multiple Cracked Circular Disks Under Crack Surface Tractions with SBFEM

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China Ocean engineering 2013年第3期27卷 417-426页

作者：刘钧玉林皋李晓川徐凤琳 faculty of Infrastructure engineering Dalian University of Technology School of architecture & civil engineering Shenyang University of Technology

Stress intensity factors （SIFs） for the cracked circular disks under different distributing surface tractions are evaluated with the scaled boundary finite element method （SBFEM）. In the SBFEM, the analytical advantage of the solution in the radial direction allows SIFs to be directly determined from its definition, therefore no special crack-tip treatment is necessary. Furthermore anisotropic material behavior can be treated easily. Different distributions of surface tractions are considered for the center and double-edge-cracked disks. The benchmark examples are modeled and an excellent agreement between the results in the present study and those in published literature is found. It shows that SBFEM is effective and possesses high accuracy. The SIFs of the cracked orthotropic material circular disks subjected to different surface tractions are also evaluated. The technique of substructure is applied to handle the multiple cracks problem.

关键词： stress intensity factors scaled boundary finite element method circular disk orthotropic material surfacetraction

Optimal slag content for geopolymer composites under freeze-thaw cycles with different freezing temperatures

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Journal of Zhejiang University-Science A(Applied Physics & engineering) 2023年第4期24卷 366-376页

作者： Lifeng FAN Weiliang ZHONG Guang WANG Yan XI faculty of architecture Civil and Transportation EngineeringBeijing University of TechnologyBeijing 100124China

Improving the freeze-thaw resistance of geopolymers is of great significance to ensure their durability in cold regions. This study presents an experimental investigation of optimal slag content for geopolymer composites under freeze-thaw cycles with different freezing temperatures. Firstly, five kinds of geopolymer composites with 10.0%, 20.0%, 30.0%, 40.0%,and 50.0% slag contents and 1.0% fiber content were prepared. Freeze-thaw cycle tests at-1.0 ℃,-20.0 ℃, and-40.0 ℃ were carried out for these geopolymer composites and their physical and mechanical properties after the freeze-thaw cycle were tested. The results show that the porosity of the geopolymer composites decreases as the slag content increases. Their mass loss ratio and strength loss ratio increase gradually as the freezing temperature decreases. The mass loss ratio and strength loss ratio of geopolymer composites after freeze-thaw cycles all decrease as the slag content increases. Considering the physical and mechanical properties of geopolymers after freeze-thaw cycles, the optimal slag contents are 40.0% and 50.0%.

关键词： Geopolymer composites Freeze-thaw cycle Freezing temperature Slag content

Effects of combined antibiotics on nitrification, bacteria and antibiotic resistance genes in activated sludge: Insights from legacy effect of antibiotics

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Journal of Environmental Sciences 2023年第9期131卷 96-110页

作者： Zhong-Xing Zhang Xiao-Yan Fan Xing Li Yu-Xi Gao Jun-Ru Zhao faculty of architecture Civil and Transportation EngineeringBeijing University of TechnologyBeijing 100124China

The effect of combined antibiotics exposure on nitrogen removal,microbial community assembly and proliferation of antibiotics resistance genes(ARGs)is a hotspot in activated sludge ***,it is unclear that how the historical antibiotic stress affects the subsequent responses of microbes and ARGs to combined *** this study,the effects of combined sulfamethoxazole(SMX)and trimethoprim(TMP)pollution on activated sludge under legacy of SMX or TMP stress with different doses(0.005-30 mg/L)were investigated to clarify antibiotic legacy *** activity was inhibited under higher level of combined exposure but a high total nitrogen removal(∼70%)*** on the full-scale classification,the legacy effect of past antibiotic stress had a marked effect on community composition of conditionally abundant taxa(CAT)and conditionally rare or abundant taxa(CRAT).Rare taxa(RT)were the keystone taxa in the microbial network,and the responses of hub genera were also affected by the legacy of antibiotic *** bacteria and genes were inhibited by the antibiotics and aerobic denitrifying bacteria(Pseudomonas,Thaurea and Hydrogenophaga)were enriched under legacy of high dose,as were the key denitrifying genes(napA,nirK and norB).Furthermore,the occurrences and co-selection relationship of 94 ARGs were affected by legacy ***,some shared hosts(eg.,Citrobacter)and hub ARGs(eg.,mdtD,mdtE and acrD)were ***,antibiotic legacy could affect responses of activated sludge to combined antibiotic and the legacy effect was stronger at higher exposure levels.

