Vibration analysis of damaged and undamaged steel structure systems: cantilever column and frame     

Khan  Muhammad Abuzar  Akhtar  Kareem  Ahmad  Naveed  Shah  Feroz  Khattak  Naeem 《地震工程与工程振动(英文版)》2020,19(3):725-737

This paper presents the experimental and numerical studies conducted on a steel column and a steel frame structure using free vibration analysis. The effects of damages on structures were investigated, which were simulated by introducing multiple cracks at different locations in the experimental and numerical models. The acceleration responses of the test models, were recorded through an accelerometer, and were used to calibrate the numerical models developed in finite element based software. Modal frequencies of damaged and undamaged structures were compared and analyzed, to derive relationships for damaged and undamaged structures' frequencies in terms of crack depth. It was found that, due to the presence of cracks, the mechanical properties of a structure changes, whereby, the modal frequencies decrease. An approximately linear trend was observed for the frequency decrease with the increase in crack depth, which was also confirmed by the numerical models. The derived relationships were extended to further develop a mechanics-based damage scale for steel structures, to help facilitate structural health monitoring and screening of vulnerable structures.  相似文献   

Thermal structure of hot events and their possible role in maintaining the warm isothermal layer in the Western Pacific warm pool     

Wirasatriya  Anindya  Kawamura  Hiroshi  Helmi  Muhammad  Sugianto  Denny Nugroho  Shimada  Teruhisa  Hosoda  Kohtaro  Handoyo  Gentur  Putra  Yoppik Disma Girindra  Koch  Magaly 《Ocean Dynamics》2020,70(6):771-786

Ocean Dynamics - The short-lived events of high SST are called hot events (HEs) and can only be generated under the conditions of large daily heat gain due to strong solar radiation and weak wind....  相似文献   

Green and Eco‐Friendly Removal of Mycotoxins with Organo‐Bentonites; Isothermal,Kinetic, and Thermodynamic Studies     

Muhammad Saeed  Komal Farooq  Muhammad Nafees  Muhammad Arshad  Mohammad Salim Akhter  Amir Waseem 《洁净——土壤、空气、水》2020,48(9)

In the current study the application of organo‐modified bentonite for the adsorption of mycotoxins (aflatoxin B1, citrinin, patulin, and zearalenone) is presented. The modification of clays is carried out using benzyl‐tri‐n‐butyl ammonium bromide (BTB), benzethonium chloride (BTC), and dioctyl sodium sulfosuccinate (DSS). Various experimental parameters such as pH, time, adsorbent dose, and mycotoxins concentration are thoroughly studied. The modified clays (B‐BTB, B‐BTC and B‐DSS) are characterized by X‐ray fluorescence, X‐ray diffraction, and Fourier transform infrared spectroscopy. The results depicted the high detoxification efficiency (≈99%) of modified clays for the removal of mycotoxins under optimized conditions (pH 5, time: 30 min, adsorbent amount: 50 mg). The adsorption capacities of modified clays are found in the order of: B‐BTC (AFB1: 18.02, CIT: 18.35, PAT: 18.21, ZEA: 18.09 mg g^?1) > B‐BTB (AFB1: 17.7, CIT: 18.11, PAT: 17.95, ZEA: 17.90 mg g^?1) > B‐DSS (AFB1: 17.5, CIT: 18.02, PAT: 17.86, ZEA: 17.80 mg g^?1). The obtained results fitted well with thermodynamic, isothermal (Langmuir) and pseudo‐second order kinetics. Low cost organo‐modified bentonite shows the promise in mitigating mycotoxin contamination, which could improve food safety and reduce environmental contamination.  相似文献   

Delineation of seismic zonation using fractal modeling in West Yazd province,Central Iran     

Peyman Afzal  Ahmad Adib  Naser Ebadati 《Journal of Seismology》2018,22(6):1377-1393

This study is an attempt to identify seismic zones utilizing number-size (N-S) and concentration-area (C-A) fractal models in the West Yazd province, Central Iran. The analysis was based on the earthquakes’ magnitude and Quaternary faults’ density. Fault density map was generated and classified by fractal modeling. The result indicates that the main fault densities correlate with Dehshir and Eqlid faults. Furthermore, the areas with relatively large earthquake magnitudes are located in the SE and NE parts of the region. The Quaternary faults’ density and earthquake magnitudes were weighted based on the results of the fractal modeling. Finally, weighted maps were combined and classified to show that Dehshir fault has the main role for seismicity in this area. Comparison between results derived via the fractal modeling and conventional seismic zonation map is satisfactory. Furthermore, fractal modeling approach distinguishes different seismic zones with higher accuracy in smaller areas. For validation of results, earthquakes since 2012 were collected and associated with seismic zones. These earthquakes which are correlated with major seismic zones are mainly located near the Dehshir and main Zagros faults.  相似文献   

高密度电法电性结构揭示天山天池堆积坝体厚度及其阻渗稳水功能分析     

尚彦军  金维浚  伊学涛  姜东廷  HASAN Muhammad 《现代地质》2023,37(1):31-39

天山天池北堆积坝体结构受其成因和演化控制,影响其含水和渗流特性。对该坝体稳定至关重要的下伏基岩埋深、坝体结构阻渗水结构特征等需现场探测并给出科学判断。在地质调查基础上采用高密度电法对天池堆积坝体结构进行探测,首次获得深达下伏基岩的堆积坝体纵向和横向电性剖面。结合光释光测年、水化学成分对比、水量平衡计算等手段,分析坝体堆积物形成时代以及坝体水文地质结构特征。结果显示：天池坝堆积体厚度大于100 m并可分为3层,上部浅表层滑坡形成的巨大块石层厚30～40 m且基本不含水,其下松散含水层厚度为30～50 m;下部为较低电阻率弱透水的冰碛物,主要分布在坝体下游和东端;底部为高电阻率不透水的石炭系火山岩。坝体中间部位地下水集中下渗补给了西小天池。同时靠坝体东侧发育排泄通道,呈现多处溢水点,控制了飞龙涧左岸下降泉季节性发育,同河谷冲刷作用一起影响并导致下游左岸冰碛物中发育4处滑坡体。电法剖面揭示出与坝体轴向近平行的2条隐伏断层,其中堆积坝高堤处气象台所在山丘上游一侧发育一条近东西走向并倾向上游的断层F1,构成地下水阻隔带而使天池堆积坝上游潜水水位呈现一定雍高,同坝体下伏基岩和弱透水冰碛物联合组成的...  相似文献   

