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Multiscale modelling of granular materials in boundary value problems accounting for mesoscale mechanisms
مدلسازی چند مقیاسی مواد دانهای در مسائل ارزش مرزی برای مکانیزمهای مقیاس متوسط-2021 The proper solution of geotechnical boundary value problems requires robust constitutive models that can
describe the mechanical behavior of geomaterials under various loading conditions, while also accounting as
closely as possible for the different material scales of interest. This is even more relevant to granular media where
the complexity of the mechanical behaviour is not limited to the nature of the contact law between grains, and
instead originates from the multiplicity of contacts oriented along all the directions of the physical space to form
distinctive mesostructures. This paper revisits the so-called H-model, which belongs to the broad family of
micromechanical approaches whereby an intermediate scale (mesoscale) is explicitly introduced into the
formulation. One great advantage of the model is that it can be extended by accounting for further multi-physical
couplings, as for example the presence of capillary bridges between grains. This versatile model was imple-
mented within an explicit finite difference based computational software (FLAC), and the present work dem-
onstrates its ability to analyze engineering problems with a microstructural viewpoint, while also providing new
insights in microstructural mechanisms of failure difficult to capture with standard phenomenological models. keywords: مواد گرانول | یکسان سازی | رویکرد چند منظوره | نظریه چندگانه | ریز ساختار | مقیاس Mesoscopic | مدل سازی سازنده | مدل H | مشکلات ارزش مرزی | Granular material | Homogenization | Multiscale approach | Multislip theory | Microstructure | Mesoscopic scale | Constitutive modeling | H-model | Boundary value problems |
مقاله انگلیسی |
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Application of spectral features for separating homochromatic foreign matter from mixed congee
کاربرد ویژگیهای طیفی برای جداسازی مواد خارجی هم رنگ از مخروط مخروطی-2021 Foreign matter (FM) in mixed congee not only reduces the quality of the congee but may also harm consumers. However, the common computer vision methods with poor recognition ability for the homochromatic FM. This study used hyperspectral reflectance images with the pattern recognition model to detect homochromatic FM on the mixed congee surface. First, spectral features corresponding to homochromatic FM and background were extracted from hyperspectral images. Then, based on the optimal spectral preprocessing method, LDA, K-nearest neighbor, backpropagation artificial neural network, and support vector machine (SVM) were used to classify the spectral features. The results revealed that the SVM model input with raw spectra principal components exhibited optimal identification rates of 99.17%. Finally, most of the pixels for homochromatic FM were classified correctly by using the SVM model. To summarized, hyperspectral images combined with pattern recognition are an effective method for recognizing homochromatic FM in mixed congee. Keyword: Mixed congee | Homochromatic foreign matter | Hyperspectral imaging technology | Pattern recognition | Chemometrics |
مقاله انگلیسی |
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Identification and differentiation of commercial and military explosives via high performance liquid chromatography – high resolution mass spectrometry (HPLC-HRMS), X-ray diffractometry (XRD) and X-ray fluorescence spectroscopy (XRF): Towards a forensic substance database on explosives
شناسایی و تمایز مواد منفجره تجاری و نظامی از طریق کروماتوگرافی مایع با کارایی بالا - طیف سنجی جرمی با وضوح بالا (HPLC-HRMS) ، پراش سنجی اشعه ایکس (XRD) و طیف سنجی فلورسانس اشعه ایکس (XRF): به سمت پایگاه داده مواد پزشکی قانونی در مورد مواد منفجره-2020 The identification of confiscated commercial and military explosives is a crucial step not only in the
uncovering of distribution pathways, but it also aids investigating officers in criminal casework. Even
though commercial and military explosives mainly rely on a small number of high-energy compounds, a
great variety of additives and synthesis by-products can be found that can differ depending on the brand,
manufacturer and application. This makes the identification of commercial and military explosives based
on their overall composition a promising approach that can be used to establish a pan-European Forensic
Substance Database on Explosives.