关键词： Antibiotics Antibiotic resistance genes(ARGs) Combined pollution Full-scale classification Legacy effect

Decontamination of Cr(Ⅵ) from water using sewage sludge-derived biochar: Role of environmentally persistent free radicals

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Chinese Journal of Chemical engineering 2023年第4期56卷 97-103页

作者： Yuhan Zhu Jia Wei Jun Li faculty of architecture Civil and Transportation EngineeringBeijing University of TechnologyBeijing 100124China

Biochar is a well-known material for pollutant removal owing to its low cost and rich surface functionality. A kind of highly active substance, called environmentally persistent free radicals(EPFRs), can be produced in the preparation process of biochar, playing an important role in the removal of *** this study, sludge-derived biochars(SBC_(120) and SBC_(270)) were prepared by the hydrothermal carbonization under two temperatures(120℃ and 270℃) to investigate their removal abilities of Cr(Ⅵ). The maximum removal amounts of Cr(Ⅵ) by SBC_(120) and SBC_(270) were 16.58 and 22.93 mg·g^(-1), respectively. It was further revealed that the appearance of Cr(Ⅲ), as a result of EPFRs on sludge-derived biochar(SBC) transferred electrons to Cr(Ⅵ) in neutral solutions. That is to say, oxygen-centered(O-centered) EPFRs on SBC_(120) and carbon-centered(C-centered) EPFRs on SBC_(270) all could be used as electron donors to Cr(Ⅵ) to make it become Cr(Ⅲ). This study not only provides a theoretical basis for the mechanism of pollutants removal by sludge-derived biochar but also offers a new perspective on the direct effect of EPFRs on pollutants.

关键词： Sludge-derived biochar Environmentally persistent free radicals Chromium Removal Reduction

In-depth understanding of transport behavior of sulfided nano zerovalent iron/reduced graphene oxide@guar gum slurry: Stability and mobility

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Journal of Environmental Sciences 2024年第10期144卷 1-14页

作者： Yuheng Ma Wenhui You Zijiang Yang Zhongyu Ren Qi Jing faculty of architecture Civil and Transportation EngineeringBeijing University of TechnologyBeijing 100124China

Nanoscale zero-valent iron(NZVI),which has the advantages of small particle size,large specific surface area,and high reactivity,is often injected into contaminated aquifers in the form of ***,the prone to passivation and agglomeration as well as poor stability andmobility of NZVI limit the further application of this technology in ***,sulfided NZVI loaded on reduced graphene oxide(S-NZVI/rGO)and guar gum(GG)with shearthinning properties as stabilizers were used to synthesize S-NZVI/rGO@GG ***,TEM,and FT-IR confirmed that the dispersion and anti-passivation of NZVI were optimized in the coupled *** stability and mobility of the slurry were improved by increasing the GG concentration,enhancing the pH,and decreasing the ionic strength and the presence of Ca^(2+)ions,respectively.A modified advection-dispersion equation(ADE)was used to simulate the transport experiments considering the strain and physicochemical deposition/***,colloidal filtration theory(CFT)demonstrated that Brownian motion plays a dominant role in themigration of S-NZVI/rGO@GG slurry,and the maximummigration distance can be increased by appropriately increasing the injection ***-Derjaguin-Landau-Verwey-Overbeek(XDLVO)theory showed that the excellent stability and migration of S-NZVI/rGO@GG slurry mainly came from the GG spatial *** study has important implications for the field injection of S-NZVI/rGO@GG *** to the injection parameters,the injection range of S-NZVI/rGO@GG slurry is effectively controlled,which lays the foundation for the promotion of application in actual fields.

关键词： S-NZVI rGO Guar gum Transport Stability

Structural Model Updating of Jacket Platform by Control Theory Using Vibration Measurement Approach

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China Ocean engineering 2021年第1期35卷 96-106页

作者： Farhad HOSSEINLOU faculty of civil engineering and architecture Shahid Chamran University of AhvazAhvaz 61357Iran

The identification of variations in the dynamic behavior of structures is an important subject in structural integrity *** and servicing of offshore platforms in the marine environment with constant changing,requires understanding the real behavior of these structures to prevent possible *** this work,empirical and numerical models of jacket structure are investigated.A test on experimental modal analysis is accomplished to acquire the response of structure and a mathematical model of the jacket structure is also ***,based on the control theory using developed reduction system,the matrices of the platform model is calibrated and *** current methodology can be applied to prepare the finite element model to be more adaptable to the empirical *** results with the proposed approach in this paper are very close to those of the actual model and also this technique leads to a reduction in the amount of calculations and *** research clearly confirms that the dynamic behavior of fixed marine structures should be designed and assessed considering the calibrated analytical models for the safety of these structures.

关键词： offshore platform calibrated model control theory vibration test reduction model