Trace Metals Accumulation and Antioxidants Profiling in Two Maize Genotypes Against Sewage and Textile Wastewater Treatment     

Zoya Zafar  Javaid Akhtar  Muhammad Amjad  Muhammad Anwar‐ul‐Haq  Zulfiqar Ahmed Saqib 《洁净——土壤、空气、水》2019,47(7)

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Modeling radon time series on the North Anatolian Fault Zone,Turkiye: Fourier transforms and Monte Carlo simulations     

Muhammad  Ahmad  Külahcı  Fatih  Akram  Pishtiwan 《Natural Hazards》2020,104(1):979-996

Natural Hazards - Time series studies depend mostly on stochastic models for radon seasonal, annual or temporal variability explanations. Others solve radon transport steady state equation...  相似文献   

Calibration of local magnitude scale for Hindukush continental subduction zone          下载免费PDF全文

Muhammad N.Mushtaq  Muhammd Tahir  Muhammd T.Iqbal  Muhammd A.Shah  Saleem Iqbal  Talat Iqbal 《地震科学（英文版）》2021,34(2):114-122

Hindukush is an active subduction zone where at least one earthquake occurs on daily basis. For seismic hazard studies, it is important to develop a local magnitude scale using the data of local seismic network. We have computed local magnitude scale for Hindukush earthquakes using data from local network belonging to Center for Earthquake Studies (CES) for a period of three years, i.e. 2015–2017. A total of 26,365 seismic records pertaining to 2,683 earthquakes with magnitude 2.0 and greater, was used with hypocentral distance less than 600 km. Magnitude scale developed by using this data comes to be M_L = logA + 0.929logr + 0.00298r – 1.84. The magnitude determined through formulated relation was compared with that of standard relation for Southern California and relation developed by the same authors for local network for Northern Punjab. It was observed that Hindukush region has high attenuation as compared to that of Southern California and Northern Punjab which implies that Hindukush is tectonically more disturbed as compared to the said regions, hence, seismically more active as well. We have calculated station correction factors for our network. Station correction factors do not show any pattern which probably owes to the geological and tectonic complexity of this structure. Standard deviation and variance of magnitude residuals for CES network determined using Hutton and Boore scale and scale developed in this study were compared, it showed that a variance reduction of 44.1% was achieved. Average of magnitude residuals for different distance ranges was almost zero which showed that our magnitude scale was stable for all distances up to 600 km. Newly developed magnitude scale will help in homogenization of earthquake catalog. It has been observed that b-value of CES catalog decreases when magnitude is calculated by using newly developed magnitude scale.  相似文献   

Geochemical anomaly separation by multifractal modeling in Kahang (Gor Gor) porphyry system,Central Iran     

Peyman Afzal  Ahmad Khakzad  Parviz Moarefvand  N. Rashidnejad Omran  Bijan Esfandiari  Younes Fadakar Alghalandis 《Journal of Geochemical Exploration》2010,104(1-2):34-46

Geochemical anomaly separation using the concentration–area (C–A) method at Kahang (Gor Gor) porphyry system in Central Iran is studied in this work. Lithogeochemical data sets were used in this geochemical survey which was conducted for the exploration for Cu mineralization in dioritic and andesitic units at Kahang Cu–Mo porphyry system. Similar surveys were also carried out for Mo and Au exploration in these rock units. The obtained results have been interpreted using rather extensive set of information available for each mineralized area, consists of detailed geological mapping, structural interpretation and alteration data. Anomalous threshold values for the mineralized zone were computed and compared with the statistical methods based on the data obtained from chemical analysis of samples for the lithological units. Several anomalies at a local scale were identified for Cu (224 ppm), Mo (63 ppm), and Au (31 ppb), and the obtained results suggests existence of local Cu anomalies whose magnitude generally is above 1000 ppm. The correlation between these threshold values and ore grades is clearly interpreted in this investigation. Also, the log–log plots show existence of three stages of Cu enrichment, and two enrichment stages for Mo and Au. The third and most important mineralization event is responsible for the presence of Cu at grades above 1995 ppm. The identified anomalies in Kahang porphyry system, and distribution of the rock types, are mainly monzodiorite and andesitic units, do have special correlation with Cu and monzonitic and dioritic rocks, especially monzodioritic type, which is of considerable emphasis. The threshold values obtained for each element are always lower than their mean content in the rocks. The study shows threshold values for Cu is clearly above the mean rock content, being a consequence of the occurrence of anomalous accumulations of phyllic, argillic and propyllitic alterations within the monzonitic and dioritic rocks especially in monzodioritic type. The obtained results were compared with fault distribution patterns which reveal a positive direct correlation between mineralization in anomalous areas and the faults present in the mineralized system.  相似文献   

Revisiting major earthquakes in Pakistan          下载免费PDF全文

Irfan Mahmood  Aqeel Ahmed Kidwai  Shahid Nadeem Qureshi  Muhammad Farooq Iqbal  Luqman Atique 《Geology Today》2015,31(1):33-38

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