In this work, three analytical techniques were employed to analyze 36 samples of commercial and
military explosives from Germany and Switzerland. An HPLC-HRMS method was developed, using 27
analytes of interest that encompass high-energy compounds, synthesis by-products and additives. HPLCHRMS
and XRD were used to gather and confirm molecular information on each sample and XRF analyses
were carried out to gain insight on the elemental composition. Combining the results from all three
techniques, 41 different additives could be identified as being diagnostic analytes and all samples showed
a unique analytical fingerprint, which allows for a differentiation of the samples. Therefore, this work
presents a set of methods that can be used as a foundation for the creation and population of a database
on explosives that enables the assigning of specific formulations to certain brands, manufacturers and
countries of origin. Keywords: HPLC-HRMS | Powder XRD | XRF | Explosives | Commercial explosives | Military explosives |
مقاله انگلیسی |
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An evolution law for fabric anisotropy and its application in micromechanical modelling of granular materials
قانون تکامل برای ناهمسانگردی پارچه و کاربرد آن در مدل سازی میکرومکانیکی مواد دانه ای-2020 Micromechanical studies of granular materials have demonstrated the importance of their microstruc- ture to their behaviour. This microstructure is often characterized by fabric tensors. Experimental and computational studies have shown that the fabric can change significantly during deformation. Therefore, the evolution of fabric is important to constitutive modelling. Current fabric evolution laws for granular materials have generally been developed for continuum-mechanical models, and use a loading index mul- tiplier associated with a yield surface. Such evolution laws can not be employed with micromechanical models that do not involve an explicit macro-scale yield surface. This study develops an evolution law for fabric anisotropy, based on observations from experiments and Discrete Element Method simulations from literature. The proposed evolution law considers the effects of inherent anisotropy, void ratio, stress ratio, loading direction and intermediate principal stress ratio. In the critical state, the value of the fabric anisotropy depends only on the Lode angle. The predicted evolution of fabric anisotropy is in good agreement with results of Discrete Element Method simulations, showing both hardening and softening behaviour and describing the influence of the initial void ratio. The proposed evolution law can be embedded into micromechanics-based constitutive relations as well as conventional continuum-mechanical models. As an example, a well-established micromechanical model (in which the fabric is considered as constant) has been extended by accounting for the variations in fabric, in combination with the proposed fabric evolution law. The performance of this enhanced mi- cromechanical model has been demonstrated by a comparison between the predicted behaviour and ex- perimental results from literature for Toyoura sand under various loading conditions. Keywords: Granular material | Fabric | Micromechanics | Constitutive modelling |
مقاله انگلیسی |
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A full-disk image standardization of the chromosphere observation at Huairou Solar Observing Station
استاندارد سازی دیسک کامل تصویر از مشاهده کروموسفر در ایستگاه مشاهده خورشیدی Huairou-2020 Observations of local features in the solar chromosphere began in 1992 at Huairou Solar Observing Station, while the full-disk chromosphere
observations were carried out since 2000. In order to facilitate researchers to use full-disk chromosphere observation, algorithms
have been developed to standardize the full-disk images. The algorithms include the determination of the center of the image
and size standardization, geometric correction and intensity normalization. The solar limb of each image is determined from a histogram
analysis of its intensity distribution. The center and radius are then calculated and the image is corrected for geometric distortions.
Images are re-scaled to have a fixed radius of 500 pixels and centered within the 1024 1024 frame. Finally, large-scale variations in
intensity, such as limb-darkening, are removed using a median filter. This paper provides a detailed description of these algorithms,
and a summary of the properties of these chromospheric full-disk observations to be used for further scientific investigations. Keywords: Chromosphere | Data standardization | Physical parameters | Big data |
مقاله انگلیسی |
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Identification of the absorbed components and metabolites ofXiao-Ai-Jie-Du decoction and their distribution in rats using ultrahigh-performance liquid chromatography/quadrupole time-of-flightmass spectrometry
شناسایی اجزای جذب شده و متابولیتهای جوشانده Xiao-Ai-Jie-Du و توزیع آنها در موشهای صحرایی با استفاده از کروماتوگرافی مایع با عملکرد فوق العاده / طیف سنجی ماد پرواز چهارگانه-2020 Xiao-Ai-Jie-Du decoction (XAJDD), a traditional Chinese medicine formula, has long been used forthe treatment of hepatocarcinoma, gastric cancer and colorectal cancer. It is composed of six herbalmedicines, including Scutellariae Barbatae Herba, Pseudostellariae Radix, Ophiopogonis Radix, Cremastrae Pseudobulbus, Curcumae Rhizoma and Akebiae Fructus. Despite the in-depth study on its pharmacologicaleffects on cancer prevention and treatment, the comprehensive analysis of the chemical components andthe absorbed bioactive constituents are not well studied. Thus, an ultra-high-performance liquid chro-matography/quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) method was establishedto detect and identify the chemical constituents in XAJDD. The absorbed components and metabolitesafter oral administration of XAJDD in rats were also studied. In total, 102 components were identified ortentatively characterized in XAJDD, including 30 flavonoids, 19 triterpenoids, 12 organic acids, 9 steroidalsaponins, 9 cyclic peptides, 7 phenanthrenes, 5 amino acids, 3 alkaloids and 8 other compounds. Afteranalysing the metabolites in rat plasma and urine after oral administration of XAJDD, a total of 70 com-pounds were identified, including 15 primary components and 55 metabolites, and metabolic pathways,including hydrogenation, hydroxylation, methylation, sulfonation, and glucuronidation were evaluated.Among these, methylation and glucuronidation were the main metabolic pathways. In conclusion, thedeveloped UHPLC-Q-TOF-MS method with high sensitivity and resolution is suitable for identifying andcharacterizing the chemical constituents of XAJDD in vitro and characterizing the primary componentsand their metabolites in vivo; moreover, the results will provide essential data for further studying therelationship between the chemical components and pharmacological activity of XAJDD. Keywords: Absorbed components | Metabolites | Identification | UHPLC-Q-TOF-MS | Xiao-Ai-Jie-Du formula |
مقاله انگلیسی |
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Mechanism of anti-inflammatory effects of volatile compounds ofAi pian based on network pharmacology, in vivo animal experiments,and GC–MS
مکانیسم اثرات ضد التهابی ترکیبات فرار بر اساس داروسازی شبکه ، آزمایشات داخل بدن حیوانات و GC-MS-2020 Ai pian (AP) is a well-known Miao national herb with resuscitative effects. However, pharmacologicaland clinical applications of AP are limited because its precise molecular mechanism remains unclear.This study was conducted to evaluate the anti-inflammatory activities of the volatile compounds of APin in vivo animal models and determine the molecular mechanism underlying the anti-inflammatoryeffects based on network pharmacology and molecular docking. We performed gas chromatography-mass spectrometric analysis of volatile compounds with chemometric methods, including hierarchicalclustering analysis and principal component analysis, to identify AP from different origins. Mouse modelsof xylene-induced ear edema were used to examine the in vivo anti-inflammatory activities of AP withcotton ball-granulation test. The mechanism of AP was determined by network pharmacology analysisand molecular docking. Significant differences in chemical constituents and percentage contents wereobserved among different habitats. We found that AP exerted potent anti-inflammatory effect, and thatmultiple targets and pathways were involved in this effect. These results provided a foundation for furthercomprehensive development and application of AP from Miao national herb. Keywords:Ai pian | Gas chromatography-mass spectrometry | Volatile compound | Anti-inflammatory | Network pharmacology | Molecular docking |
مقاله انگلیسی |
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Analysis of samples of explosives excavated from the Baltic Sea floor
تجزیه و تحلیل نمونه های مواد منفجره کشف شده از کف دریای بالتیک-2020 After World War II, conventional and chemical ammunition containing mainly secondary and primary
explosives was dumped in the sea. Explosives have medium toxicity to aquatic organisms, earthworms
and indigenous soil microorganisms. Therefore, environmental monitoring is required, especially for
dumped munitions. The main aspect of this work was to analyse the samples of lumps and sediments
taken from the Baltic seabed. These samples were potentially explosives. The main goal of the study
was to identify the type and composition of studied materials. In order to determine the chemical
composition of samples of explosives, we used as follows: GC–MS/MS, LC-HRMS and NMR.
Additionally, to determine the energetic properties we performed microcalorimetric-thermogravimetric
analysis. Based on the obtained results, the composition of this explosive was TNT (41%), RDX (53%),
aluminium powder (5%), and degradation products (below 1%). The resulting composition indicates that
the analysed material can be classified in the ‘‘torpex” family, widely used during World War II. Regarding
the results of the microcalorimetric analysis, we can conclude that excavated fragments of explosives are
in very good condition and they still can detonate after being initiated. Therefore, there is a threat that
they could be used for criminal or terrorist purposes. Keywords: Environmental samples | Explosives and their degradation products | Chromatographic analysis | Mass spectrometry | Nuclear magnetic resonance spectroscopy |
مقاله انگلیسی |
9 |
A micromorphic crystal plasticity model with the gradient-enhanced incremental hardening law
مدل انعطاف پذیری بلور میکرومورفیک با قانون سخت شدن افزایشی شیب-2020 A model of crystal plasticity is developed in which the effects of plastic flow non-uniformity are
described through the full dislocation density tensor. The micromorphic approach is used in
which the dislocation density tensor is represented by the curl of an independent constitutive
variable called microdeformation. The microdeformation tensor is enforced by an energetic
penalty term to be close to the actual plastic distortion tensor. The curl of microdeformation
tensor enters the constitutive model in two independent but complementary ways. First, it is an
argument of the free energy density function, which describes the kinematic-type hardening in
cyclic non-uniform deformation. Second, its rate influences the rates of critical resolved shear
stresses, which corresponds to additional isotropic hardening caused by incompatibility of the
plastic flow rate. The latter effect, missing in the standard slip-system hardening rule, is described
in a simple manner that does not require any extra parameter in comparison to the non-gradient
theory. In the proposed model there are two independent internal length scales whose interplay is
examined by means of 1D and 2D numerical examples of plastic shearing of a single crystal. Keywords: Gradient theory | Crystal plasticity | Dissipation | Length scale | Cyclic deformation | Numerical regularization |
مقاله انگلیسی |
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مطالعه سطح برخی فلزات سنگین در آب دریاچه حبّانیه در استان الانبار عراق
سال انتشار: 2019 - تعداد صفحات فایل pdf انگلیسی: 7 - تعداد صفحات فایل doc فارسی: 15 در این کار تحقیقی، مطالعه و تحلیل وجود برخی فلزات سنگین مثل سرب، آهن، کروم، کادمیم و نیکل در آب رودخانه حبّانیه جهت بررسی آلودگی مورد بررسی قرار گرفته است. 10 مکان در ناحیه مطالعاتی درطی 12 آوریل تا 12 آگوست سال 2017 انتخاب شد. غلظت فلزات سنگین توسط طیف نورسنج جذب اتمی تحلیل شد. اندازه گیری ها نشان داد که کاهش سطح غلظت در آب به صورت سرب > آهن > کروم > کادمیم > نیکل مشاهده شد. پی برده شد که غلظت فلزات سنگین در آب رودخانه حبّانیه از خط مقادیر مبنا توصیه شده برای زندگی آبزیان بالاتر است. شاخص آلودگی شدید محاسبه شد؛ نتیجه به دست آمده نشان داد که آب با برخی فلزات سنگین آلوده می شود. برطبق نتایج شاخص فلزی، آب به صورت جدی توسط عوامل آلاینده و مصرف های معدنی و غیرایمن برای آبیاری، نوشیدن و زندگی آبزیان تهدید می شود. |
مقاله ترجمه شده |